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Sample records for narrow-band tunable filter

  1. Narrow-Band WGM Optical Filters With Tunable FSRs

    NASA Technical Reports Server (NTRS)

    Mohageg, Makan; Matsko, Andrey; Savchenkov, Anatoliy; Maleki, Lute; Iltchenko, Vladimir; Strekalov, Dmitry

    2007-01-01

    Optical resonators of the whispering-gallery-mode (WGM) type featuring DC-tunable free spectral ranges (FSRs) have been demonstrated. By making the FSR tunable, one makes it possible to adjust, during operation, the frequency of a microwave signal generated by an optoelectronic oscillator in which an WGM optical resonator is utilized as a narrow-band filter.

  2. Whispering-Gallery-Mode Tunable Narrow-Band-Pass Filter

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy; Iltchenko, Vladimir; Matsko, Andrey; Maleki, Lute

    2004-01-01

    An experimental tunable, narrow-band-pass electro-optical filter is based on a whispering-gallery resonator. This device is a prototype of tunable filters needed for the further development of reconfigurable networking wavelength-division multiplexers and communication systems that utilize radio-frequency (more specifically, microwave) subcarrier signals on optical carrier signals. The characteristics of whispering-gallery resonators that make them attractive for such applications include high tuning speed, compactness, wide tuning range, low power consumption, and compatibility with single-mode optical fibers. In addition, relative to Fabry-Perot resonators, these devices offer advantages of greater robustness and lower cost. As described in several prior NASA Tech Briefs articles, a whispering-gallery resonator is a spheroidal, disk-like, or toroidal body made of a highly transparent material. It is so named because it is designed to exploit whispering-gallery electromagnetic modes, which are waveguide modes that propagate circumferentially and are concentrated in a narrow toroidal region centered on the equatorial plane and located near the outermost edge. The experimental whispering-gallery tunable filter (see figure) is made from a disk of Z-cut LiNbO3 of 4.8-mm diameter and 0.17-mm thickness. The perimeter of the disk is rounded to a radius of curvature of 100 m. Metal coats on the flat faces of the disk serve as electrodes for exploiting the electro-optical effect in LiNbO3 for tuning. There is no metal coat on the rounded perimeter region, where the whispering-gallery modes propagate. Light is coupled from an input optical fiber into the whispering-gallery modes by means of a diamond prism. Another diamond prism is used to couple light from the whispering-gallery modes to an output optical fiber. This device is designed and operated to exploit transverse magnetic (TM) whispering- gallery modes, rather than transverse electric (TE) modes because the

  3. First Light of the Near-Infrared Narrow-Band Tunable Birefringent Filter at Big Bear Solar Observatory

    NASA Astrophysics Data System (ADS)

    Cao, Wenda; Hartkorn, Klaus; Ma, Jun; Xu, Yan; Spirock, Tom; Wang, Haimin; Goode, Philip R.

    2006-10-01

    We discuss a near-infrared (NIR) narrow-band tunable birefringent filter system newly developed by the Big Bear Solar Observatory (BBSO). This is one of the first narrow-bandpass NIR filter systems working at 1.56 μm which is used for the observation of the deepest solar photosphere. Four stages of calcite were used to obtain a bandpass of 2.5 Å along with a free spectral range (FSR) of 40 Å. Some unique techniques were implemented in the design, including liquid crystal variable retarders (LCVRs) to tune the bandpass in a range of ±100 Å, a wide field configuration to provide up to 2° incident angle, and oil-free structure to make it more compact and handy. After performing calibration and characteristic evaluation at the Evans Facility of the National Solar Observatory at Sacramento Peak (NSO/SP), a series of high-resolution filtergrams and imaging polarimetry observations were carried out with the Dunn Solar Telescope of NSO/SP and the 65-cm telescope of BBSO, in conjunction with the high-order adaptive optics system and the Fabry-Pérot Interferometer (FPI). In this paper, we describe the optical design and discuss the calibration method. Preliminary observations show that it is capable of serving as either a stand-alone narrow-band filter for NIR filtergram observations or an order-sorting filter of a FPI applied to NIR two-dimensional imaging spectro-polarimetry.

  4. First Light for the Near-Infrared Narrow-Band Tunable Birefringent Filter of the Big Bear Solar Observatory

    NASA Astrophysics Data System (ADS)

    Cao, W.; Hartkorn, K.; Ma, J.; Wang, J.; Xu, Y.; Spirock, T.; Denker, C.; Wang, H.

    2005-05-01

    A new near-infrared, narrow-band tunable birefringent filter has been developed by BBSO/NJIT. This filter, one of the first Lyot filters in the near-infrared, has a FWHM of about 2.5 ~Å at the design wavelength of 1.5648 μm and is used to observe the deepest levels of the photosphere. New techniques were employed in the design, including liquid crystal retarders to tune the center wavelength in range of ± 100 ~Å. After finishing the calibration and evaluation of the filter at the Evans Facility of the NSO at Sacramento Peak, high spatial resolution filtergrams and imaging spectroscopy observations were carried out at the Dunn Solar Telescope of NSO in December 2004 with the use of the high-order Adaptive Optics System. For some of these observations, the Lyot filter was combined with a Fabry-Perot Etalon to achieve a much higher spectral resolution. We discuss the calibration methods and present some preliminary observation results.

  5. Precisely tunable, narrow-band pulsed dye laser

    SciTech Connect

    Bhatia, P.S.; Keto, J.W.

    1996-07-01

    A narrow-band, precisely tunable dye laser pumped by an injection-seeded YAG laser is described. The laser achieves an output of 100 mJ/pulse and 40{percent} efficiency when one uses Rhodamine 6G dyes. The output pulse is Gaussian both in time and spatial profile. The laser oscillator employs an intracavity {acute e}talon that is repetitively pressure scanned over one free spectral range while the grating successively steps to consecutive {acute e}talon modes. We pressure scanned the {acute e}talon under computer control using a bellows. Methods are described for calibrating the tuning elements for absolute precision. We demonstrated that the laser has an absolute precision of {plus_minus}0.4 pm over a 1.0-nm scan. This accuracy is achievable over the wavelength range of a dye. {copyright} {ital 1996 Optical Society of America.}

  6. PAU, a fully depleted mosaic imager with narrow band filters

    NASA Astrophysics Data System (ADS)

    Bauer, A.; Casas, R.; Castander, F. J.; Serrano, S.

    2014-03-01

    The PAU Survey studies the existence and properties of dark energy from the observations of redshift space distortions and weak lensing magnification from galaxy cross-correlations as main cosmological probes. The PAU Team is building an instrument, PAUCam, equipped with fully depleted CCD detectors, designed to be mounted at the prime focus of the 4.2 m diameter William Herschel Telescope (WHT) in La Palma. Simulations indicate that PAUCam at the WHT will be able to image about 2 square degrees per night in 40 narrow-band filters plus six wide-band filters to an AB magnitude depth of i ~ 22.5, providing low-resolution (R ~ 50) photometric spectra for around 30,000 galaxies, 5,000 stars and 1,000 quasars per square degree. Accurate photometric calibration of the PAU data is vital to achieve the survey science goals. This calibration is challenging due to the large and unusual filter set. We outline the data management pipelines being developed for the survey, both for nightly data reduction and co-addition of multiple epochs, with emphasis on the photometric calibration strategies. We also describe the main tests and results in the characterization of our Hamamatsu fully depleted detectors.

  7. Narrow-band tunable alexandrite laser with passive Q switching

    SciTech Connect

    Tyryshkin, I S; Ivanov, N A; Khulugurov, V M

    1998-06-30

    An alexandrite laser with a self-injection of narrow-band radiation into its cavity was developed. A Fabry - Perot interferometer and a diffraction grating were used as dispersive components in an additional cavity. The cavity was switched by an LiF crystal with F{sub 3}{sup -} colour centres. The laser generated a single pulse of {approx} 180 ns duration and of 1.5 mJ energy, and with a spectrum 5 x 10{sup -3} cm{sup -1} wide. The laser emitted in the spectral range 720 - 780 nm. (lasers, active media)

  8. Narrow band pass filter using birefringence film and quarter-wave film

    NASA Astrophysics Data System (ADS)

    Lee, Dong-kun; Song, Jang-Kun

    2016-03-01

    While a pixel in a color image has three colorimetric information of RGB, that in a spectral image contains full spectral information, several tens times more information compared to the color image. Hence, the spectral image is widely applicable in biology, material science, and environmental science. Although several methods for spectral image acquisition have been suggested to date, those methods are expensive, bulky, or slow in actual device. In this work, we designed a novel type of tunable narrow band-pass filter using rotatable polarizer, quarter-wave plate, and birefringence films. Different from the conventional Lyot-Ohman type filter, we do not use a liquid crystal layer. The selection of wavelength is made by rotating the polarizer in our filter set, and adopted a piezoelectric rotational actuator for that. We simulated to find the optimal conditions of the filter set, and finally, fabricated a filter module. The minimum band width was 5 nm, which is suitable for usual spectral imaging and can be reduced further if necessary, and the wavelength of light passing through the filter set was continuously selectable. After setting the filter in a microscope, we obtained a spectral image set for a bio sample that contained full spectrum information in each pixel. Using image processing, we could demonstrate to read out the spectral information for any selected position.

  9. Optimum filters for narrow-band frequency modulation.

    NASA Technical Reports Server (NTRS)

    Shelton, R. D.

    1972-01-01

    The results of a computer search for the optimum type of bandpass filter for low-index angle-modulated signals are reported. The bandpass filters are discussed in terms of their low-pass prototypes. Only filter functions with constant numerators are considered. The pole locations for the optimum filters of several cases are shown in a table. The results are fairly independent of modulation index and bandwidth.

  10. Enhanced tunable narrow-band THz emission from laser-modulated electron beams

    SciTech Connect

    Xiang, D.; Stupakov, G.; /SLAC

    2009-06-19

    We propose and analyze a scheme to generate enhanced narrow-band terahertz (THz) radiation through down-conversion of the frequency of optical lasers using laser-modulated electron beams. In the scheme the electron beam is first energy modulated by two lasers with wave numbers k{sub 1} and k2, respectively. After passing through a dispersion section, the energy modulation is converted to density modulation. Due to the nonlinear conversion process, the beam will have density modulation at wave number k = nk{sub 1} + mk{sub 2}, where n and m are positive or negative integers. By properly choosing the parameters for the lasers and dispersion section, one can generate density modulation at THz frequency in the beam using optical lasers. This density-modulated beam can be used to generate powerful narrow-band THz radiation. Since the THz radiation is in tight synchronization with the lasers, it should provide a high temporal resolution for the optical-pump THz-probe experiments. The central frequency of the THz radiation can be easily tuned by varying the wavelength of the two lasers and the energy chirp of the electron beam. The proposed scheme is in principle able to generate intense narrow-band THz radiation covering the whole THz range and offers a promising way towards the tunable intense narrow-band THz sources.

  11. Multi-tap complex-coefficient incoherent microwave photonic filters based on optical single-sideband modulation and narrow band optical filtering.

    PubMed

    Sagues, Mikel; García Olcina, Raimundo; Loayssa, Alayn; Sales, Salvador; Capmany, José

    2008-01-01

    We propose a novel scheme to implement tunable multi-tap complex coefficient filters based on optical single sideband modulation and narrow band optical filtering. A four tap filter is experimentally demonstrated to highlight the enhanced tuning performance provided by complex coefficients. Optical processing is performed by the use of a cascade of four phase-shifted fiber Bragg gratings specifically fabricated for this purpose. PMID:18521161

  12. Flexible metamaterial narrow-band-pass filter based on magnetic resonance coupling between ultra-thin bilayer frequency selective surfaces

    NASA Astrophysics Data System (ADS)

    Bai, Zhengyuan; Zhang, Qing; Ju, Yongfeng; Tao, Guiju; Jiang, Xiongwei; Kang, Ning; Liu, Chengpu; Zhang, Long

    2016-02-01

    A novel flexible metamaterial narrow-band-pass filter is designed and proved to be reliable by both numerical simulations and experimental measurements. The unit cell of the designed structure consists of circle ring resonators on top of a thin dielectric layer backed by a metallic mesh. The investigations on the distribution of the surface current and magnetic field as well as the analysis of the equivalent circuit model reveal that the magnetic resonance response between layers induced by the reverse surface current contributes to the high quality factor band-pass property. Importantly, it is a flexible design with a tunable resonance frequency by just changing the radius of the circle rings and can also be easily extended to have the multi-band-pass property. Moreover, this simplified structure with low duty cycle and ultra-thin thickness is also a symmetric design which is insensitive to the polarization and incident angles. Therefore, such a metamaterial narrow-band-pass filter is of great importance in the practical applications such as filtering and radar stealth, and especially for the conformal structure applications in the infrared and optical window area.

  13. Measuring large-scale structure with quasars in narrow-band filter surveys

    NASA Astrophysics Data System (ADS)

    Abramo, L. Raul; Strauss, Michael A.; Lima, Marcos; Hernández-Monteagudo, Carlos; Lazkoz, Ruth; Moles, Mariano; de Oliveira, Claudia Mendes; Sendra, Irene; Sodré, Laerte; Storchi-Bergmann, Thaisa

    2012-07-01

    We show that a large-area imaging survey using narrow-band filters could detect quasars in sufficiently high number densities, and with more than sufficient accuracy in their photometric redshifts, to turn them into suitable tracers of large-scale structure. If a narrow-band optical survey can detect objects as faint as i= 23, it could reach volumetric number densities as high as 10-4 h3 Mpc-3 (comoving) at z˜ 1.5. Such a catalogue would lead to precision measurements of the power spectrum up to z˜ 3-4. We also show that it is possible to employ quasars to measure baryon acoustic oscillations at high redshifts, where the uncertainties from redshift distortions and non-linearities are much smaller than at z≲ 1. As a concrete example we study the future impact of the Javalambre Physics of the Accelerating Universe Astrophysical Survey (J-PAS), which is a narrow-band imaging survey in the optical over 1/5 of the unobscured sky with 42 filters of ˜100-Å full width at half-maximum. We show that J-PAS will be able to take advantage of the broad emission lines of quasars to deliver excellent photometric redshifts, σz≃ 0.002 (1 +z), for millions of objects.

  14. A super narrow band filter based on silicon 2D photonic crystal resonator and reflectors

    NASA Astrophysics Data System (ADS)

    Wang, Yuanyuan; Chen, Deyuan; Zhang, Gang; Wang, Juebin; Tao, Shangbin

    2016-03-01

    In this paper, a novel structure of super narrow band filter based on two-dimensional square lattice photonic crystals of silicon rods in air for 1.5 um communication is proposed and studied. COMSOL Multiphysics4.3b software is used to simulate the optical behavior of the filter. The filter consists of one point-defect-based resonator and two line-defect-based reflectors. The resonance frequency, transmission coefficient and quality factor are investigated by varying the parameters of the structure. In design, a silicon rod is removed to form the resonator; for the rows of rods above and below the resonator, a part of the rods are removed to form the reflectors. By optimizing the parameters of the filter, the quality factor and transmission coefficient of the filter at the resonance frequency of 2e14 Hz can reach 1330 and 0.953, respectively. The super narrow band filter can be integrated into optical circuit for its micron size. Also, it can be used for wavelength selection and noise filtering of optical amplifier in future communication application.

  15. Narrow band wavelength selective filter using grating assisted single ring resonator

    SciTech Connect

    Prabhathan, P. Murukeshan, V. M.

    2014-09-15

    This paper illustrates a filter configuration which uses a single ring resonator of larger radius connected to a grating resonator at its drop port to achieve single wavelength selectivity and switching property with spectral features suitable for on-chip wavelength selection applications. The proposed configuration is expected to find applications in silicon photonics devices such as, on-chip external cavity lasers and multi analytic label-free biosensors. The grating resonator has been designed for a high Q-factor, high transmittivity, and minimum loss so that the wavelength selectivity of the device is improved. The proof-of-concept device has been demonstrated on a Silicon-on-Insulator (SOI) platform through electron beam lithography and Reactive Ion Etching (RIE) process. The transmission spectrum shows narrow band single wavelength selection and switching property with a high Free Spectral Range (FSR) ∼60 nm and side band rejection ratio >15 dB.

  16. A proposed interim improvement to the Tevatron beam position monitors with narrow band crystal filters

    SciTech Connect

    Cheng-Yang Tan

    2003-08-25

    Since the start of Run II, we have found that we are unable to reliably and accurately measure the beam position with the present BPM system during high energy physics (HEP). This problem can be traced back to the analogue frontend called the AM/PM module which has trouble handling coalesced beam, but works well with uncoalesced beam. In this paper, we propose a simple fix to the AM/PM module so that we can measure the beam position during HEP. The idea is to use narrow band crystal filters which ring when pinged by coalesced beam so that the AM/PM module is tricked into thinking that it is measuring uncoalesced beam.

  17. A blue optical filter for narrow-band imaging in endoscopic capsules

    NASA Astrophysics Data System (ADS)

    Silva, M. F.; Ghaderi, M.; Goncalves, L. M.; de Graaf, G.; Wolffenbuttel, R. F.; Correia, J. H.

    2014-05-01

    This paper presents the design, simulation, fabrication, and characterization of a thin-film Fabry-Perot resonator composed of titanium dioxide (TiO2) and silicon dioxide (SiO2) thin-films. The optical filter is developed to be integrated with a light emitting diode (LED) for enabling narrow-band imaging (NBI) in endoscopy. The NBI is a high resolution imaging technique that uses spectrally centered blue light (415 nm) and green light (540 nm) to illuminate the target tissue. The light at 415 nm enhances the imaging of superficial veins due to their hemoglobin absorption, while the light at 540 nm penetrates deeper into the mucosa, thus enhances the sub-epithelial vessels imaging. Typically the endoscopes and endoscopic capsules use white light for acquiring images of the gastrointestinal (GI) tract. However, implementing the NBI technique in endoscopic capsules enhances their capabilities for the clinical applications. A commercially available blue LED with a maximum peak intensity at 404 nm and Full Width Half Maximum (FWHM) of 20 nm is integrated with a narrow band blue filter as the NBI light source. The thin film simulations show a maximum spectral transmittance of 36 %, that is centered at 415 nm with FWHM of 13 nm for combined the blue LED and a Fabry Perot resonator system. A custom made deposition scheme was developed for the fabrication of the blue optical filter by RF sputtering. RF powered reactive sputtering at 200 W with the gas flows of argon and oxygen that are controlled for a 5:1 ratio gives the optimum optical conditions for TiO2 thin films. For SiO2 thin films, a non-reactive RF sputtering at 150 W with argon gas flow at 15 sccm results in the best optical performance. The TiO2 and SiO2 thin films were fully characterized by an ellipsometer in the wavelength range between 250 nm to 1600 nm. Finally, the optical performance of the blue optical filter is measured and presented.

  18. Observation of coherently enhanced tunable narrow-band terahertz transition radiation from a relativistic sub-picosecond electron bunch train

    SciTech Connect

    Piot, P.; Sun, Y. -E; Maxwell, T. J.; Ruan, J.; Lumpkin, A. H.; Rihaoui, M. M.; Thurman-Keup, R.

    2011-06-27

    We experimentally demonstrate the production of narrow-band (δf/f ~ =20% at f ~ = 0.5 THz) THz transition radiation with tunable frequency over [0.37, 0.86] THz. The radiation is produced as a train of sub-picosecond relativistic electron bunches transits at the vacuum-aluminum interface of an aluminum converter screen. In addition, we show a possible application of modulated beams to extend the dynamical range of a popular bunch length diagnostic technique based on the spectral analysis of coherent radiation.

  19. Narrow-band tunable terahertz emission from ferrimagnetic Mn3-xGa thin films

    NASA Astrophysics Data System (ADS)

    Awari, N.; Kovalev, S.; Fowley, C.; Rode, K.; Gallardo, R. A.; Lau, Y.-C.; Betto, D.; Thiyagarajah, N.; Green, B.; Yildirim, O.; Lindner, J.; Fassbender, J.; Coey, J. M. D.; Deac, A. M.; Gensch, M.

    2016-07-01

    Narrow-band terahertz emission from coherently excited spin precession in metallic ferrimagnetic Mn3-xGa Heusler alloy nanofilms has been observed. The efficiency of the emission, per nanometer film thickness, is comparable or higher than that of classical laser-driven terahertz sources based on optical rectification. The center frequency of the emission from the films can be tuned precisely via the film composition in the range of 0.20-0.35 THz, making this type of metallic film a candidate for efficient on-chip terahertz emitters. Terahertz emission spectroscopy is furthermore shown to be a sensitive probe of magnetic properties of ultra-thin films.

  20. Generation of Intense Narrow-Band Tunable Terahertz Radiation from Highly Bunched Electron Pulse Train

    NASA Astrophysics Data System (ADS)

    Li, Heting; Lu, Yalin; He, Zhigang; Jia, Qika; Wang, Lin

    2016-07-01

    We present the analysis and start-to-end simulation of an intense narrow-band terahertz (THz) source with a broad tuning range of radiation frequency, using a single-pass free electron laser (FEL) driven by a THz-pulse-train photoinjector. The fundamental radiation frequency, corresponding to the spacing between the electron microbunches, can be easily tuned by varying the spacing time between the laser micropulses. Since the prebunched electron beam is highly bunched at the first several harmonics, with the harmonic generation technique, the radiation frequency range can be further enlarged by several times. The start-to-end simulation results show that this FEL is capable of generating a few tens megawatts power, several tens micro-joules pulse energy, and a few percent bandwidth at the frequencies of 0.5-5 THz. In addition, several practical issues are considered.

  1. Tunable millisecond narrow-band Nd:GSGG laser around 1336.6 nm for 27Al+ optical clock

    NASA Astrophysics Data System (ADS)

    Wang, M.-Q.; Zhang, F.-F.; Li, J.-J.; Wang, Z.-M.; Zong, N.; Zhang, S.-J.; Yang, F.; Yuan, L.; Bo, Y.; Cui, D.-F.; Peng, Q.-J.; Xu, Z.-Y.

    2016-05-01

    We developed a narrow-band, Nd:GSGG ring laser tunable around 1336.6 nm with a tuning range more than 24 pm. The maximum output energy is 0.26 J per pulse with a pulse width of 900 μs and a pulse repetition rate of 10 Hz. The root-mean-square of wavelength stability in 1 h is 0.27 pm, and M2 factor is 1.06 at the output energy of 0.16 J per pulse. It can be a good candidate of the fundamental laser, of which the eighth-harmonic generation at 167.0787 nm can be used to induce the 27Al+ ion by the 1S0↔1P1 transition for laser cooling when it is used as the medium for optical clock.

  2. Investigation of stimulated Raman scattering effect in high-power fiber amplifiers seeded by narrow-band filtered superfluorescent source.

    PubMed

    Liu, Wei; Ma, Pengfei; Lv, Haibin; Xu, Jiangming; Zhou, Pu; Jiang, Zongfu

    2016-04-18

    In this paper the stimulated Raman scattering (SRS) effect in high-power fiber amplifiers seeded by the narrow-band filtered superfluorescent source (SFS) is firstly analyzed both theoretically and experimentally. Spectral models for the formation of the SFS and the spectral evolution in high-power fiber amplifiers seeded by filtered SFS are proposed. It is found that the SRS effect in high-power fiber amplifiers depends on the spectral width of the filtered SFS seed. The theoretical predictions are in qualitative agreements with the experimental results. PMID:27137305

  3. Development and applications of tunable, narrow band lasers and stimulated Raman scattering devices for atmospheric lidar

    NASA Technical Reports Server (NTRS)

    Wilkerson, Thomas D.

    1993-01-01

    The main thrust of the program was the study of stimulated Raman processes for application to atmospheric lidar measurements. This has involved the development of tunable lasers, the detailed study of stimulated Raman scattering, and the use of the Raman-shifted light for new measurements of molecular line strengths and line widths. The principal spectral region explored in this work was the visible and near-IR wavelengths between 500 nm and 1.5 microns. Recent alexandrite ring laser experiments are reported. The experiments involved diode injection-locking, Raman shifting, and frequency-doubling. The experiments succeeded in producing tunable light at 577 and 937 nm with line widths in the range 80-160 MHz.

  4. Narrow-band, tunable, semiconductor-laser-based source for deep-UV absorption spectroscopy.

    PubMed

    Kliner, D A; Koplow, J P; Goldberg, L

    1997-09-15

    Tunable, narrow-bandwidth (<200-MHz), ~215-nm radiation was produced by frequency quadrupling the ~860-nm output of a high-power, pulsed GaAlAs tapered amplifier seeded by an external-cavity diode laser. Pulsing the amplifier increased the 860 nm?215 nm conversion efficiency by 2 orders of magnitude with respect to cw operation. Detection of nitric oxide and sulfur dioxide by high-resolution absorption spectroscopy was demonstrated. PMID:18188256

  5. Development of a narrow-band, tunable, frequency-quadrupled diode laser for UV absorption spectroscopy.

    PubMed

    Koplow, J P; Kliner, D A; Goldberg, L

    1998-06-20

    A compact, lightweight, low-power-consumption source of tunable, narrow-bandwidth blue and UV radiation is described. In this source, a single-longitudinal-mode diode laser seeds a pulsed, GaAlAs tapered amplifier whose ~860-nm output is frequency quadrupled by two stages of single-pass frequency doubling. Performance of the laser system is characterized over a wide range of amplifier duty cycles (0.1-1.0), pulse durations (50 ns-1.0 mus), peak currents (

  6. Tunable narrow-band spectral peak imposed onto a soliton with an acoustic long-period grating

    NASA Astrophysics Data System (ADS)

    Bolger, Jeremy A.; Luan, Feng; Yeom, Dong-Il; Tsoy, Eduard; de Sterke, C. Martijn; Eggleton, Benjamin J.

    2008-01-01

    We demonstrate a method of local spectral enhancement of an ultrafast soliton pulse. We use an in-line acoustic long-period grating (LPG), a periodic structure modifying both the phase and the loss of the propagating light, and which is readily tuned by simple adjustment of an applied electrical signal. The soliton perturbed by this narrow-band filter evolves with nonlinear propagation into an intense localised spectral peak. Our setup consists of creation of a red-shifted optical soliton by propagation of pulses from a fibre laser in standard single-mode optical fibre, followed by imposition of a spectrally narrow LPG near to the soliton peak, and then continuing propagation. The wavelength and the peak value of the resulting local enhancement can be tuned by adjustment of the applied acoustic frequency and amplitude. The physics of the observed local spectral enhancement will be discussed in detail here.

  7. Optical Observations of the Nearby Galaxy IC342 with Narrow Band [SII] and H_alpha Filters. I

    NASA Astrophysics Data System (ADS)

    Vucetic, M. M.; Arbutina, B.; Urosevic, D.; Dobardzic, A.; Pavlovic, M. Z.; Pannuti, T. G.; Petrov, N.

    2013-12-01

    We present observations of a portion of the nearby spiral galaxy IC342 using narrow band [SII] and Hα filters. These observations were carried out in November 2011 with the 2m RCC telescope at Rozhen National Astronomical Observatory in Bulgaria. In this paper we report coordinates, diameters, Hα and [SII] fluxes for 203 HII regions detected in two fields of view in IC342 galaxy. The number of detected HII regions is 5 times higher than previously known in these two parts of the galaxy.

  8. Thermal control design of the Lightning Mapper Sensor narrow-band spectral filter

    NASA Technical Reports Server (NTRS)

    Flannery, Martin R.; Potter, John; Raab, Jeff R.; Manlief, Scott K.

    1992-01-01

    The performance of the Lightning Mapper Sensor is dependent on the temperature shifts of its narrowband spectral filter. To perform over a 10 degree FOV with an 0.8 nm bandwidth, the filter must be 15 cm in diameter and mounted externally to the telescope optics. The filter thermal control required a filter design optimized for minimum bandpass shift with temperature, a thermal analysis of substrate materials for maximum temperature uniformity, and a thermal radiation analysis to determine the parameter sensitivity of the radiation shield for the filter, the filter thermal recovery time after occultation, and heater power to maintain filter performance in the earth-staring geosynchronous environment.

  9. Development of narrow-band low-frequency active filters for DC railway vehicles

    SciTech Connect

    Weem, J. van der

    1994-12-31

    To avoid failures in the signalling systems of light-rail plants low frequency components of the line current may often not exceed specified limits. These limits are in the range of 0.1% of the line current. Presently the low frequency components are damped with passive filters. This paper proposes an active filter to reduce the low frequency components of the line current. A method for dimensioning a digital control algorithm for active filters, which are implemented in the railway vehicle, is presented. Time domain simulations are carried out. They predicted a good behaviour of the active filter for all kinds of vehicles and different realistic conditions. The active filter was realized with an IGBT-inverter and the filter algorithm was implemented in a microcontroller, to ensure a high flexibility. The measurements presented in this paper prove the validity of the simulations. 19 refs.

  10. Simulator spectral characterization using balloon calibrated solar cells with narrow band pass filters

    NASA Technical Reports Server (NTRS)

    Goodelle, G. S.; Brooks, G. R.; Seaman, C. H.

    1981-01-01

    The development and implementation of an instrument for spectral measurement of solar simulators for testing solar cell characteristics is reported. The device was constructed for detecting changes in solar simulator behavior and for comparing simulator spectral irradiance to solar AM0 output. It consists of a standard solar cell equipped with a band pass filter narrow enough so that, when flown on a balloon to sufficient altitude along with sufficient numbers of cells, each equipped with filters of different bandpass ratings, the entire spectral response of the standard cell can be determined. Measured short circuit currents from the balloon flights thus produce cell devices which, when exposed to solar simulator light, have a current which does or does not respond as observed under actual AM0 conditions. Improvements of the filtered cells in terms of finer bandpass filter tuning and measurement of temperature coefficients are indicated.

  11. Precise photometric redshifts with a narrow-band filter set: the PAU survey at the William Herschel Telescope

    NASA Astrophysics Data System (ADS)

    Martí, P.; Miquel, R.; Castander, F. J.; Gaztañaga, E.; Eriksen, M.; Sánchez, C.

    2014-07-01

    The Physics of the Accelerating Universe (PAU) survey at the William Herschel Telescope will use a new optical camera (PAUCam) with a large set of narrow-band filters to perform a photometric galaxy survey with a quasi-spectroscopic redshift precision of σ(z)/(1 + z) ˜ 0.0035 and map the large-scale structure of the universe in three dimensions up to iAB < 22.5-23.0. In this paper, we present a detailed photo-z performance study using photometric simulations for 40 equally spaced 12.5-nm-wide (full width at half-maximum) filters with an ˜25 per cent overlap and spanning the wavelength range from 450 to 850 nm, together with a ugrizY broad-band filter system. We then present the migration matrix rij, containing the probability that a galaxy in a true redshift bin j is measured in a photo-z bin i, and study its effect on the determination of galaxy auto- and cross-correlations. Finally, we also study the impact on the photo-z performance of small variations of the filter set in terms of width, wavelength coverage, etc., and find a broad region where slightly modified filter sets provide similar results, with the original set being close to optimal.

  12. Optical properties of narrow-band spectral filter coatings related to layer structure and preparation.

    PubMed

    Gibson, D; Lissberger, P H

    1983-01-15

    The optical properties of thirty-five all-dielectric spectral filter coatings for the visible spectrum have been investigated and correlated with the deposition conditions of the constituent layers of cryolite and zinc sulfide and with the processes which occur when the coatings are exposed to atmosphere. It will be shown that the results of measurements of transmittance and reflectance over the passband wavelengths can be predicted theoretically only if account is taken of absorption in the layers and scattering at the rough boundaries and of changes in the refractive indices of the layers due to water penetration. PMID:18195779

  13. Measurements of global UV irradiance at Terranova Bay, Antactica, by a home made narrow band filter radiometer

    NASA Astrophysics Data System (ADS)

    Salvatore, Scaglione; di Sarcina, Ilaria; Flori, Daniele; Menchini, Francesca

    2010-05-01

    Filter radiometers measure the solar radiation in several channels (typically 4 to 7) with a bandwith from 2 to 10 nm. They require less maintenance than the spectroradiometer and they are able to work in hostile environment as for instance the polar regions. The spectral resolution depends on the width at half maximum (FWHM) of the filters and is generally lower than the spectroradiometer resolution (0.5 nm). Other than the robustness of this instruments, the main advantage of the filter radiometers is the high frequency with which all wavelengths can be measured, making this class of instrument well suited for investigating short term irradiance variation. In this work is presented the results of UV irradiance measurements performed by a very narrow band (FWHM less than 1 nm) filter radiometer at Antarctica Italia Base, Mario Zucchelli Station, Terranova Bay, lat. 74° 41.6084' south and lon. 164° 05.9224' est. All-dielectric Fabry-Perot filters were manufactured in the laboratories of the Optical Coating Group, ENEA, by the ion beam assistance physical vapor deposition technique. Nine filters select nine different wavelengths in the UV spectral range from 296.5 nm to 377 nm with about 1 minute of measurement period, i.e. each wavelength is measured about 1250 times per day. At the moment the radiometer are permanently located near MZS and the data are daily downloaded in ENEA, Rome, by a dedicated satellite channel. During the Antarctica winter the radiometer will be in standby mode, in this season MZS is closed, and it will be start to measure again in the Antarctica spring.

  14. Effects of Narrow-band IR-A and of Water-Filtered Infrared A on Fibroblasts.

    PubMed

    Knels, Lilla; Valtink, Monika; Piazena, Helmut; de la Vega Marin, Jamlec; Gommel, Kerstin; Lupp, Amelie; Roehlecke, Cora; Mehner, Mirko; Funk, Richard H W

    2016-05-01

    Exposures of the skin with electromagnetic radiation of wavelengths between 670 nm and 1400 nm are often used as a general treatment to improve wound healing and reduce pain, for example, in chronic diabetic skin lesions. We investigated the effects of water-filtered infrared A (wIRA) and of narrow-band IR-A provided by a light-emitting diode LED (LED-IR-A) irradiation in vitro on 3T3 fibroblast cultures under defined conditions with and without glyoxal administration. Glyoxal triggers the formation of advanced glycation end products, thereby mimicking a diabetic metabolic state. Cell viability and apoptotic changes were determined by flow cytometry after vital staining with Annexin V, YO-PRO-1 and propidium iodide (PI), and by SubG1 assay. Mitochondrial function and oxidative stress were examined by vital staining for radical production, mitochondrial membrane potential (MMP) and the ratio of reduced-to-oxidized glutathione (GSH/GSSG). The metabolic state was monitored by a resazurin conversion assay. The numbers of apoptotic cells were reduced in cultures irradiated with wIRA or LED-IR-A. More mitochondria showed a well-polarized MMP after wIRA irradiation in glyoxal damaged cells. LED-IR-A treatment specifically restored the GSH/GSSG ratio. The immediate positive effects of wIRA and LED-IR-A observed in living cells, particularly on mitochondria, reflect the therapeutic benefits of wIRA and LED-IR-A. PMID:26876482

  15. Reduction of timing jitter and intensity noise in normal-dispersion passively mode-locked fiber lasers by narrow band-pass filtering.

    PubMed

    Qin, Peng; Song, Youjian; Kim, Hyoji; Shin, Junho; Kwon, Dohyeon; Hu, Minglie; Wang, Chingyue; Kim, Jungwon

    2014-11-17

    Fiber lasers mode-locked with normal cavity dispersion have recently attracted great attention due to large output pulse energy and femtosecond pulse duration. Here we accurately characterized the timing jitter of normal-dispersion fiber lasers using a balanced cross-correlation method. The timing jitter characterization experiments show that the timing jitter of normal-dispersion mode-locked fiber lasers can be significantly reduced by using narrow band-pass filtering (e.g., 7-nm bandwidth filtering in this work). We further identify that the timing jitter of the fiber laser is confined in a limited range, which is almost independent of cavity dispersion map due to the amplifier-similariton formation by insertion of the narrow bandpass filter. The lowest observed timing jitter reaches 0.57 fs (rms) integrated from 10 kHz to 10 MHz Fourier frequency. The rms relative intensity noise (RIN) is also reduced from 0.37% to 0.02% (integrated from 1 kHz to 5 MHz Fourier frequency) by the insertion of narrow band-pass filter. PMID:25402069

  16. Narrow-band pass filter array for integrated opto-electronic spectroscopy detectors to assess esophageal tissue

    PubMed Central

    Ferreira, Débora S.; Mirkovic, Jelena; Wolffenbuttel, Reinoud F.; Correia, José H.; Feld, Michael S.; Minas, Graça

    2011-01-01

    A strategy for spectroscopy tissue diagnosis using a small number of wavelengths is reported. The feasibility to accurately quantify tissue information using only 16 wavelengths is demonstrated with several wavelength reduction simulations of the existing esophageal data set. These results are an important step for the development of a miniaturized, robust and low-cost spectroscopy system. This system is based on a sub-millimeter high-selective filter array that offers prospects for a simplified miniature spectrographic detector for a future diagnostic tool to improve the diagnosis of dysplasia. Several thin-film optical filters are optimized and fabricated and its spectral performance is shown to be sufficient for the selection of specific wavelength bands. PMID:21698030

  17. Optically tunable optical filter

    NASA Astrophysics Data System (ADS)

    James, Robert T. B.; Wah, Christopher; Iizuka, Keigo; Shimotahira, Hiroshi

    1995-12-01

    We experimentally demonstrate an optically tunable optical filter that uses photorefractive barium titanate. With our filter we implement a spectrum analyzer at 632.8 nm with a resolution of 1.2 nm. We simulate a wavelength-division multiplexing system by separating two semiconductor laser diodes, at 1560 nm and 1578 nm, with the same filter. The filter has a bandwidth of 6.9 nm. We also use the same filter to take 2.5-nm-wide slices out of a 20-nm-wide superluminescent diode centered at 840 nm. As a result, we experimentally demonstrate a phenomenal tuning range from 632.8 to 1578 nm with a single filtering device.

  18. Energy distribution measurement of narrow-band ultrashort x-ray beams via K-edge filters subtraction

    SciTech Connect

    Cardarelli, Paolo; Di Domenico, Giovanni; Marziani, Michele; Mucollari, Irena; Pupillo, Gaia; Sisini, Francesco; Taibi, Angelo; Gambaccini, Mauro

    2012-10-01

    The characterization of novel x-ray sources includes the measurement of the photon flux and the energy distribution of the produced beam. The aim of BEATS2 experiment at the SPARC-LAB facility of the INFN National Laboratories of Frascati (Rome, Italy) is to investigate possible medical applications of an x-ray source based on Thomson relativistic back-scattering. This source is expected to produce a pulsed quasi-monochromatic x-ray beam with an instantaneous flux of 10{sup 20} ph/s in pulses 10 ps long and with an average energy of about 20 keV. A direct measurement of energy distribution of this beam is very difficult with traditional detectors because of the extremely high photon flux. In this paper, we present a method for the evaluation of the energy distribution of quasi-monochromatic x-ray beams based on beam filtration with K-edge absorbing foils in the energy range of interest (16-22 keV). The technique was tested measuring the energy distribution of an x-ray beam having a spectrum similar to the expected one (SPARC-LAB Thomson source) by using a tungsten anode x-ray tube properly filtered and powered. The energy distribution obtained has been compared with the one measured with a HPGe detector showing very good agreement.

  19. Narrow-band generation in random distributed feedback fiber laser.

    PubMed

    Sugavanam, Srikanth; Tarasov, Nikita; Shu, Xuewen; Churkin, Dmitry V

    2013-07-15

    Narrow-band emission of spectral width down to ~0.05 nm line-width is achieved in the random distributed feedback fiber laser employing narrow-band fiber Bragg grating or fiber Fabry-Perot interferometer filters. The observed line-width is ~10 times less than line-width of other demonstrated up to date random distributed feedback fiber lasers. The random DFB laser with Fabry-Perot interferometer filter provides simultaneously multi-wavelength and narrow-band (within each line) generation with possibility of further wavelength tuning. PMID:23938497

  20. Development of the Universal Tunable Filter and High-resolution Imaging Observation with the Fuxian Solar Observatory

    NASA Astrophysics Data System (ADS)

    Hagino, M.; Ichimoto, K.; Ueno, S.; Kimura, G.; Otsuji, K.; Kitai, R.; Zhong, L.; Xu, Z.; Shinoda, K.; Hara, H.; Suematsu, Y.; Shimizu, T.

    2016-04-01

    We have developed a new narrow-band universal tunable filter to perform imaging spectroscopy of the solar chromosphere. The development stage of the filter has been almost finished and we shifted to the scientific observation phase by using large grand-based telescopes. Using the filter, a series of high-resolution images were obtained with the 1m vacuum solar telescope at the Fuxian Solar Observatory. We succeeded in observing several flares and fine structures of the chromospheric layer.

  1. A Lyman-alpha tunable acousto-optic filter for detecting superthermal flare protons

    NASA Technical Reports Server (NTRS)

    Mickey, Donald L.

    1994-01-01

    The goal of this project was to develop and characterize a narrow-band, tunable filter for use near the Lyman-alpha line of hydrogen at 121.6 nm. Such a filter could form the critical component of an instrument to observe asymmetries in the solar Lyman-alpha line, caused by energetic protons accelerated during the impulsive phase of solar flares. Characteristic charge-exchange nonthermal emission at Lyman alpha should be produced when sub-MeV protons are injected into the chromosphere, but no instrument suitable for their detection has been developed. Such an instrument would require a narrow-band (less than 0.01 nm) tunable filter with aperture and throughput consistent with imaging a solar active region at 0.1 second intervals. The development of acousto-optic tunable filters (AOTF) suitable for use as compact, simple tunable filters for astronomical work suggested an investigation into the use of an AOTF at Lyman-alpha.

  2. The development of a tunable, single-frequency ultraviolet laser source for UV filtered Rayleigh scattering

    NASA Technical Reports Server (NTRS)

    Finkelstein, N.; Gambogi, J.; Lempert, Walter R.; Miles, Richard B.; Rines, G. A.; Finch, A.; Schwarz, R. A.

    1995-01-01

    We present the development of a flexible, high power, narrow line width, tunable ultraviolet source for diagnostic application. By frequency tripling the output of a pulsed titanium-sapphire laser, we achieve broadly tunable (227-360 nm) ultraviolet light with high quality spatial and spectral resolution. We also present the characterization of a mercury vapor cell which provides a narrow band, sharp edge absorption filter at 253.7 nm. These two components form the basis for the extension of the Filtered Rayleigh Scattering technique into the ultraviolet. The UV-FRS system is comprised of four pieces: a single frequency, cw tunable Ti:Sapphire seeding source; a high-powered pulsed Ti:Sapphire oscillator; a third harmonic generator system; and an atomic mercury vapor filter. In this paper we discuss the development and characterization of each of these elements.

  3. The Brazilian Tunable Filter Imager for the SOAR Telescope

    NASA Astrophysics Data System (ADS)

    Mendes de Oliveira, Cláudia; Taylor, Keith; Quint, Bruno; Andrade, Denis; Ferrari, Fabrício; Laporte, Rene; Ramos, Giseli de A.; Dani Guzman, Christian; Cavalcanti, Luiz; de Calasans, Alvaro; Ramirez Fernandez, Javier; Gutierrez Castañeda, Edna Carolina; Jones, Damien; Fontes, Fernando Luis; Molina, Ana Maria; Fialho, Fábio; Plana, Henri; Jablonski, Francisco J.; Reitano, Luiz; Daigle, Olivier; Scarano, Sergio; Amram, Philippe; Balard, Philippe; Gach, Jean-Luc; Carignan, Claude

    2013-04-01

    This article presents a description of a new Tunable Filter Instrument for the SOAR telescope. The Brazilian Tunable Filter Imager (BTFI) is a highly versatile new technology to be used both in seeing-limited mode and at higher spatial fidelity using the SAM Ground-Layer Adaptive Optics facility (SOAR Adaptive Module) which is being deployed at the SOAR telescope. Such an instrument presents important new science capabilities for the SOAR astronomical community, from studies of the centers of nearby galaxies and the insterstellar medium to statistical cosmological investigations. The BTFI concept takes advantage of three new technologies. The imaging Bragg Tunable Filter (iBTF) concept utilizes Volume Phase Holographic Gratings in a double-pass configuration as a tunable filter, while a new Fabry-Perot (FP) concept involves the use of commercially available technologies which allow a single FP etalon to act over a very large range of interference orders and hence spectral resolutions. Both of these filter technologies will be used in the same instrument. The combination allows for highly versatile capabilities. Spectral resolutions spanning the range between 25 and 30,000 can be achieved in the same instrument through the use of iBTF at low resolution and scanning FPs beyond R ~ 2,000 with some overlap in the mid-range. The third component of the new technologies deployed in BTFI is the use of EMCCDs, which allow for rapid and cyclical wavelength scanning thus mitigating the damaging effect of atmospheric variability through the acquisition of the data cube. An additional important feature of the instrument is that it has two optical channels which allow for the simultaneous recording of the narrow-band, filtered image with the remaining (complementary) broadband light. This avoids the otherwise inevitable uncertainties inherent in tunable filter imaging using a single detector, which is subject to temporal variability of the atmospheric conditions. The system was

  4. Long wave infrared tunable filter based on guided mode resonant effect

    NASA Astrophysics Data System (ADS)

    Mirotznik, Mark S.; Gupta, Neelam; McElhiney, Morgan; Carey, Victoria

    2016-05-01

    We describe here a tunable long wave infrared (LWIR) band filter based on the guided mode resonant filter (GMRF) effect. The device consists of a subwavelength dielectric grating sandwiched between planar layers of contrasting dielectric materials. Using a rigorous electromagnetic design and analysis method we demonstrate how a strong narrow band reflectance can be induced. Moreover, the resonant wavelength can be easily tuned over the entire 8-12 micron band by mechanically tilting the device with respect to the optical axis. Simulation and experimental results are presented demonstrating the effectiveness of the device.

  5. [Preliminary study on using acousto-optic tunable filter as wavelength selector for atomic absorption spectrometry].

    PubMed

    Zhao, Li-wei; Zhang, Yi-hua; Wang, Mei-jia; Song, Da-qian; Zhang, Han-qi; Jin, Qin-han

    2002-06-01

    An acousto-optic tunable filter (AOTF) is an all-solid-state, electronic monochromator that is based on the diffraction of light by an acoustic wave in an anisotropic crystal. It is a new kind of tunable small filter with narrow band compared with traditional unicolor filter. The filter can diffract incident white light at a specific wavelength when a specific radio frequency is applied into it. An AAS experimental setup using a microwave plasma torch (MPT) as the atomizer, and a visible AOTF as the wavelength selector was developed and the analytical performance was evaluated by determination of Na. The effect on the absorption signal of some operating conditions, including the observation height, the microwave forward power and the carrier and support gas flow rates for MPT, were investigated. The detection limit for Na was shown to be 0.23 microgram.mL-1 and the relative standard deviation was 2.6% (n = 6). PMID:12938338

  6. FILTER-INDUCED BIAS IN Lyα EMITTER SURVEYS: A COMPARISON BETWEEN STANDARD AND TUNABLE FILTERS. GRAN TELESCOPIO CANARIAS PRELIMINARY RESULTS

    SciTech Connect

    De Diego, J. A.; De Leo, M. A.; Cepa, J.; Bongiovanni, A.; Verdugo, T.; Sánchez-Portal, M.

    2013-10-01

    Lyα emitter (LAE) surveys have successfully used the excess in a narrowband filter compared to a nearby broadband image to find candidates. However, the odd spectral energy distribution (SED) of LAEs combined with the instrumental profile has important effects on the properties of the candidate samples extracted from these surveys. We investigate the effect of the bandpass width and the transmission profile of the narrowband filters used for extracting LAE candidates at redshifts z ≅ 6.5 through Monte Carlo simulations, and we present pilot observations to test the performance of tunable filters to find LAEs and other emission-line candidates. We compare the samples obtained using a narrow ideal rectangular filter, the Subaru NB921 narrowband filter, and sweeping across a wavelength range using the ultra-narrow-band tunable filters of the instrument OSIRIS, installed at the 10.4 m Gran Telescopio Canarias. We use this instrument for extracting LAE candidates from a small set of real observations. Broadband data from the Subaru, Hubble Space Telescope, and Spitzer databases were used for fitting SEDs to calculate photometric redshifts and to identify interlopers. Narrowband surveys are very efficient in finding LAEs in large sky areas, but the samples obtained are not evenly distributed in redshift along the filter bandpass, and the number of LAEs with equivalent widths <60 Å can be underestimated. These biased results do not appear in samples obtained using ultra-narrow-band tunable filters. However, the field size of tunable filters is restricted because of the variation of the effective wavelength across the image. Thus, narrowband and ultra-narrow-band surveys are complementary strategies to investigate high-redshift LAEs.

  7. Measuring Potassium in Exoplanet Atmospheres with the OSIRIS Tunable Filter

    NASA Astrophysics Data System (ADS)

    Colón, K. D.; Deeg, H. J.; Ford, E. B.; Redfield, S.; Fortney, J. J.; Shabram, M.; Mahadevan, S.

    2013-05-01

    We report observations of the exoplanet host-star HD 80606 using the OSIRIS tunable filter imager. Very-high-precision, narrow-band photometry in four bandpasses around the K I absorption feature was acquired during the January 2010 transit of HD 80606b, with further off-transit observations taken January and April of 2010. We obtained differential photometric precisions of ~2.08×10^-4 for the in-transit flux ratio measured at 769.91 nm, which probes the K I line core. The observed changes in the depth of the transit across several wavelengths is equivalent to a ~4.2% change in the apparent planetary radius with wavelength, which is much larger than the atmospheric scale height. This implies the observations probed the atmosphere at very low pressures as well as a dramatic change in the pressure at which the optical depth reaches unity across the bands observed. We hypothesize that the excess absorption may be due to K I in a high-speed wind being driven from the exoplanet's exosphere and discuss the viability of this and alternative interpretations. We also present similar observations of the exoplanet XO-2b that were acquired recently and which are currently being analysed. Finally, we discuss future prospects for exoplanet characterization using tunable filter spectrophotometry.

  8. An optimization of the FPGA/NIOS adaptive FIR filter using linear prediction to reduce narrow band RFI for the next generation ground-based ultra-high energy cosmic-ray experiment

    NASA Astrophysics Data System (ADS)

    Szadkowski, Zbigniew; Fraenkel, E. D.; Glas, Dariusz; Legumina, Remigiusz

    2013-12-01

    The electromagnetic part of an extensive air shower developing in the atmosphere provides significant information complementary to that obtained by water Cherenkov detectors which are predominantly sensitive to the muonic content of an air shower at ground. The emissions can be observed in the frequency band between 10 and 100 MHz. However, this frequency range is significantly contaminated by narrow-band RFI and other human-made distortions. The Auger Engineering Radio Array currently suppresses the RFI by multiple time-to-frequency domain conversions using an FFT procedure as well as by a set of manually chosen IIR notch filters in the time-domain. An alternative approach developed in this paper is an adaptive FIR filter based on linear prediction (LP). The coefficients for the linear predictor are dynamically refreshed and calculated in the virtual NIOS processor. The radio detector is an autonomous system installed on the Argentinean pampas and supplied from a solar panel. Powerful calculation capacity inside the FPGA is a factor. Power consumption versus the degree of effectiveness of the calculation inside the FPGA is a figure of merit to be minimized. Results show that the RFI contamination can be significantly suppressed by the LP FIR filter for 64 or less stages.

  9. Tunable-Bandwidth Filter System

    NASA Technical Reports Server (NTRS)

    Bailey, John W.

    2004-01-01

    A tunable-bandwidth filter system (TBFS), now undergoing development, is intended to be part of a remote sensing multispectral imaging system that will operate in the visible and near infrared spectral region (wavelengths from 400 to 900 nm). Attributes of the TBFS include rapid tunability of the pass band over a wide wavelength range and high transmission efficiency. The TBFS is based on a unique integration of two pairs of broadband Raman reflection holographic filters with two rotating spherical lenses. In experiments, a prototype of the TBFS, was shown to be capable of spectral sampling of images in the visible range over a 200 nm spectral range with a spectral resolution of 30 nm. The figure depicts the optical layout of a prototype of the TBFS as part of a laboratory multispectral imaging system for the spectral sampling of color test images in two orthogonal polarizations. Each pair of broadband Raman reflection holographic filters is mounted at an equatorial plane between two halves of a spherical lens. The two filters in each pair are characterized by steep spectral slopes (equivalently, narrow spectral edges), no ripple or side lobes in their pass bands, and a few nanometers of non-overlapping wavelength range between their pass bands. Each spherical lens and thus the filter pair within it is rotated in order to rapidly tune its pass band. The rotations of are effected by electronically controlled, programmable, high-precision rotation stages. The rotations are coordinated by electronic circuits operating under overall supervision of a personal computer in order to obtain the desired variation of the overall pass bands with time. Embedding the filters inside the spherical lenses increases the range of the hologram incidence angles, making it possible to continuously tune the pass and stop bands of the filters over a wider wavelength range. In addition, each spherical lens also serves as part of the imaging optics: The telephoto lens focuses incoming light

  10. Tunable-Bandwidth Filter System

    NASA Technical Reports Server (NTRS)

    Aye, Tin; Yu, Kevin; Dimov, Fedor; Savant, Gajendra

    2006-01-01

    A tunable-bandwidth filter system (TBFS), now undergoing development, is intended to be part of a remote-sensing multispectral imaging system that will operate in the visible and near infrared spectral region (wavelengths from 400 to 900 nm). Attributes of the TBFS include rapid tunability of the pass band over a wide wavelength range and high transmission efficiency. The TBFS is based on a unique integration of two pairs of broadband Raman reflection holographic filters with two rotating spherical lenses. In experiments, a prototype of the TBFS was shown to be capable of spectral sampling of images in the visible range over a 200-nm spectral range with a spectral resolution of .30 nm. The figure depicts the optical layout of a prototype of the TBFS as part of a laboratory multispectral imaging system for the spectral sampling of color test images in two orthogonal polarizations. Each pair of broadband Raman reflection holographic filters is mounted at an equatorial plane between two halves of a spherical lens. The two filters in each pair are characterized by steep spectral slopes (equivalently, narrow spectral edges), no ripple or side lobes in their pass bands, and a few nanometers of non-overlapping wavelength range between their pass bands. Each spherical lens and thus the filter pair within it is rotated in order to rapidly tune its pass band. The rotations of the lenses are effected by electronically controlled, programmable, high-precision rotation stages. The rotations are coordinated by electronic circuits operating under overall supervision of a personal computer in order to obtain the desired variation of the overall pass bands with time. Embedding the filters inside the spherical lenses increases the range of the hologram incidence angles, making it possible to continuously tune the pass and stop bands of the filters over a wider wavelength range. In addition, each spherical lens also serves as part of the imaging optics: The telephoto lens focuses

  11. Narrowband multispectral liquid crystal tunable filter.

    PubMed

    Abuleil, Marwan; Abdulhalim, Ibrahim

    2016-05-01

    Multispectral tunable filters with high performance are desirable components in various biomedical and industrial applications. In this Letter, we present a new narrowband multispectral tunable filter with high throughput over a wide dynamic range. It is composed from a wideband large dynamic range liquid crystal tunable filter combined with a multiple narrowbands spectral filter made of two stacks of photonic crystals and cavity layer in between. The filter tunes between nine spectral bands covering the range 450-1000 nm with bandwidth <10  nm and throughput >80%. PMID:27128048

  12. Tunable Optical Filters for Space Exploration

    NASA Technical Reports Server (NTRS)

    Crandall, Charles; Clark, Natalie; Davis, Patricia P.

    2007-01-01

    Spectrally tunable liquid crystal filters provide numerous advantages and several challenges in space applications. We discuss the tradeoffs in design elements for tunable liquid crystal birefringent filters with special consideration required for space exploration applications. In this paper we present a summary of our development of tunable filters for NASA space exploration. In particular we discuss the application of tunable liquid crystals in guidance navigation and control in space exploration programs. We present a summary of design considerations for improving speed, field of view, transmission of liquid crystal tunable filters for space exploration. In conclusion, the current state of the art of several NASA LaRC assembled filters is presented and their performance compared to the predicted spectra using our PolarTools modeling software.

  13. Tunable filters using wideband elastic resonators.

    PubMed

    Kadota, Michio; Ogami, Takashi; Kimura, Tetsuya; Daimon, Katsuya

    2013-10-01

    Currently, an ultra-wideband resonator is greatly needed to realize a tunable filter with a wide tunable range, because mobile phones with multiple bands and cognitive radio systems require such tunable filters to simplify their circuits. Although tunable filters have been studied using SAW resonators, their tunable range was insufficient for the filters even when wideband SAW resonators with a bandwidth of 17% were used. Therefore, the fabrication of wider-bandwidth resonators has been attempted with the goal of realizing tunable filters with wide tunable ranges. In this study, an SH0- mode plate wave resonator in a 27.5°YX-LiNbO3 plate with an ultra-wide bandwidth of 29.1%, a high impedance ratio of 98 dB, and a high Q (Q(r) = 700 and Q(a) = 720) was realized. Two types of tunable filters were constructed using such SH0-mode resonators and capacitors. As a result, tunable ranges (bands) of 13% to 19% were obtained. The possibility of applying the SH0-mode resonator in the high-frequency gigahertz range is discussed. PMID:24081261

  14. Recent development of infrared tunable filter

    NASA Astrophysics Data System (ADS)

    Liu, Dafu; Xu, Qinfei; Mo, Defeng

    2015-04-01

    Researchers are engaging on tunable infrared (IR) filters, miniature Fabry-Perot optical devices, to operate IR detector like a spectrometer. This kind of devices was used in astronomical detection field in the 1950s. To meet the miniature, lightweight requirements of the optical detection system, researchers began to make small, lightweight, and cheap tunable IR filters. Nowadays researchers have applied a variety of different structures and the IR filter, and are attempting to integrate them with IR detectors directly. Tunable filter thin film mechanical and thermal properties, and working conditions will affect the tunable filter optical performance. In this article we give two main influencing factors, interface roughness and curvature effect. we also present and discuss the current development of FPF in different groups around the world.

  15. Combined tunable filters based swept laser source for optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Chen, Minghui; Ding, Zhihua; Wang, Cheng; Huang, Yimei; Chen, Rong; Song, Chengli

    2013-03-01

    We demonstrate a novel ultra-broad tunable bandwidth and narrow instantaneous line-width swept laser source using combined tunable filters working at 1290 nm center wavelength for application in optical coherence tomography. The combined filters consist of a fiber Fabry-Perot tunable filter (FFP-TF) and a polygon mirror with scanning grating based filter. The FFP-TF has the narrow free spectral range (FSR) but ultra-high spectral resolution (narrow instantaneous bandwidth) driven at high frequency far from resonant frequency. The polygon filter in the Littrow configuration is composed of fiber collimator, polygon mirror driven by function generator, and diffractive grating with low groove. Polygon filter coarsely tunes with wide turning range and then FFP-TF finely tunes with narrow band-pass filtering. In contrast to traditional method using single tunable filter, the trade-off between bandwidth and instantaneous line-width is alleviated. The combined filters can realize ultra wide scan range and fairly narrow instantaneous bandwidth simultaneously. Two semiconductor optical amplifiers (SOA) in the parallel manner are used as the gain medium. The wide bandwidth could be obtained by these parallel SOAs to be suitable for sufficient wide range of the polygon filter's FSR because each SOA generates its own spectrum independently. The proposed swept laser source provides an edge-to-edge scanning range of 180 nm covering 1220 to 1400 nm with instantaneous line-width of about 0.03 nm at sweeping rate of 23.3 kHz. The swept laser source with combined filters offers broadband tunable range with narrow instantaneous line-width, which especially benefits for high resolution and deep imaging depth optical frequency domain imaging.

  16. Tunable Filter Made From Three Coupled WGM Resonators

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy; Iltchenko, Vladimir; Maleki, Lute; Matsko, Andrey

    2006-01-01

    A tunable third-order band-pass optical filter has been constructed as an assembly of three coupled, tunable, whispering-gallery-mode resonators similar to the one described in Whispering-Gallery-Mode Tunable Narrow-Band-Pass Filter (NPO-30896), NASA Tech Briefs, Vol. 28, No. 4 (April 2004), page 5a. This filter offers a combination of four characteristics that are desirable for potential applications in photonics: (1) wide real-time tunability accompanied by a high-order filter function, (2) narrowness of the passband, (3) relatively low loss between input and output coupling optical fibers, and (4) a sparse spectrum. In contrast, prior tunable band-pass optical filters have exhibited, at most, two of these four characteristics. As described in several prior NASA Tech Briefs articles, a whispering-gallery-mode (WGM) resonator is a spheroidal, disklike, or toroidal body made of a highly transparent material. It is so named because it is designed to exploit whispering-gallery electromagnetic modes, which are waveguide modes that propagate circumferentially and are concentrated in a narrow toroidal region centered on the equatorial plane and located near the outermost edge. Figure 1 depicts the optical layout of the present filter comprising an assembly of three coupled, tunable WGM resonators. Each WGM resonator is made from a disk of Z-cut LiNbO3 of 3.3-mm diameter and 50-m thickness. The perimeter of the disk is polished and rounded to a radius of curvature of 40 microns. The free spectral range of each WGM resonator is about 13.3 GHz. Gold coats on the flat faces of the disk serve as electrodes for exploiting the electro-optical effect in LiNbO3 for tuning. There is no metal coat on the rounded perimeter region, where the whispering-gallery modes propagate. Light is coupled from an input optical fiber into the whispering-gallery-modes of the first WGM resonator by means of a diamond prism. Another diamond prism is used to couple light from the whispering

  17. Narrow-Band Applications of Communications Satellites.

    ERIC Educational Resources Information Center

    Cowlan, Bert; Horowitz, Andrew

    This paper attempts to describe the advantages of "narrow-band" applications of communications satellites for education. It begins by discussing the general controversy surrounding the use of satellites in education, by placing the concern within the larger context of the general debate over the uses of new technologies in education, and by…

  18. Narrow band gap amorphous silicon semiconductors

    DOEpatents

    Madan, A.; Mahan, A.H.

    1985-01-10

    Disclosed is a narrow band gap amorphous silicon semiconductor comprising an alloy of amorphous silicon and a band gap narrowing element selected from the group consisting of Sn, Ge, and Pb, with an electron donor dopant selected from the group consisting of P, As, Sb, Bi and N. The process for producing the narrow band gap amorphous silicon semiconductor comprises the steps of forming an alloy comprising amorphous silicon and at least one of the aforesaid band gap narrowing elements in amount sufficient to narrow the band gap of the silicon semiconductor alloy below that of amorphous silicon, and also utilizing sufficient amounts of the aforesaid electron donor dopant to maintain the amorphous silicon alloy as an n-type semiconductor.

  19. Integrated optical, acoustically tunable wavelength filter

    NASA Astrophysics Data System (ADS)

    Frangen, J.; Herrmann, H.; Ricken, R.; Seibert, H.; Sohler, W.

    1989-11-01

    A TM/TE convertor is combined with a TE-pass polarizer on a common LiNbO3 chip to obtain an integrated optical, acoustically tunable wavelength filter. Its tuning range is 1.45-1.57 micron wavelength with a filter half-width of 2.8 nm. Due to the combined acoustical/optical strip guide structure used in the mode convertor, a very low acoustic drive power of only 9 mW is required.

  20. Tunable filters for JWST Fine Guidance Sensor

    NASA Astrophysics Data System (ADS)

    Rowlands, Neil; Evans, Clinton; Greenberg, Elliot; Gregory, Phil; Scott, Alan; Thibault, Simon; Poirier, Michel; Doyon, Rene; Hutchings, John B.; Alexander, Russ

    2004-10-01

    The Canadian contribution to the James Webb Space Telescope (JWST) mission will be the Fine Guidance Sensor (FGS), incorporating a science-observing mode using tunable filters. We describe here the requirements, the opto-mechanical design concept and bread-board test results for the JWST FGS tunable filters. The FGS requires two continuously tunable filters over the wavelength ranges 1.2 - 2.4 microns and 2.4 - 4.8 microns each having a spectral resolution in the range of R~70 to 200. The selected implementation uses dielectric coated Fabry-Perot etalon plates with a small air gaps. The design finesse is ~30 and the filters are used in 3rd order. The operating temperature is ~35K. Current coating designs provide implementations that require only five blocking filters in each wavelength range to suppress unwanted orders. The filters will be scanned via the use of low voltage piezo-electric transducers. We present results from cryogenic tests of coating samples, PZT actuators and a structural model. The PZT actuators were found have a displacement of ~3.3 microns at 30K with an applied voltage of 125V, more than sufficient for the required scan of the Fabry-Perot plate spacing. The prototype etalon coating was found to be very stable cryogenically, having a measured change of transmission of only ~1% at 77K. The same coating on a 12.7 mm thick substrate, similar to that planned for the filter, was found to have a 18 nm peak-to-valley surface figure change when cooled to 30K. These results demonstrate that the development of tunable filters for the JWST FGS is on track to meet the technology readiness requirements of the program.

  1. Cascaded Mach–Zehnder interferometer tunable filters

    NASA Astrophysics Data System (ADS)

    Ovvyan, A. P.; Gruhler, N.; Ferrari, S.; Pernice, W. H. P.

    2016-06-01

    By cascading compact and low-loss Mach–Zehnder interferometers (MZIs) embedded within nanophotonic circuits we realize thermo-optically tunable optical filters for the visible wavelength range. Through phase tuning in either arm of the MZI, the filter response with maximum extinction can be shifted beyond one free-spectral range with low electrical power consumption. The working wavelength of our device is aligned with the emission wavelength of the silicon vacancy color center in diamond around 740 nm where we realize a filter depth beyond 36.5 dB. Our approach allows for efficient isolation of the emitted signal intensity in future hybrid nanodiamond-nanophotonic circuits.

  2. Tunable Microwave Filter Design Using Thin-Film Ferroelectric Varactors

    NASA Astrophysics Data System (ADS)

    Haridasan, Vrinda

    Military, space, and consumer-based communication markets alike are moving towards multi-functional, multi-mode, and portable transceiver units. Ferroelectric-based tunable filter designs in RF front-ends are a relatively new area of research that provides a potential solution to support wideband and compact transceiver units. This work presents design methodologies developed to optimize a tunable filter design for system-level integration, and to improve the performance of a ferroelectric-based tunable bandpass filter. An investigative approach to find the origins of high insertion loss exhibited by these filters is also undertaken. A system-aware design guideline and figure of merit for ferroelectric-based tunable band- pass filters is developed. The guideline does not constrain the filter bandwidth as long as it falls within the range of the analog bandwidth of a system's analog to digital converter. A figure of merit (FOM) that optimizes filter design for a specific application is presented. It considers the worst-case filter performance parameters and a tuning sensitivity term that captures the relation between frequency tunability and the underlying material tunability. A non-tunable parasitic fringe capacitance associated with ferroelectric-based planar capacitors is confirmed by simulated and measured results. The fringe capacitance is an appreciable proportion of the tunable capacitance at frequencies of X-band and higher. As ferroelectric-based tunable capac- itors form tunable resonators in the filter design, a proportionally higher fringe capacitance reduces the capacitance tunability which in turn reduces the frequency tunability of the filter. Methods to reduce the fringe capacitance can thus increase frequency tunability or indirectly reduce the filter insertion-loss by trading off the increased tunability achieved to lower loss. A new two-pole tunable filter topology with high frequency tunability (> 30%), steep filter skirts, wide stopband

  3. Tunable photonic filters: a digital signal processing design approach.

    PubMed

    Binh, Le Nguyen

    2009-05-20

    Digital signal processing techniques are used for synthesizing tunable optical filters with variable bandwidth and centered reference frequency including the tunability of the low-pass, high-pass, bandpass, and bandstop optical filters. Potential applications of such filters are discussed, and the design techniques and properties of recursive digital filters are outlined. The basic filter structures, namely, the first-order all-pole optical filter (FOAPOF) and the first-order all-zero optical filter (FOAZOF), are described, and finally the design process of tunable optical filters and the designs of the second-order Butterworth low-pass, high-pass, bandpass, and bandstop tunable optical filters are presented. Indeed, we identify that the all-zero and all-pole networks are equivalent with well known principles of optics of interference and resonance, respectively. It is thus very straightforward to implement tunable optical filters, which is a unique feature. PMID:19458728

  4. Integrated Optical, Acoustically Tunable Wavelength Filter

    NASA Astrophysics Data System (ADS)

    Frangen, J.; Herrmann, Harald; Ricken, Raimund; Seibert, Holger; Sohler, Wolfgang; Strake, E.

    1989-12-01

    An integrated optical, acoustically tunable wavelength filter, consisting of a combination of TM-TE converter and integrated polarizer in LiNbO3, is demonstrated. The filter bandwidth is 2.8 nm; the center wavelength can be tuned from λ = 1.45 pm to λ = 1.57 pm by adjusting the driving acoustic frequency. Due to the combined acoustical/optical strip guide structure, used in the mode converter, a very low acoustic drive power of only 9 mW is required.

  5. Electro-optical tunable birefringent filter

    SciTech Connect

    Levinton, Fred M.

    2012-01-31

    An electrically tunable Lyot type filter is a Lyot that include one or more filter elements. Each filter element may have a planar, solid crystal comprised of a material that exhibits birefringence and is electro-optically active. Transparent electrodes may be coated on each face of the crystal. An input linear light polarizer may be located on one side of the crystal and oriented at 45 degrees to the optical axis of the birefringent crystal. An output linear light polarizer may be located on the other side of the crystal and oriented at -45 degrees with respect to the optical axis of the birefringent crystal. When an electric voltage is applied between the electrodes, the retardation of the crystal changes and so does the spectral transmission of the optical filter.

  6. Narrow band imaging: clinical applications in oral and oropharyngeal cancer.

    PubMed

    Vu, A; Farah, C S

    2016-07-01

    Narrow Band Imaging (NBI) is an endoscopic optical imaging enhancement technology that improves the contrast of mucosal surface texture, and enhances visualisation of mucosal and submucosal vasculature. White light is filtered to emit two 30-nm narrow bands of blue (415 nm) and green light (540 nm) light simultaneously, the former corresponding to the main peak absorption spectrum of haemoglobin, and the latter allowing visualisation of blood vessels in the deeper mucosal and submucosal layers. NBI has been used to better assess oral potentially malignant disorders (OPMD), identify oral and oropharyngeal squamous cell carcinoma (SCC), and to define surgical margins of head and neck malignancies. NBI shows great potential in improving detection rates of OPMD, facilitating better assessment of oral and oropharyngeal SCC, and reducing the risk of recurrence for oral SCC. Although further research is required to better understand and define intrapapillary capillary loop (IPCL) patterns and to relate these with clinical, histopathological and molecular parameters especially for early mucosal changes, there is building evidence to recommend its use as the new gold standard for endoscopic assessment in head and neck oncology. PMID:26713751

  7. Tunable Bragg filters with a phase transition material defect layer.

    PubMed

    Wang, Xi; Gong, Zilun; Dong, Kaichen; Lou, Shuai; Slack, Jonathan; Anders, Andre; Yao, Jie

    2016-09-01

    We propose an all-solid-state tunable Bragg filter with a phase transition material as the defect layer. Bragg filters based on a vanadium dioxide defect layer sandwiched between silicon dioxide/titanium dioxide Bragg gratings are experimentally demonstrated. Temperature dependent reflection spectroscopy shows the dynamic tunability and hysteresis properties of the Bragg filter. Temperature dependent Raman spectroscopy reveals the connection between the tunability and the phase transition of the vanadium dioxide defect layer. This work paves a new avenue in tunable Bragg filter designs and promises more applications by combining phase transition materials and optical cavities. PMID:27607643

  8. Narrow band 3 × 3 Mueller polarimetric endoscopy

    PubMed Central

    Qi, Ji; Ye, Menglong; Singh, Mohan; Clancy, Neil T.; Elson, Daniel S.

    2013-01-01

    Mueller matrix polarimetric imaging has shown potential in tissue diagnosis but is challenging to implement endoscopically. In this work, a narrow band 3 × 3 Mueller matrix polarimetric endoscope was designed by rotating the endoscope to generate 0°, 45° and 90° linearly polarized illumination and positioning a rotating filter wheel in front of the camera containing three polarisers to permit polarization state analysis for backscattered light. The system was validated with a rotating linear polarizer and a diffuse reflection target. Initial measurements of 3 × 3 Mueller matrices on a rat are demonstrated, followed by matrix decomposition into the depolarization and retardance matrices for further analysis. Our work shows the feasibility of implementing polarimetric imaging in a rigid endoscope conveniently and economically in order to reveal diagnostic information. PMID:24298405

  9. MMTF: THE MARYLAND-MAGELLAN TUNABLE FILTER

    SciTech Connect

    Veilleux, S.; Weiner, B. J.; Rupke, D. S. N. E-mail: bjw@as.arizona.edu

    2010-01-15

    This paper describes the Maryland-Magellan Tunable Filter (MMTF) on the Magellan-Baade 6.5 m telescope. MMTF is based on a 150 mm clear aperture Fabry-Perot (FP) etalon that operates in low orders and provides transmission bandpass and central wavelength adjustable from {approx}5 A to {approx}15 A and from {approx}5000 A to over {approx}9200 A, respectively. It is installed in the Inamori Magellan Areal Camera and Spectrograph and delivers an image quality of {approx}0.''5 over a field of view of 27' in diameter (monochromatic over {approx}10'). This versatile and easy-to-operate instrument has been used over the past three years for a wide variety of projects. This paper first reviews the basic principles of FP tunable filters, and then provides a detailed description of the hardware and software associated with MMTF and the techniques developed to observe with this instrument and reduce the data. The main lessons learned in the course of the commissioning and implementation of MMTF are highlighted next, before concluding with a brief outlook on the future of MMTF and of similar facilities which are soon coming on line.

  10. MMTF: The Maryland-Magellan Tunable Filter

    NASA Astrophysics Data System (ADS)

    Veilleux, S.; Weiner, B. J.; Rupke, D. S. N.; McDonald, M.; Birk, C.; Bland-Hawthorn, J.; Dressler, A.; Hare, T.; Osip, D.; Pietraszewski, C.; Vogel, S. N.

    2010-01-01

    This paper describes the Maryland-Magellan Tunable Filter (MMTF) on the Magellan-Baade 6.5 m telescope. MMTF is based on a 150 mm clear aperture Fabry-Perot (FP) etalon that operates in low orders and provides transmission bandpass and central wavelength adjustable from ~5 Å to ~15 Å and from ~5000 Å to over ~9200 Å, respectively. It is installed in the Inamori Magellan Areal Camera and Spectrograph and delivers an image quality of ~0farcs5 over a field of view of 27' in diameter (monochromatic over ~10'). This versatile and easy-to-operate instrument has been used over the past three years for a wide variety of projects. This paper first reviews the basic principles of FP tunable filters, and then provides a detailed description of the hardware and software associated with MMTF and the techniques developed to observe with this instrument and reduce the data. The main lessons learned in the course of the commissioning and implementation of MMTF are highlighted next, before concluding with a brief outlook on the future of MMTF and of similar facilities which are soon coming on line.

  11. MEMS tunable filter for telecom applications

    NASA Astrophysics Data System (ADS)

    Overstolz, Thomas; Niederer, Guido; Noell, Wilfried; Gale, Michael T.; Herzig, Hans Peter; Obi, Samuel; Thiele, Hans; de Rooij, Nicolaas F.

    2004-08-01

    We report on an angle-tunable oblique incidence resonant grating filter that can be used to drop individual channels from the C-band for incident TE-polarized light. For tuning purpose, the filter is glued onto a tiltable platform of a MEMS device. Continues scanning of the platform allows to monitor channel presence and power. The reflected wavelength is tuned by changing the angle of incidence of the resonant grating filter, which is composed of two thin films with a grating pattern on top of it. The first layer on a glass substrate acts as a waveguide, and the second layer separates the waveguide from the grating. The grating has been patterned by holographic recording and dry etching. The filter works over a wavelength range of 1520-1580 nm and its response has a Lorentian shape with 0.5 nm FWHM peak width. The MEMS part is based on SOI technology and is processed in only two DRIE steps. The platform measures 2 x 2 mm2 with a through-hole of 1.6 x 1.8 mm2 for light transmission. Two arrays of combs attached to the platform as well as a set of four static combs are used to electrostatically incline the platform by +/- 4° with a driving voltage of about 60 V.

  12. Imaging Spectrometer Using a Liquid Crystal Tunable Filter

    NASA Technical Reports Server (NTRS)

    Chrien, Tomas G.; Chovit, Christopher; Miller, Peter J.

    1993-01-01

    A demonstration imaging spectrometer using a liquid crystal tunable filter (LCTF) was built and tested on a hot air balloon platform. The LCTF is a tunable polarization interference or Lyot filter. The LCTF enables a small, light weight, low power, band sequential imaging spectrometer design.

  13. Wideband tunable optoelectronic oscillator based on a phase modulator and a tunable optical filter.

    PubMed

    Xie, Xiaopeng; Zhang, Cheng; Sun, Tao; Guo, Peng; Zhu, Xiaoqi; Zhu, Lixin; Hu, Weiwei; Chen, Zhangyuan

    2013-03-01

    A widely tunable optoelectronic oscillator (OEO) based on a broadband phase modulator and a tunable optical bandpass filter is proposed and experimentally demonstrated. A tunable range from 4.74 to 38.38 GHz is realized by directly tuning the bandwidth of the optical bandpass filter. To the best of our knowledge, this is the widest fundamental frequency tunable range ever achieved by an OEO. The phase noise performance of the generated signal is also investigated. The single-sideband phase noise is below -120 dBc/Hz at an offset of 10 KHz within the whole tunable range. PMID:23455255

  14. Multiple-bipolar-tap tunable spectrum sliced microwave photonic filter.

    PubMed

    Chen, Tong; Yi, Xiaoke; Huang, Thomas; Minasian, Robert A

    2010-12-01

    A spectrum sliced microwave photonic signal processor structure, which is all-fiber based and features simplicity, together with the ability to realize tunability, reconfigurability, bipolar taps, and multiple-tap rf filtering, is presented. It is based on thermally controlled optical slicing filters induced into two linearly chirped fiber Bragg gratings. Experimental results demonstrate the realization of versatile microwave photonic filters with frequency tunable, reconfiguration, and bipolar-tap generation capabilities. PMID:21124570

  15. Optical Filter Assembly for Interplanetary Optical Communications

    NASA Technical Reports Server (NTRS)

    Chen, Yijiang; Hemmati, Hamid

    2013-01-01

    Ground-based, narrow-band, high throughput optical filters are required for optical links from deep space. We report on the development of a tunable filter assembly that operates at telecommunication window of 1550 nanometers. Low insertion loss of 0.5 decibels and bandwidth of 90 picometers over a 2000 nanometers operational range of detectors has been achieved.

  16. Microwave photonic comb filter with ultra-fast tunability.

    PubMed

    Jiang, H Y; Yan, L S; Pan, Y; Pan, W; Luo, B; Zou, X H; Eggleton, B J

    2015-11-01

    A microwave comb filter with ultra-fast tunability is proposed based on the fundamental delay-line microwave photonic filter. The central frequency of the passband or stopband in such a filter can be rapidly adjusted, along with the independent tunability of the free spectral range (FSR). Experimental results show that the central frequency of the transfer function is electronically tuned with a frequency difference of half of the FSR at a speed of <100  ps. Such high-speed tunability is vital for high-speed microwave switching, frequency hopping, cognitive radio, and next-generation radar systems. PMID:26512477

  17. Narrow band photometry of selected asteroids

    NASA Technical Reports Server (NTRS)

    Rajamohan, R.; Bhargavi, S. G.

    1992-01-01

    The CCD photometry of selected asteroids was carried out to check for possible cometary activity in them. To distinguish the asteroids with possible cometary activity from those of the main belt, each object of interest was observed in two filters; one centered on the C2 emission band at 5140A (90A bandpass) and the other centered on the nearby continuum at 4845A (65A bandpass). None of the observed asteroids appear to have any C2 emission.

  18. The Narrow-Band Model and Semi-Conductor Theory

    ERIC Educational Resources Information Center

    Tanner, B. K.

    1976-01-01

    Applies the narrow-band model to the instruction of intrinsic and extrinsic semiconductors along with the phenomenon of compensation. Advocates the model for undergraduate instruction due to its intuitive appeal and mathematical simplicity. (CP)

  19. Tunable thin-film optical filters for hyperspectral microscopy

    NASA Astrophysics Data System (ADS)

    Favreau, Peter F.; Rich, Thomas C.; Prabhat, Prashant; Leavesley, Silas J.

    2013-02-01

    Hyperspectral imaging was originally developed for use in remote sensing applications. More recently, it has been applied to biological imaging systems, such as fluorescence microscopes. The ability to distinguish molecules based on spectral differences has been especially advantageous for identifying fluorophores in highly autofluorescent tissues. A key component of hyperspectral imaging systems is wavelength filtering. Each filtering technology used for hyperspectral imaging has corresponding advantages and disadvantages. Recently, a new optical filtering technology has been developed that uses multi-layered thin-film optical filters that can be rotated, with respect to incident light, to control the center wavelength of the pass-band. Compared to the majority of tunable filter technologies, these filters have superior optical performance including greater than 90% transmission, steep spectral edges and high out-of-band blocking. Hence, tunable thin-film optical filters present optical characteristics that may make them well-suited for many biological spectral imaging applications. An array of tunable thin-film filters was implemented on an inverted fluorescence microscope (TE 2000, Nikon Instruments) to cover the full visible wavelength range. Images of a previously published model, GFP-expressing endothelial cells in the lung, were acquired using a charge-coupled device camera (Rolera EM-C2, Q-Imaging). This model sample presents fluorescently-labeled cells in a highly autofluorescent environment. Linear unmixing of hyperspectral images indicates that thin-film tunable filters provide equivalent spectral discrimination to our previous acousto-optic tunable filter-based approach, with increased signal-to-noise characteristics. Hence, tunable multi-layered thin film optical filters may provide greatly improved spectral filtering characteristics and therefore enable wider acceptance of hyperspectral widefield microscopy.

  20. Imaging spectrograph for interstellar shocks (ISIS): a far-ultraviolet narrow-band imaging rocket payload

    NASA Astrophysics Data System (ADS)

    Beasley, Matthew N.; Wilkinson, Erik

    2001-12-01

    We present a new instrument for narrow band imaging without the use of conventional interference filters. This instrument will image the OVI doublet at 103.2 and 103.8 nm, the brightest astrophysical emission line from diffuse gas at 300,000 degrees. Gases at this temperature, formed mostly by supernovae blast waves, are key to understanding the energy budget of the galaxy. To date, there are no high spatial resolution narrow-band images of OVI, although some low spatial resolution narrow maps have been acquired with conventional spectrographs. Using the imaging power of a conventional two-optic Gregorian telescope in conjunction with aberration-corrected holography, we can acquire narrow band images with subarcsecond spatial resolution. An aberration-corrected holographically ruled grating in place of the secondary optic is used to diffract the ultraviolet light to stigmatic focus. Additionally, the use of few optical surfaces minimizes the light loss from poor reflectivity of materials in the far ultraviolet (FUV), thereby maximizing instrument sensitivity. This instrument is the first to use aberration-corrected holographic gratings to produce a narrow-band imaging capability in this fashion. We are now developing a rocket payload to demonstrate the power of this technique with particular application to non-radiative shocks in the interstellar medium. We present the optical design, instrument performance, and relevant scientific simulations.

  1. Microwave photonic bandstop filter with wide tunability and adjustable bandwidth.

    PubMed

    Li, Wei; Yang, Chengwu; Wang, Ling; Yuan, Zhilin; Liu, Jianguo; Li, Ming; Zhu, Ninghua

    2015-12-28

    A microwave photonic bandstop filter is proposed and experimentally demonstrated in this work. The filter exhibits promising performance combination of reconfigurability, frequency tunability, and bandwidth adjustment. The phase modulation on two orthogonal polarization states produces a bandpass and a lowpass MPF, respectively. The key concept of destructive interference between the bandpass and lowpass MPF enables the reconfiguration of MPF from bandpass to bandstop. By adjusting the wavelength of two orthogonally polarized optical carriers and the bandwidth of an optical bandpass filter, the bandstop filter is tunable in terms of center frequency and bandwidth. PMID:26832021

  2. Highly tunable microwave and millimeter wave filtering using photonic technology

    NASA Astrophysics Data System (ADS)

    Seregelyi, Joe; Lu, Ping; Paquet, Stéphane; Celo, Dritan; Mihailov, Stephen J.

    2015-05-01

    The design for a photonic microwave filter tunable in both bandwidth and operating frequency is proposed and experimentally demonstrated. The circuit is based on a single sideband modulator used in conjunction with two or more transmission fiber Bragg gratings (FBGs) cascaded in series. It is demonstrated that the optical filtering characteristics of the FBGs are instrumental in defining the shape of the microwave filter, and the numerical modeling was used to optimize these characteristics. A multiphase-shift transmission FBG design is used to increase the dynamic range of the filter, control the filter ripple, and maximize the slope of the filter skirts. Initial measurements confirmed the design theory and demonstrated a working microwave filter with a bandwidth tunable from approximately 2 to 3.5 GHz and an 18 GHz operating frequency tuning range. Further work is required to refine the FBG manufacturing process and reduce the impact of fabrication errors.

  3. Thin-film tunable filters for hyperspectral fluorescence microscopy

    PubMed Central

    Favreau, Peter; Hernandez, Clarissa; Lindsey, Ashley Stringfellow; Alvarez, Diego F.; Rich, Thomas; Prabhat, Prashant

    2013-01-01

    Abstract. Hyperspectral imaging is a powerful tool that acquires data from many spectral bands, forming a contiguous spectrum. Hyperspectral imaging was originally developed for remote sensing applications; however, hyperspectral techniques have since been applied to biological fluorescence imaging applications, such as fluorescence microscopy and small animal fluorescence imaging. The spectral filtering method largely determines the sensitivity and specificity of any hyperspectral imaging system. There are several types of spectral filtering hardware available for microscopy systems, most commonly acousto-optic tunable filters (AOTFs) and liquid crystal tunable filters (LCTFs). These filtering technologies have advantages and disadvantages. Here, we present a novel tunable filter for hyperspectral imaging—the thin-film tunable filter (TFTF). The TFTF presents several advantages over AOTFs and LCTFs, most notably, a high percentage transmission and a high out-of-band optical density (OD). We present a comparison of a TFTF-based hyperspectral microscopy system and a commercially available AOTF-based system. We have characterized the light transmission, wavelength calibration, and OD of both systems, and have then evaluated the capability of each system for discriminating between green fluorescent protein and highly autofluorescent lung tissue. Our results suggest that TFTFs are an alternative approach for hyperspectral filtering that offers improved transmission and out-of-band blocking. These characteristics make TFTFs well suited for other biomedical imaging devices, such as ophthalmoscopes or endoscopes. PMID:24077519

  4. A novel tunable cascaded IIR microwave photonic filter

    NASA Astrophysics Data System (ADS)

    Zhou, Lina; Zhang, Xinliang; Xu, Enming; Yu, Yuan; Li, Xiang; Huang, Dexiu

    2010-07-01

    A new tunable cascaded infinite impulse response (IIR) microwave photonic filter is presented, based on a novel configuration in which a semiconductor optical amplifier (SOA) is inserted between two active recirculating delay line (RDL) loops. Due to wavelength conversion with cross-gain modulation (XGM) in SOA, interferences between light beams traveling different paths are canceled, ensuring a stable transmission. By employing this configuration, a cascaded IIR microwave photonic filter is firstly achieved. The free spectral range (FSR) and the Q factor are both increased significantly by adopting "vernier effect" technique in the IIR filter. The structure is also tunable by adjusting the length of one RDL loop.

  5. Variable bandwidth birefringent filter for tunable femtosecond lasers

    SciTech Connect

    Naganuma, K.; Lenz, G.; Ippen, E.P. )

    1992-10-01

    A design for a birefringent filter is described, which is suitable for tunable femtosecond lasers. Using a single plate, which has a steeply diving optic axis, two-octave tunability is attained with negligible deterioration of the stopband rejection. For a specific wavelength region, it means that the filter's bandwidth can be changed by a factor of four. Another characteristic of the design is that, for the same bandwidth, the proposed plate is five times thicker than a conventional plate in which the optic axis is parallel to the surface. Thus, etalon effects can be avoided. Tuning characteristics of color center lasers utilizing the new filter are also presented. 18 refs.

  6. Recovering physical properties from narrow-band photometry

    NASA Astrophysics Data System (ADS)

    Schoenell, W.; Cid Fernandes, R.; Benítez, N.; Vale Asari, N.

    2013-05-01

    Our aim in this work is to answer, using simulated narrow-band photometry data, the following general question: What can we learn about galaxies from these new generation cosmological surveys? For instance, can we estimate stellar age and metallicity distributions? Can we separate star-forming galaxies from AGN? Can we measure emission lines, nebular abundances and extinction? With what precision? To accomplish this, we selected a sample of about 300k galaxies with good S/N from the SDSS and divided them in two groups: 200k objects and a template library of 100k. We corrected the spectra to z = 0 and converted them to filter fluxes. Using a statistical approach, we calculated a Probability Distribution Function (PDF) for each property of each object and the library. Since we have the properties of all the data from the STARLIGHT-SDSS database, we could compare them with the results obtained from summaries of the PDF (mean, median, etc). Our results shows that we retrieve the weighted average of the log of the galaxy age with a good error margin (σ ≈ 0.1 - 0.2 dex), and similarly for the physical properties such as mass-to-light ratio, mean stellar metallicity, etc. Furthermore, our main result is that we can derive emission line intensities and ratios with similar precision. This makes this method unique in comparison to the other methods on the market to analyze photometry data and shows that, from the point of view of galaxy studies, future photometric surveys will be much more useful than anticipated.

  7. Flux-Calibrated Emission-Line Imaging of Extended Sources Using GTC/OSIRIS Tunable Filters

    NASA Astrophysics Data System (ADS)

    Mayya, Y. D.; Rosa González, D.; Vega, O.; Méndez-Abreu, J.; Terlevich, R.; Terlevich, E.; Bertone, E.; Rodríguez-Merino, L. H.; Muñoz-Tuñón, C.; Rodríguez-Espinosa, J. M.; Sánchez Almeida, J.; Aguerri, J. A. L.

    2012-08-01

    We investigate the utility of the tunable filters (TFs) for obtaining flux-calibrated emission-line maps of extended objects such as galactic nebulae and nearby galaxies using the Optical System for Imaging and low Resolution Integrated Spectroscopy (OSIRIS) at the 10.4-m Gran Telescopio Canarias (GTC). Despite the relatively large field of view (FoV) of OSIRIS (8' × 8'), the change in wavelength across the field (~80 Å) and the long tail of the TF spectral response function are hindrances for obtaining accurate flux-calibrated emission-line maps of extended sources. The purpose of this article is to demonstrate that emission-line maps useful for diagnostics of nebulae can be generated over the entire FoV of OSIRIS if we make use of theoretically well-understood characteristics of TFs. We have successfully generated the flux-calibrated images of the nearby large late-type spiral galaxy M101 in the emission lines of Hα, [N II]λ6583, [S II]λ6716 and [S II]λ6731. We find that the present uncertainty in setting the central wavelength of TFs (~1 Å) is the biggest source of error in the emission-line fluxes. By comparing the Hα fluxes of H II regions in our images with the fluxes derived from Hα images obtained using narrow-band filters, we estimate an error of ~11% in our fluxes. The flux-calibration of the images was carried out by fitting the Sloan Digital Sky Survey (SDSS) griz magnitudes of in-frame stars with the stellar spectra from the SDSS spectral database. This method resulted in an accuracy of 3% in flux-calibration of any narrow-band image, which is as good as, if not better than, what has been feasible using the observations of spectrophotometric standard stars. Thus time-consuming calibration images need not be taken. A user-friendly script under the IRAF environment was developed and is available on request. Based on observations made with the Gran Telescopio Canarias (GTC), installed in the Spanish Observatorio del Roque de los Muchachos of the

  8. Tunable rubidium excited state Voigt atomic optical filter.

    PubMed

    Yin, Longfei; Luo, Bin; Xiong, Junyu; Guo, Hong

    2016-03-21

    A tunable rubidium excited state Voigt atomic optical filter working at optical communication wavelength (1.5 μm) is realized. The filter achieves a peak transmittance of 57.6% with a double-peak structure, in which each one has a bandwidth of 600 MHz. Benefiting from the Voigt type structure, the magnetic field of the filter can be tuned from 0 to 1600 gauss, and a peak transmittance tunability of 1.6 GHz can thus be realized. Different from the excited state Faraday type filter, the pump efficiency in the Voigt filter is affected a lot by the pump polarization. Measured absorption results of the pump laser and transmittances of the signal laser both prove that the vertical linear polarization pumping is the most efficient in the Voigt filter. PMID:27136803

  9. A simplified scheme for generating narrow-band mid-ultraviolet laser radiation

    SciTech Connect

    Almog, G.; Scholz, M. Weber, W.; Leisching, P.; Kaenders, W.; Udem, Th.

    2015-03-15

    We report on the development and characterization of continuous, narrow-band, and tunable laser systems that use direct second-harmonic generation from blue and green diode lasers with an output power level of up to 11.1 mW in the mid-ultraviolet. One of our laser systems was tuned to the mercury 6{sup 1}S{sub 0} → 6{sup 3}P{sub 1} intercombination line at 253.7 nm. We could perform Doppler-free saturation spectroscopy on this line and were able to lock our laser to the transition frequency on long time scales.

  10. A simplified scheme for generating narrow-band mid-ultraviolet laser radiation.

    PubMed

    Almog, G; Scholz, M; Weber, W; Leisching, P; Kaenders, W; Udem, Th

    2015-03-01

    We report on the development and characterization of continuous, narrow-band, and tunable laser systems that use direct second-harmonic generation from blue and green diode lasers with an output power level of up to 11.1 mW in the mid-ultraviolet. One of our laser systems was tuned to the mercury 6(1)S0 → 6(3)P1 intercombination line at 253.7 nm. We could perform Doppler-free saturation spectroscopy on this line and were able to lock our laser to the transition frequency on long time scales. PMID:25832214

  11. Narrow bandpass tunable terahertz filter based on photonic crystal cavity.

    PubMed

    He, Jinglong; Liu, Pingan; He, Yalan; Hong, Zhi

    2012-02-20

    We have fabricated a very narrow bandpass tunable terahertz (THz) filter based on a one-dimensional photonic crystal cavity. Since the filter consists of silicon wafers and air spacers, it has a very high quality factor of about 1500. The full width at half maximum (FWHM) of the passband is only about 200 MHz, and the peak transmission is higher than -4 dB. Besides, the central frequency can be tuned rapidly over the entire bandgap with the length of cavity adjusted by a motorized linear stage. Further analytical calculations indicate that a high-Q tunable filter with both high peak transmission and wide tunable range is possible if thinner silicon layers are used. PMID:22358169

  12. General formulation for the calibration and characterization of narrow-gap etalons: the OSIRIS/GTC tunable filters case

    NASA Astrophysics Data System (ADS)

    González, J. J.; Cepa, J.; González-Serrano, J. I.; Sánchez-Portal, M.

    2014-10-01

    Tunable filters (TFs) are a powerful way of implementing narrow-band imaging mode over wide wavelength ranges, without the need of purchasing a large number of narrow-band filters covering all strong emission or absorption lines at any redshift. However, one of its main features is a wavelength variation across the field of view, sometimes termed the phase effect. In this work, an anomalous phase effect is reported and characterized for the Optical System for Imaging and low Resolution Integrated Spectroscopy (OSIRIS) instrument at the 10.4 m Gran Telescopio Canarias. The transmitted wavelength across the field of view of the instrument depends, not only on the distance to the optical centre, but on wavelength. This effect is calibrated for the red TF of OSIRIS by measuring both normal-incidence light at laboratory and spectral lamps at the telescope at non-normal incidence. This effect can be explained by taking into account the inner coatings of the etalon. In a high spectral resolution etalon, the gap between plates is much larger than the thickness of the inner reflective coatings. In the case of a TF, like that in OSIRIS, the coatings thickness could be of the order of the cavity, which changes drastically the effective gap of the etalon. We show that by including thick and dispersive coatings into the interference equations, the observed anomalous phase effect can be perfectly reproduced. In fact, we find that, for the OSIRIS red TF, a two-coatings model fits the data with an rms of 0.5 Å at all wavelengths and incidence angles. This is a general physical model that can be applied to other TF instruments.

  13. Temperature Tunable Air-Gap Etalon Filter

    NASA Technical Reports Server (NTRS)

    Krainak, Michael A.; Stephen, Mark A.; Lunt, David L.

    1998-01-01

    We report on experimental measurements of a temperature tuned air-gap etalon filter. The filter exhibits temperature dependent wavelength tuning of 54 pm/C. It has a nominal center wavelength of 532 nm. The etalon filter has a 27 pm optical bandpass and 600 pm free spectral range (finesse approximately 22). The experimental results are in close agreement with etalon theory.

  14. Tunable Optical Filters Having Electro-optic Whispering-gallery-mode Resonators

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy (Inventor); Ilchenko, Vladimir (Inventor); Matsko, Andrey B. (Inventor); Maleki, Lutfollah (Inventor)

    2006-01-01

    Tunable optical filters using whispering-gallery-mode (WGM) optical resonators are described. The WGM optical resonator in a filter exhibits an electro-optical effect and hence is tunable by applying a control electrical signal.

  15. Characterizing the Atmospheres of Super-Earths and Hot-Jupiters with Narrow-Band Photometry

    NASA Astrophysics Data System (ADS)

    Colon, Knicole D.; Gaidos, E.; Wilson, P. A.; Ford, E. B.; Sing, D. K.; Ballester, G. E.; Desert, J.; Ehrenreich, D.; Fortney, J. J.; Lecavelier des Etangs, A.; Lopez-Morales, M.; Morley, C.; Pettitt, A.; Pont, F.; Vidal-Madjar, A.

    2014-01-01

    Nearly one thousand extrasolar planets have been discovered, but none are considered true analogs to solar system planets. Instead, we characterize some planets as “super-Earths” or “hot-Jupiters.” It has been possible to characterize the atmospheres of some of these planets via transit observations, which is a crucial stepping stone towards future studies of true solar system analogs. We present narrow-band photometry of several transiting planets, including the super-Earth GJ 1214b and the hot-Jupiters XO-2b and TrES-2b. For GJ 1214b, most studies find that the transmission spectrum is flat, which favors either a high mean molecular weight or cloudy/hazy hydrogen (H) rich atmosphere model. We observed seven transits of GJ 1214b through a narrow K-band (2.141 micron) filter with the Wide Field Camera on the 3.8 meter United Kingdom Infrared Telescope. We observed another five transits at 800-900 nm using tunable filters with the Optical System for Imaging and low Resolution Integrated Spectroscopy (OSIRIS) on the 10.4 meter Gran Telescopio Canarias (GTC). Our observations support a flat transmission spectrum for GJ 1214b, but we also find that a hydrogen-dominated upper atmosphere cannot be excluded. For hot-Jupiters, potassium has been predicted to be one of the strongest sources of opacity at optical wavelengths and has been previously detected in the atmospheres of XO-2b and TrES-2b. Using OSIRIS on the GTC, we observed three transits of XO-2b and two transits of TrES-2b in multiple bandpasses around the potassium absorption feature at 770 nm. Our technique is somewhat different than in previous studies, and we use our observations to constrain the amount of potassium in these exoplanet atmospheres. We consider how our studies set the stage for future investigations of true Earth and Jupiter analogs that have not yet been discovered.

  16. Spectral imaging characterization of MOEM tunable Fabry-Perot filter

    NASA Astrophysics Data System (ADS)

    Gupta, Neelam

    2012-03-01

    A miniature MOEM tunable Fabry-Perot (FP) filter development program to fabricate filters operating over spectral regions from the visible to the longwave infrared has recently succeeded in fabricating filters operating over visible/near infrared wavelength region from 400 to 800 nm. The main objective of this program is to design miniature hyperspectral imagers by placing such a miniature tunable FP filter in front of a commercial focal plane array with a suitable optical train. This novel MOEM filter design is based on using two semitransparent 30-nm thick silver-film mirrors-one fixed and one moving with application of an electrostatic force. The silver films were grown on low-cost thin commercial quartz wafers with low total thickness variation. The moving mirror is held in place by three leaf spring arm structures which were fabricated by wet etching of the quartz substrate. The size of the MOEM device is 18×24 mm2. The tunable FP filter has a 6-mm optical aperture. The fixed part has three electrodes to apply voltages and the moving mirror is used as a ground electrode. Au bumps were deposited in both parts in order to control the initial air gap distance and an Au-Au bonding was used to bond the two parts together. The electrostatic actuation changes the spacing between the two mirrors which changes the transmitted wavelength. The spectral imaging performance of MOEM filter was characterized using a tunable source and a CCD camera with suitable optics. This paper describes the MOEM filter, its characteristics and present spectral imaging characterization experiment and results.

  17. Narrow-band oscillations in probabilistic cellular automata.

    PubMed

    Puljic, Marko; Kozma, Robert

    2008-08-01

    Dynamical properties of neural populations are studied using probabilistic cellular automata. Previous work demonstrated the emergence of critical behavior as the function of system noise and density of long-range axonal connections. Finite-size scaling theory identified critical properties, which were consistent with properties of a weak Ising universality class. The present work extends the studies to neural populations with excitatory and inhibitory interactions. It is shown that the populations can exhibit narrow-band oscillations when confined to a range of inhibition levels, with clear boundaries marking the parameter region of prominent oscillations. Phase diagrams have been constructed to characterize unimodal, bimodal, and quadromodal oscillatory states. The significance of these findings is discussed in the context of large-scale narrow-band oscillations in neural tissues, as observed in electroencephalographic and magnetoencephalographic measurements. PMID:18850928

  18. Digital tunable color filter and beam scanner

    NASA Technical Reports Server (NTRS)

    Wang, Y.

    2000-01-01

    A new technology invented at JPL of color filtering and beam scanning device based on electro-optical switching of internal-reflection states have been proposed for use in DWDM, display and measurement applications.

  19. Tunable broadband light coupler based on two parallel all-fiber acousto-optic tunable filters.

    PubMed

    Zhang, Wending; Huang, Ligang; Gao, Feng; Bo, Fang; Zhang, Guoquan; Xu, Jingjun

    2013-07-15

    Based on the evanescent-field coupling between the cladding modes of two adjacent and parallel all-fiber acousto-optic tunable filters, tunable broadband light coupling with relatively uniform insertion loss of trapping spectrum was achieved. In the experiments, a wide spectral tuning range from 1490 nm to 1610 nm, covering the whole C- and L-band and parts of S-bands, was demonstrated with a wavelength tunability slope of -0.72 nm/kHz. The insertion loss of the trapping spectrum was uniform (around -5.0 dB, which can be improved with a longer evanescent-field coupling length) within the whole tuning spectral range. Such a light coupling structure would be useful in tunable broadband light coupler and broadband optical fiber add/drop multiplexer for applications in coarse wavelength division multiplexing systems. PMID:23938513

  20. Construction of narrow-band regenerative amplifier for momentum imaging spectroscopy of lithium dimer

    SciTech Connect

    Matsuoka, Leo; Hashimoto, Masashi; Yokoyama, Keiichi

    2012-07-11

    We constructed a Ti:Sapphire narrow-band regenerative amplifier as the probe laser of the experiment of momentum imaging spectroscopy of lithium dimer. The spectral profile of the regenerative cavity was designed by three birefringent filters and a plate of etalon. With 1.1-mJ pumping by the second harmonics of Nd:YLF laser, mode-locked seed pulses were amplified to {approx}25 {mu}J at 1-kHz repetition, with the bandwidth of {approx}0.7 cm{sup -1}.

  1. A tunable microwave plasma photonic crystal filter

    SciTech Connect

    Wang, B.; Cappelli, M. A.

    2015-10-26

    The integration of gaseous plasma elements into a microwave photonic crystal band gap cavity structure allows for active tuning of the device. An alumina rod array microwave photonic crystal waveguide resonator is simulated and characterized through finite difference time domain methods. A gaseous plasma element is integrated into the cavity structure and the effect of plasma density on the transmission properties of the structure is investigated. We show, through both simulations and experiments, that the permittivity of the plasma can be adjusted to shift the peak resonance to allow for both switching and tunability of transmission. The experimentally measured peak shifts in transmission are compared to those simulated and the electron density of the gaseous plasma element is calculated and compared to values determined from the measured discharge current density.

  2. A tunable microwave plasma photonic crystal filter

    NASA Astrophysics Data System (ADS)

    Wang, B.; Cappelli, M. A.

    2015-10-01

    The integration of gaseous plasma elements into a microwave photonic crystal band gap cavity structure allows for active tuning of the device. An alumina rod array microwave photonic crystal waveguide resonator is simulated and characterized through finite difference time domain methods. A gaseous plasma element is integrated into the cavity structure and the effect of plasma density on the transmission properties of the structure is investigated. We show, through both simulations and experiments, that the permittivity of the plasma can be adjusted to shift the peak resonance to allow for both switching and tunability of transmission. The experimentally measured peak shifts in transmission are compared to those simulated and the electron density of the gaseous plasma element is calculated and compared to values determined from the measured discharge current density.

  3. Electronically tunable coherent Raman spectroscopy using acousto-optics tunable filter.

    PubMed

    Petrov, Georgi I; Meng, Zhaokai; Yakovlev, Vladislav V

    2015-09-21

    Fast and sensitive Raman spectroscopy measurements are imperative for a large number of applications in biomedical imaging, remote sensing and material characterization. In this report, by introducing an electronically-tunable acousto-optical filter as a wavelength selector, we demonstrated a novel instrumentation to the broadband coherent Raman spectroscopy. System's tunability allows assessing Raman transitions ranging from <400 cm(-1) to 4500 cm(-1). We validated the use of the new instrumentation by collecting coherent anti-Stokes spectra and stimulated Raman spectra of various samples. PMID:26406668

  4. Gelled colloidal crystals as tunable optical filters for spectrophotometers

    NASA Astrophysics Data System (ADS)

    Sugao, Yukihiro; Onda, Sachiko; Toyotama, Akiko; Takiguchi, Yoshihiro; Sawada, Tsutomu; Hara, Shigeo; Nishikawa, Suguru; Yamanaka, Junpei

    2016-08-01

    We examined the performance of charged colloidal crystals immobilized in a polymer gel as tunable optical filters. The colloidal crystals of charged silica particles (particle diameter = 121 nm; particle concentration = 3.5 vol %; and Bragg wavelength λB = 630–720 nm) were produced by unidirectional crystallization under a temperature gradient. Photocurable gelation reagents were dissolved in the sample beforehand; this enabled gel immobilization of the crystals under ultraviolet illumination. The crystals had dimensions of more than 25 mm2 in area and 1 mm in thickness, and spatial λB variations of less than 1%. Upon mechanical compression, λB values shifted linearly and reversibly over almost the entire visible spectrum. Using the gelled crystals as tunable optical filters, we measured the transmittance spectra of various samples and found them to be in close agreement with those determined using a spectrophotometer equipped with optical gratings.

  5. Fatigue failure of materials under narrow band random vibrations. I.

    NASA Technical Reports Server (NTRS)

    Huang, T. C.; Hubbard, R. B.; Lanz, R. W.

    1971-01-01

    A novel approach for the study of fatigue failure of materials under the multifactor influence of narrow band random vibrations is developed. The approach involves the conduction of an experiment in conjunction with various statistical techniques. Three factors including two statistical properties of the excitation or response are considered and varied simultaneously. A minimum of 6 tests for 3 variables is possible for a fractional f actorial design. The four coefficients of the predicting equation can be independently estimated. A look at 3 predicting equations shows the predominant effect of the root mean square stress of the first order equation.

  6. GTC OSIRIS transiting exoplanet atmospheric survey: detection of potassium in HAT-P-1b from narrow-band spectrophotometry

    NASA Astrophysics Data System (ADS)

    Wilson, P. A.; Sing, D. K.; Nikolov, N.; Lecavelier des Etangs, A.; Pont, F.; Fortney, J. J.; Ballester, G. E.; López-Morales, M.; Désert, J.-M.; Vidal-Madjar, A.

    2015-06-01

    We present the detection of potassium in the atmosphere of HAT-P-1b using optical transit narrow-band photometry. The results are obtained using the 10.4-m Gran Telescopio Canarias together with the OSIRIS instrument in tunable filter imaging mode. We observed four transits, two at continuum wavelengths outside the potassium feature, at 6792 and 8844 Å, and two probing the potassium feature in the line wing at 7582.0 Å and the line core at 7664.9 Å using a 12 Å filter width (R ˜ 650). The planet-to-star radius ratios in the continuum are found to be Rpl/R⋆ = 0.1176 ± 0.0013 at 6792 Å and Rpl/R⋆ = 0.1168 ± 0.0022 at 8844 Å, significantly lower than the two observations in the potassium line: Rpl/R⋆ = 0.1248 ± 0.0014 in the line wing at 7582.0 Å and Rpl/R⋆ = 0.1268 ± 0.0012 in the line core at 7664.9 Å. With a weighted mean of the observations outside the potassium feature Rpl/R⋆ = 0.1174 ± 0.0010, the potassium is detected as an increase in the radius ratio of ΔRpl/R⋆ = 0.0073 ± 0.0017 at 7582.0 Å and ΔRpl/R⋆ = 0.0094 ± 0.0016 at 7664.9 Å (a significance of 4.3σ and 6.1σ, respectively). We hypothesize that the strong detection of potassium is caused by a large scaleheight, which can be explained by a high temperature at the base of the upper atmosphere. A lower mean molecular mass caused by the dissociation of molecular hydrogen into atomic hydrogen by the extreme ultraviolet flux from the host star may also partly explain the amplitude of our detection.

  7. Liquid-crystal tunable filter based on sapphire microspheres.

    PubMed

    Gilardi, Giovanni; Donisi, Domenico; Serpengüzel, Ali; Beccherelli, Romeo

    2009-11-01

    We design an integrated optoelectronic device based on the whispering-gallery modes of a sapphire microsphere integrated with a liquid-crystal tuning medium to produce a narrowband, electrically tunable, channel-dropping filter. The sapphire microsphere is glued over a diffused waveguide in a glass substrate. At the base of the microsphere, a small volume of liquid crystal is infiltrated. We numerically evaluate the performance of the device and demonstrate a voltage tuning of the narrowband resonances. PMID:19881558

  8. Imaging Spectrometer With Liquid-Crystal Tunable Filter

    NASA Technical Reports Server (NTRS)

    Chrien, Thomas G.

    1996-01-01

    Imaging spectrometer constructed from charged-coupled-device video camera; liquid-crystal tunable filter (LCTF) placed in front of camera lens; and associated digital and analog control, signal-processing, and data-processing circuits. To enable operation of instrument in specific application for which designed (balloon flights in cold weather), camera and LCTF surrounded by electric heating pad. Total operating power, excluding that consumed by heating pad, 16 W. Instrument weighs 4.5 kg.

  9. Compact and tunable silicon nitride Bragg grating filters in polymer

    NASA Astrophysics Data System (ADS)

    Zhang, Ziyang; Novo, Alejandro Maese; Liu, Dongliang; Keil, Norbert; Grote, Norbert

    2014-06-01

    A series of tunable filters based on silicon nitride waveguide Bragg gratings buried in polymer are studied, fabricated and analyzed. The gratings are etched completely through the waveguides to improve the peak reflectivity at short grating lengths. Reflectivity from 1% to 70% can be reached when the third-order grating length varies from 16 µm to 160 µm. The experimental results are in good agreement with numerical simulations. Due to its compact size and the thermal advantages of polymer, the filter can be tuned very efficiently by a micro heater buried beneath. A tuning range of 34.5 nm is demonstrated at a heat power of only 22 mW.

  10. Tunable filter using ferroelectric-dielectric periodic multilayer.

    PubMed

    D'souza, Nirmala Maria; Mathew, Vincent

    2015-03-20

    The microwave optical properties of a photonic crystal-based tunable single and multichannel filter are theoretically investigated using the transfer matrix method, finite difference time domain method, and the plane wave expansion method. By applying an external voltage of 8  V/micron about a 35% frequency tuning is obtained. It is found that the number of transmission peaks is directly proportional to the number of periods (N). In addition to this, the dependence of layer thicknesses, angle of incidence and polarization are also analyzed, and it is noticed that the filtering frequency is invariant in angle and polarization. PMID:25968499

  11. Guided-mode resonant polarization-controlled tunable color filters.

    PubMed

    Uddin, Mohammad Jalal; Khaleque, Tanzina; Magnusson, Robert

    2014-05-19

    We demonstrate efficient guided-mode resonant polarization-controlled tunable color filters. The devices consist of subwavelength gratings that are partially etched into a thin silicon-nitride film deposited on a glass substrate. Two color filters with grating periods of 300 nm and 370 nm are designed and fabricated. The 300-nm device exhibits green and blue colors and the 370-nm device generates red and yellow colors for TE and TM polarization, respectively. The pixels have a spectral bandwidth of ~12 nm with efficiencies exceeding 90% for TE polarization and 80% for TM polarization. The devices may find application in displays, image sensors, and biomedical imaging technologies. PMID:24921349

  12. Decomposing a signal into short-time narrow-banded modes

    NASA Astrophysics Data System (ADS)

    McNeill, S. I.

    2016-07-01

    An algorithm for nonparametric decomposition of a signal into the sum of short-time narrow-banded modes (components) is introduced. Specifically, the signal data is augmented with its Hilbert transform to obtain the analytic signal. Then the set of constituent amplitude and frequency modulated (AM-FM) analytic sinusoids, each with slowly varying amplitude and frequency, is sought. The method for obtaining the short-time narrow-banded modes is derived by minimizing an objective function comprised of three criteria: smoothness of the instantaneous amplitude envelope, smoothness of the instantaneous frequency and complete reconstruction of the signal data. A minimum of the objective function is approached using a sequence of suboptimal updates of amplitude and phase. The updates are intuitive, efficient and simple to implement. For a given mode, the amplitude and phase are extracted from the band-pass filtered residual (signal after the other modes are removed), where the band-pass filter is applied about the previous modal instantaneous frequency estimate. The method is demonstrated by application to random output-only vibration data and order tracking data. It is demonstrated that vibration modal responses can be estimated from single channel data and order tracking can be performed without measured tachometer data.

  13. A tunable hole-burning filter for lidar applications

    NASA Astrophysics Data System (ADS)

    Billmers, R. I.; Davis, J.; Squicciarini, M.

    The fundamental physical principles for the development of a 'hole-burning' optical filter based on saturable absorption in dye-doped glasses are outlined. A model was developed to calculate the required pump intensity, throughput, and linewidth for this type of filter. Rhodamine 6G, operating at 532 nm, was found to require a 'warm-up' time of 110 pulses and a pump intensity of 100 kW/sq cm per pulse. The linewidth was calculated to be approximately 15 GHz at 77 K with a throughput of at least 25 percent and five orders of magnitude noise suppression. A 'hole-burning' filter offers significant advantages over current filter technology, including tunability over a 10-nm bandwidth, perfect wavelength and bandwidth matching to the transmitting laser in a pulsed lidar system, transform limited response times, and moderately high throughputs (at least 25 percent).

  14. Novel schemes for the optimization of the SPARC narrow band THz source

    NASA Astrophysics Data System (ADS)

    Marchetti, B.; Bacci, A.; Chiadroni, E.; Cianchi, A.; Ferrario, M.; Mostacci, A.; Pompili, R.; Ronsivalle, C.; Spataro, B.; Zagorodnov, I.

    2015-07-01

    A pulsed, tunable, narrow band radiation source with frequency in the THz region can be obtained collecting the coherent transition radiation produced by a train of ultra-short electron bunches having picosecond scale inter-distance. In this paper, we review the techniques feasible at the SPARC_LAB test facility to produce and manipulate the requested train of electron bunches and we examine the dynamics of their acceleration and compression. In addition, we show how the performances of the train compression and the radiation intensity and bandwidth can be significantly improved through the insertion of a fourth order harmonic cavity, working in the X-band and acting as a longitudinal phase space linearizer.

  15. Novel schemes for the optimization of the SPARC narrow band THz source

    SciTech Connect

    Marchetti, B. Zagorodnov, I.; Bacci, A.; Chiadroni, E.; Ferrario, M.; Pompili, R.; Spataro, B.; Cianchi, A.; Mostacci, A.; Ronsivalle, C.

    2015-07-15

    A pulsed, tunable, narrow band radiation source with frequency in the THz region can be obtained collecting the coherent transition radiation produced by a train of ultra-short electron bunches having picosecond scale inter-distance. In this paper, we review the techniques feasible at the SPARC-LAB test facility to produce and manipulate the requested train of electron bunches and we examine the dynamics of their acceleration and compression. In addition, we show how the performances of the train compression and the radiation intensity and bandwidth can be significantly improved through the insertion of a fourth order harmonic cavity, working in the X-band and acting as a longitudinal phase space linearizer.

  16. Narrow-band injection seeding of a terahertz frequency quantum cascade laser: Selection and suppression of longitudinal modes

    SciTech Connect

    Nong, Hanond Markmann, Sergej; Hekmat, Negar; Jukam, Nathan; Pal, Shovon; Mohandas, Reshma A.; Dean, Paul; Li, Lianhe; Linfield, Edmund H.; Giles Davies, A.; Wieck, Andreas D.

    2014-09-15

    A periodically poled lithium niobate (PPLN) crystal with multiple poling periods is used to generate tunable narrow-bandwidth THz pulses for injection seeding a quantum cascade laser (QCL). We demonstrate that longitudinal modes of the quantum cascade laser close to the gain maximum can be selected or suppressed according to the seed spectrum. The QCL emission spectra obtained by electro-optic sampling from the quantum cascade laser, in the most favorable case, shows high selectivity and amplification of the longitudinal modes that overlap the frequency of the narrow-band seed. Proper selection of the narrow-band THz seed from the PPLN crystal discretely tunes the longitudinal mode emission of the quantum cascade laser. Moreover, the THz wave build-up within the laser cavity is studied as a function of the round-trip time. When the seed frequency is outside the maximum of the gain spectrum the laser emission shifts to the preferential longitudinal mode.

  17. Tunable high-q superconducting notch filter

    DOEpatents

    Pang, C.S.; Falco, C.M.; Kampwirth, R.T.; Schuller, I.K.

    1979-11-29

    A superconducting notch filter is made of three substrates disposed in a cryogenic environment. A superconducting material is disposed on one substrate in a pattern of a circle and an annular ring connected together. The second substrate has a corresponding pattern to form a parallel plate capacitor and the second substrate has the circle and annular ring connected by a superconducting spiral that forms an inductor. The third substrate has a superconducting spiral that is placed parallel to the first superconducting spiral to form a transformer. Relative motion of the first substrate with respect to the second is effected from outside the cryogenic environment to vary the capacitance and hence the frequency of the resonant circuit formed by the superconducting devices.

  18. Quantum information processing with narrow band two-photon state

    NASA Astrophysics Data System (ADS)

    Lu, Yajun

    Application of quantum sources in communication and information processing are believed to bring a new revolution to the on-going information age. The generation of applicable quantum sources such as single photon state and two-photon state, appears to be one of the most difficult in experimental quantum optics. Spontaneous Parametric Down-Conversion (PDC) is known to generate two-photon state, but bandwidth problem makes it less applicable in quantum information processing. The aim of this work is to generate a narrow band two-photon state and apply it to quantum information processing. We start by developing a cavity enhanced PDC device to narrow the bandwidth of the two-photon state. Direct measurement of the bandwidth of the generated state has been made and the quantum theory of such a device has been investigated. An application of this narrow band two-photon state is to generate anti-bunched photons for quantum cryptography, based on the quantum interference between the two-photon state and a coherent state. The feasibility of this scheme for pulsed pump is also investigated. When applying the concept of mode locking in lasers to a two-photon state, we have mode-locked two-photon state which exhibits a comb-like correlation function and may be used for engineering of quantum states in time domain. Other applications such as demonstration of single photon nonlocality, nonlinear sign gate in quantum computation, and direct measurement of quantum beating, will also be addressed.

  19. Enhancing the visibility of injuries with narrow-banded beams of light within the visible light spectrum.

    PubMed

    Limmen, Roxane M; Ceelen, Manon; Reijnders, Udo J L; Joris Stomp, S; de Keijzer, Koos C; Das, Kees

    2013-03-01

    The use of narrow-banded visible light sources in improving the visibility of injuries has been hardly investigated, and studies examining the extent of this improvement are lacking. In this study, narrow-banded beams of light within the visible light spectrum were used to explore their ability in improving the visibility of external injuries. The beams of light were induced by four crime-lites(®) providing narrow-banded beams of light between 400 and 550 nm. The visibility of the injuries was assessed through specific long-pass filters supplied with the set of crime-lites(®) . Forty-three percent of the examined injuries improved in visibility by using the narrow-banded visible light. In addition, injuries were visualized that were not visible or just barely visible to the naked eye. The improvements in visibility were particularly marked with the use of crime-lites(®) "violet" and "blue" covering the spectrum between 400-430 and 430-470 nm. The simple noninvasive method showed a great potential contribution in injury examination. PMID:23278497

  20. Tunable, oblique incidence resonant grating filter for telecommunications.

    PubMed

    Niederer, Guido; Herzig, Hans Peter; Shamir, Joseph; Thiele, Hans; Schnieper, Marc; Zschokke, Christian

    2004-03-10

    We have designed a tunable, oblique-incidence resonant grating filter that covers the C band as an add-drop device for incident TE-polarized light. We tune the filter by tilting a microelectromechanical systems platform onto which the filter is attached. The fabrication tolerances as well as the role of finite incident-beam size and limited device size were addressed. The maximum achievable efficiency of a finite-area device as well as a scaling law that relates the resonance peak width and the minimum device size is derived. In good agreement with simulations, measurements indicate a negligible change in shape of the resonance peak from 1526 nm at a 45 degrees angle of incidence to 1573 nm at a 53 degrees angle with a full width at half-maximum of 0.4 nm. In this range the shift of the peak wavelength is linear with respect to changes in the angle of incidence. PMID:15046172

  1. Shining a new narrow band of light on old problems.

    PubMed

    Chan, Daniel K; Wang, Kenneth K

    2014-06-01

    Improvements in narrow band imaging (NBI) may provide an improved view of colonic mucosa for detection of polyps and adenomas. In this issue, Leung et al. report findings to suggest that this next-generation NBI technology is superior to conventional high-definition white light endoscopy in polyp detection. These findings are based on brighter illumination, which has been a problem with older generations of NBI, which did not increase polyp detection but were useful for polyp characterization. Although these findings are very promising for this new role of second-generation NBI in polyp detection, the study must be viewed with consideration of the history of the older NBI system, the analysis of which through multiple positive and negative studies ultimately led to the conclusion that it was not beneficial for detection. PMID:24896757

  2. Narrow band perfect absorber for maximum localized magnetic and electric field enhancement and sensing applications

    PubMed Central

    Yong, Zhengdong; Zhang, Senlin; Gong, Chensheng; He, Sailing

    2016-01-01

    Plasmonics offer an exciting way to mediate the interaction between light and matter, allowing strong field enhancement and confinement, large absorption and scattering at resonance. However, simultaneous realization of ultra-narrow band perfect absorption and electromagnetic field enhancement is challenging due to the intrinsic high optical losses and radiative damping in metals. Here, we propose an all-metal plasmonic absorber with an absorption bandwidth less than 8 nm and polarization insensitive absorptivity exceeding 99%. Unlike traditional Metal-Dielectric-Metal configurations, we demonstrate that the narrowband perfect absorption and field enhancement are ascribed to the vertical gap plasmonic mode in the deep subwavelength scale, which has a high quality factor of 120 and mode volume of about 10−4 × (λres/n)3. Based on the coupled mode theory, we verify that the diluted field enhancement is proportional to the absorption, and thus perfect absorption is critical to maximum field enhancement. In addition, the proposed perfect absorber can be operated as a refractive index sensor with a sensitivity of 885 nm/RIU and figure of merit as high as 110. It provides a new design strategy for narrow band perfect absorption and local field enhancement, and has potential applications in biosensors, filters and nonlinear optics. PMID:27046540

  3. Narrow band perfect absorber for maximum localized magnetic and electric field enhancement and sensing applications.

    PubMed

    Yong, Zhengdong; Zhang, Senlin; Gong, Chensheng; He, Sailing

    2016-01-01

    Plasmonics offer an exciting way to mediate the interaction between light and matter, allowing strong field enhancement and confinement, large absorption and scattering at resonance. However, simultaneous realization of ultra-narrow band perfect absorption and electromagnetic field enhancement is challenging due to the intrinsic high optical losses and radiative damping in metals. Here, we propose an all-metal plasmonic absorber with an absorption bandwidth less than 8 nm and polarization insensitive absorptivity exceeding 99%. Unlike traditional Metal-Dielectric-Metal configurations, we demonstrate that the narrowband perfect absorption and field enhancement are ascribed to the vertical gap plasmonic mode in the deep subwavelength scale, which has a high quality factor of 120 and mode volume of about 10(-4) × (λres/n)(3). Based on the coupled mode theory, we verify that the diluted field enhancement is proportional to the absorption, and thus perfect absorption is critical to maximum field enhancement. In addition, the proposed perfect absorber can be operated as a refractive index sensor with a sensitivity of 885 nm/RIU and figure of merit as high as 110. It provides a new design strategy for narrow band perfect absorption and local field enhancement, and has potential applications in biosensors, filters and nonlinear optics. PMID:27046540

  4. Fabry-Pérot based narrow band imager for solar filament observations

    NASA Astrophysics Data System (ADS)

    Dhara, Sajal Kumar; Ravindra, Belur; Banyal, Ravinder Kumar

    2016-01-01

    We have recently developed a narrow band imager (NBI) using an air gap based Fabry-Pérot (FP) interferometer at the Indian Institute of Astrophysics, Bangalore. Narrow band imaging is achieved by using an FP interferometer working in combination with an order sorting pre-filter. The NBI can be tuned to a different wavelength position on the line profile by changing the plate separation of the FP. The interferometer has a 50 mm clear aperture with a bandpass of ∼247.8 mÅ and a free spectral range of ∼5.3 Å at λ = 656.3 nm. The developed NBI is used to observe the solar filament in the Hα wavelength. The instrument is being used to image the Sun at chromospheric height and it is also able to scan the Hα spectral line profile at different wavelength positions. We have also made Doppler velocity maps at chromospheric height by taking the blue and red wing images at ±176 mÅ wavelength positions separately away from the line center of the spectral line. In this paper, we present a description of the NBI including lab test results of individual components and some initial observations carried out with this instrument.

  5. Narrow band perfect absorber for maximum localized magnetic and electric field enhancement and sensing applications

    NASA Astrophysics Data System (ADS)

    Yong, Zhengdong; Zhang, Senlin; Gong, Chensheng; He, Sailing

    2016-04-01

    Plasmonics offer an exciting way to mediate the interaction between light and matter, allowing strong field enhancement and confinement, large absorption and scattering at resonance. However, simultaneous realization of ultra-narrow band perfect absorption and electromagnetic field enhancement is challenging due to the intrinsic high optical losses and radiative damping in metals. Here, we propose an all-metal plasmonic absorber with an absorption bandwidth less than 8 nm and polarization insensitive absorptivity exceeding 99%. Unlike traditional Metal-Dielectric-Metal configurations, we demonstrate that the narrowband perfect absorption and field enhancement are ascribed to the vertical gap plasmonic mode in the deep subwavelength scale, which has a high quality factor of 120 and mode volume of about 10‑4 × (λres/n)3. Based on the coupled mode theory, we verify that the diluted field enhancement is proportional to the absorption, and thus perfect absorption is critical to maximum field enhancement. In addition, the proposed perfect absorber can be operated as a refractive index sensor with a sensitivity of 885 nm/RIU and figure of merit as high as 110. It provides a new design strategy for narrow band perfect absorption and local field enhancement, and has potential applications in biosensors, filters and nonlinear optics.

  6. A filterless, visible-blind, narrow-band, and near-infrared photodetector with a gain

    NASA Astrophysics Data System (ADS)

    Shen, Liang; Zhang, Yang; Bai, Yang; Zheng, Xiaopeng; Wang, Qi; Huang, Jinsong

    2016-06-01

    In many applications of near-infrared (NIR) light detection, a band-pass filter is needed to exclude the noise caused by visible light. Here, we demonstrate a filterless, visible-blind, narrow-band NIR photodetector with a full-width at half-maximum of <50 nm for the response spectrum. These devices have a thick (>4 μm) nanocomposite absorbing layers made of polymer-fullerene:lead sulfide (PbS) quantum dots (QDs). The PbS QDs yield a photoconductive gain due to their hole-trapping effect, which effectively enhances both the responsivity and the visible rejection ratio of the external quantum efficiency by >10 fold compared to those without PbS QDs. Encouragingly, the inclusion of the PbS QDs does not increase the device noise. We directly measured a noise equivalent power (NEP) of 6.1 pW cm-2 at 890 nm, and a large linear dynamic range (LDR) over 11 orders of magnitude. The highly sensitive visible-blind NIR narrow-band photodetectors may find applications in biomedical engineering.

  7. A filterless, visible-blind, narrow-band, and near-infrared photodetector with a gain.

    PubMed

    Shen, Liang; Zhang, Yang; Bai, Yang; Zheng, Xiaopeng; Wang, Qi; Huang, Jinsong

    2016-07-14

    In many applications of near-infrared (NIR) light detection, a band-pass filter is needed to exclude the noise caused by visible light. Here, we demonstrate a filterless, visible-blind, narrow-band NIR photodetector with a full-width at half-maximum of <50 nm for the response spectrum. These devices have a thick (>4 μm) nanocomposite absorbing layers made of polymer-fullerene:lead sulfide (PbS) quantum dots (QDs). The PbS QDs yield a photoconductive gain due to their hole-trapping effect, which effectively enhances both the responsivity and the visible rejection ratio of the external quantum efficiency by >10 fold compared to those without PbS QDs. Encouragingly, the inclusion of the PbS QDs does not increase the device noise. We directly measured a noise equivalent power (NEP) of 6.1 pW cm(-2) at 890 nm, and a large linear dynamic range (LDR) over 11 orders of magnitude. The highly sensitive visible-blind NIR narrow-band photodetectors may find applications in biomedical engineering. PMID:27305339

  8. High-speed tunable microwave photonic notch filter based on phase modulator incorporated Lyot filter.

    PubMed

    Ge, Jia; Feng, Hanlin; Scott, Guy; Fok, Mable P

    2015-01-01

    A high-speed tunable microwave photonic notch filter with ultrahigh rejection ratio is presented, which is achieved by semiconductor optical amplifier (SOA)-based single-sideband modulation and optical spectral filtering with a phase modulator-incorporated Lyot (PM-Lyot) filter. By varying the birefringence of the phase modulator through electro-optic effect, electrically tuning of the microwave photonic notch filter is experimentally achieved at tens of gigahertz speed. The use of SOA-polarizer based single-sideband modulation scheme provides good sideband suppression over a wide frequency range, resulting in an ultrahigh rejection ratio of the microwave photonic notch filter. Stable filter spectrum with bandstop rejection ratio over 60 dB is observed over a frequency tuning range from 1.8 to 10 GHz. Compare with standard interferometric notch filter, narrower bandwidth and sharper notch profile are achieved with the unique PM-Lyot filter, resulting in better filter selectivity. Moreover, bandwidth tuning is also achieved through polarization adjustment inside the PM-Lyot filter, that the 10-dB filter bandwidth is tuned from 0.81 to 1.85 GHz. PMID:25531605

  9. MEMS tunable optical filter based on multi-ring resonator

    SciTech Connect

    Dessalegn, Hailu E-mail: tsrinu@ece.iisc.ernet.in; Srinivas, T. E-mail: tsrinu@ece.iisc.ernet.in

    2014-10-15

    We propose a novel MEMS tunable optical filter with a flat-top pass band based on multi-ring resonator in an electrostatically actuated microcantilever for communication application. The filter is basically structured on a microcantilever beam and built in optical integrated ring resonator which is placed in one end of the beam to gain maximum stress on the resonator. Thus, when a DC voltage is applied, the beam will bend, that induces a stress and strain in the ring, which brings a change in refractive index and perimeter of the rings leading to change in the output spectrum shift, providing the tenability as high as 0.68nm/μN and it is capable of tuning up to 1.7nm.

  10. Flat top liquid crystal tunable filter using coupled Fabry-Perot cavities.

    PubMed

    Alboon, Shadi A; Lindquist, Robert G

    2008-01-01

    In this paper, a coupled Fabry-Perot cavities filter, using the liquid crystal as the tunable medium, is investigate to achieve tunable flat top filtering performance across the C and L bands. A tandem coupled Fabry-Perot is presented for a tunable passband filter with flat top and minimum ripple in the passband. The overall tuning range of the filter is 172 nm. Several designs are shown with comparable performance to the commercial available 100 GHz fixed single channel filters. PMID:18521153

  11. In situ calibration of tunable filters: Lyot and Michelson.

    PubMed

    Mudge, Jason; Tarbell, Theodore

    2014-08-01

    Solar imaging optical filter technology has progressed significantly over the past 75 years, and the ability to tune narrowband filters is particularly valuable for solar atmosphere sensing. For example, imaging while tuning over a narrow solar spectral line (emission or absorption) provides two-dimensional measurements of Doppler shifts and magnetic fields. While tuning ability has improved significantly, tuning accuracy can be a challenge over time given system actuator drifts. For many cases, the ability to calibrate these actuators in situ is convenient and cost effective (e.g., ground-based observatories), and for other cases it is required (e.g., in a spacecraft). It is ideal to calibrate in situ without the need for additional hardware such as a spectrometer, and if that cannot be achieved, the next best thing is to do so with minimum additional hardware. Two examples of solar filters that need to be calibrated periodically are: (1) a liquid crystal variable retarder Lyot filter and (2) a tunable Michelson interferometer. For the first, the filter can have a number of stages back-to-back to achieve the desired finesse. Within each stage there is a liquid crystal variable retarder that adds some amount of retardance to the stage's fixed birefringent crystal; this provides wavelength bandpass tuning. For the second, there can be several Michelson interferometers in series each with an actuator to adjust the optical path length in one of its optical paths for tuning. The stacking of these filters implies there is a need to calibrate more than one actuator. An algorithm has been developed to calibrate these types of stacked and nonstacked filters in situ with minimal, if any, hardware additions. PMID:25090330

  12. Research on imaging spectrometer using LC-based tunable filter

    NASA Astrophysics Data System (ADS)

    Shen, Zhixue; Li, Jianfeng; Huang, Lixian; Luo, Fei; Luo, Yongquan; Zhang, Dayong; Long, Yan

    2012-09-01

    A liquid crystal tunable filter (LCTF) with large aperture is developed using PDLC liquid crystal. A small scale imaging spectrometer is established based on this tunable filter. This spectrometer can continuously tuning, or random-access selection of any wavelength in the visible and near infrared (VNIR) band synchronized with the imaging processes. Notable characteristics of this spectrometer include the high flexibility control of its operating channels, the image cubes with high spatial resolution and spectral resolution and the strong ability of acclimation to environmental temperature. The image spatial resolution of each tuning channel is almost near the one of the same camera without the LCTF. The spectral resolution is about 20 nm at 550 nm. This spectrometer works normally under 0-50°C with a maximum power consumption of 10 Watts (with exclusion of the storage module). Due to the optimization of the electrode structure and the driving mode of the Liquid Crystal cell, the switch time between adjacent selected channels can be reduced to 20 ms or even shorter. Spectral imaging experiments in laboratory are accomplished to verify the performance of this spectrometer, which indicate that this compact imaging spectrometer works reliably, and functionally. Possible applications of this imaging spectrometer include medical science, protection of historical relics, criminal investigation, disaster monitoring and mineral detection by remote sensing.

  13. Mechanically-tunable composite filter at low frequencies

    NASA Astrophysics Data System (ADS)

    Wheeland, Sara; Amirkhizi, Alireza V.; Nemat-Nasser, Sia

    2010-04-01

    Previous studies into the possibility of a plasmonic medium of a coiled conductor array in air have shown promise. This work serves to evaluate the possibility of creating a mechanically-tunable composite filter at low frequencies. Copper springs were created with varying starting pitches using a coil winder. These springs were then embedded into a flexible host polymer. The mechanical and electromagnetic properties of each spring design were predicted and tested. Two horn antennas were used to characterize the overall electromagnetic (EM) properties of the composite. The pitch of each spring was increased mechanically through application of force to the entire polymermetal composite at equal intervals, with an EM test completed at each step. Using an Agilent 8510C Vector Network Analyzer (VNA), the frequency spectrum within the microwave range was scanned. Relative amplitude and phase measurements were taken at equal frequency and pitch steps. With no polymer surrounding the springs, plasmon turn-on frequencies were observed to span the microwave bands as the pitch of the springs were increased. Similar results are expected with the springs embedded in a polymeric matrix. These results suggest a method of creating a mechanically-tunable composite filter for use at low frequencies.

  14. Narrow band absorber based on a dielectric nanodisk array on silver film

    NASA Astrophysics Data System (ADS)

    Callewaert, F.; Chen, S.; Butun, S.; Aydin, K.

    2016-07-01

    The simulations of normally incident visible light absorption in a periodic array of dielectric nanodisks on the top of a silver film are presented. Electromagnetic simulations indicate narrow resonances with absorption intensities as large as 95%. The absorption enhancement due to the periodic array can be as high as a factor of 30 compared to an equivalent dielectric film on top of a silver mirror. A parametric study shows that the resonance characteristics and the number of modes can be easily tuned and controlled by the refractive index and the geometric parameters of the nanodisks. In particular, the structure can be tuned to have either a single or two absorption peaks. The characteristics of the two main resonance peaks are described in detail using the simulated electric field profiles and the dispersion relation. Proposed narrowband absorber design utilizing continuous metal films and nanostructured dielectric arrays could be used for narrow-band absorption filters, refractive-index based biosensing applications and thermal emitters.

  15. Five years of comet narrow band photometry and imaging with TRAPPIST

    NASA Astrophysics Data System (ADS)

    Opitom, Cyrielle; Jehin, Emmanuel; Manfroid, Jean; Hutsemékers, Damien; Gillon, Michaël; Magain, Pierre

    2015-11-01

    TRAPPIST is a 60-cm robotic telescope in La Silla Observatory [1] mainly dedicated to the study of exoplanets and comets. The telescope is equipped with a set of narrow band cometary filters designed by the NASA for the Hale-Bopp observing campaign [2]. Since its installation in 2010, we gathered a high quality and homogeneous data set of more than 30 bright comets observed with narrow band filters. Some comets were only observed for a few days but others have been observed weekly during several months on both sides of perihelion. From the images, we derived OH, NH, CN, C2, and C3 production rates using a Haser [3] model in addition to the Afρ parameter as a proxy for the dust production. We computed production rates ratios and the dust color for each comet to study their composition and followed the evolution of these ratios and colors with the heliocentric distance.The TRAPPIST data set, rich of more than 10000 images obtained and reduced in an homogeneous way, allows us to address several fundamental questions such as the pristine or evolutionary origin of composition differences among comets. The evolution of comet activity with the heliocentric distance, the differences between species, and from comet to comet, will be discussed. Finally, the first results about the one year campaign on comet C/2013 US10 (Catalina) and our recent work on the re-determination of Haser scalelengths will be presented.[1] Jehin et al., The Messenger, 145, 2-6, 2011[2] Farnham et al., Icarus, 147, 180-204, 2000[3] Haser, Bulletin de l’Académie Royal des Sciences de Belgique,63, 739, 1957

  16. Superscattering-enhanced narrow band forward scattering antenna

    NASA Astrophysics Data System (ADS)

    Hu, De-Jiao; Zhang, Zhi-You; Du, Jing-Lei

    2015-10-01

    We present a narrow band forward scattering optical antenna which is based on the excitation of distinctive whispering gallery modes (WGMs). The antenna is composed of three coaxial cylinder layers: a dielectric layer is sandwiched between a metallic core and cladding. Owing to the destructive interference between the scattering of the outer metallic cladding and the WGM in the backward direction, the power flow in the forward direction is increased. Simulation and analysis show that in proper geometry conditions, the cavity can be tuned into a superscattering state. At this state, both the zeroth and the first order of WGM are excited and contribute to the total scattering. It is shown that the power ratio (power towards backward divided by power towards forward) can be enhanced to about 27 times larger than that for a non-resonant position by the superscattering. Owing to the confinement of the cladding to WGMs, the wavelength range of effective forward scattering is considerably narrow (about 15 nm). Project supported by the National Natural Science Foundation of China (Grant No. 61377054), the Collaborative Innovation Foundation of Sichuan University, China (Grant No. XTCX 2013002), and the International Cooperation and Exchange of Science and Technology Project in Sichuan Province, China (Grant No. 2013HH0010).

  17. Source characteristics of Jovian narrow-band kilometric radio emissions

    NASA Astrophysics Data System (ADS)

    Reiner, M. J.; Fainberg, J.; Stone, R. G.; Kaiser, M. L.; Desch, M. D.; Manning, R.; Zarka, P.; Pedersen, B.-M.

    1993-07-01

    New observations of Jovian narrow-band kilometric (nKOM) radio emissions were made by the Unified Radio and Plasma Wave (URAP) experiment on the Ulysses spacecraft during the Ulysses-Jupiter encounter in early February 1992. These observations have demonstrated the unique capability of the URAP instrument for determining both the direction and polarization of nKOM radio sources. An important result is the discovery that nKOM radio emission originates from a number of distinct sources located at different Jovian longitudes and at the inner and outermost regions of the Io plasma torus. These sources have been tracked for several Jovian rotations, yielding their corotational lags, their spatial and temporal evolution, and their radiation characteristics at both low latitudes far from Jupiter and at high latitudes near the planet. Both right-hand and left-hand circularly polarized nKOM sources were observed. The polarizations observed for sources in the outermost regions of the torus seem to favor extraordinary mode emission.

  18. Micromachined Tunable Fabry-Perot Filters for Infrared Astronomy

    NASA Technical Reports Server (NTRS)

    Barclay, Richard; Bier, Alexander; Chen, Tina; DiCamillo, Barbara; Deming, Drake; Greenhouse, Matthew; Henry, Ross; Hewagama, Tilak; Jacobson, Mindy; Loughlin, James; Krebs, Carolyn A. (Technical Monitor)

    2002-01-01

    Micromachined Fabry-Perot tunable filters with a large clear aperture (12.5 to 40 mm) are being developed as an optical component for wide-field imaging 1:1 spectroscopy. This program applies silicon micromachining fabrication techniques to miniaturize Fabry-Perot filters for astronomical science instruments. The filter assembly consists of a stationary etalon plate mated to a plate in which the etalon is free to move along the optical axis on silicon springs attached to a stiff silicon support ring. The moving etalon is actuated electrostatically by electrode pairs on the fixed and moving etalons. To reduce mass, both etalons are fabricated by applying optical coatings to a thin freestanding silicon nitride film held flat in drumhead tension rather than to a thick optical substrate. The design, electro-mechanical modeling, fabrication, and initial results will be discussed. The potential application of the miniature Fabry-Perot filters will be briefly discussed with emphasis on the detection of extra-solar planets.

  19. Development, characterization, and modeling of a tunable filter camera

    NASA Astrophysics Data System (ADS)

    Sartor, Mark Alan

    1999-10-01

    This paper describes the development, characterization, and modeling of a Tunable Filter Camera (TFC). The TFC is a new multispectral instrument with electronically tuned spectral filtering and low-light-level sensitivity. It represents a hybrid between hyperspectral and multispectral imaging spectrometers that incorporates advantages from each, addressing issues such as complexity, cost, lack of sensitivity, and adaptability. These capabilities allow the TFC to be applied to low- altitude video surveillance for real-time spectral and spatial target detection and image exploitation. Described herein are the theory and principles of operation for the TFC, which includes a liquid crystal tunable filter, an intensified CCD, and a custom apochromatic lens. The results of proof-of-concept testing, and characterization of two prototype cameras are included, along with a summary of the design analyses for the development of a multiple-channel system. A significant result of this effort was the creation of a system-level model, which was used to facilitate development and predict performance. It includes models for the liquid crystal tunable filter and intensified CCD. Such modeling was necessary in the design of the system and is useful for evaluation of the system in remote-sensing applications. Also presented are characterization data from component testing, which included quantitative results for linearity, signal to noise ratio (SNR), linearity, and radiometric response. These data were used to help refine and validate the model. For a pre-defined source, the spatial and spectral response, and the noise of the camera, system can now be predicted. The innovation that sets this development apart is the fact that this instrument has been designed for integrated, multi-channel operation for the express purpose of real-time detection/identification in low- light-level conditions. Many of the requirements for the TFC were derived from this mission. In order to provide

  20. Flexibly tunable multichannel filter and bandpass filter based on long-period fiber gratings

    NASA Astrophysics Data System (ADS)

    Han, Young-Geun; Hyuck Kim, Sang; Lee, Sang Bae

    2004-05-01

    The voltage-controllable multichannel filter based on multiply cascaded long-period fiber gratings with a divided coil heater will be proposed and experimentally demonstrated. It has several advantages of the large tuning range in both C- and L-band, multichannel operation, multiwavelength electivity, and bandwidth controllability. The tunable bandpass filter based on long-period fiber gratings ith the broad bandwidth over 6.5 nm, large tuning range over 30 nm, and excellent side mode suppression more than 40 dB will be also discussed.

  1. Fully-tunable microwave photonic filter with complex coefficients using tunable delay lines based on frequency-time conversions.

    PubMed

    Mokhtari, Arash; Preußler, Stefan; Jamshidi, Kambiz; Akbari, Mahmood; Schneider, Thomas

    2012-09-24

    A fully electrically tunable microwave photonic filter is realized by the implementation of delay lines based on frequency-time conversion. The frequency response and free spectral range (FSR) of the filter can be engineered by a simple electrical tuning of the delay lines. The method has the capability of being integrated on a silicon photonic platform. In the experiment, a 2-tap tunable microwave photonic filter with a 3-dB bandwidth of 2.55 GHz, a FSR of 4.016 GHz, a FSR maximum tuning range from -354 MHz to 354 MHz and a full FSR translation range is achieved. PMID:23037423

  2. Materials for imaging acousto-optic tunable filters

    NASA Astrophysics Data System (ADS)

    Gupta, Neelam

    2014-05-01

    Research and development of robust compact hyperspectral imagers that can acquire both spectral and spatial features from a scene of interest is of utmost importance for standoff detection of targets as well as chemical and biological agents and backgrounds. Hyperspectral imagers can acquire images with a large number of narrow spectral bands and take advantage of the characteristic spectral signatures of different materials making up the scene. At the Army Research Laboratory (ARL), we are developing hyperspectral imagers based on acousto-optic tunable filters (AOTFs) that can provide adaptive no-moving-parts imagers from the ultraviolet (UV) to the long wave infrared (LWIR) to acquire a two-dimensional spectral image and build up a two-dimensional image cube as a function of time instead of using traditional grating or prism based approach that requires relative motion between sensor and scene. Here, we will review the development of different imaging AOTFs operating from the UV to the LWIR based on a variety of birefringent materials and include the spectral imaging carried out with these filters including both with single and double piezoelectric transducers. We will also include the theoretical background needed to carry out the filter design and discuss development of mercurous halide crystals that can be used to develop AOTFs operating over a wide spectral region from the visible to the LWIR.

  3. Tunable thin film filters for intelligent WDM networks

    NASA Astrophysics Data System (ADS)

    Cahill, Michael; Bartolini, Glenn; Lourie, Mark; Domash, Lawrence

    2006-08-01

    Optical transmission systems have evolved rapidly in recent years with the emergence of new technologies for gain management, wavelength multiplexing, tunability, and switching. WDM networks are increasingly expected to be agile, flexible, and reconfigurable which in turn has led to a need for monitoring to be more widely distributed within the network. Automation of many actions performed on these networks, such as channel provisioning and power balancing, can only be realized by the addition of optical channel monitors (OCMs). These devices provide information about the optical transmission system including the number of optical channels, channel identification, wavelength, power, and in some cases optical signal-to-noise ratio (OSNR). Until recently OCMs were costly and bulky and thus the number of OCMs used in optical networks was often kept to a minimum. We describe a family of tunable thin film filters which have greatly reduced the cost and physical footprint of channel monitors, making possible 'monitoring everywhere' for intelligent optical networks which can serve long haul, metro and access requirements from a single technology platform. As examples of specific applications we discuss network issues such as auto provisioning, wavelength collision avoidance, power balancing, OSNR balancing, gain equalization, alien wavelength recognition, interoperability, and other requirements assigned to the emerging concept of an Optical Control Plane.

  4. Display system employing acousto-optic tunable filter

    NASA Technical Reports Server (NTRS)

    Lambert, James L. (Inventor)

    1995-01-01

    An acousto-optic tunable filter (AOTF) is employed to generate a display by driving the AOTF with a RF electrical signal comprising modulated red, green, and blue video scan line signals and scanning the AOTF with a linearly polarized, pulsed light beam, resulting in encoding of color video columns (scan lines) of an input video image into vertical columns of the AOTF output beam. The AOTF is illuminated periodically as each acoustically-encoded scan line fills the cell aperture of the AOTF. A polarizing beam splitter removes the unused first order beam component of the AOTF output and, if desired, overlays a real world scene on the output plane. Resolutions as high as 30,000 lines are possible, providing holographic display capability.

  5. Display system employing acousto-optic tunable filter

    NASA Technical Reports Server (NTRS)

    Lambert, James L. (Inventor)

    1993-01-01

    An acousto-optic tunable filter (AOTF) is employed to generate a display by driving the AOTF with a RF electrical signal comprising modulated red, green, and blue video scan line signals and scanning the AOTF with a linearly polarized, pulsed light beam, resulting in encoding of color video columns (scan lines) of an input video image into vertical columns of the AOTF output beam. The AOTF is illuminated periodically as each acoustically-encoded scan line fills the cell aperture of the AOTF. A polarizing beam splitter removes the unused first order beam component of the AOTF output and, if desired, overlays a real world scene on the output plane. Resolutions as high as 30,000 lines are possible, providing holographic display capability.

  6. Optically tunable acoustic wave band-pass filter

    SciTech Connect

    Swinteck, N.; Lucas, P.; Deymier, P. A.

    2014-12-15

    The acoustic properties of a hybrid composite that exhibits both photonic and phononic behavior are investigated numerically with finite-element and finite-difference time-domain simulations. The structure is constituted of a periodic array of photonic resonant cavities embedded in a background superlattice. The resonant cavities contain a photo-elastic chalcogenide glass that undergoes atomic-scale structural reorganization when irradiated with light having energy close to its band-gap. Photo-excitation of the chalcogenide glass changes its elastic properties and, consequently, augments the acoustic transmission spectrum of the composite. By modulating the intensity of light irradiating the hybrid photonic/phononic structure, the position and spectral width of phonon passing-bands can be controlled. This demonstration offers the technological platform for optically-tunable acoustic wave band-pass filters.

  7. Lumped-element tunable absorptive bandstop filter and its applications

    NASA Astrophysics Data System (ADS)

    Kim, Byung Guk

    To avoid the cost, large size, and complexity of going off-chip between individually packaged components, it is desirable to integrate as many components as possible. For on-chip passive filter design, size constraints and the quality factor limit the amount of attenuation that can be achieved. This work demonstrates the use of absorptive bandstop filters which gives anomalously deep notches for a given Q-factor. A lumped-element-only topology enables a realization on a chip for the first time. For reconfigurable RF front-ends, a frequency-agile design is newly developed with Q-tunable resonators because an absorptive bandstop filter must balance both intrinsic Q of the resonators and the resonant frequency of the filter. Despite using small-size, low-Q resonators in the bandstop filter design, a large stopband attenuation with a capability of frequency tuning is achieved with potential to suppress potential interference or an image frequency signal. Higher-order absorptive bandstop filters which give higher selectivity are also demonstrated. The sensing of the unused bands is a pre-requisite and important function so that the cognitive radio system can track and use available frequencies. When the ultra-wideband ADC is utilized for sensing to find the unused bands or read the spectrum availability, both the high power interferences and small power signals are the signals we are interested, but the wideband ADC has a limited dynamic range. Since we have the signals with various frequencies and power levels, it is required to have something that can give different gains at different frequencies. This work proposes a frequency equalizer which gives selective attenuation at desired different frequencies, and absorptive bandstop filter with variable attenuation is proposed in this work. For a wide-band receiver or application, it is not typical for AGC to control different gain or attenuation levels at different frequencies. Using frequency selective attenuation, it is

  8. 47 CFR 80.1159 - Narrow-band direct-printing (NB-DP).

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Narrow-band direct-printing (NB-DP). 80.1159... Narrow-band direct-printing (NB-DP). NB-DP is a form of telegraphy for the transmission and receipt of direct printing public correspondence. Ships must use NB-DP techniques only with authorized public...

  9. 47 CFR 80.1159 - Narrow-band direct-printing (NB-DP).

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Narrow-band direct-printing (NB-DP). 80.1159... Narrow-band direct-printing (NB-DP). NB-DP is a form of telegraphy for the transmission and receipt of direct printing public correspondence. Ships must use NB-DP techniques only with authorized public...

  10. 47 CFR 80.1159 - Narrow-band direct-printing (NB-DP).

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Narrow-band direct-printing (NB-DP). 80.1159... Narrow-band direct-printing (NB-DP). NB-DP is a form of telegraphy for the transmission and receipt of direct printing public correspondence. Ships must use NB-DP techniques only with authorized public...

  11. 47 CFR 80.1159 - Narrow-band direct-printing (NB-DP).

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Narrow-band direct-printing (NB-DP). 80.1159... Narrow-band direct-printing (NB-DP). NB-DP is a form of telegraphy for the transmission and receipt of direct printing public correspondence. Ships must use NB-DP techniques only with authorized public...

  12. 47 CFR 80.1159 - Narrow-band direct-printing (NB-DP).

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Narrow-band direct-printing (NB-DP). 80.1159... Narrow-band direct-printing (NB-DP). NB-DP is a form of telegraphy for the transmission and receipt of direct printing public correspondence. Ships must use NB-DP techniques only with authorized public...

  13. Narrow band imaging and long slit spectroscopy of UGC 5101

    NASA Technical Reports Server (NTRS)

    Stanga, R. M.; Mannucci, F.; Rodriguezespinosa, J. M.

    1993-01-01

    UGC 5101 (z = 0.04; D is approximately equal to 240 Mpc) is one of the so called Ultraluminous IRAS sources. Two important properties of the members of this group are their L(sub IR) is greater than or equal to 10(exp 12) solar luminosity, and their space density in the universe up to z is less than 0.1 is equal or even larger than the space density of the quasars. Further noteworthy features of the Ultraluminous IRAS sources are their being morphologically peculiar and the fact that they all seem to host active nuclei in their center. We have observed UGC 5101 in an effort to study the interplay between the gas ionized by the central active nucleus and that gas ionized by other processes which may hold important clues to the understanding of the entire picture of this object. In particular these other ionizing processes could well be massive stars formed recently after the galactic encounter and shocks possibly also related to the galaxy collision. The data that we discuss were obtained between Dec. 1989 and Jan. 1992 with the WHT 4.2 m telescope using the two-arm spectrograph ISIS. Several spectral frames were obtained at three different position angles: PA 84--along the tail of the galaxy; PA 32--along the dust lane; and PA 110. The blue spectra are centered on the H beta line, while the red spectra are centered on the H alpha line. In the configuration we used for the long slit spectra, the spectral scale was 0.74 A per pixel, and the spatial scale was .37 arcsec per pixel; we also observed the H alpha region with a spectral scale of .37 A per pixel, at position angle 84. The narrow band images were obtained at the auxiliary port of ISIS, with a scale of .2 arcsec per pixel, and were centered at the H alpha wavelength, and on the adjacent continuum. The H alpha images and the spectra support the following model. UGC 5101 hosts an active nucleus; the NLR extends up to about 1.5 kpc and shows a complex velocity field, superimposed on the rotation curve of the

  14. PHIRST light: a liquid crystal tunable filter hyperspectral sensor

    NASA Astrophysics Data System (ADS)

    Stevenson, Brian P.; Kendall, William B.; Stellman, Christopher M.; Olchowski, Frederick M.

    2003-09-01

    PHIRST Light is a visible and near-infrared (VNIR) hyperspectral imaging sensor that has been assembled at the Naval Research Laboratory (NRL) using off-the-shelf components. It consists of a Dalsa 1M60 camera mated to a CRI VariSpec liquid crystal tunable filter (LCTF) and a conventional 75mm Pentax lens. This system can be thought of as the modern equivalent of a filter-wheel sensor. Historically, the problem with such sensors has been that images for different wavelengths are collected at different times. This causes spectral correlation problems when the camera is not perfectly still during the collection time for all bands (such as when it is deployed on an airborne platform). However, the PHIRST Light sensor is hard mounted in a Twin Otter aircraft, and is mated to a TrueTime event capture board, which records the precise GPS time of each image frame. Combining this information with the output of a CMIGITS INS/GPS unit permits precise coregistration of images from multiple wavelengths, and allows the formation of a conventional hyperspectral image cube. In this paper we present an overview of the sensor and its deployment, describe the processing steps required to produce coregistered hyperspectral cubes, and show detection results for targets viewed during the Aberdeen Collection Experiment (ACE).

  15. Transmission type tunable wavelength filters based on polymer waveguide Bragg reflectors

    NASA Astrophysics Data System (ADS)

    Park, Su-Hyun; Seo, Jun-Kyu; Park, Joonoh; Lee, Hak-Kyu; Shin, Jin-Soo; Oh, Min-Cheol

    2016-03-01

    In WDM communication systems, a compact low-cost tunable wavelength filter is highly demanded. Polymeric Bragg reflector devices are suitable for this purpose because the large thermo-optic effect of the polymer enables widely tunable wavelength filters with simple device structure. To direct the filtered signal in the forward direction rather than the backward direction, a waveguide mirror device is integrated. A compact package was then achieved by attaching a fiber-connecting receptacle and a high-speed PD on each side of the chip. The tunable filter exhibited a tuning range of 14 nm, a 3-dB bandwidth of 0.45 nm, and a 15-dB bandwidth of 1.54 nm. The device exhibited a low polarization dependence of 0.08 nm, which is the first demonstration in polymeric tunable filters.

  16. Probing potassium in the atmosphere of HD 80606b with tunable filter transit spectrophotometry from the Gran Telescopio Canarias

    NASA Astrophysics Data System (ADS)

    Colón, Knicole D.; Ford, Eric B.; Redfield, Seth; Fortney, Jonathan J.; Shabram, Megan; Deeg, Hans J.; Mahadevan, Suvrath

    2012-01-01

    We report observations of HD 80606 using the 10.4-m Gran Telescopio Canarias and the Optical System for Imaging and low Resolution Integrated Spectroscopy (OSIRIS) tunable filter imager. We acquired very high precision, narrow-band photometry in four bandpasses around the K I absorption feature during the 2010 January transit of HD 80606b and during out-of-transit observations conducted in 2010 January and April. We obtained differential photometric precisions of ˜2.08 × 10-4 for the in-transit flux ratio measured at 769.91 nm, which probes the K I line core. We find no significant difference in the in-transit flux ratio between observations at 768.76 and 769.91 nm. Yet, we find a difference of ˜8.09 ± 2.88 × 10-4 between these observations and observations at a longer wavelength that probes the K I wing (777.36 nm). While the presence of red noise in the transit data has a non-negligible effect on the uncertainties in the flux ratio, the 777.36-769.91 nm colour during transit shows no effects from red noise and also indicates a significant colour change, with a mean value of ˜8.99 ± 0.62 × 10-4. This large change in the colour is equivalent to a ˜4.2 per cent change in the apparent planetary radius with wavelength, which is much larger than the atmospheric scaleheight. This implies the observations probed the atmosphere at very low pressures as well as a dramatic change in the pressure at which the slant optical depth reaches unity between ˜770 and 777 nm. We hypothesize that the excess absorption may be due to K I in a high-speed wind being driven from the exoplanet's exosphere. We discuss the viability of this and alternative interpretations, including stellar limb darkening, star-spots and effects from Earth's atmosphere. We strongly encourage follow-up observations of HD 80606b to confirm the signal measured here. Finally, we discuss the future prospects for exoplanet characterization using tunable filter spectrophotometry.

  17. Tunable microwave photonic notch filter based on sliced broadband optical source.

    PubMed

    Yu, Yang; Li, Shangyuan; Zheng, Xiaoping; Zhang, Hanyi; Zhou, Bingkun

    2015-09-21

    A microwave photonic filter is demonstrated with both tunable center frequency and bandwidth. This filter is switchable from all-pass, bandpass to notch filter, and the notch filter is a result of the subtraction of a bandpass filter from an all-pass filter based on a balanced photodetector. The all-pass filter is achieved based on a single wavelength radio over fiber link, and the bandpass one is acquired by using the spectrum-sliced broadband optical source. Theoretical analysis and experimental results show that both the center frequency and the bandwidth of the notch filter can be widely tuned. PMID:26406636

  18. Jovian narrow-band as generator of the Jovian millisecond radio bursts

    NASA Astrophysics Data System (ADS)

    Boudjada, M. Y.; Galopeau, P. H. M.; Rucker, H. O.; Lecacheux, A.

    2000-11-01

    We report on the narrow-band emissions observed in the dynamic spectra of the Jovian decametric radio emissions. Such narrow-band emissions are infrequent phenomena and are related to the Jovian millisecond radio bursts (S-bursts). From the Riihimaa catalogue (Riihimaa 1991) we select narrow-band events observed in Oulu (Finland) with an acousto-optic spectrograph (AOS) with a high time resolution of about 7 ms. The AOS receiver gives the possibility to study the relationship between the S-bursts and the Jovian narrow-band emissions. For this we use the Riihimaa classification which shows sketches of millisecond radio bursts as they appear on the dynamic spectra and allows to distinguish one S-burst from another. The analysis of the temporal evolution of the Jovian narrow-band leads to a new interpretation of the Riihimaa structures. We show that each individual structure could be decomposed in one, two or three components and related to the narrow-band. It appears that the temporal evolution of the narrow-band involves the presence of fine structures, i.e. S-bursts, with a short time duration of about few tens of milliseconds. The individual S-burst duration and the short time scale of the gap in the narrow-band account for a mechanism totally intrinsic to the radio source. Taking into consideration our new results, we show that two models, the feedback model (Calvert 1982) and filamentary model (Louarn 1997) could explain part but not the global observed features of the narrow-band. According to the previous models the drift rate of the individual S-bursts seems to associate the combined effect of the source width with the refractive index or the geometry of the source relatively to the observer.

  19. Recent advance in application of acousto-optic tunable filters

    NASA Astrophysics Data System (ADS)

    Khansuvarov, Ruslan A.; Shakin, Oleg V.; Vaganov, Mikhail A.; Zhdanov, Arseniy Y.; Prokashev, Vadim N.

    2014-09-01

    This paper aims to inform those interested in the scientific work of a large group of scientists: workers of the Department of Electronics and Optical communications of St. Petersburg State University of Aerospace Instrumentation in collaboration with workers of the Department of Quantum Electronics of St. Petersburg State Technical University in the area of researches and development of acousto-optic tunable filters (AOTF). Paper discusses the important features of the AOTF structure and their parameters that affect its work, such as: spectral range of optical radiation, spectral resolution, active aperture of the optical radiation, optical transmission of the working spectral range, optical radiation polarization (linear, circular or arbitrary) , diffraction efficiency, contrast, distortion of the optical radiation's front, frequency range of elastic waves, switching time, maximum electric control power, impedance. Also the AOTF using is considered: AOTF's implications for control of laser radiation, AOTF's application to determine the counterfeit money. The last part of the report focuses on materials that act as antireflection thin films. Spectral characteristics of "clean" and enlightened substrates of ZnSe and Ge are shown. As seen from the examples in the report, antireflection thin films increase transmittance of optical elements.

  20. Double-filtering method based on two acousto-optic tunable filters for hyperspectral imaging application.

    PubMed

    Wang, Pengchong; Zhang, Zhonghua

    2016-05-01

    A hyperspectral imaging system was demonstrated based on two acousto-optic tunable filters (AOTFs). Efficient regulation of the incoherent beam was executed by means of the wide-angular regime of Bragg diffraction in the birefringent materials. A double-filtering process was achieved when these two AOTFs operated with a central wavelength difference. In comparison with the single-filtering method, the spectral bandwidth was greatly compressed, giving an increment of 42.02% in spectral resolution at the wavelength of 651.62 nm. Experimental results and theoretical calculations are basically identical. Furthermore, the sidelobe was found to be suppressed by the double-filtering process with the first order maximum decreased from -9.25 dB to -22.35 dB. The results indicated high spectral resolution and high spectral purity were obtained simultaneously from this method. The basic spectral resolution performance was examined with a didymium glass by this configuration. We present our experimental methods and the detailed results obtained. PMID:27137600

  1. Narrow band photometry of comet Kohoutek. [made at the Cassegrain focus of a 36-inch astronomical telescope

    NASA Technical Reports Server (NTRS)

    Brown, L. W.

    1976-01-01

    Photometric observations of the coma of comet Kohoutek were made at the Cassegrain focus of a 36-inch telescope. The observations consisted of one wide (visual, 5454 A) and six narrow (CN, 3879 A; C3, 4057 A; C2, 4732 A, 5165 A, 5634 A; continuum, 5200 A) band interference filters. In addition each filter was used with six diaphragms. Good quality data were obtained on 13 days between November 1973 and February 1974. A small flare was observed on 1 December for all filters, a CN flare on 13 January, and a visual flare on 28 January. The data were reduced to absolute narrow band magnitudes of the comet for the 13 days. The radial dependence of the surface brightness was derived from the set of diaphragms and future work will be directed toward using these results for modeling density distributions for the coma.

  2. Single passband microwave photonic filter with wideband tunability and adjustable bandwidth.

    PubMed

    Chen, Tong; Yi, Xiaoke; Li, Liwei; Minasian, Robert

    2012-11-15

    A new and simple structure for a single passband microwave photonic filter is presented. It is based on using an electro-optical phase modulator and a tunable optical filter and only requires a single wavelength source and a single photodetector. Experimental results are presented that demonstrate a single passband, flat-top radio-frequency filter response without free spectral range limitations, along with the capability of tuning the center frequency and filter bandwidth independently. PMID:23164884

  3. Elimination of threshold-induced distortion in the power spectrum of narrow-band laser speckle

    NASA Astrophysics Data System (ADS)

    Ducharme, Alfred D.; Boreman, Glenn D.; Yang, Sidney S.

    1995-10-01

    The distortion in the power spectrum of narrow-band laser speckle that results from irradiance thresholding is quantified. A method for compensation of this distortion is presented. An optimal threshold level is presented that simplifies the compensation method.

  4. Further improvements in program to calculate electronic properties of narrow band gap materials

    NASA Technical Reports Server (NTRS)

    Patterson, James D.

    1991-01-01

    Research into the properties of narrow band gap materials during the period 15 Jun. to 15 Dec. 1991 is discussed. Abstracts and bibliographies from papers presented during this period are reported. Graphs are provided.

  5. Ultrafast optical control of group delay of narrow-band terahertz waves

    PubMed Central

    Miyamaru, Fumiaki; Morita, Hiroki; Nishiyama, Yohei; Nishida, Tsubasa; Nakanishi, Toshihiro; Kitano, Masao; Takeda, Mitsuo W.

    2014-01-01

    We experimentally demonstrate control over the group delay of narrow-band (quasi continuous wave) terahertz (THz) pulses with constant amplitude based on optical switching of a metasurface characteristic. The near-field coupling between resonant modes of a complementary split ring resonator pair and a rectangular slit show an electromagnetically induced transparency-like (EIT-like) spectral shape in the reflection spectrum of a metasurface. This coupling induces group delay of a narrow-band THz pulse around the resonant frequency of the EIT-like spectrum. By irradiating the metasurface with an optical excitation pulse, the metasurface becomes mirror-like and thus the incident narrow-band THz pulse is reflected without a delay. Remarkably, if we select the appropriate excitation power, only the group delay of the narrow-band THz pulse can be switched while the amplitude is maintained before and after optical excitation. PMID:24614514

  6. Narrow-band 5 kHz hiss observed in the vicinity of the plasmapause

    NASA Astrophysics Data System (ADS)

    Ondoh, T.; Nakamura, Y.; Watanabe, S.; Murakami, T.

    1981-01-01

    Latitudinal distributions of narrow-band 5 kHz hisses have been statistically obtained by using VLF electric field data received from the ISIS-1 and -2 at Syowa station, Antarctica and Kashima station, Japan, in order to study an origin of the narrow-band 5 kHz hisses which are often observed on the ground in mid- and low-latitudes. The result shows that the narrow-band 5 kHz hiss occurs most frequently at geomagnetically invariant latitudes from 55 to 63 deg, which are roughly the plasmapause latitudes at various geomagnetic activities, both in the Northern and Southern Hemispheres. The narrow-band 5 kHz hiss seems to be generated by the cyclotron instabilities of several keV to a few ten keV electrons for the most feasible electron density of 10 to 1000 per cu cm in the vicinity of the equatorial plasmapause.

  7. Ultra-narrow band perfect absorbers based on plasmonic analog of electromagnetically induced absorption.

    PubMed

    He, Jinna; Ding, Pei; Wang, Junqiao; Fan, Chunzhen; Liang, Erjun

    2015-03-01

    A novel plasmonic metamaterial consisting of the solid (bar) and the inverse (slot) compound metallic nanostructure for electromagnetically induced absorption (EIA) is proposed in this paper, which is demonstrated to achieve an ultra-narrow absorption peak with the linewidth less than 8 nm and the absorptivity exceeding 97% at optical frequencies. This is attributed to the plasmonic EIA resonance arising from the efficient coupling between the magnetic response of the slot (dark mode) and the electric resonance of the bar (bright mode). To the best of our knowledge, this is the first time that the plasmonic EIA is used to realize the narrow-band perfect absorbers. The underlying physics are revealed by applying the two-coupled-oscillator model. The near-perfect-absorption resonance also causes an enhancement of about 50 times in H-field and about 130 times in E-field within the slots. Such absorber possesses potential for applications in filter, thermal emitter, surface enhanced Raman scattering, sensing and nonlinear optics. PMID:25836832

  8. Visualization of mucosal vasculature with narrow band imaging: a theoretical study

    NASA Astrophysics Data System (ADS)

    Wang, Quanzeng; Le, Du; Ramella-Roman, Jessica; Pfefer, Joshua

    2012-03-01

    Narrow band imaging (NBI) is a spectrally-selective reflectance imaging technique that is used as an adjunctive approach to endoscopic detection of mucosal abnormalities such as neoplastic lesions. While numerous clinical studies in tissue sites such as the esophagus, oral cavity and lung indicate the efficacy of this approach, it is not well theoretically understood. In this study, we performed Monte Carlo simulations to elucidate the factors that affect NBI device performance. The model geometry involved a two-layer turbid medium based on mucosal tissue optical properties and embedded cylindrical, blood-filled vessels at varying diameters and depths. Specifically, we studied the effect of bandpass filters (415+/-15 nm, 540+/-10 nm versus white light), blood vessel diameter (20-400 μm) and depth (30 - 450 μm), wavelength, and bandwidth on vessel contrast. Our results provide a quantitative evaluation of the two mechanisms that are commonly believed to be the primary components of NBI: (i) the increased contrast provided by high hemoglobin absorption and (ii) increase in the penetration depth produced by the decrease in scattering with increasing wavelength. Our MC model can provide novel, quantitative insight into NBI, may lead to improvements in its performance.

  9. Narrow band pulses as stimuli in an auditory brain stem recording study with a harbor porpoise

    NASA Astrophysics Data System (ADS)

    Beedholm, Kristian; Miller, Lee A.

    2005-04-01

    We have studied several aspects of hearing by a harbor porpoise using the ABR method with pulsed stimuli. Experiments were conducted on a male porpoise in collaboration with Fjord and Baelt, Kerteminde, Denmark. The animal had suction cups containing silver electrodes placed near the blowhole and near the dorsal fin. When fitted with the electrodes he moved to an underwater listening post where his outgoing sonar signal could be used to trigger a phantom echo. EEG signals were amplified differentially and averaged over a variable number of presentations depending on trial duration and experiment. For studying the frequency/intensity response, narrow band pulsed stimuli were generated and presented in several ways. One way was to use the impulse response of a B&K 1/3 octave filter bank (set to 80, 100, 125, or 160 kHz) as a stimulus. This stimulus was presented in both a passive hearing task, when a signal generator triggered the echo, and in an active experiment, where the echo was time locked to the animals emitted signal. Our results show the best response at 125 kHz and indicate a slight, but significantly higher response in the active mode. The latter has a methodological explanation. [Work supported by ONR.

  10. All-optical tunable microwave interference suppression filter based on SOA

    NASA Astrophysics Data System (ADS)

    Xu, Enming; Zhang, Xinliang; Zhou, Lina; Huang, Dexiu

    2008-12-01

    An all-optical filter structure for interference suppression of microwave signals is presented. The filter is based on a recirculating delay line (RDL) loop consisting of a semiconductor optical amplifier (SOA) followed by a tunable narrowband optical filter, and a fiber Bragg grating connected after the RDL loop. Negative tap is generated in wavelength conversion process based on cross-gain modulation of amplified spontaneous emission spectrum of the SOA. A narrow passband filter with negative coefficients and a broadband all-pass filter are synthesized to achieve a narrow notch filter with flat passband which can excise interference with minimal impact on the wanted signal over a wide microwave range. Experimental results show that measured and theoretical frequency responses agree well and the filter is tunable.

  11. Narrow-band photometry of Beta Lyrae in 1971

    NASA Astrophysics Data System (ADS)

    Scarfe, C. D.

    1980-01-01

    Observations of Beta Lyrae (with HR 6997 as the principal companion star) are presented, principally of certain strong lines and neighboring continuum regions obtained through interference filters of bandwidths ranging from 27.0 to 33.7 A. Light curves in the 3 blue and 3 red bands are shown, and color indices and emission intensity indices are tabulated. Moreover, a photometric index of emission line strength, analogous to the spectroscopic index of Batten and Sahade (1973), is derived. It is suggested that the H alpha emission comes from a larger region around the binary star than does the helium emission and is asymmetrical, being weakest near quadrature when the primary star is approaching earth. The helium emission, by contrast, is more symmetrical, and varies with binary phase by a larger fractional amount.

  12. High-efficiency microwave photonic harmonic down-conversion with tunable and reconfigurable filtering.

    PubMed

    Liao, Jinxin; Zheng, Xiaoping; Li, Shangyuan; Zhang, Hanyi; Zhou, Bingkun

    2014-12-01

    A new optical-frequency comb-based microwave photonic harmonic down-convertor with tunable and reconfigurable filtering is proposed and experimentally demonstrated. The coherent evenly spaced optical carriers offer harmonic down-conversion for ultrahigh radio frequency signals with low-frequency local oscillator, and construct a tunable and reconfigurable bandpass filter for the intermediate-frequency (IF) signal combined with dispersion. This implementation features high conversion efficiency. Experimental results show the filtered output IF signal has a clean spectrum with high quality. Measured conversion loss is 8.3 dB without extra electrical amplification. PMID:25490622

  13. Low-power microelectromechanically tunable silicon photonic ring resonator add-drop filter.

    PubMed

    Errando-Herranz, Carlos; Niklaus, Frank; Stemme, Göran; Gylfason, Kristinn B

    2015-08-01

    We experimentally demonstrate a microelectromechanically (MEMS) tunable photonic ring resonator add-drop filter, fabricated in a simple silicon-on-insulator (SOI) based process. The device uses electrostatic parallel plate actuation to perturb the evanescent field of a silicon waveguide, and achieves a 530 pm resonance wavelength tuning, i.e., more than a fourfold improvement compared to previous MEMS tunable ring resonator add-drop filters. Moreover, our device has a static power consumption below 100 nW, and a tuning rate of -62  pm/V, i.e., the highest reported rate for electrostatic tuning of ring resonator add-drop filters. PMID:26258356

  14. Tunable orbital angular momentum mode filter based on optical geometric transformation.

    PubMed

    Huang, Hao; Ren, Yongxiong; Xie, Guodong; Yan, Yan; Yue, Yang; Ahmed, Nisar; Lavery, Martin P J; Padgett, Miles J; Dolinar, Sam; Tur, Moshe; Willner, Alan E

    2014-03-15

    We present a tunable mode filter for spatially multiplexed laser beams carrying orbital angular momentum (OAM). The filter comprises an optical geometric transformation-based OAM mode sorter and a spatial light modulator (SLM). The programmable SLM can selectively control the passing/blocking of each input OAM beam. We experimentally demonstrate tunable filtering of one or multiple OAM modes from four multiplexed input OAM modes with vortex charge of ℓ=-9, -4, +4, and +9. The measured output power suppression ratio of the propagated modes to the blocked modes exceeds 14.5 dB. PMID:24690870

  15. Assessing the temperature dependence of narrow-band Raman water vapor lidar measurements: a practical approach.

    PubMed

    Whiteman, David N; Venable, Demetrius D; Walker, Monique; Cadirola, Martin; Sakai, Tetsu; Veselovskii, Igor

    2013-08-01

    Narrow-band detection of the Raman water vapor spectrum using the lidar technique introduces a concern over the temperature dependence of the Raman spectrum. Various groups have addressed this issue either by trying to minimize the temperature dependence to the point where it can be ignored or by correcting for whatever degree of temperature dependence exists. The traditional technique for performing either of these entails accurately measuring both the laser output wavelength and the water vapor spectral passband with combined uncertainty of approximately 0.01 nm. However, uncertainty in interference filter center wavelengths and laser output wavelengths can be this large or larger. These combined uncertainties translate into uncertainties in the magnitude of the temperature dependence of the Raman lidar water vapor measurement of 3% or more. We present here an alternate approach for accurately determining the temperature dependence of the Raman lidar water vapor measurement. This alternate approach entails acquiring sequential atmospheric profiles using the lidar while scanning the channel passband across portions of the Raman water vapor Q-branch. This scanning is accomplished either by tilt-tuning an interference filter or by scanning the output of a spectrometer. Through this process a peak in the transmitted intensity can be discerned in a manner that defines the spectral location of the channel passband with respect to the laser output wavelength to much higher accuracy than that achieved with standard laboratory techniques. Given the peak of the water vapor signal intensity curve, determined using the techniques described here, and an approximate knowledge of atmospheric temperature, the temperature dependence of a given Raman lidar profile can be determined with accuracy of 0.5% or better. A Mathematica notebook that demonstrates the calculations used here is available from the lead author. PMID:23913054

  16. Assessing the Temperature Dependence of Narrow-Band Raman Water Vapor Lidar Measurements: A Practical Approach

    NASA Technical Reports Server (NTRS)

    Whiteman, David N.; Venable, Demetrius D.; Walker, Monique; Cardirola, Martin; Sakai, Tetsu; Veselovskii, Igor

    2013-01-01

    Narrow-band detection of the Raman water vapor spectrum using the lidar technique introduces a concern over the temperature dependence of the Raman spectrum. Various groups have addressed this issue either by trying to minimize the temperature dependence to the point where it can be ignored or by correcting for whatever degree of temperature dependence exists. The traditional technique for performing either of these entails accurately measuring both the laser output wavelength and the water vapor spectral passband with combined uncertainty of approximately 0.01 nm. However, uncertainty in interference filter center wavelengths and laser output wavelengths can be this large or larger. These combined uncertainties translate into uncertainties in the magnitude of the temperature dependence of the Raman lidar water vapor measurement of 3% or more. We present here an alternate approach for accurately determining the temperature dependence of the Raman lidar water vapor measurement. This alternate approach entails acquiring sequential atmospheric profiles using the lidar while scanning the channel passband across portions of the Raman water vapor Q-branch. This scanning is accomplished either by tilt-tuning an interference filter or by scanning the output of a spectrometer. Through this process a peak in the transmitted intensity can be discerned in a manner that defines the spectral location of the channel passband with respect to the laser output wavelength to much higher accuracy than that achieved with standard laboratory techniques. Given the peak of the water vapor signal intensity curve, determined using the techniques described here, and an approximate knowledge of atmospheric temperature, the temperature dependence of a given Raman lidar profile can be determined with accuracy of 0.5% or better. A Mathematica notebook that demonstrates the calculations used here is available from the lead author.

  17. Comb-based radiofrequency photonic filters with rapid tunability and high selectivity

    NASA Astrophysics Data System (ADS)

    Supradeepa, V. R.; Long, Christopher M.; Wu, Rui; Ferdous, Fahmida; Hamidi, Ehsan; Leaird, Daniel E.; Weiner, Andrew M.

    2012-03-01

    Photonic technologies have received considerable attention regarding the enhancement of radiofrequency electrical systems, including high-frequency analogue signal transmission, control of phased arrays, analog-to-digital conversion and signal processing. Although the potential of radiofrequency photonics for the implementation of tunable electrical filters over broad radiofrequency bandwidths has been much discussed, the realization of programmable filters with highly selective filter lineshapes and rapid reconfigurability has faced significant challenges. A new approach for radiofrequency photonic filters based on frequency combs offers a potential route to simultaneous high stopband attenuation, fast tunability and bandwidth reconfiguration. In one configuration, tuning of the radiofrequency passband frequency is demonstrated with unprecedented (~40 ns) speed by controlling the optical delay between combs. In a second, fixed filter configuration, cascaded four-wave mixing simultaneously broadens and smoothes the comb spectra, resulting in Gaussian radiofrequency filter lineshapes exhibiting an extremely high (>60 dB) main lobe to sidelobe suppression ratio and (>70 dB) stopband attenuation.

  18. Study on the structure of bridge surface of the micro Fabry-Perot cavity tunable filter

    NASA Astrophysics Data System (ADS)

    Meng, Qinghua; Luo, Huan; Bao, Shiwei; Zhou, Yifan; Chen, Sihai

    2011-02-01

    Micro Fabry-Perot cavity tunable filters are widely applied in the area of Pushbroom Hyperspectral imaging, DWDM optical communication system and self-adaptive optics. With small volume, lower consumption and cost, the Micro Fabry-Perot cavity tunable filter can realize superior response speed, large spectral range, high definition and high reliability. By deposition metal membrane on silicon chip by MEMS technology, the micro Fabry-Perot cavity has been achieved, which is actuated by electrostatic force and can realize the function of an optical filter. In this paper, the micro-bridge structure of the micro Fabry-Perot cavity tunable filter has been studied. Finite element analysis software COMSOL Multiphysics has been adopted to design the structure of the micro-bridge of the micro filter. In order to simulate the working mechanism of the micro Fabry-Perot cavity and study the electrical and mechanical characteristics of the micro tunable filter,the static and dynamic characteriastics are analyzed, such as stress, displacement, transient response, etc. The corresponding parameters of the structure are considered as well by optimizition the filter's sustain structure.

  19. Multifunctional tunable multiwavelength erbium-doped fiber laser based on tunable comb filter and intensity-dependent loss modulation

    NASA Astrophysics Data System (ADS)

    Quan, Mingran; Li, Yuan; Tian, Jiajun; Yao, Yong

    2015-04-01

    A multiwavelength erbium-doped fiber laser based on tunable comb spectral filter and intensity-dependent loss modulation is proposed and experimentally demonstrated. The laser allows fine and multifunctional tunable operations of channel-spacing, peak-location, spectral-range, and wavelength-number. More specifically, channel-spacing switch from 0.4 nm to 0.2 nm and peak-location adjustment within half of free spectrum range are obtained via controlling the tunable comb filter. The wavelength-number and the spectral-range of the lasing lines can be accurately controlled by intensity-dependent loss modulation in the laser cavity, enabled by a power-symmetric nonlinear optical loop mirror. In addition, fine control over the wavelength-number at fixed spectral-range is realized by simply adjusting the pump power. More important, the tunable operation process for every type of specific parameter is individual, without influences for other output parameters. Such features of this fiber laser make it useful and convenient for the practical application.

  20. Improved tunable external filter for Langmuir probe measurement at low density plasmas

    NASA Astrophysics Data System (ADS)

    Chang, Yoon-Min; Lee, Hyo-Chang; Jeon, Sang-Bum; Kim, Dong-Hwan; Kim, Ju-Ho; Chung, Chin-Wook; Department of Electrical Engineering Team; Department of Nanoscale Semiconductor Engineering Team

    2015-09-01

    Measurement of the electron energy probability function (EEPF) at low density plasma, especially in molecular gas discharge, is difficult due to large RF fluctuation. To overcome the problem, an improved tunable external filter was developed. In contrast to an internal filter, the external filter can tune the resonance frequency of the choke filter. However, conventional external filter has low impedance due to a large stray capacitance between a probe tip and the external filter. To reduce the effect of the stray capacitance, an appropriate inductor was connected to the probe tip, and the external filter was designed to tune the first and the second harmonic frequencies independently. Using our filter, the EEPFs were measured at low density plasma with various gases, and the results show the improved performance of the filter as compared to the previous studies.

  1. Tunable millimeter-wave filters using a coplanar waveguide and micromachined variable capacitors

    NASA Astrophysics Data System (ADS)

    Park, Jae-Hyoung; Kim, Hong-Teuk; Kwon, Youngwoo; Kim, Yong-Kweon

    2001-11-01

    In this paper, new micromachined tunable bandpass filters for multi-band millimeter-wave telecommunication systems are proposed. Two types of millimeter-wave tunable filters have been fabricated using micromachining technology and the responses of the filters have been measured: one type is a two-pole lumped element filter and the other a two-pole resonator filter. The frequency tunability of the filter has been achieved by changing the gap between a common coplanar waveguide ground plate and a movable cantilever beam connected to the transmission line with a controllable range of 2.5 µm. The deflection of the cantilever beam has been measured with applied dc voltage. With the applied bias voltage from 0 to 50 V, the fabricated filters have shown center frequency shifts of 0.6 GHz (2.3%) at 26.6 GHz and 0.8 GHz (2.5%) at 32 GHz for the lumped element and resonator filters, respectively. The mechanical lifetime of the fabricated gold cantilever structure has been tested by observing the existence of the spring memory phenomenon; there is no memory phenomenon or breakdown until a repeated actuation of 1.6×108 cycles.

  2. Final Report: Tunable Narrow Band Gap Absorbers For Ultra High Efficiency Solar Cells

    SciTech Connect

    Bedair, Salah M.; Hauser, John R.; Elmasry, Nadia; Colter, Peter C.; Bradshaw, G.; Carlin, C. Z.; Samberg, J.; Edmonson, Kenneth

    2012-07-31

    We report on a joint research program between NCSU and Spectrolab to develop an upright multijunction solar cell structure with a potential efficiency exceeding the current record of 41.6% reported by Spectrolab. The record efficiency Ge/GaAs/InGaP triple junction cell structure is handicapped by the fact that the current generated by the Ge cell is much higher than that of both the middle and top cells. We carried out a modification of the record cell structure that will keep the lattice matched condition and allow better matching of the current generated by each cell. We used the concept of strain balanced strained layer superlattices (SLS), inserted in the i-layer, to reduce the bandgap of the middle cell without violating the desirable lattice matched condition. For the middle GaAs cell, we have demonstrated an n-GaAs/i-(InGaAs/GaAsP)/p-GaAs structure, where the InxGa1-xAs/GaAs1-yPy SLS is grown lattice matched to GaAs and with reduced bandgap from 1.43 eV to 1.2 eV, depending upon the values of x and y.

  3. Tunable optical bandpass filter with multiple flat-top bands in nanostructured resonators

    NASA Astrophysics Data System (ADS)

    Xie, Jun; Chen, Yuping; Lu, Wenjie; Chen, Xianfeng

    2011-03-01

    Based on second-order nonlinearity, we present a tunable optical bandpass filter at c-band by introducing a back quasiphase-matching technique with a nanostructured named multiple resonator waveguide. Two injecting forward lights and one backward propagating light interact with difference frequency generation. At that juncture, the transmission of the forward signal can be modulated via changing the forward control power. As a result, a tunable optical bandpass filter with multiple flat-top transmit bands of the forward signal can be formed in the waveguide.

  4. A narrow-band speckle-free light source via random Raman lasing

    NASA Astrophysics Data System (ADS)

    Hokr, Brett H.; Schmidt, Morgan S.; Bixler, Joel N.; Dyer, Phillip N.; Noojin, Gary D.; Redding, Brandon; Thomas, Robert J.; Rockwell, Benjamin A.; Cao, Hui; Yakovlev, Vladislav V.; Scully, Marlan O.

    2016-01-01

    Currently, no light source exists which is both narrowband and speckle free with sufficient brightness for full-field imaging applications. Light-emitting diodes are excellent spatially incoherent sources, but are tens of nanometers broad. Lasers, on the other hand, can produce very narrow-band light, but suffer from high spatial coherence which leads to speckle patterns, which distort the image. Here, we propose the use of random Raman laser emission as a new kind of light source capable of providing short-pulsed narrow-band speckle-free illumination for imaging applications.

  5. Narrow-band impedance of a round metallic pipe with a low conductive thin layer

    NASA Astrophysics Data System (ADS)

    Ivanyan, M.; Grigoryan, A.; Tsakanian, A.; Tsakanov, V.

    2014-02-01

    The new traveling wave structure with a single synchronous mode resonantly excited by the relativistic charge is presented. The structure is composed of a metallic tube with an internally coated low conductive thin layer. It is shown that the impedance of the internally coated metallic tube has a narrow-band single resonance at a high frequency. The analytical presentation of the narrow-band impedance, the wake function, and the frequency of the synchronous mode are obtained. The analytical solutions are compared with exact numerical simulations using the field matching technique.

  6. Polarization-Insensitive Tunable Optical Filters based on Liquid Crystal Polarization Gratings

    NASA Astrophysics Data System (ADS)

    Nicolescu, Elena

    Tunable optical filters are widely used for a variety of applications including spectroscopy, optical communication networks, remote sensing, and biomedical imaging and diagnostics. All of these application areas can greatly benefit from improvements in the key characteristics of the tunable optical filters embedded in them. Some of these key parameters include peak transmittance, bandwidth, tuning range, and transition width. In recent years research efforts have also focused on miniaturizing tunable optical filters into physically small packages for compact portable spectroscopy and hyperspectral imaging applications such as real-time medical diagnostics and defense applications. However, it is important that miniaturization not have a detrimental effect on filter performance. The overarching theme of this dissertation is to explore novel configurations of Polarization Gratings (PGs) as simple, low-cost, polarization-insensitive alternatives to conventional optical filtering technologies for applications including hyperspectral imaging and telecommunications. We approach this goal from several directions with a combination of theory and experimental demonstration leading to, in our opinion, a significant contribution to the field. We present three classes of tunable optical filters, the first of which is an angle-filtering scheme where the stop-band wavelengths are redirected off axis and the passband is transmitted on-axis. This is achieved using a stacked configuration of polarization gratings of various thicknesses. To improve this class of filter, we also introduce a novel optical element, the Bilayer Polarization Grating, exhibiting unique optical properties and demonstrating complex anchoring conditions with high quality. The second class of optical filter is analogous to a Lyot filter, utilizing stacks of static or tunable waveplates sandwiched with polarizing elements. However, we introduce a new configuration using PGs and static waveplates to replace

  7. Tunable Fabry-Perot filter and grating hybrid modulator to improve dispersive spectrometer resolution

    NASA Astrophysics Data System (ADS)

    Fang, Liang; Li, Guojun; Yang, Huan; Zhou, Chongxi

    2016-05-01

    We describe a tunable Fabry-Perot filter and grating hybrid modulator to achieve a higher spectral resolution compared with that produced by a single grating with the same period. In the hybrid modulator, a tunable Fabry-Perot filter is designed with a long cavity to accommodate a multi-order narrowband pre-filter. A grating is then utilized to separate these multi-orders spatially. Scanning the air gap of the tunable Fabry-Perot filter within 1/2 wavelength, the entire spectrogram can be achieved by compositing each group of transmitted multi-orders. Light passes first through the Fabry-Perot cavity and then into the grating. Thus, all of the light is incident on the Fabry-Perot cavity at a given angle, which can reduce the requirement for incident beam alignment and simplify the operation of the hybrid modulator. The structural matching conditions of the tunable Fabry-Perot filter and grating were presented based on the operating law of the hybrid modulator. In terms of the Rayleigh criterion, the practical spectral resolution of the hybrid modulator can be increased by at least twice that of the single grating. Experiments with a neon lamp revealed that the spectral resolution of the hybrid modulator was nearly double that of a single grating.

  8. A Catalog of z=3.1 Lyman Alpha Emitting Galaxies Discovered in Narrow-band Imaging of MUSYC 1030+05

    NASA Astrophysics Data System (ADS)

    Christenson, Holly; Gangolli, Nakul; Raney, Catie Ann; Walker, Jean P.; Gawiser, Eric J.; MUSYC Collaboration

    2016-01-01

    We present a catalog of ~200 Lyman Alpha Emitting galaxies (LAEs) at redshift z=3.1 found in a 5015 Å narrow-band image of the MUSYC 1030+05 field. We reduced raw optical images taken with the MOSAIC II CCD camera at the CTIO 4m telescope with the IRAF MSCRED package. The reduction included the crucial steps of bias subtraction, flat-field correction, cosmic ray and satellite trail rejection, astrometric calibration, tangent plane projection, weighted stacking, and sky background removal. Our initial catalog of sources detected in the narrow-band filter contains ~20,000 sources. We used additional photometric measurements in the MUSYC broad-band filters to identify LAEs via their flux density excess in the narrow-band. This catalog of LAEs will undergo further analysis to characterize how the number density, clustering, colors, and star formation rates of LAEs vary with position and evolve with redshift.We gratefully acknowledge support from NSF grants AST-1055919 & PHY-1263280.

  9. Narrow-Band Spectrophotometry of Comet Hale-Bopp (C/1995 O1) Near Perihelion I.: Photometric Behavior of C2, C3, CN Molecular Bands

    NASA Astrophysics Data System (ADS)

    Sung, Eon-Chang; Kim, Ho-Il; Youn, Jae-Hyuk

    2000-12-01

    We present the results from narrow-band spectrophotometry of Comet Hale-Bopp (C/1995 O1) near perihelion obtained at Sobaeksan Optical Astronomy Observatory 61cm telescope equipped with PM 512 CCD camera (512 x 512, 0.5''/pixel) and narrow-band filter set for the comet on 19 nights from February 21 to May 1, 1997. We discuss molecular emission band morphology and photometric behavior of Comet Hale-Bopp. The morphology of CN band shows more symmetric light distributions than C2 or C3 bands. On other hand, C2 and C3 band have more compact light distributions than CN band. Similar to wide-band image, molecular band morphology shows spiral structures at the core of the comet. The CN surface brightness variation with changing heliocentric distance shows difference from those of C2 and C.3 The brightness, however, of these molecular bands near perihelion shows previously known 7day period light variations.

  10. Correlation of Electric Field and Critical Design Parameters for Ferroelectric Tunable Microwave Filters

    NASA Technical Reports Server (NTRS)

    Subramanyam, Guru; VanKeuls, Fred W.; Miranda, Felix A.; Canedy, Chadwick L.; Aggarwal, Sanjeev; Venkatesan, Thirumalai; Ramesh, Ramamoorthy

    2000-01-01

    The correlation of electric field and critical design parameters such as the insertion loss, frequency ability return loss, and bandwidth of conductor/ferroelectric/dielectric microstrip tunable K-band microwave filters is discussed in this work. This work is based primarily on barium strontium titanate (BSTO) ferroelectric thin film based tunable microstrip filters for room temperature applications. Two new parameters which we believe will simplify the evaluation of ferroelectric thin films for tunable microwave filters, are defined. The first of these, called the sensitivity parameter, is defined as the incremental change in center frequency with incremental change in maximum applied electric field (EPEAK) in the filter. The other, the loss parameter, is defined as the incremental or decremental change in insertion loss of the filter with incremental change in maximum applied electric field. At room temperature, the Au/BSTO/LAO microstrip filters exhibited a sensitivity parameter value between 15 and 5 MHz/cm/kV. The loss parameter varied for different bias configurations used for electrically tuning the filter. The loss parameter varied from 0.05 to 0.01 dB/cm/kV at room temperature.

  11. An optically tunable wideband optoelectronic oscillator based on a bandpass microwave photonic filter.

    PubMed

    Jiang, Fan; Wong, Jia Haur; Lam, Huy Quoc; Zhou, Junqiang; Aditya, Sheel; Lim, Peng Huei; Lee, Kenneth Eng Kian; Shum, Perry Ping; Zhang, Xinliang

    2013-07-15

    An optoelectronic oscillator (OEO) with wideband frequency tunability and stable output based on a bandpass microwave photonic filter (MPF) has been proposed and experimentally demonstrated. Realized by cascading a finite impulse response (FIR) filter and an infinite impulse response (IIR) filter together, the tunable bandpass MPF successfully replaces the narrowband electrical bandpass filter in a conventional single-loop OEO and serves as the oscillating frequency selector. The FIR filter is based on a tunable multi-wavelength laser and dispersion compensation fiber (DCF) while the IIR filter is simply based on an optical loop. Utilizing a long length of DCF as the dispersion medium for the FIR filter also provides a long delay line for the OEO feedback cavity and as a result, optical tuning over a wide frequency range can be achieved without sacrificing the quality of the generated signal. By tuning the wavelength spacing of the multi-wavelength laser, the oscillation frequency can be tuned from 6.88 GHz to 12.79 GHz with an average step-size of 0.128 GHz. The maximum frequency drift of the generated 10 GHz signal is observed to be 1.923 kHz over 1 hour and its phase noise reaches the -112 dBc/Hz limit of our measuring equipment at 10 kHz offset frequency. PMID:23938489

  12. Observation of tunable optical filtering in photosensitive composite structures containing liquid crystals.

    PubMed

    Gilardi, Giovanni; De Sio, Luciano; Beccherelli, Romeo; Asquini, Rita; d'Alessandro, Antonio; Umeton, Cesare

    2011-12-15

    We report on the investigation and characterization of an optically tunable filtering effect, observed in a waveguide grating made of alternated strips of photocurable polymer and a mixture of azo-dye-doped liquid crystal. The grating is sandwiched between two borosilicate glasses, one of which includes an ion-exchanged channel waveguide, which confines the optical signal to be filtered. Exposure to a low power visible light beam modifies the azo-dye molecular configuration, thus allowing the filtered wavelength to be tuned over a 6.6 nm range. Simulations of the filtering response are well described with our experimental findings. PMID:22179873

  13. Magnetic-field tunable multichannel filter in a plasma photonic crystal at microwave frequencies.

    PubMed

    Chang, Tsung-Wen; Chien, Jia-Ren Chang; Wu, Chien-Jang

    2016-02-01

    The microwave magnetic-field tunable filtering properties in a multichannel filter based on use of a one-dimensional finite magnetized plasma photonic crystal (PPC) are theoretically investigated. The considered PPC has a structure of air/(AB)N/air, where A is a dielectric layer, B is a plasma layer, and N is the stack number. First, in the absence of an externally applied magnetic field, the structure can work as a multichannel filter whose channel number is equal to N-1 for N>1. Next, in the presence of an externally applied field, the filtering properties become tunable, i.e., the channel frequencies can be shifted as a function of the applied magnetic field. We find that the effect of the magnetic field will cause the channel frequencies to be blue-shifted or red-shifted depending on the orientation of the applied magnetic field. PMID:26836104

  14. All-fiber tunable laser based on an acousto-optic tunable filter and a tapered fiber.

    PubMed

    Huang, Ligang; Song, Xiaobo; Chang, Pengfa; Peng, Weihua; Zhang, Wending; Gao, Feng; Bo, Fang; Zhang, Guoquan; Xu, Jingjun

    2016-04-01

    An all-fiber tunable laser was fabricated based on an acousto-optic tunable filter and a tapered fiber. The structure was of a high signal-to-noise ratio, therefore, no extra gain flattening was needed in the laser. In the experiment, the wavelength of the laser could be tuned from 1532.1 nm to 1570.4 nm with a 3-dB bandwidth of about 0.2 nm. Given enough nonlinearity in the laser cavity, it could also generate a sliding-frequency pulse train. The laser gains advantages of fast tuning and agility in pulse generation, and its simple structure is low cost for practical applications. PMID:27137035

  15. Invisible grazings and dangerous bifurcations in impacting systems: The problem of narrow-band chaos

    NASA Astrophysics Data System (ADS)

    Banerjee, Soumitro; Ing, James; Pavlovskaia, Ekaterina; Wiercigroch, Marian; Reddy, Ramesh K.

    2009-03-01

    We discovered a narrow band of chaos close to the grazing condition for a simple soft impact oscillator. The phenomenon was observed experimentally for a range of system parameters. Through numerical stability analysis, we argue that this abrupt onset to chaos is caused by a dangerous bifurcation in which two unstable period-3 orbits, created at “invisible” grazings, take part.

  16. Invisible grazings and dangerous bifurcations in impacting systems: the problem of narrow-band chaos.

    PubMed

    Banerjee, Soumitro; Ing, James; Pavlovskaia, Ekaterina; Wiercigroch, Marian; Reddy, Ramesh K

    2009-03-01

    We discovered a narrow band of chaos close to the grazing condition for a simple soft impact oscillator. The phenomenon was observed experimentally for a range of system parameters. Through numerical stability analysis, we argue that this abrupt onset to chaos is caused by a dangerous bifurcation in which two unstable period-3 orbits, created at "invisible" grazings, take part. PMID:19392086

  17. Electronic structure descriptor for the discovery of narrow-band red-emitting phosphors

    DOE PAGESBeta

    Wang, Zhenbin; Chu, Iek -Heng; Zhou, Fei; Ong, Shyue Ping

    2016-05-09

    Narrow-band red-emitting phosphors are a critical component of phosphor-converted light-emitting diodes for highly efficient illumination-grade lighting. In this work, we report the discovery of a quantitative descriptor for narrow-band Eu2+-activated emission identified through a comparison of the electronic structures of known narrow-band and broad-band phosphors. We find that a narrow emission bandwidth is characterized by a large splitting of more than 0.1 eV between the two highest Eu2+ 4f7 bands. By incorporating this descriptor in a high-throughput first-principles screening of 2259 nitride compounds, we identify five promising new nitride hosts for Eu2+-activated red-emitting phosphors that are predicted to exhibit goodmore » chemical stability, thermal quenching resistance, and quantum efficiency, as well as narrow-band emission. Lastly, our findings provide important insights into the emission characteristics of rare-earth activators in phosphor hosts and a general strategy to the discovery of phosphors with a desired emission peak and bandwidth.« less

  18. Narrow band coronographic imaging of the bipolar nebula around the LBV R127

    NASA Technical Reports Server (NTRS)

    Clampin, Mark; Nota, Antonella; Golimowski, David A.; Leitherer, Claus

    1992-01-01

    New high resolution narrow band coronographic images of the R127 nebula have been recently obtained. The nebula displays a bipolar morphology and is similar in appearance to the nebula around AG Carinae. The observations improve the values for the linear dimensions (1.9 x 2.2 pc) and yield an estimated nebular mass of 3.1 solar mass.

  19. The relationship between rape biomass and narrow-band vegetation indices

    NASA Astrophysics Data System (ADS)

    Huang, Jingfeng; Wang, Yuan; Wang, Fumin; Wang, Xiuzhen

    2004-11-01

    The Relationships between rape biomass and hyperspectral vegetation indices are investigated in this paper. The data for this study comes from field hyperspectral reflectance measurements of rape during 2002-2003 growing period. Reflectance was measured in discrete narrow bands between 350 and 2500 nm. Observed rape biomass included wet biomass (WBM including leaf wet biomass-LWBM, stem wet biomass-SWBM, fruit wet biomass-FWBM), and dry biomass(DBM: including leaf dry biomass-LDBM, stem dry biomass, fruit dry biomass-FDBM). Narrow band normalized difference vegetation index (NBNDVI) and narrow band ratio vegetation index (NBRVI)involving all possible two-band combinations of discrete channels was tested. Special narrow band lambda (λ1) versus lambda (λ2) plots of R2 values illustrate the most effective wavelength combinations (λ1 and λ2) and band-width (Δλ1 and Δλ2) for predicting rape biomass at different development stage. A strong relationship with rape biomass is located in red-edge, the longer portion of red, moisture-sensitive NIR, longer portion of the blue band, the intermediate portion of SWIR, and the longer portion of SWIR.

  20. Filter-less frequency-doubling microwave signal generator with tunable phase shift

    NASA Astrophysics Data System (ADS)

    Li, Yueqin; Pei, Li; Li, Jing; Wang, Yiqun; Yuan, Jin

    2016-07-01

    A prototype for frequency-doubling microwave signal generator with tunable phase shift based on a filter-less architecture is proposed and analyzed. In the proposal, one dual parallel polarization modulator is used as the key component to generate two ±1st order sidebands along the orthogonal polarization directions with suppressed carrier. Then the polarization states of the two sidebands are aligned with the principal axes of an electro-optical phase modulator (EOPM). Tunable phase shift is implemented by controlling the direct current voltage applied to the EOPM. Without using any filters or wavelength-dependent components, the system possesses good frequency tunability and it can be applied to multi-wavelength operation. Taking advantage of the ability of frequency multiplication, the frequency tuning range can be wider than the operation bandwidth of the modulator. By theoretical analyses and simulated verifications, a frequency-doubling microwave signal ranging from 22 to 40 GHz with full range phase shift is achieved.

  1. Tunable, Strain-Controlled Nanoporous MoS₂ Filter for Water Desalination.

    PubMed

    Li, Weifeng; Yang, Yanmei; Weber, Jeffrey K; Zhang, Gang; Zhou, Ruhong

    2016-02-23

    The deteriorating state of global fresh water resources represents one of the most serious challenges that scientists and policymakers currently face. Desalination technologies, which are designed to extract potable water from the planet's bountiful stores of seawater, could serve to alleviate much of the stress that presently plagues fresh water supplies. In recent decades, desalination methods have improved via water-filtering architectures based on nanoporous graphene filters and artificial membranes integrated with biological water channels. Here, we report the auspicious performance (in simulations) of an alternative nanoporous desalination filter constructed from a MoS2 nanosheet. In striking contrast to graphene-based filters, we find that the "open" and "closed" states of the MoS2 filter can be regulated by the introduction of mechanical strain, yielding a highly tunable nanopore interface. By applying lateral strain to the MoS2 filter in our simulations, we see that the transition point between "open" and "closed" states occurs under tension that induces about 6% cross-sectional expansion in the membrane (6% strain); the open state of the MoS2 filter demonstrates high water transparency and a strong salt filtering capability even under 12% strain. Our results thus demonstrate the promise of a controllable nanoporous MoS2 desalination filter, wherein the morphology and size of the central nanopore can be precisely regulated by tensile strain. These findings support the design and proliferation of tunable nanodevices for filtration and other applications. PMID:26800095

  2. Resolution improvement of grating spectrometer by using a tunable Fabry-Perot filter

    NASA Astrophysics Data System (ADS)

    Fang, Liang; Shi, Zhendong; Qiu, Chuankai; Zhou, Chongxi

    2015-10-01

    Aiming at the problem of the resolution reduction in a miniaturized grating spectrometer, we presented a method to improve its spectral resolution by inserting a tunable Fabry-Perot filter into its optical path before the grating. The Fabry-Perot filter was designed to filter out a partial spectrogram and separate the original undistinguishable spectral lines so as to make their actual wavelengths can be detected. The different cavity length of the Fabry-Perot filter is corresponding to the different separated partial spectrogram. Combining all the separated partial spectrograms, an entire spectrogram with improved resolution can be achieved. Experimentally, the spectral resolution of a grating dispersive system was improved from 2 nm to 1.2nm in a broad spectral range by insetting a homemade tunable Fabry-Perot filter, which demonstrated the feasibility of this scheme. The tunable Fabry-Perot filter is fit for miniaturization by using MEMS technology and is able to work as an independent module. The method proposed provides a potential way to improve the spectral resolution without reducing the spectral range of the existing miniaturized grating spectrometers.

  3. Acousto-Optic Tunable Filter Hyperspectral Microscope Imaging Method for Characterizing Spectra from Foodborne Pathogens.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Hyperspectral microscope imaging (HMI) method, which provides both spatial and spectral characteristics of samples, can be effective for foodborne pathogen detection. The acousto-optic tunable filter (AOTF)-based HMI method can be used to characterize spectral properties of biofilms formed by Salmon...

  4. Integrated InP-InGaAsP tunable coupled ring optical bandpass filters with zero insertion loss.

    PubMed

    Guzzon, Robert S; Norberg, Erik J; Parker, John S; Johansson, Leif A; Coldren, Larry A

    2011-04-11

    Second and third-order monolithically integrated coupled ring bandpass filters are demonstrated in the InP-InGaAsP material system with active semiconductor optical amplifiers (SOAs) and current injection phase modulators (PMs). Such integration achieves a high level of tunability and precise generation of optical filters in the RF domain at telecom wavelengths while simultaneously compensating for device insertion loss. Passband bandwidth tunability of 3.9 GHz to 7.1 GHz and stopband extinction up to 40 dB are shown for third-order filters. Center frequency tunability over a full free spectral range (FSR) is demonstrated, allowing for the placement of a filter anywhere in the telecom C-band. A Z-transform representation of coupled resonator filters is derived and compared with experimental results. A theoretical description of filter tunability is presented. PMID:21503092

  5. Tunable light filtering by a Bragg mirror/heavily doped semiconducting nanocrystal composite

    PubMed Central

    Kriegel, Ilka

    2015-01-01

    Summary Tunable light filters are critical components for many optical applications in which light in-coupling, out-coupling or rejection is crucial, such as lasing, sensing, photovoltaics and information and communication technology. For this purpose, Bragg mirrors (band-pass filters with high reflectivity) represent good candidates. However, their optical characteristics are determined during the fabrication stage. Heavily doped semiconductor nanocrystals (NCs), on the other hand, deliver a high degree of optical tunability through the active modulation of their carrier density, ultimately influencing their plasmonic absorption properties. Here, we propose the design of an actively tunable light filter composed of a Bragg mirror and a layer of plasmonic semiconductor NCs. We demonstrate that the filtering properties of the coupled device can be tuned to cover a wide range of frequencies from the visible to the near infrared (vis–NIR) spectral region when employing varying carrier densities. As the tunable component, we implemented a dispersion of copper selenide (Cu2−xSe) NCs and a film of indium tin oxide (ITO) NCs, which are known to show optical tunablility with chemical or electrochemical treatments. We utilized the Mie theory to describe the carrier-dependent plasmonic properties of the Cu2−x Se NC dispersion and the effective medium theory to describe the optical characteristics of the ITO film. The transmission properties of the Bragg mirror have been modelled with the transfer matrix method. We foresee ease of experimental realization of the coupled device, where filtering modulation is achieved upon chemical and electrochemical post-fabrication treatment of the heavily doped semiconductor NC component, eventually resulting in tunable transmission properties of the coupled device. PMID:25671163

  6. Tunable First-Order Resistorless All-Pass Filter with Low Output Impedance

    PubMed Central

    2014-01-01

    This paper presents a voltage mode cascadable single active element tunable first-order all-pass filter with a single passive component. The active element used to realise the filter is a new building block termed as differential difference dual-X current conveyor with a buffered output (DD-DXCCII). The filter is thus realized with the help of a DD-DXCCII, a capacitor, and a MOS transistor. By exploiting the low output impedance, a higher order filter is also realized. Nonideal and parasitic study is also carried out on the realised filters. The proposed DD-DXCCII filters are simulated using TSMC the 0.25 µm technology. PMID:24587713

  7. Optofluidic-tunable color filters and spectroscopy based on liquid-crystal microflows.

    PubMed

    Cuennet, J G; Vasdekis, A E; Psaltis, D

    2013-07-21

    The integration of color filters with microfluidics has attracted substantial attention in recent years, for on-chip absorption, fluorescence, or Raman analysis. We describe such tunable filters based on the micro-flow of liquid crystals. The filter operation is based on the wavelength-dependent liquid crystal birefringence that can be tuned by modifying the flow velocity field in the microchannel. The latter is possible both temporally and spatially by varying the inlet pressure and the channel geometry, respectively. We explored the use of these optofluidic filters for on-chip absorption spectroscopy in poly(dimethylsiloxane) microfluidic systems; by integrating the distance-dependent color filter with a dye-filled micro-channel, the absorption spectrum of a dye could be measured. Liquid crystal microflows substantially simplify the optofluidic integration, actuation and tuning of color filters for lab-on-a-chip spectroscopic applications. PMID:23752198

  8. MEMS optical tunable filter based on free-standing subwavelength silicon layers

    NASA Astrophysics Data System (ADS)

    Omran, Haitham; Sabry, Yasser M.; Sadek, Mohamed; Hassan, Khaled; Shalaby, Mohamed Y.; Khalil, Diaa

    2014-03-01

    We report a MEMS optical tunable filter based on high-aspect-ratio etching of sub-wavelength silicon layers on a silicon- on-insulator wafer. The reported filter has measured free-spectral and filter-tuning ranges of approximately 100 nm and a finesse of about 20 around a wavelength of 1550 nm, enabled by the use of 1000 nm-thick silicon layers and a balanced tilt-free motion using a lithographically-aligned electrostatic actuator. The average insertion loss of the filter is about 12 dB with a superior wavelength-dependent loss of about 1.5 dB. The filter has an out-of-band to in-band wavelength rejection ratio that is better than 20 dB. The reported filter experimental characteristics and its integrability are suitable for the production of integrated swept sources for optical coherence tomography application and miniaturized spectrometers.

  9. Optofluidic-Tunable Color Filters And Spectroscopy Based On Liquid-Crystal Microflows

    SciTech Connect

    Cuennet, J. G.; Vasdekis, Andreas E.; Psaltis, D.

    2013-05-24

    The integration of color filters with microfluidics has attracted substantial attention in recent years, for on-chip absorption, fluorescence, or Raman analysis. We describe such tunable filters based on the micro-flow of liquid crystals. The filter operation is based on the wavelength dependent liquid crystal birefringence that can be tuned by modifying the flow velocity field in the microchannel. The latter is possible both temporally and spatially by varying the inlet pressure and the channel geometry respectively. We explored the use of these optofluidic filters for on-chip absorption spectroscopy; by integrating the distance dependent color filter with a dye-filled micro-channel, the absorption spectrum of a dye could be measured. Liquid crystal microflows simplify substantially the optofluidic integration, actuation and tuning of color filters for lab-on-a-chip spectroscopic applications.

  10. Tunable coherence-free microwave photonic bandpass filter based on double cross gain modulation technique.

    PubMed

    Chan, Erwin H W

    2012-10-01

    A tunable, coherence-free, high-resolution microwave photonic bandpass filter, which is compatible to be inserted in a conventional fiber optic link, is presented. It is based on using two cross gain modulation based wavelength converters in a recursive loop. The double cross gain modulation technique solves the semiconductor optical amplifier facet reflection problem in the conventional recursive structure; hence the new microwave photonic signal processor has no coherent interference and no phase-induced intensity noise. It allows arbitrary narrow-linewidth telecommunication-type lasers to be used while enabling stable filter operation to be realized. The filter passband frequency can be tuned by using a wavelength tunable laser and a wavelength dependent time delay component. Experimental results demonstrate robust high-resolution bandpass filter operation with narrow-linewidth sources, no phase-induced intensity noise and a high signal-to-noise ratio performance. Tunable coherence-free operation of the high-resolution bandpass filter is also demonstrated. PMID:23188262

  11. Development of inexpensive optical broad- and narrow-band sensors for ecosystem research

    NASA Astrophysics Data System (ADS)

    Mollenhauer, Hannes; Cuntz, Thomas; Bumberger, Jan

    2014-05-01

    The observation and monitoring of ecosystem processes are great challenges in environmental science, due to the dynamic and complexity of such procedures. To describe and understand biotic and abiotic processes and their interaction it is necessary to acquire multiple parameters, which are influencing the natural regime. Essential issues are: the detection of spatial heterogeneities and scale overlapping procedures in the environment. To overcome these problems an adequate monitoring system should cover a representative area as well as have a sufficient resolution in time and space. Hence, the needed quantity of sensors (depending on the observed parameters or processes) can be enormous. According to these issues, there is a high demand on low-cost sensor technologies (with adequate performances) to realize a delicate monitoring platform. In the case of vegetation processes, one key feature is to characterize photosynthetic activity of the plants in detail. Common investigation methods are based on optical measurements. Here photosynthetically active radiation (PAR) sensors and hyperspectral sensors are in major use. Photosynthetically active radiation (solar radiation from 400 to 700 nanometers) designates the spectral range that photosynthetic organisms are able to use in the process of photosynthesis. PAR sensors enable the detection of the reflected solar light of the vegetation in whole the PAR wave band. The amount of absorption indicates photosynthetic activity of the plant. Hyperspectral sensors observe specific parts of the solar light spectrum and facilitate the determination of the main pigment classes (Chlorophyll, Carotenoid and Anthocyanin). Due to absorption of pigments they producing a specific spectral signature in the visible part of the electromagnetic spectrum (narrow-band peaks). If vegetation is affected by water or nutritional deficience the proportion of light-absorbing pigments is reduced which finally results in an overall reduced light

  12. An accurate cluster selection function for the J-PAS narrow-band wide-field survey

    NASA Astrophysics Data System (ADS)

    Ascaso, B.; Benítez, N.; Dupke, R.; Cypriano, E.; Lima-Neto, G.; López-Sanjuan, C.; Varela, J.; Alcaniz, J. S.; Broadhurst, T.; Cenarro, A. J.; Devi, N. Chandrachani; Díaz-García, L. A.; Fernandes, C. A. C.; Hernández-Monteagudo, C.; Mei, S.; Mendes de Oliveira, C.; Molino, A.; Oteo, I.; Schoenell, W.; Sodré, L.; Viironen, K.; Marín-Franch, A.

    2016-03-01

    The impending Javalambre Physics of the accelerating Universe Astrophysical Survey (J-PAS) will be the first wide-field survey of ≳ 8500 deg2 to reach the `stage IV' category. Because of the redshift resolution afforded by 54 narrow-band filters, J-PAS is particularly suitable for cluster detection in the range z<1. The photometric redshift dispersion is estimated to be only ˜0.003 with few outliers ≲4 per cent for galaxies brighter than i ˜ 23 AB, because of the sensitivity of narrow band imaging to absorption and emission lines. Here, we evaluate the cluster selection function for J-PAS using N-body+semi-analytical realistic mock catalogues. We optimally detect clusters from this simulation with the Bayesian Cluster Finder, and we assess the completeness and purity of cluster detection against the mock data. The minimum halo mass threshold we find for detections of galaxy clusters and groups with both >80 per cent completeness and purity is Mh ˜ 5 × 1013 M⊙ up to z ˜ 0.7. We also model the optical observable, M^{*}_CL-halo mass relation, finding a non-evolution with redshift and main scatter of σ _{M^{*}_CL | M_h}˜ 0.14 dex down to a factor 2 lower in mass than other planned broad-band stage IV surveys, at least. For the Mh ˜ 1 × 1014 M⊙ Planck mass limit, J-PAS will arrive up to z ˜ 0.85 with a σ _{M^{*}_CL | M_h}˜ 0.12 dex. Therefore, J-PAS will provide the largest sample of clusters and groups up to z ˜ 0.8 with a mass calibration accuracy comparable to X-ray data.

  13. Tunable Microstrip Filters Using Selectively Etched Ferroelectric Thin-Film Varactors for Coupling

    NASA Technical Reports Server (NTRS)

    Mueller, Carl H.; VanKeuls, Frederick W.; Romanofsky, Robert R.; Subramanyam, Guru; Miranda, Felix A.

    2006-01-01

    We report on the use of patterned ferroelectric films to fabricate proof of concept tunable one-pole microstrip filters with excellent transmission and mismatch/reflection properties at frequencies up to 24 GHz. By controlling the electric field distribution within the coupling region between the resonator and input/output lines, sufficiently high loaded and unloaded Q values are maintained so as to be useful for microstrip filter design, with low mismatch loss. In the 23 - 24 GHz region, the filter was tunable over a 100 MHz range, the loaded and unloaded Q values were 29 and 68, respectively, and the reflection losses were below -16 dB, which demonstrates the suitability of these films for practical microwave applications.

  14. A tunable submicro-optofluidic polymer filter based on guided-mode resonance

    NASA Astrophysics Data System (ADS)

    Xiao, Guohui; Zhu, Qiangzhong; Shen, Yang; Li, Kezheng; Liu, Mingkai; Zhuang, Qiandong; Jin, Chongjun

    2015-02-01

    Optical filters with reconfigurable spectral properties are highly desirable in a wide range of applications. We propose and experimentally demonstrate a tunable submicro-optofluidic polymer guided-mode resonance (PGMR) filter. The device is composed of a periodic grating sandwiched between a high index waveguide layer and a low index capping layer, which integrates submicro-fluidic channel arrays and a PGMR filter elegantly. A finite difference time domain (FDTD) method is employed to understand the spectral properties and determine appropriate device parameters. We fabricated the polymer guided-mode resonance filter with a method combining two-beam interference lithography, floating nanofilm transfer and thermal bonding techniques. Experimental results show that our tunable submicro-optofluidic PGMR filters can provide a broad spectral tuning range (13.181 nm), a narrow bandwidth (<2.504 nm), and a high reflection efficiency (>85%) in the visible region. Such submicro-optofluidic PGMR filters are highly compatible with existing nano/microfluidic technologies and would be valuable for the integrated flexible optical system.Optical filters with reconfigurable spectral properties are highly desirable in a wide range of applications. We propose and experimentally demonstrate a tunable submicro-optofluidic polymer guided-mode resonance (PGMR) filter. The device is composed of a periodic grating sandwiched between a high index waveguide layer and a low index capping layer, which integrates submicro-fluidic channel arrays and a PGMR filter elegantly. A finite difference time domain (FDTD) method is employed to understand the spectral properties and determine appropriate device parameters. We fabricated the polymer guided-mode resonance filter with a method combining two-beam interference lithography, floating nanofilm transfer and thermal bonding techniques. Experimental results show that our tunable submicro-optofluidic PGMR filters can provide a broad spectral tuning

  15. Tunable microwave notch filter created by stimulated Brillouin scattering in a silicon chip

    NASA Astrophysics Data System (ADS)

    Casas-Bedoya, A.; Morrison, Blair; Pagani, Mattia; Marpaung, David; Eggleton, Benjamin J.

    2015-12-01

    We show the first functional signal processing device based on forward stimulated Brillouin scattering from a silicon nanowire. We harness 1dB of SBS gain to create a high performance, energy efficient microwave photonic notch filter. The filter possess 48dB of suppression, 98 MHz linewidth, and is tunable within a 6 GHz bandwidth. This demonstration represents a significant advance in integrated microwave photonics with potential applications in on-chip microwave signal processing and establish the foundation towards the first CMOS-compatible high performance RF photonic filter.

  16. Chemical imaging and spectroscopy using tunable filters: Instrumentation, methodology, and multivariate analysis

    NASA Astrophysics Data System (ADS)

    Turner, John Frederick, II

    Spectral imaging has experienced tremendous growth during the past ten years and is rapidly becoming a formidable analytical tool. Recent advances in electronically tunable filters and array detectors are enabling high resolution spectral images to be acquired of chemical and biological systems that have traditionally been difficult to study non-invasively. Additionally, the development of powerful and inexpensive computer platforms is broadening the appeal of spectral imaging methods which have historically required costly and computationally adept computer workstations. The emphasis of my research has been to explore high throughput widefield imaging instrumentation and methodology using novel acousto-optic tunable filter (AOTF) and liquid crystal tunable filter (LCTF) imaging spectrometers. In order to demonstrate the feasibility of employing multiplexed AOTFs for spectroscopy and chemical imaging applications, a near- infrared (NIR) multiplexed AOTF spectrometer employing Hadamard encoding sequences has been developed. In addition, the use of multiplexed AOTFs as adaptive filters in NIR spectroscopy and fluorescence imaging has been demonstrated. A second type of electronically tunable image filter, the liquid crystal tunable filter (LCTF) has recently been developed and is well suited to high resolution, diffraction limited imaging applications. The earliest generation of LCTFs was based on the Lyot birefringent filter and possessed small transmittances due to the use of multiple polarizers and imperfect waveplate action. An improved LCTF prototype incorporating split-element Lyot filter stages has been evaluated and compared to the earlier generation of LCTF devices. The high image fidelity, wide acceptance angle, and large clear aperture of the LCTF make it well suited to macroscopic chemical imaging applications. A macroscopic imaging fluorometer employing LCTFs for source tuning and emission filtering has been developed for high throughput microtiter plate

  17. Tunable optical filters with wide wavelength range based on porous multilayers

    PubMed Central

    2014-01-01

    A novel concept for micromechanical tunable optical filter (TOF) with porous-silicon-based photonic crystals which provide wavelength tuning of ca. ±20% around a working wavelength at frequencies up to kilohertz is presented. The combination of fast mechanical tilting and pore-filling of the porous silicon multilayer structure increases the tunable range to more than 200 nm or provides fine adjustment of working wavelength of the TOF. Experimental and optical simulation data for the visible and near-infrared wavelength range supporting the approach are shown. TOF are used in spectroscopic applications, e.g., for process analysis. PMID:25232293

  18. Tunable optical filters with wide wavelength range based on porous multilayers.

    PubMed

    Mescheder, Ulrich; Khazi, Isman; Kovacs, Andras; Ivanov, Alexey

    2014-01-01

    A novel concept for micromechanical tunable optical filter (TOF) with porous-silicon-based photonic crystals which provide wavelength tuning of ca. ±20% around a working wavelength at frequencies up to kilohertz is presented. The combination of fast mechanical tilting and pore-filling of the porous silicon multilayer structure increases the tunable range to more than 200 nm or provides fine adjustment of working wavelength of the TOF. Experimental and optical simulation data for the visible and near-infrared wavelength range supporting the approach are shown. TOF are used in spectroscopic applications, e.g., for process analysis. PMID:25232293

  19. Wavelength tunable liquid crystal imaging filters for remote sensing from geosynchronous platforms

    NASA Technical Reports Server (NTRS)

    Foukal, Peter

    1992-01-01

    Recent advances in liquid crystal technology have enabled us to construct tunable birefringent filters with bandwidths between approximately 0.1 nm and 50 nm. The center wavelength of these filters can be selected electronically, in a few tens of milliseconds, with no moving parts. These liquid crystal tunable filters (LCTF's), together with existing CCD detectors, make possible a new generation of lightweight, rugged, high-resolution imaging spectrophotometers. Such instruments would be particularly interesting for remote sensing applications from geosynchronous platforms. Important advantages exist in the aperture, absence of image shift, power consumption, size, weight, and absence of high drive frequencies, compared to current instruments used or considered for multispectral scene analysis. In the present work, we have reviewed spectral requirements of planned NASA geosynchronous remote sensing missions and identified several applications of the liquid crystal tunable filter technology. We have modeled the LCTF performance in the visible and near-infrared, and carried out a literature study on space-hardening of the filter components, to evaluate the suitability of LCTF's for geosynchronous missions. We have also compared the power consumption, weight, size, reliability, and optical performance of an imaging spectrophotometer using a LCTF monochromator, to other instruments that have been put forward for remote sensing from geosynchronous platforms. We put forward some conceptual designs for LCTF's that seem to offer important reliability, over the mechanical filter wheels presently baselined for the HEPI and ALM experiments. The extremely wide acceptance angle achievable with LCTF's could also avoid the present need for large-aperture interference filters in the ALM (and LIS) experiments. Thermal vacuum testing and radiation damage analysis is required to investigate the space hardening of these new filters for geosynchronous flight.

  20. Development of stress-induced curved actuators for a tunable THz filter based on double split-ring resonators

    NASA Astrophysics Data System (ADS)

    Lin, Yu-Sheng; Qian, You; Ma, Fusheng; Liu, Zhen; Kropelnicki, Piotr; Lee, Chengkuo

    2013-03-01

    Using stress-induced curved cantilevers to form double split-ring resonator (DSRR) in three-dimensional configuration, an electrically tunable microelectromechanical system (MEMS) based out-of-plane metamaterials THz filter is experimentally demonstrated and characterized. While the achieved tunable range for the resonant frequency is 0.5 THz at 20 V bias, quality factor of the resonant frequency is improved as well. This MEMS based THz filter using released DSRR structures shows its potential in tunable metamaterials applications such as sensors, optical switches, and filters.

  1. Stopping Narrow-Band X-Ray Pulses in Nuclear Media

    NASA Astrophysics Data System (ADS)

    Kong, Xiangjin; Pálffy, Adriana

    2016-05-01

    A control mechanism for stopping x-ray pulses in resonant nuclear media is investigated theoretically. We show that narrow-band x-ray pulses can be mapped and stored as nuclear coherence in a thin-film planar x-ray cavity with an embedded 57Fe nuclear layer. The pulse is nearly resonant to the 14.4 keV Mössbauer transition in the 57Fe nuclei. The role of the control field is played here by a hyperfine magnetic field which induces interference effects reminiscent of electromagnetically induced transparency. We show that, by switching off the control magnetic field, a narrow-band x-ray pulse can be completely stored in the cavity for approximately 100 ns. Additional manipulation of the external magnetic field can lead to both group velocity and phase control of the pulse in the x-ray cavity sample.

  2. Scaling effect on the estimation of chlorophyll content using narrow band NDVIs based on radiative transfer model

    NASA Astrophysics Data System (ADS)

    Wang, Hong; Shi, Runhe; Liu, Pudong; Cong, Zhou

    2015-09-01

    The aim of this work is to use narrow band normalized difference vegetation indices to compare the estimations of chlorophyll contents at foliar level and canopy level, through a large number of simulated canopy reflectance spectra under different chlorophyll contents based on PROSPECT model and SAIL model. 10 narrow band NDVIs were selected at the identified ranges that can effectively assess foliar chlorophyll content. We analyzed the correlations between canopy chlorophyll contents and the ten narrow band NDVIs firstly, and then analyze these indices' sensitivities to all canopy parameters, the adaptation of the 10 narrow band NDVIs used in assessing the canopy chlorophyll content were evaluated finally. We found that only two narrow band NDVIs (i.e., NDVI(875, 725) and NDVI(900,720)) can be applied for the estimation of chlorophyll contents at canopy level.

  3. CMOS-compatible temperature-independent tunable silicon optical lattice filters.

    PubMed

    Lu, Liangjun; Zhou, Linjie; Sun, Xiaomeng; Xie, Jingya; Zou, Zhi; Zhu, Haike; Li, Xinwan; Chen, Jianping

    2013-04-22

    We present a CMOS-compatible athermal tunable silicon optical lattice filter composed of 10 cascaded 2 × 2 asymmetric Mach-Zehnder interferometers. Active tuning experiments show that the filter central wavelength can be red-/blue-shifted by 13.1/21.3 nm with power consumption of 77/96 mW on top/bottom arms. Temperature shift measurements show that the thermal-sensitivity of the filter central wavelength before active tuning is as low as -1.465 pm/°C. The thermal-sensitivity is varied within 26.5 pm/°C to -27.1 pm/°C when the filter central wavelength is tuned in the wavelength range of 1534 nm to 1551 nm. We use the transfer matrix method to theoretically model the lattice filter and its thermal-sensitivity before and after tuning is analyzed and discussed. PMID:23609656

  4. Narrow-band radiation wavelength measurement by processing digital photographs in RAW format

    SciTech Connect

    Kraiskii, A V; Mironova, T V; Sultanov, T T

    2012-12-31

    The technique of measuring the mean wavelength of narrow-band radiation in the 455 - 625-nm range using the image of the emitting surface is presented. The data from the camera array unprocessed by the built-in processor (RAW format) are used. The method is applied for determining the parameters of response of holographic sensors. Depending on the wavelength and brightness of the image fragment, the mean square deviation of the wavelength amounts to 0.3 - 3 nm. (experimental techniques)

  5. Identification of vessel degeneration and endometrosis in the equine endometrium, using narrow-band imaging hysteroscopy.

    PubMed

    Otzen, Henning; Sieme, Harald; Oldenhof, Harriëtte; Ertmer, Franziska; Kehr, Anne; Rode, Kristina; Klose, Kristin; Rohn, Karl; Schoon, Heinz-Adolf; Meinecke, Burkhard

    2016-10-01

    In this study, endometrosis and angiosclerosis in mares were studied. Endometrosis is a severe, progressive, and irreversible fibrotic condition that affects the endometrium, whereas angiosclerosis refers to thickening of vessel walls due to degenerative changes leading to reduced elasticity of the walls and lower perfusion. Histologic evaluations were performed on biopsies and compared with vascular features of the endometrial surface obtained via narrow-band imaging (NBI) hysteroscopy. First, it was determined if hysteroscopic evaluation of the endometrium using NBI resulted in a better visualization of the vascular pattern (i.e., vessel-versus-background contrast was increased) compared with using white light. This was found to be the case for examinations in vivo (n = 10), but not when using abattoir uteri (n = 3). In the second part of this study, it was determined if vascular densities and sizes as derived from NBI images could be used as indicators for the degree of degenerative changes of the equine endometrium and its vessels. Narrow-band imaging hysteroscopic evaluations were performed (n = 10), and endometrial biopsies (n = 32) were collected. Histologic specimens were evaluated for degree of endometrosis and angiosclerosis, and they were classified in Kenney categories. Narrow-band imaging images were analyzed for vascular pattern. Samples classified to Kenney category I, or without signs of vessel degeneration, had significantly higher vascular densities than samples from Kenney category IIa or with angiosclerosis. In conclusion, narrow-band imaging facilitates enhanced visualization of the vasculature of the equine endometrium during hysteroscopies, which has applications in detection of endometrosis and angiosclerosis. PMID:27264739

  6. On resolving 2M - 1 narrow-band signals with an M sensor uniform linear array

    NASA Technical Reports Server (NTRS)

    Williams, Douglas B.; Johnson, Don H.

    1992-01-01

    Length 2M real signal vectors are used to address the problem of determining the maximum number of narrow-band signals whose parameters can be estimated with a linear array of M equally spaced sensors. It is shown that 2M of these real vectors are linearly independent with probability one, and, thus in the presence of additive white noise, the parameters of 2M - 1 signals can be estimated. An algorithm for determining directions and amplitudes is presented.

  7. Performance Enhancement of Tunable Bandpass Filters Using Selective Etched Ferroelectric Thin Films

    NASA Technical Reports Server (NTRS)

    Miranda, Felix A.; Mueller, Carl H.; VanKeuls, Fred W.; Subramanyam, Guru; Vignesparamoorthy, Sivaruban

    2003-01-01

    The inclusion of voltage-tunable barium strontium titanate (BSTO) thin films into planar band pass filters offers tremendous potential to increase their versatility. The ability to tune the passband so as to correct for minor deviations in manufacturing tolerances, or to completely reconfigure the operating frequencies of a microwave communication system, are highly sought-after goals. However, use of ferroelectric films in these devices results in higher dielectric losses, which in turn increase the insertion loss and decrease the quality factors of the filters. This study explores the use of patterned ferroelectric layers to minimize dielectric losses without degrading tunability. Patterning the ferroelectric layers enables us to constrict the width of the ferroelectric layers between the coupled microstrip lines, and minimize losses due to ferroelectric layers. Coupled one-pole microstrip bandpass filters with fundamental resonances at approx. 7.2 GHz and well defined harmonic resonances at approx. 14.4 and approx. 21.6 GHz, were designed, simulated and tested. For one of the filters, experimental results verified that its center frequency was tunable by 528 MHz at a center frequency of 21.957 GHz, with insertion losses varying from 4.3 to 2.5 dB, at 0 and 3.5 V/micron, respectively. These data demonstrate that the tuning-to-loss figure of merit of tunable microstrip filters can be greatly improved using patterned ferroelectric thin films as the tuning element, and tuning can be controlled by engineering the ferroelectric constriction in the coupled sections.

  8. A tunable submicro-optofluidic polymer filter based on guided-mode resonance.

    PubMed

    Xiao, Guohui; Zhu, Qiangzhong; Shen, Yang; Li, Kezheng; Liu, Mingkai; Zhuang, Qiandong; Jin, Chongjun

    2015-02-28

    Optical filters with reconfigurable spectral properties are highly desirable in a wide range of applications. We propose and experimentally demonstrate a tunable submicro-optofluidic polymer guided-mode resonance (PGMR) filter. The device is composed of a periodic grating sandwiched between a high index waveguide layer and a low index capping layer, which integrates submicro-fluidic channel arrays and a PGMR filter elegantly. A finite difference time domain (FDTD) method is employed to understand the spectral properties and determine appropriate device parameters. We fabricated the polymer guided-mode resonance filter with a method combining two-beam interference lithography, floating nanofilm transfer and thermal bonding techniques. Experimental results show that our tunable submicro-optofluidic PGMR filters can provide a broad spectral tuning range (13.181 nm), a narrow bandwidth (<2.504 nm), and a high reflection efficiency (>85%) in the visible region. Such submicro-optofluidic PGMR filters are highly compatible with existing nano/microfluidic technologies and would be valuable for the integrated flexible optical system. PMID:25630880

  9. Tunable Band-Stop Filters for Graphene Plasmons Based on Periodically Modulated Graphene.

    PubMed

    Shi, Bin; Cai, Wei; Zhang, Xinzheng; Xiang, Yinxiao; Zhan, Yu; Geng, Juan; Ren, Mengxin; Xu, Jingjun

    2016-01-01

    Tunable band-stop filters based on graphene with periodically modulated chemical potentials are proposed. Periodic graphene can be considered as a plasmonic crystal. Its energy band diagram is analyzed, which clearly shows a blue shift of the forbidden band with increasing chemical potential. Structural design and optimization are performed by an effective-index-based transfer matrix method, which is confirmed by numerical simulations. The center frequency of the filter can be tuned in a range from 37 to 53 THz based on the electrical tunability of graphene, while the modulation depth (-26 dB) and the bandwidth (3.1 THz) of the filter remain unchanged. Specifically, the bandwidth and modulation depth of the filters can be flexibly preset by adjusting the chemical potential ratio and the period number. The length of the filter (~750 nm) is only 1/9 of the operating wavelength in vacuum, which makes the filter a good choice for compact on-chip applications. PMID:27228949

  10. Tunable Band-Stop Filters for Graphene Plasmons Based on Periodically Modulated Graphene

    PubMed Central

    Shi, Bin; Cai, Wei; Zhang, Xinzheng; Xiang, Yinxiao; Zhan, Yu; Geng, Juan; Ren, Mengxin; Xu, Jingjun

    2016-01-01

    Tunable band-stop filters based on graphene with periodically modulated chemical potentials are proposed. Periodic graphene can be considered as a plasmonic crystal. Its energy band diagram is analyzed, which clearly shows a blue shift of the forbidden band with increasing chemical potential. Structural design and optimization are performed by an effective-index-based transfer matrix method, which is confirmed by numerical simulations. The center frequency of the filter can be tuned in a range from 37 to 53 THz based on the electrical tunability of graphene, while the modulation depth (−26 dB) and the bandwidth (3.1 THz) of the filter remain unchanged. Specifically, the bandwidth and modulation depth of the filters can be flexibly preset by adjusting the chemical potential ratio and the period number. The length of the filter (~750 nm) is only 1/9 of the operating wavelength in vacuum, which makes the filter a good choice for compact on-chip applications. PMID:27228949

  11. Tunable Band-Stop Filters for Graphene Plasmons Based on Periodically Modulated Graphene

    NASA Astrophysics Data System (ADS)

    Shi, Bin; Cai, Wei; Zhang, Xinzheng; Xiang, Yinxiao; Zhan, Yu; Geng, Juan; Ren, Mengxin; Xu, Jingjun

    2016-05-01

    Tunable band-stop filters based on graphene with periodically modulated chemical potentials are proposed. Periodic graphene can be considered as a plasmonic crystal. Its energy band diagram is analyzed, which clearly shows a blue shift of the forbidden band with increasing chemical potential. Structural design and optimization are performed by an effective-index-based transfer matrix method, which is confirmed by numerical simulations. The center frequency of the filter can be tuned in a range from 37 to 53 THz based on the electrical tunability of graphene, while the modulation depth (‑26 dB) and the bandwidth (3.1 THz) of the filter remain unchanged. Specifically, the bandwidth and modulation depth of the filters can be flexibly preset by adjusting the chemical potential ratio and the period number. The length of the filter (~750 nm) is only 1/9 of the operating wavelength in vacuum, which makes the filter a good choice for compact on-chip applications.

  12. Tunability of multichannel optical filter based on magnetized one-dimensional plasma photonic crystal

    SciTech Connect

    Jamshidi-Ghaleh, K. Karami-Garehgeshlagi, F.; Mazloom, A. A.

    2015-10-15

    A one dimensional plasma photonic crystal (1DPPC) structure was proposed to design a tunable compressing/broadening multi-channel optical filter with external controllability. The 1DPPC with arrangement of (AP){sup n}D(PA){sup n}, where A and D are the dielectric materials, P is a magnetized plasma layer and n is the number of the periodicity, was proposed. The well-known transfer matrix method was employed for analysis. In linear transmittance spectrum, n − 1 defect modes were appeared inside the photonic band gap. The results were shown that by increasing the applied magnetic field intensity and its direction, a red-shift and blue-shift were, respectively, observed in defect mode frequencies. On the other hand, the modes were compressed and broadened with increasing the intensity and the direction of the applied magnetic field, respectively. Externally controllable defect modes can be useful in designing a multichannel tunable optical filter.

  13. Tunable optoelectronic oscillator incorporating an all-optical microwave photonic filter

    NASA Astrophysics Data System (ADS)

    Li, Cheng-Xin; Chen, Fu-Shen; Zhang, Jia-Hong

    2015-01-01

    A tunable optoelectronic oscillator (OEO), which employs an all-optical microwave photonic filter (MPF) consisting of two laser sources (LD1 and LD2), an optical coupler (OC, 50:50), a Mach-Zehnder modulator (MZM), and a chirped fiber Bragg grating, is proposed. Because the central frequency of the all-optical MPF can be shifted by changing the wavelength spacing between the two laser sources, the frequency tunability of the OEO can be realized by incorporating such an all-optical MPF into an optical domain dual-loop OEO without any electronic microwave filters. A detailed theoretical analysis is presented and the results are confirmed by an experiment. A microwave signal with a frequency-tuning range from 4.057 to 8.595 GHz is generated. The phase noise, the long-term stability, and the side-mode suppression performance of the generated microwave signal are also investigated.

  14. Tunability of multichannel optical filter based on magnetized one-dimensional plasma photonic crystal

    NASA Astrophysics Data System (ADS)

    Jamshidi-Ghaleh, K.; Karami-Garehgeshlagi, F.; Mazloom, A. A.

    2015-10-01

    A one dimensional plasma photonic crystal (1DPPC) structure was proposed to design a tunable compressing/broadening multi-channel optical filter with external controllability. The 1DPPC with arrangement of (AP)nD(PA)n, where A and D are the dielectric materials, P is a magnetized plasma layer and n is the number of the periodicity, was proposed. The well-known transfer matrix method was employed for analysis. In linear transmittance spectrum, n - 1 defect modes were appeared inside the photonic band gap. The results were shown that by increasing the applied magnetic field intensity and its direction, a red-shift and blue-shift were, respectively, observed in defect mode frequencies. On the other hand, the modes were compressed and broadened with increasing the intensity and the direction of the applied magnetic field, respectively. Externally controllable defect modes can be useful in designing a multichannel tunable optical filter.

  15. An ultrawide tunable range single passband microwave photonic filter based on stimulated Brillouin scattering.

    PubMed

    Xiao, Yongchuan; Guo, Jing; Wu, Kui; Qu, Pengfei; Qi, Huajuan; Liu, Caixia; Ruan, Shengping; Chen, Weiyou; Dong, Wei

    2013-02-11

    A single passband microwave photonic filter with ultrawide tunable range based on stimulated Brillouin scattering is theoretically analyzed. Combining the gain and loss spectrums, tuning range with 44GHz is obtained without crosstalk by introducing two pumps. Adding more pumps, Tuning range multiplying with the multiplication factor equaling to the total quantity of pump can be achieved, which has potential application in microwave and millimeter wave wireless communication systems. PMID:23481728

  16. Development of a Compact Imaging Spectrometer Using Liquid Crystal Tunable Filter Technology

    NASA Technical Reports Server (NTRS)

    Faust, Jessica A; Biswas, Abhijit; Bearman, Gregory H.; Chrien, Thomas; Miller, Peter J.

    1996-01-01

    Liquid crystal tunable filters are useful in building compact multi-spectral instruments. The system is portable and adaptable for use in a variety of fields of study in the visible and near-infrared regions of the spectrum.We will present data from calibration targets and some applications, results of the spectral calibration of a spectrometer system, and results of environmental (vibration, radiation, shock, and thermal) testing. Data acquisition and system design are also discussed.

  17. A Bragg grating tunable filter based on temperature control system to demodulate a voltage sensor

    NASA Astrophysics Data System (ADS)

    Ribeiro, Bessie A.; Werneck, Marcelo M.; de Nazaré, Fabio B. V.; Gonçalves, Marceli N.

    2015-09-01

    This work presents an innovative automated Fiber Bragg Grating (FBG) based tunable optical filter (TOF) controlled by temperature to be used in temperature compensating schemes in FBG sensing set-ups. Mechanical and electronic aspects are discussed, and the implemented FBG-TOF viability and reliability in sensing systems are showed. The system was employed to demodulate a high voltage AC signal applied to a FBG-PZT sensor, showing good linearity and sensitivity.

  18. Mid infra-red hyper-spectral imaging with bright super continuum source and fast acousto-optic tuneable filter for cytological applications.

    NASA Astrophysics Data System (ADS)

    Farries, Mark; Ward, Jon; Valle, Stefano; Stephens, Gary; Moselund, Peter; van der Zanden, Koen; Napier, Bruce

    2015-06-01

    Mid-IR imaging spectroscopy has the potential to offer an effective tool for early cancer diagnosis. Current development of bright super-continuum sources, narrow band acousto-optic tunable filters and fast cameras have made feasible a system that can be used for fast diagnosis of cancer in vivo at point of care. The performance of a proto system that has been developed under the Minerva project is described.

  19. Polarization independent, integrated optical, acoustically tunable wavelength filters/switches with tapered acoustical directional coupler

    NASA Astrophysics Data System (ADS)

    Herrmann, H.; Schaefer, K.; Sohler, W.

    1994-11-01

    Enhanced sidelobe suppression of the filter characteristics of tunable acousto-optical mode converters in LiNbO3 has been achieved using for the first time tapered acoustical directional couplers. A sidelobe suppression of more than 15.5 dB could be demonstrated in a single stage device. By combining the mode converter with two integrated optical polarization splitters a polarization independent filter/wavelength selective switch has been fabricated with less than 3 dB intrinsic insertion loss, a polarization dependence of less than 1 dB, and a sidelobe suppression exceeding 14 dB.

  20. Study on spectrally agile staring sensor using acousto-optic tunable filter

    NASA Astrophysics Data System (ADS)

    Cui, Yan; Zhang, Minghui

    1992-08-01

    The spectrally agile staring sensor (SASS) is an instrument system that is able to get image and spectrum information. This paper analyzes the expression of signal-to-noise ratio and overall performance of the SASS system that uses an acousto-optic tunable filter as its spectral filter, and points out improving methods and limiting factors of the system performance. The complete SASS system experimental set-up is constructed. Using this set-up, the theory is verified, and the image and spectrum information of the simulated target is acquired.

  1. Wavelength-selective orbital-angular-momentum beam generation using MEMS tunable Fabry-Perot filter.

    PubMed

    Paul, Sujoy; Lyubopytov, Vladimir S; Schumann, Martin F; Cesar, Julijan; Chipouline, Arkadi; Wegener, Martin; Küppers, Franko

    2016-07-15

    We demonstrate an on-chip device capable of wavelength-selective generation of vortex beams, which is realized by a spiral phase plate integrated onto a microelectromechanical system (MEMS) tunable filter. This vortex MEMS filter, being capable of functioning simultaneously in both wavelength and orbital-angular-momentum (OAM) domains at the 1550 nm wavelength regime, is considered as a compact, robust, and cost-effective solution for simultaneous OAM- and wavelength-division multiplexed optical communications. The experimental OAM spectra for azimuthal orders 1, 2, and 3 show an OAM state purity >92% across a wavelength range of more than 30 nm. PMID:27420507

  2. Tunable microwave band-stop filters using ferromagnetic resonance

    NASA Astrophysics Data System (ADS)

    Zhao, Baolin; Shi, Yu; Zhong, Hui; Wang, Hualei

    2008-02-01

    In this paper, we present some results on FeCoB-based microwave band-stop filters. These structures, prepared on GaAs substrates, are compatible in size and growth process with on-chip high-frequency electronics. The band-stop filters have been realized with microstrips which incorporate ferromagnetic and dielectric layers to absorb microwave energy at the ferromagnetic resonance (FMR) frequency. The absorption notch in transmission can be tuned to various frequencies by varying an external applied magnitic field. For our devices, which incorporate FeCoB as the ferromagnetic material, the resultant FMR frequencies range from 12-22 GHz for applied fields up to only 1000 Oe. Comparatively, the frequency range of those devices using permalloy and Fe is substantially lower than FeCoB-based devices for applied the same fields. We constructed devices using monocrystalline FeCoB films grown in a sputtering system. Our devices are of different construction than other dielectric microstrips and show much improvement in terms of notch width and depth. The maximum attenuations of 3.5 dB/cm and 90dB/cm are observed respectively in two different structures.

  3. Spectral imaging characterization of quartz MOEM tunable Fabry-Perot filter

    NASA Astrophysics Data System (ADS)

    Gupta, Neelam; Tan, Songsheng

    2012-07-01

    Recently, prototype MOEM tunable Fabry-Perot filters operating from 400 to 800 nm were fabricated under a program to design miniature hyperspectral imagers operating from the visible to the longwave infrared. The filter design uses two semitransparent 30 nm thick silver-film mirrors, one fixed and the other moving, on a low-cost thin commercial quartz substrate. The moving mirror is supported by three leaf spring arms, which are fabricated by wet etching of the quartz substrate. The tuning of the transmitted wavelength of light from the filter is achieved by electrostatically actuating the moving mirror to vary the distance between the two mirrors. The size of the device is 18×24 mm2. The fixed part has a 6 mm diameter mirror and three electrodes to apply voltages, and the moving mirror is used as a ground electrode. Au bumps deposited on both parts control the initial air gap distance, and an Au-Au bonding is used to bond the two parts together. The spectral imaging performance of the MOEM filter is characterized using a spectrally tunable source and a CCD camera with suitable optics. The authors present a brief description of the filter, its characteristics, spectral imaging characterization experiment and results.

  4. JPL activities on development of acousto-optic tunable filter imaging spectrometer

    NASA Technical Reports Server (NTRS)

    Cheng, Li-Jen; Chao, Tien-Hsin; Reyes, George

    1992-01-01

    Recent activities of JPL in the development of a new type of imaging spectrometers for earth observation and planetary exploration are reported. This instrument uses the acousto-optic tunable filter (AOTF) as high resolution and fast programmable bandpass filter. AOTF operates in the principle of acousto-optic interaction in an anisotropic medium. This filter can be tuned in sequential, random, and multiwavelength access modes, providing observational flexibility. The diffraction process in the filter generates two diffracted monochromatic beams with polarization orthogonal to each other, creating a unique capability to measure both polarimetric and spectral properties of the incoming light simultaneously with a single instrument. The device gives wide wavelength operations with reasonably large throughput. In addition, it is in a compact solid-state structure without moving parts, providing system reliability. These attractive features give promising opportunities to develop a new generation of airborne/spaceborne and ground, real-time, imaging spectrometer systems for remote sensing applications.

  5. All-fiber widely wavelength-tunable thulium-doped fiber ring laser incorporating a Fabry-Perot filter

    NASA Astrophysics Data System (ADS)

    Wei, Y.; Hu, K.; Sun, B.; Wang, T.

    2012-04-01

    We demonstrate 1940 to 2010 nm continuous CW wavelength-tuning in a thulium-doped fiber laser (TDFL), using only fiber-format components. A fiber Fabry-Perot (FP) tunable filter is employed to achieve the wavelength tunability of 70 nm. By imposing a 200 Hz triangle wave signal on the filter, rapid wavelength-sweeping is demonstrated from 1952 to 1992 nm every 5 ms, corresponding to 8 nm/ms. This all-fiber wavelength-tunable and swept laser may find applications such as gas monitoring in the wavelength region of 2 μm.

  6. Fiber Fabry-Perot tunable filter for high-speed optical packet switching

    SciTech Connect

    Taranenko, N.L.; Tenbrink, S.C.; Hsu, K.; Miller, C.M.

    1997-01-01

    Tunable optical filters are important building blocks for All-Optical systems and networks. Fast optical tuning in several microseconds is necessary to perform high-speed optical packet switching. Multi- Gigabit/sec packet-switching will provide flexibility and higher network throughput when large numbers of users communicate simultaneously. One approach to achieve fast wavelength tuning is to use high-speed piezoelectrically-driven Fiber Fabry-Perot tunable filters (FFP-TFs). The requirement for tuning in microseconds raises a whole new set of challenges, such as ringing, thermostability and mechanical inertia control. It was shown that correlation between the mechanical resonance and optical response of the filter is important for the filter`s speed and for mounting hardware and control circuitry optimization. These features together with the FFP-TF`s high capacitance (approximately 0.25-0.5 microfarad) are being folded into building a special controller to substantially improve the shape of the driving signal and the response of the filter. The resultant controller enables tuning the high-speed FFP-TF three-orders-of- magnitude faster than that possible with standard commercial FFP-TFS. The fastest switching time achieved is 2.5 microseconds. As the result, a new packet-switched media access control protocol is being designed to minimize the searching time. The filter scans only once through the entire optical region and then tunes to all the required channels one after another in a few microseconds. It can help update Rainbow-2 Broadcast-and-Select High-Speed Wavelength Division Multiplexing All-Optical network that currently has a circuit- switched protocol using standard FFP-TFS.

  7. Compressed Sensing/Sparse-Recovery Approach for Improved Range Resolution in Narrow-Band Radar

    PubMed Central

    Costanzo, Sandra

    2016-01-01

    A compressed sensing/sparse-recovery procedure is adopted to obtain enhanced range resolution capability from the processing of data acquired with narrow-band SFCW radars. A mathematical formulation for the proposed approach is reported and validity limitations are fully discussed, by demonstrating the ability to identify a great number of targets, up to 20, in the range direction. Both numerical and experimental validations are presented, by assuming also noise conditions. The proposed method can be usefully applied for the accurate detection of parameters with very small variations, such as those involved in the monitoring of soil deformations or biological objects. PMID:27022617

  8. AGAR-AGAR: a high-efficiency narrow-band imager for ELTs

    NASA Astrophysics Data System (ADS)

    Tresoldi, Daniela; Felletti, Riccardo; Bianco, Andrea; Conconi, Paolo; De Caprio, Vincenzo; Crimi, Giuseppe; Molinari, Emilio; Riva, Alberto; Riva, Marco; Spanò, Paolo; Tintori, Matteo; Toso, Giorgio; Zerbi, Filippo M.

    2006-06-01

    The thinking about possible instruments for the future ELTs has just started and the current phase allows to pursue non-traditional solutions. Following the guidelines of the Science Case for an ELT 1,2 our team searched for possible intersections with innovative technologies we currently deal with in our research. We found that Volume Phase Holographic Gratings and advanced dichroics could be suited to design a non-traditional narrow band imager. We propose in this paper a comparative analysis of a VPHG based and a dichroic based configurations for the imager.

  9. Variations in the wide band and narrow band beams for NuMI

    SciTech Connect

    Malensek, A.J.

    1997-06-02

    This paper is directed at studies related to using the main injector at Fermilab to generate neutrino beams. The note describes two studies that have been done on variations of the reference beams. The first suggests a method to reduce the low-energy tail of the narrow band beam (NBB); the second addresses possibilities for minimizing the far/near variations in the spectra for the wide band beam (WBB). Both of these are studied with NUADA (Long Baseline) and are meant to give guidance for GEANT calculations that would be able to answer whether the suggested ideas are in fact improvements, once all the complex processes are included.

  10. Single-Crystal Semiconductors with Narrow Band Gaps for Solar Water Splitting.

    PubMed

    Wang, Tuo; Gong, Jinlong

    2015-09-01

    Solar water splitting provides a clean and renewable approach to produce hydrogen energy. In recent years, single-crystal semiconductors such as Si and InP with narrow band gaps have demonstrated excellent performance to drive the half reactions of water splitting through visible light due to their suitable band gaps and low bulk recombination. This Minireview describes recent research advances that successfully overcome the primary obstacles in using these semiconductors as photoelectrodes, including photocorrosion, sluggish reaction kinetics, low photovoltage, and unfavorable planar substrate surface. Surface modification strategies, such as surface protection, cocatalyst loading, surface energetics tuning, and surface texturization are highlighted as the solutions. PMID:26227831

  11. Measurement of the surface wavelength distribution of narrow-band radiation by a colorimetric method

    SciTech Connect

    Kraiskii, A V; Mironova, T V; Sultanov, T T

    2010-09-10

    A method is suggested for determining the wavelength of narrow-band light from a digital photograph of a radiating surface. The digital camera used should be appropriately calibrated. The accuracy of the wavelength measurement is better than 1 nm. The method was tested on the yellow doublet of mercury spectrum and on the adjacent continuum of the incandescent lamp radiation spectrum. By means of the method suggested the homogeneity of holographic sensor swelling was studied in stationary and transient cases. (laser applications and other topics in quantum electronics)

  12. Narrow-band erbium-doped fibre linear–ring laser

    SciTech Connect

    Kolegov, A A; Sofienko, G S; Minashina, L A; Bochkov, A V

    2014-01-31

    We have demonstrated a narrow-band linear – ring fibre laser with an output power of 15 mW at a wavelength of 1.55 μm and an emission bandwidth less than 5 kHz. The laser frequency is stabilised by an unpumped active fibre section and fibre Bragg grating. The fibre laser operates in a travelling wave mode, which allows the spatial hole burning effect to be avoided. At a certain pump power level, the laser switches from continuous mode to repetitivepulse operation, corresponding to relaxation oscillations. (control of laser radiation parameters)

  13. Effect of timing noise on targeted and narrow-band coherent searches for continuous gravitational waves from pulsars

    NASA Astrophysics Data System (ADS)

    Ashton, G.; Jones, D. I.; Prix, R.

    2015-03-01

    Most searches for continuous gravitational waves from pulsars use Taylor expansions in the phase to model the spin-down of neutron stars. Studies of pulsars demonstrate that their electromagnetic (EM) emissions suffer from timing noise, small deviations in the phase from Taylor expansion models. How the mechanism producing EM emission is related to any continuous gravitational-wave (CW) emission is unknown; if they either interact or are locked in phase, then the CW will also experience timing noise. Any disparity between the signal and the search template used in matched filtering methods will result in a loss of signal-to-noise ratio, referred to as "mismatch." In this work we assume the CW suffers a level of timing noise similar to its EM counterpart. We inject and recover fake CW signals, which include timing noise generated from observational data on the Crab pulsar. Measuring the mismatch over durations of order ˜10 months, the effect is, for the most part, found to be small. This suggests recent so-called "narrow-band" searches which placed upper limits on the signals from the Crab and Vela pulsars will not be significantly affected. At a fixed observation time, we find the mismatch depends upon the observation epoch. Considering the averaged mismatch as a function of observation time, we find that it increases as a power law with time, and so may become relevant in long baseline searches.

  14. Effect of metal coating in all-fiber acousto-optic tunable filter using torsional wave.

    PubMed

    Song, Du-Ri; Jun, Chang Su; Do Lim, Sun; Kim, Byoung Yoon

    2014-12-15

    Torsional mode acousto-optic tunable filter (AOTF) is demonstrated using a metal-coated birefringent optical fiber for an improved robustness. The changes in acoustic and optical properties of a metal-coated birefringent optical fiber induced by the thin metal coating were analyzed experimentally and theoretically. The filter wavelength shift is successfully explained as a result of combined effect of acoustic wavelength change and optical birefringence change. We also demonstrated a small form-factor configuration by coiling the fiber with 6 cm diameter without performance degradation. The center wavelength of the filter can be tuned >35 nm by changing the applied frequency, and the coupling efficiency is higher than 92% with <5 nm 3-dB bandwidth. PMID:25607036

  15. Double channel mechanically tunable terahertz filter based on parallel plate waveguide cavities

    NASA Astrophysics Data System (ADS)

    Chen, Lin; Zhu, Yiming

    2012-12-01

    Theoretical and experimental works were carried out on a double channel mechanically tunable terahertz filter integrated with parallel plate waveguide cavities. The filter includes two rectangular grooves on upper and bottom plates of waveguide, respectively. The filter frequencies can be quasilinearly tuned by altering the overlap length between two rectangle grooves on metal plates. From the experiment, we found low (high) resonant frequency can be adjusted from 0.417(0.346) THz to 0.399(0.374) THz when the overlap length is altered from 0 to 500 μm, respectively. The Q values can reach 46 with the resonant frequency (0.41THz), overlap length (220 μm) and waveguide spacing (650 μm). Theoretical results show good agreement with experiment.

  16. Tunable and reconfigurable multi-tap microwave photonic filter based on dynamic Brillouin gratings in fibers.

    PubMed

    Sancho, J; Primerov, N; Chin, S; Antman, Y; Zadok, A; Sales, S; Thévenaz, L

    2012-03-12

    We propose and experimentally demonstrate new architectures to realize multi-tap microwave photonic filters, based on the generation of a single or multiple dynamic Brillouin gratings in polarization maintaining fibers. The spectral range and selectivity of the proposed periodic filters is extensively tunable, simply by reconfiguring the positions and the number of dynamic gratings along the fiber respectively. In this paper, we present a complete analysis of three different configurations comprising a microwave photonic filter implementation: a simple notch-type Mach-Zehnder approach with a single movable dynamic grating, a multi-tap performance based on multiple dynamic gratings and finally a stationary grating configuration based on the phase modulation of two counter-propagating optical waves by a common pseudo-random bit sequence (PRBS). PMID:22418495

  17. Photothermally tunable silicon-microring-based optical add-drop filter through integrated light absorber.

    PubMed

    Chen, Xi; Shi, Yuechun; Lou, Fei; Chen, Yiting; Yan, Min; Wosinski, Lech; Qiu, Min

    2014-10-20

    An optically pumped thermo-optic (TO) silicon ring add-drop filter with fast thermal response is experimentally demonstrated. We propose that metal-insulator-metal (MIM) light absorber can be integrated into silicon TO devices, acting as a localized heat source which can be activated remotely by a pump beam. The MIM absorber design introduces less thermal capacity to the device, compared to conventional electrically-driven approaches. Experimentally, the absorber-integrated add-drop filter shows an optical response time of 13.7 μs following the 10%-90% rule (equivalent to a exponential time constant of 5 μs) and a wavelength shift over pump power of 60 pm/mW. The photothermally tunable add-drop filter may provide new perspectives for all-optical routing and switching in integrated Si photonic circuits. PMID:25401557

  18. Compact tunable multibandpass filters based on liquid-filled photonic crystal fibers.

    PubMed

    Liu, Yingjie; Wang, Yiping; Sun, Bing; Liao, Changrui; Song, Jun; Yang, Kaiming; Wang, Guanjun; Wang, Qiao; Yin, Guolu; Zhou, Jiangtao

    2014-04-01

    We demonstrated a compact tunable multibandpass filter with a short size of about 9 mm and a high wavelength-tuning sensitivity of up to -2.194  nm/°C by means of filling a liquid with a high refractive index of 1.700 into the air holes of a photonic crystal fiber (PCF). Such a PCF-based filter maintains an almost constant bandwidth and a large extinction ratio of more than 40 dB within the whole wavelength tuning range of more than 100 nm. Moreover, the transmission spectrum of the PCF-based filter is insensitive to the stretch force and the curvature of the fiber. PMID:24686697

  19. 33 W quasi-continuous-wave narrow-band sodium D2a laser by sum-frequency generation in LBO

    NASA Astrophysics Data System (ADS)

    Wang, Peng-Yuan; Xie, Shi-Yong; Bo, Yong; Wang, Bao-Shan; Zuo, Jun-Wei; Wang, Zhi-Chao; Shen, Yu; Zhang, Feng-Feng; Wei, Kai; Jin, Kai; Xu, Yi-Ting; Xu, Jia-Lin; Peng, Qin-Jun; Zhang, Jing-Yuan; Lei, Wen-Qiang; Cui, Da-Fu; Zhang, Yu-Dong; Xu, Zu-Yan

    2014-09-01

    We demonstrate an all-solid quasi-continuous-wave (QCW) narrow-band source tunable to sodium D2a line at 589.159 nm. The source is based on sum-frequency mixing between lasers at 1064 nm and 1319 nm in a LBO crystal. The 1064 nm and 1319 nm lasers are produced from two diode side-pumped Nd:YAG master oscillator power amplifier (MOPA) laser systems, respectively. A 33 W output of 589 nm laser is obtained with beam quality factor M2 = 1.25, frequency stability better than ±0.2 GHz and linewidth less than 0.44 GHz. A prototype 589 nm laser system is assembled, and a sodium laser guided star has been successfully observed in the field test.

  20. A Cooperative Distance Learning Method based on the Narrow-band Internet and Its Evaluation

    NASA Astrophysics Data System (ADS)

    Tilwaldi, Dilmurat; Takahashi, Toshiya; Takata, Akinobu; Koizumi, Hisao

    This paper describes the experimental evaluation of a cooperative distance learning method, which can be utilized on the narrow-band Internet. In this method, students of group-learning perform a series of study a couple of times, which create an on-line report, communicating through the chat about given theme. they try to gain improvement in the study effect with higher cooperative attitude. Teacher gives a short lecture at the first stage, and then gives supplementary explanation after grasping the degree of comprehension of students at the middle stage of the study. Teaching materials are distributed to students' PCs beforehand and the lecture could be carried out on the narrow-band environment by transmitting the commands. The teacher analyzes students' communication logs and gives advice for the next study. This paper describes the result of the evaluation of the proposed method by carrying out simulated installation of the environment within the campus supposing a trial of cooperative distance learning in overseas desert circumference area environment.

  1. Flow-radiation coupling for atmospheric entries using a Hybrid Statistical Narrow Band model

    NASA Astrophysics Data System (ADS)

    Soucasse, Laurent; Scoggins, James B.; Rivière, Philippe; Magin, Thierry E.; Soufiani, Anouar

    2016-09-01

    In this study, a Hybrid Statistical Narrow Band (HSNB) model is implemented to make fast and accurate predictions of radiative transfer effects on hypersonic entry flows. The HSNB model combines a Statistical Narrow Band (SNB) model for optically thick molecular systems, a box model for optically thin molecular systems and continua, and a Line-By-Line (LBL) description of atomic radiation. Radiative transfer calculations are coupled to a 1D stagnation-line flow model under thermal and chemical nonequilibrium. Earth entry conditions corresponding to the FIRE 2 experiment, as well as Titan entry conditions corresponding to the Huygens probe, are considered in this work. Thermal nonequilibrium is described by a two temperature model, although non-Boltzmann distributions of electronic levels provided by a Quasi-Steady State model are also considered for radiative transfer. For all the studied configurations, radiative transfer effects on the flow, the plasma chemistry and the total heat flux at the wall are analyzed in detail. The HSNB model is shown to reproduce LBL results with an accuracy better than 5% and a speed up of the computational time around two orders of magnitude. Concerning molecular radiation, the HSNB model provides a significant improvement in accuracy compared to the Smeared-Rotational-Band model, especially for Titan entries dominated by optically thick CN radiation.

  2. In vivo early diagnosis of gastric dysplasia using narrow-band image-guided Raman endoscopy

    NASA Astrophysics Data System (ADS)

    Huang, Zhiwei; Bergholt, Mads Sylvest; Zheng, Wei; Lin, Kan; Ho, Khek Yu; Teh, Ming; Yeoh, Khay Guan

    2010-05-01

    We first report on the implementation of a novel narrow-band image-guided Raman endoscopy technique for in vivo diagnosis of gastric dysplasia. High-quality in vivo Raman spectra can be acquired from normal and dysplastic gastric mucosal tissue within 0.5 sec under narrow-band image (NBI) guidance at gastroscopy. Significant differences are observed in in vivo Raman spectra between normal (n=54) and dysplastic (n=18) gastric tissue from 30 gastric patients, particularly in the spectral ranges of 825 to 950, 1000 to 1100, 1250 to 1500, and 1600 to 1800 cm-1, which primarily contain signals related to proteins, nucleic acids, and lipids. The multivariate analysis [i.e., principal components analysis (PCA) and linear discriminant analysis (LDA)], together with the leave-one tissue site-out, cross validation on in vivo gastric Raman spectra yields a diagnostic sensitivity of 94.4% (17/18) and specificity of 96.3% (52/54) for distinction of gastric dysplastic tissue. This study suggests that narrowband image-guided Raman endoscopy associated with PCA-LDA diagnostic algorithms has potential for the noninvasive, in vivo early diagnosis and detection of gastric precancer during clinical gastroscopic examination.

  3. Progress in the Search for Ultra-Narrow Band Extraterrestrial Artificial

    NASA Astrophysics Data System (ADS)

    Lemarchand, Guillermo

    Project META II (Megachannel Extra Terrestrial Assay), a full-sky survey for artificial ultra-narrow-band signals, has been conducted in Argentina, since October 1990, from one of the two 30-m radiotelescopes of the Instituto Argentino de Radioastronomia (IAR). The search was performed near the 1.4 GHz line of neutral hydrogen, using an 8.4 times 10^6 channel Fourier spectrometer of 0.05 Hz spectral resolution and 400 kHz of instantaneous bandwidth. The observing frequency was corrected both for motions with respect to three astronomical inertial frames, and for the effect of Earth's rotation, which provides a characteristic changing signature for narrow-band signals of extraterrestrial origin. In 1996, with the economical sponsorship of The Planetary Society, an up-grade of the original META data acquisition system was made. New hardware was installed and new software was developed allowing a more comprehensive data analysis of the detected signals. The search was expanded to the 1.667 and 3.3 GHz observing frequencies. A description of the new system's characteristics as well

  4. Minority carrier blocking to enhance the thermoelectric figure of merit in narrow-band-gap semiconductors

    NASA Astrophysics Data System (ADS)

    Bahk, Je-Hyeong; Shakouri, Ali

    2016-04-01

    We present detailed theoretical predictions on the enhancement of the thermoelectric figure of merit by minority carrier blocking with heterostructure barriers in bulk narrow-band-gap semiconductors. Bipolar carrier transport, which is often significant in a narrow-band-gap material, is detrimental to the thermoelectric energy conversion efficiency as it suppresses the Seebeck coefficient and increases the thermal conductivity. When the minority carriers are selectively prevented from participating in conduction while the transport of majority carriers is relatively unaffected by one-sided heterobarriers, the thermoelectric figure of merit can be drastically enhanced. Thermoelectric transport properties such as Seebeck coefficient, electrical conductivity, and electronic thermal conductivity including the bipolar term are calculated with and without the barriers based on the near-equilibrium Boltzmann transport equations under the relaxation time approximation to investigate the effects of minority carrier barriers on the thermoelectric figure of merit. For this, we provide details of carrier transport modeling and fitting results of experimental data for three important material systems, B i2T e3 -based alloys, M g2S i1 -xS nx , and S i1 -xG ex , that represent, respectively, near-room-temperature (300 K-500 K), midtemperature (600 K-900 K), and high-temperature (>1000 K ) applications. Theoretical maximum enhancement of thermoelectric figure of merit that can be achieved by minority carrier blocking is quantified and discussed for each of these semiconductors.

  5. Narrow-band N-resonance formed in thin rubidium atomic layers

    SciTech Connect

    Sargsyan, A.; Mirzoyan, R.; Sarkisyan, D.

    2012-11-15

    The narrow-band N-resonance formed in a {Lambda} system of D{sub 1}-line rubidium atoms is studied in the presence of a buffer gas (neon) and the radiations of two continuous narrow-band diode lasers. Special-purpose cells are used to investigate the dependence of the process on vapor column thickness L in millimeter, micrometer, and nanometer ranges. A comparison of the dependences of the N-resonance and the electromagnetically induced transparency (EIT) resonance on L demonstrates that the minimum (record) thickness at which the N-resonance can be detected is L = 50 {mu}m and that a high-contrast EIT resonance can easily be formed even at L Almost-Equal-To 800 nm. The N-resonance in a magnetic field for {sup 85}Rb atoms is shown to split into five or six components depending on the magnetic field and laser radiation directions. The results obtained indicate that levels F{sub g} = 2, 3 are initial and final in the N-resonance formation. The dependence of the N-resonance on the angle between the laser beams is analyzed, and practical applications are noted.

  6. Observation of tunable nonlinear effects in an analogue of superconducting composite right/left hand filter.

    PubMed

    Liu, Haiwen; Lei, Jiuhuai; Jiang, Hao; Guan, Xuehui; Ji, Laiyun; Ma, Zhewang

    2015-01-01

    Artificial structures with negative permittivity or permeability have attracted significant attention in the science community because they provide a pathway for obtaining exotic electromagnetic properties not found in natural materials. At the moment, the great challenge of these artificial structures in microwave frequency exhibits a relatively large loss. It is well-known that superconducting thin films have extremely low surface resistance. Hence, it is a good candidate to resolve this constraint. Besides, the reported artificial structures with negative permittivity or permeability are mainly focusing on linear regime of wave propagation. However, any future effort in creating tunable structures would require knowledge of nonlinear properties. In this work, a tunable superconducting filter with composite right/left-hand transmission property is proposed and fabricated. Its nonlinear effects on temperature and power are studied by theoretical analysis and experiments. PMID:26442447

  7. Observation of tunable nonlinear effects in an analogue of superconducting composite right/left hand filter

    PubMed Central

    Liu, Haiwen; Lei, Jiuhuai; Jiang, Hao; Guan, Xuehui; Ji, Laiyun; Ma, Zhewang

    2015-01-01

    Artificial structures with negative permittivity or permeability have attracted significant attention in the science community because they provide a pathway for obtaining exotic electromagnetic properties not found in natural materials. At the moment, the great challenge of these artificial structures in microwave frequency exhibits a relatively large loss. It is well-known that superconducting thin films have extremely low surface resistance. Hence, it is a good candidate to resolve this constraint. Besides, the reported artificial structures with negative permittivity or permeability are mainly focusing on linear regime of wave propagation. However, any future effort in creating tunable structures would require knowledge of nonlinear properties. In this work, a tunable superconducting filter with composite right/left-hand transmission property is proposed and fabricated. Its nonlinear effects on temperature and power are studied by theoretical analysis and experiments. PMID:26442447

  8. A Novel K-Band Tunable Microstrip Bandpass Filter Using a Thin Film HTS/Ferroelectric/ Dielectric Configuration

    NASA Technical Reports Server (NTRS)

    Subramanyam, G.; VanKeuls, F.; Miranda, F. A.

    1998-01-01

    We report on YBCO/strontium titanate (STO) thin film K-band tunable bandpass filters on lanthanum aluminate substrates. The 2 pole filters were designed for a center frequency of 19 GHz and 4% bandwidth. Tunability is achieved through the non-linear dc electric field dependence of the relative dielectric constant of STO (epsilon-rSTO). Center frequency shifts greater than 2 GHz were obtained at a 400V bipolar dc bias at temperatures below 77K, with minimum degradation in the insertion loss of the filters.

  9. Assessment of low-frequency hearing with narrow-band chirp-evoked 40-Hz sinusoidal auditory steady-state response.

    PubMed

    Wilson, Uzma S; Kaf, Wafaa A; Danesh, Ali A; Lichtenhan, Jeffery T

    2016-01-01

    Objective To determine the clinical utility of narrow-band chirp-evoked 40-Hz sinusoidal auditory steady state responses (s-ASSR) in the assessment of low-frequency hearing in noisy participants. Design Tone bursts and narrow-band chirps were used to respectively evoke auditory brainstem responses (tb-ABR) and 40-Hz s-ASSR thresholds with the Kalman-weighted filtering technique and were compared to behavioral thresholds at 500, 2000, and 4000 Hz. A repeated measure ANOVA and post-hoc t-tests, and simple regression analyses were performed for each of the three stimulus frequencies. Study sample Thirty young adults aged 18-25 with normal hearing participated in this study. Results When 4000 equivalent response averages were used, the range of mean s-ASSR thresholds from 500, 2000, and 4000 Hz were 17-22 dB lower (better) than when 2000 averages were used. The range of mean tb-ABR thresholds were lower by 11-15 dB for 2000 and 4000 Hz when twice as many equivalent response averages were used, while mean tb-ABR thresholds for 500 Hz were indistinguishable regardless of additional response averaging. Conclusion Narrow-band chirp-evoked 40-Hz s-ASSR requires a ∼15 dB smaller correction factor than tb-ABR for estimating low-frequency auditory threshold in noisy participants when adequate response averaging is used. PMID:26795555

  10. Tunable spin filter and molecular hybridization in a quantum dot molecule

    NASA Astrophysics Data System (ADS)

    Mireles, F.; Ulloa, S. E.

    2005-03-01

    Spin filtering using few electron semiconductor quantum dots formed in two-dimensional electron gas systems has attracted much recent attention in spintronics. Spin filtering has been achieved in a quantum dot via universal conductance fluctuations and electron magnetic focusing [1]. A bipolar spin filter (SF) has been realized recently using a semiconductor quantum dot which can operate practically as a perfect SF, provided there is a large enough Zeeman splitting [2]. In this work we present calculations showing that the tunable (molecular) hybridization between two quantum dots with few electrons and connected ``in parallel,'' produces a singlet-triplet transition in the ground state which can be used as a robust bipolar SF in both the linear and non-linear regimes of transport. The bipolar SF is found to be fully tunable by only electrical gating at low temperatures. We show that a singlet-triplet transition in the energy spectrum gives rise to the natural spin selectivity in the odd-to-even electron number transition in Coulomb blockade experiments. The competition between the Zeeman, Coulomb, and tunneling energies is studied in detail to determine the optimal conditions to achieve the singlet-triplet transition, so that it becomes broadly useful as a bipolar SF. [1] J. A. Folk et al., Science 299, 679 (2003). [2] R. Hanson et al., cond-mat/0311414 (2003). *Supported by DGAPA-UNAM project 1N114403, CONACYT, projects J40521F and 143673F, and NSF-IMC.

  11. A Tunable Lyot Filter at Prime Focus: a Method for Tracing Supercluster Scales at z ~ 1

    NASA Astrophysics Data System (ADS)

    Bland-Hawthorn, J.; van Breugel, W.; Gillingham, P. R.; Baldry, I. K.; Jones, D. H.

    2001-12-01

    Tunable narrowband emission line surveys have begun to show the ease with which star-forming galaxies can be identified in restricted redshift intervals to z~5 with a 4 m class telescope. These surveys have been carried out with imaging systems at the Cassegrain or Nasmyth focus, and are therefore restricted to fields smaller than 10'. We now show that tunable narrowband imaging is possible over a 30' field with a high-performance Lyot filter placed directly in front of a CCD mosaic at the prime focus. Our design is intended for the f/3.3 prime focus of the Anglo-Australian Telescope (AAT) 3.9 m, although similar devices can be envisaged for the Subaru 8 m (f/2), Palomar 5 m (f/3.4), Visible and Infrared Survey Telescope for Astronomy (VISTA) 4 m (f/6), Mayall 4 m (f/2.6), or the Canada-France-Hawaii Telescope (CFHT) 3.6 m (f/4). A modified Wynne doublet ensures subarcsecond performance over the field. In combination with the new Wide-Field Imager 8k×8k mosaic (WFI) at the AAT, the overall throughput (35%) of the system to unpolarized light is expected to be comparable to the TAURUS Tunable Filter (TTF). Unlike the TTF, the field is fully monochromatic, and the instrumental profile has much better wing suppression. For targeted surveys of emission line sources at z~1, a low-resolution (R~150 at 550 nm) Lyot filter on a 4 m telescope is expected to be comparable or superior to current instruments on 8-10 m class telescopes. We demonstrate that the 30' field is well matched to superclusters at these redshifts, such that large-scale structure should be directly observable.

  12. Compact spectrophotometer using polarization-independent liquid crystal tunable optical filters

    NASA Astrophysics Data System (ADS)

    Nicolescu, Elena; Escuti, Michael J.

    2007-09-01

    We introduce and demonstrate a simple spectrophotometer system insensitive to input polarization and with strong potential for compact and low-cost implementation. This technology has a wide variety of potential applications ranging from astronomy to medicine and even the cosmetics industry. To enable more powerful and portable microspectrometers we employ a novel design based on a tunable liquid crystal filter with polarization-independence, which is constructed of stacked liquid crystal polarization gratings (LCPGs). These switchable, anisotropic, thin diffraction gratings exhibit unique properties that include diffraction at visible and infrared wavelengths that can be coupled between only the zero- and first-orders (with nearly 100% and 0% experimentally verified efficiencies), depending on the applied voltage and wavelength of incident light. When combined with an elemental spatial filter, polarization-independent bandpass tuning can be achieved with minimum loss. Analogous to Lyot and Solc filters, several LCPGs are layered and introduced into a temporally resolved system using a single photodetector. The unique filter design enables improvement in terms of resolution and sensitivity by eliminating the polarization dependence present in all competing birefringence-based technologies. Also, the temporal detection system has a potential for improved miniaturization compared to any competing relevant approach and decreased cost by avoiding highly sensitive alignment, reflective diffraction components, Fabry- Perot cavities, and expensive detectors. In this work we describe the core principles of the tunable filter, present a representative spectrometer system design, report preliminary experimental data, and discuss the capabilities of the system in terms of spectral range, resolution, and sensitivity.

  13. A tunable and switchable single-longitudinal-mode dual-wavelength fiber laser with a simple linear cavity.

    PubMed

    He, Xiaoying; Fang, Xia; Liao, Changrui; Wang, D N; Sun, Junqiang

    2009-11-23

    A simple linear cavity erbium-doped fiber laser based on a Fabry-Perot filter which consists of a pair of fiber Bragg gratings is proposed for tunable and switchable single-longitudinal-mode dual-wavelength operation. The single-longitudinal-mode is obtained by the saturable absorption of an unpumed erbium-doped fiber together with a narrow-band fiber Bragg grating. Under the high pump power (>166 mW) condition, the stable dual-wavelength oscillation with uniform amplitude can be realized by carefully adjusting the polarization controller in the cavity. Wavelength selection and switching are achieved by tuning the narrow-band fiber Bragg grating in the system. The spacing of the dual-wavelength can be selected at 0.20 nm (approximately 25.62 GHz), 0.22 nm (approximately 28.19 GHz) and 0.54 nm (approximately 69.19 GHz). PMID:19997420

  14. A search for methane in the atmosphere of GJ 1214b via GTC narrow-band transmission spectrophotometry

    NASA Astrophysics Data System (ADS)

    Wilson, P. A.; Colón, K. D.; Sing, D. K.; Ballester, G. E.; Désert, J.-M.; Ehrenreich, D.; Ford, E. B.; Fortney, J. J.; Lecavelier des Etangs, A.; López-Morales, M.; Morley, C. V.; Pettitt, A. R.; Pont, F.; Vidal-Madjar, A.

    2014-03-01

    We present narrow-band photometric measurements of the exoplanet GJ 1214b using the 10.4 m Gran Telescopio Canarias and the Optical System for Imaging and low Resolution Integrated Spectroscopy instrument. Using tuneable filters, we observed a total of five transits, three of which were observed at two wavelengths nearly simultaneously, producing a total of eight individual light curves, six of these probed the possible existence of a methane absorption feature in the 8770-8850 Å region at high resolution. We detect no increase in the planet-to-star radius ratio across the methane feature with a change in radius ratio of Δ overline{R} = -0.0007 ± 0.0017 corresponding to a scaleheight (H) change of -0.5 ± 1.2H across the methane feature, assuming a hydrogen-dominated atmosphere. We find that a variety of water and cloudy atmospheric models fit the data well, but find that cloud-free models provide poor fits. These observations support a flat transmission spectrum resulting from the presence of a high-altitude haze or a water-rich atmosphere, in agreement with previous studies. In this study, the observations are pre-dominantly limited by the photometric quality and the limited number of data points (resulting from a long observing cadence), which make the determination of the systematic noise challenging. With tuneable filters capable of high-resolution measurements (R ≈ 600-750) of narrow absorption features, the interpretation of our results are also limited by the absence of high-resolution methane models below 1 μm.

  15. High-Order Tunable Filters Based on a Chain of Coupled Crystalline Whispering Gallery-Mode Resonators

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy A.; Ilchenko, Vladimir S.; Matsko, Andrey B.; Maleki, Lute

    2005-01-01

    We demonstrate experimentally a tunable third-order optical filter fabricated from the three voltage-controlled lithium niobate whispering gallery-mode resonators. The filter operates at 1550 nm with 30-MHz bandwidth and can be electrooptically tuned by 12 GHz in the linear regime with approximately 80-MHz/V tuning rate. With this filter, we have demonstrated 6-dB fiber-to-fiber insertion loss and 30-ns tuning speed, limited by the resonator buildup time.

  16. Dual-band bandpass tunable microwave photonic filter based on stimulated Brillouin scattering

    NASA Astrophysics Data System (ADS)

    Li, Jia-qi; Xiao, Yong-chuan; Dong, Wei; Zhang, Xin-dong

    2016-07-01

    A dual-band bandpass microwave photonic filter (MPF) based on stimulated Brillouin scattering (SBS) is theoretically analyzed and experimentally demonstrated. Two separated tunable laser sources (TLSs) are employed to generate two passbands by implementing phase modulation to amplitude modulation conversion by using SBS induced sideband amplification. The center frequencies of both passbands can be independently tuned ranging from 1 GHz to 19 GHz. High resolution with 3 dB bandwidth less than 30 MHz and large out-of-band rejection about 40 dB under 25 mW optical pump power are achieved.

  17. A tunable dye laser with a CaMoO4 acoustooptical filter

    NASA Astrophysics Data System (ADS)

    Mazur, M. M.; Makhmudov, Kh. M.; Pustovoit, V. I.

    1988-04-01

    A new optical scheme is proposed and an electronically tunable laser with a CaMoO4 acoustooptical filter (AOF) used as the dispersing element is experimentally tested. For rhodamine C dye, an emission wavelength tuning range of about 40 nm with a line width of 0.3 nm is obtained. Single and dual frequency operation is described. It is shown that the CaMoO4 AOF allows for laser operation with a driving RF power of 1 W, making it possible to use the laser in the CW mode.

  18. The Narrow Band AOTF Based Hyperspectral Microscopic Imaging on the Rat Skin Stratum Configuration

    NASA Astrophysics Data System (ADS)

    Zhang, C.; Wang, H.; Huang, J.; Gao, Q.

    2014-08-01

    A noncollinear acousto-optic tunable filter (AOTF) was designed with a comprehensive treatment of the properties of TeO2 as an acoustooptic (A-O) material. The results of optical testing validated that it predicted the performance of the designed AOTF. The bandwidth of the AOTF was very narrow in the visible light range. The high spectral resolution of AOTF was useful in practical applications to the hyperspectral imaging. The experimentally observed spectral pattern of the diffracted light was nearly the same as the theoretical result. The measured tuning relationship between the diffracted central optical wavelength and acoustic frequency was in accordance with the theoretical prediction. It demonstrates the accuracy of our design theory. Furthermore, by selecting the AOTF as the spectroscopic element, a hyperspectral microscopic imaging system was designed. The hyperspectral microscopic images of the rat skin tissue under the different optical center wavelength were acquired. The experimental results indicated that the imaging performance was satisfactory. The stratums of the rat skin can be clearly distinguished. The inner details of the epidermis and the corium can be shown on the hyperspectral microscopic images. Some differences also can be found by the comparison of the hyperspectal images under the different optical wavelengths. The study indicated the applicability and the advantage of our system on biomedicine area.

  19. Ultra-wideband ladder filter using SH(0) plate wave in thin LiNbO(3) plate and its application to tunable filter.

    PubMed

    Kadota, Michio; Tanaka, Shuji

    2015-05-01

    A cognitive radio terminal using vacant frequency bands of digital TV (DTV) channels, i.e., TV white space, strongly requires a compact tunable filter covering a wide frequency range of the DTV band (470 to 710 MHz in Japan). In this study, a T-type ladder filter using ultra-wideband shear horizontal mode plate wave resonators was fabricated, and a low peak insertion loss of 0.8 dB and an ultra-large 6 dB bandwidth of 240 MHz (41%) were measured in the DTV band. In addition, bandpass filters with different center frequencies of 502 and 653 MHz at 6 dB attenuation were numerically synthesized based on the same T-type ladder filter in conjunction with band rejection filters with different frequencies. The results suggest that the combination of the wideband T-type ladder filter and the band rejection filters connected with variable capacitors enables a tunable filter with large tunability of frequency and bandwidth as well as large rejection at the adjacent channels of an available TV white space. PMID:25965686

  20. Wavelength-tunable filter utilizing non-cyclic arrayed waveguide grating to create colorless, directionless, contentionless ROADMs

    NASA Astrophysics Data System (ADS)

    Niwa, Masaki; Takashina, Shoichi; Mori, Yojiro; Hasegawa, Hiroshi; Sato, Ken-ichi; Watanabe, Toshio

    2015-01-01

    With the continuous increase in Internet traffic, reconfigurable optical add-drop multiplexers (ROADMs) have been widely adopted in the core and metro core networks. Current ROADMs, however, allow only static operation. To realize future dynamic optical-network services, and to minimize any human intervention in network operation, the optical signal add/drop part should have colorless/directionless/contentionless (C/D/C) capabilities. This is possible with matrix switches or a combination of splitter-switches and optical tunable filters. The scale of the matrix switch increases with the square of the number of supported channels, and hence, the matrix-switch-based architecture is not suitable for creating future large-scale ROADMs. In contrast, the numbers of splitter ports, switches, and tunable filters increase linearly with the number of supported channels, and hence the tunable-filter-based architecture will support all future traffic. So far, we have succeeded in fabricating a compact tunable filter that consists of multi-stage cyclic arrayed-waveguide gratings (AWGs) and switches by using planar-lightwave-circuit (PLC) technologies. However, this multistage configuration suffers from large insertion loss and filter narrowing. Moreover, power-consuming temperature control is necessary since it is difficult to make cyclic AWGs athermal. We propose here novel tunable-filter architecture that sandwiches a single-stage non-cyclic athermal AWG having flatter-topped passbands between small-scale switches. With this configuration, the optical tunable filter attains low insertion loss, large passband bandwidths, low power consumption, compactness, and high cost-effectiveness. A prototype is monolithically fabricated with PLC technologies and its excellent performance is experimentally confirmed utilizing 80-channel 30-GBaud dual-polarization quadrature phase-shift-keying (QPSK) signals.

  1. Tailoring of the Brillouin gain for on-chip widely tunable and reconfigurable broadband microwave photonic filters.

    PubMed

    Choudhary, Amol; Aryanfar, Iman; Shahnia, Shayan; Morrison, Blair; Vu, Khu; Madden, Stephen; Luther-Davies, Barry; Marpaung, David; Eggleton, Benjamin J

    2016-02-01

    An unprecedented Brillouin gain of 44 dB in a photonic chip enables the realization of broadly tunable and reconfigurable integrated microwave photonic filters. More than a decade bandwidth reconfigurability from 30 up to 440 MHz, with a passband ripple <1.9  dB is achieved by tailoring the Brillouin pump. The filter central frequency is continuously tuned up to 30 GHz with no degradation of the passband response, which is a major improvement over electronic filters. Furthermore, we demonstrate pump tailoring to realize multiple bandpass filters with different bandwidths and central frequencies, paving the way for multiple on-chip microwave filters and channelizers. PMID:26907391

  2. Spin-wave band-pass filters based on yttrium iron garnet films for tunable microwave photonic oscillators

    NASA Astrophysics Data System (ADS)

    Ustinov, A. B.; Drozdovskii, A. V.; Nikitin, A. A.; Kalinikos, B. A.

    2015-12-01

    The paper reports on development of tunable band-pass microwave filters for microwave photonic generators. The filters were fabricated with the use of epitaxial yttrium iron garnet films. Principle of operation of the filters was based on excitation, propagation, and reception of spin waves. In order to obtain narrow pass band, the filtering properties of excitation and reception antennas were exploited. The filters demonstrated insertion losses of 2-3 dB, bandwidth of 25-35 MHz, and tuning range of up to 1.5 GHz in the range 3-7 GHz.

  3. Full-optical tunable add/drop filter based on nonlinear photonic crystal ring resonators

    NASA Astrophysics Data System (ADS)

    Mansouri-Birjandi, Mohammad Ali; Tavousi, Alireza; Ghadrdan, Majid

    2016-09-01

    Here, we propose a full-optical tunable Add/Drop filter based on single (SR) and double-vertically (DR) aligned Kerr-like nonlinear photonic crystal ring resonators (PCRRs). Silicon (Si) nano-crystal is used as the nonlinear material inside and outside of PCRRs. The minimum optical power required to turn-on/turn-off the SR and DR filters are 2000 mW/μm2, and 150 mW/μm2, respectively. We believe since the DR filter has a higher Q-factor rather than SR and also since the optical power reads more nonlinear rods with a longer time to pass the structure, thus the optical power required is much lower (10 folds). In addition, the minimum power required to 1 nm redshift the center operating wavelength of SR filter is 125 mW/μm2 (i.e. ΔnNL = 0.005) and for DR is as low as 8 mW/μm2. Performance of the Add/Drop filter structure is simulated by means of finite difference time domain (FDTD) method, in which the simulations showed an ultra-compact size structure with promising ultrafast tune-ability speeds.

  4. Deep-UV Based Acousto-Optic Tunable Filter for Spectral Sensing Applications

    NASA Technical Reports Server (NTRS)

    Prasad, Narasimha S.

    2006-01-01

    In this paper, recent progress made in the development of quartz and KDP crystal based acousto-optic tunable filters (AOTF) are presented. These AOTFs are developed for operation over deep-UV to near-UV wavelengths of 190 nm to 400 nm. Preliminary output performance measurements of quartz AOTF and design specifications of KDP AOTF are presented. At 355 nm, the quartz AOTF device offered approx.15% diffraction efficiency with a passband full-width-half-maximum (FWHM) of less than 0.0625 nm. Further characterization of quartz AOTF devices at deep-UV wavelengths is progressing. The hermetic packaging of KDP AOTF is nearing completion. The solid-state optical sources being used for excitation include nonlinear optics based high-energy tunable UV transmitters that operate around 320 nm and 308 nm wavelengths, and a tunable deep-UV laser operating over 193 nm to 210 nm. These AOTF devices have been developed as turn-key devices for primarily for space-based chemical and biological sensing applications using laser induced Fluorescence and resonance Raman techniques.

  5. Can optical diagnosis of small colon polyps be accurate? Comparing standard scope without narrow banding to high definition scope with narrow banding

    PubMed Central

    Ashktorab, Hassan; Etaati, Firoozeh; Rezaeean, Farahnaz; Nouraie, Mehdi; Paydar, Mansour; Namin, Hassan Hassanzadeh; Sanderson, Andrew; Begum, Rehana; Alkhalloufi, Kawtar; Brim, Hassan; Laiyemo, Adeyinka O

    2016-01-01

    AIM: To study the accuracy of using high definition (HD) scope with narrow band imaging (NBI) vs standard white light colonoscope without NBI (ST), to predict the histology of the colon polyps, particularly those < 1 cm. METHODS: A total of 147 African Americans patients who were referred to Howard University Hospital for screening or, diagnostic or follow up colonoscopy, during a 12-mo period in 2012 were prospectively recruited. Some patients had multiple polyps and total number of polyps was 179. Their colonoscopies were performed by 3 experienced endoscopists who determined the size and stated whether the polyps being removed were hyperplastic or adenomatous polyps using standard colonoscopes or high definition colonoscopes with NBI. The histopathologic diagnosis was reported by pathologists as part of routine care. RESULTS: Of participants in the study, 55 (37%) were male and median (interquartile range) of age was 56 (19-80). Demographic, clinical characteristics, past medical history of patients, and the data obtained by two instruments were not significantly different and two methods detected similar number of polyps. In ST scope 89% of polyps were < 1 cm vs 87% in HD scope (P = 0.7). The ST scope had a positive predictive value (PPV) and positive likelihood ratio (PLR) of 86% and 4.0 for adenoma compared to 74% and 2.6 for HD scope. There was a trend of higher sensitivity for HD scope (68%) compare to ST scope (53%) with almost the same specificity. The ST scope had a PPV and PLR of 38% and 1.8 for hyperplastic polyp (HPP) compared to 42% and 2.2 for HD scope. The sensitivity and specificity of two instruments for HPP diagnosis were similar. CONCLUSION: Our results indicated that HD scope was more sensitive in diagnosis of adenoma than ST scope. Clinical diagnosis of HPP with either scope is less accurate compared to adenoma. Colonoscopy diagnosis is not yet fully matched with pathologic diagnosis of colon polyp. However with the advancement of both

  6. Treatment of moderate and severe adult chronic atopic dermatitis with narrow-band UVB and the combination of narrow-band UVB/UVA phototherapy.

    PubMed

    Fernández-Guarino, Montserrat; Aboin-Gonzalez, Sonsoles; Barchino, Lucia; Velazquez, Diana; Arsuaga, Carmen; Lázaro, Pablo

    2016-01-01

    The phototherapy is a safe and effective technique for the treatment of adult patients with atopic dermatitis (AD). The treatment of chronic forms of the disease is most often done with narrow-band UVB (NB-UVB). There also exist effective phototherapy options against the AD. The aim of this study was to asses if the combination of NB-UVB with UVA was more effective than the treatment with only NB-UVB against adult chronic AD. We carried out a prospective and observational study. Adult patients with chronic AD with more than 50% of the total body surface area affected (TBSA) were included. The affected TBSA was calculated using the so-called "rule of nines." Patients with a clearance rate >75% of the initial affected TBSA or complete clearance rate were considered as complete response (CR). An analogue scale from 0 to 10 was used to measure the improvement grade of the pruritus. The treatments were repeated three times a week. The initial doses of NB-UVB and UVA were determined by patient's phototype. The treatments were performed using a phototherapy booth (UV7002, Walmann, Villingen-Schwenningen, Germany(®) ) with TL01 and UVA fluorescent lamps. Statistical analysis was performed with SPSS(®) (IBM, New York, NY) for Windows 21.0. A total of 26 patients with adult chronic AD were included in the study, 16 patients were treated with UVB-BE and 10 patients with the combined treatment option NB-UVB/UVA. The mean value of cumulative doses and the mean number of performed treatments were similar between both groups of patients (p > 0.05). The mean value of duration of response was significantly higher in the patients treated only with NB-UVB, 101 versus 6.8 months (p ≥ 0.05). No differences were observed for the patients that showed complete response (p = 0.42) and in the analogue scale of pruritus (p > 0.005). In our study, the patients treated with the combination of NB-UVB and UVA were similar to the patient that were only treated with NB-UVB e

  7. H-tailored surface conductivity in narrow band gap In(AsN)

    SciTech Connect

    Velichko, A. V. E-mail: anton.velychko@nottingham.ac.uk; Patanè, A. E-mail: anton.velychko@nottingham.ac.uk; Makarovsky, O.; Capizzi, M.; Polimeni, A.; Sandall, I. C.; Tan, C. H.; Giubertoni, D.; Krier, A.; Zhuang, Q.

    2015-01-12

    We show that the n-type conductivity of the narrow band gap In(AsN) alloy can be increased within a thin (∼100 nm) channel below the surface by the controlled incorporation of H-atoms. This channel has a large electron sheet density of ∼10{sup 18 }m{sup −2} and a high electron mobility (μ > 0.1 m{sup 2}V{sup −1}s{sup −1} at low and room temperature). For a fixed dose of impinging H-atoms, its width decreases with the increase in concentration of N-atoms that act as H-traps thus forming N-H donor complexes near the surface.

  8. Numerical investigation of the instability and nonlinear evolution of narrow-band directional ocean waves.

    PubMed

    Eliasson, Bengt; Shukla, P K

    2010-07-01

    The instability and nonlinear evolution of directional ocean waves is investigated numerically by means of simulations of the governing kinetic equation for narrow-band surface waves. Our simulation results reveal the onset of the modulational instability for long-crested wave trains, which agrees well with recent large-scale experiments in wave basins, where it was found that narrower directional spectra lead to self-focusing of ocean waves and an enhanced probability of extreme events. We find that the modulational instability is nonlinearly saturated by a broadening of the wave spectrum, which leads to the stabilization of the water-wave system. Applications of our results to other fields of physics, such as nonlinear optics and plasma physics, are discussed. PMID:20867450

  9. Narrow-band Electrostatic Noise generated by an electron velocity space hole

    NASA Technical Reports Server (NTRS)

    Richard, Robert L.; Ashour-Abdalla, Maha; Coroniti, Ferdinand V.

    1993-01-01

    Narrow-band Electrostatic Noise (NEN) is a common occurrence in the Earth's distant magnetotail. NEN is observed in a frequency range (100-316 Hz) that falls roughly between the electron and ion plasma frequencies. This mode may result from holes in the electron distribution function associated with slow shocks. An instability that is associated with this mode is studied using numerical simulations. The growth of the instability depends on the size and shape of the hole. The hole mode can also be driven unstable by either an anisotropy in the electron distribution function or an ion beam. In all these cases the instability saturates at a low level and only a fraction of the available free energy is released.

  10. Narrow Band Gap Lead Sulfide Hole Transport Layers for Quantum Dot Photovoltaics.

    PubMed

    Zhang, Nanlin; Neo, Darren C J; Tazawa, Yujiro; Li, Xiuting; Assender, Hazel E; Compton, Richard G; Watt, Andrew A R

    2016-08-24

    The band structure of colloidal quantum dot (CQD) bilayer heterojunction solar cells is optimized using a combination of ligand modification and QD band gap control. Solar cells with power conversion efficiencies of up to 9.33 ± 0.50% are demonstrated by aligning the absorber and hole transport layers (HTL). Key to achieving high efficiencies is optimizing the relative position of both the valence band and Fermi energy at the CQD bilayer interface. By comparing different band gap CQDs with different ligands, we find that a smaller band gap CQD HTL in combination with a more p-type-inducing CQD ligand is found to enhance hole extraction and hence device performance. We postulate that the efficiency improvements observed are largely due to the synergistic effects of narrower band gap QDs, causing an upshift of valence band position due to 1,2-ethanedithiol (EDT) ligands and a lowering of the Fermi level due to oxidation. PMID:27421066

  11. [Nursing care management in dermatological patient on phototherapy narrow band UVB].

    PubMed

    de Argila Fernández-Durán, Nuria; Blasco Maldonado, Celeste; Martín Gómez, Mónica

    2013-01-01

    Phototherapy with narrow band ultraviolet B is a treatment used in some dermatology units, and is the first choice in some dermatological diseases due to being comfortable and cheap. The aim of this paper is to describe the management and nursing care by grouping more specific diagnoses, following NANDA-NIC/NOC taxonomy, such as the methodology from application, technique, material, and personnel to space-related aspects, with the aim of avoiding the clinical variability and the possible associated risks for the patients, and for the nurses who administer the treatment. The continuity of the same nurse in the follow-up sessions stimulates the relationship between medical personnel and patients, key points for loyalty and therapeutic adherence. This paper examines a consensus procedure with the Dermatology Unit Team and accredited by the Hospital Quality Unit. PMID:23916523

  12. Polyp detection rates using magnification with narrow band imaging and white light

    PubMed Central

    Gilani, Nooman; Stipho, Sally; Panetta, James D; Petre, Sorin; Young, Michele A; Ramirez, Francisco C

    2015-01-01

    AIM: To compare the yield of adenomas between narrow band imaging and white light when using high definition/magnification. METHODS: This prospective, non-randomized comparative study was performed at the endoscopy unit of veteran affairs medical center in Phoenix, Arizona. Consecutive patients undergoing first average risk colorectal cancer screening colonoscopy were selected. Two experienced gastroenterologists performed all the procedures that were blinded to each other’s findings. Demographic details were recorded. Data are presented as mean ± SEM. Proportional data were compared using the χ2 test and means were compared using the Student’s t test. Tandem colonoscopy was performed in a sequential and segmental fashion using one of 3 strategies: white light followed by narrow band imaging [Group A: white light (WL) → narrow band imaging (NBI)]; narrow band imaging followed by white light (Group B: NBI → WL) and, white light followed by white light (Group C: WL → WL). Detection rate of missed polyps and adenomas were evaluated in all three groups. RESULTS: Three hundred patients were studied (100 in each Group). Although the total time for the colonoscopy was similar in the 3 groups (23.8 ± 0.7, 22.2 ± 0.5 and 24.1 ± 0.7 min for Groups A, B and C, respectively), it reached statistical significance between Groups B and C (P < 0.05). The cecal intubation time in Groups B and C was longer than for Group A (6.5 ± 0.4 min and 6.5 ± 0.4 min vs 4.9 ± 0.3 min; P < 0.05). The withdrawal time for Groups A and C was longer than Group B (18.9 ± 0.7 min and 17.6 ± 0.6 min vs 15.7 ± 0.4 min; P < 0.05). Overall miss rate for polyps and adenomas detected in three groups during the second look was 18% and 17%, respectively (P = NS). Detection rate for polyps and adenomas after first look with white light was similar irrespective of the light used during the second look (WL → WL: 13.7% for polyps, 12.6% for adenomas; WL → NBI: 14.2% for polyps, 11.3% for

  13. Investigation of narrow-band thermal emission from intersubband transitions in quantum wells

    SciTech Connect

    De Zoysa, M.; Asano, T.; Inoue, T.; Mochizuki, K.; Noda, S.

    2015-09-14

    We investigate thermal emission from n-doped GaAs/AlGaAs quantum wells (QWs). Emission peaks with Lorentzian shapes (linewidth 11∼19 meV) that reflect transitions between the first and second conduction subbands are observed in the mid-infrared range. It is demonstrated that the emission characteristics can be tuned by modifying the QW parameters. The peak emissivity is increased from 0.3 to 0.9 by modifying the doping density, and the peak wavelength is tuned from 6 to 10 μm by changing the well width. The obtained results are useful for the design of narrow-band thermal emitters.

  14. High-power narrow-band terahertz generation using large-aperture photoconductors

    SciTech Connect

    Park, S.G.; Weiner, A.M.; Melloch, M.R. . School of Electrical and Computer Engineering); Siders, C.W.; Siders, J.L.W.; Taylor, A.J. )

    1999-08-01

    Large-aperture biased photoconductive emitters which can generate high-power narrow-band terahertz (THz) radiation are developed. These emitters avoid saturation at high fluence excitation and achieve enhanced peak power spectral density by employing a thick layer of short-lifetime low-temperature-grown GaAs (LT-GaAs) photoconductor and multiple-pulse excitation. THz waveforms are calculated from the saturation theory of large-aperture photoconductors, and a comparison is made between theory and measurement. A direct comparison of the multiple-pulse saturation properties of THz emission from semi-insulating GaAs and LT-GaAs emitters reveals a strong dependence on the carrier lifetime. In particular, the data demonstrate that saturation is avoided only when the interpulse spacing is longer than the carrier lifetime.

  15. Some observations about the components of transonic fan noise from narrow-band spectral analysis

    NASA Technical Reports Server (NTRS)

    Saule, A. V.

    1974-01-01

    Qualitative and quantitative spectral analyses are presented that give the broadband-noise, discrete-tone, and multiple-tone properties of the noise generated by a full-scale high-bypass single-stage axial-flow transonic fan (fan B, NASA Quiet Engine Program). The noise components were obtained from narrow-band spectra in conjunction with 1/3-octave-band spectra. Variations in the pressure levels of the noise components with fan speed, forward-quadrant azimuth angle, and frequency are presented and compared. The study shows that much of the apparent broadband noise on 1/3-octave-band plots consists of a complex system of shaft-order tones. The analyses also indicate the difficulties in determining or defining noise components, especially the broadband level under the discrete tones. The sources which may be associated with the noise components are discussed.

  16. The method of narrow-band audio classification based on universal noise background model

    NASA Astrophysics Data System (ADS)

    Rui, Rui; Bao, Chang-chun

    2013-03-01

    Audio classification is the basis of content-based audio analysis and retrieval. The conventional classification methods mainly depend on feature extraction of audio clip, which certainly increase the time requirement for classification. An approach for classifying the narrow-band audio stream based on feature extraction of audio frame-level is presented in this paper. The audio signals are divided into speech, instrumental music, song with accompaniment and noise using the Gaussian mixture model (GMM). In order to satisfy the demand of actual environment changing, a universal noise background model (UNBM) for white noise, street noise, factory noise and car interior noise is built. In addition, three feature schemes are considered to optimize feature selection. The experimental results show that the proposed algorithm achieves a high accuracy for audio classification, especially under each noise background we used and keep the classification time less than one second.

  17. A search for narrow band signals with SERENDIP II: a progress report

    NASA Technical Reports Server (NTRS)

    Werthimer, D.; Brady, R.; Berezin, A.; Bowyer, S.

    1988-01-01

    Commensal programs for the Search for Extraterrestrial Intelligence (SETI), carried out concurrently with conventional radio astronomical observing programs, can be an attractive and cost-effective means of exploring the large multidimensional search space intrinsic to this effort. Our automated commensal system, SERENDIP II, is a high resolution 131,072 channel spectrometer. It searches for 0.49 Hz signals in sequential 64,700 Hz bands of the IF signal from a radio telescope being used for an astronomical observation. Upon detection of a narrow band signal with power above a preset threshold, the frequency, power, time, and telescope direction are recorded for later study. The system has been tested at the Hat Creek Radio Astronomy Observatory 85 ft telescope and the NASA-JPL Deep Space Station (DSS 14) 64 m telescope. It is currently collecting data at the National Radio Astronomy Observatory 300 ft telescope.

  18. The Safety and Efficacy of Narrow Band Ultraviolet B Treatment in Dermatology: A Review.

    PubMed

    Sokolova, Anna; Lee, Andrew; D Smith, Saxon

    2015-12-01

    Narrow-band ultraviolet B (NBUVB) phototherapy is an important treatment modality in dermatology. The most common dermatological indications for NBUVB include psoriasis, atopic dermatitis and vitiligo; however, it has been found to be an effective and well-tolerated treatment option in various other dermatoses. The efficacy of NBUVB phototherapy compares favorably with other available photo(chemo)therapy options and its efficacy is further augmented by a number of topical and systemic adjuncts. The long-term safety of NBUVB phototherapy remains to be fully elucidated; however, available data now suggest that it is safe and well-tolerated. The objective of this review was to summarize the current understanding of the safety and efficacy of NBUVB phototherapy in dermatology. PMID:26369540

  19. A search for narrow band signals with SERENDIP II: a progress report.

    PubMed

    Werthimer, D; Brady, R; Berezin, A; Bowyer, S

    1988-01-01

    Commensal programs for the Search for Extraterrestrial Intelligence (SETI), carried out concurrently with conventional radio astronomical observing programs, can be an attractive and cost-effective means of exploring the large multidimensional search space intrinsic to this effort. Our automated commensal system, SERENDIP II, is a high resolution 131,072 channel spectrometer. It searches for 0.49 Hz signals in sequential 64,700 Hz bands of the IF signal from a radio telescope being used for an astronomical observation. Upon detection of a narrow band signal with power above a preset threshold, the frequency, power, time, and telescope direction are recorded for later study. The system has been tested at the Hat Creek Radio Astronomy Observatory 85 ft telescope and the NASA-JPL Deep Space Station (DSS 14) 64 m telescope. It is currently collecting data at the National Radio Astronomy Observatory 300 ft telescope. PMID:11538322

  20. Electro-optic tuning and sidelobe control in acousto-optic tunable filters

    NASA Astrophysics Data System (ADS)

    Aronson, L. B.

    1995-01-01

    Both the center wavelength and the sidelobe structure of an integrated acousto-optic tunable filter (AOTF) are determined by the effective waveguide birefringence along the length of the device. By altering the birefringence by means of the electro-optic effect, one can control these device characteristics in potentially useful ways. Electro-optic tuning of the center frequency of an AOTF is demonstrated, and it is shown that this tuning mode, while limited to smaller ranges than acoustic frequency tuning, is many orders of magnitude faster. By use of multisection electrodes, dynamic control over the shape of the filter function is demonstrated. Finally, a number of practical uses of this technique are discussed.

  1. Tunable passively harmonic mode-locked Yb-doped fiber laser with Lyot-Sagnac filter.

    PubMed

    Li, Ming; Zou, Xin; Wu, Jian; Shi, Jindan; Qiu, Jifang; Hong, Xiaobin

    2015-10-10

    A novel passively harmonic mode-locked dissipative soliton Yb-doped fiber laser with all normal dispersion is proposed and experimentally demonstrated based on a semiconductor saturable absorption mirror and tunable Lyot-Sagnac filter. By only tuning the bandwidth of the filter at fixed pump power, the repetition rate of 9.87 to 167.8 MHz (corresponding to 17th-order harmonic) is obtained. This is the highest repetition rate and harmonic order for a passively harmonic mode-locked dissipative soliton Yb-doped fiber laser with all-normal dispersion to the best of our knowledge. The signal-to-noise ratio and super-mode suppression ratio for all harmonic orders are higher than 65 and 35 dB, respectively, which shows the high stability of the fiber laser. PMID:26479821

  2. Compact continuously tunable microwave photonic filters based on cascaded silicon microring resonators

    NASA Astrophysics Data System (ADS)

    Liu, Li; He, Mengying; Dong, Jianji

    2016-03-01

    We propose and experimentally demonstrate a photonic approach to achieving tunable bandpass microwave photonic filters (MPFs) based on cascaded microring resonators (CMRRs). The optical spectrum of the silicon CMRRs could offer two bandpass response to separately filter the optical carrier and one of the sidebands generated by the phase modulation. Thus we could achieve a bandpass MPF. Moreover, as the central frequencies and bandwidths of the two bandpass response can be tuned by adjusting the laser wavelength and voltages applied on one MRR, the central operating frequency or 3-dB bandwidth of the MPF can be continuously tuned in wide ranges respectively. A proof-of-concept experiment illustrates a central frequency tuning range from 19 GHz to 40 GHz, and a wide bandwidth tuning range from 5.5 GHz to 17.5 GHz.

  3. Tunable and reconfigurable single passband filter using stimulated Brillouin scattering and intensity modulation

    NASA Astrophysics Data System (ADS)

    Hu, Shuling; Xiao, Zeyu; Wang, Huanhuan

    2015-07-01

    A tunable and reconfigurable single passband microwave photonic filter based on stimulated Brillouin scattering (SBS) and intensity modulation is presented and theoretically analyzed. Three Brillouin pumps with equal intensity are generated by selecting appropriate bias voltages and modulation indices. Then a reconfigurable passband can be achieved by superposition of the three pumps. Simulation results demonstrate that the proposed filter has a 22-GHz continuous tuning range with a high out-of-band rejection ratio above 40 dB. The -3-dB bandwidth can be tuned from 12 to 95 MHz, and the flatness is less than 1.5 dB. This technique uses a low-frequency (0 to 35 MHz) modulation signal to realize passband reshaping, and has potential applications in communication and radar systems.

  4. Frequency tunable terahertz filter based on dual layered split-ring resonator array

    NASA Astrophysics Data System (ADS)

    Jung, Hyunseung; Lee, Hojin

    2014-01-01

    Terahertz frequency tunable filter based on the dual layered split-ring resonator (SRR) array was fabricated on flexible polyimide film using conventional photolithography techniques. The fabricated SRR array was measured by terahertz time-domain spectroscopy (THz-TDS) and compared with the simulation data. We found that the center frequency could be controlled from 1.04 to 1.65 THz by the dipole coupling effect between upper and lower SRR layers. The bandwidth of the fabricated filter is also confirmed to be tuned validly ranging from 1.04 to 1.72 THz. By using the extracted field distribution, we verified that the localized field enhancement could be manipulated by changing the coupling distance between adjacent layers.

  5. Tunable channel drop filters consisting of a tilted Bragg grating and a mode sorting polymer waveguide.

    PubMed

    Park, Tae-Hyun; Shin, Jin-Soo; Huang, Guanghao; Chu, Woo-Sung; Oh, Min-Cheol

    2016-03-21

    Optical wavelength filters with large tuning range and narrow bandwidth are crucial for enhancing the capability of WDM communication systems. A polymeric tunable filter for C-band, comprising a tilted Bragg grating and a mode sorting waveguide junction is proposed in this work. For dropping a certain wavelength signal, the tilted Bragg grating reflects an odd mode into an even mode and then the reflected even mode propagates towards an output port of the asymmetric Y-junction due to the mode sorting. Consequently, the output port is separated from the input port, which is not possible in an ordinary Bragg reflector. The tilted Bragg reflector with an odd-even mode coupling efficiency of 61% exhibited a maximum reflectivity of 95% for a grating of 6 mm. A linear wavelength tuning of over 10 nm was achieved for an applied thermal power of 312 mW. PMID:27136768

  6. Tunable terahertz multichannel filter based on one-dimensional superconductor-dielectric photonic crystals

    SciTech Connect

    Liu, Yang; Yi, Lin

    2014-12-14

    By means of the transfer matrix method, the transmission properties of one-dimensional photonic crystals (PCs) consisting of superconductor and dielectric have been systematically investigated within the terahertz frequency range (0.1–10 THz). It is shown that comb-like resonant peaks in transmission band can be formed without adding any defect layer in superconductor-dielectric PCs, which means that such a one-dimensional periodic structure can serve as a tunable terahertz multichannel filter by using the PCs passband. Furthermore, the influences coming from the period of the structure, the thickness of the components, the permittivity of the dielectric layers, temperature, and the normal conducting electrons on the filtering properties are also numerically investigated.

  7. Wavelength-tunable actively mode-locked erbium-doped fiber ring laser using a distributed feedback semiconductor laser as mode locker and tunable filter

    NASA Astrophysics Data System (ADS)

    Li, Shenping; Chan, K. T.

    1999-07-01

    A wavelength-tunable actively mode-locked erbium fiber ring laser was demonstrated using a distributed feedback semiconductor laser as an intensity mode locker and a tunable optical filter. Very stable optical pulse trains at gigabit repetition rates were generated using harmonica mode locking. The supermode noise was suppressed to 60 dB below the signal level and the root-mean-square timing jitter (0.45 kHz-1 MHz) was found to be about 1% of the pulse duration. A continuous wavelength tuning range of 1.8 nm was achieved by changing the semiconductor laser temperature from 11.4 to 30 °C.

  8. Narrow-band surveys for very high redshift Lyman-α emitters

    NASA Astrophysics Data System (ADS)

    Nilsson, K. K.; Orsi, A.; Lacey, C. G.; Baugh, C. M.; Thommes, E.

    2007-11-01

    Context: Many current and future surveys aim to detect the highest redshift (z ⪆ 7) sources through their Lyman-α (Lyα) emission, using the narrow-band imaging method. However, to date the surveys have only yielded non-detections and upper limits as no survey has reached the necessary combination of depth and area to detect these very young star forming galaxies. Aims: We aim to calculate model luminosity functions and mock surveys of Lyα emitters at z ⪆ 7 based on a variety of approaches calibrated and tested on observational data at lower redshifts. Methods: We calculate model luminosity functions at different redshifts based on three different approaches: a semi-analytical model based on CDM, a simple phenomenological model, and an extrapolation of observed Schechter functions at lower redshifts. The results of the first two models are compared with observations made at redshifts z ˜ 5.7 and z ˜ 6.5, and they are then extrapolated to higher redshift. Results: We present model luminosity functions for redshifts between z = 7{-}12.5 and give specific number predictions for future planned or possible narrow-band surveys for Lyα emitters. We also investigate what constraints future observations will be able to place on the Lyα luminosity function at very high redshift. Conclusions: It should be possible to observe z = 7{-}10 Lyα emitters with present or near-future instruments if enough observing time is allocated. In particular, large area surveys such as ELVIS (Emission Line galaxies with VISTA Survey) will be useful in collecting a large sample. However, to get a large enough sample to constrain well the z ≥ 10 Lyα luminosity function, instruments further in the future, such as an ELT, will be necessary.

  9. Tunable complex-valued multi-tap microwave photonic filter based on single silicon-on-insulator microring resonator.

    PubMed

    Lloret, Juan; Sancho, Juan; Pu, Minhao; Gasulla, Ivana; Yvind, Kresten; Sales, Salvador; Capmany, José

    2011-06-20

    A complex-valued multi-tap tunable microwave photonic filter based on single silicon-on-insulator microring resonator is presented. The degree of tunability of the approach involving two, three and four taps is theoretical and experimentally characterized, respectively. The constraints of exploiting the optical phase transfer function of a microring resonator aiming at implementing complex-valued multi-tap filtering schemes are also reported. The trade-off between the degree of tunability without changing the free spectral range and the number of taps is studied in-depth. Different window based scenarios are evaluated for improving the filter performance in terms of the side-lobe level. PMID:21716478

  10. Photonic chip based tunable and reconfigurable narrowband microwave photonic filter using stimulated Brillouin scattering.

    PubMed

    Byrnes, Adam; Pant, Ravi; Li, Enbang; Choi, Duk-Yong; Poulton, Christopher G; Fan, Shanhui; Madden, Steve; Luther-Davies, Barry; Eggleton, Benjamin J

    2012-08-13

    We report the first demonstration of a photonic chip based dynamically reconfigurable, widely tunable, narrow pass-band, high Q microwave photonic filter (MPF). We exploit stimulated Brillouin scattering (SBS) in a 6.5 cm long chalcogenide (As2S3) photonic chip to demonstrate a MPF that exhibited a high quality factor of ~520 and narrow bandwidth and was dynamically reconfigurable and widely tunable. It maintained a stable 3 dB bandwidth of 23 ± 2MHz and amplitude of 20 ± 2 dB over a large frequency tuning range of 2-12 GHz. By tailoring the pump spectrum, we reconfigured the 3 dB bandwidth of the MPF from ~20 MHz to ~40 MHz and tuned the shape factor from 3.5 to 2 resulting in a nearly flat-topped filter profile. This demonstration represents a significant advance in integrated microwave photonics with potential applications in on-chip microwave signal processing for RADAR and analogue communications. PMID:23038523

  11. DKIST visible tunable filter control software: connecting the DKIST framework to OPC UA

    NASA Astrophysics Data System (ADS)

    Bell, Alexander; Halbgewachs, Clemens; Kentischer, Thomas J.; Schmidt, Wolfgang; von der Lühe, Oskar; Sigwarth, Michael; Fischer, Andreas

    2014-07-01

    The Visible Tunable Filter (VTF) is a narrowband tunable filter system for imaging spectroscopy and spectropolarimetry based on large-format Fabry Perot interferometers that is currently built by the Kiepenheuer Institut fuer Sonnenphysik for the Daniel K. Inouye Solar Telescope (DKIST). The control software must handle around 30 motorised drives, 3 etalons, a polarizing modulator, a helium neon laser for system calibration, temperature controllers and a multitude of sensors. The VTF is foreseen as one of the DKISTs first-light instruments and should become operational in 2019. In the design of the control software we strongly separate between the high-level part interfacing to the DKIST common services framework (CSF) and the low-level control system software which guarantees real-time performance and synchronization to precision time protocol (PTP) based observatory time. For the latter we chose a programmable logic controller (PLC) from Beckhoff Automation GmbH which supports a wide set of input and output devices as well as distributed clocks for synchronizing signals down to the sub-microsecond level. In this paper we present the design of the required control system software as well as our work on extending the DKIST CSF to use the OPC Unified Architecture (OPC UA) standard which provides a cross-platform communication standard for process control and automation as an interface between the high-level software and the real-time control system.

  12. Comparative performance studies between tunable filter and push-broom chemical imaging systems

    NASA Astrophysics Data System (ADS)

    Malinen, Jouko; Saari, Heikki; Kemeny, Gabor; Shi, Zhenqi; Anderson, Carl

    2010-04-01

    This paper reports instrument characterization measurements, which were recently arranged to provide comparative information on different hyperspectral chemical imaging systems. Three different instruments were studied covering both tunable filter and push-broom techniques: The first instrument MatrixNIRTM is based on a LCTF tunable filter and InGaAs camera and covers wavelengths from 1000 to 1700 nm. The second one SisuCHEMATM is based on push-broom technology and MCT camera operating from 1000 to 2500 nm. The third system is an instrument prototype from VTT Technical Research Centre of Finland exploiting high speed Fabry-Perot interferometer and MCT camera, currently calibrated from 1260 to 2500 nm. The characterization procedure was designed to study instrumental noise, signal-to-noise ratio, linearity and spectral as well as spatial resolution. Finally, a pharmaceutical tablet sample was measured with each instrument to demonstrate speed of measurement in a typical application. In spite of differences in wavelength ranges and camera technologies used, the results provide interesting information on relative instrumental advantages and disadvantages, which may be useful for selecting appropriate instrumentation for defined applications. Further, an additional aim of this study is to compare the high speed Fabry-Perot imaging technology under development against the established chemical imaging techniques available on the market today.

  13. Configurable-bandwidth imaging spectrometer based on an acousto-optic tunable filter

    NASA Astrophysics Data System (ADS)

    Vila-Francés, Joan; Calpe-Maravilla, Javier; Muñoz-Mari, Jordi; Gómez-Chova, Luis; Amorós-López, Julia; Ribes-Gómez, Emilio; Durán-Bosch, Vicente

    2006-07-01

    This article presents a new imaging spectrometer called autonomous tunable filtering system. The instrument acquires sequential images at different spectral wavelengths in the visible and near infrared range of the electromagnetic spectrum. The spectral selection is performed by an acousto-optic tunable filter (AOTF), which is driven by a custom radio-frequency (rf) generator based on a direct digital synthesizer (DDS). The DDS allows a high flexibility in terms of acquisition speed and bandwidth selection. The rf power is dynamically controlled to drive the AOTF with the optimum value for each wavelength. The images are formed through a carefully designed optical layout and acquired with a high performance digital camera. The application software controls the instrument and acquires the raw spectral images from the camera. This software optionally corrects the image for the AOTF nonidealities, such as diffraction efficiency variations, spatial nonuniformity, and chromatic aberration, and generates a single multiband image file. Moreover, the software can calculate the reflectance or transmittance of the acquired images. The instrument has been calibrated to give precise and repetitive measurements and has been validated against a high performance point spectrometer. As a case example, the instrument has been successfully used for the mapping of chlorophyll content of plant leaves from their multispectral reflectance images.

  14. Tunable drop filters based on photonic crystal self-collimation ring resonators

    NASA Astrophysics Data System (ADS)

    Li, Junjun; Chen, Xiyao; Xu, Xiaofu; Jiang, Junzhen; Qiang, Zexuan; Lin, Guimin; Zhang, Hao

    2010-10-01

    A tunable drop filter (TDF) based on two-dimensional photonic crystal (PC) self-collimation ring resonator (SCRR) is proposed. The PC consisting of square-lattice air cylinders in silicon has square-shaped equal frequency contours (EFCs) in the wavevector space at the frequencies between 0.172-0.188c/a for TE modes. The SCRR includes two mirrors and two splitters. The air holes inside the SCRR are infiltrated with a kind of liquid crystal whose ordinary and extraordinary refractive indices are 1.522 and 1.706, respectively. The effective refractive index neff of liquid crystal depends on the applied electric field. Simulated with the FDTD method, the transmission spectra at the drop port of SCRR are in the shape of sinusoidal curves with uniform peak spacing between 0.172-0.188c/a. Transmission peaks will shift to the lower frequencies when neff is increased. When neff changes from 1.522 to 1.706, the peaks will experience red-shift over 0.003c/a. So this SCRR can work as a tunable drop filter. For the operating wavelength around 1550nm, its dimensions are only tens of microns.

  15. Widely tunable single bandpass microwave photonic filter based on Brillouin-assisted optical carrier recovery.

    PubMed

    Wang, Wen Ting; Liu, Jian Guo; Sun, Wen Hui; Wang, Wei Yu; Wang, Sun Long; Zhu, Ning Hua

    2014-12-01

    A widely tunable single bandpass microwave photonic filter (MPF) based on Brillouin-assisted optical carrier recovery in a highly nonlinear fiber (HNLF) with only one optical filter is proposed and experimentally demonstrated. The fundamental principle lies in the fact that the suppressed optical carrier of the phase modulated optical signal could be recovered by the stimulated Brillouin scattering (SBS) amplification effect. When phase modulated optical signals go through an optical filter with a bandpass response, the optical carrier and the upper sidebands suffer from the suppression of the optical filter because they fall in the stopband of that. In our system, the optical carrier could be recovered by the SBS operation around 38 dB. The MPF is achieved by one-to-one mapping from the optical domain to the electrical domain only when one of phase modulated sidebands lies in the bandpass of the optical filter. It shows an excellent selectivity with a 3-dB bandwidth of 170 MHz over a tuning frequency range of 9.5-32.5 GHz. The out-of-band suppression of the MPF is more than 20 dB. Moreover, the MPF shows an excellent shape factor with 10-dB bandwidth of only 520 MHz. The frequency response of the MPF could be widely tuned by changing the frequency difference between the frequency of the optical carrier and the center frequency of the bandpass of the optical filter. A proof-of-concept experiment is carried out to verify the proposed approach. PMID:25606864

  16. Tunable integrated optical filter made of a glass ion-exchanged waveguide and an electro-optic composite holographic grating.

    PubMed

    d'Alessandro, Antonio; Donisi, Domenico; De Sio, Luciano; Beccherelli, Romeo; Asquini, Rita; Caputo, Roberto; Umeton, Cesare

    2008-06-23

    We report the fabrication and the optical characterization of a hybrid tunable integrated optical filter. It consists of a diffused ion-exchanged channel waveguide on a borosilicate glass substrate with a cover of the same glass to form a gap filled with a holographic grating. The grating morphology, called POLICRYPS (POlymer LIquid CRYstal Polymer Slices), is made of alternating stripes of polymer and liquid crystal acting as overlayer for the underneath waveguide. The filter structure includes aluminum coplanar electrodes to electrically control the grating properties, allowing the tunability of the filter. The electric driving power required to tune the filter obtained was in the range of submilliwatts due to the efficient liquid crystal electro-optic effect. PMID:18575489

  17. All-fiber widely tunable mode-locked thulium-doped laser using a curvature multimode interference filter

    NASA Astrophysics Data System (ADS)

    Li, N.; Liu, M. Y.; Gao, X. J.; Zhang, L.; Jia, Z. X.; Feng, Y.; Ohishi, Y.; Qin, G. S.; Qin, W. P.

    2016-07-01

    We demonstrated a widely tunable mode-locked thulium doped fiber laser (TDFL) by using a homemade multimode interference filter (MMIF). The MMIF had a structure of single mode fiber (SMF)—multimode fiber (MMF)—SMF and three main transmission peaks at 1901.2, 1957.2 and 2043.2 nm. By mechanically bending the MMIF, the three main transmission peaks were tuned in the range of 1860–2024 nm due to multimode interference effect. By inserting the MMIF into a passively mode-locked TDFL cavity pumped by a 1570 nm fiber laser, a tunable mode-locked TDFL with a tuning range of 1919.6–2014.9 nm was achieved by adjusting the MMIF. To the best of our knowledge, such a tunable range is the largest among all-fiber tunable mode-locked TDFLs.

  18. Tunable integrated optical filters based on sapphire microspheres and liquid crystals

    NASA Astrophysics Data System (ADS)

    Gilardi, Giovanni; Yilmaz, Hasan; Sharif Murib, Mohammed; Asquini, Rita; d'Alessandro, Antonio; Serpengüzel, Ali; Beccherelli, Romeo

    2010-05-01

    We present an integrated optical narrowband electrically tunable filter based on the whispering gallery modes of sapphire microspheres and double ion-exchanged channel BK7 glass waveguides. Tuning is provided by a liquid crystal infiltrated between the spheres and the glass substrate. By suitably choosing the radii of the spheres and of the circular apertures, upon which the spheres are positioned, arrays of different filters can be realized on the same substrate with a low cost industrial process. We evaluate the performance in terms of quality factor, mode spacing, and tuning range by comparing the numerical results obtained by the numerical finite element modeling approach and with the analytical approach of the Generalized Lorenz-Mie Theory for various design parameters. By reorienting the LC in an external electrical field, we demonstrate the tuning of the spectral response of the sapphire microsphere based filter. We find that the value of the mode spacing remains nearly unchanged for the different values of the applied electric field. An increase of the applied electric field strength, changes the refractive index of the liquid crystal, so that for a fixed geometry the mode spacing remains unchanged.

  19. A wavelength-tunable fiber laser based on a twin-core fiber comb filter

    NASA Astrophysics Data System (ADS)

    Zou, Hui; Lou, Shuqin; Yin, Guolu

    2013-02-01

    A wavelength-tunable fiber laser based on a twin-core fiber (TCF) comb filter is proposed and demonstrated. The TCF comb filter is fabricated by splicing a 0.85 m long TCF between two standard single mode fibers (SMFs) and with exhibits a good linear strain characteristic with a sensitivity of 1.23 pm/μɛ. The wavelength of the laser can be linearly tuned from 1558.04 nm to 1553.62 nm by applying an axial strain to the TCF comb filter. The optical signal-to-noise ratio (OSNR) of the fiber laser reaches 45 dB. The 3 dB bandwidth is 0.02 nm. The fluctuation of the laser peak in the output power and the wavelength is less than 0.5 dB and within 0.05 nm, respectively. The fiber laser has the advantages of having a simple structure and stable operation under room temperature.

  20. Microwave photonic filter with multiple independently tunable passbands based on a broadband optical source.

    PubMed

    Huang, Long; Chen, Dalei; Zhang, Fangzheng; Xiang, Peng; Zhang, Tingting; Wang, Peng; Lu, Linlin; Pu, Tao; Chen, Xiangfei

    2015-10-01

    In this paper, a novel microwave photonic filter (MPF) with multiple independently tunable passbands is proposed. A broadband optical source (BOS) is employed and split by a 1:N coupler into several branches. One branch is directed to a phase modulator which is modulated by a radio frequency signal and the other branches are delayed by optical delay lines (ODLs), respectively. All of these branches are combined by another 1:N coupler and sent to a dispersion compensation fiber which is used to introduce group delay dispersion to the optical signal. At a photodetector, each time-delayed broadband lightwave beating with the sidebands produced by the phase modulator forms a passband of the MPF. By tuning the delay of each broadband lightwave, the center frequency of the passband can be independently tuned. An MPF with two independently tunable passbands is experimentally demonstrated. The two passbands can be tuned from DC to 30 GHz with a 3-dB bandwidth of about 250 MHz. The stability and dynamic range of the MPF are also evaluated. By employing more branches delayed by ODLs, more passbands can be generated. PMID:26480071

  1. Switchable and tunable microwave frequency multiplication based on a dual-passband microwave photonic filter.

    PubMed

    Chen, Hao; Xu, Zuowei; Fu, Hongyan; Zhang, Shiwei; Wu, Congxian; Wu, Hao; Xu, Huiying; Cai, Zhiping

    2015-04-20

    In this paper, a novel approach to implement switchable and tunable microwave frequency multiplication has been proposed and experimentally demonstrated. High order harmonics of microwave signal with external modulation technique can be selected by using a novel switchable dual-passband microwave photonic filter (MPF) based on a modified fiber Mach-Zehnder interferometer (FMZI) and a dispersive medium. By adjusting the polarization controllers in the modified FMZI, the passbands of the MPF can switch between lower frequency, higher frequency or dual-passband states, and by changing the length of the variable optical delay line (VODL) in the modified FMZI, the central frequencies of these passbands can also be tuned. Therefore, tunable and switchable microwave signal frequency multiplication can be achieved. The experimental results show that by modulating a driving signal with frequency of 2.5 GHz, a signal with frequency of 7.5 GHz, which is three times of the driving frequency, the other one with the frequency of 15 GHz, which is six times of the driving frequency can be generated and freely switchable between two frequencies and dual frequency states by simply adjusting the polarization controllers in the modified FMZI. PMID:25969024

  2. Measurement and Analysis of Narrow-Band Surface Acoustic Waves in Ceramic Environmental Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Steen, T. L.; Basu, S. N.; Sarin, V. K.; Murray, T. W.

    2008-02-01

    A laser-based ultrasonic system is used to measure the mechanical properties and thickness of mullite environmental barrier coatings deposited on SiC substrates. Narrow-band surface acoustic waves (SAWs) are generated with an amplitude modulated laser source, and a photorefractive crystal based interferometer coupled to a lock-in amplifier is used to detect the resulting surface displacement. The complex displacement field is mapped over a source-to-receiver distance of approximately 500 μm in order to extract the wavelength of the SAW at a given excitation frequency, from which the phase velocity is determined. Dispersion curves measured over a frequency range of 100-180 MHz are used to extract mean values for the elastic modulus and thickness of the coating over the measurement region. These values are compared to the mean elastic modulus and thickness of the coating measured using nanoindentation and optical microscopy, respectively. It is shown that porosity in the substrate can have a significant impact on the experimental results, particularly over short measurement distances. Experiments on SiC with 1-4% porosity show a linear increase of the mean SAW velocity with decreasing porosity. Additionally, measurements made on a sample with a given bulk porosity indicate that the SAW velocity varies locally, leading to additional error in the measurement of coating properties. This error can be reduced through spatially averaging the velocity measurements.

  3. Growth of semiconducting single-wall carbon nanotubes with a narrow band-gap distribution

    PubMed Central

    Zhang, Feng; Hou, Peng-Xiang; Liu, Chang; Wang, Bing-Wei; Jiang, Hua; Chen, Mao-Lin; Sun, Dong-Ming; Li, Jin-Cheng; Cong, Hong-Tao; Kauppinen, Esko I.; Cheng, Hui-Ming

    2016-01-01

    The growth of high-quality semiconducting single-wall carbon nanotubes with a narrow band-gap distribution is crucial for the fabrication of high-performance electronic devices. However, the single-wall carbon nanotubes grown from traditional metal catalysts usually have diversified structures and properties. Here we design and prepare an acorn-like, partially carbon-coated cobalt nanoparticle catalyst with a uniform size and structure by the thermal reduction of a [Co(CN)6]3− precursor adsorbed on a self-assembled block copolymer nanodomain. The inner cobalt nanoparticle functions as active catalytic phase for carbon nanotube growth, whereas the outer carbon layer prevents the aggregation of cobalt nanoparticles and ensures a perpendicular growth mode. The grown single-wall carbon nanotubes have a very narrow diameter distribution centred at 1.7 nm and a high semiconducting content of >95%. These semiconducting single-wall carbon nanotubes have a very small band-gap difference of ∼0.08 eV and show excellent thin-film transistor performance. PMID:27025784

  4. Hearing thresholds of a harbor porpoise (Phocoena phocoena) for narrow-band sweeps.

    PubMed

    Kastelein, Ronald A; Schop, Jessica; Hoek, Lean; Covi, Jennifer

    2015-10-01

    The hearing sensitivity of a 2-yr-old male harbor porpoise was measured using a standard psycho-acoustic technique under low ambient noise conditions. Auditory sensitivity was measured for narrow-band 1 s sweeps (center frequencies: 0.125-150 kHz). The audiogram was U-shaped; range of best hearing (within 10 dB of maximum sensitivity) was from 13 to ∼140 kHz. Maximum sensitivity (threshold: ∼39 dB re 1 μPa) occurred at 125 kHz at the peak frequency of echolocation pulses produced by harbor porpoises. Reduced sensitivity occurred at 32 and 63 kHz. Sensitivity fell by ∼10 dB per octave below 16 kHz and declined sharply above 125 kHz. Apart from this individual's ca. 10 dB higher sensitivity at 0.250 kHz, ca. 10 dB lower sensitivity at 32 kHz, and ca. 59 dB lower sensitivity at 150 kHz, his audiogram is similar to that of two harbor porpoises tested previously with a similar psycho-acoustic technique. PMID:26520333

  5. Adaptive digital calibration techniques for narrow band low-IF receivers with on-chip PLL

    NASA Astrophysics Data System (ADS)

    Juan, Li; Huajiang, Zhang; Feng, Zhao; Zhiliang, Hong

    2009-06-01

    Digital calibration and control techniques for narrow band integrated low-IF receivers with on-chip frequency synthesizer are presented. The calibration and control system, which is adopted to ensure an achievable signal-to-noise ratio and bit error rate, consists of a digitally controlled, high resolution dB-linear automatic gain control (AGC), an inphase (I) and quadrature (Q) gain and phase mismatch calibration, and an automatic frequency calibration (AFC) of a wideband voltage-controlled oscillator in a PLL based frequency synthesizer. The calibration system has a low design complexity with little power and small die area. Simulation results show that the calibration system can enlarge the dynamic range to 72 dB and minimize the phase and amplitude imbalance between I and Q to 0.08° and 0.024 dB, respectively, which means the image rejection ratio is better than 60 dB. In addition, the calibration time of the AFC is 1.12 μs only with a reference clock of 100 MHz.

  6. Three-step H- charge exchange injection with a narrow-band laser

    NASA Astrophysics Data System (ADS)

    Danilov, V.; Aleksandrov, A.; Assadi, S.; Henderson, S.; Holtkamp, N.; Shea, T.; Shishlo, A.; Braiman, Y.; Liu, Y.; Barhen, J.; Zacharia, T.

    2003-05-01

    This paper presents a scheme for three-step laser-based stripping of an H- beam for charge exchange injection into a high-intensity proton ring. First, H- atoms are converted to H0 by Lorentz stripping in a strong magnetic field, then neutral hydrogen atoms are excited from the ground state to upper levels by a laser, and the remaining electron, now more weakly bound, is stripped in a strong magnetic field. The energy spread of the beam particles gives rise to a Doppler broadened absorption linewidth, which makes for an inefficient population of the upper state by a narrow-band laser. We propose to overcome this limitation with a “frequency sweeping” arrangement, which populates the upper state with almost 100% efficiency. We present estimates of peak laser power and describe a method to reduce the power by tailoring the dispersion function at the laser-particle beam interaction point. We present a scheme for reducing the average power requirements by using an optical ring resonator. Finally, we discuss an experimental setup to demonstrate this approach in a proof-of-principle experiment.

  7. Narrow-band EUV Multilayer Coating for the MOSES Sounding Rocket

    NASA Technical Reports Server (NTRS)

    Owens, Scott M.; Gum, Jeffery S.; Tarrio, Charles; Dvorak, Joseph; Kjornrattanawanich, Benjawan; Keski-Kuha, Ritva; Thomas, Roger J.; Kankelborg, Charles C.

    2005-01-01

    The Multi-order Solar EUV Spectrograph (MOSES) is a slitless spectrograph designed to study solar He II emission at 303.8 Angstroms, to be launched on a sounding rocket payload. One difference between MOSES and other slitless spectrographs is that the images are recorded simultaneously at three spectral orders, m = -1,0, +l. Another is the addition of a narrow-band multilayer coating on both the grating and the fold flat, which will reject out-of-band lines that normally contaminate the image of a slitless instrument. The primary metrics f a the mating were high peak reflectivity and suppression of Fe XV and XVI emission lines at 284 Angstroms and 335 Angstroms, respectively. We chose B4C/Mg2Si for our material combination since it provides better values for all three metrics together than the other leading candidates Si/Ir, Si/B4C or Si/SiC. Measurements of witness flats at NIST indicate the peak reflectivity at 303.6 is 38.5% for a 15 bilayer stack, while the suppression at 284 Angstroms, is 4.5x and at 335 Angstroms is 18.3x for each of two reflections in the instrument. We present the results of coating the MOSES flight gratings and fold flat, including the spectral response of the fold flat and grating as measured at NIST's SURF III and Brookhaven's X24C beamline.

  8. Development of narrow-band fluorescence index for the detection of aflatoxin contaminated corn

    NASA Astrophysics Data System (ADS)

    Yao, Haibo; Hruska, Zuzana; Kincaid, Russell; Ononye, Ambrose; Brown, Robert L.; Bhatnagar, Deepak; Cleveland, Thomas E.

    2011-06-01

    Aflatoxin is produced by the fungus Aspergillus flavus when the fungus invades developing corn kernels. Because of its potent toxicity, the levels of aflatoxin are regulated by the Food and Drug Administration (FDA) in the US, allowing 20 ppb (parts per billion) limits in food, and feed intended for interstate commerce. Currently, aflatoxin detection and quantification methods are based on analytical tests. These tests require the destruction of samples, can be costly and time consuming, and often rely on less than desirable sampling techniques. Thus, the ability to detect aflatoxin in a rapid, non-invasive way is crucial to the corn industry in particular. This paper described how narrow-band fluorescence indices were developed for aflatoxin contamination detection based on single corn kernel samples. The indices were based on two bands extracted from full wavelength fluorescence hyperspectral imagery. The two band results were later applied to two large sample experiments with 25 g and 1 kg of corn per sample. The detection accuracies were 85% and 95% when 100 ppb threshold was used. Since the data acquisition period is significantly lower for several image bands than for full wavelength hyperspectral data, this study would be helpful in the development of real-time detection instrumentation for the corn industry.

  9. Analysis of Discrimination Techniques for Low-Cost Narrow-Band Spectrofluorometers

    PubMed Central

    Aymerich, Ismael F.; Sánchez, Albert-Miquel; Pérez, Sergio; Piera, Jaume

    2015-01-01

    The need for covering large areas in oceanographic measurement campaigns and the general interest in reducing the observational costs open the necessity to develop new strategies towards this objective, fundamental to deal with current and future research projects. In this respect, the development of low-cost instruments becomes a key factor, but optimal signal-processing techniques must be used to balance their measurements with those obtained from accurate but expensive instruments. In this paper, a complete signal-processing chain to process the fluorescence spectra of marine organisms for taxonomic discrimination is proposed. It has been designed to deal with noisy, narrow-band and low-resolution data obtained from low-cost sensors or instruments and to optimize its computational cost, and it consists of four separated blocks that denoise, normalize, transform and classify the samples. For each block, several techniques are tested and compared to find the best combination that optimizes the classification of the samples. The signal processing has been focused on the Chlorophyll-a fluorescence peak, since it presents the highest emission levels and it can be measured with sensors presenting poor sensitivity and signal-to-noise ratios. The whole methodology has been successfully validated by means of the fluorescence spectra emitted by five different cultures. PMID:25558997

  10. Narrow-band imaging with magnifying endoscopy for the evaluation of gastrointestinal lesions

    PubMed Central

    Boeriu, Alina; Boeriu, Cristian; Drasovean, Silvia; Pascarenco, Ofelia; Mocan, Simona; Stoian, Mircea; Dobru, Daniela

    2015-01-01

    Narrow band imaging (NBI) endoscopy is an optical image enhancing technology that allows a detailed inspection of vascular and mucosal patterns, providing the ability to predict histology during real-time endoscopy. By combining NBI with magnification endoscopy (NBI-ME), the accurate assessment of lesions in the gastrointestinal tract can be achieved, as well as the early detection of neoplasia by emphasizing neovascularization. Promising results of the method in the diagnosis of premalignant and malignant lesions of gastrointestinal tract have been reported in clinical studies. The usefulness of NBI-ME as an adjunct to endoscopic therapy in clinical practice, the potential to improve diagnostic accuracy, surveillance strategies and cost-saving strategies based on this method are summarized in this review. Various classification systems of mucosal and vascular patterns used to differentiate preneoplastic and neoplastic lesions have been reviewed. We concluded that the clinical applicability of NBI-ME has increased, but standardization of endoscopic criteria and classification systems, validation in randomized multicenter trials and training programs to improve the diagnostic performance are all needed before the widespread acceptance of the method in routine practice. However, published data regarding the usefulness of NBI endoscopy are relevant in order to recommend the method as a reliable tool in diagnostic and therapy, even for less experienced endoscopists. PMID:25685267

  11. Magnifying Endoscopy with Narrow Band Imaging of Early Gastric Cancer: Correlation with Histopathology and Mucin Phenotype

    PubMed Central

    Ok, Kyung-Sun; Kim, Gwang Ha; Park, Do Youn; Lee, Hyun Jeong; Jeon, Hye Kyung; Baek, Dong Hoon; Lee, Bong Eun; Song, Geun Am

    2016-01-01

    Background/Aims Magnifying endoscopy with narrow band imaging (ME-NBI) is a useful modality for the detailed visualization of microsurface (MS) and microvascular (MV) structures in the gastrointestinal tract. This study aimed to determine whether the MS and MV patterns in ME-NBI differ according to the histologic type, invasion depth, and mucin phenotype of early gastric cancers (EGCs). Methods The MS and MV patterns of 160 lesions in 160 patients with EGC who underwent ME-NBI before endoscopic or surgical resection were prospectively collected and analyzed. EGCs were categorized as either differentiated or undifferentiated and as either mucosal or submucosal, and their mucin phenotypes were determined via immunohistochemistry of the tumor specimens. Results Differentiated tumors mainly displayed an oval and/or tubular MS pattern and a fine network or loop MV pattern, whereas undifferentiated tumors mainly displayed an absent MS pattern and a corkscrew MV pattern. The destructive MS pattern was associated with submucosal invasion, and this association was more prominent in the differentiated tumors than in the undifferentiated tumors. MUC5AC expression was increased in lesions with either a papillary or absent MS pattern and a corkscrew MV pattern, whereas MUC6 expression was increased in lesions with a papillary MS pattern and a loop MV pattern. CD10 expression was more frequent in lesions with a fine network MV pattern. Conclusions ME-NBI can be useful for predicting the histopathology and mucin phenotype of EGCs. PMID:27021504

  12. Equine endometrial vascular pattern changes during the estrous cycle examined by Narrow Band Imaging hysteroscopy.

    PubMed

    Otzen, Henning; Sieme, Harald; Oldenhof, Harriëtte; Kassens, Ana; Ertmer, Franziska; Rode, Kristina; Müller, Kristin; Klose, Kristin; Rohn, Karl; Schoon, Heinz-Adolf; Meinecke, Burkhard

    2016-03-01

    The aim of this study was to evaluate the uterine blood supply and endometrial vessel architecture, during the equine estrous cycle. Narrow Band Imaging (NBI) hysteroscopy was used for evaluating changes in the endometrial vasculature during the estrous cycle [six mares, d 0 (representing the day of ovulation), d 6 and 11 in four locations]. In addition, endometrial biopsy samples were used for immunodetection of markers for angiogenesis (Vascular Endothelial Growth Factor A, its receptor 2, as well as angiopoietin-2 and its receptor-tyrosine-kinase Tie2) during the estrous cycle (three mares, d 0, 5 and 10; one biopsy per mare). Detailed analysis of hysteroscopic images revealed an increase in the vascular density from estrus towards diestrus. In contrast, microscopic specimens prepared from biopsies revealed no evidence for changes in the endometrial vessel number during the estrous cycle. Studies on expression of angiogenesis markers indicated that cyclic changes in the endometrial vascular density observed by NBI-hysteroscopy were not due to formation of new vessels. It is concluded that vessels are involved in blood supply of a smaller area during diestrus, facilitating better distribution of nutrients during this phase. PMID:26791330

  13. Polyp Detection, Characterization, and Management Using Narrow-Band Imaging with/without Magnification

    PubMed Central

    Utsumi, Takahiro; Iwatate, Mineo; Sano, Wataru; Sunakawa, Hironori; Hattori, Santa; Hasuike, Noriaki; Sano, Yasushi

    2015-01-01

    Narrow-band imaging (NBI) is a new imaging technology that was developed in 2006 and has since spread worldwide. Because of its convenience, NBI has been replacing the role of chromoendoscopy. Here we review the efficacy of NBI with/without magnification for detection, characterization, and management of colorectal polyps, and future perspectives for the technology, including education. Recent studies have shown that the next-generation NBI system can detect significantly more colonic polyps than white light imaging, suggesting that NBI may become the modality of choice from the beginning of screening. The capillary pattern revealed by NBI, and the NBI International Colorectal Endoscopic classification are helpful for prediction of histology and for estimating the depth of invasion of colorectal cancer. However, NBI with magnifying colonoscopy is not superior to magnifying chromoendoscopy for estimation of invasion depth. Currently, therefore, chromoendoscopy should also be performed additionally if deep submucosal invasive cancer is suspected. If endoscopists become able to accurately estimate colorectal polyp pathology using NBI, this will allow adenomatous polyps to be resected and discarded; thus, reducing both the risk of polypectomy and costs. In order to achieve this goal, a suitable system for education and training in in vivo diagnostics will be necessary. PMID:26668794

  14. Narrow-band imaging observation of colorectal lesions using NICE classification to avoid discarding significant lesions

    PubMed Central

    Hattori, Santa; Iwatate, Mineo; Sano, Wataru; Hasuike, Noriaki; Kosaka, Hidekazu; Ikumoto, Taro; Kotaka, Masahito; Ichiyanagi, Akihiro; Ebisutani, Chikara; Hisano, Yasuko; Fujimori, Takahiro; Sano, Yasushi

    2014-01-01

    AIM: To assess the risk of failing to detect diminutive and small colorectal cancers with the “resect and discard” policy. METHODS: Patients who received colonoscopy and polypectomy were recruited in the retrospective study. Probable histology of the polyps was predicted by six colonoscopists by the use of NICE classification. The incidence of diminutive and small colorectal cancers and their endoscopic features were assessed. RESULTS: In total, we found 681 cases of diminutive (1-5 mm) lesions in 402 patients and 197 cases of small (6-9 mm) lesions in 151 patients. Based on pathology of the diminutive and small polyps, 105 and 18 were non-neoplastic polyps, 557 and 154 were low-grade adenomas, 18 and 24 were high-grade adenomas or intramucosal/submucosal (SM) scanty invasive carcinomas, 1 and 1 were SM-d carcinoma, respectively. The endoscopic features of invasive cancer were classified as NICE type 3 endoscopically. CONCLUSION: The risk of failing to detect diminutive and small colorectal invasive cancer with the “resect and discard” strategy might be avoided through the use of narrow-band imaging observation with the NICE classification scheme and magnifying endoscopy. PMID:25512769

  15. Narrow band gap and enhanced thermoelectricity in FeSb2.

    PubMed

    Sun, Peijie; Oeschler, Niels; Johnsen, Simon; Iversen, Bo B; Steglich, Frank

    2010-01-28

    FeSb(2) was recently identified as a narrow-gap semiconductor with indications of strong electron-electron correlations. In this manuscript, we report on systematic thermoelectric investigation of a number of FeSb(2) single crystals with varying carrier concentrations, together with two isoelectronically substituted FeSb(2-x)As(x) samples (x = 0.01 and 0.03) and two reference compounds FeAs(2) and RuSb(2). Typical behaviour associated with narrow bands and narrow gaps is only confirmed for the FeSb(2) and the FeSb(2-x)As(x) samples. The maximum absolute thermopower of FeSb(2) spans from 10 to 45 mV/K at around 10 K, greatly exceeding that of both FeAs(2) and RuSb(2). The relation between the carrier concentration and the maximum thermopower value is in approximate agreement with theoretical predictions of the electron-diffusion contribution which, however, requires an enhancement factor larger than 30. The isoelectronic substitution leads to a reduction of the thermal conductivity, but the charge-carrier mobility is also largely reduced due to doping-induced crystallographic defects or impurities. In combination with the high charge-carrier mobility and the enhanced thermoelectricity, FeSb(2) represents a promising candidate for thermoelectric cooling applications at cryogenic temperatures. PMID:20066185

  16. High-repetition-rate, narrow-band dye lasers with water as a solvent for dyes

    NASA Astrophysics Data System (ADS)

    Ray, Alok K.; Sinha, Sucharita; Kundu, Soumitra; Kumar, Sasi; Nair, Sivagiriyal Karunakaran Sreenivasan; Pal, Tamal; Dasgupta, Kamalesh

    2002-03-01

    The performance of a copper vapor laser-pumped narrow-band dye laser in oscillator-amplifier configuration with water-based binary mixture solvents is described. Although oscillator efficiency in water-surfactant (sodium lauryl sulfate) solvent was comparable with that that employed pure ethanolic solvent, amplifier efficiency was found to be lower. Experiments that were carried out with vertically polarized pump beams and either horizontally or vertically polarized signal beams show that, in case of both the pump and signal having orthogonal polarization (horizontal) and same polarization (vertical), the extraction efficiency for both ethanolic and water-micelle media increased substantially from 15.7% to 18.5% and from 10% to 12.5%, respectively. However, the relative difference remained nearly the same, indicating that a slower orientational diffusion of excited dye molecules in a micellar medium is not responsible for a decrease in amplifier efficiency. Amplifier efficiency comparable with that containing ethanolic dye solutions could be obtained with a binary solvent that comprises a mixture of water and about 30% n-propanol. The performances of two efficient dyes, Rhodamine-6G and Kiton Red S, using water-based solvents were studied.

  17. Narrow-band imaging in the diagnosis of vascular nasal lesions.

    PubMed

    Torretta, Sara; Gaffuri, Michele; Cantarella, Giovanna; Pignataro, Lorenzo

    2013-01-01

    The management of unilateral nasal lesions can sometimes be a challenge and an ordinary bioptic assessment should be avoided in order to prevent complications due to their possible vascular or meningoencephalic origin. Narrow-band imaging (NBI) endoscopy could improve the diagnosis of vascular nasal formations by enhancing the visualisation of the mucosal microvascular supply. We describe the case of a 68-year-old male patient who was brought to our attention because of a left nasopharyngeal mass that had elsewhere been unsuccessfully biopsied (with conspicuous bleeding) and assessed by means of traditional endoscopic and radiological techniques. NBI endoscopy revealed increased vasculature covering most of the mucosal surface without any features suggestive for malignancy. Subsequent angiography showed that the feeding vessel was the left sphenopalatine artery, which was embolised using 150-250 μm Contour embospheres. The mass was then completely removed surgically using an NBI-assisted endoscopic technique, and a histopathological examination revealed it was a hemangiopericytoma-like (HPCL) tumor. This case suggests the usefulness of NBI endoscopy in diagnosing unilateral vascularised nasal lesions and guiding the therapeutic approach before and during major surgery. PMID:23218114

  18. "Leopard skin sign": the use of narrow-band imaging with magnification endoscopy in celiac disease.

    PubMed

    Tchekmedyian, Asadur J; Coronel, Emmanuel; Czul, Frank

    2014-01-01

    Celiac Disease (CD) is an immune reaction to gluten containing foods such as rye, wheat and barley. This condition affects individuals with a genetic predisposition; it targets the small bowel and may cause symptoms including diarrhea, malabsorption, weight loss, abdominal pain and bloating. The diagnosis is made by serologic testing of celiac-specific antibodies and confirmed by histology. Certain endoscopic characteristics, such as scalloping, reduction in the number of folds, mosaic-pattern mucosa or nodular mucosa, are suggestive of CD and can be visualized under white light endoscopy. Due to its low sensitivity, endoscopy alone is not recommended to diagnose CD; however, enhanced visual identification of suspected mucosal abnormalities through the use of new technologies, such as narrow band imaging with magnification (NBI-ME), could assist in targeting biopsies and thereby increasing the sensitivity of endoscopy. This is a case series of seven patients with serologic and histologic diagnoses of CD who underwent upper endoscopies with NBI-ME imaging technology as part of their CD evaluation. By employing this imaging technology, we could identify patchy atrophy sites in a mosaic pattern, with flattened villi and alteration of the central capillaries of the duodenal mucosa. We refer to this epithelial pattern as "Leopard Skin Sign". Since epithelial lesions are easily seen using NBI-ME, we found it beneficial for identifying and targeting biopsy sites. Larger prospective studies are warranted to confirm our findings. PMID:25594756

  19. Intercomparison of tunable diode laser and gas filter correlation measurements of ambient carbon monoxide

    NASA Astrophysics Data System (ADS)

    Fried, Alan; Henry, Bruce; Parrish, David D.; Carpenter, James R.; Buhr, Martin P.

    An intercomparison that involved a standards intercomparison, interferant spiking tests and simultaneous ambient measurements was carried out between two CO measurement systems: a tunable diode laser absorption spectrometer (TDLAS) and a gas filter correlation, non-dispersive infrared absorption instrument (GFC). Both the TDLAS and the GFC techniques responded to CO. No major interferences were found for the TDLAS system; tested species included H 2O, O 3 and OCS. The GFC instrument exhibited no interference from H 2O or O 3, but only a relatively high upper limit could be placed on the O 3 interference. For CO measurements in ambient air at levels from 100 to 1500 ppbv, the results from the two instruments agreed within their combined uncertainties. On average the GFC technique was 6% higher than the TDLAS system, and there was no systematic, constant offset. The precision of the GFC instrument was about 10%, and the precision of the TDLAS system was better than 4%.

  20. New electronically tunable current-mode universal biquad filter using translinear current conveyors

    NASA Astrophysics Data System (ADS)

    Kumngern, Montree; Jongchanachavawat, Wirote; Dejhan, Kobchai

    2010-05-01

    In this study, a new electronically tunable current-mode universal filter with two inputs and two outputs employing one translinear current conveyor, one translinear current conveyor with controlled current gain and two grounded capacitors is presented. The proposed circuit offers the following attractive features: realisation of low-pass, band-pass, high-pass, band-stop and all-pass current responses from the same configuration; employment of the minimum active and passive components; no requirement of component matching conditions; independent current-control of the parameters natural frequency (ωo) and quality factor (Q); low active and passive sensitivities; and high impedance output. The characteristics of the proposed circuit are simulated using PSPICE to confirm the theory.

  1. Tunable bandpass microwave photonic filter with ultrahigh stopband attenuation and skirt selectivity.

    PubMed

    Jiang, Fan; Yu, Yuan; Tang, Haitao; Xu, Lu; Zhang, Xinliang

    2016-08-01

    we propose and demonstrate a bandpass microwave photonic filter (MPF) with ultrahigh stopband attenuation and skirt selectivity based on a simple signal cancellation technique. By injecting two phase modulated signals located on opposite sides of two resonant gain peaks of a Fabry-Pérot semiconductor optical amplifier (FP-SOA), two microwave frequency responses can be generated by the two input signals, respectively. The two frequency responses will add together within the passband but cancel each other out within the stopband, thus generating a MPF with simultaneous ultrahigh stopband attenuation and skirt selectivity. In the experiment the obtained MPF exhibits single passband in the range from 0 to 18 GHz and is tunable from 4 to 16 GHz by adjusting the laser wavelengths. During the tuning process the maximum stopband attenuation is 76.3 dB and the minimum 30-dB to 3-dB bandwidth shape factor is 3.5. PMID:27505828

  2. Correlated color temperature tunable white LED with a dynamic color filter.

    PubMed

    Chen, Haiwei; Zhu, Ruidong; Lee, Yun-Han; Wu, Shin-Tson

    2016-03-21

    We proposed a new device structure to dynamically tune the correlated color temperature (CCT) of a white light-emitting-diode (WLED). The key component is a dynamic color filter, consisting of a liquid crystal (LC) cell sandwiched between two cholesteric LC films whose Bragg reflection band covers the blue wavelength of the WLED. When a voltage is applied to the LC cell, the transmittance of blue light is changed, while the longer wavelength part remains unaffected, resulting in a tunable CCT. Validated by experiment, our design exhibits several advantages, such as reasonably wide tuning range (6916K to 3253K), low operation voltage (~3.2 V), simple device configuration, and low cost. It is a strong contender for next generation smart lighting. PMID:27136890

  3. 47 CFR 80.361 - Frequencies for narrow-band direct-printing (NBDP), radioprinter and data transmissions.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Frequencies for narrow-band direct-printing (NBDP), radioprinter and data transmissions. 80.361 Section 80.361 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES STATIONS IN THE MARITIME SERVICES Frequencies Radiotelegraphy § 80.361 Frequencies...

  4. 47 CFR 80.219 - Special requirements for narrow-band direct-printing (NB-DP) equipment.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Special requirements for narrow-band direct-printing (NB-DP) equipment. 80.219 Section 80.219 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES STATIONS IN THE MARITIME SERVICES General Technical Standards § 80.219 Special requirements...

  5. 47 CFR 80.219 - Special requirements for narrow-band direct-printing (NB-DP) equipment.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... reference in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies of these standards can be inspected...-printing (NB-DP) equipment. 80.219 Section 80.219 Telecommunication FEDERAL COMMUNICATIONS COMMISSION... § 80.219 Special requirements for narrow-band direct-printing (NB-DP) equipment. NB-DP and...

  6. 47 CFR 80.219 - Special requirements for narrow-band direct-printing (NB-DP) equipment.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...-printing (NB-DP) equipment. 80.219 Section 80.219 Telecommunication FEDERAL COMMUNICATIONS COMMISSION... § 80.219 Special requirements for narrow-band direct-printing (NB-DP) equipment. NB-DP and data...-DP and data transmission equipment are additionally permitted to utilize any modulation, so long...

  7. 47 CFR 80.219 - Special requirements for narrow-band direct-printing (NB-DP) equipment.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...-printing (NB-DP) equipment. 80.219 Section 80.219 Telecommunication FEDERAL COMMUNICATIONS COMMISSION... § 80.219 Special requirements for narrow-band direct-printing (NB-DP) equipment. NB-DP and data...-DP and data transmission equipment are additionally permitted to utilize any modulation, so long...

  8. 47 CFR 80.219 - Special requirements for narrow-band direct-printing (NB-DP) equipment.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...-printing (NB-DP) equipment. 80.219 Section 80.219 Telecommunication FEDERAL COMMUNICATIONS COMMISSION... § 80.219 Special requirements for narrow-band direct-printing (NB-DP) equipment. NB-DP and data...-DP and data transmission equipment are additionally permitted to utilize any modulation, so long...

  9. Synchrotron Studies of Narrow Band and Low-Dimensional Materials. Final Report for July 1, 1990---December 31, 2002

    SciTech Connect

    Allen, J. W.

    2003-05-13

    This report summarizes a 12-year program of various kinds of synchrotron spectroscopies directed at the electronic structures of narrow band and low-dimensional materials that display correlated electron behaviors such as metal-insulator transitions, mixed valence, superconductivity, Kondo moment quenching, heavy Fermions, and non-Fermi liquid properties.

  10. Very narrow band model calculations of atmospheric fluxes and cooling rates

    SciTech Connect

    Bernstein, L.S.; Berk, A.; Acharya, P.K.; Robertson, D.C.

    1996-10-15

    A new very narrow band model (VNBM) approach has been developed and incorporated into the MODTRAN atmospheric transmittance-radiance code. The VNBM includes a computational spectral resolution of 1 cm{sup {minus}1}, a single-line Voigt equivalent width formalism that is based on the Rodgers-Williams approximation and accounts for the finite spectral width of the interval, explicit consideration of line tails, a statistical line overlap correction, a new sublayer integration approach that treats the effect of the sublayer temperature gradient on the path radiance, and the Curtis-Godson (CG) approximation for inhomogeneous paths. A modified procedure for determining the line density parameter 1/d is introduced, which reduces its magnitude. This results in a partial correction of the VNBM tendency to overestimate the interval equivalent widths. The standard two parameter CG approximation is used for H{sub 2}O and CO{sub 2}, while the Goody three parameter CG approximation is used for O{sub 3}. Atmospheric flux and cooling rate predictions using a research version of MODTRAN, MODR, are presented for H{sub 2}O (with and without the continuum), CO{sub 2}, and O{sub 3} for several model atmospheres. The effect of doubling the CO{sub 2} concentration is also considered. These calculations are compared to line-by-line (LBL) model calculations using the AER, GLA, GFDL, and GISS codes. The MODR predictions fall within the spread of the LBL results. The effects of decreasing the band model spectral resolution are illustrated using CO{sub 2} cooling rate and flux calculations. 36 refs., 18 figs., 1 tab.

  11. Reversal of Atopic Dermatitis with Narrow-Band UVB Phototherapy and Biomarkers for Therapeutic Response

    PubMed Central

    Tintle, Suzanne; Shemer, Avner; Suárez-Fariñas, Mayte; Fujita, Hideki; Gilleaudeau, Patricia; Sullivan-Whalen, Mary; Johnson-Huang, Leanne; Chiricozzi, Andrea; Cardinale, Irma; Duan, Shenghui; Bowcock, Anne; Krueger, James G.; Guttman-Yassky, Emma

    2012-01-01

    Background Atopic dermatitis (AD) is a common inflammatory skin disease exhibiting a predominantly Th2/“T22” immune activation and a defective epidermal barrier. Narrow-band UVB (NB-UVB) is considered an efficient treatment for moderate-to-severe AD. In psoriasis, NB-UVB has been found to suppress the Th1/Th17-polarization with subsequent reversal of epidermal hyperplasia. The immunomodulatory effects of this treatment are largely unknown in AD. Objective To evaluate the effects of NB-UVB on immune and barrier abnormalities in AD, aiming to establish reversibility of disease and biomarkers of therapeutic response. Methods 12 moderate-to-severe chronic AD patients received NB-UVB phototherapy 3 times weekly for up to 12 weeks. Lesional and non-lesional skin biopsies were obtained before and after treatment and evaluated by gene-expression and immunohistochemistry studies. Results All patients had at least a 50% reduction in SCORing of AD (SCORAD) index with NB-UVB phototherapy. The Th2, “T22,” and Th1 immune pathways were suppressed and measures of epidermal hyperplasia and differentiation normalized. The reversal of disease activity was associated with elimination of inflammatory leukocytes, Th2/“T22”- associated cytokines and chemokines, and normalized expression of barrier proteins. Conclusions Our study shows that resolution of clinical disease in patients with chronic AD is accompanied by reversal of both the epidermal defects and the underlying immune activation. We have defined a set of biomarkers of disease response that associate resolved Th2 and “T22” inflammation in chronic AD patients with reversal of barrier pathology. By showing reversal of the AD epidermal phenotype with a broad immune-targeted therapy, our data argues against a fixed genetic phenotype. PMID:21762976

  12. Differential Expression of TGF-β Isoforms in Human Kerationocytes by Narrow Band UVB

    PubMed Central

    Jung, Moon Chul; Shin, Min Kyung; Hong, Kyung Kook; Jeong, Ki Heon

    2008-01-01

    Background Transforming growth factor-β (TGF-β), a multifunctional growth factor, has three isoforms: TGF-β1, TGF-β2, and TGF-β3. Different isoforms of TGF-β are associated with different proliferation and differentiation states of the epidermis. Narrow band ultraviolet B (NBUVB) emits a concentrated UVB source of 311 nm. NBUVB 1,000 mJ/cm2 induces apoptosis in approximately 50% of keratinocytes. Objective The purpose of this study was to evaluate whether irradiation with NBUVB would alter the expression and production of TGF-β1, 2, and 3. Methods We measured TGF-β1, 2, and 3 mRNA and TGF-β1 and 2 protein levels at 800, 1,000, and 1,200 mJ/cm2 for 24 hours and 48 hours. Results TGF-β1 mRNA levels were increased at both 24 hr and 48 hr, TGF-β2 mRNA levels were decreased at both 24 hr and 48 hr, and TGF-β3 mRNA levels were increased at 24 hr and similar to control at 48 hr. TGF-β1 protein levels were increased at 48 hr but decreased at 24 hr. TGF-β2 protein levels were decreased at both 24 hr and 48 hr. Conclusion The results suggest a possible role for TGF-β1 after NBUVB irradiation and opposing roles for TGF-β1 and TGF-β2 isoforms in NBUVB irradiation. PMID:27303173

  13. Usefulness of magnifying endoscopy with narrow-band imaging for diagnosis of depressed gastric lesions.

    PubMed

    Sumie, Hiroaki; Sumie, Shuji; Nakahara, Keita; Watanabe, Yasutomo; Matsuo, Ken; Mukasa, Michita; Sakai, Takeshi; Yoshida, Hikaru; Tsuruta, Osamu; Sata, Michio

    2014-01-01

    The usefulness of magnifying endoscopy with narrow-band imaging (ME-NBI) for the diagnosis of early gastric cancer is well known, however, there are no evaluation criteria. The aim of this study was to devise and evaluate a novel diagnostic algorithm for ME-NBI in depressed early gastric cancer. Between August, 2007 and May, 2011, 90 patients with a total of 110 depressed gastric lesions were enrolled in the study. A diagnostic algorithm was devised based on ME-NBI microvascular findings: microvascular irregularity and abnormal microvascular patterns (fine network, corkscrew and unclassified patterns). The diagnostic efficiency of the algorithm for gastric cancer and histological grade was assessed by measuring its mean sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy. Furthermore, inter- and intra-observer variation were measured. In the differential diagnosis of gastric cancer from non-cancerous lesions, the mean sensitivity, specificity, PPV, NPV, and accuracy of the diagnostic algorithm were 86.7, 48.0, 94.4, 26.7, and 83.2%, respectively. Furthermore, in the differential diagnosis of undifferentiated adenocarcinoma from differentiated adenocarcinoma, the mean sensitivity, specificity, PPV, NPV, and accuracy of the diagnostic algorithm were 61.6, 86.3, 69.0, 84.8, and 79.1%, respectively. For the ME-NBI final diagnosis using this algorithm, the mean κ values for inter- and intra-observer agreement were 0.50 and 0.77, respectively. In conclusion, the diagnostic algorithm based on ME-NBI microvascular findings was convenient and had high diagnostic accuracy, reliability and reproducibility in the differential diagnosis of depressed gastric lesions. PMID:24649321

  14. Narrow band quantitative and multivariate electroencephalogram analysis of peri-adolescent period

    PubMed Central

    2012-01-01

    Background The peri-adolescent period is a crucial developmental moment of transition from childhood to emergent adulthood. The present report analyses the differences in Power Spectrum (PS) of the Electroencephalogram (EEG) between late childhood (24 children between 8 and 13 years old) and young adulthood (24 young adults between 18 and 23 years old). Results The narrow band analysis of the Electroencephalogram was computed in the frequency range of 0–20 Hz. The analysis of mean and variance suggested that six frequency ranges presented a different rate of maturation at these ages, namely: low delta, delta-theta, low alpha, high alpha, low beta and high beta. For most of these bands the maturation seems to occur later in anterior sites than posterior sites. Correlational analysis showed a lower pattern of correlation between different frequencies in children than in young adults, suggesting a certain asynchrony in the maturation of different rhythms. The topographical analysis revealed similar topographies of the different rhythms in children and young adults. Principal Component Analysis (PCA) demonstrated the same internal structure for the Electroencephalogram of both age groups. Principal Component Analysis allowed to separate four subcomponents in the alpha range. All these subcomponents peaked at a lower frequency in children than in young adults. Conclusions The present approaches complement and solve some of the incertitudes when the classical brain broad rhythm analysis is applied. Children have a higher absolute power than young adults for frequency ranges between 0-20 Hz, the correlation of Power Spectrum (PS) with age and the variance age comparison showed that there are six ranges of frequencies that can distinguish the level of EEG maturation in children and adults. The establishment of maturational order of different frequencies and its possible maturational interdependence would require a complete series including all the different ages. PMID

  15. Therapeutic or spontaneous Helicobacter pylori eradication can obscure magnifying narrow-band imaging of gastric tumors

    PubMed Central

    Kobayashi, Masaaki; Hashimoto, Satoru; Mizuno, Ken-ichi; Takeuchi, Manabu; Sato, Yuichi; Watanabe, Gen; Ajioka, Yoichi; Azumi, Motoi; Akazawa, Kouhei; Terai, Shuji

    2016-01-01

    Background and study aims: We previously reported that narrow-band imaging with magnifying endoscopy (NBI-ME) revealed a unique “gastritis-like” appearance in approximately 40 % of early gastric cancers after Helicobacter pylori eradication. Because rates of gastric cancer are increasing in patients with non-persistent infection of H. pylori, we aimed to clarify contribution factors to obscure tumors after therapeutic or spontaneous eradication. Patients and methods: NBI-ME findings were examined retrospectively in 194 differentiated-type adenocarcinomas from H. pylori-negative patients with prior eradication therapy (83 patients) or without prior eradication therapy (72 patients). A gastritis-like appearance under NBI-ME was defined as an orderly microsurface structure and/or loss of clear demarcation with resemblance to the adjacent, non-cancerous mucosa. The correlation of this phenomenon with the degree of atrophic gastritis, determined both histologically in the adjacent mucosa and endoscopically, was evaluated. Results: The tumor-obscuring gastritis-like appearance was observed in 42 % and 23 % of the patients in the H. pylori eradication and non-eradication groups, respectively. The development of this appearance was affected by the histological grade of atrophy (P = 0.003) and intestinal metaplasia (P < 0.001) on univariate analysis. Multivariate analysis revealed an odds ratio of 0.25 (95 % confidence interval 0.10 – 0.61, P = 0.002) for an endoscopically severe extent of atrophy, independently of eradication therapy. Conclusions: An endoscopically mild or moderate extent of atrophy is associated with a gastritis-like appearance under NBI-ME in currently H. pylori-negative gastric cancers. Surveillance endoscopy should be performed carefully after successful eradication or spontaneous elimination of H. pylori, particularly in patients with non-severe atrophic background mucosa. PMID:27556076

  16. Advantage of transurethral resection with narrow band imaging for non-muscle invasive bladder cancer

    PubMed Central

    KOBATAKE, KOHEI; MITA, KOJI; OHARA, SHINYA; KATO, MASAO

    2015-01-01

    The aim of the present study was to compare the benefits of transurethral resection (TUR) under narrow band imaging (NBI-TUR) and TUR under conventional white light imaging (WLI-TUR) for non-muscle invasive bladder cancer (NMIBC). The study cohort consisted of 135 patients with NMIBC who were followed up for ≥1 year after TUR and who received no additional post-operative treatment. In the WLI-TUR group (n=78), systematic intravesical observation under WLI was followed by a multiple site biopsy (MSB), after which lesions detected as positive findings were resected completely under WLI. In the NBI-TUR group (n=57), similar observation under WLI was followed by systematic intravesical observation under NBI. Following MSB under NBI, TUR was performed for all lesions detected as positive findings under NBI. The sensitivity, specificity, positive-predictive value, negative-predictive value (NPV) and accuracy in the NBI-TUR group were calculated using results from the cystoscopical and pathological examinations of MSB samples under WLI and NBI. The tumor recurrence rate was analyzed in the two groups. Background factors did not differ significantly between the two groups, with the exception of the observation period (31.0 vs. 15.0 months; P<0.01). The procedure under NBI exhibited significantly higher sensitivity (95.0 vs. 70.0%; P<0.01) and NPV (97.1 vs. 86.8%; P<0.01) compared with the procedure under WLI. The 1-year recurrence rate in the NBI-TUR group was significantly lower than that in the WLI-TUR group (21.1 vs. 39.7%; P=0.016). In conclusion, the present study indicated that NBI-TUR is more advantageous than conventional WLI-TUR for patients with NMIBC. PMID:26622632

  17. Narrow-band imaging for the computer assisted diagnosis in patients with Barrett's esophagus

    NASA Astrophysics Data System (ADS)

    Kage, Andreas; Raithel, Martin; Zopf, Steffen; Wittenberg, Thomas; Münzenmayer, Christian

    2009-02-01

    Cancer of the esophagus has the worst prediction of all known cancers in Germany. The early detection of suspicious changes in the esophagus allows therapies that can prevent the cancer. Barrett's esophagus is a premalignant change of the esophagus that is a strong indication for cancer. Therefore there is a big interest to detect Barrett's esophagus as early as possible. The standard examination is done with a videoscope where the physician checks the esophagus for suspicious regions. Once a suspicious region is found, the physician takes a biopsy of that region to get a histological result of it. Besides the traditional white light for the illumination there is a new technology: the so called narrow-band Imaging (NBI). This technology uses a smaller spectrum of the visible light to highlight the scene captured by the videoscope. Medical studies indicate that the use of NBI instead of white light can increase the rate of correct diagnoses of a physician. In the future, Computer-Assisted Diagnosis (CAD) which is well known in the area of mammography might be used to support the physician in the diagnosis of different lesions in the esophagus. A knowledge-based system which uses a database is a possible solution for this task. For our work we have collected NBI images containing 326 Regions of Interest (ROI) of three typical classes: epithelium, cardia mucosa and Barrett's esophagus. We then used standard texture analysis features like those proposed by Haralick, Chen, Gabor and Unser to extract features from every ROI. The performance of the classification was evaluated with a classifier using the leaving-one-out sampling. The best result that was achieved is an accuracy of 92% for all classes and an accuracy of 76% for Barrett's esophagus. These results show that the NBI technology can provide a good diagnosis support when used in a CAD system.

  18. Rapid spontaneous Raman light sheet microscopy using cw-lasers and tunable filters

    PubMed Central

    Rocha-Mendoza, Israel; Licea-Rodriguez, Jacob; Marro, Mónica; Olarte, Omar E.; Plata-Sanchez, Marcos; Loza-Alvarez, Pablo

    2015-01-01

    We perform rapid spontaneous Raman 2D imaging in light-sheet microscopy using continuous wave lasers and interferometric tunable filters. By angularly tuning the filter, the cut-on/off edge transitions are scanned along the excited Stokes wavelengths. This allows obtaining cumulative intensity profiles of the scanned vibrational bands, which are recorded on image stacks; resembling a spectral version of the knife-edge technique to measure intensity profiles. A further differentiation of the stack retrieves the Raman spectra at each pixel of the image which inherits the 3D resolution of the host light sheet system. We demonstrate this technique using solvent solutions and composites of polystyrene beads and lipid droplets immersed in agar and by imaging the C–H (2800-3100cm−1) region in a C. elegans worm. The image acquisition time results in 4 orders of magnitude faster than confocal point scanning Raman systems, allowing the possibility of performing fast spontaneous Raman·3D-imaging on biological samples. PMID:26417514

  19. Acousto-optic tunable filter for dispersion characterization of time-domain optical coherence tomography systems.

    PubMed

    Chin, Catherine; Toadere, Florin; Feuchter, Thomas; Leick, Lasse; Moselund, Peter; Bradu, Adrian; Podoleanu, Adrian

    2016-07-20

    A broadband supercontinuum light source with an acousto-optic tunable filter (AOTF) are used to characterize dispersion in two time-domain OCT systems, at 850 and 1300 nm. The filter is designed to sweep across two spectral ranges, which are restricted here from 800 to 900 nm and from 1200 to 1500 nm, respectively. Dispersion compensation for 850 nm was achieved with a spectral delay line. Dispersion compensation for 1300 nm was achieved using BK 7 rod glasses in the reference arm. The AOTF allows evaluation of dispersion in under as well as overcompensated systems. The AOTF method is based on wavelength dependence of the optical path difference corresponding to the maximum strength of the interference signal recorded using a mirror as object. Comparison is made between the AOTF method and the more usual method based on measurement of the full width at half-maximum of the autocorrelation peak. This comparison shows that the AOTF method is more accurate in terms of evaluation of the dispersion left uncompensated after each adjustment. The AOTF method additionally provides information on the direction of dispersion compensation. PMID:27463927

  20. Tunable microwave bandpass filter integrated power divider based on the high anisotropy electro-optic nematic liquid crystal.

    PubMed

    Liu, Yupeng; Liu, Yang; Li, Haiyan; Jiang, Di; Cao, Weiping; Chen, Hui; Xia, Lei; Xu, Ruimin

    2016-07-01

    A novel, compact microwave tunable bandpass filter integrated power divider, based on the high anisotropy electro-optic nematic liquid crystal, is proposed in this letter. Liquid crystal, as the electro-optic material, is placed between top inverted microstrip line and the metal plate. The proposed structure can realize continuous tunable bandpass response and miniaturization. The proposed design concept is validated by the good performance of simulation results and experimental results. The electro-optic material has shown great potential for microwave application. PMID:27475583

  1. Tunable microwave bandpass filter integrated power divider based on the high anisotropy electro-optic nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Liu, Yupeng; Liu, Yang; Li, Haiyan; Jiang, Di; Cao, Weiping; Chen, Hui; Xia, Lei; Xu, Ruimin

    2016-07-01

    A novel, compact microwave tunable bandpass filter integrated power divider, based on the high anisotropy electro-optic nematic liquid crystal, is proposed in this letter. Liquid crystal, as the electro-optic material, is placed between top inverted microstrip line and the metal plate. The proposed structure can realize continuous tunable bandpass response and miniaturization. The proposed design concept is validated by the good performance of simulation results and experimental results. The electro-optic material has shown great potential for microwave application.

  2. Tunable photonic microwave notch filter using SOA-based single-longitudinal mode, dual-wavelength laser.

    PubMed

    Lee, Kwanil; Lee, Ju Han; Lee, Sang Bae

    2009-07-20

    A novel photonic microwave notch filter with capability of frequency tuning is proposed and experimentally demonstrated. The scheme is based on a fiber Bragg grating (FBG)-based, single longitudinal mode, wavelength-spacing tunable dual-wavelength fiber laser and a dispersive fiber delay line. By using a symmetrical S-bending technique along the FBGs, the wavelength spacing of the laser can be tuned, which enables the microwave notch frequency tuning. Experimental results show that the notch rejection of more than 30 dB and the flexible tunability of notch frequency can be readily achieved in the range of 1.2 approximately 6.7 GHz. PMID:19654727

  3. Power-stabilized tunable narrow-band source using a VCSEL and an EDFA for FBG sensor interrogation

    NASA Astrophysics Data System (ADS)

    Mizunami, Toru; Hirose, Shuji; Yoshinaga, Takeshi; Yamamoto, Ken-ichi

    2013-09-01

    Wavelength tuning with a current of a long-wavelength vertical-cavity surface-emitting laser (VCSEL) was studied for application to wavelength readout of fiber Bragg grating (FBG) sensors. 1.5 µm single-longitudinal-mode VCSELs with a spectral line width of 30 MHz were used. To decrease the variation in the output power with the current, saturated amplification of the VCSEL output by an erbium-doped fiber amplifier (EDFA) was proposed. In the experiment, the wavelength readout of an FBG by variation in the VCSEL current was studied first, and then amplification characteristics using a commercially available EDFA module were measured. Two VCSELs with different wavelengths and tuning ranges were used as input and compared. For a VCSEL with a wavelength tuning range of 2.5 nm, there was a threefold change in the VCSEL output power. However, the variation in the amplified output power was within ±14%. For another VCSEL with a wavelength tuning range of 3.9 nm, the variation in the amplified output power was within ±18% for variation in the VCSEL output power by 2.2 times. The power slope with respect to the wavelength was also decreased by the stabilization. Computer simulation was performed to study the wavelength shift in the measured Bragg wavelength induced by the power slope. The simulation showed that the wavelength shift can be reduced to 1/2.5-1/5 by the stabilization compared with that using a single VCSEL. Application to long-period grating sensors was also discussed.

  4. Modulation transfer function testing of detector arrays using narrow-band laser speckle

    NASA Astrophysics Data System (ADS)

    Sensiper, Martin; Boreman, Glenn D.; Ducharme, Alfred D.; Snyder, Donald R.

    1993-02-01

    A method for measuring the modulation transfer function (MTF) of a detector array from zero spatial frequency to twice the Nyquist frequency is presented. Laser speckle with a tunable, narrow spatial-frequency bandpass is used. The MTF measured with this method is compared to the MTF measured using sine targets. The results of the two methods agree to within 2%.

  5. Modulation transfer function testing of FPA using narrow-band laser speckle

    NASA Astrophysics Data System (ADS)

    Hua, Qing; Zheng, Wenlong; Li, Yuguang; Liang, Yinzhong; He, Ping'an; Li, Song; Xu, Jing

    2000-10-01

    This paper shows an approach using tunable narrowband speckle pattern generated by a double-slit aperture laid behind a new microcrystalline glass material scattering screen, for testing MTF of FPA between zero and twice Nyquist frequency. The measurement near to the Nyquist frequency, this method proved highly effective much better than that obtained by the Wide-band Laser Speckle.

  6. Discretely tunable Tm-doped fiber-based MOPA using FBG arrays as spectral filters

    NASA Astrophysics Data System (ADS)

    Tiess, T.; Junaid, S.; Becker, M.; Rothhardt, M.; Bartelt, H.; Jäger, M.

    2016-03-01

    Over the past years, Thulium (Tm) -doped fiber lasers in the 2μm region have gained a lot of interest due to many potential applications in materials processing and biophotonics. Based on the broad gain regions spanning from 1800nm to 2100nm, they offer the perfect basis to implement broadly tunable and user-friendly light sources like they are increasingly demanded in spectroscopic applications. Recently, a novel tuning mechanism based on a fiber Bragg grating (FBG) array as versatile spectral filter has been reported. This concept combines unique spectral freedom for customized tuning ranges and ultrabroad bandwidths with a fiber-integrated setup in order to maintain the advantages of the waveguide geometry. In this work, we demonstrate such a dispersion tuned and pulsed fiber laser in the Tm domain around 1950nm using a modulator and a discrete FBG array to control the emission wavelength. In order to comply with the demands of potential applications in biophotonics, for the first time, this tuning concept is realized in a polarization maintaining (PM) configuration ensuring linearly polarized output. While a simple FBG array is employed containing five gratings inscribed in PM fiber, we also outline the prospect to implement FBGs fabricated in a standard single mode fiber. The emission characteristics of the system are investigated showing pulse durations down to 11ns and a good spectral signal contrast. In order to highlight the prospect for tunable high-power operation, we have also implemented an amplification stage scaling the average power to more than 25W.

  7. The simulation and improved design of tunable channel drop filter using hexagonal photonic crystal ring resonator

    SciTech Connect

    Chhipa, Mayur Kumar

    2014-10-15

    In this paper, we have proposed a new design of tunable two dimensional (2D) photonic crystal (PhC) channel drop filter (CDF) using ring resonators. The increasing interest in photonic integrated circuits (PIC's) and the increasing use of all-optical fiber networks as backbones for global communication systems have been based in large part on the extremely wide optical transmission bandwidth provided by dielectric materials. Based on the analysis we present novel photonic crystal channel drop filters. Simulations demonstrate that these filters exhibit ideal transfer characteristics. Channel dropping filters (CDF's) that access one channel of a wavelength division multiplexed (WDM) signal while leaving other channels undisturbed are essential components of PIC's and optical communication systems. In this paper we have investigated such parameters which have an effect on resonant wavelength in this Channel Drop Filter, such as dielectric constant of inner, coupling, adjacent and whole rods of the structure. The dimensions of these structures are taken as 20a×19a and the area of the proposed structure is about 125.6μm{sup 2}; therefore this structure can be used in the future photonic integrated circuits. While using this design the dropping efficiency at the resonance of single ring are 100%. The spectrum of the power transmission is obtained with finite difference time domain (FDTD) method. FDTD method is the most famous method for PhC analysis. In this paper the dielectric rods have a dielectric constant of 10.65, so the refractive index is 3.26 and radius r=0.213a is located in air, where a is a lattice constant. In this we have used five scatter rods for obtaining more coupling efficiency; radius of scatter rods is set to 0.215a. The proposed structure is simulated with OptiFDTD.v.8.0 software, the different dielectric constant of rods equal to ε{sub r}−0.4, ε{sub r} and ε{sub r}+0.4 at wavelength of 1570 nm.

  8. The simulation & improved design of tunable channel drop filter using hexagonal photonic crystal ring resonator

    NASA Astrophysics Data System (ADS)

    Chhipa, Mayur Kumar

    2014-10-01

    In this paper, we have proposed a new design of tunable two dimensional (2D) photonic crystal (PhC) channel drop filter (CDF) using ring resonators. The increasing interest in photonic integrated circuits (PIC's) and the increasing use of all-optical fiber networks as backbones for global communication systems have been based in large part on the extremely wide optical transmission bandwidth provided by dielectric materials. Based on the analysis we present novel photonic crystal channel drop filters. Simulations demonstrate that these filters exhibit ideal transfer characteristics. Channel dropping filters (CDF's) that access one channel of a wavelength division multiplexed (WDM) signal while leaving other channels undisturbed are essential components of PIC's and optical communication systems. In this paper we have investigated such parameters which have an effect on resonant wavelength in this Channel Drop Filter, such as dielectric constant of inner, coupling, adjacent and whole rods of the structure. The dimensions of these structures are taken as 20a×19a and the area of the proposed structure is about 125.6μm2; therefore this structure can be used in the future photonic integrated circuits. While using this design the dropping efficiency at the resonance of single ring are 100%. The spectrum of the power transmission is obtained with finite difference time domain (FDTD) method. FDTD method is the most famous method for PhC analysis. In this paper the dielectric rods have a dielectric constant of 10.65, so the refractive index is 3.26 and radius r=0.213a is located in air, where a is a lattice constant. In this we have used five scatter rods for obtaining more coupling efficiency; radius of scatter rods is set to 0.215a. The proposed structure is simulated with OptiFDTD.v.8.0 software, the different dielectric constant of rods equal to ɛr-0.4, ɛr and ɛr+0.4 at wavelength of 1570 nm.

  9. Narrow-band imaging with magnifying endoscopy is accurate for detecting gastric intestinal metaplasia

    PubMed Central

    Savarino, Edoardo; Corbo, Marina; Dulbecco, Pietro; Gemignani, Lorenzo; Giambruno, Elisa; Mastracci, Luca; Grillo, Federica; Savarino, Vincenzo

    2013-01-01

    AIM: To investigate the predictive value of narrow-band imaging with magnifying endoscopy (NBI-ME) for identifying gastric intestinal metaplasia (GIM) in unselected patients. METHODS: We prospectively evaluated consecutive patients undergoing upper endoscopy for various indications, such as epigastric discomfort/pain, anaemia, gastro-oesophageal reflux disease, suspicion of peptic ulcer disease, or chronic liver diseases. Patients underwent NBI-ME, which was performed by three blinded, experienced endoscopists. In addition, five biopsies (2 antrum, 1 angulus, and 2 corpus) were taken and examined by two pathologists unaware of the endoscopic findings to determine the presence or absence of GIM. The correlation between light blue crest (LBC) appearance and histology was measured. Moreover, we quantified the degree of LBC appearance as less than 20% (+), 20%-80% (++) and more than 80% (+++) of an image field, and the semiquantitative evaluation of LBC appearance was correlated with IM percentage from the histological findings. RESULTS: We enrolled 100 (58 F/42 M) patients who were mainly referred for gastro-esophageal reflux disease/dyspepsia (46%), cancer screening/anaemia (34%), chronic liver disease (9%), and suspected celiac disease (6%); the remaining patients were referred for other indications. The prevalence of Helicobacter pylori (H. pylori) infection detected from the biopsies was 31%, while 67% of the patients used proton pump inhibitors. LBCs were found in the antrum of 33 patients (33%); 20 of the cases were classified as LBC+, 9 as LBC++, and 4 as LBC+++. LBCs were found in the gastric body of 6 patients (6%), with 5 of them also having LBCs in the antrum. The correlation between the appearance of LBCs and histological GIM was good, with a sensitivity of 80% (95%CI: 67-92), a specificity of 96% (95%CI: 93-99), a positive predictive value of 84% (95%CI: 73-96), a negative predictive value of 95% (95%CI: 92-98), and an accuracy of 93% (95%CI: 90-97). The

  10. Analysis of microvascular density in early gastric carcinoma using magnifying endoscopy with narrow-band imaging

    PubMed Central

    Kawamura, Masashi; Naganuma, Hiroshi; Shibuya, Rie; Kikuchi, Tatsuya; Sakai, Yoshitaka; Nagasaki, Futoshi; Nomura, Eiki; Suzuki, Noriaki; Saito, Eri

    2016-01-01

    Background and study aims: Intramucosal vascular density differs between differentiated and undifferentiated type gastric carcinomas. This study aimed to evaluate the microvascular density characteristics of these two types of carcinoma using magnifying endoscopy with narrow-band imaging (ME-NBI). Patients and methods: In total, 42 differentiated and 10 undifferentiated types were evaluated. The microvessels observed using ME-NBI were extracted from stored still images and the microvascular density in the two carcinoma types was analyzed. Histological vascular density in resected specimens was also evaluated using CD34 immunostaining. Results: There were significant differences between the microvascular density in the differentiated and undifferentiated types of carcinoma (10.02 ± 4.72 % vs 4.02 ± 0.40 %; P < 0.001) using ME-NBI. Vascular density assessed histologically also differed significantly between differentiated and undifferentiated types in both the whole mucosal (5.81 ± 3.17 % vs 3.25 ± 1.21 %) and the superficial mucosal layers (0 – 100 μm) (6.38 ± 3.73 % vs 3.66 ± 1.46 %). However, the vascular density in the surrounding non-carcinomatous mucosa assessed using ME-NBI and histologically, was significantly lower in the differentiated than in the undifferentiated types (P < 0.001). There was good agreement between ME-NBI and histologically assessed microvascular density in both the whole (r = 0.740; P < 0.001) and superficial mucosal layers (r = 0.764; P < 0.001). White opaque substance (WOS) was seen in eight patients who had the differentiated type carcinoma. In almost all cases with WOS, the appearance of the carcinoma was discolored. Conclusions: There was a close relationship between ME-NBI assessed microvascular density and histologically assessed vascular density in the mucosal layer. Microvascular density differed significantly between the differentiated and undifferentiated

  11. Acousto-Optic Tunable Filter Spectroscopic Instrumentation for Quantitative Near-Ir Analysis of Organic Materials.

    NASA Astrophysics Data System (ADS)

    Eilert, Arnold James

    1995-01-01

    The utility of near-IR spectroscopy for routine quantitative analyses of a wide variety of compositional, chemical, or physical parameters of organic materials is well understood. It can be used for relatively fast and inexpensive non-destructive bulk material analysis before, during, and after processing. It has been demonstrated as being a particularly useful technique for numerous analytical applications in cereal (food and feed) science and industry. Further fulfillment of the potential of near-IR spectroscopic analysis, both in the process and laboratory environment, is reliant upon the development of instrumentation that is capable of meeting the challenges of increasingly difficult applications. One approach to the development of near-IR spectroscopic instrumentation that holds a great deal of promise is acousto-optic tunable filter (AOTF) technology. A combination of attributes offered by AOTF spectrometry, including speed, optical throughput, wavelength reproducibility, ruggedness (no -moving-parts operation) and flexibility, make it particularly desirable for numerous applications. A series of prototype (research model) acousto -optic tunable filter instruments were developed and tested in order to investigate the feasibility of the technology for quantitative near-IR spectrometry. Development included design, component procurement, assembly and/or configuration of the optical and electronic subsystems of which each functional spectrometer arrangement was comprised, as well as computer interfacing and acquisition/control software development. Investigation of this technology involved an evolution of several operational spectrometer systems, each of which offered improvements over its predecessor. Appropriate testing was conducted at various stages of development. Demonstrations of the potential applicability of our AOTF spectrometer to quantitative process monitoring or laboratory analysis of numerous organic substances, including food materials, were

  12. Narrow-band UVB radiation promotes dendrite formation by activating Rac1 in B16 melanoma cells.

    PubMed

    Wang, Wu-Qing; Wu, Jin-Feng; Xiao, Xiao-Qing; Xiao, Qin; Wang, Jing; Zuo, Fu-Guo

    2013-09-01

    Melanocytes are found scattered throughout the basal layer of the epidermis. Following hormone or ultraviolet (UV) light stimulation, the melanin pigments contained in melanocytes are transferred through the dendrites to the surrounding keratinocytes to protect against UV light damage or carcinogenesis. This has been considered as a morphological indicator of melanocytes and melanoma cells. Small GTPases of the Rho family have been implicated in the regulation of actin reorganization underlying dendrite formation in melanocytes and melanoma cells. It has been proven that ultraviolet light plays a pivotal role in melanocyte dendrite formation; however, the molecular mechanism underlying this process has not been fully elucidated. The effect of small GTPases, such as Rac1 and RhoA, on the morphology of B16 melanoma cells treated with narrow-band UVB radiation was investigated. The morphological changes were observed under a phase contrast microscope and the F-actin microfilament of the cytoskeleton was observed under a laser scanning confocal microscope. The pull-down assay was performed to detect the activity of the small GTPases Rac1 and RhoA. The morphological changes were evident, with globular cell bodies and increased numbers of tree branch-like dendrites. The cytoskeletal F-actin appeared disassembled following narrow-band UVB irradiation of B16 melanoma cells. Treatment of B16 melanoma cells with narrow-band UVB radiation resulted in the activation of Rac1 in a time-dependent manner. In conclusion, the present study may provide a novel method through which narrow-band UVB radiation may be used to promote dendrite formation by activating the Rac1 signaling pathway, resulting in F-actin rearrangement in B16 melanoma cells. PMID:24649261

  13. AVHRR Surface Temperature and Narrow-Band Albedo Comparison with Ground Measurements for the Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Haefliger, M.; Steffen, K.; Fowler, C.

    1993-01-01

    An ice-surface temperature retrieval algorithm for the Greenland ice sheet was developed using NOAA 11 thermal radiances from channels 4 and 5. Temperature, pressure and humidity profiles, cloud observations and skin temperatures from the Swiss Federal Institute of Technology (ETH) camp, located at the equilibrium line altitude at 49 deg17 min W, 69 deg 34 min N, were used in the LOWTRAN 7 model. Through a statistical analysis of daily clear sky profiles, the coefficients that correct for the atmospheric effects were determined for the ETH-Camp field season (May to August). Surface temperatures retrieved by this method were then compared against the in situ observations with a maximum difference of 0.6 K. The NOAA 11 narrow-band planetary albedo values for channels 1 and 2 were calculated using pre-launch calibration coefficients. Scattering and absorption by the atmosphere were modelled with LOWTRAN 7. Then, narrow-band albedo values for the AVHRR visible and near infrared channels were compared with in situ high resolution spectral reflectance measurements. In the visible band (580-680 nm), AVHRR-derived narrow-band albedo and the in situ measurements corrected with radiative transfer model LOWTRAN 7 showed a difference of less than 2%. For the near infrared channel (725-1100 nm) the difference between the measured and modelled narrow-band albedo was 14%. These discrepancies could be either the result of inaccurate aerosol scattering modelling (lack of the in situ observation), or the result of sensor drift due to degradation.

  14. Intensity Variations of Narrow Bands of Solar UV Radiation during Descending Phases of SACs 21-23

    NASA Astrophysics Data System (ADS)

    Gigolashvili, M.; Kapanadze, N.

    2014-12-01

    The study of variations of four narrow bands of solar spectral irradiance (SSI) in the ultraviolet (UV) range for period 1981-2008 is presented. Observational data obtained by space-flight missions SORCE, UARS, SME and daily meanings of international sunspot number (ISN) have been used. The investigated data cover the decreasing phases of the solar activity cycles (SACs) 21, 22 and 23. We have revealed a peculiar behavior of intensity variability of some solar ultraviolet spectral lines originated in the solar chromospheres for period corresponding to the declining phase of the solar cycle 23. It is found that variability of emission of different solar spectral narrow bands (289.5 nm, 300.5 nm) does not agree equally well with ISN variability during decreasing phase of the solar activity cycle 23. The negative correlations between total solar irradiance and the solar spectral narrow bands of UV emission (298.5 nm, 300.5 nm) had been revealed. The existence of the negative correlation can be explained by the sensitivity of SSI of some emission lines to the solar global magnetic field.

  15. LIGHT MODULATION: Quasi-collinear tunable acousto-optic paratellurite crystal filters for wavelength division multiplexing and optical channel selection

    NASA Astrophysics Data System (ADS)

    Molchanov, V. Ya; Voloshinov, V. B.; Makarov, O. Yu

    2009-04-01

    Quasi-collinear acousto-optic interaction is studied in acoustically and optically anisotropic paratellurite crystals. The possible applications of this interaction in acousto-optic tunable filters with a high spectral resolution are discussed. Different modifications of devices are compared and variants of devices intended for processing light beams and selection of light signals in fibreoptic communication systems with wavelength division multiplexing (WDM) at λ simeq 1550 nm are considered.

  16. Tunable fiber ring laser with an intracavity high resolution filter employing two-dimensional dispersion and LCoS modulator.

    PubMed

    Sinefeld, David; Marom, Dan M

    2012-01-01

    We demonstrate a tunable fiber ring laser employing a two-dimensional dispersion arrangement filter, with the lasing determined by a liquid crystal on silicon (LCoS) spatial light modulator. Lasing wavelengths can be tuned discontinuously across the communication C-band at an addressable resolution of less than 200 MHz. We introduce full characterization of the laser output including phase and amplitude stability and short and long-term bandwidth measurements. PMID:22212771

  17. Quasi-collinear tunable acousto-optic paratellurite crystal filters for wavelength division multiplexing and optical channel selection

    SciTech Connect

    Molchanov, V Ya; Makarov, O Yu; Voloshinov, V B

    2009-04-30

    Quasi-collinear acousto-optic interaction is studied in acoustically and optically anisotropic paratellurite crystals. The possible applications of this interaction in acousto-optic tunable filters with a high spectral resolution are discussed. Different modifications of devices are compared and variants of devices intended for processing light beams and selection of light signals in fibreoptic communication systems with wavelength division multiplexing (WDM) at {lambda} {approx_equal} 1550 nm are considered. (light modulation)

  18. Demonstration of multi-wavelength tunable fiber lasers based on a digital micromirror device processor.

    PubMed

    Ai, Qi; Chen, Xiao; Tian, Miao; Yan, Bin-bin; Zhang, Ying; Song, Fei-jun; Chen, Gen-xiang; Sang, Xin-zhu; Wang, Yi-quan; Xiao, Feng; Alameh, Kamal

    2015-02-01

    Based on a digital micromirror device (DMD) processor as the multi-wavelength narrow-band tunable filter, we demonstrate a multi-port tunable fiber laser through experiments. The key property of this laser is that any lasing wavelength channel from any arbitrary output port can be switched independently over the whole C-band, which is only driven by single DMD chip flexibly. All outputs display an excellent tuning capacity and high consistency in the whole C-band with a 0.02 nm linewidth, 0.055 nm wavelength tuning step, and side-mode suppression ratio greater than 60 dB. Due to the automatic power control and polarization design, the power uniformity of output lasers is less than 0.008 dB and the wavelength fluctuation is below 0.02 nm within 2 h at room temperature. PMID:25967765

  19. A SOA-based high Q microwave photonic filter

    NASA Astrophysics Data System (ADS)

    Xu, Enming; Li, Lipei; Wang, Fei; Yu, Yuan; Li, Xiang; Zhang, Xinliang; Huang, Dexiu

    2011-01-01

    We propose and experimentally demonstrate a novel all-optical microwave filter with high quality factor (Q). It is based on a recirculating delay line (RDL) loop in which a semiconductor optical amplifier (SOA) is followed by a tunable narrow-band optical filter and a 1x2 10:90 optical coupler. Converted signal used as a negative tap is generated through wavelength conversion employing the cross-gain modulation (XGM) of the amplified spontaneous emission (ASE) spectrum of the SOA. The converted signal can circulate in the RDL loop so that the proposed filter realizes a high Q factor response after photo-detection. The 1x2 10:90 coupler is employed to extract 10% optical power from the loop as output. A frequency response with a high Q factor of 543, a rejection ratio of 40 dB is experimentally demonstrated.

  20. A SOA-based high Q microwave photonic filter

    NASA Astrophysics Data System (ADS)

    Xu, Enming; Li, Lipei; Wang, Fei; Yu, Yuan; Li, Xiang; Zhang, Xinliang; Huang, Dexiu

    2010-12-01

    We propose and experimentally demonstrate a novel all-optical microwave filter with high quality factor (Q). It is based on a recirculating delay line (RDL) loop in which a semiconductor optical amplifier (SOA) is followed by a tunable narrow-band optical filter and a 1x2 10:90 optical coupler. Converted signal used as a negative tap is generated through wavelength conversion employing the cross-gain modulation (XGM) of the amplified spontaneous emission (ASE) spectrum of the SOA. The converted signal can circulate in the RDL loop so that the proposed filter realizes a high Q factor response after photo-detection. The 1x2 10:90 coupler is employed to extract 10% optical power from the loop as output. A frequency response with a high Q factor of 543, a rejection ratio of 40 dB is experimentally demonstrated.

  1. Dual-wavelength erbium-doped fiber laser with tunable wavelength spacing using a twin core fiber-based filter

    NASA Astrophysics Data System (ADS)

    Yin, Guolu; Lou, Shuqin; Wang, Xin; Han, Bolin

    2014-05-01

    A dual-wavelength erbium-doped fiber laser with tunable wavelength spacing was proposed and experimentally demonstrated by using a twin core fiber (TCF)-based filter. Benefiting from the polarization dependence of the TCF-based filter, the laser operated in dual-wavelength oscillation with two orthogonal polarization states. By adjusting the polarization controller, the wavelength spacing was tuned from 0.1 nm to 1.2 nm without shifting the centre position of the two wavelengths. By stretching the TCF, the two wavelengths were simultaneously tuned with fixed wavelength spacing. Such a dual-wavelength fiber laser could find applications in optical fiber sensors and microwave photonics generation.

  2. Electrically tunable spin filtering for electron tunneling between spin-resolved quantum Hall edge states and a quantum dot

    SciTech Connect

    Kiyama, H. Fujita, T.; Teraoka, S.; Oiwa, A.; Tarucha, S.

    2014-06-30

    Spin filtering with electrically tunable efficiency is achieved for electron tunneling between a quantum dot and spin-resolved quantum Hall edge states by locally gating the two-dimensional electron gas (2DEG) leads near the tunnel junction to the dot. The local gating can change the potential gradient in the 2DEG and consequently the edge state separation. We use this technique to electrically control the ratio of the dot–edge state tunnel coupling between opposite spins and finally increase spin filtering efficiency up to 91%, the highest ever reported, by optimizing the local gating.

  3. Note: Broadly tunable all-fiber ytterbium laser with 0.05 nm spectral width based on multimode interference filter

    SciTech Connect

    Mukhopadhyay, Pranab K. Gupta, Pradeep K.; Singh, Amarjeet; Sharma, Sunil K.; Bindra, Kushvinder S.; Oak, Shrikant M.

    2014-05-15

    A multimode interference filter with narrow transmission bandwidth and large self-imaging wavelength interval is constructed and implemented in an ytterbium doped fiber laser in all-fiber format for broad wavelength tunability as well as narrow spectral width of the output beam. The peak transmission wavelength of the multimode interference filter was tuned with the help of a standard in-fiber polarization controller. With this simple mechanism more than 30 nm (1038 nm–1070 nm) tuning range is demonstrated. The spectral width of the output beam from the laser was measured to be 0.05 nm.

  4. An acousto-optic tunable filter enhanced CO{sub 2} lidar atmospheric monitor

    SciTech Connect

    Taylor, L.H.; Suhre, D.R.; Mani, S.S.

    1996-12-31

    The atmospheric monitor conceptual design is based on a pulsed CO{sub 2} laser. The narrow laser lines provide high spectral selectivity in the 9-11 {mu}m region, within the 8-14 {mu}m ``fingerprint`` region where most large molecules have unique spectral absorption signatures. Laser power has been chosen so that topological objects, e.g., trees or buildings, as far as 4 km can be used as backreflectors, but the laser intensity is sufficiently low that the laser beam is eye-safe. Time-of-flight measurements give the distance to the topological reflector. The lidar system is augmented with an acousto-optic tunable filter (AOTF) which measures the thermal emission spectra from 3 to 14 {mu}m with a 3 cm{sup -1} passband. Sensitivity to narrow emission lines is enhanced by derivative spectroscopy in which the passband of the AOTF is dithered via the rf drive. Path-averaged concentrations are determined from the emission intensity and laser- determined range.

  5. Radiometric calibration and noise estimation of acousto-optic tunable filter hyperspectral imaging systems.

    PubMed

    Katrašnik, Jaka; Pernuš, Franjo; Likar, Boštjan

    2013-05-20

    The accuracy of the radiometric response of acousto-optic tunable filter (AOTF) hyperspectral imaging systems is crucial for obtaining reliable measurements. It is therefore important to know the radiometric response and noise characteristics of the hyperspectral imaging system used. A radiometric model of an AOTF hyperspectral imaging system composed of an imaging sensor radiometric model (CCD, CMOS, and sCMOS) and an AOTF light transmission model is proposed. Using the radiometric model, a method for obtaining the fixed pattern noise (FPN) of the imaging system by displacing and imaging an illuminated reference target is developed. Methods for estimating the temporal noise of the imaging system, using the photon transfer method, and for correcting FPN are also presented. Noise estimation and image restoration methods were tested on an AOTF hyperspectral imaging system. The results indicate that the developed methods can accurately calculate temporal and FPN, and can effectively correct the acquired images. After correction, the signal-to-noise ratio of the acquired images was shown to increase by 26%. PMID:23736239

  6. Electro-Mechanical Simulation of a Large Aperture MOEMS Fabry-Perot Tunable Filter

    NASA Technical Reports Server (NTRS)

    Kuhn, Jonathan L.; Barclay, Richard B.; Greenhouse, Matthew A.; Mott, D. Brent; Satyapal, Shobita; Powers, Edward I. (Technical Monitor)

    2000-01-01

    We are developing a micro-machined electrostatically actuated Fabry-Perot tunable filter with a large clear aperture for application in high through-put wide-field imaging spectroscopy and lidar systems. In the first phase of this effort, we are developing key components based on coupled electro-mechanical simulations. In particular, the movable etalon plate design leverages high coating stresses to yield a flat surface in drum-head tension over a large diameter (12.5 mm). In this approach, the cylindrical silicon movable plate is back etched, resulting in an optically coated membrane that is suspended from a thick silicon support ring. Understanding the interaction between the support ring, suspended membrane, and coating is critical to developing surfaces that are flat to within stringent etalon requirements. In this work, we present the simulations used to develop the movable plate, spring suspension system, and electrostatic actuation mechanism. We also present results from tests of fabricated proof of concept components.

  7. A liquid-crystal-tunable-filter-based multispectral imaging system for prediction of apple fruit firmness

    NASA Astrophysics Data System (ADS)

    Peng, Yankun; Lu, Renfu

    2004-11-01

    Firmness of apple fruit is an important quality attribute, which varies greatly in the same lot of fruit due to such factors as climatic condition, cultural practice, harvest time or maturity level, and postharvest handling and storage. This research developed a compact multispectral imaging system with a low cost digital camera and a liquid crystal tunable filter (LCTF), and proposed a modified Lorentzian distribution (MLD) function to describe scattering profiles acquired from Red Delicious apples. The LCTF, which allows for the rapid, vibration-less selection of any wavelength in the visible/near-infrared range, was used to find optimal wavelengths over the spectral region between 650 nm and 1,000 nm for predicting apple fruit firmness. Radial scattering profiles were described accurately by the MLD function with four profile parameters for wavelengths between 650 nm and 1000 nm at an interval of 10 nm. Multi-linear regression (MLR) and cross-validation were performed on relating MLD parameters to fruit firmness. The prediction model gave good firmness predictions with the correlation coefficient (r) of 0.82 and the standard error of validation (SEV) of 6.64 N, which were considerably better than those obtained with visible/near-infrared spectroscopy.

  8. Investigation of liquid crystal Fabry-Perot tunable filters: design, fabrication, and polarization independence.

    PubMed

    Isaacs, Sivan; Placido, Frank; Abdulhalim, Ibrahim

    2014-10-10

    Liquid crystal Fabry-Perot tunable filters are investigated in detail, with special attention to their manufacturability, design, tolerances, and polarization independence. The calculations were performed both numerically and analytically using the 4×4 propagation matrix method. A simplified analytic expression for the propagation matrix is derived for the case of nematic LC in the homogeneous geometry. At normal incidence, it is shown that one can use the 2×2 Abeles matrix method; however, at oblique incidence, the 4×4 matrix method is needed. The effects of dephasing originating from wedge or noncollimated light beams are investigated. Due to the absorption of the indium tin oxide layer and as an electrode, its location within the mirror multilayered stack is very important. The optimum location is found to be within the stack and not on its top or bottom. Finally, we give more detailed experimental results of our polarization-independent configuration that uses polarization diversity with a Wollaston prism. PMID:25322437

  9. Hyperspectral imaging with liquid-crystal tunable filter for biological and agricultural assessment

    NASA Astrophysics Data System (ADS)

    Mao, Chengye; Heitschmidt, Jerry

    1999-01-01

    A hyperspectral imaging system has been developed to provide the capability of both airborne and ground/laboratory data acquisitions. The system consists of modular front imaging optics with a liquid crystal tunable filter (LCTF), a CCD video camera, a frame grabber and a portable computer system. The spectral range is form 450 nm to 750 nm with a 10 nm bandpass for each band acquired. The system can capture different spectral images at a rate up to 14 images per second. Hyperspectral imaging with an LCTF provides a new method for hyperspectral image acquisition. The system allows the user to define a wavelength sequence of up to thirty-two spectrums specifically required for individual application, and can quickly switch from the current wavelength to the next during automated image acquisition. Hyperspectral images of crop fields, vegetation, fruits, and meat were successfully captured during laboratory experiments and airborne image acquisition. The constructed spectral image cube not only shows the spatial features of the target, but also reveals the individual pixels with unique spectral signatures. The imaging system with LCTF is, therefore, very useful in biological and agricultural assessment for detecting variations in crop fields, or defects in samples and products.

  10. Double tungsten coil atomic absorption spectrometer based on an acousto-optic tunable filter

    NASA Astrophysics Data System (ADS)

    Jora, M. Z.; Nóbrega, J. A.; Rohwedder, J. J. R.; Pasquini, C.

    2015-01-01

    An atomic absorption spectrometer based on a quartz acousto-optic tunable filter (AOTF) monochromator operating in the 271-453 nm range, is described. The instrument was tailored to study the formation and evolution of electrothermal atomic cloud induced either by one or two tungsten coils. The spectrometer also includes a fast response programmable photomultiplier module for data acquisition, and a power supply capable of driving two parallel tungsten coils independently. The atomization cell herein described was manufactured in PTFE and presents a new design with reduced size. Synchronization between the instant of power delivering to start the atomization process and the detection was achieved, allowing for monitoring the atomization and thermal events synchronously and in real time. Absorption signals can be sampled at a rate of a few milliseconds, compatible with the fast phenomena that occur with electrothermal metallic atomizers. The instrument performance was preliminarily evaluated by monitoring the absorption of radiation of atomic clouds produced by standard solutions containing chromium or lead. Its quantitative performance was evaluated by using Cr aqueous solutions, resulting in detection limits as low as 0.24 μg L- 1, and a relative standard deviation of 3%.

  11. Idler-free microwave photonic mixer integrated with a widely tunable and highly selective microwave photonic filter.

    PubMed

    Zou, Dan; Zheng, Xiaoping; Li, Shangyuan; Zhang, Hanyi; Zhou, Bingkun

    2014-07-01

    A novel structure consisting of an idler-free microwave photonic mixer integrated with a widely tunable and highly selective microwave photonic filter is presented, which is comprised of a spectrum-sliced broadband optical source, a dual-parallel Mach-Zehnder modulator (DPMZM), and a spatial light amplitude and phase processor (SLAPP). By adjusting the optical phase shift in the DPMZM, the dispersion-induced mixing power fading can be eliminated. By applying a phase processor with the SLAPP, the distortion of the mixing filter brought upon by third-order dispersion is also compensated. Experiments are performed and show that the up/down-conversion signal has a clean spectrum and the mixing filter can be tuned from 12 to 20 GHz without any change to the passband shape. The out-of-band suppression ratio of the mixing filter is more than 40 dB, and the 3 dB bandwidth is 140 MHz. PMID:24978780

  12. Leaf Level Chlorophyll Fluorescence Emission Spectra: Narrow Band versus Full 650-800 nm Retrievals

    NASA Astrophysics Data System (ADS)

    Middleton, E.; Zhang, Q.; Campbell, P. K.; Huemmrich, K. F.; Corp, L.; Cheng, Y.

    2012-12-01

    nm (r2 = 0.88, RMSE = 7.54 x 107). When perfect retrievals were assumed (0% noise), retrievals remained good in the low emission regions on either side of the peaks-- those associated with the H alpha line at 655 nm (r2 = 0.83, RMSE =8.87 x 107) and the far-NIR wavelengths recently utilized for satellite retrievals: a K line at 770 nm (r2 = 0.85, RMSE = 8.36 x 107) and the 750-770 nm interval (r2 = 0.88, RMSE = 6.92 x 107). However, the atmosphere and satellite observations are expected to add noise to retrievals. Adding 5% random error to these relationships did not seriously impair the retrieval successes in the red and far-red peaks (r2 ~ 0.85, RMSEs = 6.31 x 107). A greater impact occurred (reducing retrieval success by ~10%) when adding 5% noise for the far-NIR narrow band at 770 nm (r2 ~ 0.70, RMSE ~ 8.5 x 107). When a 10% random error was added, the retrieval successes fell to ~68 ± 7% for all retrieval wavebands, and RMSEs increased by a factor of 10. This laboratory approach will be critical to calibrate space borne retrievals, but additional information across plant species is needed. Furthermore, this experiment indicates that ChlF retrievals from space should include information from the red and far-red peak emission regions, since the true total fluorescence signal is the desired parameter for Earth carbon and energy budgets.

  13. Diagnosis of gastric intraepithelial neoplasia by narrow-band imaging and confocal laser endomicroscopy

    PubMed Central

    Wang, Shu-Fang; Yang, Yun-Sheng; Wei, Li-Xin; Lu, Zhong-Sheng; Guo, Ming-Zhou; Huang, Jin; Peng, Li-Hua; Sun, Gang; Ling-Hu, En-Qiang; Meng, Jiang-Yun

    2012-01-01

    AIM: To evaluate the diagnosis of different differentiated gastric intraepithelial neoplasia (IN) by magnification endoscopy combined with narrow-band imaging (ME-NBI) and confocal laser endomicroscopy (CLE). METHODS: Eligible patients with suspected gastric IN lesions previously diagnosed by endoscopy in secondary hospitals and scheduled for further diagnosis and treatment were recruited for this study. Excluded from the study were patients who had liver cirrhosis, impaired renal function, acute gastrointestinal (GI) bleeding, coagulopathy, esophageal varices, jaundice, and GI post-surgery. Also excluded were those who were pregnant, breastfeeding, were younger than 18 years old, or were unable to provide informed consent. All patients had all mucus and bile cleared from their stomachs. They then received upper GI endoscopy. When a mucosal lesion is found during observation with white-light imaging, the lesion is visualized using maximal magnification, employing gradual movement of the tip of the endoscope to bring the image into focus. Saved images are analyzed. Confocal images were evaluated by two endoscopists (Huang J and Li MY), who were familiar with CLE, blinded to the related information about the lesions, and asked to classify each lesion as either a low grade dysplasia (LGD) or high grade dysplasia (HGD) according to given criteria. The results were compared with the final histopathologic diagnosis. ME-NBI images were evaluated by two endoscopists (Lu ZS and Ling-Hu EQ) who were familiar with NBI, blinded to the related information about the lesions and CLE images, and were asked to classify each lesion as a LGD or HGD according to the “microvascular pattern and surface pattern” classification system. The results were compared with the final histopathologic diagnosis. RESULTS: The study included 32 pathology-proven low grade gastric IN and 26 pathology-proven high grade gastric IN that were detected with any of the modalities. CLE and ME-NBI enabled

  14. A Bio-Realistic Analog CMOS Cochlea Filter With High Tunability and Ultra-Steep Roll-Off.

    PubMed

    Wang, Shiwei; Koickal, Thomas Jacob; Hamilton, Alister; Cheung, Rebecca; Smith, Leslie S

    2015-06-01

    This paper presents the design and experimental results of a cochlea filter in analog very large scale integration (VLSI) which highly resembles physiologically measured response of the mammalian cochlea. The filter consists of three specialized sub-filter stages which respectively provide passive response in low frequencies, actively tunable response in mid-band frequencies and ultra-steep roll-off at transition frequencies from pass-band to stop-band. The sub-filters are implemented in balanced ladder topology using floating active inductors. Measured results from the fabricated chip show that wide range of mid-band tuning including gain tuning of over 20 dB, Q factor tuning from 2 to 19 as well as the bio-realistic center frequency shift are achieved by adjusting only one circuit parameter. Besides, the filter has an ultra-steep roll-off reaching over 300 dB/dec. By changing biasing currents, the filter can be configured to operate with center frequencies from 31 Hz to 8 kHz. The filter is 9th order, consumes 59.5 ∼ 90.0 μW power and occupies 0.9 mm2 chip area. A parallel bank of the proposed filter can be used as the front-end in hearing prosthesis devices, speech processors as well as other bio-inspired auditory systems owing to its bio-realistic behavior, low power consumption and small size. PMID:25099631

  15. The Luminosity Function and Star Formation Rate Between Redshifts of 0.07 and 1.47 for Narrow-band Emitters in the Subaru Deep Field

    NASA Astrophysics Data System (ADS)

    Ly, Chun; Malkan, M.; Kashikawa, N.; Shimasaku, K.; Doi, M.; Nagao, T.; Iye, M.; Kodama, T.; Morokuma, T.; Motohara, K.

    2006-06-01

    Subaru Deep Field line-emitting galaxies in four narrow-band filters at low and intermediate redshifts are presented. Broad-band colors, follow-up optical spectroscopy, and multiple narrow-band filters are used to distinguish Hα, [OII], and [OIII] emitters between redshifts of 0.07 and 1.47 to construct their averaged rest-frame optical-to-UV SED and luminosity functions. These luminosity functions are derived down to faint magnitudes, which allows for a more accurate determination of the faint end slope. With a large (N 200-900) sample for each redshift interval, a Schechter profile is fitted to each luminosity function. Prior to dust extinction corrections, the [OIII] and [OII] luminosity functions reported in this paper agree reasonably well with those of Hippelein et al (2003). The z=0.066-0.092 Hα LF agrees with those of Jones & Bland-Hawthorn (2001), but for z=0.24 and 0.40, their number density is higher by a factor of two or more. The z=0.08 Hα LF, which reaches two orders of magnitude fainter than Gallego et al. (1995), is steeper by 25%. This indicates that there are more low luminosity star-forming galaxies for z<0.1 than predicted. The faint end slope α and φ* show a strong evolution with redshift while L* show little evolution. The evolution in α indicates that low-luminosity galaxies have a stronger evolution compared to brighter ones. Integrated star formation rate densities are derived via Hα for 0.07

  16. High Voltage Ramp Generator for Electro-Optically Tunable Filter for the MSE-CIF Diagnostics on NSTX.

    NASA Astrophysics Data System (ADS)

    Wu, Ying; Levinton, Fred

    2004-11-01

    The motional Stark effect (MSE) diagnostic is routinely used to determine the q-profile in large fusion devices. To apply the MSE diagnostic to experiments with low magnetic fields such as NSTX (<1 T), a tunable birefringent Lyot filter is used with high throughput and high resolution which allows for a good signal-to-noise ratio. The birefringent filter is made from lithium-niobate crystals, which are coated with a layer of indium tin-oxide (ITO). The ITO layer is a transparent conductive coating. By applying an electric field across the crystal the index of refraction is varied. This allows tunability of the filter. Putting multiple crystals together and tuning them individually it is possible to pass certain wavelengths of light and reject others. A high voltage ramp generator circuit is under development to ramp a 5 kV signal using a simple design involving MOSFET ladders. The goal is to design the circuit so that it can ramp ±5000 volts at a frequency of around 1 kHz. This would allow the filter to sweep over a range of ˜ 1nm.

  17. A continuously tunable multi-tap complex-coefficient microwave photonic filter based on a tilted fiber Bragg grating.

    PubMed

    Shahoei, Hiva; Yao, Jianping

    2013-03-25

    The coupling coefficients of the cladding-mode resonances of a tilted fiber Bragg grating (TFBG) are linearly increasing or decreasing in different wavelength regions. Based on the Kramers-Kronig relations, when the coupling coefficients are linearly increasing, the phase shifts are linearly increasing correspondingly. This feature is employed, for the first time, for the implementation of a multi-tap continuously tunable microwave photonic filter with complex coefficients by using a TFBG. By locating the optical carriers of single-sideband-modulated signals at the cladding-mode resonances of the TFBG which has linearly increasing depths, linearly increasing phase shifts are introduced to the optical carriers. By beating the optical carriers with the single sidebands, the phase shifts are translated to the microwave signals, and thus complex coefficients with the required linearly increasing phase shifts are generated. The tunability of the complex coefficients is realized by optically pumping the TFBG which is written in an erbium/ytterbium (Er/Yb) co-doped fiber. A proof-of-concept experiment is performed; a three- and four-tap filter with a frequency tunable range of 150 and 120 MHz, respectively, are demonstrated. PMID:23546134

  18. Dual cut-off direct current-tunable microwave low-pass filter on superconducting Nb microstrips with asymmetric nanogrooves

    NASA Astrophysics Data System (ADS)

    Dobrovolskiy, Oleksandr V.; Huth, Michael

    2015-04-01

    We present a dual cut-off, dc-tunable low-pass microwave filter on a superconducting Nb microstrip with uniaxial asymmetric nanogrooves. The frequency response of the device was measured in the range 300 KHz-14 GHz at different temperatures, magnetic fields, and dc values. The microwave loss is most effectively reduced when the Abrikosov vortex lattice spatially matches the underlying washboard pinning landscape. The forward transmission coefficient S21(f) of the microstrip has a dc-tunable cut-off frequency fd which notably changes under dc bias reversal, due to the two different slope steepnesses of the pinning landscape. The device's operation principle relies upon a crossover from the weakly dissipative response of vortices at low frequencies when they are driven over the grooves, to the strongly dissipative response at high frequencies when the vortices are oscillating within one groove. The filter's cut-off frequency is the vortex depinning frequency tunable by the dc bias as it diminishes the pinning effect induced by the nanopattern. The reported results unveil an advanced microwave functionality of superconducting films with asymmetric (ratchet) pinning landscapes and are relevant for tuning the microwave loss in superconducting planar transmission lines.

  19. A novel acousto-optic tunable filter for use in hyperspectral imaging systems

    NASA Astrophysics Data System (ADS)

    Stedham, C.; Draper, M.; Ward, J.; Wachman, E.; Pannell, C.

    2008-02-01

    The design and performance characteristics of a novel Acousto Optic Tunable Filter (AOTF) are presented. Particular attention has been paid to the reduction of optical side lobes, maximising the light throughput and achieving efficient wideband RF matching of a device for use in hyperspectral imaging systems. Conventional AOTFs are known to yield an optical pass band with side lobes at unacceptable levels of ~-10dB relative to the transmission peak. It is known that shaping the acoustic beam ("apodisation") can suppress the side lobe transmission of the AOTF and improve its imaging capabilities. Results of a novel electrode apodisation pattern are presented, reducing sidelobes to ~-25dB. This produces an AOTF which is capable of being placed in a diffraction limited optical system and introduces negligible amounts of image degradation. The large transducer area (associated with the large optical aperture) and acoustic impedance mismatch between the AO substrate (TeO II) and transducer (LiNbO 3) pose a challenge in achieving wideband RF performance. Acoustic mismatch between substrate and transducer has been addressed by the introduction of a special acoustic matching layer in the bond. The layer reduces dispersion in the transducer impedance easing broadband matching. The transducer has a low (<1 Ohm) radiation resistance which must be matched to the RF driver (typically 50 ohms). This very low impedance may be swamped by the parasitic impedances of the electrode, bond layers and wire bonds used for electrical connection. Thus, the transducer is split into series-connected sections to increase the "bare" impedance. We present results to show the performance increase that can be obtained this way.

  20. Tunable filter comparator for spectral calibration of near-ambient temperature blackbodies

    NASA Astrophysics Data System (ADS)

    Khromchenko, V. B.; Mekhontsev, S. N.; Hanssen, L. M.

    2007-09-01

    The calibration of infrared (IR) radiometers, thermal imagers and electro-optical systems relies on use of extended area blackbodies (BB) operating in the ambient environment. "Flat plate" designs, typically using a thermoelectric heat pump backed with an air- or liquid-cooled radiator, allow one to adequately meet the requirements of geometrical size and temperature span. The tradeoff comes in the form of limited temperature uniformity and lower emissivity that such an approach can provide given the limitations in achievable thermal conductivity of the plate and reflectance of the black paint, respectively. The availability of spectrally resolved radiance temperature data for infrared calibrators has become especially vital in the last few years with the widespread use of multi- and hyper-spectral electro-optical systems that enable better detection and identification of targets. In an effort to increase the measurement accuracy of IR spectral radiance of near-ambient BB calibrators, NIST has recently built a dedicated capability which is a part of its new AIRI (Advanced Infrared Radiometry and Imaging) facility. The Tunable Filter Comparator (TFC) is a key new element in this setup, allowing us to perform a precise comparison of the unit under test (UUT) with two reference blackbodies of known temperatures and emissivity. The report describes the major design features of the TFC comparator, the algorithm used for signal processing, and results of a performance evaluation of the TFC. The TFC development has enabled us to achieve BB radiance temperature comparisons with a standard deviation of 5 to 15 mK at temperatures of 15-150 C across the 3 to 5 µm and 8 to 12 µm atmospheric band ranges with a relative spectral resolution of 2 to 3%.

  1. Spacecraft Doppler Tracking as a Narrow-Band Detector of Gravitational Radiation

    NASA Technical Reports Server (NTRS)

    Tinto, M.; Armstrong, J. W.

    1998-01-01

    We discuss a filtering technique for reducing the frequency fluctuations due to the troposphere, ionosphere, and mechanical vibrations of the ground antenna in spacecraft Doppler tracking searches for gravitational radiation. This method takes advantage of the sinusoidal behavior of the transfer function to the Doppler observable of these noise sources, which displays sharp nulls at selected Fourier components.

  2. Tunable all-optical single-bandpass photonic microwave filter based on spectrally sliced broad optical source and phase modulation.

    PubMed

    Chen, Ming; Pan, Wei; Zou, Xihua; Luo, Bin; Yan, Lianshan; Liu, Xinkai

    2013-01-10

    A tunable all-optical single-bandpass photonic microwave filter (PMF) based on spectrally sliced broadband optical source and phase modulation is proposed and experimentally demonstrated. A broadband optical source and a Mach-Zehnder interferometer (MZI) are used to generate continuous optical spectral samples, which are employed to form a finite impulse response filter with a single-bandpass response with the help of a single-mode fiber. A phase modulator is then adopted to eliminate the baseband components in the filtering response. The center frequency of the PMF can be tuned by changing the free spectral range of the MZI. An experiment is performed, and the results demonstrate that the proposed PMF has a single-bandpass without baseband components and a tuning range of 5-15 GHz. PMID:23314649

  3. Tunable channel-drop filters consisting of polymeric Bragg reflectors and a mode sorting asymmetric X-junction.

    PubMed

    Shin, Jin-Soo; Park, Tea-Hyun; Chu, Woo-Sung; Lee, Chang-Hee; Shin, Sang-Yung; Oh, Min-Cheol

    2015-06-29

    A tunable channel-drop filter as essential component for the wavelength-division-multiplexing optical communication system has been demonstrated, which is based on polymer waveguide Bragg reflectors. For an ordinary Bragg reflector, the filtered signal is reflected toward the input waveguide. Thus an external circulator is required to separate the filtered signal from the input port, though it increases the total footprint and cost. For this purpose, we employed dual Bragg reflectors and a mode sorting asymmetric X-junction. The Bragg reflector exhibited a maximum reflectivity of 94% for a 6-mm long grating, a 3-dB bandwidth of 0.39 nm and a 20-dB bandwidth of 2.6 nm. The mode sorting crosstalk in asymmetric X-junction was less than -20 dB, and linear wavelength tuning was achieved over 10 nm at the applied thermal power of 377 mW. PMID:26191731

  4. Tunable Fabry-Perot filter in cobalt doped fiber formed by optically heated fiber Bragg gratings pair

    NASA Astrophysics Data System (ADS)

    Li, Ying; Zhou, Bin; Zhang, Liang; He, Sailing

    2015-06-01

    In this paper, a tunable fiber Fabry-Perot (F-P) filter by all-optical heating is proposed. Two high reflective fiber Bragg gratings (FBG) fabricated in cobalt doped single mode fiber form the F-P cavity. The cobalt-doped fiber used here is an active fiber, and it transforms optical power from a control laser into heat effectively due to the nonradiative processes. The generated heat raises the refraction index of the fiber and enlarges the F-P cavity's length, realizing the all-optical tuning characteristics. By adjusting the power of the control laser, the resonant wavelength of our proposed fiber F-P filter can be high precisely controlled. The cavity length of the filter is carefully designed to make sure the longitude mode spacing is comparable to the grating bandwidth, making it single mode operating.

  5. High resolution observations with Artemis-IV and the NRH. I. Type IV associated narrow-band bursts

    NASA Astrophysics Data System (ADS)

    Bouratzis, C.; Hillaris, A.; Alissandrakis, C. E.; Preka-Papadema, P.; Moussas, X.; Caroubalos, C.; Tsitsipis, P.; Kontogeorgos, A.

    2016-02-01

    Context. Narrow-band bursts appear on dynamic spectra from microwave to decametric frequencies as fine structures with very small duration and bandwidth. They are believed to be manifestations of small scale energy release through magnetic reconnection. Aims: We analyzed 27 metric type IV events with embedded narrow-band bursts, which were observed by the ARTEMIS-IV radio spectrograph from 30 June 1999 to 1 August 2010. We examined the morphological characteristics of isolated narrow-band structures (mostly spikes) and groups or chains of structures. Methods: The events were recorded with the SAO high resolution (10 ms cadence) receiver of ARTEMIS-IV in the 270-450 MHz range. We measured the duration, spectral width, and frequency drift of ~12 000 individual narrow-band bursts, groups, and chains. Spike sources were imaged with the Nançay radioheliograph (NRH) for the event of 21 April 2003. Results: The mean duration of individual bursts at fixed frequency was ~100 ms, while the instantaneous relative bandwidth was ~2%. Some bursts had measurable frequency drift, either positive or negative. Quite often spikes appeared in chains, which were closely spaced in time (column chains) or in frequency (row chains). Column chains had frequency drifts similar to type-IIId bursts, while most of the row chains exhibited negative frequently drifts with a rate close to that of fiber bursts. From the analysis of NRH data, we found that spikes were superimposed on a larger, slowly varying, background component. They were polarized in the same sense as the background source, with a slightly higher degree of polarization of ~65%, and their size was about 60% of their size in total intensity. Conclusions: The duration and bandwidth distributions did not show any clear separation in groups. Some chains tended to assume the form of zebra, lace stripes, fiber bursts, or bursts of the type-III family, suggesting that such bursts might be resolved in spikes when viewed with high

  6. SciNOvA: A Measurement of Neutrino-Nucleus Scattering in a Narrow-Band Beam

    SciTech Connect

    Paley, J.; Djurcic, Z.; Harris, D.; Tesarek, R.; Feldman, G.; Corwin, L.; Messier, M.D.; Mayer, N.; Musser, J.; Paley, J.; Tayloe, R.; /Indiana U. /Iowa State U. /Minnesota U. /South Carolina U. /Wichita State U. /William-Mary Coll.

    2010-10-15

    We propose to construct and deploy a fine-grained detector in the Fermilab NOvA 2 GeV narrow-band neutrino beam. In this beam, the detector can make unique contributions to the measurement of quasi-elastic scattering, neutral-current elastic scattering, neutral-current {pi}{sup 0} production, and enhance the NOvA measurements of electron neutrino appearance. To minimize cost and risks, the proposed detector is a copy of the SciBar detector originally built for the K2K long baseline experiment and used recently in the SciBooNE experiment.

  7. Widely tunable hybrid semiconductor lasers

    NASA Astrophysics Data System (ADS)

    Koh, Ping-Chiek; Plumb, Richard G. S.

    1999-04-01

    A new hybrid design tunable semiconductor laser, with a wide tuning range, a narrow linewidth, simple tuning/control algorithms, low variations in output power across its tuning range and simple fabrication, is introduced. This hybrid laser consists of a large spot reflective amplifier (LS-RA) coupled to a Lithium Niobate Acousto-Optic Filter (AOF), giving wavelength selective feedback. The LS-RA waveguide is angled by 10 degrees to the coupling facet, but is normal to the other facet, giving reflectivities of 5 X 10-5 and 3 X 10-1 respectively. This amplifier structure allows maximum coupling to the AOF without stringent alignment tolerance. THe AOF consists of a 2-stage acoustic TE/TM converter with a high TE reflectivity coating at the end. A propagating surface acoustic wave is employed to phase-match the TE and TM modes of a specific wavelength, achieving a narrow-band feedback into the LS-RA. Output power and wavelength of the hybrid laser are controlled by the LS-RA current and RF drive frequency of the AOF respectively. Simulations using a Time-Domain Model and initial experiments have shown that the hybrid laser have a wide tuning range, narrow linewidth, SMSR >= 30 dB and low power variations across its tuning range.

  8. Tunable semiconductor laser at 1025-1095 nm range for OCT applications with an extended imaging depth

    NASA Astrophysics Data System (ADS)

    Shramenko, Mikhail V.; Chamorovskiy, Alexander; Lyu, Hong-Chou; Lobintsov, Andrei A.; Karnowski, Karol; Yakubovich, Sergei D.; Wojtkowski, Maciej

    2015-03-01

    Tunable semiconductor laser for 1025-1095 nm spectral range is developed based on the InGaAs semiconductor optical amplifier and a narrow band-pass acousto-optic tunable filter in a fiber ring cavity. Mode-hop-free sweeping with tuning speeds of up to 104 nm/s was demonstrated. Instantaneous linewidth is in the range of 0.06-0.15 nm, side-mode suppression is up to 50 dB and polarization extinction ratio exceeds 18 dB. Optical power in output single mode fiber reaches 20 mW. The laser was used in OCT system for imaging a contact lens immersed in a 0.5% intra-lipid solution. The cross-section image provided the imaging depth of more than 5mm.

  9. [Neuroendocrine tumor of the terminal ileum observed by magnifying endoscopy with narrow-band imaging: a case report].

    PubMed

    Ishibashi, Hiroyuki; Fukita, Yosho; Toyomizu, Michifumi; Asaki, Tsutoshi; Adachi, Seitaro; Yasuda, Ikuma; Katakura, Yoshiki; Saito, Toru; Nozawa, Satoshi; Suematsu, Naomi

    2015-11-01

    We report the case of an 88-year-old woman with localized intestinal obstruction caused by a midgut neuroendocrine tumor (NET) without endocrine symptoms. She was referred to our hospital for lower abdominal pain. Abdominal enhanced computed tomography revealed a thickened wall in the terminal ileum with dilated small bowel and multiple hepatic metastases upstream. Although the presenting symptoms resolved with short-term fasting and defecation, we performed further investigation. Colonoscopy confirmed the presence of submucosal tumors in the terminal ileum with a yellow-discolored surface but without ulceration or erosion. Magnifying endoscopy with narrow-band imaging clearly showed extended and dilated vessels, with the existing vessels maintained under the epithelium. Biopsies from these lesions were immunohistochemically positive for all neuroendocrine markers, and the Ki-67 index was 10%. Therefore, the patient was diagnosed with NET, and she underwent laparoscopic surgery to relieve the intestinal obstruction. Pathological examination of the resected specimen confirmed grade 2 NET with intramural metastasis and dissemination. After follow-up for a month, octreotide long-acting repeatable therapy was initiated and the patient was free of symptoms at the 6-month follow-up. This is the first report of midgut NET observed by magnifying endoscopy with narrow-band imaging. PMID:26537328

  10. Crystal growth and characterization of the narrow-band-gap semiconductors OsPn₂ (Pn = P, As, Sb).

    PubMed

    Bugaris, Daniel E; Malliakas, Christos D; Shoemaker, Daniel P; Do, Dat T; Chung, Duck Young; Mahanti, Subhendra D; Kanatzidis, Mercouri G

    2014-09-15

    Using metal fluxes, crystals of the binary osmium dipnictides OsPn2 (Pn = P, As, Sb) have been grown for the first time. Single-crystal X-ray diffraction confirms that these compounds crystallize in the marcasite structure type with orthorhombic space group Pnnm. The structure is a three-dimensional framework of corner- and edge-sharing OsPn6 octahedra, as well as [Pn2(4-)] anions. Raman spectroscopy shows the presence of P-P single bonds, consistent with the presence of [Pn2(-4)] anions and formally Os(4+) cations. Optical-band-gap and high-temperature electrical resistivity measurements indicate that these materials are narrow-band-gap semiconductors. The experimentally determined Seebeck coefficients reveal that nominally undoped OsP2 and OsSb2 are n-type semiconductors, whereas OsAs2 is p-type. Electronic band structure using density functional theory calculations shows that these compounds are indirect narrow-band-gap semiconductors. The bonding p orbitals associated with the Pn2 dimer are below the Fermi energy, and the corresponding antibonding states are above, consistent with a Pn-Pn single bond. Thermopower calculations using Boltzmann transport theory and constant relaxation time approximation show that these materials are potentially good thermoelectrics, in agreement with experiment. PMID:25162930

  11. A polynomial chaos approach to narrow band modeling of radiative heat transfer in non-uniform gaseous media

    NASA Astrophysics Data System (ADS)

    André, Frédéric

    2016-05-01

    An accurate treatment of non-uniformities is required in many applications involving radiative heat transfer in gaseous media. Usual techniques to handle path non-uniformities rely on simplifying assumptions, such as scaling or correlation of gas spectra. Those approximations are usually accurate but may also fail to provide accurate results, especially when large temperature gradients are considered. The objective of the present work is to show that this problem can be treated rigorously. The proposed method can be applied to any arbitrary narrow band model. It is based on some results from Polynomial Chaos' framework and copulas theory. Although the mathematical derivation may appear sophisticated, applying the method is straightforward. It is shown that adding only one coefficient to any uniform narrow band model (for a simple case involving a non-uniform column discretized into two uniform sub-paths) allows to achieve almost LBL accuracy for radiative heat transfer calculations. The technique is described and applied to some "severe" test cases from the literature.

  12. Narrow-Band Search of Continuous Gravitational-Wave Signals from Crab and Vela Pulsars in Virgo VSR4 Data

    NASA Technical Reports Server (NTRS)

    Aasi, J.; Abbott, B. P.; Abbott, R.; Abbott, T.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D.; Ain, A.; Ajith, P.; Alemic, A.; Allen, B.; Allocca, A.; Amariutei, D.; Camp, J. B.; Gehrels, N.

    2015-01-01

    In this paper we present the results of a coherent narrow-band search for continuous gravitational-wave signals from the Crab and Vela pulsars conducted on Virgo VSR4 data. In order to take into account a possible small mismatch between the gravitational wave frequency and two times the star rotation frequency, inferred from measurement of the electromagnetic pulse rate, a range of 0.02 Hz around two times the star rotational frequency has been searched for both the pulsars. No evidence for a signal has been found and 95% confidence level upper limits have been computed both assuming polarization parameters are completely unknown and that they are known with some uncertainty, as derived from X-ray observations of the pulsar wind torii. For Vela the upper limits are comparable to the spin-down limit, computed assuming that all the observed spin-down is due to the emission of gravitational waves. For Crab the upper limits are about a factor of two below the spin-down limit, and represent a significant improvement with respect to past analysis. This is the first time the spin-down limit is significantly overcome in a narrow-band search.

  13. Five years of Project META - An all-sky narrow-band radio search for extraterrestrial signals

    NASA Technical Reports Server (NTRS)

    Horowitz, Paul; Sagan, Carl

    1993-01-01

    We have conducted a five-year search of the northern sky (delta between 30 and 60 deg) for narrow-band radio signals near the 1420 MHz line of neutral hydrogen, and its second harmonic, using an 8.4 x 10 exp 6 channel Fourier spectrometer of 0.05 Hz resolution and 400 kHz instantaneous bandwidth. The observing frequency was corrected both for motions with respect to three astronomical inertial frames, and for the effect of Earth's rotation, which provides a characteristic changing Doppler signature for narrow-band signals of extraterrestrial origin. Among the 6 x 10 exp 13 spectral channels searched, we have found 37 candidate events exceeding the average detection threshold of 1.7 x 10 exp -23 W/sq m, none of which was detected upon reobservation. The strongest of these appear to be dominated by rare processor errors. However, the strongest signals that survive culling for terrestrial interference lie in or near the Galactic plane. We describe the search and candidate events, and set limits on the prevalence of supercivilizations transmitting Doppler-precompensated beacons at H I or its second harmonic. We conclude with recommendations for future searches, based upon these findings, and a description of our next-generation search system.

  14. Narrow-band search of continuous gravitational-wave signals from Crab and Vela pulsars in Virgo VSR4 data

    NASA Astrophysics Data System (ADS)

    Aasi, J.; Abbott, B. P.; Abbott, R.; Abbott, T.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D.; Ain, A.; Ajith, P.; Alemic, A.; Allen, B.; Allocca, A.; Amariutei, D.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Arceneaux, C.; Areeda, J. S.; Ashton, G.; Ast, S.; Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; Aylott, B. E.; Babak, S.; Baker, P. T.; Baldaccini, F.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; Barbet, M.; Barclay, S.; Barish, B. C.; Barker, D.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Bartlett, J.; Barton, M. A.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Bauer, Th. S.; Baune, C.; Bavigadda, V.; Behnke, B.; Bejger, M.; Belczynski, C.; Bell, A. S.; Bell, C.; Benacquista, M.; Bergman, J.; Bergmann, G.; Berry, C. P. L.; Bersanetti, D.; Bertolini, A.; Betzwieser, J.; Bhagwat, S.; Bhandare, R.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Biscans, S.; Bitossi, M.; Biwer, C.; Bizouard, M. A.; Blackburn, J. K.; Blackburn, L.; Blair, C. D.; Blair, D.; Bloemen, S.; Bock, O.; Bodiya, T. P.; Boer, M.; Bogaert, G.; Bojtos, P.; Bond, C.; Bondu, F.; Bonelli, L.; Bonnand, R.; Bork, R.; Born, M.; Boschi, V.; Bose, Sukanta; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Briant, T.; Bridges, D. O.; Brillet, A.; Brinkmann, M.; Brisson, V.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brown, N. M.; Buchman, S.; Buikema, A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Cadonati, L.; Cagnoli, G.; Calderón Bustillo, J.; Calloni, E.; Camp, J. B.; Cannon, K. C.; Cao, J.; Capano, C. D.; Carbognani, F.; Caride, S.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C.; Cesarini, E.; Chakraborty, R.; Chalermsongsak, T.; Chamberlin, S. J.; Chao, S.; Charlton, P.; Chassande-Mottin, E.; Chen, Y.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.; Chu, Q.; Chua, S.; Chung, S.; Ciani, G.; Clara, F.; Clark, J. A.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colla, A.; Collette, C.; Colombini, M.; Cominsky, L.; Constancio, M.; Conte, A.; Cook, D.; Corbitt, T. R.; Cornish, N.; Corsi, A.; Costa, C. A.; Coughlin, M. W.; Coulon, J.-P.; Countryman, S.; Couvares, P.; Coward, D. M.; Cowart, M. J.; Coyne, D. C.; Coyne, R.; Craig, K.; Creighton, J. D. E.; Creighton, T. D.; Cripe, J.; Crowder, S. G.; Cumming, A.; Cunningham, L.; Cuoco, E.; Cutler, C.; Dahl, K.; Canton, T. Dal; Damjanic, M.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Dartez, L.; Dattilo, V.; Dave, I.; Daveloza, H.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.; DeBra, D.; Debreczeni, G.; Degallaix, J.; De Laurentis, M.; Deléglise, S.; Del Pozzo, W.; Denker, T.; Dent, T.; Dereli, H.; Dergachev, V.; De Rosa, R.; DeRosa, R. T.; DeSalvo, R.; Dhurandhar, S.; Díaz, M.; Di Fiore, L.; Di Lieto, A.; Di Palma, I.; Di Virgilio, A.; Dojcinoski, G.; Dolique, V.; Dominguez, E.; Donovan, F.; Dooley, K. L.; Doravari, S.; Douglas, R.; Downes, T. P.; Drago, M.; Driggers, J. C.; Du, Z.; Ducrot, M.; Dwyer, S.; Eberle, T.; Edo, T.; Edwards, M.; Edwards, M.; Effler, A.; Eggenstein, H.-B.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Essick, R.; Etzel, T.; Evans, M.; Evans, T.; Factourovich, M.; Fafone, V.; Fairhurst, S.; Fan, X.; Fang, Q.; Farinon, S.; Farr, B.; Farr, W. M.; Favata, M.; Fays, M.; Fehrmann, H.; Fejer, M. M.; Feldbaum, D.; Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Fiori, I.; Fisher, R. P.; Flaminio, R.; Fournier, J.-D.; Franco, S.; Frasca, S.; Frasconi, F.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Fritschel, P.; Frolov, V. V.; Fuentes-Tapia, S.; Fulda, P.; Fyffe, M.; Gair, J. R.; Gammaitoni, L.; Gaonkar, S.; Garufi, F.; Gatto, A.; Gehrels, N.; Gemme, G.; Gendre, B.; Genin, E.; Gennai, A.; Gergely, L. Á.; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto, A.; Gleason, J.; Goetz, E.; Goetz, R.; Gondan, L.; González, G.; Gordon, N.; Gorodetsky, M. L.; Gossan, S.; Goßler, S.; Gouaty, R.; Gräf, C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greco, G.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Groot, P.; Grote, H.; Grunewald, S.; Guidi, G. M.; Guido, C. J.; Guo, X.; Gushwa, K.; Gustafson, E. K.; Gustafson, R.; Hacker, J.; Hall, E. D.; Hammond, G.; Hanke, M.; Hanks, J.; Hanna, C.; Hannam, M. D.; Hanson, J.; Hardwick, T.; Harms, J.; Harry, G. M.; Harry, I. W.; Hart, M.; Hartman, M. T.; Haster, C.-J.; Haughian, K.; Hee, S.; Heidmann, A.; Heintze, M.; Heinzel, G.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Heptonstall, A. W.; Heurs, M.; Hewitson, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Hofman, D.; Hollitt, S. E.; Holt, K.; Hopkins, P.; Hosken, D. J.; Hough, J.; Houston, E.; Howell, E. J.; Hu, Y. M.; Huerta, E.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh, M.; Huynh-Dinh, T.; Idrisy, A.; Indik, N.; Ingram, D. R.; Inta, R.; Islas, G.; Isler, J. C.; Isogai, T.; Iyer, B. R.; Izumi, K.; Jacobson, M.; Jang, H.; Jaranowski, P.; Jawahar, S.; Ji, Y.; Jiménez-Forteza, F.; Johnson, W. W.; Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; Haris, K.; Kalogera, V.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Kasprzack, M.; Katsavounidis, E.; Katzman, W.; Kaufer, H.; Kaufer, S.; Kaur, T.; Kawabe, K.; Kawazoe, F.; Kéfélian, F.; Keiser, G. M.; Keitel, D.; Kelley, D. B.; Kells, W.; Keppel, D. G.; Key, J. S.; Khalaidovski, A.; Khalili, F. Y.; Khazanov, E. A.; Kim, C.; Kim, K.; Kim, N. G.; Kim, N.; Kim, Y.-M.; King, E. J.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Klimenko, S.; Kline, J.; Koehlenbeck, S.; Kokeyama, K.; Kondrashov, V.; Korobko, M.; Korth, W. Z.; Kowalska, I.; Kozak, D. B.; Kringel, V.; Krishnan, B.; Królak, A.; Krueger, C.; Kuehn, G.; Kumar, A.; Kumar, P.; Kuo, L.; Kutynia, A.; Landry, M.; Lantz, B.; Larson, S.; Lasky, P. D.; Lazzarini, A.; Lazzaro, C.; Lazzaro, C.; Le, J.; Leaci, P.; Leavey, S.; Lebigot, E.; Lebigot, E. O.; Lee, C. H.; Lee, H. K.; Lee, H. M.; Leonardi, M.; Leong, J. R.; Leroy, N.; Letendre, N.; Levin, Y.; Levine, B.; Lewis, J.; Li, T. G. F.; Libbrecht, K.; Libson, A.; Lin, A. C.; Littenberg, T. B.; Lockerbie, N. A.; Lockett, V.; Logue, J.; Lombardi, A. L.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J.; Lubinski, M. J.; Lück, H.; Lundgren, A. P.; Lynch, R.; Ma, Y.; Macarthur, J.; MacDonald, T.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Magaña-Sandoval, F.; Magee, R.; Mageswaran, M.; Maglione, C.; Mailand, K.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Mandel, I.; Mandic, V.; Mangano, V.; Mangano, V.; Mansell, G. L.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markosyan, A.; Maros, E.; Martelli, F.; Martellini, L.; Martin, I. W.; Martin, R. M.; Martynov, D.; Marx, J. N.; Mason, K.; Masserot, A.; Massinger, T. J.; Matichard, F.; Matone, L.; Mavalvala, N.; Mazumder, N.; Mazzolo, G.; McCarthy, R.; McClelland, D. E.; McCormick, S.; McGuire, S. C.; McIntyre, G.; McIver, J.; McLin, K.; McWilliams, S.; Meacher, D.; Meadors, G. D.; Meidam, J.; Meinders, M.; Melatos, A.; Mendell, G.; Mercer, R. A.; Meshkov, S.; Messenger, C.; Meyers, P. M.; Mezzani, F.; Miao, H.; Michel, C.; Middleton, H.; Mikhailov, E. E.; Milano, L.; Miller, A.; Miller, J.; Millhouse, M.; Minenkov, Y.; Ming, J.; Mirshekari, S.; Mishra, C.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moe, B.; Moggi, A.; Mohan, M.; Mohanty, S. D.; Mohapatra, S. R. P.; Moore, B.; Moraru, D.; Moreno, G.; Morriss, S. R.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, C. L.; Mueller, G.; Mukherjee, S.; Mullavey, A.; Munch, J.; Murphy, D.; Murray, P. G.; Mytidis, A.; Nagy, M. F.; Nardecchia, I.; Nash, T.; Naticchioni, L.; Nayak, R. K.; Necula, V.; Nedkova, K.; Nelemans, G.; Neri, I.; Neri, M.; Newton, G.; Nguyen, T.; Nielsen, A. B.; Nissanke, S.; Nitz, A. H.; Nocera, F.; Nolting, D.; Normandin, M. E. N.; Nuttall, L. K.; Ochsner, E.; O'Dell, J.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Ohme, F.; Oppermann, P.; Oram, R.; O'Reilly, B.; Ortega, W.; O'Shaughnessy, R.; Osthelder, C.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Padilla, C.; Pai, A.; Pai, S.; Palashov, O.; Palomba, C.; Pal-Singh, A.; Pan, H.; Pankow, C.; Pannarale, F.; Pant, B. C.; Paoletti, F.; Papa, M. A.; Paris, H.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patrick, Z.; Pedraza, M.; Pekowsky, L.; Pele, A.; Penn, S.; Perreca, A.; Phelps, M.; Pichot, M.; Piergiovanni, F.; Pierro, V.; Pillant, G.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Poeld, J.; Poggiani, R.; Post, A.; Poteomkin, A.; Powell, J.; Prasad, J.; Predoi, V.; Premachandra, S.; Prestegard, T.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Pürrer, M.; Qin, J.; Quetschke, V.; Quintero, E.; Quiroga, G.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Rácz, I.; Radkins, H.; Raffai, P.; Raja, S.; Rajalakshmi, G.; Rakhmanov, M.; Ramirez, K.; Rapagnani, P.; Raymond, V.; Razzano, M.; Re, V.; Reed, C. M.; Regimbau, T.; Rei, L.; Reid, S.; Reitze, D. H.; Reula, O.; Ricci, F.; Riles, K.; Robertson, N. A.; Robie, R.; Robinet, F.; Rocchi, A.; Rolland, L.; Rollins, J. G.; Roma, V.; Romano, R.; Romanov, G.; Romie, J. H.; Rosińska, D.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Sachdev, S.; Sadecki, T.; Sadeghian, L.; Saleem, M.; Salemi, F.; Sammut, L.; Sandberg, V.; Sanders, J. R.; Sannibale, V.; Santiago-Prieto, I.; Sassolas, B.; Sathyaprakash, B. S.; Saulson, P. R.; Savage, R.; Sawadsky, A.; Scheuer, J.; Schilling, R.; Schmidt, P.; Schnabel, R.; Schofield, R. M. S.; Schreiber, E.; Schuette, D.; Schutz, B. F.; Scott, J.; Scott, S. M.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sequino, V.; Serafinelli, R.; Sergeev, A.; Serna, G.; Sevigny, A.; Shaddock, D. A.; Shah, S.; Shahriar, M. S.; Shaltev, M.; Shao, Z.; Shapiro, B.; Shawhan, P.; Shoemaker, D. H.; Sidery, T. L.; Siellez, K.; Siemens, X.; Sigg, D.; Silva, A. D.; Simakov, D.; Singer, A.; Singer, L.; Singh, R.; Sintes, A. M.; Slagmolen, B. J. J.; Smith, J. R.; Smith, M. R.; Smith, R. J. E.; Smith-Lefebvre, N. D.; Son, E. J.; Sorazu, B.; Souradeep, T.; Staley, A.; Stebbins, J.; Steinke, M.; Steinlechner, J.; Steinlechner, S.; Steinmeyer, D.; Stephens, B. C.; Steplewski, S.; Stevenson, S.; Stone, R.; Strain, K. A.; Straniero, N.; Strigin, S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sutton, P. J.; Swinkels, B.; Szczepanczyk, M.; Szeifert, G.; Tacca, M.; Talukder, D.; Tanner, D. B.; Tápai, M.; Tarabrin, S. P.; Taracchini, A.; Taylor, R.; Tellez, G.; Theeg, T.; Thirugnanasambandam, M. P.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Tiwari, V.; Tomlinson, C.; Tonelli, M.; Torres, C. V.; Torrie, C. I.; Travasso, F.; Traylor, G.; Tse, M.; Tshilumba, D.; Ugolini, D.; Unnikrishnan, C. S.; Urban, A. L.; Usman, S. A.; Vahlbruch, H.; Vajente, G.; Vajente, G.; Valdes, G.; Vallisneri, M.; van Bakel, N.; van Beuzekom, M.; van den Brand, J. F. J.; van den Broeck, C.; van der Sluys, M. V.; van Heijningen, J.; van Veggel, A. A.; Vass, S.; Vasúth, M.; Vaulin, R.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, J.; Veitch, P. J.; Venkateswara, K.; Verkindt, D.; Vetrano, F.; Viceré, A.; Vincent-Finley, R.; Vinet, J.-Y.; Vitale, S.; Vo, T.; Vocca, H.; Vorvick, C.; Vousden, W. D.; Vyatchanin, S. P.; Wade, A. R.; Wade, L.; Wade, M.; Walker, M.; Wallace, L.; Walsh, S.; Wang, H.; Wang, M.; Wang, X.; Ward, R. L.; Warner, J.; Was, M.; Weaver, B.; Wei, L.-W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Welborn, T.; Wen, L.; Wessels, P.; Westphal, T.; Wette, K.; Whelan, J. T.; White, D. J.; Whiting, B. F.; Wilkinson, C.; Williams, L.; Williams, R.; Williamson, A. R.; Willis, J. L.; Willke, B.; Wimmer, M.; Winkler, W.; Wipf, C. C.; Wittel, H.; Woan, G.; Worden, J.; Xie, S.; Yablon, J.; Yakushin, I.; Yam, W.; Yamamoto, H.; Yancey, C. C.; Yang, Q.; Yvert, M.; ZadroŻny, A.; Zanolin, M.; Zendri, J.-P.; Zhang, Fan; Zhang, L.; Zhang, M.; Zhang, Y.; Zhao, C.; Zhou, M.; Zhu, X. J.; Zucker, M. E.; Zuraw, S.; Zweizig, J.; LIGO Scientific Collaboration; Virgo Collaboration

    2015-01-01

    In this paper we present the results of a coherent narrow-band search for continuous gravitational-wave signals from the Crab and Vela pulsars conducted on Virgo VSR4 data. In order to take into account a possible small mismatch between the gravitational-wave frequency and two times the star rotation frequency, inferred from measurement of the electromagnetic pulse rate, a range of 0.02 Hz around two times the star rotational frequency has been searched for both the pulsars. No evidence for a signal has been found and 95% confidence level upper limits have been computed assuming both that polarization parameters are completely unknown and that they are known with some uncertainty, as derived from x-ray observations of the pulsar wind torii. For Vela the upper limits are comparable to the spin-down limit, computed assuming that all the observed spin-down is due to the emission of gravitational waves. For Crab the upper limits are about a factor of 2 below the spin-down limit, and represent a significant improvement with respect to past analysis. This is the first time the spin-down limit is significantly overcome in a narrow-band search.

  15. Study on the characteristics of an imaging spectrum system by means of an acousto-optic tunable filter

    NASA Astrophysics Data System (ADS)

    Cui, Yan; Cui, Dunjie; Tang, Jiu-Hua

    1993-11-01

    The spectrally agile staring sensor (SASS) is an instrument system that is able to acquire image and spectrum information simultaneously. We analyze the expression of SNR and overall performance of the SASS system consisting of an acousto-optic tunable filter and point out improvement methods and limiting factors of the system performance. The complete SASS system setup is constructed. By means of this setup, the theoretical analysis is verified and the image and spectrum information of the simulated target is obtained. These results demonstrate the ability of the SASS to acquire image and spectrum information.

  16. Microwave photonic filter with two independently tunable passbands based on paralleled fiber Mach-Zehnder interferometers and dispersive medium

    NASA Astrophysics Data System (ADS)

    Xu, Zuowei; Fu, Hongyan; Chen, Hao; Wu, Congxian; Xu, Huiying; Cai, Zhiping

    2015-09-01

    In this article, we propose and experimentally demonstrate a novel microwave photonics filter (MPF) with two independently tunable passbands. The MPF is based on a sliced broadband optical source and a dispersive medium, and two paralleled fiber Mach-Zehnder interferometers (FMZIs) have been employed as the optical spectrum slicer. A coil of single-mode fiber has been used as a dispersion medium, which introduces time delay for each tap. A stable dual-passband MPF has been obtained, and the experimental results show that each passband of the MPF can be tuned freewill by adjusting the variable optical delay line (VODL) in each of the FMZIs.

  17. Narrow band deformable registration of prostate magnetic resonance imaging, magnetic resonance spectroscopic imaging, and computed tomography studies

    SciTech Connect

    Schreibmann, Eduard; Xing Lei . E-mail: lei@reyes.stanford.edu

    2005-06-01

    Purpose: Endorectal (ER) coil-based magnetic resonance imaging (MRI) and magnetic resonance spectroscopic imaging (MRSI) is often used to obtain anatomic and metabolic images of the prostate and to accurately identify and assess the intraprostatic lesions. Recent advancements in high-field (3 Tesla or above) MR techniques affords significantly enhanced signal-to-noise ratio and makes it possible to obtain high-quality MRI data. In reality, the use of rigid or inflatable endorectal probes deforms the shape of the prostate gland, and the images so obtained are not directly usable in radiation therapy planning. The purpose of this work is to apply a narrow band deformable registration model to faithfully map the acquired information from the ER-based MRI/MRSI onto treatment planning computed tomography (CT) images. Methods and Materials: A narrow band registration, which is a hybrid method combining the advantages of pixel-based and distance-based registration techniques, was used to directly register ER-based MRI/MRSI with CT. The normalized correlation between the two input images for registration was used as the metric, and the calculation was restricted to those points contained in the narrow bands around the user-delineated structures. The narrow band method is inherently efficient because of the use of a priori information of the meaningful contour data. The registration was performed in two steps. First, the two input images were grossly aligned using a rigid registration. The detailed mapping was then modeled by free form deformations based on B-spline. The limited memory Broyden-Fletcher-Goldfarb-Shanno algorithm (L-BFGS), which is known for its superior performance in dealing with high-dimensionality problems, was implemented to optimize the metric function. The convergence behavior of the algorithm was studied by self-registering an MR image with 100 randomly initiated relative positions. To evaluate the performance of the algorithm, an MR image was

  18. Versatile tunable current-mode universal biquadratic filter using MO-DVCCs and MOSFET-based electronic resistors.

    PubMed

    Chen, Hua-Pin

    2014-01-01

    This paper presents a versatile tunable current-mode universal biquadratic filter with four-input and three-output employing only two multioutput differential voltage current conveyors (MO-DVCCs), two grounded capacitors, and a well-known method for replacement of three grounded resistors by MOSFET-based electronic resistors. The proposed configuration exhibits high-output impedance which is important for easy cascading in the current-mode operations. The proposed circuit can be used as either a two-input three-output circuit or a three-input single-output circuit. In the operation of two-input three-output circuit, the bandpass, highpass, and bandreject filtering responses can be realized simultaneously while the allpass filtering response can be easily obtained by connecting appropriated output current directly without using additional stages. In the operation of three-input single-output circuit, all five generic filtering functions can be easily realized by selecting different three-input current signals. The filter permits orthogonal controllability of the quality factor and resonance angular frequency, and no inverting-type input current signals are imposed. All the passive and active sensitivities are low. Postlayout simulations were carried out to verify the functionality of the design. PMID:24982963

  19. Versatile Tunable Current-Mode Universal Biquadratic Filter Using MO-DVCCs and MOSFET-Based Electronic Resistors

    PubMed Central

    2014-01-01

    This paper presents a versatile tunable current-mode universal biquadratic filter with four-input and three-output employing only two multioutput differential voltage current conveyors (MO-DVCCs), two grounded capacitors, and a well-known method for replacement of three grounded resistors by MOSFET-based electronic resistors. The proposed configuration exhibits high-output impedance which is important for easy cascading in the current-mode operations. The proposed circuit can be used as either a two-input three-output circuit or a three-input single-output circuit. In the operation of two-input three-output circuit, the bandpass, highpass, and bandreject filtering responses can be realized simultaneously while the allpass filtering response can be easily obtained by connecting appropriated output current directly without using additional stages. In the operation of three-input single-output circuit, all five generic filtering functions can be easily realized by selecting different three-input current signals. The filter permits orthogonal controllability of the quality factor and resonance angular frequency, and no inverting-type input current signals are imposed. All the passive and active sensitivities are low. Postlayout simulations were carried out to verify the functionality of the design. PMID:24982963

  20. THE COSMIC INFRARED BACKGROUND EXPERIMENT (CIBER): THE NARROW-BAND SPECTROMETER

    SciTech Connect

    Korngut, P. M.; Bock, J.; Renbarger, T.; Keating, B.; Arai, T.; Matsumoto, T.; Matsuura, S.; Battle, J.; Hristov, V.; Lanz, A.; Levenson, L. R.; Mason, P.; Brown, S. W.; Lykke, K. R.; Smith, A. W.; Cooray, A.; Kim, M. G.; Lee, D. H.; Nam, U. W.; Shultz, B.; and others

    2013-08-15

    We have developed a near-infrared spectrometer designed to measure the absolute intensity of the solar 854.2 nm Ca II Fraunhofer line, scattered by interplanetary dust, in the zodiacal light (ZL) spectrum. Based on the known equivalent line width in the solar spectrum, this measurement can derive the zodiacal brightness, testing models of the ZL based on morphology that are used to determine the extragalactic background light in absolute photometry measurements. The spectrometer is based on a simple high-resolution tipped filter placed in front of a compact camera with wide-field refractive optics to provide the large optical throughput and high sensitivity required for rocket-borne observations. We discuss the instrument requirements for an accurate measurement of the absolute ZL brightness, the measured laboratory characterization, and the instrument performance in flight.

  1. Upgrading and testing program for narrow band high resolution planetary IR imaging spectrometer

    NASA Technical Reports Server (NTRS)

    Wattson, R. B.; Rappaport, S.

    1977-01-01

    An imaging spectrometer, intended primarily for observations of the outer planets, which utilizes an acoustically tuned optical filter (ATOF) and a charge coupled device (CCD) television camera was modified to improve spatial resolution and sensitivity. The upgraded instrument was a spatial resolving power of approximately 1 arc second, as defined by an f/7 beam at the CCD position and it has this resolution over the 50 arc second field of view. Less vignetting occurs and sensitivity is four times greater. The spectral resolution of 15 A over the wavelength interval 6500 A - 11,000 A is unchanged. Mechanical utility has been increased by the use of a honeycomb optical table, mechanically rigid yet adjustable optical component mounts, and a camera focus translation stage. The upgraded instrument was used to observe Venus and Saturn.

  2. Frequency-tunable optoelectronic oscillator using a dual-mode amplified feedback laser as an electrically controlled active microwave photonic filter.

    PubMed

    Lu, Dan; Pan, Biwei; Chen, Haibo; Zhao, Lingjuan

    2015-09-15

    A widely tunable optoelectronic oscillator (OEO) based on a self-injection-locked monolithic dual-mode amplified feedback laser (DM-AFL) is proposed and experimentally demonstrated. In the proposed OEO structure, the DM-AFL functions as an active tunable microwave photonic filter (MPF). By tuning the injection current applied on the amplifier section of the AFL, tunable microwave outputs ranging from 32 to 41 GHz and single sideband phase noises below -97  dBc/Hz at 10 kHz offset from the carriers were realized. PMID:26371931

  3. Acousto-optic-tunable-filter-based spectropolarimetric imagers for medical diagnostic applications--instrument design point of view.

    PubMed

    Gupta, Neelam

    2005-01-01

    Compact optical imagers that can detect both spectral and polarization signatures are required in many biomedical applications. An acousto-optic-tunable-filter (AOTF)-based imager is ideally suited to provide both agile spectral and polarization signatures. Such an imager can be readily used for real-time in vivo medical diagnostic applications. We develop a family of small, robust, and programmable hyperspectral imagers operating from the ultraviolet (UV) to the long-wave IR (LWIR). Such imagers require minimal data processing because they can acquire images at only select wavelengths of interest. We use AOTFs made of KDP, TeO2, and TAS with Si-based CCD, InGaAs, InSb, and HgCdTe cameras to cover different spectral regions from the UV to the LWIR. Operation of each of these imagers and image acquisition is computer controlled. The most developed imager covers the visible to near-infrared (VNIR) region from 400 to 900 nm, with a 10-nm spectral resolution at 600 nm, it uses an electronically tunable TeO2 AOTF as a bandpass filter, and a nematic liquid crystal retarder to change polarization. We describe our concept in the development of these imagers and present new results obtained using the VNIR imager. PMID:16292960

  4. Video rate imaging of narrow band THz radiation based on frequency upconversion

    NASA Astrophysics Data System (ADS)

    Tekavec, Patrick F.; Kozlov, Vladimir G.; Mcnee, Ian; Spektor, Igor E.; Lebedev, Sergey P.

    2015-03-01

    We demonstrate video rate THz imaging by detecting a frequency upconverted signal with a CMOS camera. A fiber laser pumped, double resonant optical parametric oscillator generates THz pulses via difference frequency generation in a quasi-phasematched gallium arsenide (QPM-GaAs) crystal located inside the OPO cavity. The output produced THz pulses centered at 1.5 THz, with an average power up to 1 mW, a linewidth of <100 GHz, and peak power of >2 W. By mixing the THz pulses with a portion of the fiber laser pump (1064 nm) in a second QPM-GaAs crystal, distinct sidebands are observed at 1058 nm and 1070 nm, corresponding to sum and difference frequency generation of the pump pule with the THz pulse. By using a polarizer and long pass filter, the strong pump light can be removed, leaving a nearly background free signal at 1070 nm. For imaging, a Fourier imaging geometry is used, with the object illuminated by the THz beam located one focal length from the GaAs crystal. The spatial Fourier transform is upconverted with a large diameter pump beam, after which a second lens inverse transforms the upconverted spatial components, and the image is detected with a CMOS camera. We have obtained video rate images with spatial resolution of 1mm and field of view ca. 20 mm in diameter without any post processing of the data.

  5. MWIR/LWIR filter based on Liquid-Crystal Fabry-Perot structure for tunable spectral imaging detection

    NASA Astrophysics Data System (ADS)

    Zhang, Huaidong; Muhammad, Afzal; Luo, Jun; Tong, Qing; Lei, Yu; Zhang, Xinyu; Sang, Hongshi; Xie, Changsheng

    2015-03-01

    An electrically tunable medium-wave infrared (MWIR)/long-wave infrared (LWIR) filter based on the key structure of Liquid-Crystal (LC) Fabry-Perot (FP), which works in the wavelength range from 2.5 μm to 12 μm, is designed and fabricated successfully in this paper. According to the optical interference principle of the FP cavity and electrically controlled birefringence of nematic LC molecules, the particular functions including spectral selection and spectral staring and spectral adjustment, can be realized by the developed MWIR/LWIR filter driven and controlled electrically. As to the LC-FP filter, both planar reflective mirrors are shaped by depositing a layer of aluminum (Al) film (∼60 nm) over one side of double-side polished Zinc Selenide (ZnSe) wafer (∼1 mm), and then polyimide (PI) layer with the thickness of ∼100 nm is coated directly on Al film. With typical sandwich architecture, the depth of the cavity with nematic LC molecules sealed in is ∼7.5 μm. To make sure the LC molecules parallel aligned and twist regularly under voltage driving signal applied on Al film, which also acts as electrode, the V-grooves are formed in PI layer with the depth of ∼90 nm and the width of ∼350 nm at average by strong rubbing. The typical transmission spectrum in MWIR&LWIR wavelength range and several spectral images in MWIR wavelength range based on the fabricated LC-FP filter, have been obtained through applying a voltage driving-signal with different root-means-square (RMS) value over the electrodes of LC-FP filter in the selected voltage range from 0VRMS to 19.8VRMS. The testing result demonstrates a prospect of realization smart spectral imaging and further integrating the LC-FP filter with infrared focal plane arrays (FPAs) to achieve the purpose infrared multispectral imaging. The developed MWIR&LWIR LC-FP filters show some obvious advantages such as wide working wavelength range, electrically tunable spectral selection, ultra-compact, low cost, being

  6. Tunable Fabry-Perot filter for imaging spectroscopy in the infrared

    NASA Astrophysics Data System (ADS)

    Schwarze, Craig R.; Rentz, Julia R.; Carlson, David L.; Vaillancourt, Robert M.; Genetti, George J.; Engel, James R.

    2002-02-01

    We present a new hyperspectral imaging system for the long wave infrared (LWIR) based on a tunable first-order Fabry-Perot Scanning Spectrometer (FPSS). The FPSS operates over 8 O 12 micrometers with a spectral resolution of 1% of the wavelength. The FPSS has a 22 degree field of view and a spatial resolution of 0.11 degrees. The key components of the FPSS system are the collection optics, a tunable Fabry-Perot etalon, optical position sensors, a closed-loop positioning system, an uncooled microbolometer focal plane array, a digital frame grabber card, and a user-friendly Graphical User Interface (GUI).

  7. Strong Narrow-Band Luminescence from Silicon-Vacancy Color Centers in Spatially Localized Sub-10 nm Nanodiamond

    PubMed Central

    Catledge, Shane A.; Singh, Sonal

    2011-01-01

    Discrete nanodiamond particles of 500 nm and 6 nm average size were seeded onto silicon substrates and plasma treated using chemical vapor deposition to create silicon-vacancy color centers. The resulting narrow-band room temperature photoluminescence is intense, and readily observed even for weakly agglomerated sub-10 nm size diamond. This is in contrast to the well-studied nitrogen-vacancy center in diamond which has luminescence properties that are strongly dependant on particle size, with low probability for incorporation of centers in sub-10 nm crystals. We suggest the silicon-vacancy center to be a viable alternative to nitrogen-vacancy defects for use as a biomarker in the clinically-relevant sub-10 nm size regime, for which nitrogen defect-related luminescent activity and stability is reportedly poor. PMID:21603120

  8. Technique for narrow-band imaging in the far ultraviolet based on aberration-corrected holographic gratings.

    PubMed

    Wilkinson, E; Indebetouw, R; Beasley, M

    2001-07-01

    We have developed a new family of imaging spectrometer designs that combine the imaging power of two-element telescopes with the aberration control of first-generation holographic gratings. The resulting optical designs provide high spatial resolution over modest fields of view at selectable wavelengths. These all-reflective designs are particularly suited for narrow-band imaging below 1050 A, the wavelength below which there are no transmitting materials in the UV. We have developed designs to efficiently map the spatial distribution of UV-emitting material. This mapping capability is absent in current and future astronomical instruments but is crucial to the understanding of the nature of a variety of astrophysical phenomena. Although our examples focus on UV wavelengths, the design concept is applicable to any wavelength. PMID:11958267

  9. Wide angle and narrow-band asymmetric absorption in visible and near-infrared regime through lossy Bragg stacks.

    PubMed

    Shu, Shiwei; Zhan, Yawen; Lee, Chris; Lu, Jian; Li, Yang Yang

    2016-01-01

    Absorber is an important component in various optical devices. Here we report a novel type of asymmetric absorber in the visible and near-infrared spectrum which is based on lossy Bragg stacks. The lossy Bragg stacks can achieve near-perfect absorption at one side and high reflection at the other within the narrow bands (several nm) of resonance wavelengths, whereas display almost identical absorption/reflection responses for the rest of the spectrum. Meanwhile, this interesting wavelength-selective asymmetric absorption behavior persists for wide angles, does not depend on polarization, and can be ascribed to the lossy characteristics of the Bragg stacks. Moreover, interesting Fano resonance with easily tailorable peak profiles can be realized using the lossy Bragg stacks. PMID:27251768

  10. Wide angle and narrow-band asymmetric absorption in visible and near-infrared regime through lossy Bragg stacks

    NASA Astrophysics Data System (ADS)

    Shu, Shiwei; Zhan, Yawen; Lee, Chris; Lu, Jian; Li, Yang Yang

    2016-06-01

    Absorber is an important component in various optical devices. Here we report a novel type of asymmetric absorber in the visible and near-infrared spectrum which is based on lossy Bragg stacks. The lossy Bragg stacks can achieve near-perfect absorption at one side and high reflection at the other within the narrow bands (several nm) of resonance wavelengths, whereas display almost identical absorption/reflection responses for the rest of the spectrum. Meanwhile, this interesting wavelength-selective asymmetric absorption behavior persists for wide angles, does not depend on polarization, and can be ascribed to the lossy characteristics of the Bragg stacks. Moreover, interesting Fano resonance with easily tailorable peak profiles can be realized using the lossy Bragg stacks.

  11. Total neutrino and antineutrino charged current cross section measurements in 100, 160, and 200 GeV narrow band beams

    NASA Astrophysics Data System (ADS)

    Berge, P.; Blondel, A.; Böckmann, P.; Burkhardt, H.; Dydak, F.; de Groot, J. G. H.; Grant, A. L.; Hagelberg, R.; Hughes, E. W.; Krasny, M.; Meyer, H. J.; Palazzi, P.; Ranjard, F.; Rothberg, J.; Steinberger, J.; Taureg, H.; Wachsmuth, H.; Wahl, H.; Williams, R. W.; Wotschack, J.; Wysłouch, B.; Blümer, H.; Brummel, H. D.; Buchholz, P.; Duda, J.; Eisele, F.; Kampschulte, B.; Kleinknecht, K.; Knobloch, J.; Müller, E.; Pszola, B.; Renk, B.; Belusević, R.; Falkenburg, B.; Fiedler, M.; Geiges, R.; Geweniger, C.; Hepp, V.; Keilwerth, H.; Kurz, N.; Tittel, K.; Debu, P.; Guyot, C.; Merlo, J. P.; Para, A.; Perez, P.; Perrier, F.; Rander, J.; Schuller, J. P.; Turlay, R.; Vallage, B.; Abramowicz, H.; Królikowski, J.; Lipniacka, A.

    1987-12-01

    Neutrino and antineutrino total charged current cross sections on iron were measured in the 100, 160, and 200 GeV narrow band beams at the CERN SPS in the energy range 10 to 200 GeV. Assuming σ/ E to be constant, the values corrected for non-isoscalarity are σv/E = (0.686 ± 0.019) * 10-38 cm2/ (GeV · nucleon) and σv/E = (0.339 ± 0.010) * 10-38 cm2/ (GeV·nucleon). Between 50 and 150 GeV no energy dependence of σ/ E was observed within ±3% for neutrino and ±4% for antineutrino interactions.

  12. A theory for narrow-banded radio bursts at Uranus - MHD surface waves as an energy driver

    NASA Technical Reports Server (NTRS)

    Farrell, W. M.; Curtis, S. A.; Desch, M. D.; Lepping, R. P.

    1992-01-01

    A possible scenario for the generation of the narrow-banded radio bursts detected at Uranus by the Voyager 2 planetary radio astronomy experiment is described. In order to account for the emission burstiness which occurs on time scales of hundreds of milliseconds, it is proposed that ULF magnetic surface turbulence generated at the frontside magnetopause propagates down the open/closed field line boundary and mode-converts to kinetic Alfven waves (KAW) deep within the polar cusp. The oscillating KAW potentials then drive a transient electron stream that creates the bursty radio emission. To substantiate these ideas, Voyager 2 magnetometer measurements of enhanced ULF magnetic activity at the frontside magnetopause are shown. It is demonstrated analytically that such magnetic turbulence should mode-convert deep in the cusp at a radial distance of 3 RU.

  13. First-principles study of direct and narrow band gap semiconducting β-CuGaO2

    NASA Astrophysics Data System (ADS)

    Nguyen, Manh Cuong; Zhao, Xin; Wang, Cai-Zhuang; Ho, Kai-Ming

    2015-04-01

    Semiconducting oxides have attracted much attention due to their great stability in air or water and the abundance of oxygen. Recent success in synthesizing a metastable phase of CuGaO2 with direct narrow band gap opens up new applications of semiconducting oxides as absorber layer for photovoltaics. Using first-principles density functional theory calculations, we investigate the thermodynamic and mechanical stabilities as well as the structural and electronic properties of the β-CuGaO2 phase. Our calculations show that the β-CuGaO2 structure is dynamically and mechanically stable. The energy band gap is confirmed to be direct at the Γ point of Brillouin zone. The optical absorption occurs right at the band gap edge and the density of states near the valance band maximum is large, inducing an intense absorption of light as observed in experiment.

  14. Using narrow-band J-PAS photometry to assess the properties of the stellar population in galaxies

    NASA Astrophysics Data System (ADS)

    Bruzual, Gustavo; Mejia-Narvaez, Alfredo; Magris C., Gladis

    2015-08-01

    We study the uncertainties and biases on the properties of the stellar population content of galaxies retrieved from narrow-band (J-PAS) photometry using the non-parametric method of spectral fitting dubbed DynBaS. We construct a star formation history library à la Chen et al. (2012), and then SED-fit a selection of synthetic spectra with observational properties similar to SDSS galaxies. We confront the results obtained from the photometric fits to those obtained from spectroscopic data for synthetic and real galaxies at various redshift ranges. Since no assumption on the star formation history is made, the so called template mismatch biases are naturally overcome. We find that biases in our estimations are the consequence of the several degeneracies between mass, age, metallicity, and internal dust extinction present in galaxy properties.

  15. First-principles study of direct and narrow band gap semiconducting β -CuGaO2

    DOE PAGESBeta

    Nguyen, Manh Cuong; Zhao, Xin; Wang, Cai-Zhuang; Ho, Kai-Ming

    2015-04-16

    Semiconducting oxides have attracted much attention due to their great stability in air or water and the abundance of oxygen. Recent success in synthesizing a metastable phase of CuGaO2 with direct narrow band gap opens up new applications of semiconducting oxides as absorber layer for photovoltaics. Using first-principles density functional theory calculations, we investigate the thermodynamic and mechanical stabilities as well as the structural and electronic properties of the β-CuGaO2 phase. Our calculations show that the β-CuGaO2 structure is dynamically and mechanically stable. The energy band gap is confirmed to be direct at the Γ point of Brillouin zone. Inmore » conclusion, the optical absorption occurs right at the band gap edge and the density of states near the valance band maximum is large, inducing an intense absorption of light as observed in experiment.« less

  16. Wide angle and narrow-band asymmetric absorption in visible and near-infrared regime through lossy Bragg stacks

    PubMed Central

    Shu, Shiwei; Zhan, Yawen; Lee, Chris; Lu, Jian; Li, Yang Yang

    2016-01-01

    Absorber is an important component in various optical devices. Here we report a novel type of asymmetric absorber in the visible and near-infrared spectrum which is based on lossy Bragg stacks. The lossy Bragg stacks can achieve near-perfect absorption at one side and high reflection at the other within the narrow bands (several nm) of resonance wavelengths, whereas display almost identical absorption/reflection responses for the rest of the spectrum. Meanwhile, this interesting wavelength-selective asymmetric absorption behavior persists for wide angles, does not depend on polarization, and can be ascribed to the lossy characteristics of the Bragg stacks. Moreover, interesting Fano resonance with easily tailorable peak profiles can be realized using the lossy Bragg stacks. PMID:27251768

  17. Commissioning results of the narrow-band beam position monitor system upgrade in the APS storage ring.

    SciTech Connect

    Singh, O.

    1999-04-20

    When using a low emittance storage ring as a high brightness synchrotron radiation source, it is critical to maintain a very high degree of orbit stability, both for the short term and for the duration of an operational fill. A fill-to-fill reproducibility is an additional important requirement. Recent developments in orbit correction algorithms have provided tools that are capable of achieving a high degree of orbit stability. However, the performance of these feedback systems can be severely limited if there are errors in the beam position monitors (BPMs). The present orbit measurement and correction system at the APS storage ring utilizes 360 broad-band-type BPMs that provide turn-by-turn diagnostics and an ultra-stable orbit: < 1.8 micron rms vertically and 4.5 microns rms horizontally in a frequency band of 0.017 to 30 Hz. The effects of beam intensity and bunch pattern dependency on these BPMs have been significantly reduced by employing offset compensation correction. Recently, 40 narrow-band switching-type BPMs have been installed in the APS storage ring, two in each of 20 operational insertion device straight sections, bringing the total number of beam position monitors to 400. The use of narrow-band BPM electronics is expected to reduce sensitivity to beam intensity, bunch pattern dependence, and long-term drift. These beam position monitors are used for orbit correction/feedback and machine protection interlocks for the insertion device beamlines. The commissioning results and overall performance for orbit stability are provided.

  18. Simultaneous Multi-Spectral Narrow Band Auroral Imagery From Space (1150Å to 6300Å)

    NASA Astrophysics Data System (ADS)

    Schenkel, F. W.; Ogorzalek, B. S.; Gardner, R. R.; Hutchins, R. A.; Huffman, R. E.; Larrabee, J. C.

    1986-12-01

    The design of a multi-mode instrument known as the Auroral Ionospheric Remote Sensor, AIRS, is described. The design criteria are enumerated. The goal of the AIRS instrument is to produce data on the global imaging of the auroral display in both dark and sunlit hemispheres with the remote sensing of ionospheric airglows to deduce ionospheric parameters such as electron density profiles and atmospheric background emissions. The AIRS will fly on the POLAR BEAR spacecraft in a near polar circular orbit at an altitude of 1,000 km with a scheduled launch in the fall of 1986. The AIRS instrument is designed as a multi-mode system with four (4) channels of data to yield simultaneous operation in the vacuum ultraviolet (VUV), near ultraviolet (UV) and visible spectral bands. Two of the data channels are designed to operate in the VUV with 30A windows having a 240Å separation. These two channels utilize an Ebert-Fastie spectrometer which can provide total coverage for each of these channels from 1150Å to 1800Å. The other two channels utilize a filter selector system to provide preselected, 10Å bandwidth spectral channels at 3371Å, 3914Å and 6300Å, and a 200Å wide channel centered at 2250Å. These spectral bands are paired to provide simultaneous pair coverage of 2250Å and 3371Å and simultaneous pair coverage of 3914Å and 6300Å. All four channels view the auroral scene of the north polar cap via appropriate optics and a scan mirror system. In effect a line scan image of the auroral scene is produced via the scan mirror operating in the orbit cross plane with the longitudinal direction provided by the forward motion of the spacecraft. All four channels can also operate in the photometer mode by locking of the scan mirror in the nadir viewing position. The two VUV channels can also operate in a spectrometer mode with the scan mirror locked in the nadir viewing position and the Ebert-Fastie spectrometer performing a spectral scan. The basic ground level spatial

  19. Wavelength-spacing-tunable multichannel filter incorporating a sampled chirped fiber Bragg grating based on a symmetrical chirp-tuning technique without center wavelength shift

    NASA Astrophysics Data System (ADS)

    Han, Young-Geun; Dong, Xinyong; Lee, Ju Han; Lee, Sang Bae

    2006-12-01

    We propose and experimentally demonstrate a simple and flexible scheme for a wavelength-spacing-tunable multichannel filter exploiting a sampled chirped fiber Bragg grating based on a symmetrical modification of the chirp ratio. Symmetrical bending along a sampled chirped fiber Bragg grating attached to a flexible cantilever beam induces a variation of the chirp ratio and a reflection chirp bandwidth of the grating without a center wavelength shift. Accordingly, the wavelength spacing of a sampled chirped fiber Bragg grating is continuously controlled by the reflection chirp bandwidth variation of the grating corresponding to the bending direction, which allows for realization of an effective wavelength-spacing-tunable multichannel filter. Based on the proposed technique, we achieve the continuous tunability of the wavelength spacing in a range from 1.51 to 6.11 nm, depending on the bending direction of the cantilever beam.

  20. Development and Acceptance Testing of the Dual Wheel Mechanism for the Tunable Filter Imager Cryogenic Instrument on the JWST

    NASA Technical Reports Server (NTRS)

    Leckie, Martin; Ahmad, Zakir

    2010-01-01

    The James Webb Space Telescope (JWST) will carry four scientific instruments, one of which is the Tunable Filter Imager (TFI), which is an instrument within the Fine Guidance Sensor. The Dual Wheel (DW) mechanism is being designed, built and tested by COM DEV Ltd. under contract from the Canadian Space Agency. The DW mechanism includes a pupil wheel (PW) holding seven coronagraphic masks and two calibration elements and a filter wheel (FW) holding nine blocking filters. The DW mechanism must operate at both room temperature and at 35K. Successful operation at 35K comprises positioning each optical element with the required repeatability, for several thousand occasions over the five year mission. The paper discusses the results of testing geared motors and bearings at the cryogenic temperature. In particular bearing retainer design and PGM-HT material, the effects of temperature gradients across bearings and the problems associated with cooling mechanisms down to cryogenic temperatures. The results of additional bearing tests are described that were employed to investigate an abnormally high initial torque experienced at cryogenic temperatures. The findings of these tests, was that the bearing retainer and the ball/race system could be adversely affected by the large temperature change from room temperature to cryogenic temperature and also the temperature gradient across the bearing. The DW mechanism is now performing successfully at both room temperature and at cryogenic temperature. The life testing of the mechanism is expected to be completed in the first quarter of 2010.

  1. Full-sky survey searching for ultra-narrow-band artificial CW signals: analysis of the results of Project META

    NASA Astrophysics Data System (ADS)

    Lemarchand, Guillermo A.

    1996-06-01

    Project META (Megachannel ExtraTerrestrial Assay), a full-sky survey for artificial narrow-band signals, has been conducted from the Harvard/Smithsonian 26 m radiotelescope at Agassiz Station and from one of the two 30 m radiotelescopes of the Instituto Argentino de Radioastronomia (IAR). The search was performed near the 1420 MHz line of neutral hydrogen, and its second harmonic, using two 8.4 X 10(superscript 6) channel Fourier spectrometers of 0.05 Hz resolution and 400 kHz of instantaneous bandwidth. The observing frequency was corrected both for motions with respect to three astronomical inertial frames, and for the effect of Earth's rotation, which provides a characteristic changing signature for narrow-band signals of extraterrestrial origin. Among the 6 X 10(superscript 13) spectral channels searched in the northern hemisphere, Horowitz and Sagan reported 37 candidates events exceeding the average threshold of 1.7 X 10(superscript -23) W m(superscript -2), while in the southern hemisphere among 2 X 10(superscript 13) spectral channels analyzed we found 19 events exceeding the same threshold. The strongest signals that survive culling for terrestrial interference lie in or near the Galactic Plane. The first high resolution southern target search around 71 stars (-90 degrees

  2. Pure electrical, highly-efficient and sidelobe free coherent Raman spectroscopy using acousto-optics tunable filter (AOTF)

    PubMed Central

    Meng, Zhaokai; Petrov, Georgi I.; Yakovlev, Vladislav V.

    2016-01-01

    Fast and sensitive Raman spectroscopy measurements are imperative for a large number of applications in biomedical imaging, remote sensing and material characterization. Stimulated Raman spectroscopy offers a substantial improvement in the signal-to-noise ratio but is often limited to a discrete number of wavelengths. In this report, by introducing an electronically-tunable acousto-optical filter as a wavelength selector, a novel approach to a broadband stimulated Raman spectroscopy is demonstrated. The corresponding Raman shift covers the spectral range from 600 cm−1 to 4500 cm−1, sufficient for probing most vibrational Raman transitions. We validated the use of the new instrumentation to both coherent anti-Stokes scattering (CARS) and stimulated Raman scattering (SRS) spectroscopies. PMID:26828198

  3. Pure electrical, highly-efficient and sidelobe free coherent Raman spectroscopy using acousto-optics tunable filter (AOTF)

    NASA Astrophysics Data System (ADS)

    Meng, Zhaokai; Petrov, Georgi I.; Yakovlev, Vladislav V.

    2016-02-01

    Fast and sensitive Raman spectroscopy measurements are imperative for a large number of applications in biomedical imaging, remote sensing and material characterization. Stimulated Raman spectroscopy offers a substantial improvement in the signal-to-noise ratio but is often limited to a discrete number of wavelengths. In this report, by introducing an electronically-tunable acousto-optical filter as a wavelength selector, a novel approach to a broadband stimulated Raman spectroscopy is demonstrated. The corresponding Raman shift covers the spectral range from 600 cm-1 to 4500 cm-1, sufficient for probing most vibrational Raman transitions. We validated the use of the new instrumentation to both coherent anti-Stokes scattering (CARS) and stimulated Raman scattering (SRS) spectroscopies.

  4. Pure electrical, highly-efficient and sidelobe free coherent Raman spectroscopy using acousto-optics tunable filter (AOTF).

    PubMed

    Meng, Zhaokai; Petrov, Georgi I; Yakovlev, Vladislav V

    2016-01-01

    Fast and sensitive Raman spectroscopy measurements are imperative for a large number of applications in biomedical imaging, remote sensing and material characterization. Stimulated Raman spectroscopy offers a substantial improvement in the signal-to-noise ratio but is often limited to a discrete number of wavelengths. In this report, by introducing an electronically-tunable acousto-optical filter as a wavelength selector, a novel approach to a broadband stimulated Raman spectroscopy is demonstrated. The corresponding Raman shift covers the spectral range from 600 cm(-1) to 4500 cm(-1), sufficient for probing most vibrational Raman transitions. We validated the use of the new instrumentation to both coherent anti-Stokes scattering (CARS) and stimulated Raman scattering (SRS) spectroscopies. PMID:26828198

  5. Wavelength modulation spectroscopy at 1530.32 nm for measurements of acetylene based on Fabry-Perot tunable filter

    NASA Astrophysics Data System (ADS)

    Yun-Long, Li; Bing-Chu, Yang; Xue-Mei, Xu

    2016-02-01

    Sensitive detection of acetylene (C2H2) is performed by absorption spectroscopy and wavelength modulation spectroscopy (WMS) based on Fiber Fabry-Perot tunable filter (FFP-TF) at 1530.32 nm. After being calibrated by Fiber Bragg Grating (FBG), FFP-TF is frequency-multiplexed and modulated at 20 Hz and 2.5 kHz respectively to achieve wavelength modulation. The linearity with 0.9907 fitting coefficient is obtained by measuring different concentrations in a 100 ppmv-400 ppmv range. Furthermore, the stability of the system is analyzed by detecting 50 ppmv and 100 ppmv standard gases for 2 h under room temperature and ambient pressure conditions respectively. The precision of 11 ppmv is achieved by calculating the standard deviation. Therefore, the measuring system of C2H2 detection can be applied in practical applications. Project supported by the National Natural Science Foundation of China (Grant Nos. 61172047 and 61071025).

  6. Spectral evolution and extreme value analysis of non-linear numerical simulations of narrow band random surface gravity waves.

    NASA Astrophysics Data System (ADS)

    Socquet-Juglard, H.; Dysthe, K. B.; Trulsen, K.; Liu, J.; Krogstad, H. E.

    2003-04-01

    Numerical simulations of a narrow band gaussian spectrum of random surface gravity waves have been carried out in two and three spatial dimensions [7]. Different types of non-linear Schr&{uml;o}dinger equations, [1] and [4], have been used in these simulations. Simulations have now been carried with a JONSWAP spectrum associated with a spreading function of the type cosine-squared [5]. The evolution of the spectrum, skewness, kurtosis, ... will be presented. In addition, some results about stochastic properties of the surface will be shown. Based on the approach found in [2], [3] and [6], the results are presented in terms of deviations from linear Gaussian theory and the standard second order small slope perturbation theory. begin{thebibliography}{9} bibitem{kk96} Trulsen, K. &Dysthe, K. B. (1996). A modified nonlinear Schr&{uml;o}dinger equation for broader bandwidth gravity waves on deep water. Wave Motion, 24, pp. 281-289. bibitem{BK2000} Krogstad, H.E. and S.F. Barstow (2000). A uniform approach to extreme value analysis of ocean waves, Proc. ISOPE'2000, Seattle, USA, 3, pp. 103-108. bibitem{PRK} Prevosto, M., H. E. Krogstad and A. Robin (2000). Probability distributions for maximum wave and crest heights, Coast. Eng., 40, 329-360. bibitem{ketal} Trulsen, K., Kliakhandler, I., Dysthe, K. B. &Velarde, M. G. (2000) On weakly nonlinear modulation of waves on deep water, Phys. Fluids, 12, pp. L25-L28. bibitem{onorato} Onorato, M., Osborne, A.R. and Serio, M. (2002) Extreme wave events in directional, random oceanic sea states, Phys. Fluids, 14, pp. 2432-2437. bibitem{BK2002} Krogstad, H.E. and S.F. Barstow (2002). Analysis and Applications of Second Order Models for the Maximum Crest height, % Proc. 21nd Int. Conf. Offshore Mechanics and Arctic Engineering, Oslo. Paper no. OMAE2002-28479. bibitem{JFMP} Dysthe, K. B., Trulsen, K., Krogstad, H. E. and Socquet-Juglard, H. (2002, in press) Evolution of a narrow band spectrum of random surface gravity waves, J. Fluid

  7. Electrically tunable infrared filter based on the liquid crystal Fabry-Perot structure for spectral imaging detection.

    PubMed

    Zhang, Huaidong; Muhammmad, Afzal; Luo, Jun; Tong, Qing; Lei, Yu; Zhang, Xinyu; Sang, Hongshi; Xie, Changsheng

    2014-09-01

    An electrically tunable infrared (IR) filter based on the liquid crystal (LC) Fabry-Perot (FP) key structure, which works in the wavelength range from 5.5 to 12 μm, is designed and fabricated successfully. Both planar reflective mirrors with a very high reflectivity of ∼95%, which are shaped by depositing a layer of aluminum (Al) film over one side of a double-sided polished zinc selenide wafer, are coupled into a dual-mirror FP cavity. The LC materials are filled into the FP cavity with a thickness of ∼7.5  μm for constructing the LC-FP filter, which is a typical type of sandwich architecture. The top and bottom mirrors of the FP cavity are further coated by an alignment layer with a thickness of ∼100  nm over Al film. The formed alignment layer is rubbed strongly to shape relatively deep V-grooves to anchor LC molecules effectively. Common optical tests show some particular properties; for instance, the existing three transmission peaks in the measured wavelength range, the minimum full width at half-maximum being ∼120  nm, and the maximum adjustment extent of the imaging wavelength being ∼500  nm through applying the voltage driving signal with a root mean square (RMS) value ranging from 0 to ∼19.8  V. The experiment results are consistent with the simulation, according to our model setup. The spectral images obtained in the long-wavelength IR range, through the LC-FP device driven by the voltage signal with a different RMS value, demonstrates the prospect of the realization of smart spectral imaging and further integrating the LC-FP filter with IR focal plane arrays. The developed LC-FP filters show some advantages, such as electrically tunable imaging wavelength, very high structural and photoelectronic response stability, small size and low power consumption, and a very high filling factor of more than 95% compared with common MEMS-FP spectral imaging approaches. PMID:25321356

  8. An arrayed infrared filter based on liquid crystal Fabry-Perot effect for electrically tunable spectral imaging detection

    NASA Astrophysics Data System (ADS)

    Lin, Jiuning; Tong, Qing; Luo, Jun; Lei, Yu; Zhang, Xinyu; Sang, Hongshi; Xie, Changsheng

    2015-12-01

    An arrayed electrically tunable infrared (IR) filter based on the key structure of liquid crystal Fabry-Perot (LC-FP) working in the wavelength range from 2.5 to 12 μm, is designed and fabricated successfully. According to the electrically controlled birefringence characteristics of nematic LC molecules, the refractive index of LC materials filled into a prefabricated microcavity can be adjusted by the spatial electric field stimulated between the top aluminum electrode patterned by conventional UV-photolithography and the bottom aluminum electrode in the LC-FP. The particular functions including key spectral selection and spectral adjustment, can be performed by the developed LC-FP filter driven and controlled electrically. Our experiments show that the maximum transmittance of the transmission peaks is ~24% and the peaks of transmission spectrum shift through applying different voltage signals with a root mean square (RMS) value ranging from 0 to ~21.7Vrms. The experimental results are consistent with the simulation according to the model constructed by us. As a 4-channel array-type IR filter, the top electrode of the device is composed of four same sub-electrodes, which is powered, respectively, to select desired transmission spectrum. Each of the units in the device is operated separately and synchronously, which means that spectral images of the same object can be obtained with different wavelengths in one shot. Without any mechanical parts, the developed LC-FP filter exhibits several advantages including ultra-small size, low cost, high reliability, high spectral selectivity, and compact integration.

  9. Tunable narrowband microwave photonic filter created by stimulated Brillouin scattering from a silicon nanowire

    NASA Astrophysics Data System (ADS)

    Casas-Bedoya, Alvaro; Morrison, Blair; Pagani, Mattia; Marpaung, David; Eggleton, Benjamin J.

    2015-09-01

    We demonstrate the first functional signal processing device based on stimulated Brillouin scattering in a silicon nanowire. We use only 1 dB of on-chip SBS gain to create an RF photonic notch filter with 48 dB of suppression, 98 MHz linewidth, and 6 GHz frequency tuning. This device has potential applications in on-chip microwave signal processing and establishes the foundation for the first CMOS-compatible high performance RF photonic filter.

  10. Data analysis of gravitational-wave signals from spinning neutron stars. V. A narrow-band all-sky search

    SciTech Connect

    Astone, Pia; Borkowski, Kazimierz M.; Jaranowski, Piotr; Pietka, Maciej; Krolak, Andrzej

    2010-07-15

    We present theory and algorithms to perform an all-sky coherent search for periodic signals of gravitational waves in narrow-band data of a detector. Our search is based on a statistic, commonly called the F-statistic, derived from the maximum-likelihood principle in Paper I of this series. We briefly review the response of a ground-based detector to the gravitational-wave signal from a rotating neuron star and the derivation of the F-statistic. We present several algorithms to calculate efficiently this statistic. In particular our algorithms are such that one can take advantage of the speed of fast Fourier transform in calculation of the F-statistic. We construct a grid in the parameter space such that the nodes of the grid coincide with the Fourier frequencies. We present interpolation methods that approximately convert the two integrals in the F-statistic into Fourier transforms so that the fast Fourier transform algorithm can be applied in their evaluation. We have implemented our methods and algorithms into computer codes and we present results of the Monte Carlo simulations performed to test these codes.

  11. Optimization of narrow-band uvb with a 5% oleic acid cream in the treatment of psoriasis.

    PubMed

    Martín-Ezquerra, G; Sánchez-Regaña, M; Umbert-Millet, P

    2007-03-01

    Oleic acid is a monounsaturated fatty acid with a known action of penetration enhancer which has been used for various purposes, such as a tanning increaser. Narrow-band ultraviolet B (UVB) is a also first-line treatment for psoriasis. The purpose of this study was to evaluate if the use of a 5% oleic acid emulsion previous to the phototherapy sessions was useful in reducing the total dosage necessary for whitening in patients with psoriasis. Forty-four patients were included, 24 received application of the emulsion before phototherapy and 20 received phototherapy with no emulsion. Patients received the UVB sessions just to achieve a reduction of 80% of the basal PASI. The total dose received and number of sessions were compared within the 2 groups. A reduction in these parameters (29.68 J/cm(2) vs. 18.16 J/cm(2); 24 vs. 19 sessions) was seen in the group that received application of the emulsion. However, this was not statistically significant. The fact that we did not achieve the statistical significance may be due to the small sample size. These results must be cautiously interpreted and confirmed with further studies. PMID:17373190

  12. Banks of templates for all-sky narrow-band searches of gravitational waves from spinning neutron stars

    NASA Astrophysics Data System (ADS)

    Pisarski, Andrzej; Jaranowski, Piotr

    2015-07-01

    We construct efficient banks of templates suitable for all-sky narrow-band searches of almost monochromatic gravitational waves originating from spinning neutron stars in our Galaxy in data collected by interferometric detectors. We consider waves with one spindown parameter included, and we assume that both the position of the gravitational-wave source in the sky and the wave's frequency, together with spindown parameter, are unknown. In the construction we employ a simplified model of the signal with constant amplitude and phase which is a linear function of unknown parameters. Our template banks enable the usage of the fast Fourier transform algorithm in the computation of the maximum-likelihood {F}-statistic for nodes of the grids defining the bank, and fulfill an additional constraint needed to resample the data to barycentric time efficiently. All these template bank features were employed in the recent all-sky {F}-statistic-based search for continuous gravitational waves in Virgo VSR1 data (Aasi et al 2014 Class. Quantum Grav. 31 165014). Here we improve that template bank by constructing templates suitable for a larger range of search parameters and of smaller thicknesses for certain values of search parameters. One of our template banks has a thickness 12% smaller than that of the template bank used in the all-sky search of Virgo VSR1 data and only 4% larger than the thickness of the four-dimensional optimal lattice covering {A}4\\star .

  13. 1.064-μm laser damage studies of silicon oxy-nitride narrow band reflectors

    NASA Astrophysics Data System (ADS)

    Milward, Jonathan R.; Lewis, Keith L.; Sheach, K.; Heinecke, Rudolf A.

    1994-07-01

    In a paper presented at the 1992 Boulder Damage Symposium, we discussed the role of electric field effects, defect type, surface roughness, film thickness and coating absorption on the laser damage thresholds of sinusoidally modulated, plasma deposited, silicon oxy-nitride narrow band reflectors. We concluded that the damage threshold, which was essentially constant at 2 J/cm2 at the test wavelength of 0.532 micrometers , was defect dominated. A sizeable fraction of the damage events occurred at a particular type of defect--a hemispherical hillock feature typically 5 micrometers in diameter as identified by SEM and interferometric surface profiling. We postulated that this defect initiated damage because of either a microlensing effect or an enhanced electric field effect. We have since measured the laser damage thresholds of all these samples at 1.064 micrometers , and found significant variations in the damage thresholds, which were a factor of three higher on average than those at 0.532 micrometers . The microlens model presented can explain damage thresholds up to a factor of four higher at the longer wavelength, and predicts a minimum nodule height for increased damage susceptibility. The minimum nodule height is dependent on the wavelength and the coating average index. The wavelength scaling of the fluence enhancement and the minimum nodule height imply that nodule initiated damage will become an even more serious problem as the wavelength approaches the UV.

  14. Narrow Band Ultraviolet B Treatment for Human Vitiligo Is Associated with Proliferation, Migration, and Differentiation of Melanocyte Precursors.

    PubMed

    Goldstein, Nathaniel B; Koster, Maranke I; Hoaglin, Laura G; Spoelstra, Nicole S; Kechris, Katerina J; Robinson, Steven E; Robinson, William A; Roop, Dennis R; Norris, David A; Birlea, Stanca A

    2015-08-01

    In vitiligo, the autoimmune destruction of epidermal melanocytes produces white spots that can be repigmented by melanocyte precursors from the hair follicles, following stimulation with UV light. We examined by immunofluorescence the distribution of melanocyte markers (C-KIT, DCT, PAX3, and TYR) coupled with markers of proliferation (KI-67) and migration (MCAM) in precursors and mature melanocytes from the hair follicle and the epidermis of untreated and narrow band UVB (NBUVB)-treated human vitiligo skin. NBUVB was associated with a significant increase in the number of melanocytes in the infundibulum and with restoration of the normal melanocyte population in the epidermis, which was lacking in the untreated vitiligo. We identified several precursor populations (melanocyte stem cells, melanoblasts, and other immature phenotypes), and progressively differentiating melanocytes, some with putative migratory and/or proliferative abilities. The primary melanocyte germ was present in the untreated and treated hair follicle bulge, whereas a possible secondary melanocyte germ composed of C-KIT+ melanocytes was found in the infundibulum and interfollicular epidermis of UV-treated vitiligo. This is an exceptional model for studying the mobilization of melanocyte stem cells in human skin. Improved understanding of this process is essential for designing better treatments for vitiligo, ultimately based on melanocyte stem cell activation and mobilization. PMID:25822579

  15. Objective quantification of the vocal fold vascular pattern: comparison of narrow band imaging and white light endoscopy.

    PubMed

    Pliske, Gerald; Voigt-Zimmermann, Susanne; Glaßer, Sylvia; Arens, Christoph

    2016-09-01

    No clinical standard procedure has yet been defined to quantify the vascular pattern of vocal folds. Subjective classification trials have shown a lot of promise. Narrow band imaging (NBI) as an endoscopic imaging tool is useful, because it shows the vascular structure clearer than white light endoscopy (WL) alone. Endoscopic images of 74 human vocal folds (NBI and WL) were semi-automatically evaluated after image processing with respect to pixels of vessels and mucosa by the software MeVisLab. The ratios of vessel/mucosa pixels were compared. Using NBI, more vocal fold vessels are visible compared with WL alone (p = 0.000). There may be a difference between the right and left vocal folds due to the handedness of the examiner (p = 0.033) without any interaction between the method (NBI/WL) and the side (right/left) (p = 0.467). MeVisLab is a suitable tool for the objective quantification of the vessel/mucosa ratio for NBI and WL endoscopic images. NBI is an appropriate endoscopic tool for examination of diseases of vocal folds with changes in the vascular pattern. There is evidence that the handedness of the examiner may have an influence on the quality of the examination between the right and left vocal folds. PMID:27126337

  16. Narrow Band Ultraviolet B Treatment for Human Vitiligo Is Associated with Proliferation, Migration, and Differentiation of Melanocyte Precursors

    PubMed Central

    Goldstein, Nathaniel B.; Koster, Maranke I.; Hoaglin, Laura G.; Spoelstra, Nicole S.; Kechris, Katerina J.; Robinson, Steven E.; Robinson, William A.; Roop, Dennis R.; Norris, David A.; Birlea, Stanca A.

    2015-01-01

    In vitiligo, the autoimmune destruction of epidermal melanocytes produces white spots that can be repigmented by melanocyte precursors from the hair follicles, following stimulation with UV light. We examined by immunofluorescence the distribution of melanocyte markers (C-KIT, DCT, PAX3, and TYR) coupled with markers of proliferation (KI-67) and migration (MCAM) in precursors and mature melanocytes from the hair follicle and the epidermis of untreated and narrow band UVB (NBUVB)-treated human vitiligo skin. NBUVB was associated with a significant increase in the number of melanocytes in the infundibulum and with restoration of the normal melanocyte population in the epidermis, which was lacking in the untreated vitiligo. We identified several precursor populations (melanocyte stem cells, melanoblasts, and other immature phenotypes), and progressively differentiating melanocytes, some with putative migratory and/or proliferative abilities. The primary melanocyte germ was present in the untreated and treated hair follicle bulge, whereas a possible secondary melanocyte germ composed of C-KIT+ melanocytes was found in the infundibulum and interfollicular epidermis of UV-treated vitiligo. This is an exceptional model for studying the mobilization of melanocyte stem cells in human skin. Improved understanding of this process is essential for designing better treatments for vitiligo, ultimately based on melanocyte stem cell activation and mobilization. PMID:25822579

  17. Light-Emitting Diode-Assisted Narrow Band Imaging Video Endoscopy System in Head and Neck Cancer

    PubMed Central

    Chang, Hsin-Jen; Wang, Wen-Hung; Chang, Yen-Liang; Jeng, Tzuan-Ren; Wu, Chun-Te; Angot, Ludovic; Lee, Chun-Hsing

    2015-01-01

    Background/Aims To validate the effectiveness of a newly developed light-emitting diode (LED)-narrow band imaging (NBI) system for detecting early malignant tumors in the oral cavity. Methods Six men (mean age, 51.5 years) with early oral mucosa lesions were screened using both the conventional white light and LED-NBI systems. Results Small elevated or ulcerative lesions were found under the white light view, and typical scattered brown spots were identified after shifting to the LED-NBI view for all six patients. Histopathological examination confirmed squamous cell carcinoma. The clinical stage was early malignant lesions (T1), and the patients underwent wide excision for primary cancer. This is the pilot study documenting the utility of a new LED-NBI system as an adjunctive technique to detect early oral cancer using the diagnostic criterion of the presence of typical scattered brown spots in six high-risk patients. Conclusions Although large-scale screening programs should be established to further verify the accuracy of this technology, its lower power consumption, lower heat emission, and higher luminous efficiency appear promising for future clinical applications. PMID:25844342

  18. Echolocation in sympatric Peale's dolphins (Lagenorhynchus australis) and Commerson's dolphins (Cephalorhynchus commersonii) producing narrow-band high-frequency clicks.

    PubMed

    Kyhn, L A; Jensen, F H; Beedholm, K; Tougaard, J; Hansen, M; Madsen, P T

    2010-06-01

    An increasing number of smaller odontocetes have recently been shown to produce stereotyped narrow-band high-frequency (NBHF) echolocation clicks. Click source parameters of NBHF clicks are very similar, and it is unclear whether the sonars of individual NBHF species are adapted to specific habitats or the presence of other NBHF species. Here, we test whether sympatric NBHF species sharing the same habitat show similar adaptations in their echolocation clicks and whether their clicks display signs of character displacement. Wide-band sound recordings were obtained with a six-element hydrophone array from wild Peale's (Lagenorhynchus australis) and Commerson's (Cephalorhynchus commersonii) dolphins off the Falkland Islands. The centroid frequency was different between Commerson's (133+/-2 kHz) and Peale's (129+/-3 kHz) dolphins. The r.m.s. bandwidth was 12+/-3 kHz for both species. The source level was higher for Peale's dolphin (185+/-6 dB re 1 muPa p.-p.) than for Commerson's (177+/-5 dB re 1 muPa p.-p.). The mean directivity indexes were 25 dB for both species. The relatively low source levels in combination with the high directivity index may be an adaptation to reduce clutter when foraging in a coastal environment. We conclude that the small species-specific shifts in distribution of centroid frequencies around 130 kHz may reflect character displacement in otherwise-stereotyped NBHF clicks. PMID:20472781

  19. In-plane deeply-etched optical MEMS notch filter with high-speed tunability

    NASA Astrophysics Data System (ADS)

    Sabry, Yasser M.; Eltagoury, Yomna M.; Shebl, Ahmed; Soliman, Mostafa; Sadek, Mohamed; Khalil, Diaa

    2015-12-01

    Notch filters are used in spectroscopy, multi-photon microscopy, fluorescence instrumentation, optical sensors and other life science applications. One type of notch filter is based on a fiber-coupled Fabry-Pérot cavity, which is formed by a reflector (external mirror) facing a dielectric-coated end of an optical fiber. Tailoring this kind of optical filter for different applications is possible because the external mirror has fewer mechanical and optical constraints. In this paper we present optical modeling and implementation of a fiber-coupled Fabry-Pérot filter based on dielectric-coated optical fiber inserted into a micromachined fiber groove facing a metallized micromirror, which is driven by a high-speed MEMS actuator. The optical MEMS chip is fabricated using deep reactive ion etching (DRIE) technology on a silicon on insulator wafer, where the optical axis is parallel to the substrate (in-plane) and the optical/mechanical components are self-aligned by the photolithographic process. The DRIE etching depth is 150 μm, chosen to increase the micromirror optical throughput and improving the out-of-plane stiffness of the MEMS actuator. The MEMS actuator type is closing-gap, while its quality factor is almost doubled by slotting the fixed plate. A low-finesse Fabry-Pérot interferometer is formed by the metallized surface of the micromirror and a cleaved end of a standard single-mode fiber, for characterization of the MEMS actuator stroke and resonance frequency. The actuator achieves a travel distance of 800 nm at a resonance frequency of 89.9 kHz. The notch filter characteristics were measured using an optical spectrum analyzer, and the filter exhibits a free spectral range up to 100 nm and a notch rejection ratio up to 20 dB around a wavelength of 1300 nm. The presented device provides batch processing and low-cost production of the filter.

  20. Large Format Narrow-Band, Multi-Band, and Broad-Band LWIR QWIP Focal Planes for Space and Earth Science Applications

    NASA Technical Reports Server (NTRS)

    Gunapala, S. D.; Bandara, S. V.

    2004-01-01

    A 640x512 pixel, long-wavelength cutoff, narrow-band (delta(lambda)/approx. 10%) quantum well infrared photodetector (QWIP) focal plane array (FPA), a four-band QWIP FPA in the 4-16 m spectral region, and a broad-band (delta(lambda)/approx. 42%) QWIP FPA having 15.4 m cutoff have been demonstrated.

  1. Tunable multi-wavelength thulium-doped fiber laser incorporating two-stage cascaded Sagnac loop comb filter

    NASA Astrophysics Data System (ADS)

    Zhu, Lianqing; He, Wei; Dong, Mingli; Lou, Xiaoping; Luo, Fei

    2016-08-01

    A tunable multi-wavelength narrow-linewidth thulium-doped fiber laser employing two-stage cascaded Sagnac loop mirrors is proposed and experimentally demonstrated. The designed fiber laser is composed of a pump source, wavelength division multiplex, circulator, thulium-doped fiber, polarization controllers (PCs), couplers and polarization-maintaining fibers (PMFs). Two cascaded Sagnac loops are used as the cavity reflector and filter, and the proposed filter is fabricated using two sections of PMFs with 2-m and 1-m lengths, respectively. In the experiment, the laser threshold is 110 mW, and laser can emit single, double, triple, quadruple and quintuple wavelengths in the spectral range of 1873-1901 nm through the simultaneous adjustment of the two PCs. The power fluctuations and 3-dB linewidth are less than 2.1 dB and 0.2 nm, respectively, over 10 min at room temperature, and the side-mode suppression ratio is greater than 20 dB. The proposed laser will be useful in various fields, such as spectral analysis, fiber sensing and optical communication.

  2. A rapid excitation-emission matrix fluorometer utilizing supercontinuum white light and acousto-optic tunable filters

    NASA Astrophysics Data System (ADS)

    Wang, Wenbo; Wu, Zhenguo; Zhao, Jianhua; Lui, Harvey; Zeng, Haishan

    2016-06-01

    Scanning speed and coupling efficiency of excitation light to optic fibres are two major technical challenges that limit the potential of fluorescence excitation-emission matrix (EEM) spectrometer for on-line applications and in vivo studies. In this paper, a novel EEM system, utilizing a supercontinuum white light source and acousto-optic tunable filters (AOTFs), was introduced and evaluated. The supercontinuum white light, generated by pumping a nonlinear photonic crystal fiber with an 800 nm femtosecond laser, was efficiently coupled into a bifurcated optic fiber bundle. High speed EEM spectral scanning was achieved using AOTFs both for selecting excitation wavelength and scanning emission spectra. Using calibration lamps (neon and mercury argon), wavelength deviations were determined to vary from 0.18 nm to -0.70 nm within the spectral range of 500-850 nm. Spectral bandwidth for filtered excitation light broadened by twofold compared to that measured with monochromatic light between 650 nm and 750 nm. The EEM spectra for methanol solutions of laser dyes were successfully acquired with this rapid fluorometer using an integration time of 5 s.

  3. A rapid excitation-emission matrix fluorometer utilizing supercontinuum white light and acousto-optic tunable filters.

    PubMed

    Wang, Wenbo; Wu, Zhenguo; Zhao, Jianhua; Lui, Harvey; Zeng, Haishan

    2016-06-01

    Scanning speed and coupling efficiency of excitation light to optic fibres are two major technical challenges that limit the potential of fluorescence excitation-emission matrix (EEM) spectrometer for on-line applications and in vivo studies. In this paper, a novel EEM system, utilizing a supercontinuum white light source and acousto-optic tunable filters (AOTFs), was introduced and evaluated. The supercontinuum white light, generated by pumping a nonlinear photonic crystal fiber with an 800 nm femtosecond laser, was efficiently coupled into a bifurcated optic fiber bundle. High speed EEM spectral scanning was achieved using AOTFs both for selecting excitation wavelength and scanning emission spectra. Using calibration lamps (neon and mercury argon), wavelength deviations were determined to vary from 0.18 nm to -0.70 nm within the spectral range of 500-850 nm. Spectral bandwidth for filtered excitation light broadened by twofold compared to that measured with monochromatic light between 650 nm and 750 nm. The EEM spectra for methanol solutions of laser dyes were successfully acquired with this rapid fluorometer using an integration time of 5 s. PMID:27370436

  4. Fast wavelength-tunable picosecond pulses from a passively mode-locked Er fiber laser using a galvanometer-driven intracavity filter.

    PubMed

    Ozeki, Yasuyuki; Tashiro, Daigo

    2015-06-15

    We experimentally investigate fast wavelength-tuning characteristics of a polarization-maintaining Er fiber laser, which is mode-locked with a semiconductor saturable absorber mirror. Wavelength tuning was accomplished with an intracavity filter incorporating a galvanometer mirror and a diffraction grating. Within the tunability of 30 nm, we achieved a wavelength-tuning speed of <5 ms. We also show that the variation of repetition rates can be suppressed to <200 Hz by simply shifting the position of the grating. The presented scheme for generating wavelength-tunable pulses will be potentially useful for coherent Raman spectral imaging. PMID:26193501

  5. Use of acousto-optic tunable filter in fluorescence imaging endoscopy

    NASA Astrophysics Data System (ADS)

    Bouhifd, Mounir; Whelan, Maurice; Aprahamian, Marc

    2003-10-01

    A prototype instrument for fluorescence-based medical diagnostics in vivo is described. The system consists of a rigid endoscope comprising a UV laser-source for fluorescence excitation and a white light source for direct imaging. An acousto-optic tuneable filter (AOTF) is employed as a full-field tuneable bandpass filter. This allows fast continuous or random-access tuning with high filtering efficiency. A study of the diagnostic potential of fluorescence imaging for pancreatitis was conducted on a rat model. In particular, the aim was to detect autofluorescence of endogenous protoporphyrin IX (PpIX) that has been shown to accumulate in early-stage diseased tissue undergoing an inflammatory response.

  6. Tunable filter and optical buffer based on dual plasmonic ring resonators

    NASA Astrophysics Data System (ADS)

    Li, Boxun; Li, Hongjian; Zeng, Lili; Zhan, Shiping; Cao, Guangtao; He, Zhihui; Yang, Hui

    2015-02-01

    We demonstrate the realization of on chip plasmon-induced transparency using dual ring resonators coupling to metal-dielectric-metal bus waveguide. The theoretical results agree well with the finite-difference time-domain simulative ones. Moreover, by adjusting the radius, width, as well as the coupling distance can efficiently operate the wavelengths and bandwidths of our filter. In theory, we propose a feasible method to improve the trade-off between transmission and quality factor. Finally, the ultra-compact structure possesses slow light effect and manifests a low group velocity, which provides a guideline to control the light and has potential application in optical filter and optical buffer.

  7. Tunable wavevector and spin filtering in graphene induced by resonant tunneling

    NASA Astrophysics Data System (ADS)

    Lu, Wei-Tao; Li, Wen; Wang, Yong-Long; Jiang, Hua; Xu, Chang-Tan

    2013-08-01

    The resonant tunneling in graphene superlattices with an exchange field is studied theoretically. The results show that a resonant tunneling occurs in the transmission gap by virtue of the transverse wave vector. The position, width, and number of resonant tunneling can be effectively manipulated by adjusting the barrier strength, barrier width, and well width, respectively, which indicates the remarkable wavevector filtering behavior. This resonant effect together with the exchange splitting can be utilized to design an efficient spin filter. It is also found that the energy spectrum in the bound region displays bandlike distribution due to the coupling of eigenstates.

  8. Tunable narrowband microwave photonic filter created by stimulated Brillouin scattering from a silicon nanowire.

    PubMed

    Casas-Bedoya, Alvaro; Morrison, Blair; Pagani, Mattia; Marpaung, David; Eggleton, Benjamin J

    2015-09-01

    We demonstrate the first, to the best of our knowledge, functional signal processing device based on stimulated Brillouin scattering in a silicon nanowire. We use only 1 dB of on-chip stimulated Brillouin scattering gain to create an RF photonic notch filter with 48 dB of suppression, 98 MHz linewidth, and 6 GHz frequency tuning. This device has potential applications in on-chip microwave signal processing and establishes the foundation for the first CMOS-compatible high-performance RF photonic filter. PMID:26368735

  9. Dual-tunable multiferroic active ring filter for microwave photonic oscillators

    NASA Astrophysics Data System (ADS)

    Vitko, V. V.; Nikitin, A. A.; Ustinov, A. B.; Kalinikos, B. A.

    2015-12-01

    A theoretical model of a microwave active ring filter based on a ferrite-ferroelectric layered structure serving as a waveguide for spin-electromagnetic waves is developed. An experimental prototype of the device is fabricated and characterized. The device is implemented as an active-ring resonator with a microwave amplifier and a ferrite-ferroelectric delay line. The resonance properties of this system are studied theoretically and experimentally. The results show dual control of central frequency of the filter with magnetic and electric fields. An effective Q-factor of 50 000 and tuning by 5 MHz with an electric field are achieved at 8 GHz.

  10. Wide-aperture acousto-optic tunable filters for visible and UV lights

    NASA Astrophysics Data System (ADS)

    Ponomarev, Andrei N.; Rodionov, Igor D.; Teterin, George E.

    1995-02-01

    Acousto optic filters (AOF) with optical size approximately 8 - 10 mm for visible and ultraviolet spectrum on the base of TeO2 and KH2 PO4 crystals correspondingly are developed and manufactured. The spectral resolution is better than 1 nm. The frequency bandwidth of both filters is 55 - 90 MHz, that allows us to use the only high frequency generator with two different power amplifiers. Acoustic power level for the AOFs on the base of TeO2 and KH2PO4 was about 1 W and 5 W, respectively. The optical tuning is carried out by means of a computer program.

  11. A strain-tunable nanoimprint lithography for linear variable photonic crystal filters.

    PubMed

    Liu, Longju; Khan, Haris A; Li, Jingjing; Hillier, Andrew C; Lu, Meng

    2016-07-22

    This paper presents the fabrication methodology of a linear variable photonic crystal (PC) filter with narrowband reflection that varies over a broad spectral range along the length of the filter. The key component of the linear variable PC filter is a polymer surface-relief grating whose period changes linearly as a function of its position on the filter. The grating is fabricated using a nanoreplica molding process with a wedge-shaped elastomer mold. The top surface of the mold carries the grating pattern and the wedge is formed by a shallow angle between the top and bottom surfaces of the mold. During the replica molding process, a uniaxial force is applied to stretch the mold, resulting in a nearly linearly varying grating period. The period of the grating is determined using the magnitude of the force and the local thickness of the mold. The grating period of the fabricated device spans a range of 421.8-463.3 nm over a distance of 20 mm. A high refractive index dielectric film is deposited on the graded-period grating to act as the waveguide layer of the PC device. The resonance reflection feature of the device varies linearly in a range of 680.2-737.0 nm over the length of the grating. PMID:27276512

  12. A strain-tunable nanoimprint lithography for linear variable photonic crystal filters

    NASA Astrophysics Data System (ADS)

    Liu, Longju; Khan, Haris A.; Li, Jingjing; Hillier, Andrew C.; Lu, Meng

    2016-07-01

    This paper presents the fabrication methodology of a linear variable photonic crystal (PC) filter with narrowband reflection that varies over a broad spectral range along the length of the filter. The key component of the linear variable PC filter is a polymer surface-relief grating whose period changes linearly as a function of its position on the filter. The grating is fabricated using a nanoreplica molding process with a wedge-shaped elastomer mold. The top surface of the mold carries the grating pattern and the wedge is formed by a shallow angle between the top and bottom surfaces of the mold. During the replica molding process, a uniaxial force is applied to stretch the mold, resulting in a nearly linearly varying grating period. The period of the grating is determined using the magnitude of the force and the local thickness of the mold. The grating period of the fabricated device spans a range of 421.8–463.3 nm over a distance of 20 mm. A high refractive index dielectric film is deposited on the graded-period grating to act as the waveguide layer of the PC device. The resonance reflection feature of the device varies linearly in a range of 680.2–737.0 nm over the length of the grating.

  13. Bandwidth-tunable narrowband rectangular optical filter based on stimulated Brillouin scattering in optical fiber.

    PubMed

    Wei, Wei; Yi, Lilin; Jaouën, Yves; Hu, Weisheng

    2014-09-22

    We propose a rectangular optical filter based on stimulated Brillouin scattering (SBS) in optical fiber with bandwidth tuning from 50 MHz to 4 GHz at less than 15-MHz resolution. The rectangular shape of the filter is precisely achieved utilizing digital feedback control of the comb-like pump spectral lines. The passband ripple is suppressed to ~1 dB by mitigating the nonlinearity influences of the comb-like pump lines generated in electrical and optical components and fibers. Moreover a fiber with a single Brillouin peak is employed to further reduce the in-band ripple and the out-of-band SBS gain at the same time. Finally, we analyze the noise performance of the filter at different bandwidth cases and demonstrate the system performance of the proposed filter with 2.1-GHz bandwidth and 19-dB gain by amplifying a 2-GHz orthogonal frequency-division-multiplexing (OFDM) signal with quadrature-phase-shift-keying (QPSK) and 16-quadrature-amplitude-modulation (16-QAM) on each subscriber. PMID:25321794

  14. A tunable biquad switched-capacitor amplifier-filter for neural recording.

    PubMed

    Jongwoo Lee; Johnson, Matthew D; Kipke, Daryl R

    2010-10-01

    With the emerging interest in local field potentials (LFPs) as input signals for brain-machine interfaces, there is a need for integrated circuits capable of amplifying spikes and LFPs. A two-stage complementary metal-oxide semiconductor (CMOS) amplifier-filter has been implemented with 0.18-μm CMOS for simultaneous, multimodal recording of extracellular unit spikes and LFPs. For the frequency tuning and the reduction of the 1/f noise, it employs a switched-capacitor technique. The filter bandwidth is reconfigurable by using a different sampling clock frequency. The prototype amplifier has gains of 19.1 dB and 37.5 dB for low-pass only filter and cascaded filter, respectively. With a 100-kHz sampling frequency, the equivalent input noise spectral density is 38.8 nV/√Hz while the total power consumption is 69 μW with a 1.6-V supply, including clock generation and biasing occupying an area of 44 × 148 μm(2). PMID:23853375

  15. Band-gap tunable dielectric elastomer filter for low frequency noise

    NASA Astrophysics Data System (ADS)

    Jia, Kun; Wang, Mian; Lu, Tongqing; Zhang, Jinhua; Wang, Tiejun

    2016-05-01

    In the last decades, diverse materials and technologies for sound insulation have been widely applied in engineering. However, suppressing the noise radiation at low frequency still remains a challenge. In this work, a novel membrane-type smart filter, consisting of a pre-stretched dielectric elastomer membrane with two compliant electrodes coated on the both sides, is presented to control the low frequency noise. Since the stiffness of membrane dominates its acoustic properties, sound transmission band-gap of the membrane filter can be tuned by adjusting the voltage applied to the membrane. The impedance tube experiments have been carried out to measure the sound transmission loss (STL) of the filters with different electrodes, membrane thickness and pre-stretch conditions. The experimental results show that the center frequency of sound transmission band-gap mainly depends on the stress in the dielectric elastomer, and a large band-gap shift (more than 60 Hz) can be achieved by tuning the voltage applied to the 85 mm diameter VHB4910 specimen with pre-stretch {λ }0=3. Based on the experimental results and the assumption that applied electric field is independent of the membrane behavior, 3D finite element analysis has also been conducted to calculate the membrane stress variation. The sound filter proposed herein may provide a promising facility to control low frequency noise source with tonal characteristics.

  16. Atomic and electronic structures evolution of the narrow band gap semiconductor Ag2Se under high pressure.

    PubMed

    Naumov, P; Barkalov, O; Mirhosseini, H; Felser, C; Medvedev, S A

    2016-09-28

    Non-trivial electronic properties of silver telluride and other chalcogenides, such as the presence of a topological insulator state, electronic topological transitions, metallization, and the possible emergence of superconductivity under pressure have attracted attention in recent years. In this work, we studied the electronic properties of silver selenide (Ag2Se). We performed direct current electrical resistivity measurements, in situ Raman spectroscopy, and synchrotron x-ray diffraction accompanied by ab initio calculations to explore pressure-induced changes to the atomic and electronic structure of Ag2Se. The temperature dependence of the electrical resistivity was measured up to 30 GPa in the 4-300 K temperature interval. Resistivity data showed an unusual increase in the thermal energy gap of phase I, which is a semiconductor under ambient conditions. Recently, a similar effect was reported for the 3D topological insulator Bi2Se3. Raman spectroscopy studies revealed lattice instability in phase I indicated by the softening of observed vibrational modes with pressure. Our hybrid functional band structure calculations predicted that phase I of Ag2Se would be a narrow band gap semiconductor, in accordance with experimental results. At a pressure of ~7.5 GPa, Ag2Se underwent a structural transition to phase II with an orthorhombic Pnma structure. The temperature dependence of the resistivity of Ag2Se phase II demonstrated its metallic character. Ag2Se phase III, which is stable above 16.5 GPa, is also metallic according to the resistivity data. No indication of the superconducting transition is found above 4 K in the studied pressure range. PMID:27439023

  17. Atomic and electronic structures evolution of the narrow band gap semiconductor Ag2Se under high pressure

    NASA Astrophysics Data System (ADS)

    Naumov, P.; Barkalov, O.; Mirhosseini, H.; Felser, C.; Medvedev, S. A.

    2016-09-01

    Non-trivial electronic properties of silver telluride and other chalcogenides, such as the presence of a topological insulator state, electronic topological transitions, metallization, and the possible emergence of superconductivity under pressure have attracted attention in recent years. In this work, we studied the electronic properties of silver selenide (Ag2Se). We performed direct current electrical resistivity measurements, in situ Raman spectroscopy, and synchrotron x-ray diffraction accompanied by ab initio calculations to explore pressure-induced changes to the atomic and electronic structure of Ag2Se. The temperature dependence of the electrical resistivity was measured up to 30 GPa in the 4–300 K temperature interval. Resistivity data showed an unusual increase in the thermal energy gap of phase I, which is a semiconductor under ambient conditions. Recently, a similar effect was reported for the 3D topological insulator Bi2Se3. Raman spectroscopy studies revealed lattice instability in phase I indicated by the softening of observed vibrational modes with pressure. Our hybrid functional band structure calculations predicted that phase I of Ag2Se would be a narrow band gap semiconductor, in accordance with experimental results. At a pressure of ~7.5 GPa, Ag2Se underwent a structural transition to phase II with an orthorhombic Pnma structure. The temperature dependence of the resistivity of Ag2Se phase II demonstrated its metallic character. Ag2Se phase III, which is stable above 16.5 GPa, is also metallic according to the resistivity data. No indication of the superconducting transition is found above 4 K in the studied pressure range.

  18. Preparation of narrow band gap V2O5/TiO2 composite films by micro-arc oxidation

    NASA Astrophysics Data System (ADS)

    Luo, Qiang; Li, Xin-wei; Cai, Qi-zhou; Yan, Qing-song; Pan, Zhen-hua

    2012-11-01

    V2O5/TiO2 composite films were prepared on pure titanium substrates via micro-arc oxidation (MAO) in electrolytes consisting of NaVO3. Their morphology and elements were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis. Phase composition and valence states of species in the films were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Ultraviolet-visible diffuse reflectance spectra (UV-Vis DRS) were also employed to evaluate the photophysical property of the films. The V2O5/TiO2 composite films show a sheet-like morphology. Not only V2O5 phase appears in the films when the NaVO3 concentration of the electrolyte is higher than 6.10 g/L and is loaded at the surface of anatase, but also V4+ is incorporated into the crystal lattice of anatase. In comparison with pure TiO2 films the V2O5/TiO2 composite films exhibit significantly narrow band gap energy. The film prepared in an electrolyte consisting of NaVO3 with a concentration of 8.54 g/L exhibits the narrowest band gap energy, which is approximately 1.89 eV. The V2O5/TiO2 composite films also have the significantly enhanced visible light photocatalytic activity. The film prepared in an electrolyte consisting of NaVO3 with a concentration of 8.54 g/L exhibits the best photocatalytic activity and about 93% of rhodamine is degraded after 14 h visible light radiation.

  19. Value of Magnifying Endoscopy With Narrow-Band Imaging and Confocal Laser Endomicroscopy in Detecting Gastric Cancerous Lesions

    PubMed Central

    Gong, Shuai; Xue, Han-Bing; Ge, Zhi-Zheng; Dai, Jun; Li, Xiao-Bo; Zhao, Yun-Jia; Zhang, Yao; Gao, Yun-Jie; Song, Yan

    2015-01-01

    Abstract Although the respective potentials of magnifying endoscopy with narrow-band imaging (ME-NBI) and confocal laser endomicroscopy (CLE) in predicting gastric cancer has been well documented, there is a lack of studies in comparing the value and diagnostic strategy of these 2 modalities. Our primary aim is to investigate whether CLE is superior to ME-NBI for differentiation between gastric cancerous and noncancerous lesions. A secondary aim is to propose an applicable clinical strategy. We conducted a diagnostic accuracy study involving patients with suspected gastric superficial cancerous lesions. White light endoscopy, ME-NBI, and CLE were performed diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive value between ME-NBI and CLE were assessed, as well as agreements between ME-NBI/CLE and histopathology. This study involved 86 gastric lesions in 82 consecutive patients who underwent white light endoscopy, ME-NBI, and CLE before biopsy. The accuracy, sensitivity, and specificity for ME-NBI were 93.75%, 91.67%, and 95.45%, compared with 91.86%, 90%, and 93.48%, respectively, for CLE, for discrimination cancerous/noncancerous lesion (all P > 0.05). For undifferentiated/differentiated adenocarcinoma, CLE had a numerically but not statistically significantly higher accuracy than ME-NBI (81.25% vs 73.33%, P = 0.46). Agreements between ME-NBI/CLE and histopathology were near perfect (ME-NBI, κ = 0.87; CLE, κ = 0.84). CLE is not superior to ME-NBI for discriminating gastric cancerous from noncancerous lesions. Endoscopist could make an optimal choice according to the specific indication and advantages of ME-NBI and CLE in daily practices. PMID:26554797

  20. Gate-tunable valley-spin filtering in silicene with magnetic barrier

    SciTech Connect

    Wu, X. Q.; Meng, H.

    2015-05-28

    We theoretically study the valley- and spin-resolved scattering through magnetic barrier in a one layer thick silicene, using the mode-matching method for the Dirac equation. We show that the spin-valley filtering effect can be achieved and can also be tuned completely through both a top and bottom gate. Moreover, when reversing the sign of the staggered potential, we find the direction of the valley polarization is switched while the direction of spin polarization is unchanged. These results can provide some meaningful information to design valley valve residing on silicene.

  1. A tunable electrochromic fabry-perot filter for adaptive optics applications.

    SciTech Connect

    Blaich, Jonathan David; Kammler, Daniel R.; Ambrosini, Andrea; Sweatt, William C.; Verley, Jason C.; Heller, Edwin J.; Yelton, William Graham

    2006-10-01

    The potential for electrochromic (EC) materials to be incorporated into a Fabry-Perot (FP) filter to allow modest amounts of tuning was evaluated by both experimental methods and modeling. A combination of chemical vapor deposition (CVD), physical vapor deposition (PVD), and electrochemical methods was used to produce an ECFP film stack consisting of an EC WO{sub 3}/Ta{sub 2}O{sub 5}/NiO{sub x}H{sub y} film stack (with indium-tin-oxide electrodes) sandwiched between two Si{sub 3}N{sub 4}/SiO{sub 2} dielectric reflector stacks. A process to produce a NiO{sub x}H{sub y} charge storage layer that freed the EC stack from dependence on atmospheric humidity and allowed construction of this complex EC-FP stack was developed. The refractive index (n) and extinction coefficient (k) for each layer in the EC-FP film stack was measured between 300 and 1700 nm. A prototype EC-FP filter was produced that had a transmission at 500 nm of 36%, and a FWHM of 10 nm. A general modeling approach that takes into account the desired pass band location, pass band width, required transmission and EC optical constants in order to estimate the maximum tuning from an EC-FP filter was developed. Modeling shows that minor thickness changes in the prototype stack developed in this project should yield a filter with a transmission at 600 nm of 33% and a FWHM of 9.6 nm, which could be tuned to 598 nm with a FWHM of 12.1 nm and a transmission of 16%. Additional modeling shows that if the EC WO{sub 3} absorption centers were optimized, then a shift from 600 nm to 598 nm could be made with a FWHM of 11.3 nm and a transmission of 20%. If (at 600 nm) the FWHM is decreased to 1 nm and transmission maintained at a reasonable level (e.g. 30%), only fractions of a nm of tuning would be possible with the film stack considered in this study. These tradeoffs may improve at other wavelengths or with EC materials different than those considered here. Finally, based on our limited investigation and material set

  2. Tunable negative-tap photonic microwave filter based on a cladding-mode coupler and an optically injected laser of large detuning.

    PubMed

    Chan, Sze-Chun; Liu, Qing; Wang, Zhu; Chiang, Kin Seng

    2011-06-20

    A tunable negative-tap photonic microwave filter using a cladding-mode coupler together with optical injection locking of large wavelength detuning is demonstrated. Continuous and precise tunability of the filter is realized by physically sliding a pair of bare fibers inside the cladding-mode coupler. Signal inversion for the negative tap is achieved by optical injection locking of a single-mode semiconductor laser. To couple light into and out of the cladding-mode coupler, a pair of matching long-period fiber gratings is employed. The large bandwidth of the gratings requires injection locking of an exceptionally large wavelength detuning that has never been demonstrated before. Experimentally, injection locking with wavelength detuning as large as 27 nm was achieved, which corresponded to locking the 36-th side mode. Microwave filtering with a free-spectral range tunable from 88.6 MHz to 1.57 GHz and a notch depth larger than 35 dB was obtained. PMID:21716440

  3. Ultrasensitive and compact tunable electro-optic filter in a 2D silicon photonic-crystal cavity

    NASA Astrophysics Data System (ADS)

    Ebrahimy, Mehdi N.; Naziri, Mohammad; Andalib, Alireza; Daie Kuzekanani, Ziaddin

    2016-06-01

    In this work, we designed and simulated a high Q-factor photonic crystal cavity with a PN junction to demonstrate a high-sensitivity and high tunable electro-optic filter (EOF). For this purpose, we used a cavity based on 2D photonic crystal structures and created a PN junction with 1 μm width in the center of the cavity to change the refractive index of it. The electro-optic sensitivity of the cavity was improved by reducing modal volume and scattering power. Reverse bias in the range of (‑3.88 V–0.288 V) is applied to the PN junction and the output spectrum is investigated for various bias voltages. The output wavelengths of designed EOF can be tuned by manipulating cavity cells. In final response of EOF the maximum transmission efficiency is more than 93%, the overall Q-factor is more than 14 500. The whole device fits in a compact 102.6 μm2 (17.4 μm  ×  5.9 μm) footprint.

  4. Validity of retinal oxygen saturation analysis: Hyperspectral imaging in visible wavelength with fundus camera and liquid crystal wavelength tunable filter

    NASA Astrophysics Data System (ADS)

    Hirohara, Yoko; Okawa, Yoshitaka; Mihashi, Toshifumi; Yamaguchi, Tatsuo; Nakazawa, Naoki; Tsuruga, Yasuko; Aoki, Hiroyuki; Maeda, Naoyuki; Uchida, Ichiro; Fujikado, Takashi

    2007-05-01

    The purpose of this paper was to investigate the feasibility of a newly developed hyperspectral fundus imaging camera with a liquid crystal tunable filter. The intensities of different wavelengths of light transmitted through an artery, vein, and the area surrounding these vessels and reflected out were measured, and the differential spectral absorptions were analyzed. Measurements were made from 16 normal eyes and from two artificial capillaries. The ratios of absorption (ROA) of arteries to veins from 500 to 580 nm (range 1) and from 600 to 720 nm (range 2) were calculated. For all eyes, the ROArange1 was larger than ROArange2. The ROA obtained from the artificial capillary filled with blood saturated with oxygen or nitrogen was similar to that of simulated data of oxy- and deoxyhemoglobin extinction rate. Most ROAs of human eyes were lower than those of the simulated data and the artificial capillaries. Oxygen saturation analysis by hyperspectral fundus imaging of retinal vessels were qualitatively in agreement with the in vitro analysis or simulated values. However, further improvements are necessary to evaluate the oxygen saturation quantitatively in the retinal blood vessels.

  5. Ultra-compact, broadband tunable optical bandstop filters based on a multimode one-dimensional photonic crystal waveguide.

    PubMed

    Huang, Qingzhong; Jie, Kun; Liu, Qiang; Huang, Ying; Wang, Yi; Xia, Jinsong

    2016-09-01

    In this paper, ultra-compact, broadband tunable optical bandstop filters (OBSFs) based on a multimode one-dimensional photonic crystal waveguide (PhCW) are proposed and systematically investigated. For the wavelengths in the mini-stopband, the input mode is coupled to a contra-propagating higher order mode by the PhCW and then radiates in a taper, resulting in a stopband at the output with low backreflection at the input. Three-dimensional finite-difference time-domain method is employed to study the OBSFs. The influence of main structural parameters is analyzed, and the design is optimized to reduce the back-reflection and band sidelobes. Using localized heating, we can shift the stopband and tune the bandwidth continuously by cascading the proposed structures. Due to the strong grating strength, our device provides a more compact footprint (40 μm × 1 μm) and much broader stopband (bandwidth of up to 84 nm), compared to the counterparts based on microrings, long-period waveguide gratings, and multimode two-dimensional PhCWs. PMID:27607658

  6. Multiple-channel optical signal processing with wavelength-waveform conversions, pulsewidth tunability, and signal regeneration.

    PubMed

    Nguyen Tan, Hung; Matsuura, Motoharu; Katafuchi, Tomoya; Kishi, Naoto

    2009-12-01

    A multiple-channel multiple-function optical signal processor (MCMF-OSP) including wavelength-waveform conversions, pulsewidth tunability, and signal regeneration is realized through AND logic gate based on optical parametric processing with a pulsewidth-tunable RZ clock pump. The proposed scheme simultaneously offers four signal processing functions which are useful in wavelength-division multiplexing (WDM) transmission systems, and at network nodes with the necessity for multiple-channel data processing. After the discussions on the concept of MCMF-OSP, a proof-of concept experiment is demonstrated on four 10 Gb/s nonreturn-to-zero (NRZ) data format channels using nonlinearities in semiconductor optical amplifier (SOA) and highly nonlinear fiber (HNLF). A wavelength and waveform conversions to return-to-zero (RZ) modulation format are obtained together with pulsewidth-tunable range from 20% to 80% duty cycles for all input signals. The converted signals inherit the timing and waveform of the RZ clock pump, thus resulting in a time regeneration and large tolerance to narrow-band optical filtering (NAOF) and fiber accumulated chromatic dispersion (CD). PMID:20052222

  7. Analysis of one-dimensional photonic band gap structures with a liquid crystal defect towards development of fiber-optic tunable wavelength filters.

    PubMed

    Del Villar, Ignacio; Matias, Ignacio; Arregui, Francisco; Claus, Richard

    2003-03-10

    A theoretical analysis of a fiber optical photonic band gap based tunable wavelength filter is presented. The design presented here is based on the quarter wave reflector with a liquid crystal defect layer in the middle of the structure. The filter generated by the structure is shifted in wavelength as the voltage applied to the structure is modified. Some critical parameters are analyzed: the effect of the consideration of fiber as the first layer and not the input medium in the shape of the filter, the number of layers of the structure, and the thickness of the defect layer. This last parameter determines the width of the wavelength sweep of the filter, but is limited by the creation of more defects. Some rules of practical implementation of this device are also given. PMID:19461749

  8. A tunable line filter polychromator for gas temperature measurements using laser Raman scattering

    NASA Technical Reports Server (NTRS)

    Grossman, J. J.; Muramoto, M.

    1975-01-01

    A proprietary laser line filter spectrograph (LLFS) was modified to test for improved remote measurement of atmospheric temperature by Raman spectroscopy of the rotational bands of N2 and O2. Both grating scan measurements with fixed PMT and polychromator image plane PMT scans with fixed grating setting were made using HeNe and Ar(+) lasers. The LLFS was found to have a laser line rejection ratio at 6A from the laser line and provides resolved rotational Raman spectral display at the polychromator exit plane. Spectral resolution is adequate to measure and correct for background in the Stokes spectrum. It is anticipated that this system should allow measurement of gas or atmospheric temperature to + or - 1 C.

  9. An optimized strain demodulation method for PZT driven fiber Fabry-Perot tunable filter

    NASA Astrophysics Data System (ADS)

    Sheng, Wenjuan; Peng, G. D.; Liu, Yang; Yang, Ning

    2015-08-01

    An optimized strain-demodulation-method based on piezo-electrical transducer (PZT) driven fiber Fabry-Perot (FFP) filter is proposed and experimentally demonstrated. Using a parallel processing mode to drive the PZT continuously, the hysteresis effect is eliminated, and the system demodulation rate is increased. Furthermore, an AC-DC compensation method is developed to address the intrinsic nonlinear relationship between the displacement and voltage of PZT. The experimental results show that the actual demodulation rate is improved from 15 Hz to 30 Hz, the random error of the strain measurement is decreased by 95%, and the deviation between the test values after compensation and the theoretical values is less than 1 pm/με.

  10. Realization of spectral tunable filter based on thermal effect in microfiber structure

    NASA Astrophysics Data System (ADS)

    Nodehi, S.; Mohammed, W. S.; Ahmad, H.; Harun, S. W.

    2016-03-01

    This paper demonstrates a new approach for tuning the extinction ratio of a complex microfiber structure output using thermal effect. The microfiber filter device comprises of a microfiber Mach-Zehnder interferometer followed a knot structure, where temperature is controlled by a DC current applied to a copper wire placed inside the knot. This enables electrical tuning, where applying electrical current increases the temperature and affects the optical path. The change of temperature facilitates the fine tuning of the resonance output spectrum. From the experiment, it was observed that the extinction ratio of the output comb spectrum can be controlled within 2 dB to 10 dB by varying the current rating from 0 A to 1.22 A.

  11. Design of a Mechanical-Tunable Filter Spectrometer for Noninvasive Glucose Measurement

    NASA Astrophysics Data System (ADS)

    Saptari, Vidi; Youcef-Toumi, Kamal

    2004-05-01

    The development of an accurate and reliable noninvasive near-infrared (NIR) glucose sensor hinges on the success in addressing the sensitivity and the specificity problems associated with the weak glucose signals and the overlapping NIR spectra. Spectroscopic hardware parameters most relevant to noninvasive blood glucose measurement are discussed, which include the optical throughput, integration time, spectral range, and the spectral resolution. We propose a unique spectroscopic system using a continuously rotating interference filter, which produces a signal-to-noise ratio of the order of 10^5 and is estimated to be the minimum required for successful in vivo glucose sensing. Using a classical least-squares algorithm and a spectral range between 2180 and 2312 nm, we extracted clinically relevant glucose concentrations in multicomponent solutions containing bovine serum albumin, triacetin, lactate, and urea.

  12. Tunable ultracompact chip-integrated multichannel filter based on plasmon-induced transparencies

    SciTech Connect

    Yang, Xiaoyu; Chai, Zhen; Lu, Cuicui; Yang, Hong; Hu, Xiaoyong E-mail: qhgong@pku.edu.cn; Gong, Qihuang E-mail: qhgong@pku.edu.cn

    2014-06-02

    Nanoscale multichannel filter is realized in plasmonic circuits directly, which consists of four plasmonic nanocavities coupled via a plasmonic waveguide etched in a gold film. The feature device size is only 1.35 μm, which is reduced by five orders of magnitude compared with previous reports. The optical channels are formed by transparency windows of plasmon-induced transparencies. A shift of 45 nm in the central wavelengths of optical channels is obtained when the plasmonic coupled-nanocavities are covered with a 100-nm-thick poly(methyl methacrylate) layer. This work opens up the possibility for the realization of solid quantum chips based on plasmonic circuits.

  13. Weak Broadband Electromagnetic Fields are More Disruptive to Magnetic Compass Orientation in a Night-Migratory Songbird (Erithacus rubecula) than Strong Narrow-Band Fields

    PubMed Central

    Schwarze, Susanne; Schneider, Nils-Lasse; Reichl, Thomas; Dreyer, David; Lefeldt, Nele; Engels, Svenja; Baker, Neville; Hore, P. J.; Mouritsen, Henrik

    2016-01-01

    Magnetic compass orientation in night-migratory songbirds is embedded in the visual system and seems to be based on a light-dependent radical pair mechanism. Recent findings suggest that both broadband electromagnetic fields ranging from ~2 kHz to ~9 MHz and narrow-band fields at the so-called Larmor frequency for a free electron in the Earth’s magnetic field can disrupt this mechanism. However, due to local magnetic fields generated by nuclear spins, effects specific to the Larmor frequency are difficult to understand considering that the primary sensory molecule should be organic and probably a protein. We therefore constructed a purpose-built laboratory and tested the orientation capabilities of European robins in an electromagnetically silent environment, under the specific influence of four different oscillating narrow-band electromagnetic fields, at the Larmor frequency, double the Larmor frequency, 1.315 MHz or 50 Hz, and in the presence of broadband electromagnetic noise covering the range from ~2 kHz to ~9 MHz. Our results indicated that the magnetic compass orientation of European robins could not be disrupted by any of the relatively strong narrow-band electromagnetic fields employed here, but that the weak broadband field very efficiently disrupted their orientation. PMID:27047356

  14. Weak Broadband Electromagnetic Fields are More Disruptive to Magnetic Compass Orientation in a Night-Migratory Songbird (Erithacus rubecula) than Strong Narrow-Band Fields.

    PubMed

    Schwarze, Susanne; Schneider, Nils-Lasse; Reichl, Thomas; Dreyer, David; Lefeldt, Nele; Engels, Svenja; Baker, Neville; Hore, P J; Mouritsen, Henrik

    2016-01-01

    Magnetic compass orientation in night-migratory songbirds is embedded in the visual system and seems to be based on a light-dependent radical pair mechanism. Recent findings suggest that both broadband electromagnetic fields ranging from ~2 kHz to ~9 MHz and narrow-band fields at the so-called Larmor frequency for a free electron in the Earth's magnetic field can disrupt this mechanism. However, due to local magnetic fields generated by nuclear spins, effects specific to the Larmor frequency are difficult to understand considering that the primary sensory molecule should be organic and probably a protein. We therefore constructed a purpose-built laboratory and tested the orientation capabilities of European robins in an electromagnetically silent environment, under the specific influence of four different oscillating narrow-band electromagnetic fields, at the Larmor frequency, double the Larmor frequency, 1.315 MHz or 50 Hz, and in the presence of broadband electromagnetic noise covering the range from ~2 kHz to ~9 MHz. Our results indicated that the magnetic compass orientation of European robins could not be disrupted by any of the relatively strong narrow-band electromagnetic fields employed here, but that the weak broadband field very efficiently disrupted their orientation. PMID:27047356

  15. A 1.1-1.9 GHz SETI SURVEY OF THE KEPLER FIELD. I. A SEARCH FOR NARROW-BAND EMISSION FROM SELECT TARGETS

    SciTech Connect

    Siemion, Andrew P. V.; Korpela, Eric; Werthimer, Dan; Cobb, Jeff; Lebofsky, Matt; Marcy, Geoffrey W.; Demorest, Paul; Maddalena, Ron J.; Langston, Glen; Howard, Andrew W.; Tarter, Jill

    2013-04-10

    We present a targeted search for narrow-band (<5 Hz) drifting sinusoidal radio emission from 86 stars in the Kepler field hosting confirmed or candidate exoplanets. Radio emission less than 5 Hz in spectral extent is currently known to only arise from artificial sources. The stars searched were chosen based on the properties of their putative exoplanets, including stars hosting candidates with 380 K > T{sub eq} > 230 K, stars with five or more detected candidates or stars with a super-Earth (R{sub p} < 3 R{sub Circled-Plus }) in a >50 day orbit. Baseband voltage data across the entire band between 1.1 and 1.9 GHz were recorded at the Robert C. Byrd Green Bank Telescope between 2011 February and April and subsequently searched offline. No signals of extraterrestrial origin were found. We estimate that fewer than {approx}1% of transiting exoplanet systems host technological civilizations that are radio loud in narrow-band emission between 1 and 2 GHz at an equivalent isotropically radiated power (EIRP) of {approx}1.5 Multiplication-Sign 10{sup 21} erg s{sup -1}, approximately eight times the peak EIRP of the Arecibo Planetary Radar, and we limit the number of 1-2 GHz narrow-band-radio-loud Kardashev type II civilizations in the Milky Way to be <10{sup -6} M{sub Sun }{sup -1}. Here we describe our observations, data reduction procedures and results.

  16. A 1.1-1.9 GHz SETI Survey of the Kepler Field. I. A Search for Narrow-band Emission from Select Targets

    NASA Astrophysics Data System (ADS)

    Siemion, Andrew P. V.; Demorest, Paul; Korpela, Eric; Maddalena, Ron J.; Werthimer, Dan; Cobb, Jeff; Howard, Andrew W.; Langston, Glen; Lebofsky, Matt; Marcy, Geoffrey W.; Tarter, Jill

    2013-04-01

    We present a targeted search for narrow-band (<5 Hz) drifting sinusoidal radio emission from 86 stars in the Kepler field hosting confirmed or candidate exoplanets. Radio emission less than 5 Hz in spectral extent is currently known to only arise from artificial sources. The stars searched were chosen based on the properties of their putative exoplanets, including stars hosting candidates with 380 K > T eq > 230 K, stars with five or more detected candidates or stars with a super-Earth (R p < 3 R ⊕) in a >50 day orbit. Baseband voltage data across the entire band between 1.1 and 1.9 GHz were recorded at the Robert C. Byrd Green Bank Telescope between 2011 February and April and subsequently searched offline. No signals of extraterrestrial origin were found. We estimate that fewer than ~1% of transiting exoplanet systems host technological civilizations that are radio loud in narrow-band emission between 1 and 2 GHz at an equivalent isotropically radiated power (EIRP) of ~1.5 × 1021 erg s-1, approximately eight times the peak EIRP of the Arecibo Planetary Radar, and we limit the number of 1-2 GHz narrow-band-radio-loud Kardashev type II civilizations in the Milky Way to be {<}10^{-6}\\ M^{-1}_\\odot. Here we describe our observations, data reduction procedures and results.

  17. Highly-efficient, tunable green, phosphor-converted LEDs using a long-pass dichroic filter and a series of orthosilicate phosphors for tri-color white LEDs.

    PubMed

    Oh, Ji Hye; Oh, Jeong Rok; Park, Hoo Keun; Sung, Yeon-Goog; Do, Young Rag

    2012-01-01

    This study introduces a long-pass dichroic filter (LPDF) on top of a phosphor-converted LED (pc-LED) packing associated with each corresponding tunable orthosilicate ((Ba,Sr)2SiO4:Eu) phosphor in order to fabricate tunable green pc-LEDs. These LPDF-capped green pc-LEDs provide luminous efficacies between 143–173 lm/W at 60 mA in a wavelength range between 515 and 560 nm. These tunable green pc-LEDs can replace green semiconductor-type III-V LEDs, which present challenges with respect to generating high luminous efficacy. We also introduce the highly-efficient tunable green pc-LEDs into tri-color white LED systems that combine an InGaN blue LED and green/red full down-converted pc-LEDs. The effect of peak wavelength in the tunable green pc-LEDs on the optical properties of a tri-color package white LED is analyzed to determine the proper wavelength of green color for tri-color white LEDs. The tri-color white LED provides excellent luminous efficacy (81.5–109 lm/W) and a good color rendering index (64–87) at 6500 K of correlated color temperature (CCT) with the peak wavelength of green pc-LEDs. The luminous efficacy of the LPDF-capped green monochromatic pc-LED and tri-color package with tunable green pc-LEDs can be increased by improving the external quantum efficiency of blue LEDs and the conversion efficiency of green pc-LEDs. PMID:22379669

  18. Analysis of all-optically tunable functionalities in subwavelength periodic structures by the Fourier modal method

    NASA Astrophysics Data System (ADS)

    Bej, Subhajit; Tervo, Jani; Francés, Jorge; Svirko, Yuri P.; Turunen, Jari

    2016-05-01

    We propose the nonlinear Fourier Modal Method (FMM) [J. Opt. Soc. Am. B 31, 2371 (2014)] as a convenient and versatile numerical tool for the design and analysis of grating based next generation all-optical devices. Here, we include several numerical examples where the FMM is used to simulate all-optically tunable functionalities in sub-wavelength periodic structures. At first, we numerically investigate a 1-D periodic nonlinear binary grating with amorphous TiO2. We plot the diffraction efficiency in the transmitted orders against the structure depth for normally incident plane wave. Change in diffraction efficiencies for different incident field amplitudes are evident from the plots. We verify the accuracy of our implementation by comparing our results with the results obtained with the nonlinear Split Field-Finite Difference Time Domain (SF-FDTD) method. Next we repeat the same experiment with vertically standing amorphous Titanium dioxide (TiO2) nanowire arrays grown on top of quartz which are periodic in two mutually perpendicular directions and examine the efficiencies in the direct transmitted light for different incident field amplitudes. Our third example includes analysis of a form birefringent linear grating with Kerr medium. With FMM we demonstrate that the birefringence of such a structure can be tuned by all-optical means. As a final example, we design a narrow band Guided Mode Resonance Filter (GMRF). Numerical experiments based on the nonlinear FMM reveal that the spectral tunability of such a filter can be obtained by all-optical means.

  19. Filtration at the microfluidic level: enrichment of nanoparticles by tunable filters.

    PubMed

    Boettcher, M; Schmidt, S; Latz, A; Jaeger, M S; Stuke, M; Duschl, C

    2011-08-17

    We present an electrohydrodynamic device for filtration of nanometre-sized particles from suspensions. A high-frequency electric field is locally generated through the action of mutually parallel microelectrodes integrated into a microfluidic channel. Due to the mechanism of ohmic heating, a thermal gradient arises above these electrodes. In conjunction with temperature-sensitive properties of the fluid, an eddy flow behaviour emerges in the laminar environment. This acts as an adjustable filter. For quantification of the filtration efficiency, we tested a wide range of particle concentrations at different electric field strengths and overall external flow velocities. Particles with a diameter of 200 nm were retained in this manner at rates of up to 100%. Numerical simulations of a model taking into account the hydrodynamic as well as electric conditions, but no interactions between the point-shaped particles, yield results that are similar to the experiment in both the flow trajectories and the particle accumulation. Our easy technique could become a valuable tool that complements conventional filtration methods for handling nanometre-scaled particles in medicine and biotechnology, e.g. bacteria and viruses. PMID:21795763

  20. Instrumentation for time-resolved dynamic and static dichroic measurements of polymers with a near-IR acoustooptic tunable filter

    NASA Astrophysics Data System (ADS)

    Sweat, Joseph Allen

    1999-11-01

    The optical measurement of the orientational response of chemical functional groups of a polymer as it is subjected to conventional dynamic mechanical analysis can give insight into the rheological behavior of the polymer while under repetitive strain based on the chemical structure. Instrumentation used in the mid infrared has included the use of grating monochromators and interferometers. The use of a multiply modulated optical signal has decreased the level of noise to observe the small amplitude changes (typically >10-3 absorbance units) associated with the repetitive oscillatory strain. The use of digital signal processing to replace phase sensitive detection for demodulation of the optical signal has greatly reduced the spectral collection time. In addition, multiplexing gained with the use of step-scan interferometry in making time resolved measurements has aided in making the procedure more practical. However, instrumental complexity and expense are drawbacks. By incorporating the high throughput, polarized tuned beam, and rapid wavelength switching capability of an acousto-optic tunable filter (AOTF), a dynamic instrument with integrated centralized control by a single microprocessor has been built. it operates in the near infrared with a rapid dynamic data collection time and requires the use of only a single modulation in the form of the sample oscillatory strain. The near infrared permits thicker samples to reduce sample preparation tune or allows polymers to be tested without pretreatment. The use of Fourier based digital filtering improves the signal to noise ratio of the dynamic differential spectra. The instrument is cost effective and rugged in comparison to step-scan interferometers yet has a rapid data collection rate allowing use in a routine industrial setting. Information from these measurements can aid in determining the rheological properties necessary for the end use functionality of a polymer. Additionally, AOTF instrumentation can be used