High-power, single-longitudinal-mode terahertz-wave generation pumped by a microchip Nd:YAG laser [Invited].

PubMed

Hayashi, Shin'ichiro; Nawata, Koji; Sakai, Hiroshi; Taira, Takunori; Minamide, Hiroaki; Kawase, Kodo

2012-01-30

We report on the development of a high-peak-power, single-longitudinal-mode and tunable injection-seeded terahertz-wave parametric generator using MgO:LiNbO3, which operates at room temperature. The high peak power (> 120 W) is enough to allow easy detection by commercial and calibrated pyroelectric detectors, and the spectral resolution (< 10 GHz) is the Fourier transform limit of the sub-nanosecond terahertz-wave pulse. The tunability (1.2-2.8 THz) and the small footprint size (A3 paper, 29.7 × 42 cm) are suitable for a variety of applications.

Understanding Charge Collection Mechanisms in InGaAs FinFETs Using High-Speed Pulsed-Laser Transient Testing With Tunable Wavelength

NASA Astrophysics Data System (ADS)

Ni, Kai; Sternberg, Andrew L.; Zhang, En Xia; Kozub, John A.; Jiang, Rong; Schrimpf, Ronald D.; Reed, Robert A.; Fleetwood, Daniel M.; Alles, Michael L.; McMorrow, Dale; Lin, Jianqiang; Vardi, Alon; del Alamo, Jesús

2017-08-01

A tunable wavelength laser system and high-resolution transient capture system are introduced to characterize transients in high-mobility MOSFETs. The experimental configuration enables resolution of fast transient signals and new understanding of charge collection mechanisms. The channel layer is critical in the charge collection process for the InGaAs FinFETs examined here. The transient current mainly comes from the channel current, due to shunt effects and parasitic bipolar effects, instead of the junction collection. The charge amplification factor is found to be as high as 14, which makes this technology relatively sensitive to transient radiation. The peak current is inversely proportional to the device gate length. Simulations show that the parasitic bipolar effect is due to source-to-channel barrier lowering caused by hole accumulation in the source and channel. Charge deposited in the channel causes prompt current, while charge deposited below the channel causes delayed and slow current.

New ultra-high resolution dye laser spectrometer utilizing a non-tunable reference resonator

NASA Astrophysics Data System (ADS)

Helmcke, J.; Snyder, J. J.; Morinaga, A.; Mensing, F.; Gläser, M.

1987-06-01

A new dye laser spectrometer utilizing a non-tunable reference resonator is described. The resonator consists of two Zerodur mirrors optically contacted to a Zerodur spacer. Frequency scanning of the laser is provided by acoustooptic modulation. Residual drifts of the resonator frequency — measured on line — are compensated automatically by corresponding corrections of the modulation frequency. The stability during several hours and the resettability of the dye laser frequency are±2.5 kHz and±10 kHz, respectively.

Tunable laser techniques for improving the precision of observational astronomy

NASA Astrophysics Data System (ADS)

Cramer, Claire E.; Brown, Steven W.; Lykke, Keith R.; Woodward, John T.; Bailey, Stephen; Schlegel, David J.; Bolton, Adam S.; Brownstein, Joel; Doherty, Peter E.; Stubbs, Christopher W.; Vaz, Amali; Szentgyorgyi, Andrew

2012-09-01

Improving the precision of observational astronomy requires not only new telescopes and instrumentation, but also advances in observing protocols, calibrations and data analysis. The Laser Applications Group at the National Institute of Standards and Technology in Gaithersburg, Maryland has been applying advances in detector metrology and tunable laser calibrations to problems in astronomy since 2007. Using similar measurement techniques, we have addressed a number of seemingly disparate issues: precision flux calibration for broad-band imaging, precision wavelength calibration for high-resolution spectroscopy, and precision PSF mapping for fiber spectrographs of any resolution. In each case, we rely on robust, commercially-available laboratory technology that is readily adapted to use at an observatory. In this paper, we give an overview of these techniques.

A 10 micron heterodyne receiver for ultra high resolution astronomical spectroscopy

NASA Technical Reports Server (NTRS)

Buhl, D.; Chin, G.; Faris, J.; Kostiuk, T.; Mumma, M. J.; Zipoy, D.

1980-01-01

An improved CO2 laser heterodyne spectrometer is examined. The present system uses reflective optics to eliminate refocusing at different wavelengths, and the local oscillator is a line-center-stabilized isotopic CO2 laser. A tunable diffraction grating makes possible easy and rapid selection of over 50 transitions per isotope of CO2. The IF (0 to 1.6 GHz) from the HgCdTe photomizer is analyzed by a 128-channel filter bank, consisting of 64 tunable 5-MHz filters and 64 fixed 25-MHz RF filters. These filters provide resolving powers of about 1,000,000 to 10,000,000 and velocity resolution of 50 to 250 m/sec; their output is synchronously detected, integrated, multiplexed and stored in a buffer memory for the desired integration period. Kitt Peak observations show the wide spectral coverage, wide mixer and electronics bandwidth, and high sensitivity of the system.

High resolution reversible color images on photonic crystal substrates.

PubMed

Kang, Pilgyu; Ogunbo, Samuel O; Erickson, David

2011-08-16

When light is incident on a crystalline structure with appropriate periodicity, some colors will be preferentially reflected (Joannopoulos, J. D.; Meade, R. D.; Winn, J. N. Photonic crystals: molding the flow of light; Princeton University Press: Princeton, NJ, 1995; p ix, 137 pp). These photonic crystals and the structural color they generate represent an interesting method for creating reflective displays and drawing devices, since they can achieve a continuous color response and do not require back lighting (Joannopoulos, J. D.; Villeneuve, P. R.; Fan, S. H. Photonic crystals: Putting a new twist on light. Nature 1997, 386, 143-149; Graham-Rowe, D. Tunable structural colour. Nat. Photonics 2009, 3, 551-553.; Arsenault, A. C.; Puzzo, D. P.; Manners, I.; Ozin, G. A. Photonic-crystal full-colour displays. Nat. Photonics 2007, 1, 468-472; Walish, J. J.; Kang, Y.; Mickiewicz, R. A.; Thomas, E. L. Bioinspired Electrochemically Tunable Block Copolymer Full Color Pixels. Adv. Mater.2009, 21, 3078). Here we demonstrate a technique for creating erasable, high-resolution, color images using otherwise transparent inks on self-assembled photonic crystal substrates (Fudouzi, H.; Xia, Y. N. Colloidal crystals with tunable colors and their use as photonic papers. Langmuir 2003, 19, 9653-9660). Using inkjet printing, we show the ability to infuse fine droplets of silicone oils into the crystal, locally swelling it and changing the reflected color (Sirringhaus, H.; Kawase, T.; Friend, R. H.; Shimoda, T.; Inbasekaran, M.; Wu, W.; Woo, E. P. High-resolution inkjet printing of all-polymer transistor circuits. Science 2000, 290, 2123-2126). Multicolor images with resolutions as high as 200 μm are obtained from oils of different molecular weights with the lighter oils being able to penetrate deeper, yielding larger red shifts. Erasing of images is done simply by adding a low vapor pressure oil which dissolves the image, returning the substrate to its original state.

HEKATE-A novel grazing incidence neutron scattering concept for the European Spallation Source.

PubMed

Glavic, Artur; Stahn, Jochen

2018-03-01

Structure and magnetism at surfaces and buried interfaces on the nanoscale can only be accessed by few techniques, one of which is grazing incidence neutron scattering. While the technique has its strongest limitation in a low signal and large background, due to the low scattering probability and need for high resolution, it can be expected that the high intensity of the European Spallation Source in Lund, Sweden, will make many more such studies possible, warranting a dedicated beamline for this technique. We present an instrument concept, Highly Extended K range And Tunable Experiment (HEKATE), for surface scattering that combines the advantages of two Selene neutron guides with unique capabilities of spatially separated distinct wavelength frames. With this combination, it is not only possible to measure large specular reflectometry ranges, even on free liquid surfaces, but also to use two independent incident beams with tunable sizes and resolutions that can be optimized for the specifics of the investigated samples. Further the instrument guide geometry is tuned for reduction of high energy particle background and only uses low to moderate supermirror coatings for high reliability and affordable cost.

HEKATE—A novel grazing incidence neutron scattering concept for the European Spallation Source

NASA Astrophysics Data System (ADS)

Glavic, Artur; Stahn, Jochen

2018-03-01

Structure and magnetism at surfaces and buried interfaces on the nanoscale can only be accessed by few techniques, one of which is grazing incidence neutron scattering. While the technique has its strongest limitation in a low signal and large background, due to the low scattering probability and need for high resolution, it can be expected that the high intensity of the European Spallation Source in Lund, Sweden, will make many more such studies possible, warranting a dedicated beamline for this technique. We present an instrument concept, Highly Extended K range And Tunable Experiment (HEKATE), for surface scattering that combines the advantages of two Selene neutron guides with unique capabilities of spatially separated distinct wavelength frames. With this combination, it is not only possible to measure large specular reflectometry ranges, even on free liquid surfaces, but also to use two independent incident beams with tunable sizes and resolutions that can be optimized for the specifics of the investigated samples. Further the instrument guide geometry is tuned for reduction of high energy particle background and only uses low to moderate supermirror coatings for high reliability and affordable cost.

A sensitivity analysis of cloud properties to CLUBB parameters in the single-column Community Atmosphere Model (SCAM5)

DOE PAGES

Guo, Zhun; Wang, Minghuai; Qian, Yun; ...

2014-08-13

In this study, we investigate the sensitivity of simulated shallow cumulus and stratocumulus clouds to selected tunable parameters of Cloud Layers Unified by Binormals (CLUBB) in the single column version of Community Atmosphere Model version 5 (SCAM5). A quasi-Monte Carlo (QMC) sampling approach is adopted to effectively explore the high-dimensional parameter space and a generalized linear model is adopted to study the responses of simulated cloud fields to tunable parameters. One stratocumulus and two shallow convection cases are configured at both coarse and fine vertical resolutions in this study.. Our results show that most of the variance in simulated cloudmore » fields can be explained by a small number of tunable parameters. The parameters related to Newtonian and buoyancy-damping terms of total water flux are found to be the most influential parameters for stratocumulus. For shallow cumulus, the most influential parameters are those related to skewness of vertical velocity, reflecting the strong coupling between cloud properties and dynamics in this regime. The influential parameters in the stratocumulus case are sensitive to the choice of the vertical resolution while little sensitivity is found for the shallow convection cases, as eddy mixing length (or dissipation time scale) plays a more important role and depends more strongly on the vertical resolution in stratocumulus than in shallow convections. The influential parameters remain almost unchanged when the number of tunable parameters increases from 16 to 35. This study improves understanding of the CLUBB behavior associated with parameter uncertainties.« less

Widely tunable (PbSn)Te lasers using etched cavities for mass production. [for infrared spectroscopic applications

NASA Technical Reports Server (NTRS)

Miller, M. D.

1980-01-01

Lead salt diode lasers are being used increasingly as tunable sources of monochromatic infrared radiation in a variety of spectroscopic systems. These devices are particularly useful, both in the laboratory and in the field, because of their high spectral brightness (compared to thermal sources) and wide spectral coverage (compared to line-tunable gas lasers). While the primary commercial application of these lasers has been for ultrahigh resolution laboratory spectroscopy, there are numerous systems applications, including laser absorbtion pollution monitors and laser heterodyne radiometers, for which diode lasers have great potential utility. Problem areas related to the wider use of these components are identified. Among these are total tuning range, mode control, and high fabrication cost. A fabrication technique which specifically addresses the problems of tuning range and cost, and which also has potential application for mode control, is reported.

High Spectral Resolution Lidar Measurements Using an I2 Absorption Filter

NASA Technical Reports Server (NTRS)

Eloranta, E. W.; Piironen, P.

1996-01-01

The University of Wisconsin high spectral resolution lidar (HSRL) measures optical properties of the atmosphere by separating the Doppler-broadened molecular backscatter return from the unbroadened aerosol return. The HSRL was modified to use an I2 absorption cell The modified HSRL transmitter uses a continuously pumped, Q-switched, injection seeded, frequency doubled Nd:YAG laser operating at a 4 kHz pulse repetition rate. This laser is tunable over a 124 GHz frequency range by temperature tuning the seed laser under computer control.

Optoelectronic frequency discriminated phase tuning technology and its applications

NASA Astrophysics Data System (ADS)

Lin, Gong-Ru; Chang, Yung-Cheng

2000-07-01

By using a phase-tunable optoelectronic phase-locked loop, we are able to continuously change the phase as well as the delay-time of optically distributed microwave clock signals or optical pulse train. The advantages of the proposed technique include such as wide-band operation up to 20GHz, wide-range tuning up to 640 degrees, high tuning resolution of <6x10-2 degree/mV, ultra-low short-term phase fluctuation and drive of 4.7x10-2 degree and 3.4x10- 3 degree/min, good linearity with acceptable deviations, and frequency-independent transferred function with slope of nearly 90 degrees/volt, etc. The novel optoelectronic phase shifter is performed by using a DC-voltage controlled, optoelectronic-mixer-based, frequency-down-converted digital phase-locked-loop. The maximum delay-time is continuously tunable up to 3.9 ns for optical pulses repeated at 500 MHz from a gain-switched laser diode. This corresponds to a delay responsivity of about 0.54 ps/mV. The using of the OEPS as being an optoelectronic delay-time controller for optical pulses is demonstrated with temporal resolution of <0.2 ps. Electro-optic sampling of high-frequency microwave signals by using the in-situ delay-time-tunable pulsed laser as a novel optical probe is primarily reported.

Trace gas absorption spectroscopy using laser difference-frequency spectrometer for environmental application

NASA Technical Reports Server (NTRS)

Chen, W.; Cazier, F.; Boucher, D.; Tittel, F. K.; Davies, P. B.

2001-01-01

A widely tunable infrared spectrometer based on difference frequency generation (DFG) has been developed for organic trace gas detection by laser absorption spectroscopy. On-line measurements of concentration of various hydrocarbons, such as acetylene, benzene, and ethylene, were investigated using high-resolution DFG trace gas spectroscopy for highly sensitive detection.

Photonic instantaneous frequency measurement of wideband microwave signals.

PubMed

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

2017-01-01

We propose a photonic system for instantaneous frequency measurement (IFM) of wideband microwave signals with a tunable measurement range and resolution based on a polarization-maintaining fiber Bragg grating (PM-FBG). Firstly, in order to be insensitive to laser power fluctuation, we aim at generating two different frequency to amplitude characteristics so that we can normalize them to obtain an amplitude comparison function (ACF). Then we encode these two different wavelengths in two perpendicular polarizations by using the PM-FBG which shows different transmission profiles at two polarizations. The ACF is capable of being adjusted by tuning polarization angle, therefore the measurement range and resolution are tunable. By theoretical analyses and simulated verification, a frequency measurement range of 0~17.2 GHz with average resolution of ±0.12 GHz can be achieved, which signifies a wide measurement range with relatively high resolution. Our system does not require large optical bandwidth for the components because the wavelength spacing can be small, making the system affordable, stable, and reliable with more consistent characteristics due to the narrowband nature of the optical parts. PM-FBG with high integration can be potentially used for more polarization manipulating systems and the use of a single-polarization dual-wavelength laser can simplify the architecture and enhance the stability.

Versatile Miniature Tunable Liquid Lenses Using Transparent Graphene Electrodes.

PubMed

Shahini, Ali; Xia, Jinjun; Zhou, Zhixian; Zhao, Yang; Cheng, Mark Ming-Cheng

2016-02-16

This paper presents, for the first time, versatile and low-cost miniature liquid lenses with graphene as electrodes. Tunable focal length is achieved by changing the droplet curvature using electrowetting on dielectric (EWOD). Ionic liquid and KCl solution are utilized as lens liquid on the top of a flexible Teflon-coated PDMS/parylene membrane. Transparent and flexible, graphene allows transmission of visible light as well as large deformation of the polymer membrane to achieve requirements for different lens designs and to increase the field of view without damaging of electrodes. The tunable range for the focal length is between 3 and 7 mm for a droplet with a volume of 3 μL. The visualization of bone marrow dendritic cells is demonstrated by the liquid lens system with a high resolution (456 lp/mm).

Laser techniques for spectroscopy of core-excited atomic levels

NASA Technical Reports Server (NTRS)

Harris, S. E.; Young, J. F.; Falcone, R. W.; Rothenberg, J. E.; Willison, J. R.

1982-01-01

We discuss three techniques which allow the use of tunable lasers for high resolution and picosecond time scale spectroscopy of core-excited atomic levels. These are: anti-Stokes absorption spectroscopy, laser induced emission from metastable levels, and laser designation of selected core-excited levels.

Spectrum Analyzers Incorporating Tunable WGM Resonators

NASA Technical Reports Server (NTRS)

Savchenkov, Anatoliy; Matsko, Andrey; Strekalov, Dmitry; Maleki, Lute

2009-01-01

A photonic instrument is proposed to boost the resolution for ultraviolet/ optical/infrared spectral analysis and spectral imaging allowing the detection of narrow (0.00007-to-0.07-picometer wavelength resolution range) optical spectral signatures of chemical elements in space and planetary atmospheres. The idea underlying the proposal is to exploit the advantageous spectral characteristics of whispering-gallery-mode (WGM) resonators to obtain spectral resolutions at least three orders of magnitude greater than those of optical spectrum analyzers now in use. Such high resolutions would enable measurement of spectral features that could not be resolved by prior instruments.

High accuracy demodulation for twin-grating based sensor network with hybrid TDM/FDM

NASA Astrophysics Data System (ADS)

Ai, Fan; Sun, Qizhen; Cheng, Jianwei; Luo, Yiyang; Yan, Zhijun; Liu, Deming

2017-04-01

We demonstrate a high accuracy demodulation platform with a tunable Fabry-Perot filter (TFF) for twin-grating based fiber optic sensing network with hybrid TDM/FDM. The hybrid TDM/FDM scheme can improve the spatial resolution to centimeter but increases the requirement of high spectrum resolution. To realize the demodulation of the complex twin-grating spectrum, we adopt the TFF demodulation method and compensate the environmental temperature change and nonlinear effect through calibration FBGs. The performance of the demodulation module is tested by a temperature experiment. Spectrum resolution of 1pm is realized with precision of 2.5pm while the environmental temperature of TFF changes 9.3°C.

Qubit Architecture with High Coherence and Fast Tunable Coupling.

PubMed

Chen, Yu; Neill, C; Roushan, P; Leung, N; Fang, M; Barends, R; Kelly, J; Campbell, B; Chen, Z; Chiaro, B; Dunsworth, A; Jeffrey, E; Megrant, A; Mutus, J Y; O'Malley, P J J; Quintana, C M; Sank, D; Vainsencher, A; Wenner, J; White, T C; Geller, Michael R; Cleland, A N; Martinis, John M

2014-11-28

We introduce a superconducting qubit architecture that combines high-coherence qubits and tunable qubit-qubit coupling. With the ability to set the coupling to zero, we demonstrate that this architecture is protected from the frequency crowding problems that arise from fixed coupling. More importantly, the coupling can be tuned dynamically with nanosecond resolution, making this architecture a versatile platform with applications ranging from quantum logic gates to quantum simulation. We illustrate the advantages of dynamical coupling by implementing a novel adiabatic controlled-z gate, with a speed approaching that of single-qubit gates. Integrating coherence and scalable control, the introduced qubit architecture provides a promising path towards large-scale quantum computation and simulation.

A novel fiber Bragg grating wavelength demodulation system based on F-P etalon

NASA Astrophysics Data System (ADS)

Yang, Gang; Guo, Jinghong; Xu, Guoliang; Lv, Lidong; Tu, Guojie; Xia, Lan

2014-10-01

This paper designs and implies a high precision FBG demodulation system which based on F-P etalon. In order to reduce the influence of the temperature drift effect, the peristaltic effect, and the nonlinear effect of F-P filter in traditional tunable filter method, F-P etalon is added as dynamical calibration and wavelength reference. Meanwhile segmentation demodulation which uses ASE spectral characteristics is applied to achieve high accuracy of the center wavelength of FBG. The experiment shows that the stability, resolution are 0.65pm, 0.23pm, respectively. Key words: fiber optics; fiber Bragg grating sensor system; tunable Fabry-Perot filter; F-P etalon; spectrum segmentation demodulation

Development of a tunable filter for coronal polarimetry

NASA Astrophysics Data System (ADS)

Tomczyk, S.; Mathew, S. K.; Gallagher, D.

2016-07-01

Measuring magnetic fields in the solar corona is crucial to understanding and predicting the Sun's generation of space weather that affects communications, GPS systems, space flight, and power transmission. The Coronal Solar Magnetism Observatory Large Coronagraph (COSMO LC) is a proposed 1.5 m aperture coronagraph designed to synoptically observe magnetic fields and plasma properties in the large-scale corona to improve our understanding of solar processes that cause space weather. The LC will observe coronal emission lines over the wavelength range from 500 to 1100 nm with a field of view of 1° and a spatial resolution of 2 arcsec. A spectral resolution greater than 8000 over the wavelength range is needed to resolve the polarization signatures of magnetic fields in the emission line profiles. The aperture and field of view of the LC set an étendue requirement of 1.39 m2 deg2 for the postfocus instrumentation. We find that a tunable wide-field birefringent filter using Lithium Niobate crystals can meet the étendue and spectral resolution requirements for the LC spectrometer. We have tested a number of commercially available crystals and verify that crystals of the required size and birefringence uniformity are available. We also evaluate electro-optical tuning of a Lithium Niobate birefringent filter by the application of high voltage. This tunable filter represents a key enabling technology for the COSMO LC.

Infrared heterodyne spectroscopy of atmospheric ozone

NASA Technical Reports Server (NTRS)

Frerking, M. A.; Muehlner, D. J.

1977-01-01

The absorption spectrum of atmospheric ozone is measured within a 1/cm region at 1100/cm, using an IR heterodyne detector (spectrometer with CO2 local oscillator) developed for astronomical work. Absorption spectra obtained by passing radiation from the tunable diode laser through an absorption cell, heterodyne spectra of atmospheric ozone, and a predicted atmospheric spectrum are compared. Water vapor absorbing in the region of interest (1100/cm) is also considered. Preliminary results encourage the use of diode laser local oscillators in tunable heterodyne detector systems for spectroscopy of atmospheric ozone and remote high-resolution spectroscopy of atmospheric constituents and pollutants.

Brewster-plate spoiler - A novel method for reducing the amplitude of interference fringes that limit tunable-laser absorption sensitivities

NASA Technical Reports Server (NTRS)

Webster, C. R.

1985-01-01

A simple method is described for substantially reducing the amplitude of interference fringes that limit the sensitivities of tunable-laser high-resolution absorption spectrometers. A lead-salt diode laser operating in the 7-micron region is used with a single Brewster-plate spoiler to reduce the fringe amplitude by a factor of 30 and also to allow the detection of absorptances 0.001 percent in a single laser scan without subtraction techniques, without complex frequency modulation, and without distortion of the molecular line-shape signals. Application to multipass-cell spectrometers is described.

Tunable all-optical quasimonochromatic thomson x-ray source in the nonlinear regime.

PubMed

Khrennikov, K; Wenz, J; Buck, A; Xu, J; Heigoldt, M; Veisz, L; Karsch, S

2015-05-15

We present an all-laser-driven, energy-tunable, and quasimonochromatic x-ray source based on Thomson scattering from laser-wakefield-accelerated electrons. One part of the laser beam was used to drive a few-fs bunch of quasimonoenergetic electrons, while the remainder was backscattered off the bunch at weakly relativistic intensity. When the electron energy was tuned from 17-50 MeV, narrow x-ray spectra peaking at 5-42 keV were recorded with high resolution, revealing nonlinear features. We present a large set of measurements showing the stability and practicality of our source.

Advanced RF and microwave functions based on an integrated optical frequency comb source.

PubMed

Xu, Xingyuan; Wu, Jiayang; Nguyen, Thach G; Shoeiby, Mehrdad; Chu, Sai T; Little, Brent E; Morandotti, Roberto; Mitchell, Arnan; Moss, David J

2018-02-05

We demonstrate advanced transversal radio frequency (RF) and microwave functions based on a Kerr optical comb source generated by an integrated micro-ring resonator. We achieve extremely high performance for an optical true time delay aimed at tunable phased array antenna applications, as well as reconfigurable microwave photonic filters. Our results agree well with theory. We show that our true time delay would yield a phased array antenna with features that include high angular resolution and a wide range of beam steering angles, while the microwave photonic filters feature high Q factors, wideband tunability, and highly reconfigurable filtering shapes. These results show that our approach is a competitive solution to implementing reconfigurable, high performance and potentially low cost RF and microwave signal processing functions for applications including radar and communication systems.

Hyperspectral retinal imaging with a spectrally tunable light source

NASA Astrophysics Data System (ADS)

Francis, Robert P.; Zuzak, Karel J.; Ufret-Vincenty, Rafael

2011-03-01

Hyperspectral retinal imaging can measure oxygenation and identify areas of ischemia in human patients, but the devices used by current researchers are inflexible in spatial and spectral resolution. We have developed a flexible research prototype consisting of a DLP®-based spectrally tunable light source coupled to a fundus camera to quickly explore the effects of spatial resolution, spectral resolution, and spectral range on hyperspectral imaging of the retina. The goal of this prototype is to (1) identify spectral and spatial regions of interest for early diagnosis of diseases such as glaucoma, age-related macular degeneration (AMD), and diabetic retinopathy (DR); and (2) define required specifications for commercial products. In this paper, we describe the challenges and advantages of using a spectrally tunable light source for hyperspectral retinal imaging, present clinical results of initial imaging sessions, and describe how this research can be leveraged into specifying a commercial product.

Spectrum synthesis for a spectrally tunable light source based on a DMD-convex grating Offner configuration

NASA Astrophysics Data System (ADS)

Ma, Suodong; Pan, Qiao; Shen, Weimin

2016-09-01

As one kind of light source simulation devices, spectrally tunable light sources are able to generate specific spectral shape and radiant intensity outputs according to different application requirements, which have urgent demands in many fields of the national economy and the national defense industry. Compared with the LED-type spectrally tunable light source, the one based on a DMD-convex grating Offner configuration has advantages of high spectral resolution, strong digital controllability, high spectrum synthesis accuracy, etc. As a key link of the above type light source to achieve target spectrum outputs, spectrum synthesis algorithm based on spectrum matching is therefore very important. An improved spectrum synthesis algorithm based on linear least square initialization and Levenberg-Marquardt iterative optimization is proposed in this paper on the basis of in-depth study of the spectrum matching principle. The effectiveness of the proposed method is verified by a series of simulations and experimental works.

Heterodyne spectrophotometry of ozone in the 9.6-micron band using a tunable diode laser

NASA Technical Reports Server (NTRS)

Mcelroy, C. T.; Goldman, A.; Fogal, P. F.; Murcray, D. G.

1990-01-01

Tunable diode laser heterodyne spectrophotometry (TDLHS) has been used to make extremely high resolution (0.0003/cm) solar spectra in the 9.6-micron ozone band. Observations have shown that a signal-to-noise ratio of 120:1 (about 30 percent of theoretical) for an integration time of 1/8 s can be achieved at a resolution of 0.0013 wave numbers. The spectral data have been inverted to yield a total column amount of ozone, in good agreement with that measured at the nearby NOAA ozone monitoring facility in Boulder, Colorado. Line positions for several ozone lines in the spectral region 996-997/cm are reported. Recent improvements have produced a signal-to-noise ratio of 95:1 (about 40 percent of theoretical) at 0.0003/cm and extended the range of wavelengths which can be observed.

3D-NTT: a versatile integral field spectro-imager for the NTT

NASA Astrophysics Data System (ADS)

Marcelin, M.; Amram, P.; Balard, P.; Balkowski, C.; Boissin, O.; Boulesteix, J.; Carignan, C.; Daigle, O.; de Denus Baillargeon, M.-M.; Epinat, B.; Gach, J.-L.; Hernandez, O.; Rigaud, F.; Vallée, P.

2008-07-01

The 3D-NTT is a visible integral field spectro-imager offering two modes. A low resolution mode (R ~ 300 to 6 000) with a large field of view Tunable Filter (17'x17') and a high resolution mode (R ~ 10 000 to 40 000) with a scanning Fabry-Perot (7'x7'). It will be operated as a visitor instrument on the NTT from 2009. Two large programmes will be led: "Characterizing the interstellar medium of nearby galaxies with 2D maps of extinction and abundances" (PI M. Marcelin) and "Gas accretion and radiative feedback in the early universe" (PI J. Bland Hawthorn). Both will be mainly based on the Tunable Filter mode. This instrument is being built as a collaborative effort between LAM (Marseille), GEPI (Paris) and LAE (Montreal). The website adress of the instrument is : http://www.astro.umontreal.ca/3DNTT

Tunable Emission Wavelength Stacked InAs/GaAs Quantum Dots by Chemical Beam Epitaxy for Optical Coherence Tomography

PubMed Central

Ilahi, Bouraoui; Zribi, Jihene; Guillotte, Maxime; Arès, Richard; Aimez, Vincent; Morris, Denis

2016-01-01

We report on Chemical Beam Epitaxy (CBE) growth of wavelength tunable InAs/GaAs quantum dots (QD) based superluminescent diode’s active layer suitable for Optical Coherence Tomography (OCT). The In-flush technique has been employed to fabricate QD with controllable heights, from 5 nm down to 2 nm, allowing a tunable emission band over 160 nm. The emission wavelength blueshift has been ensured by reducing both dots’ height and composition. A structure containing four vertically stacked height-engineered QDs have been fabricated, showing a room temperature broad emission band centered at 1.1 µm. The buried QD layers remain insensitive to the In-flush process of the subsequent layers, testifying the reliability of the process for broadband light sources required for high axial resolution OCT imaging. PMID:28773633

Industrial integration of high coherence tunable VECSEL in the NIR and MIR

NASA Astrophysics Data System (ADS)

Denet, Stéphane; Chomet, Baptiste; Lecocq, Vincent; Ferrières, Laurence; Myara, Mikhaël.; Cerutti, Laurent; Sagnes, Isabelle; Garnache, Arnaud

2016-03-01

Laser technology is finding applications in areas such as high resolution spectroscopy, radar-lidar, velocimetry, or atomic clock where highly coherent tunable high power light sources are required. The Vertical External Cavity Surface Emitting Laser (VECSEL) technology [1] has been identified for years as a good candidate to reach high power, high coherence and broad tunability while covering a wide emission wavelength range exploiting III-V semiconductor technologies. Offering such performances in the Near- and Middle-IR range, GaAs- and Sb-based VECSEL technologies seem to be a well suited path to meet the required specifications of demanding applications. Built up in this field, our expertise allows the realization of compact and low power consumption marketable products, with performances that do not exist on the market today in the 0.8- 1.1 μm and 2-2.5 μm spectral range. Here we demonstrate highly coherent broadly tunable single frequency micro-chip, intracavity element free, patented VECSEL technology, integrated into a compact module with driving electronics. VECSEL devices emitting in the Near and Middle-IR developed in the frame of this work [2] exhibit exciting features compared to diode-pumped solid-state lasers and DFB diode lasers; they combine high power (>100mW) high coherence with a low divergence diffraction limited TEM00 beam, class A dynamics with Relative Intensity Noise as low as -140dB/Hz and at shot noise level above 200MHz RF frequency (up to 160GHz), free running narrow linewidth at sub MHz level (fundamental limit at Hz level) with high spectral purity (SMSR >55dB), linear polarization (50dB suppression ratio), and broadband continuous tunability greater than 400GHz (< 30V piezo voltage, 6kHz cut off frequency) with total tunability up to 3THz. Those performances can all be reached thanks to the high finesse cavity of VECSEL technology, associated to ideal homogeneous QW gain behaviour [3]. In addition, the compact design without any movable intracavity elements offers a robust single frequency regime with a long term wavelength stability better than few GHz/h (ambient thermal drift limited). Those devices surpass the state of the art commercial technologies thanks to a combination of power-coherence wavelength tunability performances and integration.

A new way of controlling NesCOPOs (nested cavity doubly resonant OPO) for faster and more efficient high resolution spectrum measurement

NASA Astrophysics Data System (ADS)

Georges des Aulnois, Johann; Szymanski, Benjamin; Grimieau, Axel; Sillard, Léo.

2018-02-01

Optical Parametric Oscillator (OPO) is a well-known solution when wide tunability in the mid-infrared is needed. A specific design called NesCOPO (Nested Cavity doubly resonant OPO) is currently integrated in the X-FLR8 portable gas analyzer from Blue Industry and Science. Thanks to its low threshold this OPO can be pumped by a micro-chip nanosecond YAG (4 kHz repetition rate and a 30 GHz bandwidth). To achieve very high resolution spectra (10 pm of resolution or better), the emitted wavelength has to be finely controlled. Commercial Wavemeter do not meet price and compactness required in the context of an affordable and portable gas analyzer. To overcome this issue, Blue first integrated an active wavelength controller using multiple tunable Fabry-Perot (FP) interferometers. The required resolution was achieved at a 10 Hz measurement rate. We now present an enhanced Wavemeter architecture, based on fixed FP etalons, that is 100 times faster and 2 times smaller. We avoid having FP `blind zones' thanks to one source characteristic: the knowledge of the FSR (Free Spectral Range) of the OPO source and thus, the fact that only discrete wavelengths can be emitted. First results are displayed showing faster measurement for spectroscopic application, and potential future improvement of the device are discussed.

High-Performance Organic Vertical Thin Film Transistor Using Graphene as a Tunable Contact.

PubMed

Liu, Yuan; Zhou, Hailong; Weiss, Nathan O; Huang, Yu; Duan, Xiangfeng

2015-11-24

Here we present a general strategy for the fabrication of high-performance organic vertical thin film transistors (OVTFTs) based on the heterostructure of graphene and different organic semiconductor thin films. Utilizing the unique tunable work function of graphene, we show that the vertical carrier transport across the graphene-organic semiconductor junction can be effectively modulated to achieve an ON/OFF ratio greater than 10(3). Importantly, with the OVTFT design, the channel length is determined by the organic thin film thickness rather than by lithographic resolution. It can thus readily enable transistors with ultrashort channel lengths (<200 nm) to afford a delivering current greatly exceeding that of conventional planar TFTs, thus enabling a respectable operation frequency (up to 0.4 MHz) while using low-mobility organic semiconductors and low-resolution lithography. With this vertical device architecture, the entire organic channel is sandwiched and naturally protected between the source and drain electrodes, which function as the self-passivation layer to ensure stable operation of both p- and n-type OVTFTs in ambient conditions and enable complementary circuits with voltage gain. The creation of high-performance and highly robust OVTFTs can open up exciting opportunities in large-area organic macroelectronics.

Reflectance confocal microscopy of oral epithelial tissue using an electrically tunable lens

NASA Astrophysics Data System (ADS)

Jabbour, Joey M.; Malik, Bilal H.; Cuenca, Rodrigo; Cheng, Shuna; Jo, Javier A.; Cheng, Yi-Shing L.; Wright, John M.; Maitland, Kristen C.

2014-02-01

We present the use of a commercially available electrically tunable lens to achieve axial scanning in a reflectance confocal microscope. Over a 255 μm axial scan range, the lateral and axial resolutions varied from 1-2 μm and 4-14 μm, respectively, dependent on the variable focal length of the tunable lens. Confocal imaging was performed on normal human biopsies from the oral cavity ex vivo. Sub-cellular morphologic features were seen throughout the depth of the epithelium while axially scanning using the focus tunable lens.

Chromatic aberrations correction for imaging spectrometer based on acousto-optic tunable filter with two transducers.

PubMed

Zhao, Huijie; Wang, Ziye; Jia, Guorui; Zhang, Ying; Xu, Zefu

2017-10-02

The acousto-optic tunable filter (AOTF) with wide wavelength range and high spectral resolution has long crystal and two transducers. A longer crystal length leads to a bigger chromatic focal shift and the double-transducer arrangement induces angular mutation in diffracted beam, which increase difficulty in longitudinal and lateral chromatic aberration correction respectively. In this study, the two chromatic aberrations are analyzed quantitatively based on an AOTF optical model and a novel catadioptric dual-path configuration is proposed to correct both the chromatic aberrations. The test results exhibit effectiveness of the optical configuration for this type of AOTF-based imaging spectrometer.

Infrared absorption nano-spectroscopy using sample photoexpansion induced by tunable quantum cascade lasers.

PubMed

Lu, Feng; Belkin, Mikhail A

2011-10-10

We report a simple technique that allows obtaining mid-infrared absorption spectra with nanoscale spatial resolution under low-power illumination from tunable quantum cascade lasers. Light absorption is detected by measuring associated sample thermal expansion with an atomic force microscope. To detect minute thermal expansion we tune the repetition frequency of laser pulses in resonance with the mechanical frequency of the atomic force microscope cantilever. Spatial resolution of better than 50 nm is experimentally demonstrated.

Polarization-independent actively tunable colour generation on imprinted plasmonic surfaces

PubMed Central

Franklin, Daniel; Chen, Yuan; Vazquez-Guardado, Abraham; Modak, Sushrut; Boroumand, Javaneh; Xu, Daming; Wu, Shin-Tson; Chanda, Debashis

2015-01-01

Structural colour arising from nanostructured metallic surfaces offers many benefits compared to conventional pigmentation based display technologies, such as increased resolution and scalability of their optical response with structure dimensions. However, once these structures are fabricated their optical characteristics remain static, limiting their potential application. Here, by using a specially designed nanostructured plasmonic surface in conjunction with high birefringence liquid crystals, we demonstrate a tunable polarization-independent reflective surface where the colour of the surface is changed as a function of applied voltage. A large range of colour tunability is achieved over previous reports by utilizing an engineered surface which allows full liquid crystal reorientation while maximizing the overlap between plasmonic fields and liquid crystal. In combination with imprinted structures of varying periods, a full range of colours spanning the entire visible spectrum is achieved, paving the way towards dynamic pixels for reflective displays. PMID:26066375

Tunable room temperature THz sources based on nonlinear mixing in a hybrid optical and THz micro-ring resonator.

PubMed

Sinha, Raju; Karabiyik, Mustafa; Al-Amin, Chowdhury; Vabbina, Phani K; Güney, Durdu Ö; Pala, Nezih

2015-03-24

We propose and systematically investigate a novel tunable, compact room temperature terahertz (THz) source based on difference frequency generation in a hybrid optical and THz micro-ring resonator. We describe detailed design steps of the source capable of generating THz wave in 0.5-10 THz with a tunability resolution of 0.05 THz by using high second order optical susceptibility (χ((2))) in crystals and polymers. In order to enhance THz generation compared to bulk nonlinear material, we employ a nonlinear optical micro-ring resonator with high-Q resonant modes for infrared input waves. Another ring oscillator with the same outer radius underneath the nonlinear ring with an insulation of SiO2 layer supports the generated THz with resonant modes and out-couples them into a THz waveguide. The phase matching condition is satisfied by engineering both the optical and THz resonators with appropriate effective indices. We analytically estimate THz output power of the device by using practical values of susceptibility in available crystals and polymers. The proposed source can enable tunable, compact THz emitters, on-chip integrated spectrometers, inspire a broader use of THz sources and motivate many important potential THz applications in different fields.

Tunable Room Temperature THz Sources Based on Nonlinear Mixing in a Hybrid Optical and THz Micro-Ring Resonator

PubMed Central

Sinha, Raju; Karabiyik, Mustafa; Al-Amin, Chowdhury; Vabbina, Phani K.; Güney, Durdu Ö.; Pala, Nezih

2015-01-01

We propose and systematically investigate a novel tunable, compact room temperature terahertz (THz) source based on difference frequency generation in a hybrid optical and THz micro-ring resonator. We describe detailed design steps of the source capable of generating THz wave in 0.5–10 THz with a tunability resolution of 0.05 THz by using high second order optical susceptibility (χ(2)) in crystals and polymers. In order to enhance THz generation compared to bulk nonlinear material, we employ a nonlinear optical micro-ring resonator with high-Q resonant modes for infrared input waves. Another ring oscillator with the same outer radius underneath the nonlinear ring with an insulation of SiO2 layer supports the generated THz with resonant modes and out-couples them into a THz waveguide. The phase matching condition is satisfied by engineering both the optical and THz resonators with appropriate effective indices. We analytically estimate THz output power of the device by using practical values of susceptibility in available crystals and polymers. The proposed source can enable tunable, compact THz emitters, on-chip integrated spectrometers, inspire a broader use of THz sources and motivate many important potential THz applications in different fields. PMID:25800287

An off Axis Cavity Enhanced Absorption Spectrometer and a Rapid Scan Spectrometer with a Room-Temperature External Cavity Quantum Cascade Laser

NASA Astrophysics Data System (ADS)

Liu, Xunchen; Kang, Cheolhwa; Xu, Yunjie

2009-06-01

Quantum cascade laser (QCL) is a new type of mid-infrared tunable diode lasers with superior output power and mode quality. Recent developments, such as room temperature operation, wide frequency tunability, and narrow line width, make QCLs an ideal light source for high resolution spectroscopy. Two slit jet infrared spectrometers, namely an off-axis cavity enhanced absorption (CEA) spectrometer and a rapid scan spectrometer with an astigmatic multi-pass cell assembly, have been coupled with a newly purchased room temperature tunable mod-hop-free QCL with a frequency coverage from 1592 cm^{-1} to 1698 cm^{-1} and a scan rate of 0.1 cm^{-1}/ms. Our aim is to utilize these two sensitive spectrometers, that are equipped with a molecular jet expansion, to investigate the chiral molecules-(water)_n clusters. To demonstrate the resolution and sensitivity achieved, the rovibrational transitions of the static N_2O gas and the bending rovibrational transitions of the Ar-water complex, a test system, at 1634 cm^{-1} have been measured. D. Hofstetter and J. Faist in High performance quantum cascade lasers and their applications, Vol.89 Springer-Verlag Berlin & Heidelberg, 2003, pp. 61-98. Y. Xu, X. Liu, Z. Su, R. M. Kulkarni, W. S. Tam, C. Kang, I. Leonov and L. D'Agostino, Proc. Spie, 2009, 722208 (1-11). M. J. Weida and D. J. Nesbitt, J. Chem. Phys. 1997, 106, 3078-3089.

High-resolution differential mode delay measurement for a multimode optical fiber using a modified optical frequency domain reflectometer.

PubMed

Ahn, T-J; Kim, D

2005-10-03

A novel differential mode delay (DMD) measurement technique for a multimode optical fiber based on optical frequency domain reflectometry (OFDR) has been proposed. We have obtained a high-resolution DMD value of 0.054 ps/m for a commercial multimode optical fiber with length of 50 m by using a modified OFDR in a Mach-Zehnder interferometer structure with a tunable external cavity laser and a Mach-Zehnder interferometer instead of Michelson interferometer. We have also compared the OFDR measurement results with those obtained using a traditional time-domain measurement method. DMD resolution with our proposed OFDR technique is more than an order of magnitude better than a result obtainable with a conventional time-domain method.

Industrial integration of high coherence tunable single frequency semiconductor lasers based on VECSEL technology for scientific instrumentation in NIR and MIR

NASA Astrophysics Data System (ADS)

Lecocq, Vincent; Chomet, Baptiste; Ferrières, Laurence; Myara, Mikhaël.; Beaudoin, Grégoire; Sagnes, Isabelle; Cerutti, Laurent; Denet, Stéphane; Garnache, Arnaud

2017-02-01

Laser technology is finding applications in areas such as high resolution spectroscopy, radar-lidar, velocimetry, or atomic clock where highly coherent tunable high power light sources are required. The Vertical External Cavity Surface Emitting Laser (VECSEL) technology [1] has been identified for years as a good candidate to reach high power, high coherence and broad tunability while covering a wide emission wavelength range exploiting III-V semiconductor technologies. Offering such performances in the Near- and Middle-IR range, GaAs- and Sb-based VECSEL technologies seem to be a well suited path to meet the required specifications of demanding applications. Built up in this field, our expertise allows the realization of compact and low power consumption marketable products, with performances that do not exist on the market today in the 0.8-1.1 μm and 2-2.5 μm spectral range. Here we demonstrate highly coherent broadly tunable single frequency laser micro-chip, intracavity element free, based on a patented VECSEL technology, integrated into a compact module with driving electronics. VECSEL devices emitting in the Near and Middle-IR developed in the frame of this work [2] exhibit exciting features compared to diode-pumped solid-state lasers and DFB diode lasers; they combine high power (>100mW) high temporal coherence together with a low divergence diffraction limited TEM00 beam. They exhibit a class-A dynamics with a Relative Intensity Noise as low as -140dB/Hz and at shot noise level reached above 200MHz RF frequency (up to 160GHz), a free running narrow linewidth at sub MHz level (fundamental limit at Hz level) with high spectral purity (SMSR >55dB), a linear polarization (>50dB suppression ratio), and broadband continuous tunability greater than 400GHz (< 30V piezo voltage, 6kHz cut off frequency) with total tunability up to 3THz. Those performances can all be reached thanks to the high finesse cavity of VECSEL technology, associated to ideal homogeneous QW gain behaviour [3]. In addition, the compact design without any movable intracavity elements offers a robust single frequency regime with a long term wavelength stability better than few GHz/h (ambient thermal drift limited). Those devices surpass the state of the art commercial technologies thanks to a combination of power-coherence-wavelength tunability performances and integration.

Airborne Laser Infrared Absorption Spectrometer (ALIAS-II) for in situ Atmospheric Measurements of N(sub 2)0, CH(sub 4), CO, HCl, and NO(sub 2) from Balloon or RPA Platforms

NASA Technical Reports Server (NTRS)

Scott, D.; Herman, R.; Webster, C.; May, R.; Flesch, G.; Moyer, E.

1998-01-01

The Airborne Laser Infrared Absorption Spectrometer II (ALIAS-II) is a lightweight, high-resolution (0.0003 cm-1), scanning, mid-infrared absorption spectrometer based on cooled (80 K) lead-salt tunable diode laser sources.

Tunable laser heterodyne spectrometer measurements of atmospheric species

NASA Technical Reports Server (NTRS)

Allario, F.; Katzberg, S. J.; Hoell, J. M.

1983-01-01

It is pointed out that spectroscopic measurements conducted with the aid of tunable laser heterodyne spectrometers in the 3-30 micron range of the electromagnetic spectrum have the potential to measure the vertical profiles of tenuous gas molecules in the atmosphere with ultra high spectral resolution and great sensitivity. Programs related to the realization of this potential have been conducted for some time, and a Laser Heterodyne Spectrometer (LHS) experiment was developed. The present investigation has the objective to provide an overview of the LHS concept for measuring the vertical profiles of tenuous gas molecules in the upper atmosphere from space and airborne platforms, and to discuss the sensitivity ranges for this technique.

Tunable diode laser measurements of HO2NO2 absorption coefficients near 12.5 microns

NASA Technical Reports Server (NTRS)

May, R. D.; Molina, L. T.; Webster, C. R.

1988-01-01

A tunable diode laser spectrometer has been used to measure absorption coefficients of peroxynitric acid (HO2NO2) near the 803/cm Q branch. HO2NO2 concentrations in a low-pressure flowing gas mixture were determined from chemical titration procedures and UV absorption spectroscopy. The diode laser measured absorption coefficients, at a spectral resolution of better than 0.001/cm, are about 10 percent larger than previous Fourier transform infrared measurements made at a spectral resolution of 0.06/cm.

Solar CIV Vacuum-Ultraviolet Fabry-Perot Interferometers

NASA Technical Reports Server (NTRS)

Gary, G. Allen; West, Edward A.; Rees, David; McKay, Jack A.; Zukic, Maumer; Herman, Peter

2006-01-01

Aims: A tunable, high spectral resolution, high effective finesse, vacuum ultraviolet (VUV) Fabry-Perot interferometer (PPI) is designed for obtaining narrow-passband images, magnetograms, and Dopplergrams of the transition region emission line of CIV (155 nm). Methods: The integral part of the CIV narrow passband filter package (with a 2-10 pm FWHM) consists of a multiple etalon system composed of a tunable interferometer that provides high-spectral resolution and a static low-spectral resolution interferometer that allows a large effective free spectral range. The prefilter for the interferometers is provided by a set of four mirrors with dielectric high-reflective coatings. A tunable interferometer, a VUV piezoelectric-control etalon, has undergone testing using the surrogate F2 eximer laser line at 157 nm for the CIV line. We present the results of the tests with a description of the overall concept for a complete narrow-band CIV spectral filter. The static interferometer of the filter is envisioned as being hudt using a set of fixed MgF2 plates. The four-mirror prefilter is designed to have dielectric multilayer n-stacks employing the design concept used in the Ultraviolet Imager of NASA's Polar Spacecraft. A dual etalon system allows the effective free spectral range to be commensurate with the prefilter profile. With an additional etalon, a triple etalon system would allow a spectrographic resolution of 2 pm. The basic strategy has been to combine the expertise of spaceflight etalon manufacturing with VUV coating technology to build a VUV FPI which combines the best attributes of imagers and spectrographs into a single compact instrument. Results. Spectro-polarimetry observations of the transition region CIV emission can be performed to increase the understanding of the magnetic forces, mass motion, evolution, and energy release within the solar atmosphere at the base of the corona where most of the magnetic field is approximately force-free. The 2D imaging of the full vector magnetic field at the height of maximum magnetic influence (minimum plasma beta) can be accomplished, albeit difficult, by measuring the Zeeman splitting of the CIV resonance pair. Designs of multiple VUV FPIs can be developed for integration into future orbiting solar observatories to obtain rapid cadence, spectral imaging of the transition region.

Simultaneous interrogation of interferometric and Bragg grating sensors

NASA Astrophysics Data System (ADS)

Brady, G.; Kalli, K.; Webb, D. J.; Jackson, D. A.; Reekie, L.; Archambault, J. L.

1995-06-01

We propose a new method for the simultaneous interrogation of conventional two-beam interferometers and Bragg grating sensors. The technique employs an unbalanced Mach-Zehnder interferometer illuminated by a single low-coherence source, which acts as a wavelength-tunable source for the grating and as a path-matched filter for the Fizeau interferometer, thus providing a high phase resolution output for each sensor. The grating sensor demonstrates a dynamic strain resolution of \\similar 0.05 mu 3 / \\radical Hz \\end-radical at 20 Hz, while the interferometric phase resolution is better than 1mrad/ \\radical Hz \\end-radical at 20 Hz, corresponding to an rms mirror displacement of 0.08 nm.

Spontaneous Raman scattering as a high resolution XUV radiation source

NASA Technical Reports Server (NTRS)

Rothenberg, J. E.; Young, J. F.; Harris, S. E.

1983-01-01

A type of high resolution XUV radiation source is described which is based upon spontaneous anti-Stokes scattering of tunable incident laser radiation from atoms excited to metastable levels. The theory of the source is summarized and two sets of experiments using He (1s2s)(1)S atoms, produced in a cw hollow cathode and in a pulsed high power microwave discharge, are discussed. The radiation source is used to examine transitions originating from the 3p(6) shell of potassium. The observed features include four previously unreported absorption lines and several sharp interferences of closely spaced autoionizing lines. A source linewidth of about 1.9 cm(-1) at 185,000 cm(-1) is demonstrated.

High-brightness laser imaging with tunable speckle reduction enabled by electroactive micro-optic diffusers.

PubMed

Farrokhi, Hamid; Rohith, Thazhe Madam; Boonruangkan, Jeeranan; Han, Seunghwoi; Kim, Hyunwoong; Kim, Seung-Woo; Kim, Young-Jin

2017-11-10

High coherence of lasers is desirable in high-speed, high-resolution, and wide-field imaging. However, it also causes unavoidable background speckle noise thus degrades the image quality in traditional microscopy and more significantly in interferometric quantitative phase imaging (QPI). QPI utilizes optical interference for high-precision measurement of the optical properties where the speckle can severely distort the information. To overcome this, we demonstrated a light source system having a wide tunability in the spatial coherence over 43% by controlling the illumination angle, scatterer's size, and the rotational speed of an electroactive-polymer rotational micro-optic diffuser. Spatially random phase modulation was implemented for the lower speckle imaging with over a 50% speckle reduction without a significant degradation in the temporal coherence. Our coherence control technique will provide a unique solution for a low-speckle, full-field, and coherent imaging in optically scattering media in the fields of healthcare sciences, material sciences and high-precision engineering.

Infrared near-field spectroscopy of trace explosives using an external cavity quantum cascade laser.

PubMed

Craig, Ian M; Taubman, Matthew S; Lea, A Scott; Phillips, Mark C; Josberger, Erik E; Raschke, Markus B

2013-12-16

Utilizing a broadly-tunable external cavity quantum cascade laser for scattering-type scanning near-field optical microscopy (s-SNOM), we measure infrared spectra of particles of explosives by probing characteristic nitro-group resonances in the 7.1-7.9 µm wavelength range. Measurements are presented with spectral resolution of 0.25 cm(-1), spatial resolution of 25 nm, sensitivity better than 100 attomoles, and at a rapid acquisition time of 90 s per spectrum. We demonstrate high reproducibility of the acquired s-SNOM spectra with very high signal-to-noise ratios and relative noise of <0.02 in self-homodyne detection.

Two-dimensional fluorescence spectroscopy of uranium isotopes in femtosecond laser ablation plumes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Phillips, Mark C.; Brumfield, Brian E.; LaHaye, Nicole

Here, we demonstrate measurement of uranium isotopes in femtosecond laser ablation plumes using two-dimensional fluorescence spectroscopy (2DFS). The high-resolution, tunable CW-laser spectroscopy technique clearly distinguishes atomic absorption from 235U and 238U in natural and highly enriched uranium metal samples. We present analysis of spectral resolution and analytical performance of 2DFS as a function of ambient pressure. Simultaneous measurement using time-resolved absorption spectroscopy provides information on temporal dynamics of the laser ablation plume and saturation behavior of fluorescence signals. The rapid, non-contact measurement is promising for in-field, standoff measurements of uranium enrichment for nuclear safety and security.

Two-dimensional fluorescence spectroscopy of uranium isotopes in femtosecond laser ablation plumes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Phillips, Mark C.; Brumfield, Brian E.; LaHaye, Nicole L.

We demonstrate measurement of uranium isotopes in femtosecond laser ablation plumes using two-dimensional fluorescence spectroscopy (2DFS). The high-resolution, tunable CW-laser spectroscopy technique clearly distinguishes atomic absorption from 235U and 238U in natural and highly enriched uranium metal samples. We present analysis of spectral resolution and analytical performance of 2DFS as a function of ambient pressure. Simultaneous measurement using time-resolved absorption spectroscopy provides information on temporal dynamics of the laser ablation plume and saturation behavior of fluorescence signals. The rapid, non-contact measurement is promising for in-field, standoff measurements of uranium enrichment for nuclear safety and security applications.

Two-dimensional fluorescence spectroscopy of uranium isotopes in femtosecond laser ablation plumes

DOE PAGES

Phillips, Mark C.; Brumfield, Brian E.; LaHaye, Nicole; ...

2017-06-19

Here, we demonstrate measurement of uranium isotopes in femtosecond laser ablation plumes using two-dimensional fluorescence spectroscopy (2DFS). The high-resolution, tunable CW-laser spectroscopy technique clearly distinguishes atomic absorption from 235U and 238U in natural and highly enriched uranium metal samples. We present analysis of spectral resolution and analytical performance of 2DFS as a function of ambient pressure. Simultaneous measurement using time-resolved absorption spectroscopy provides information on temporal dynamics of the laser ablation plume and saturation behavior of fluorescence signals. The rapid, non-contact measurement is promising for in-field, standoff measurements of uranium enrichment for nuclear safety and security.

Solar vector magnetograph for Max 1991 programs

NASA Technical Reports Server (NTRS)

Rust, D. M.; Obyrne, J. W.; Harris, T. J.

1988-01-01

An instrument for measuring solar magnetic fields is under construction. Key requirements for any solar vector magnetograph are high spatial resolution, high optical throughput, fine spectral selectivity, and ultralow instrumental polarization. An available 25 cm Cassegrain telescope will provide 0.5 arcsec spatial resolution. Spectral selection will be accomplished with a 150 mA filter based on electrically tunable solid Fabry-Perot etalon. Filter and polarization analyzer design concepts for the magnetograph are described in detail. The instrument will be tested at JHU/APL, and then moved to the National Solar Observatory in late 1988. It will be available to support the Max 1991 program.

MEMS for Tunable Photonic Metamaterial Applications

NASA Astrophysics Data System (ADS)

Stark, Thomas

Photonic metamaterials are materials whose optical properties are derived from artificially-structured sub-wavelength unit cells, rather than from the bulk properties of the constituent materials. Examples of metamaterials include plasmonic materials, negative index materials, and electromagnetic cloaks. While advances in simulation tools and nanofabrication methods have allowed this field to grow over the past several decades, many challenges still exist. This thesis addresses two of these challenges: fabrication of photonic metamaterials with tunable responses and high-throughput nanofabrication methods for these materials. The design, fabrication, and optical characterization of a microelectromechanical systems (MEMS) tunable plasmonic spectrometer are presented. An array of holes in a gold film, with plasmon resonance in the mid-infrared, is suspended above a gold reflector, forming a Fabry-Perot interferometer of tunable length. The spectra exhibit the convolution of extraordinary optical transmission through the holes and Fabry-Perot resonances. Using MEMS, the interferometer length is modulated from 1.7 mum to 21.67 mum , thereby tuning the free spectral range from about 2900 wavenumbers to 230.7 wavenumbers and shifting the reflection minima and maxima across the infrared. Due to its broad spectral tunability in the fingerprint region of the mid-infrared, this device shows promise as a tunable biological sensing device. To address the issue of high-throughput, high-resolution fabrication of optical metamaterials, atomic calligraphy, a MEMS-based dynamic stencil lithography technique for resist-free fabrication of photonic metamaterials on unconventional substrates, has been developed. The MEMS consists of a moveable stencil, which can be actuated with nanometer precision using electrostatic comb drive actuators. A fabrication method and flip chip method have been developed, enabling evaporation of metals through the device handle for fabrication on an external substrate. While the MEMS can be used to fabricate over areas of approximately 100 square mum2, a piezoelectric step-and repeat system enables fabrication over cm length scales. Thus, this technique leverages the precision inherent to MEMS actuation, while enhancing nanofabrication thoughput. Fabricating metamaterials on new substrates will enable novel and tunable metamaterials. For example, by fabricating unit cells on a periodic auxetic mechanical scaffold, the optical properties can be tuned by straining the mechanical scaffold.

Hyperspectral proximal sensing of Salix Alba trees in the Sacco river valley (Latium, Italy).

PubMed

Moroni, Monica; Lupo, Emanuela; Cenedese, Antonio

2013-10-29

Recent developments in hardware and software have increased the possibilities and reduced the costs of hyperspectral proximal sensing. Through the analysis of high resolution spectroscopic measurements at the laboratory or field scales, this monitoring technique is suitable for quantitative estimates of biochemical and biophysical variables related to the physiological state of vegetation. Two systems for hyperspectral imaging have been designed and developed at DICEA-Sapienza University of Rome, one based on the use of spectrometers, the other on tunable interference filters. Both systems provide a high spectral and spatial resolution with low weight, power consumption and cost. This paper describes the set-up of the tunable filter platform and its application to the investigation of the environmental status of the region crossed by the Sacco river (Latium, Italy). This was achieved by analyzing the spectral response given by tree samples, with roots partly or wholly submerged in the river, located upstream and downstream of an industrial area affected by contamination. Data acquired is represented as reflectance indices as well as reflectance values. Broadband and narrowband indices based on pigment content and carotenoids vs. chlorophyll content suggest tree samples located upstream of the contaminated area are 'healthier' than those downstream.

An imaging vector magnetograph for the next solar maximum

NASA Technical Reports Server (NTRS)

Canfield, Richard C.; Mickey, Donald L.

1988-01-01

Measurements of the vector magnetic field in the solar atmosphere with high spatial and temporal resolution over a large field of view are critical to understanding the nature and evolution of currents in active regions. Such measurements, when combined with the thermal and nonthermal X-ray images from the upcoming Solar-A mission, will reveal the large-scale relationship between these currents and sites of heating and particle acceleration in flaring coronal magnetic flux tubes. The conceptual design of an imaging vector magnetograph that combines a modest solar telescope with a rotating quarter-wave plate, an acousto-optical tunable prefilter as a blocker for a servo-controlled Fabry-Perot etalon, CCD cameras, and a rapid digital tape recorder are described. Its high spatial resolution (1/2 arcsec pixel size) over a large field of view (4 x 5 arcmin) will be sufficient to significantly measure, for the first time, the magnetic energy dissipated in major solar flares. Its millisecond tunability and wide spectra range (5000 to 8000 A) enable nearly simultaneous vector magnetic field measurements in the gas-pressure-dominated photosphere and magnetically dominated chromosphere, as well as effective co-alignment with Solar-A's X-ray images.

[Application of mid-infrared wavelength tunable laser in glucose determination].

PubMed

Yu, Song-Lin; Li, Da-Chao; Zhong, Hao; Sun, Chang-Yue; Xu, Ke-Xin

2013-04-01

The authors proposed a method of control and stabilization for laser emission wavelengths and power, and presented the mid-infrared wavelength tunable laser with broad emission spectrum band of 9.19-9.77 microm, half wave width of 4 cm(-1), spectral resolution of 2.7 x 10(4) and max power of 800 mW with fluctuation < 0.8% in the present paper. The tunable laser was employed as the light source in combination with ATR sensor for glucose measurement in PBS solution. In our experiments, absorbance at the five laser emission wavelengths, including 1 081, 1 076, 1 051, 1 041 and 1 037 cm(-1) in the 9R and 9P band of the laser emission spectrum, all correlates well with the glucose concentration (R2 > 0.99, SD < 0.0004, P < 0.000 1). Especially, the sensitivity of this laser spectroscopy system is about 4 times as high as that of traditional FTIR spectrometer.

Development of thin-film tunable band-pass filters based hyper-spectral imaging system applied for both surface enhanced Raman scattering and plasmon resonance Rayleigh scattering

NASA Astrophysics Data System (ADS)

Iga, Mitsuhiro; Kakuryu, Nobuyuki; Tanaami, Takeo; Sajiki, Jiro; Isozaki, Katsumi; Itoh, Tamitake

2012-10-01

We describe the development of a hyper-spectral imaging (HSI) system composed of thin-film tunable band-pass filters (TF-TBPFs) and its application to inhomogeneous sample surfaces. Compared with existing HSI systems, the system has a simpler optical arrangement and has an optical transmittance of up to 80% owing to polarization independence. The HSI system exhibits a constant spectral resolution over a spectral window of 80 nm (530 to 610 nm) and tunable spectral resolution from 1.5 to 3.0 nm, and requires only 5.4 s per measurement. Plasmon resonance and surface enhanced Raman scattering (SERS) from inhomogeneous surfaces dispersed with Ag nanoparticles (NP) have been measured with the HSI system. The measurement of multiple Ag NPs is consistent with conventional isolated NP measurements as explained by the electromagnetic mechanism of SERS, demonstrating the validity of the HSI system.

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.

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.

Tunable single-longitudinal-mode operation of an injection-locked TEA CO2 laser. [ozone absorption spectroscopy

NASA Technical Reports Server (NTRS)

Megie, G.; Menzies, R. T.

1979-01-01

The tunable single-longitudinal-mode operation of a TEA CO2 laser by an injection technique using a CW waveguide laser as the master oscillator is reported. With the experimental arrangement described, in which the waveguide laser frequency is tuned to correspond to one of the oscillating longitudinal modes of the TEA laser, single-longitudinal-mode operation was achieved with no apparent reduction in the TEA output energy, on various CO2 lines with frequency offsets from the line center as large as 300 MHz. The capability of this technique for high-resolution spectroscopy or atmospheric lidar studies is demonstrated by the recording of the absorption spectrum of a strong ozone line.

Graphene based terahertz phase modulators

NASA Astrophysics Data System (ADS)

Kakenov, N.; Ergoktas, M. S.; Balci, O.; Kocabas, C.

2018-07-01

Electrical control of amplitude and phase of terahertz radiation (THz) is the key technological challenge for high resolution and noninvasive THz imaging. The lack of active materials and devices hinders the realization of these imaging systems. Here, we demonstrate an efficient terahertz phase and amplitude modulation using electrically tunable graphene devices. Our device structure consists of electrolyte-gated graphene placed at quarter wavelength distance from a reflecting metallic surface. In this geometry, graphene operates as a tunable impedance surface which yields electrically controlled reflection phase. Terahertz time domain reflection spectroscopy reveals the voltage controlled phase modulation of π and the reflection modulation of 50 dB. To show the promises of our approach, we demonstrate a multipixel phase modulator array which operates as a gradient impedance surface.

High-speed transport-of-intensity phase microscopy with an electrically tunable lens.

PubMed

Zuo, Chao; Chen, Qian; Qu, Weijuan; Asundi, Anand

2013-10-07

We present a high-speed transport-of-intensity equation (TIE) quantitative phase microscopy technique, named TL-TIE, by combining an electrically tunable lens with a conventional transmission microscope. This permits the specimen at different focus position to be imaged in rapid succession, with constant magnification and no physically moving parts. The simplified image stack collection significantly reduces the acquisition time, allows for the diffraction-limited through-focus intensity stack collection at 15 frames per second, making dynamic TIE phase imaging possible. The technique is demonstrated by profiling of microlens array using optimal frequency selection scheme, and time-lapse imaging of live breast cancer cells by inversion the defocused phase optical transfer function to correct the phase blurring in traditional TIE. Experimental results illustrate its outstanding capability of the technique for quantitative phase imaging, through a simple, non-interferometric, high-speed, high-resolution, and unwrapping-free approach with prosperous applications in micro-optics, life sciences and bio-photonics.

HPT: A High Spatial Resolution Multispectral Sensor for Microsatellite Remote Sensing

PubMed Central

Takahashi, Yukihiro; Sakamoto, Yuji; Kuwahara, Toshinori

2018-01-01

Although nano/microsatellites have great potential as remote sensing platforms, the spatial and spectral resolutions of an optical payload instrument are limited. In this study, a high spatial resolution multispectral sensor, the High-Precision Telescope (HPT), was developed for the RISING-2 microsatellite. The HPT has four image sensors: three in the visible region of the spectrum used for the composition of true color images, and a fourth in the near-infrared region, which employs liquid crystal tunable filter (LCTF) technology for wavelength scanning. Band-to-band image registration methods have also been developed for the HPT and implemented in the image processing procedure. The processed images were compared with other satellite images, and proven to be useful in various remote sensing applications. Thus, LCTF technology can be considered an innovative tool that is suitable for future multi/hyperspectral remote sensing by nano/microsatellites. PMID:29463022

Electrically optofluidic zoom system with a large zoom range and high-resolution image.

PubMed

Li, Lei; Yuan, Rong-Ying; Wang, Jin-Hui; Wang, Qiong-Hua

2017-09-18

We report an electrically controlled optofluidic zoom system which can achieve a large continuous zoom change and high-resolution image. The zoom system consists of an optofluidic zoom objective and a switchable light path which are controlled by two liquid optical shutters. The proposed zoom system can achieve a large tunable focal length range from 36mm to 92mm. And in this tuning range, the zoom system can correct aberrations dynamically, thus the image resolution is high. Due to large zoom range, the proposed imaging system incorporates both camera configuration and telescope configuration into one system. In addition, the whole system is electrically controlled by three electrowetting liquid lenses and two liquid optical shutters, therefore, the proposed system is very compact and free of mechanical moving parts. The proposed zoom system has potential to take place of conventional zoom systems.

Tunable Microcavity-Stabilized Quantum Cascade Laser for Mid-IR High-Resolution Spectroscopy and Sensing.

PubMed

Borri, Simone; Siciliani de Cumis, Mario; Insero, Giacomo; Bartalini, Saverio; Cancio Pastor, Pablo; Mazzotti, Davide; Galli, Iacopo; Giusfredi, Giovanni; Santambrogio, Gabriele; Savchenkov, Anatoliy; Eliyahu, Danny; Ilchenko, Vladimir; Akikusa, Naota; Matsko, Andrey; Maleki, Lute; De Natale, Paolo

2016-02-17

The need for highly performing and stable methods for mid-IR molecular sensing and metrology pushes towards the development of more and more compact and robust systems. Among the innovative solutions aimed at answering the need for stable mid-IR references are crystalline microresonators, which have recently shown excellent capabilities for frequency stabilization and linewidth narrowing of quantum cascade lasers with compact setups. In this work, we report on the first system for mid-IR high-resolution spectroscopy based on a quantum cascade laser locked to a CaF₂ microresonator. Electronic locking narrows the laser linewidth by one order of magnitude and guarantees good stability over long timescales, allowing, at the same time, an easy way for finely tuning the laser frequency over the molecular absorption line. Improvements in terms of resolution and frequency stability of the source are demonstrated by direct sub-Doppler recording of a molecular line.

Tunable Microcavity-Stabilized Quantum Cascade Laser for Mid-IR High-Resolution Spectroscopy and Sensing

PubMed Central

Borri, Simone; Siciliani de Cumis, Mario; Insero, Giacomo; Bartalini, Saverio; Cancio Pastor, Pablo; Mazzotti, Davide; Galli, Iacopo; Giusfredi, Giovanni; Santambrogio, Gabriele; Savchenkov, Anatoliy; Eliyahu, Danny; Ilchenko, Vladimir; Akikusa, Naota; Matsko, Andrey; Maleki, Lute; De Natale, Paolo

2016-01-01

The need for highly performing and stable methods for mid-IR molecular sensing and metrology pushes towards the development of more and more compact and robust systems. Among the innovative solutions aimed at answering the need for stable mid-IR references are crystalline microresonators, which have recently shown excellent capabilities for frequency stabilization and linewidth narrowing of quantum cascade lasers with compact setups. In this work, we report on the first system for mid-IR high-resolution spectroscopy based on a quantum cascade laser locked to a CaF2 microresonator. Electronic locking narrows the laser linewidth by one order of magnitude and guarantees good stability over long timescales, allowing, at the same time, an easy way for finely tuning the laser frequency over the molecular absorption line. Improvements in terms of resolution and frequency stability of the source are demonstrated by direct sub-Doppler recording of a molecular line. PMID:26901199

Phase-slope and phase measurements of tunable CW-THz radiation with terahertz comb for wide-dynamic-range, high-resolution, distance measurement of optically rough object.

PubMed

Yasui, Takeshi; Fujio, Makoto; Yokoyama, Shuko; Araki, Tsutomu

2014-07-14

Phase measurement of continuous-wave terahertz (CW-THz) radiation is a potential tool for direct distance and imaging measurement of optically rough objects due to its high robustness to optical rough surfaces. However, the 2π phase ambiguity in the phase measurement of single-frequency CW-THz radiation limits the dynamic range of the measured distance to the order of the wavelength used. In this article, phase-slope measurement of tunable CW-THz radiation with a THz frequency comb was effectively used to extend the dynamic range up to 1.834 m while maintaining an error of a few tens µm in the distance measurement of an optically rough object. Furthermore, a combination of phase-slope measurement of tunable CW-THz radiation and phase measurement of single-frequency CW-THz radiation enhanced the distance error to a few µm within the dynamic range of 1.834 m without any influence from the 2π phase ambiguity. The proposed method will be a powerful tool for the construction and maintenance of large-scale structures covered with optically rough surfaces.

Characterizing SOI Wafers By Use Of AOTF-PHI

NASA Technical Reports Server (NTRS)

Cheng, Li-Jen; Li, Guann-Pyng; Zang, Deyu

1995-01-01

Developmental nondestructive method of characterizing layers of silicon-on-insulator (SOI) wafer involves combination of polarimetric hyperspectral imaging by use of acousto-optical tunable filters (AOTF-PHI) and computational resources for extracting pertinent data on SOI wafers from polarimetric hyperspectral images. Offers high spectral resolution and both ease and rapidity of optical-wavelength tuning. Further efforts to implement all of processing of polarimetric spectral image data in special-purpose hardware for sake of procesing speed. Enables characterization of SOI wafers in real time for online monitoring and adjustment of production. Also accelerates application of AOTF-PHI to other applications in which need for high-resolution spectral imaging, both with and without polarimetry.

Development of High-Resolution UV-VIS Diagnostics for Space Plasma Simulation

NASA Astrophysics Data System (ADS)

Taylor, Andrew; Batishchev, Oleg

2012-10-01

Non-invasive far-UV-VIS plasma emission allows remote diagnostics of plasma, which is particularly important for space application. Accurate vacuum tank space plasma simulations require monochromators with high spectral resolution (better than 0.01A) to capture important details of atomic and ionic lines, such as Ly-alpha, etc. We are building a new system based on the previous work [1], and will discuss the development of a spectrometry system that combines a single-pass vacuum far-UV-NIR spectrometer and a tunable Fabry-Perot etalon. [4pt] [1] O. Batishchev and J.L. Cambier, Experimental Study of the Mini-Helicon Thruster, Air Force Research Laboratory Report, AFRL-RZ-ED-TR-2009-0020, 2009.

The Tunable XUV Imager (TXI) Sounding Rocket Payload

NASA Technical Reports Server (NTRS)

Brinton, John (Technical Monitor); Golub, Leon

2004-01-01

The TXI was flown successfully on 21 June 2001 (36.199 US). All systems functioned as planned and image data were acquired and sent to the ground. Unfortunately, due to a parachute failure the payload was destroyed. In this report we summarize results from the flight and provide detailed information on the high resolution X-ray imaging detector which was developed as part of the program.

Airborne Lidar measurements of the atmospheric pressure profile with tunable Alexandrite lasers

NASA Technical Reports Server (NTRS)

Korb, C. L.; Schwemmer, G. K.; Dombrowski, M.; Milrod, J.; Walden, H.

1986-01-01

The first remote measurements of the atmospheric pressure profile made from an airborne platform are described. The measurements utilize a differential absorption lidar and tunable solid state Alexandrite lasers. The pressure measurement technique uses a high resolution oxygen A band where the absorption is highly pressure sensitive due to collision broadening. Absorption troughs and regions of minimum absorption were used between pairs of stongly absorption lines for these measurements. The trough technique allows the measurement to be greatly desensitized to the effects of laser frequency instabilities. The lidar system was set up to measure pressure with the on-line laser tuned to the absorption trough at 13147.3/cm and with the reference laser tuned to a nonabsorbing frequency near 13170.0/cm. The lidar signal returns were sampled with a 200 range gate (30 vertical resoltion) and averaged over 100 shots.

Real-time spectroscopic sensing using a widely tunable external cavity-QCL with MOEMS diffraction grating

NASA Astrophysics Data System (ADS)

Ostendorf, Ralf; Butschek, Lorenz; Merten, André; Grahmann, Jan; Jarvis, Jan; Hugger, Stefan; Fuchs, Frank; Wagner, Joachim

2016-02-01

We present spectroscopic measurements performed with an EC-QCL combining a broadly tunable quantum cascade laser chip with a tuning range of more than 300 cm-1 and a resonantly driven MOEMS scanner with an integrated diffraction grating for wavelength selection in Littrow configuration. The grating geometry was optimized to provide high diffraction efficiency over the wide tuning range of the QCL, thus assuring high power density and high spectral resolution in the MIR range. The MOEMS scanner has a resonance frequency of 1 kHz, hence allowing for two full wavelength scans, one up and the other downwards, within 1 ms. The capability for real-time spectroscopic sensing based on MOEMS EC-QCLs is demonstrated by transmission measurements performed on polystyrene reference absorber sheets as well as on gaseous samples of carbon monoxide. For the latter one, a large portion of the characteristic CO absorption band containing several absorption lines in the range of 2070 cm-1 to 2280 cm-1 can be monitored in real-time.

Dual-color three-dimensional STED microscopy with a single high-repetition-rate laser

PubMed Central

Han, Kyu Young; Ha, Taekjip

2016-01-01

We describe a dual-color three-dimensional stimulated emission depletion (3D-STED) microscopy employing a single laser source with a repetition rate of 80 MHz. Multiple excitation pulses synchronized with a STED pulse were generated by a photonic crystal fiber and the desired wavelengths were selected by an acousto-optic tunable filter with high spectral purity. Selective excitation at different wavelengths permits simultaneous imaging of two fluorescent markers at a nanoscale resolution in three dimensions. PMID:26030581

Aluminum plasmonic metamaterials for structural color printing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Fei; Gao, Jie; Stan, Liliana

2015-01-01

We report a structural color printing platform based on aluminum plasmonic metamaterials supporting near perfect light absorption and narrow-band spectral response tunable across the visible spectrum to realize high-resolution, angle-insensitive color printing with high color purity and saturation. Additionally, the fabricated metamaterials can be protected by a transparent polymer thin layer for ambient use with further improved color performance. The demonstrated structural color printing with aluminum plasmonic metamaterials offers great potential for relevant applications such as security marking and information storage.

Aluminum plasmonic metamaterials for structural color printing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Fei; Gao, Jie; Stan, Liliana

2015-05-26

We report a structural color printing platform based on aluminum plasmonic metamaterials supporting near perfect light absorption and narrow-band spectral response tunable across the visible spectrum to realize high-resolution, angle-insensitive color printing with high color purity and saturation. Additionally, the fabricated metamaterials can be protected by a transparent polymer thin layer for ambient use with further improved color performance. The demonstrated structural color printing with aluminum plasmonic metamaterials offers great potential for relevant applications such as security marking and information storage.

Ponderomotive phase plate for transmission electron microscopes

DOEpatents

Reed, Bryan W [Livermore, CA

2012-07-10

A ponderomotive phase plate system and method for controllably producing highly tunable phase contrast transfer functions in a transmission electron microscope (TEM) for high resolution and biological phase contrast imaging. The system and method includes a laser source and a beam transport system to produce a focused laser crossover as a phase plate, so that a ponderomotive potential of the focused laser crossover produces a scattering-angle-dependent phase shift in the electrons of the post-sample electron beam corresponding to a desired phase contrast transfer function.

In vivo multiphoton microscopy beyond 1 mm in the brain

NASA Astrophysics Data System (ADS)

Miller, David R.; Medina, Flor A.; Hassan, Ahmed; Perillo, Evan P.; Hagan, Kristen; Kazmi, S. M. Shams; Zemelman, Boris V.; Dunn, Andrew K.

2017-02-01

We perform high-resolution, non-invasive, in vivo deep-tissue imaging of the mouse neocortex using multiphoton microscopy with a high repetition rate optical parametric amplifier laser source tunable between λ=1,100 and 1,400 nm. We demonstrate an imaging depth of 1,200 μm in vasculature and 1,160 μm in neurons. We also demonstrate deep-tissue imaging using Indocyanine Green (ICG), which is FDA approved and a promising route to translate multiphoton microscopy to human applications.

Spectral characterization and calibration of AOTF spectrometers and hyper-spectral imaging system

NASA Astrophysics Data System (ADS)

Katrašnik, Jaka; Pernuš, Franjo; Likar, Boštjan

2010-02-01

The goal of this article is to present a novel method for spectral characterization and calibration of spectrometers and hyper-spectral imaging systems based on non-collinear acousto-optical tunable filters. The method characterizes the spectral tuning curve (frequency-wavelength characteristic) of the AOTF (Acousto-Optic Tunable Filter) filter by matching the acquired and modeled spectra of the HgAr calibration lamp, which emits line spectrum that can be well modeled via AOTF transfer function. In this way, not only tuning curve characterization and corresponding spectral calibration but also spectral resolution assessment is performed. The obtained results indicated that the proposed method is efficient, accurate and feasible for routine calibration of AOTF spectrometers and hyper-spectral imaging systems and thereby a highly competitive alternative to the existing calibration methods.

TUNABLE DIODE LASER MEASUREMENTS OF NO2 NEAR 670 NM AND 395 NM. (R823933)

EPA Science Inventory

Two single-mode diode lasers were used to record high-resolution absorption spectra of NO2 (dilute in Ar) near 670.2 and 394.5 nm over a range of temperatures (296 to 774 K) and total pressures (2.4 x 10(-2) to 1 atm). A commercial InGaAsP laser was tuned 1.3 cm(-1) at a repetiti...

All-optical endoscopic probe for high resolution 3D photoacoustic tomography

NASA Astrophysics Data System (ADS)

Ansari, R.; Zhang, E.; Desjardins, A. E.; Beard, P. C.

2017-03-01

A novel all-optical forward-viewing photoacoustic probe using a flexible coherent fibre-optic bundle and a Fabry- Perot (FP) ultrasound sensor has been developed. The fibre bundle, along with the FP sensor at its distal end, synthesizes a high density 2D array of wideband ultrasound detectors. Photoacoustic waves arriving at the sensor are spatially mapped by optically scanning the proximal end face of the bundle in 2D with a CW wavelength-tunable interrogation laser. 3D images are formed from the detected signals using a time-reversal image reconstruction algorithm. The system has been characterized in terms of its PSF, noise-equivalent pressure and field of view. Finally, the high resolution 3D imaging capability has been demonstrated using arbitrary shaped phantoms and duck embryo.

Hyperspectral Proximal Sensing of Salix Alba Trees in the Sacco River Valley (Latium, Italy)

PubMed Central

Moroni, Monica; Lupo, Emanuela; Cenedese, Antonio

2013-01-01

Recent developments in hardware and software have increased the possibilities and reduced the costs of hyperspectral proximal sensing. Through the analysis of high resolution spectroscopic measurements at the laboratory or field scales, this monitoring technique is suitable for quantitative estimates of biochemical and biophysical variables related to the physiological state of vegetation. Two systems for hyperspectral imaging have been designed and developed at DICEA-Sapienza University of Rome, one based on the use of spectrometers, the other on tunable interference filters. Both systems provide a high spectral and spatial resolution with low weight, power consumption and cost. This paper describes the set-up of the tunable filter platform and its application to the investigation of the environmental status of the region crossed by the Sacco river (Latium, Italy). This was achieved by analyzing the spectral response given by tree samples, with roots partly or wholly submerged in the river, located upstream and downstream of an industrial area affected by contamination. Data acquired is represented as reflectance indices as well as reflectance values. Broadband and narrowband indices based on pigment content and carotenoids vs. chlorophyll content suggest tree samples located upstream of the contaminated area are ‘healthier’ than those downstream. PMID:24172281

X-Ray Structure determination of the Glycine Cleavage System Protein H of Mycobacterium tuberculosis Using An Inverse Compton Synchrotron X-Ray Source

PubMed Central

Abendroth, Jan; McCormick, Michael S.; Edwards, Thomas E.; Staker, Bart; Loewen, Roderick; Gifford, Martin; Rifkin, Jeff; Mayer, Chad; Guo, Wenjin; Zhang, Yang; Myler, Peter; Kelley, Angela; Analau, Erwin; Hewitt, Stephen Nakazawa; Napuli, Alberto J.; Kuhn, Peter; Ruth, Ronald D.; Stewart, Lance J.

2010-01-01

Structural genomics discovery projects require ready access to both X-ray and NMR instrumentation which support the collection of experimental data needed to solve large numbers of novel protein structures. The most productive X-ray crystal structure determination laboratories make extensive frequent use of tunable synchrotron X-ray light to solve novel structures by anomalous diffraction methods. This requires that frozen cryo-protected crystals be shipped to large government-run synchrotron facilities for data collection. In an effort to eliminate the need to ship crystals for data collection, we have developed the first laboratory-scale synchrotron light source capable of performing many of the state-of-the-art synchrotron applications in X-ray science. This Compact Light Source is a first-in-class device that uses inverse Compton scattering to generate X-rays of sufficient flux, tunable wavelength and beam size to allow high-resolution X-ray diffraction data collection from protein crystals. We report on benchmarking tests of X-ray diffraction data collection with hen egg white lysozyme, and the successful high-resolution X-ray structure determination of the Glycine cleavage system protein H from Mycobacterium tuberculosis using diffraction data collected with the Compact Light Source X-ray beam. PMID:20364333

Tunable far infrared studies of molecular parameters in support of stratospheric measurements

NASA Technical Reports Server (NTRS)

Chance, Kelly V.; Evenson, K. M.; Park, K.; Radostitz, J. V.; Jennings, D. A.; Nolt, I. G.; Vanek, M. D.

1991-01-01

Lab studies were made in support of far infrared spectroscopy of the stratosphere using the Tunable Far InfraRed (TuFIR) method of ultrahigh resolution spectroscopy and, more recently, spectroscopic and retrieval calculations performed in support of satellite-based atmospheric measurement programs: the Global Ozone Monitoring Experiment (GOME), and the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY).

Toward tunable doping in graphene FETs by molecular self-assembled monolayers

NASA Astrophysics Data System (ADS)

Li, Bing; Klekachev, Alexander V.; Cantoro, Mirco; Huyghebaert, Cedric; Stesmans, André; Asselberghs, Inge; de Gendt, Stefan; de Feyter, Steven

2013-09-01

In this paper, we report the formation of self-assembled monolayers (SAMs) of oleylamine (OA) on highly oriented pyrolytic graphite (HOPG) and graphene surfaces and demonstrate the potential of using such organic SAMs to tailor the electronic properties of graphene. Molecular resolution Atomic Force Microscopy (AFM) and Scanning Tunneling Microscopy (STM) images reveal the detailed molecular ordering. The electrical measurements show that OA strongly interacts with graphene leading to n-doping effects in graphene devices. The doping levels are tunable by varying the OA deposition conditions. Importantly, neither hole nor electron mobilities are decreased by the OA modification. As a benefit from this noncovalent modification strategy, the pristine characteristics of the device are recoverable upon OA removal. From this study, one can envision the possibility to correlate the graphene-based device performance with the molecular structure and supramolecular ordering of the organic dopant.In this paper, we report the formation of self-assembled monolayers (SAMs) of oleylamine (OA) on highly oriented pyrolytic graphite (HOPG) and graphene surfaces and demonstrate the potential of using such organic SAMs to tailor the electronic properties of graphene. Molecular resolution Atomic Force Microscopy (AFM) and Scanning Tunneling Microscopy (STM) images reveal the detailed molecular ordering. The electrical measurements show that OA strongly interacts with graphene leading to n-doping effects in graphene devices. The doping levels are tunable by varying the OA deposition conditions. Importantly, neither hole nor electron mobilities are decreased by the OA modification. As a benefit from this noncovalent modification strategy, the pristine characteristics of the device are recoverable upon OA removal. From this study, one can envision the possibility to correlate the graphene-based device performance with the molecular structure and supramolecular ordering of the organic dopant. Electronic supplementary information (ESI) available: AFM images of self-assembled monolayers of OA on HOPG; AFM height image of the graphene surface on a SiC substrate; high resolution STM image of a self-assembled monolayer of OA on HOPG; transfer curves of a graphene FET with and without baking steps; transfer curves of a graphene FET under high vacuum conditions; transfer curves of a graphene FET and its Raman response before and after OA treatment; transfer curves of a graphene FET before and after rinsing with n-hexane. See DOI: 10.1039/c3nr01255g

A high resolution spectroscopic study of the oxygen molecule. Ph.D. Thesis Final Report

NASA Technical Reports Server (NTRS)

Ritter, K. J.

1984-01-01

A high resolution spectrometer which incorporates a narrow line width tunable dye laser was used to make absorption profiles of 57 spectral lines in the Oxygen A-Band at pressures up to one atmosphere in pure O2. The observed line profiles are compared to the Voigt, and a collisionally narrowed, profile using a least squares fitting procedure. The collisionally narrowed profile compares more favorable to the observed profiles. Values of the line strengths and self broadening coeffiencients, determined from the least square fitting process, are presented in tabular form. It is found that the experssion by Watson are in closest agreement with the experimentally determined strengths. The self broadening coefficients are compared with the measurements of several other investigators.

Ozone height profiles using laser heterodyne radiometer

NASA Technical Reports Server (NTRS)

Jain, S. L.

1994-01-01

The monitoring of vertical profiles of ozone and related minor constituents in the atmosphere are of great significance to understanding the complex interaction between atmospheric dynamics, chemistry and radiation budget. An ultra high spectral resolution tunable CO2 laser heterodyne radiometer has been designed, developed and set up at the National Physical Laboratory, New Delhi to obtain vertical profiles of various minor constituents the characteristic absorption lines in 9 to 11 micron spectral range. Due to its high spectral resolution the lines can be resolved completely and data obtained are inverted to get vertical profiles using an inversion technique developed by the author. In the present communication the salient features of the laser heterodyne system and the results obtained are discussed in detail.

A High Spectral Resolution Lidar Based on Absorption Filter

NASA Technical Reports Server (NTRS)

Piironen, Paivi

1996-01-01

A High Spectral Resolution Lidar (HSRL) that uses an iodine absorption filter and a tunable, narrow bandwidth Nd:YAG laser is demonstrated. The iodine absorption filter provides better performance than the Fabry-Perot etalon that it replaces. This study presents an instrument design that can be used a the basis for a design of a simple and robust lidar for the measurement of the optical properties of the atmosphere. The HSRL provides calibrated measurements of the optical properties of the atmospheric aerosols. These observations include measurements of aerosol backscatter cross sections, optical depth, backscatter phase function depolarization, and multiple scattering. The errors in the HSRL data are discussed and the effects of different errors on the measured optical parameters are shown.

Tunable emergent heterostructures in a prototypical correlated metal

NASA Astrophysics Data System (ADS)

Fobes, D. M.; Zhang, S.; Lin, S.-Z.; Das, Pinaki; Ghimire, N. J.; Bauer, E. D.; Thompson, J. D.; Harriger, L. W.; Ehlers, G.; Podlesnyak, A.; Bewley, R. I.; Sazonov, A.; Hutanu, V.; Ronning, F.; Batista, C. D.; Janoschek, M.

2018-05-01

At the interface between two distinct materials, desirable properties, such as superconductivity, can be greatly enhanced1, or entirely new functionalities may emerge2. Similar to in artificially engineered heterostructures, clean functional interfaces alternatively exist in electronically textured bulk materials. Electronic textures emerge spontaneously due to competing atomic-scale interactions3, the control of which would enable a top-down approach for designing tunable intrinsic heterostructures. This is particularly attractive for correlated electron materials, where spontaneous heterostructures strongly affect the interplay between charge and spin degrees of freedom4. Here we report high-resolution neutron spectroscopy on the prototypical strongly correlated metal CeRhIn5, revealing competition between magnetic frustration and easy-axis anisotropy—a well-established mechanism for generating spontaneous superstructures5. Because the observed easy-axis anisotropy is field-induced and anomalously large, it can be controlled efficiently with small magnetic fields. The resulting field-controlled magnetic superstructure is closely tied to the formation of superconducting6 and electronic nematic textures7 in CeRhIn5, suggesting that in situ tunable heterostructures can be realized in correlated electron materials.

Plasmonic Nanobubbles as Tunable Cellular Probes for Cancer Theranostics

PubMed Central

Lapotko, Dmitri

2011-01-01

This review is focused on a novel cellular probe, the plasmonic nanobubble (PNB), which has the dynamically tunable and multiple functions of imaging, diagnosis, delivery, therapy and, ultimately, theranostics. The concept of theranostics was recently introduced in order to unite the clinically important stages of treatment, namely diagnosis, therapy and therapy guidance, into one single, rapid and highly accurate procedure. Cell level theranostics will have far-reaching implications for the treatment of cancer and other diseases at their earliest stages. PNBs were developed to support cell level theranostics as a new generation of on-demand tunable cellular probes. A PNB is a transient vapor nanobubble that is generated within nanoseconds around an overheated plasmonic nanoparticle with a short laser pulse. In the short term, we expect that PNB technology will be rapidly adaptable to clinical medicine, where the single cell resolution it provides will be critical for diagnosing incipient or residual disease and eliminating cancer cells, while leaving healthy cells intact. This review discusses mechanisms of plasmonic nanobubbles and their biomedical applications with the focus on cancer cell theranostics. PMID:21442036

Tunable emergent heterostructures in a prototypical correlated metal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fobes, D. M.; Zhang, S.; Lin, S. -Z.

We report at the interface between two distinct materials, desirable properties, such as superconductivity, can be greatly enhanced1, or entirely new functionalities may emerge. Similar to in artificially engineered heterostructures, clean functional interfaces alternatively exist in electronically textured bulk materials. Electronic textures emerge spontaneously due to competing atomic-scale interactions, the control of which would enable a top-down approach for designing tunable intrinsic heterostructures. This is particularly attractive for correlated electron materials, where spontaneous heterostructures strongly affect the interplay between charge and spin degrees of freedom. Here we report high-resolution neutron spectroscopy on the prototypical strongly correlated metal CeRhIn 5, revealingmore » competition between magnetic frustration and easy-axis anisotropy—a well-established mechanism for generating spontaneous superstructures. Because the observed easy-axis anisotropy is field-induced and anomalously large, it can be controlled efficiently with small magnetic fields. Finally, the resulting field-controlled magnetic superstructure is closely tied to the formation of superconducting and electronic nematic textures in CeRhIn 5, suggesting that in situ tunable heterostructures can be realized in correlated electron materials.« less

Tunable emergent heterostructures in a prototypical correlated metal

DOE PAGES

Fobes, D. M.; Zhang, S.; Lin, S. -Z.; ...

2018-03-26

We report at the interface between two distinct materials, desirable properties, such as superconductivity, can be greatly enhanced1, or entirely new functionalities may emerge. Similar to in artificially engineered heterostructures, clean functional interfaces alternatively exist in electronically textured bulk materials. Electronic textures emerge spontaneously due to competing atomic-scale interactions, the control of which would enable a top-down approach for designing tunable intrinsic heterostructures. This is particularly attractive for correlated electron materials, where spontaneous heterostructures strongly affect the interplay between charge and spin degrees of freedom. Here we report high-resolution neutron spectroscopy on the prototypical strongly correlated metal CeRhIn 5, revealingmore » competition between magnetic frustration and easy-axis anisotropy—a well-established mechanism for generating spontaneous superstructures. Because the observed easy-axis anisotropy is field-induced and anomalously large, it can be controlled efficiently with small magnetic fields. Finally, the resulting field-controlled magnetic superstructure is closely tied to the formation of superconducting and electronic nematic textures in CeRhIn 5, suggesting that in situ tunable heterostructures can be realized in correlated electron materials.« less

[Open-path online monitoring of ambient atmospheric CO2 based on laser absorption spectrum].

PubMed

He, Ying; Zhang, Yu-Jun; Kan, Rui-Feng; Xia, Hui; Geng, Hui; Ruan, Jun; Wang, Min; Cui, Xiao-Juan; Liu, Wen-Qing

2009-01-01

With the conjunction of tunable diode laser absorption spectroscopy technology (TDLAS) and the open long optical path technology, the system designing scheme of CO2 on-line monitoring based on near infrared tunable diode laser absorption spectroscopy technology was discussed in detail, and the instrument for large-range measurement was set up. By choosing the infrared absorption line of CO2 at 1.57 microm whose line strength is strong and suitable for measurement, the ambient atmospheric CO2 was measured continuously with a 30 s temporal resolution at an suburb site in the autumn of 2007. The diurnal atmospheric variations of CO2 and continuous monitoring results were presented. The results show that the variation in CO2 concentration has an obvious diurnal periodicity in suburb where the air is free of interference and contamination. The general characteristic of diurnal variation is that the concentration is low in the daytime and high at night, so it matches the photosynthesis trend. The instrument can detect gas concentration online with high resolution, high sensitivity, high precision, short response time and many other advantages, the monitoring requires no gas sampling, the calibration is easy, and the detection limit is about 4.2 x 10(-7). It has been proved that the system and measurement project are feasible, so it is an effective method for gas flux continuous online monitoring of large range in ecosystem based on TDLAS technology.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harilal, Sivanandan S.; LaHaye, Nicole L.; Phillips, Mark C.

We used a CW laser as a narrow-band (~50kHz) tunable LIF excitation source to probe absorption from selected atomic transitions (Al, U etc. ) in a ns laser ablation plume. A comparison of fluorescence signal with respect to emission spectroscopy show significant increase in the magnitude and persistence from selected Al and U transitions in a LIBS plume. The high spectral resolution provided by the LIF measurement allows peaks to be easily separated even if they overlap in the emission spectra.

MOEMS Fabry-Pérot interferometer with point-anchored Si-air mirrors for middle infrared

NASA Astrophysics Data System (ADS)

Tuohiniemi, Mikko; Näsilä, Antti; Akujärvi, Altti; Blomberg, Martti

2014-09-01

We studied how a micromachined Fabry-Pérot interferometer, realized with wide point-anchored Si/air-gap reflectors, performs at the middle-infrared. A computational analysis of the anchor mechanical behavior is also presented. Compared with solid-film reflectors, this technology features better index contrast, which enables a wider stop band and potentially higher resolution. In this work, we investigate whether the performance is improved according to the index-contrast benefit, or whether the mechanical differences play a role. For comparison, we manufactured and characterized another design that applies solid-film reflectors of Si/SiO2 structure. This data is exploited as a reference for a middle-infrared interferometer and as a template for mapping the performance from the simulation results to the measured data. The novel Si/air-gap device was realized as a non-tunable proof-of-concept version. The measured data is mapped into an estimate of the achievable performance of a tunable version. We present the measured transmission and resolution data and compare the simulation models that reproduce the data. The prediction for the tunable middle-infrared Si/air-gap device is then presented. The results indicate that the interferometer’s resolution is expected to have improved twofold and have a much wider stop band compared with the prior art.

Development and Experimental Verification of a High Resolution, Tunable LIDAR Computer Simulation Model for Atmospheric Laser Remote Sensing

NASA Astrophysics Data System (ADS)

Wilcox, William Edward, Jr.

1995-01-01

A computer program (LIDAR-PC) and associated atmospheric spectral databases have been developed which accurately simulate the laser remote sensing of the atmosphere and the system performance of a direct-detection Lidar or tunable Differential Absorption Lidar (DIAL) system. This simulation program allows, for the first time, the use of several different large atmospheric spectral databases to be coupled with Lidar parameter simulations on the same computer platform to provide a real-time, interactive, and easy to use design tool for atmospheric Lidar simulation and modeling. LIDAR -PC has been used for a range of different Lidar simulations and compared to experimental Lidar data. In general, the simulations agreed very well with the experimental measurements. In addition, the simulation offered, for the first time, the analysis and comparison of experimental Lidar data to easily determine the range-resolved attenuation coefficient of the atmosphere and the effect of telescope overlap factor. The software and databases operate on an IBM-PC or compatible computer platform, and thus are very useful to the research community for Lidar analysis. The complete Lidar and atmospheric spectral transmission modeling program uses the HITRAN database for high-resolution molecular absorption lines of the atmosphere, the BACKSCAT/LOWTRAN computer databases and models for the effects of aerosol and cloud backscatter and attenuation, and the range-resolved Lidar equation. The program can calculate the Lidar backscattered signal-to-noise for a slant path geometry from space and simulate the effect of high resolution, tunable, single frequency, and moderate line width lasers on the Lidar/DIAL signal. The program was used to model and analyze the experimental Lidar data obtained from several measurements. A fixed wavelength, Ho:YSGG aerosol Lidar (Sugimoto, 1990) developed at USF and a tunable Ho:YSGG DIAL system (Cha, 1991) for measuring atmospheric water vapor at 2.1 μm were analyzed. The simulations agreed very well with the measurements, and also yielded, for the first time, the ability to easily deduce the atmospheric attentuation coefficient, alpha, from the Lidar data. Simulations and analysis of other Lidar measurements included that of a 1.57 mu m OPO aerosol Lidar system developed at USF (Harrell, 1995) and of the NASA LITE (Laser-in-Space Technology Experiment) Lidar recently flown in the Space shuttle. Finally, an extensive series of laboratory experiments were made with the 1.57 μm OPO Lidar system to test calculations of the telescope/laser overlap and the effect of different telescope sizes and designs. The simulations agreed well with the experimental data for the telescope diameter and central obscuration test cases. The LIDAR-PC programs are available on the Internet from the USAF Lidar Home Page Web site, http://www.cas.usf.edu/physics/lidar.html/.

Pixel-level tunable liquid crystal lenses for auto-stereoscopic display

NASA Astrophysics Data System (ADS)

Li, Kun; Robertson, Brian; Pivnenko, Mike; Chu, Daping; Zhou, Jiong; Yao, Jun

2014-02-01

Mobile video and gaming are now widely used, and delivery of a glass-free 3D experience is of both research and development interest. The key drawbacks of a conventional 3D display based on a static lenticular lenslet array and parallax barriers are low resolution, limited viewing angle and reduced brightness, mainly because of the need of multiple-pixels for each object point. This study describes the concept and performance of pixel-level cylindrical liquid crystal (LC) lenses, which are designed to steer light to the left and right eye sequentially to form stereo parallax. The width of the LC lenses can be as small as 20-30 μm, so that the associated auto-stereoscopic display will have the same resolution as the 2D display panel in use. Such a thin sheet of tunable LC lens array can be applied directly on existing mobile displays, and can deliver 3D viewing experience while maintaining 2D viewing capability. Transparent electrodes were laser patterned to achieve the single pixel lens resolution, and a high birefringent LC material was used to realise a large diffraction angle for a wide field of view. Simulation was carried out to model the intensity profile at the viewing plane and optimise the lens array based on the measured LC phase profile. The measured viewing angle and intensity profile were compared with the simulation results.

Highly Tunable Complementary Micro/Submicro-Nanopatterned Surfaces Combining Block Copolymer Self-Assembly and Colloidal Lithography.

PubMed

Chang, Tongxin; Du, Binyang; Huang, Haiying; He, Tianbai

2016-08-31

Two kinds of large-area ordered and highly tunable micro/submicro-nanopatterned surfaces in a complementary manner were successfully fabricated by elaborately combining block copolymer self-assembly and colloidal lithography. Employing a monolayer of polystyrene (PS) colloidal spheres assembled on top as etching mask, polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) or polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) micelle films were patterned into micro/submicro patches by plasma etching, which could be further transferred into micropatterned metal nanoarrays by subsequent metal precursor loading and a second plasma etching. On the other hand, micro/submicro-nanopatterns in a complementary manner were generated via preloading a metal precursor in initial micelle films before the assembly of PS colloidal spheres on top. Both kinds of micro/submicro-nanopatterns showed good fidelity at the micro/submicroscale and nanoscale; meanwhile, they could be flexibly tuned by the sample and processing parameters. Significantly, when the PS colloidal sphere size was reduced to 250 nm, a high-resolution submicro-nanostructured surface with 3-5 metal nanoparticles in each patch or a single-nanoparticle interconnected honeycomb network was achieved. Moreover, by applying gold (Au) nanoparticles as anchoring points, micronanopatterned Au arrays can serve as a flexible template to pattern bovine serum albumin (BSA) molecules. This facile and cost-effective approach may provide a novel platform for fabrication of micropatterned nanoarrays with high tunability and controllability, which are promising in the applications of biological and microelectronic fields.

Electrically tunable lens speeds up 3D orbital tracking

PubMed Central

Annibale, Paolo; Dvornikov, Alexander; Gratton, Enrico

2015-01-01

3D orbital particle tracking is a versatile and effective microscopy technique that allows following fast moving fluorescent objects within living cells and reconstructing complex 3D shapes using laser scanning microscopes. We demonstrated notable improvements in the range, speed and accuracy of 3D orbital particle tracking by replacing commonly used piezoelectric stages with Electrically Tunable Lens (ETL) that eliminates mechanical movement of objective lenses. This allowed tracking and reconstructing shape of structures extending 500 microns in the axial direction. Using the ETL, we tracked at high speed fluorescently labeled genomic loci within the nucleus of living cells with unprecedented temporal resolution of 8ms using a 1.42NA oil-immersion objective. The presented technology is cost effective and allows easy upgrade of scanning microscopes for fast 3D orbital tracking. PMID:26114037

Software-defined microwave photonic filter with high reconfigurable resolution

PubMed Central

Wei, Wei; Yi, Lilin; Jaouën, Yves; Hu, Weisheng

2016-01-01

Microwave photonic filters (MPFs) are of great interest in radio frequency systems since they provide prominent flexibility on microwave signal processing. Although filter reconfigurability and tunability have been demonstrated repeatedly, it is still difficult to control the filter shape with very high precision. Thus the MPF application is basically limited to signal selection. Here we present a polarization-insensitive single-passband arbitrary-shaped MPF with ~GHz bandwidth based on stimulated Brillouin scattering (SBS) in optical fibre. For the first time the filter shape, bandwidth and central frequency can all be precisely defined by software with ~MHz resolution. The unprecedented multi-dimensional filter flexibility offers new possibilities to process microwave signals directly in optical domain with high precision thus enhancing the MPF functionality. Nanosecond pulse shaping by implementing precisely defined filters is demonstrated to prove the filter superiority and practicability. PMID:27759062

Software-defined microwave photonic filter with high reconfigurable resolution.

PubMed

Wei, Wei; Yi, Lilin; Jaouën, Yves; Hu, Weisheng

2016-10-19

Microwave photonic filters (MPFs) are of great interest in radio frequency systems since they provide prominent flexibility on microwave signal processing. Although filter reconfigurability and tunability have been demonstrated repeatedly, it is still difficult to control the filter shape with very high precision. Thus the MPF application is basically limited to signal selection. Here we present a polarization-insensitive single-passband arbitrary-shaped MPF with ~GHz bandwidth based on stimulated Brillouin scattering (SBS) in optical fibre. For the first time the filter shape, bandwidth and central frequency can all be precisely defined by software with ~MHz resolution. The unprecedented multi-dimensional filter flexibility offers new possibilities to process microwave signals directly in optical domain with high precision thus enhancing the MPF functionality. Nanosecond pulse shaping by implementing precisely defined filters is demonstrated to prove the filter superiority and practicability.

Broadly tunable ultrafast pump-probe system operating at multi-kHz repetition rate

NASA Astrophysics Data System (ADS)

Grupp, Alexander; Budweg, Arne; Fischer, Marco P.; Allerbeck, Jonas; Soavi, Giancarlo; Leitenstorfer, Alfred; Brida, Daniele

2018-01-01

Femtosecond systems based on ytterbium as active medium are ideal for driving ultrafast optical parametric amplifiers in a broad frequency range. The excellent stability of the source and the repetition rate tunable to up to hundreds of kHz allow for the implementation of an advanced two-color pump probe setup with the capability to achieve excellent signal-to-noise performances with sub-10 fs temporal resolution.

Microchannel plate detector technology potential for LUVOIR and HabEx

NASA Astrophysics Data System (ADS)

Siegmund, O. H. W.; Ertley, C.; Vallerga, J. V.; Schindhelm, E. R.; Harwit, A.; Fleming, B. T.; France, K. C.; Green, J. C.; McCandliss, S. R.; Harris, W. M.

2017-08-01

Microchannel plate (MCP) detectors have been the detector of choice for ultraviolet (UV) instruments onboard many NASA missions. These detectors have many advantages, including high spatial resolution (<20 μm), photon counting, radiation hardness, large formats (up to 20 cm), and ability for curved focal plane matching. Novel borosilicate glass MCPs with atomic layer deposition combine extremely low backgrounds, high strength, and tunable secondary electron yield. GaN and combinations of bialkali/alkali halide photocathodes show promise for broadband, higher quantum efficiency. Cross-strip anodes combined with compact ASIC readout electronics enable high spatial resolution over large formats with high dynamic range. The technology readiness levels of these technologies are each being advanced through research grants for laboratory testing and rocket flights. Combining these capabilities would be ideal for UV instruments onboard the Large UV/Optical/IR Surveyor (LUVOIR) and the Habitable Exoplanet Imaging Mission (HABEX) concepts currently under study for NASA's Astrophysics Decadal Survey.

Continuous glucose determination using fiber-based tunable mid-infrared laser spectroscopy

NASA Astrophysics Data System (ADS)

Yu, Songlin; Li, Dachao; Chong, Hao; Sun, Changyue; Xu, Kexin

2014-04-01

Wavelength-tunable laser spectroscopy in combination with a small-sized fiber-optic attenuated total reflection (ATR) sensor (fiber-based evanescent field analysis, FEFA) is reported for the continuous measurement of the glucose level. We propose a method of controlling and stabilizing the wavelength and power of laser emission and present a newly developed mid-infrared wavelength-tunable laser with a broad emission spectrum band of 9.19-9.77 μm (1024-1088 cm-1). The novel small-sized flow-through fiber-optic ATR sensor with long optical sensing length was used for glucose level determination. The experimental results indicate that the noise-equivalent concentration of this laser measurement system is as low as 3.8 mg/dL, which is among the most precise glucose measurements using mid-infrared spectroscopy. The sensitivity, which is three times that of conventional Fourier transform infrared spectrometer, was acquired because of the higher laser power and higher spectral resolution. The best prediction of the glucose concentration in phosphate buffered saline solution was achieved using the five-variable partial least-squares model, yielding a root-mean-square error of prediction as small as 3.5 mg/dL. The high sensitivity, multiple tunable wavelengths and small fiber-based sensor with long optical sensing length make glucose determination possible in blood or interstitial fluid in vivo.

Interferometer. [high resolution

NASA Technical Reports Server (NTRS)

Breckinridge, J. B.; Norton, R. H.; Schindler, R. A. (Inventor)

1981-01-01

A high resolution interferometer is described. The interferometer is insensitive to slight misalignment of its elements, avoids channeling in the spectrum, generates a maximum equal path fringe contrast, produces an even two sided interferogram without critical matching of the wedge angles of the beamsplitter and compensator wedges, and is optically phase tunable. The interferometer includes a mirror along the path of each beam component produced by the beamsplitter, for reflecting the beam component from the beamsplitter, for reflecting the beam component from the beamsplitter to a corresponding retroreflector and for reflecting the beam returned by the retroreflector back to the beamsplitter. A wedge located along each beam component path, is large enough to cover the retroreflector, so that each beam component passes through the wedge during movement towards the retroreflector and away therefrom.

Controlling total spot power from holographic laser by superimposing a binary phase grating.

PubMed

Liu, Xiang; Zhang, Jian; Gan, Yu; Wu, Liying

2011-04-25

By superimposing a tunable binary phase grating with a conventional computer-generated hologram, the total power of multiple holographic 3D spots can be easily controlled by changing the phase depth of grating with high accuracy to a random power value for real-time optical manipulation without extra power loss. Simulation and experiment results indicate that a resolution of 0.002 can be achieved at a lower time cost for normalized total spot power.

Tunable high-power blue external cavity semiconductor laser

NASA Astrophysics Data System (ADS)

Ding, Ding; Lv, Xueqin; Chen, Xinyi; Wang, Fei; Zhang, Jiangyong; Che, Kaijun

2017-09-01

A commercially available high-power GaN-based blue laser diode has been operated in a simple Littrow-type external cavity (EC). Two kinds of EC configurations with the grating lines perpendicular (A configuration) and parallel (B configuration) to the p-n junction are evaluated. Good performance has been demonstrated for the EC laser with B configuration due to the better mode selection effect induced by the narrow feedback wavelength range from the grating. Under an injection current of 1100 mA, the spectral linewidth is narrowed significantly down to ∼0.1 nm from ∼1 nm (the free-running width), with a good wavelength-locking behavior and a higher than 35 dB-amplified spontaneous emission suppression ratio. Moreover, a tuning bandwidth of 3.6 nm from 443.9 nm to 447.5 nm is realized with output power of 1.24 W and EC coupling efficiency of 80% at the central wavelength. The grating-coupled blue EC laser with narrow spectral linewidth, flexible wavelength tunability, and high output power shows potential applications in atom cooling and trapping, high-resolution spectroscopy, second harmonic generation, and high-capacity holographic data storage.

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 rejection, and constant bandwidth is designed, simulated, fabricated and measured. The filters are fabricated using barium strontium titanate (BST) varactors. Electromagnetic simulations and measured results of the tunable two-pole ferroelectric filter are analyzed to explore the origins of high insertion loss in ferroelectric filters. The results indicate that the high-permittivity of the BST (a ferroelectric) not only makes the filters tunable and compact, but also increases the conductive loss of the ferroelectric-based tunable resonators which translates into high insertion loss in ferroelectric filters.

An imaging vector magnetograph for the next solar maximum

NASA Technical Reports Server (NTRS)

Mickey, D. L.; Labonte, B. J.; Canfield, R. C.

1989-01-01

Researchers describe the conceptual design of a new imaging vector magnetograph currently being constructed at the University of Hawaii. The instrument combines a modest solar telescope with a rotating quarter-wave plate, an acousto-optical tunable prefilter as a blocker for a servo-controlled Fabry-Perot etalon, CCD cameras, and on-line digital image processing. Its high spatial resolution (1/2 arcsec pixel size) over a large field of view (5 by 5 arcmin) will be sufficient to significantly measure, for the first time, the magnetic energy dissipated in major solar flares. Its millisecond tunability and wide spectral range (5000 to 7000 A) enable nearly simultaneous vector magnetic field measurements in the gas-pressure-dominated photosphere and magnetically-dominated chromosphere, as well as effective co-alignment with Solar-A's X ray images. Researchers expect to have the instrument in operation at Mees Solar Observatory (Haleakala) in early 1991. They have chosen to use tunable filters as wavelength-selection elements in order to emphasize the spatial relationships between magnetic field elements, and to permit construction of a compact, efficient instrument. This means that spectral information must be obtained from sequences of images, which can cause line profile distortions due to effects of atmospheric seeing.

Tunable long persistent luminescence in the second near-infrared window via crystal field control.

PubMed

Nie, Jianmin; Li, Yang; Liu, Shanshan; Chen, Qiuqun; Xu, Qi; Qiu, Jianrong

2017-09-29

Construction of an active composite as a biomarker with deeper tissue penetration and higher signal-to-noise ratio (SNR) is of great importance for the application in bioimaging. Here, we report a strategy for tuning the emission bandwidth and intensity via crystal field control in long persistent phosphors (LPPs). Ni 2+ -doped Zn 1+y Sn y Ga 2-x-2y O 4 phosphors, with a tunable emission band peaking from 1270 to 1430 nm in the second near-infrared (NIR) window, have been successfully prepared. Such featured materials have the advantages of low absorption and scattering as well as more efficient tissue penetration. The emission spectra can be controlled by tailoring the local crystal field around the activator precisely via substitution of Zn and Sn for Ga. Moreover, with high resolution and weak light disturbance, these developed multi-band afterglow phosphors exhibit great application potential in advanced optical imaging.

Field propagation-induced directionality of carrier-envelope phase-controlled photoemission from nanospheres

PubMed Central

Süßmann, F.; Seiffert, L.; Zherebtsov, S.; Mondes, V.; Stierle, J.; Arbeiter, M.; Plenge, J.; Rupp, P.; Peltz, C.; Kessel, A.; Trushin, S. A.; Ahn, B.; Kim, D.; Graf, C.; Rühl, E.; Kling, M. F.; Fennel, T.

2015-01-01

Near-fields of non-resonantly laser-excited nanostructures enable strong localization of ultrashort light fields and have opened novel routes to fundamentally modify and control electronic strong-field processes. Harnessing spatiotemporally tunable near-fields for the steering of sub-cycle electron dynamics may enable ultrafast optoelectronic devices and unprecedented control in the generation of attosecond electron and photon pulses. Here we utilize unsupported sub-wavelength dielectric nanospheres to generate near-fields with adjustable structure and study the resulting strong-field dynamics via photoelectron imaging. We demonstrate field propagation-induced tunability of the emission direction of fast recollision electrons up to a regime, where nonlinear charge interaction effects become dominant in the acceleration process. Our analysis supports that the timing of the recollision process remains controllable with attosecond resolution by the carrier-envelope phase, indicating the possibility to expand near-field-mediated control far into the realm of high-field phenomena. PMID:26264422

Field propagation-induced directionality of carrier-envelope phase-controlled photoemission from nanospheres.

PubMed

Süßmann, F; Seiffert, L; Zherebtsov, S; Mondes, V; Stierle, J; Arbeiter, M; Plenge, J; Rupp, P; Peltz, C; Kessel, A; Trushin, S A; Ahn, B; Kim, D; Graf, C; Rühl, E; Kling, M F; Fennel, T

2015-08-12

Near-fields of non-resonantly laser-excited nanostructures enable strong localization of ultrashort light fields and have opened novel routes to fundamentally modify and control electronic strong-field processes. Harnessing spatiotemporally tunable near-fields for the steering of sub-cycle electron dynamics may enable ultrafast optoelectronic devices and unprecedented control in the generation of attosecond electron and photon pulses. Here we utilize unsupported sub-wavelength dielectric nanospheres to generate near-fields with adjustable structure and study the resulting strong-field dynamics via photoelectron imaging. We demonstrate field propagation-induced tunability of the emission direction of fast recollision electrons up to a regime, where nonlinear charge interaction effects become dominant in the acceleration process. Our analysis supports that the timing of the recollision process remains controllable with attosecond resolution by the carrier-envelope phase, indicating the possibility to expand near-field-mediated control far into the realm of high-field phenomena.

Mass attenuation coefficients in the range 3.8⩽E⩽11 keV, K fluorescence yield and Kβ/Kα relative X-ray emission rate for Ti, V, Fe, Co, Ni, Cu and Zn measured with a tunable monochromatic X-ray source

NASA Astrophysics Data System (ADS)

Ménesguen, Y.; Lépy, M.-C.

2010-08-01

This work presents new measurements of mass attenuation coefficients in the range 3.8⩽E⩽11 keV, K-absorption jump-ratios, Kα and Kβ fluorescence yields for Ti, V, Fe, Co, Ni, Cu and Zn. We use the experimental facility SOLEX, a tunable monochromatic X-ray source combined with an energy-dispersive high-purity germanium detector. The results are compared with theoretical values as well as with other experimental data and show a relatively good agreement. However, the derived K-jump-ratios appear larger than those widely used in the XCOM database. The Kα and Kβ fluorescence yields and the corresponding relative emission rates Kβ/Kα are also derived, which was made possible by the use of energy-dispersive detectors with good spectral resolution.

High-pulse energy supercontinuum laser for high-resolution spectroscopic photoacoustic imaging of lipids in the 1650-1850 nm region.

PubMed

Dasa, Manoj Kumar; Markos, Christos; Maria, Michael; Petersen, Christian R; Moselund, Peter M; Bang, Ole

2018-04-01

We propose a cost-effective high-pulse energy supercontinuum (SC) source based on a telecom range diode laser-based amplifier and a few meters of standard single-mode optical fiber, with a pulse energy density as high as ~25 nJ/nm in the 1650-1850 nm regime (factor >3 times higher than any SC source ever used in this wavelength range). We demonstrate how such an SC source combined with a tunable filter allows high-resolution spectroscopic photoacoustic imaging and the spectroscopy of lipids in the first overtone transition band of C-H bonds (1650-1850 nm). We show the successful discrimination of two different lipids (cholesterol and lipid in adipose tissue) and the photoacoustic cross-sectional scan of lipid-rich adipose tissue at three different locations. The proposed high-pulse energy SC laser paves a new direction towards compact, broadband and cost-effective source for spectroscopic photoacoustic imaging.

High resolution strain sensor for earthquake precursor observation and earthquake monitoring

NASA Astrophysics Data System (ADS)

Zhang, Wentao; Huang, Wenzhu; Li, Li; Liu, Wenyi; Li, Fang

2016-05-01

We propose a high-resolution static-strain sensor based on a FBG Fabry-Perot interferometer (FBG-FP) and a wavelet domain cross-correlation algorithm. This sensor is used for crust deformation measurement, which plays an important role in earthquake precursor observation. The Pound-Drever-Hall (PDH) technique based on a narrow-linewidth tunable fiber laser is used to interrogate the FBG-FPs. A demodulation algorithm based on wavelet domain cross-correlation is used to calculate the wavelength difference. The FBG-FP sensor head is fixed on the two steel alloy rods which are installed in the bedrock. The reference FBG-FP is placed in a strain-free state closely to compensate the environment temperature fluctuation. A static-strain resolution of 1.6 n(epsilon) can be achieved. As a result, clear solid tide signals and seismic signals can be recorded, which suggests that the proposed strain sensor can be applied to earthquake precursor observation and earthquake monitoring.

Single mode, short cavity, Pb-salt diode lasers operating in the 5, 10, and 30-microns spectral regions

NASA Technical Reports Server (NTRS)

Linden, K. J.

1985-01-01

Pb-salt diode lasers are being used as frequency-tunable infrared sources in high resolution spectroscopy and heterodyne detection applications. Recent advances in short cavity, stripe-geometry laser configurations have led to significant increases in maximum CW operating temperature, single mode operation, and increased single mode tuning range. This paper describes short cavity, stripe geometry lasers operating in the 5, 10, and 30-microns spectral regions, with single mode tuning ranges of over 6/cm.

A narrow-band injection-seeded pulsed titanium:sapphire oscillator-amplifier system with on-line chirp analysis for high-resolution spectroscopy.

PubMed

Hannemann, S; van Duijn, E-J; Ubachs, W

2007-10-01

A narrow-band tunable injection-seeded pulsed titanium:sapphire laser system has been developed for application in high-resolution spectroscopic studies at the fundamental wavelengths in the near infrared as well as in the ultraviolet, deep ultraviolet, and extreme ultraviolet after upconversion. Special focus is on the quantitative assessment of the frequency characteristics of the oscillator-amplifier system on a pulse-to-pulse basis. Frequency offsets between continuous-wave seed light and the pulsed output are measured as well as linear chirps attributed mainly to mode pulling effects in the oscillator cavity. Operational conditions of the laser are found in which these offset and chirp effects are minimal. Absolute frequency calibration at the megahertz level of accuracy is demonstrated on various atomic and molecular resonance lines.

Investigation of solar active regions at high resolution by balloon flights of the solar optical universal polarimeter, definition phase

NASA Technical Reports Server (NTRS)

Tarbell, Theodore D.; Topka, Kenneth P.

1992-01-01

The definition phase of a scientific study of active regions on the sun by balloon flight of a former Spacelab instrument, the Solar Optical Universal Polarimeter (SOUP) is described. SOUP is an optical telescope with image stabilization, tunable filter and various cameras. After the flight phase of the program was cancelled due to budgetary problems, scientific and engineering studies relevant to future balloon experiments of this type were completed. High resolution observations of the sun were obtained using SOUP components at the Swedish Solar Observatory in the Canary Islands. These were analyzed and published in studies of solar magnetic fields and active regions. In addition, testing of low-voltage piezoelectric transducers was performed, which showed they were appropriate for use in image stabilization on a balloon.

Toward individually tunable compound eyes with transparent graphene electrode.

PubMed

Shahini, Ali; Jin, Hai; Zhou, Zhixian; Zhao, Yang; Chen, Pai-Yen; Hua, Jing; Cheng, Mark Ming-Cheng

2017-06-08

We present tunable compound eyes made of ionic liquid lenses, of which both curvatures (R 1 and R 2 in the lensmaker's equation) can be individually changed using electrowetting on dielectric (EWOD) and applied pressure. Flexible graphene is used as a transparent electrode and is integrated on a flexible polydimethylsiloxane (PDMS)/parylene hybrid substrate. Graphene electrodes allow a large lens aperture diameter of between 2.4 mm and 2.74 mm. Spherical aberration analysis is performed using COMSOL to investigate the optical property of the lens under applied voltage and pressure. The final lens system shows a resolution of 645.1 line pair per millimeter. A prototype of a tunable lens array is proposed for the application of a compound eye.

Tunable diode-laser absorption measurements of methane at elevated temperatures

NASA Astrophysics Data System (ADS)

Nagali, V.; Chou, S. I.; Baer, D. S.; Hanson, R. K.; Segall, J.

1996-07-01

A diode-laser sensor system based on absorption spectroscopy techniques has been developed to monitor CH4 nonintrusively in high-temperature environments. Fundamental spectroscopic parameters, including the line strengths of the transitions in the R(6) manifold of the 2 nu 3 band near 1.646 mu m, have been determined from high-resolution absorption measurements in a heated static cell. In addition, a corrected expression for the CH 4 partition function has been validated experimentally over the temperature range from 400 to 915 K. Potential applications of the diode-laser sensor system include process control, combustion measurements, and atmospheric monitoring.

High Power Local Oscillator Sources for 1-2 THz

NASA Technical Reports Server (NTRS)

Mehdi, Imran; Thomas, Bertrand; Lin, Robert; Maestrini, Alain; Ward, John; Schlecht, Erich; Gill, John; Lee, Choonsup; Chattopadhyay, Goutam; Maiwald, Frank

2010-01-01

Recent results from the Heterodyne Instrument for Far-Infrared (HIFI) on the Herschel Space Telescope have confirmed the usefulness of high resolution spectroscopic data for a better understanding of our Universe. This paper will explore the current status of tunable local oscillator sources beyond HIFI and provide demonstration of how power combining of GaAs Schottky diodes can be used to increase both power and upper operating frequency for heterodyne receivers. Availability of power levels greater than 1 watt in the W-band now makes it possible to design a 1900 GHz source with more than 100 microwatts of expected output power.

Absorber Materials for Transition-Edge Sensor X-ray Microcalorimeters

NASA Technical Reports Server (NTRS)

Brown, Ari-David; Bandler, Simon; Brekosky, Regis; Chervenak, James; Figueroa-Feliciano, Enectali; Finkbeiner, Fred; Sadleir, Jack; Iyomoto, Naoko; Kelley, Richard; Kilbourne, Caroline;

Acoustic focusing by symmetrical self-bending beams with phase modulations

NASA Astrophysics Data System (ADS)

Gao, He; Gu, Zhong-ming; Liang, Bin; Zou, Xin-ye; Yang, Jing; Yang, Jun; Cheng, Jian-chun

2016-02-01

We propose a scheme for generating high-efficient acoustic focusing capable of circumventing obstacles in the propagating medium. This distinct feature that is highly desirable for practical applications is realized by employing two symmetrical Airy beams, and a different type of acoustic lens is designed by using a zero-index medium to provide the required phase profile with extremely high resolution. Furthermore, the scheme has the flexibility of generating tunable focal length. We anticipate our design to open possibilities for the design of acoustic lens and have potential applications in various important scenarios such as biomedical imaging/therapy and non-destructive evaluation.

Applications of absorption spectroscopy using quantum cascade lasers.

PubMed

Zhang, Lizhu; Tian, Guang; Li, Jingsong; Yu, Benli

2014-01-01

Infrared laser absorption spectroscopy (LAS) is a promising modern technique for sensing trace gases with high sensitivity, selectivity, and high time resolution. Mid-infrared quantum cascade lasers, operating in a pulsed or continuous wave mode, have potential as spectroscopic sources because of their narrow linewidths, single mode operation, tunability, high output power, reliability, low power consumption, and compactness. This paper reviews some important developments in modern laser absorption spectroscopy based on the use of quantum cascade laser (QCL) sources. Among the various laser spectroscopic methods, this review is focused on selected absorption spectroscopy applications of QCLs, with particular emphasis on molecular spectroscopy, industrial process control, combustion diagnostics, and medical breath analysis.

Fiber Bragg grating interrogation using wavelength modulated tunable distributed feedback lasers and a fiber-optic Mach-Zehnder interferometer.

PubMed

Roy, Anirban; Chakraborty, Arup Lal; Jha, Chandan Kumar

2017-04-20

This paper demonstrates a technique of high-resolution interrogation of two fiber Bragg gratings (FBGs) with flat-topped reflection spectra centered on 1649.55 nm and 1530.182 nm with narrow line width tunable semiconductor lasers emitting at 1651.93 nm and 1531.52 nm, respectively. The spectral shift of the reflection spectrum in response to temperature and strain is accurately measured with a fiber-optic Mach-Zehnder interferometer that has a free spectral range of 0.0523 GHz and a broadband photodetector. Laser wavelength modulation and harmonic detection techniques are used to transform the gentle edges of the flat-topped FBG into prominent leading and trailing peaks that are up to five times narrower than the FBG spectrum. Either of these peaks can be used to accurately measure spectral shifts of the FBG reflection spectrum with a resolution down to a value of 0.47 pm. A digital signal processing board is used to measure the temperature-induced spectral shifts over the range of 30°C-80°C and strain-induced spectral shifts from 0  μϵ to 12,000  μϵ. The shift is linear in both cases with a temperature sensitivity of 12.8 pm/°C and strain sensitivity of 0.12  pm/μϵ. The distinctive feature of this technique is that it does not use an optical spectrum analyzer at any stage of its design or operation. It can be readily extended to all types of tunable diode lasers and is ideally suited for compact field instruments and for biomedical applications in stroke rehabilitation monitoring.

Daniel K. Inouye Solar Telescope: High-resolution observing of the dynamic Sun

NASA Astrophysics Data System (ADS)

Tritschler, A.; Rimmele, T. R.; Berukoff, S.; Casini, R.; Kuhn, J. R.; Lin, H.; Rast, M. P.; McMullin, J. P.; Schmidt, W.; Wöger, F.; DKIST Team

2016-11-01

The 4-m aperture Daniel K. Inouye Solar Telescope (DKIST) formerly known as the Advanced Technology Solar Telescope (ATST) is currently under construction on Haleakalā (Maui, Hawai'i) projected to start operations in 2019. At the time of completion, DKIST will be the largest ground-based solar telescope providing unprecedented resolution and photon collecting power. The DKIST will be equipped with a set of first-light facility-class instruments offering unique imaging, spectroscopic and spectropolarimetric observing opportunities covering the visible to infrared wavelength range. This first-light instrumentation suite will include: a Visible Broadband Imager (VBI) for high-spatial and -temporal resolution imaging of the solar atmosphere; a Visible Spectro-Polarimeter (ViSP) for sensitive and accurate multi-line spectropolarimetry; a Fabry-Pérot based Visible Tunable Filter (VTF) for high-spatial resolution spectropolarimetry; a fiber-fed Diffraction-Limited Near Infra-Red Spectro-Polarimeter (DL-NIRSP) for two-dimensional high-spatial resolution spectropolarimetry (simultaneous spatial and spectral information); and a Cryogenic Near Infra-Red Spectro-Polarimeter (Cryo-NIRSP) for coronal magnetic field measurements and on-disk observations of, e.g., the CO lines at 4.7 μm. We will provide an overview of the DKIST's unique capabilities with strong focus on the first-light instrumentation suite, highlight some of the additional properties supporting observations of transient and dynamic solar phenomena, and touch on some operational strategies and the DKIST critical science plan.

Two-color temporal focusing multiphoton excitation imaging with tunable-wavelength excitation

NASA Astrophysics Data System (ADS)

Lien, Chi-Hsiang; Abrigo, Gerald; Chen, Pei-Hsuan; Chien, Fan-Ching

2017-02-01

Wavelength tunable temporal focusing multiphoton excitation microscopy (TFMPEM) is conducted to visualize optical sectioning images of multiple fluorophore-labeled specimens through the optimal two-photon excitation (TPE) of each type of fluorophore. The tunable range of excitation wavelength was determined by the groove density of the grating, the diffraction angle, the focal length of lenses, and the shifting distance of the first lens in the beam expander. Based on a consideration of the trade-off between the tunable-wavelength range and axial resolution of temporal focusing multiphoton excitation imaging, the presented system demonstrated a tunable-wavelength range from 770 to 920 nm using a diffraction grating with groove density of 830 lines/mm. TPE fluorescence imaging examination of a fluorescent thin film indicated that the width of the axial confined excitation was 3.0±0.7 μm and the shifting distance of the temporal focal plane was less than 0.95 μm within the presented wavelength tunable range. Fast different wavelength excitation and three-dimensionally rendered imaging of Hela cell mitochondria and cytoskeletons and mouse muscle fibers were demonstrated. Significantly, the proposed system can improve the quality of two-color TFMPEM images through different excitation wavelengths to obtain higher-quality fluorescent signals in multiple-fluorophore measurements.

Airborne and ground based lidar measurements of the atmospheric pressure profile

NASA Technical Reports Server (NTRS)

Korb, C. Laurence; Schwemmer, Geary K.; Dombrowski, Mark; Weng, Chi Y.

1989-01-01

The first high accuracy remote measurements of the atmospheric pressure profile have been made. The measurements were made with a differential absorption lidar system that utilizes tunable alexandrite lasers. The absorption in the trough between two lines in the oxygen A-band near 760 nm was used for probing the atmosphere. Measurements of the two-dimensional structure of the pressure field were made in the troposphere from an aircraft looking down. Also, measurements of the one-dimensional structure were made from the ground looking up. Typical pressure accuracies for the aircraft measurements were 1.5-2 mbar with a 30-m vertical resolution and a 100-shot average (20 s), which corresponds to a 2-km horizontal resolution. Typical accuracies for the upward viewing ground based measurements were 2.0 mbar for a 30-m resolution and a 100-shot average.

Standoff analysis of laser-produced plasmas using laser-induced fluorescence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harilal, S. S.; Brumfield, B. E.; Phillips, M. C.

We report the use of laser-induced fluorescence (LIF) of laser ablation plumes for standoff applications. The standoff analysis of Al species, as major and minor species in samples, is performed in a nanosecond laser-produced plasma created at a distance ~10 m. The LIF analysis is performed by resonantly exciting an Al transition at 394.4 nm using a continuous wave (cw) tunable laser and by collecting the direct-line fluorescence signal at 396.15 nm. The spectral resolution of LIF is obtained by scanning the cw tunable LIF laser across the selected Al transition. Our results highlight that LIF provides enhanced signal intensity,more » emission persistence, and spectral resolution when compared to thermally-excited emission, and these are crucial considerations for using laser-produced plasma for standoff isotopic analysis.« less

Photoresist Design for Elastomeric Light Tunable Photonic Devices

PubMed Central

Nocentini, Sara; Martella, Daniele; Parmeggiani, Camilla; Wiersma, Diederik S.

2016-01-01

An increasing interest in tunable photonic structures is growing within the photonic community. The usage of Liquid Crystalline Elastomer (LCE) structures in the micro-scale has been motivated by the potential to remotely control their properties. In order to design elastic photonic structures with a three-dimensional lithographic technique, an analysis of the different mixtures used in the micro-printing process is required. Previously reported LCE microstructures suffer damage and strong swelling as a limiting factor of resolution. In this article, we reported a detailed study on the writing process with four liquid crystalline photoresists, in which the percentage of crosslinker is gradually increased. The experiments reveal that exploiting the crosslinking degree is a possible means in which to obtain suspended lines with good resolution, quite good rigidity, and good elasticity, thereby preserving the possibility of deformation by light irradiation. PMID:28773646

Photoresist Design for Elastomeric Light Tunable Photonic Devices.

PubMed

Nocentini, Sara; Martella, Daniele; Parmeggiani, Camilla; Wiersma, Diederik S

2016-06-29

An increasing interest in tunable photonic structures is growing within the photonic community. The usage of Liquid Crystalline Elastomer (LCE) structures in the micro-scale has been motivated by the potential to remotely control their properties. In order to design elastic photonic structures with a three-dimensional lithographic technique, an analysis of the different mixtures used in the micro-printing process is required. Previously reported LCE microstructures suffer damage and strong swelling as a limiting factor of resolution. In this article, we reported a detailed study on the writing process with four liquid crystalline photoresists, in which the percentage of crosslinker is gradually increased. The experiments reveal that exploiting the crosslinking degree is a possible means in which to obtain suspended lines with good resolution, quite good rigidity, and good elasticity, thereby preserving the possibility of deformation by light irradiation.

Tunable All Reflective Spatial Heterodyne Spectroscopy, A Technique For High Resolving Power Observation OI Defused Emission Line Sources

NASA Astrophysics Data System (ADS)

Hosseini, Seyedeh Sona

The solar system presents a challenge to spectroscopic observers, because it is an astrophysically low energy environment populated with often angularly extended targets (e.g, interplanetary medium, comets, planetary upper atmospheres, and planet and satellite near space environments). Spectroscopy is a proven tool for determining compositional and other properties of remote objects. Narrow band imaging and low resolving spectroscopic measurements provide information about composition, photochemical evolution, energy distribution and density. The extension to high resolving power provides further access to temperature, velocity, isotopic ratios, separation of blended sources, and opacity effects. The drawback of high-resolution spectroscopy comes from the instrumental limitations of lower throughput, the necessity of small entrance apertures, sensitivity, field of view, and large physical instrumental size. These limitations quickly become definitive for faint and/or extended targets and for spacecraft encounters. An emerging technique with promise for the study of faint, extended sources at high resolving power is the all-reflective form of the Spatial Heterodyne Spectrometer (SHS). SHS instruments are compact and naturally possess both high etendue and high resolving power. To achieve similar spectral grasp, grating spectrometers require big telescopes. SHS is a common-path beam Fourier transform interferometer that produces Fizeau fringe pattern for all other wavelengths except the tuned wavelength. Compared to similar Fourier transform Spectrometers (FTS), SHS has considerably relaxed optical tolerances that make it easier to use in the visible and UV spectral ranges. The large etendue of SHS instruments makes them ideal for observations of extended, low surface brightness, isolated emission line sources, while their intrinsically high spectral resolution enables the study of the dynamical and spectral characteristics described above. SHS also combines very high (R >105) spectral resolution and large etendue in a small package that is compatible with space mission requirements that have not been met with any other SHS technologies to date. One limitation of current SHS designs is the lack of a broadband capability. To address this gap we are developing a form of the reflective SHS that is tunable over a wide range of wavelength (TSHS). In this work, we describe the primary TSHS concept in a mathematical approach, describe the variations under development, and discuss their scientific potential for the exploration of faint extended targets. An in-development laboratory prototype of a second generation TSHS in which we address several technical limitations noted in earlier studies is shown. This document contains three chapters. Chapter 1, is an overview of the scientific need for a new instrument that we are introducing here and it is an summery of previous papers. Chapter 2 contains new work developing the mathematical frame work for the all reflective SHS. The results presented in this chapter have not been reported in any related literature before and will be presented in an upcoming conference paper. Chapter 3 contains a laboratory report for construction of a tunable all reflective SHS.

Multi-spectral digital holographic microscopy for enhanced quantitative phase imaging of living cells

NASA Astrophysics Data System (ADS)

Kemper, Björn; Kastl, Lena; Schnekenburger, Jürgen; Ketelhut, Steffi

2018-02-01

Main restrictions of using laser light in digital holographic microscopy (DHM) are coherence induced noise and parasitic reflections in the experimental setup which limit resolution and measurement accuracy. We explored, if coherence properties of partial coherent light sources can be generated synthetically utilizing spectrally tunable lasers. The concept of the method is demonstrated by label-free quantitative phase imaging of living pancreatic tumor cells and utilizing an experimental configuration including a commercial microscope and a laser source with a broad tunable spectral range of more than 200 nm.

High resolution absorption cross sections for the A2Pi-X2Pi system of ClO

NASA Technical Reports Server (NTRS)

Wine, P. H.; Ravishankara, A. R.; Philen, D. L.; Davis, D. D.; Watson, R. T.

1977-01-01

High-resolution ultraviolet absorption cross-sections for the ClO molecule are obtained, with the aim of facilitating studies of ozone depletion resulting from the injection of chlorofluorocarbons into the atmosphere. The spectroscopic analysis, which involves a frequency-doubled tunable dye laser with a bandwidth of 0.015 A, is described. Studies of the rotational lines of the ClO A 2Pi 3/2-X2Pi 3/2 9-10 band were conducted. Peak cross-sections for the P and R lines of the 9-0 band are found to be 10.0, 9.6, 8.6, 10.6, 10.3, and 9.2 times ten to the negative seventeenth power cm squared, with estimated accuracy of plus or minus 25%. Problems in distinguishing between Cl-35 and Cl-37 absorption are also considered.

Theory of high-resolution tunneling spin transport on a magnetic skyrmion

NASA Astrophysics Data System (ADS)

Palotás, Krisztián; Rózsa, Levente; Szunyogh, László

2018-05-01

Tunneling spin transport characteristics of a magnetic skyrmion are described theoretically in magnetic scanning tunneling microscopy (STM). The spin-polarized charge current in STM (SP-STM) and tunneling spin transport vector quantities, the longitudinal spin current and the spin transfer torque, are calculated in high spatial resolution within the same theoretical framework. A connection between the conventional charge current SP-STM image contrasts and the magnitudes of the spin transport vectors is demonstrated that enables the estimation of tunneling spin transport properties based on experimentally measured SP-STM images. A considerable tunability of the spin transport vectors by the involved spin polarizations is also highlighted. These possibilities and the combined theory of tunneling charge and vector spin transport pave the way for gaining deep insight into electric-current-induced tunneling spin transport properties in SP-STM and to the related dynamics of complex magnetic textures at surfaces.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hartemann, F V; Albert, F; Anderson, S G

Nuclear photonics is an emerging field of research requiring new tools, including high spectral brightness, tunable gamma-ray sources; high photon energy, ultrahigh-resolution crystal spectrometers; and novel detectors. This presentation focuses on the precision linac technology required for Compton scattering gamma-ray light sources, and on the optimization of the laser and electron beam pulse format to achieve unprecedented spectral brightness. Within this context, high-gradient X-band technology will be shown to offer optimal performance in a compact package, when used in conjunction with the appropriate pulse format, and photocathode illumination and interaction laser technologies. The nascent field of nuclear photonics is enabledmore » by the recent maturation of new technologies, including high-gradient X-band electron acceleration, robust fiber laser systems, and hyper-dispersion CPA. Recent work has been performed at LLNL to demonstrate isotope-specific detection of shielded materials via NRF using a tunable, quasi-monochromatic Compton scattering gamma-ray source operating between 0.2 MeV and 0.9 MeV photon energy. This technique is called Fluorescence Imaging in the Nuclear Domain with Energetic Radiation (or FINDER). This work has, among other things, demonstrated the detection of {sup 7}Li shielded by Pb, utilizing gamma rays generated by a linac-driven, laser-based Compton scattering gamma-ray source developed at LLNL. Within this context, a new facility is currently under construction at LLNL, with the goal of generating tunable {gamma}-rays in the 0.5-2.5 MeV photon energy range, at a repetition rate of 120 Hz, and with a peak brightness in the 10{sup 20} photons/(s x mm{sup 2} x mrad{sup 2} x 0.1% bw).« less

Spectral imagery with an acousto-optic tunable filter

NASA Technical Reports Server (NTRS)

Smith, W. Hayden; Schempp, W. V.; Conner, C. P.; Katzka, P.

1987-01-01

.A spectral imager for astronomy and aeronomy has been fabricated using collinear or non-collinear acoustooptic tunable filters (AOTFs). The AOTF provides high transparency, rapid tunability over a wide wavelength range, a capability of varying the bandwidth by more than an order of magnitude, high etendue, and linearly polarized output. Some typical observational applications of acoustooptic tunable filters used in several configurations at astronomical telescopes are demonstrated.

Novel system for picosecond photoemission spectroscopy

NASA Astrophysics Data System (ADS)

Haight, R.; Silberman, J. A.; Lilie, M. I.

1988-09-01

This article describes a laser-based source and detection scheme for performing time-resolved photoemission studies of materials. The pulsed laser source produces intense picosecond pulses of coherent radiation that are nearly continuously tunable from the near infrared to photon energies up to 13 eV. To achieve high sensitivity, a novel multianode time-of-flight spectrometer has been built that generates an angularly resolved intensity versus kinetic energy spectrum with better than 100-meV resolution. The source and detector provide an opportunity to study the electronic dynamics of excited systems on a picosecond time scale.

Tunable self-organization of nanocomposite multilayers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, C. Q.; Pei, Y. T.; Shaha, K. P.

In this letter we report the controlled growth and microstructural evolution of self-assembled nanocomposite multilayers that are induced by surface ion-impingement. The nanoscale structures together with chemical composition, especially at the growing front, have been investigated with high-resolution transmission electron microscopy. Concurrent ion impingement of growing films produces an amorphous capping layer 3 nm in thickness where spatially modulated phase separation is initiated. It is shown that the modulation of multilayers as controlled by the self-organization of nanocrystallites below the capping layer, can be tuned through the entire film.

Wavelength-division and spatial multiplexing using tandem interferometers for Bragg grating sensor networks

NASA Astrophysics Data System (ADS)

Kalli, K.; Brady, G. P.; Webb, D. J.; Jackson, D. A.; Zhang, L.; Bennion, I.

1995-12-01

We present a new method for the interrogation of large arrays of Bragg grating sensors. Eight gratings operating between the wavelengths of 1533 and 1555 nm have been demultiplexed. An unbalanced Mach-Zehnder interferometer illuminated by a single low-coherence source provides a high-phase-resolution output for each sensor, the outputs of which are sequentially selected in wavelength by a tunable Fabry-Perot interferometer. The minimum detectable strain measured was 90 n 3 / \\radical Hz \\end-radical at 7 Hz for a wavelength of 1535 nm.

Enhanced structural color generation in aluminum metamaterials coated with a thin polymer layer

DOE PAGES

Cheng, Fei; Yang, Xiaodong; Rosenmann, Daniel; ...

2015-09-18

A high-resolution and angle-insensitive structural color generation platform is demonstrated based on triple-layer aluminum-silica-aluminum metamaterials supporting surface plasmon resonances tunable across the entire visible spectrum. The color performances of the fabricated aluminum metamaterials can be strongly enhanced by coating a thin transparent polymer layer on top. The results show that the presence of the polymer layer induces a better impedance matching for the plasmonic resonances to the free space so that strong light absorption can be obtained, leading to the generation of pure colors in cyan, magenta, yellow and black (CMYK) with high color saturation.

High-power quantum-dot tapered tunable external-cavity lasers based on chirped and unchirped structures.

PubMed

Haggett, Stephanie; Krakowski, Michel; Montrosset, Ivo; Cataluna, Maria Ana

2014-09-22

A high-power tunable external cavity laser configuration with a tapered quantum-dot semiconductor optical amplifier at its core is presented, enabling a record output power for a broadly tunable semiconductor laser source in the 1.2 - 1.3 µm spectral region. Two distinct optical amplifiers are investigated, using either chirped or unchirped quantum-dot structures, and their merits are compared, considering the combination of tunability and high output power generation. At 1230 nm, the chirped quantum-dot laser achieved a maximum power of 0.62 W and demonstrated nearly 100-nm tunability. The unchirped laser enabled a tunability range of 32 nm and at 1254 nm generated a maximum power of 0.97 W, representing a 22-fold increase in output power compared with similar narrow-ridge external-cavity lasers at the same current density.

Tunable Reflective Spatial Heterodyne Spectrometer: A Technique for High Resolving Power, Wide Field Of View Observation Of Diffuse Emission Line Sources

NASA Astrophysics Data System (ADS)

Hosseini, Seyedeh Sona

The purpose of this dissertation is to discuss the need for new technology in broadband high-resolution spectroscopy based on the emerging technique of Spatial Heterodyne Spectroscopy (SHS) and to propose new solutions that should enhance and generalize this technology to other fields. Spectroscopy is a proven tool for determining compositional and other properties of remote objects. Narrow band imaging and low resolving spectroscopic measurements provide information about composition, photochemical evolution, energy distribution and density. The extension to high resolving power provides further access to temperature, velocity, isotopic ratios, separation of blended sources, and opacity effects. In current high resolving power devices, the drawback of high-resolution spectroscopy is bound to the instrumental limitations of lower throughput, the necessity of small entrance apertures, sensitivity, field of view, and large physical instrumental size. These limitations quickly become handicapping for observation of faint and/or extended targets and for spacecraft encounters. A technique with promise for the study of faint and extended sources at high resolving power is the reflective format of the Spatial Heterodyne Spectrometer (SHS). SHS instruments are compact and naturally tailored for both high etendue (defined in section 2.2.5) and high resolving power. In contrast, to achieve similar spectral grasp, grating spectrometers require large telescopes. For reference, SHS is a cyclical interferometer that produces Fizeau fringe pattern for all other wavelengths except the tuned wavelength. The large etendue obtained by SHS instruments makes them ideal for observations of extended, low surface brightness, isolated emission line sources, while their intrinsically high spectral resolution enables one to study the dynamical and physical properties described above. This document contains four chapters. Chapter 1, introduces a class of scientific targets that formerly have not been extensively observed due to absence of technical capabilities in current apparatus. We will introduce the concept of Special Heterodyne Spectrometers and address how it can fill the gap. Chapter 2 reports on the development of a new mathematical frame work for the Reflective SHS. Chapter 3 provides the details of the design and construction of a Tunable Reflective SHS at both UC Davis laboratory and Mt. Hamilton, Lick Observatory, CA. And chapter 4 contains an overview of the prospects of SHS instruments in future.

Field propagation-induced directionality of carrier-envelope phase-controlled photoemission from nanospheres

DOE PAGES

SuBmann, F.; Seiffert, L.; Zherebtsov, S.; ...

2015-08-12

Near-fields of non-resonantly laser-excited nanostructures enable strong localization of ultrashort light fields and have opened novel routes to fundamentally modify and control electronic strong-field processes. Harnessing spatiotemporally tunable near-fields for the steering of sub-cycle electron dynamics may enable ultrafast optoelectronic devices and unprecedented control in the generation of attosecond electron and photon pulses. Here we utilize unsupported sub-wavelength dielectric nanospheres to generate near-fields with adjustable structure and study the resulting strong-field dynamics via photoelectron imaging. We demonstrate field propagation-induced tunability of the emission direction of fast recollision electrons up to a regime, where nonlinear charge interaction effects become dominant inmore » the acceleration process. In conclusion, our analysis supports that the timing of the recollision process remains controllable with attosecond resolution by the carrier-envelope phase, indicating the possibility to expand near-field-mediated control far into the realm of high-field phenomena.« less

Field propagation-induced directionality of carrier-envelope phase-controlled photoemission from nanospheres

DOE Office of Scientific and Technical Information (OSTI.GOV)

SuBmann, F.; Seiffert, L.; Zherebtsov, S.

Near-fields of non-resonantly laser-excited nanostructures enable strong localization of ultrashort light fields and have opened novel routes to fundamentally modify and control electronic strong-field processes. Harnessing spatiotemporally tunable near-fields for the steering of sub-cycle electron dynamics may enable ultrafast optoelectronic devices and unprecedented control in the generation of attosecond electron and photon pulses. Here we utilize unsupported sub-wavelength dielectric nanospheres to generate near-fields with adjustable structure and study the resulting strong-field dynamics via photoelectron imaging. We demonstrate field propagation-induced tunability of the emission direction of fast recollision electrons up to a regime, where nonlinear charge interaction effects become dominant inmore » the acceleration process. In conclusion, our analysis supports that the timing of the recollision process remains controllable with attosecond resolution by the carrier-envelope phase, indicating the possibility to expand near-field-mediated control far into the realm of high-field phenomena.« less

Grating-assisted demodulation of interferometric optical sensors.

PubMed

Yu, Bing; Wang, Anbo

2003-12-01

Accurate and dynamic control of the operating point of an interferometric optical sensor to produce the highest sensitivity is crucial in the demodulation of interferometric optical sensors to compensate for manufacturing errors and environmental perturbations. A grating-assisted operating-point tuning system has been designed that uses a diffraction grating and feedback control, functions as a tunable-bandpass optical filter, and can be used as an effective demodulation subsystem in sensor systems based on optical interferometers that use broadband light sources. This demodulation method has no signal-detection bandwidth limit, a high tuning speed, a large tunable range, increased interference fringe contrast, and the potential for absolute optical-path-difference measurement. The achieved 40-nm tuning range, which is limited by the available source spectrum width, 400-nm/s tuning speed, and a step resolution of 0.4 nm, is sufficient for most practical measurements. A significant improvement in signal-to-noise ratio in a fiber Fabry-Perot acoustic-wave sensor system proved that the expected fringe contrast and sensitivity increase.

Large depth of focus dynamic micro integral imaging for optical see-through augmented reality display using a focus-tunable lens.

PubMed

Shen, Xin; Javidi, Bahram

2018-03-01

We have developed a three-dimensional (3D) dynamic integral-imaging (InIm)-system-based optical see-through augmented reality display with enhanced depth range of a 3D augmented image. A focus-tunable lens is adopted in the 3D display unit to relay the elemental images with various positions to the micro lens array. Based on resolution priority integral imaging, multiple lenslet image planes are generated to enhance the depth range of the 3D image. The depth range is further increased by utilizing both the real and virtual 3D imaging fields. The 3D reconstructed image and the real-world scene are overlaid using an optical see-through display for augmented reality. The proposed system can significantly enhance the depth range of a 3D reconstructed image with high image quality in the micro InIm unit. This approach provides enhanced functionality for augmented information and adjusts the vergence-accommodation conflict of a traditional augmented reality display.

Piezo activated mode tracking system for widely tunable mode-hop-free external cavity mid-IR semiconductor lasers

NASA Technical Reports Server (NTRS)

Tittel, Frank K. (Inventor); Curl, Robert F. (Inventor); Wysocki, Gerard (Inventor)

2010-01-01

A widely tunable, mode-hop-free semiconductor laser operating in the mid-IR comprises a QCL laser chip having an effective QCL cavity length, a diffraction grating defining a grating angle and an external cavity length with respect to said chip, and means for controlling the QCL cavity length, the external cavity length, and the grating angle. The laser of claim 1 wherein said chip may be tuned over a range of frequencies even in the absence of an anti-reflective coating. The diffraction grating is controllably pivotable and translatable relative to said chip and the effective QCL cavity length can be adjusted by varying the injection current to the chip. The laser can be used for high resolution spectroscopic applications and multi species trace-gas detection. Mode-hopping is avoided by controlling the effective QCL cavity length, the external cavity length, and the grating angle so as to replicate a virtual pivot point.

Ultrafast fluorescence imaging in vivo with conjugated polymer fluorophores in the second near-infrared window

NASA Astrophysics Data System (ADS)

Hong, Guosong; Zou, Yingping; Antaris, Alexander L.; Diao, Shuo; Wu, Di; Cheng, Kai; Zhang, Xiaodong; Chen, Changxin; Liu, Bo; He, Yuehui; Wu, Justin Z.; Yuan, Jun; Zhang, Bo; Tao, Zhimin; Fukunaga, Chihiro; Dai, Hongjie

2014-06-01

In vivo fluorescence imaging in the second near-infrared window (1.0-1.7 μm) can afford deep tissue penetration and high spatial resolution, owing to the reduced scattering of long-wavelength photons. Here we synthesize a series of low-bandgap donor/acceptor copolymers with tunable emission wavelengths of 1,050-1,350 nm in this window. Non-covalent functionalization with phospholipid-polyethylene glycol results in water-soluble and biocompatible polymeric nanoparticles, allowing for live cell molecular imaging at >1,000 nm with polymer fluorophores for the first time. Importantly, the high quantum yield of the polymer allows for in vivo, deep-tissue and ultrafast imaging of mouse arterial blood flow with an unprecedented frame rate of >25 frames per second. The high time-resolution results in spatially and time resolved imaging of the blood flow pattern in cardiogram waveform over a single cardiac cycle (~200 ms) of a mouse, which has not been observed with fluorescence imaging in this window before.

Continuously Tunable, Polarization Controlled, Colour Palette Produced from Nanoscale Plasmonic Pixels.

PubMed

Balaur, Eugeniu; Sadatnajafi, Catherine; Kou, Shan Shan; Lin, Jiao; Abbey, Brian

2016-06-17

Colour filters based on nano-apertures in thin metallic films have been widely studied due to their extraordinary optical transmission and small size. These properties make them prime candidates for use in high-resolution colour displays and high accuracy bio-sensors. The inclusion of polarization sensitive plasmonic features in such devices allow additional control over the electromagnetic field distribution, critical for investigations of polarization induced phenomena. Here we demonstrate that cross-shaped nano-apertures can be used for polarization controlled color tuning in the visible range and apply fundamental theoretical models to interpret key features of the transmitted spectrum. Full color transmission was achieved by fine-tuning the periodicity of the apertures, whilst keeping the geometry of individual apertures constant. We demonstrate this effect for both transverse electric and magnetic fields. Furthermore we have been able to demonstrate the same polarization sensitivity even for nano-size, sub-wavelength sets of arrays, which is paramount for ultra-high resolution compact colour displays.

Continuously Tunable, Polarization Controlled, Colour Palette Produced from Nanoscale Plasmonic Pixels

PubMed Central

Balaur, Eugeniu; Sadatnajafi, Catherine; Kou, Shan Shan; Lin, Jiao; Abbey, Brian

2016-01-01

Colour filters based on nano-apertures in thin metallic films have been widely studied due to their extraordinary optical transmission and small size. These properties make them prime candidates for use in high-resolution colour displays and high accuracy bio-sensors. The inclusion of polarization sensitive plasmonic features in such devices allow additional control over the electromagnetic field distribution, critical for investigations of polarization induced phenomena. Here we demonstrate that cross-shaped nano-apertures can be used for polarization controlled color tuning in the visible range and apply fundamental theoretical models to interpret key features of the transmitted spectrum. Full color transmission was achieved by fine-tuning the periodicity of the apertures, whilst keeping the geometry of individual apertures constant. We demonstrate this effect for both transverse electric and magnetic fields. Furthermore we have been able to demonstrate the same polarization sensitivity even for nano-size, sub-wavelength sets of arrays, which is paramount for ultra-high resolution compact colour displays. PMID:27312072

A fiber-optic interferometer with subpicometer resolution for dc and low-frequency displacement measurement.

PubMed

Smith, D T; Pratt, J R; Howard, L P

2009-03-01

We have developed a fiber-optic interferometer optimized for best performance in the frequency range from dc to 1 kHz, with displacement linearity of 1% over a range of +/- 25 nm, and noise-limited resolution of 2 pm. The interferometer uses a tunable infrared laser source (nominal 1550 nm wavelength) with high amplitude and wavelength stability, low spontaneous self-emission noise, high sideband suppression, and a coherence control feature that broadens the laser linewidth and dramatically lowers the low-frequency noise in the system. The amplitude stability of the source, combined with the use of specially manufactured "bend-insensitive" fiber and all-spliced fiber construction, results in a robust homodyne interferometer system, which achieves resolution of 40 fm Hz(-1/2) above 20 Hz and approaches the shot-noise-limit of 20 fm Hz(-1/2) at 1 kHz for an optical power of 10 microW, without the need for differential detection. Here we describe the design and construction of the interferometer, as well as modes of operation, and demonstrate its performance.

High Resolution Spectroscopy to Support Atmospheric Measurements

NASA Technical Reports Server (NTRS)

Benner, D. Chris; Venkataraman, Malathy Devi

2000-01-01

The major research activities performed during the cooperative agreement enhanced our spectroscopic knowledge of molecules of atmospheric interest such as carbon dioxide, water vapor, ozone, methane, and carbon monoxide, to name a few. Measurements were made using the NASA Langley Tunable Diode Laser Spectrometer System (TDL) and several Fourier Transform Spectrometer Systems (FTS) around the globe. The results from these studies made remarkable improvements in the line positions and intensities for several molecules, particularly ozone and carbon dioxide in the 2 to 17-micrometer spectral region. Measurements of pressure broadening and pressure induced line shift coefficients and the temperature dependence of pressure broadening and pressure induced line shift coefficients for infrared transitions of ozone, methane, and water vapor were also performed. Results from these studies have been used for retrievals of stratospheric gas concentration profiles from data collected by several Upper Atmospheric Research satellite (UARS) infrared instruments as well as in the analysis of high resolution atmospheric spectra such as those acquired by space-based, ground-based, and various balloon- and aircraft-borne experiments. Our results made significant contributions in several updates of the HITRAN (HIgh resolution TRANsmission) spectral line parameters database. This database enjoys worldwide recognition in research involving diversified scientific fields.

High Resolution Spectroscopy to Support Atmospheric Measurements

NASA Technical Reports Server (NTRS)

Benner, D. Chris; Venkataraman, Malathy Devi

2000-01-01

The major research activities performed during the cooperative agreement enhanced our spectroscopic knowledge of molecules of atmospheric interest such as carbon dioxide, water vapor, ozone, methane, and carbon monoxide, to name a few. Measurements were made using the NASA Langley Tunable Diode Laser Spectrometer System (TDL) and several Fourier Transform Spectrometer Systems (FTS) around the globe. The results from these studies made remarkable improvements in the line positions and intensities for several molecules, particularly ozone and carbon dioxide in the 2 to 17-micrometer spectral region. Measurements of pressure broadening and pressure induced line shift coefficients and the temperature dependence of pressure broadening and pressure induced line shift coefficients for infrared transitions of ozone, methane, and water vapor were also performed. Results from these studies have been used for retrievals of stratospheric gas concentration profiles from data collected by several Upper Atmospheric Research satellite (UARS) infrared instruments as well as in the analysis of high resolution atmospheric spectra such as those acquired by space-based, ground-based, and various balloon-and aircraft-borne experiments. Our results made significant contributions in several updates of the HITRAN (HIgh resolution TRANsmission) spectral line parameters database. This database enjoys worldwide recognition in research involving diversified scientific fields.

One-step direct-laser metal writing of sub-100 nm 3D silver nanostructures in a gelatin matrix

NASA Astrophysics Data System (ADS)

Kang, SeungYeon; Vora, Kevin; Mazur, Eric

2015-03-01

Developing an ability to fabricate high-resolution, 3D metal nanostructures in a stretchable 3D matrix is a critical step to realizing novel optoelectronic devices such as tunable bulk metal-dielectric optical devices and THz metamaterial devices that are not feasible with alternative techniques. We report a new chemistry method to fabricate high-resolution, 3D silver nanostructures using a femtosecond-laser direct metal writing technique. Previously, only fabrication of 3D polymeric structures or single-/few-layer metal structures was possible. Our method takes advantage of unique gelatin properties to overcome such previous limitations as limited freedom in 3D material design and short sample lifetime. We fabricate more than 15 layers of 3D silver nanostructures with a resolution of less than 100 nm in a stable dielectric matrix that is flexible and has high large transparency that is well-matched for potential applications in the optical and THz metamaterial regimes. This is a single-step process that does not require any further processing. This work will be of interest to those interested in fabrication methods that utilize nonlinear light-matter interactions and the realization of future metamaterials.

Numerical study of low-current steady arcs

NASA Technical Reports Server (NTRS)

Kim, S. C.; Nagamatsu, H. T.

1992-01-01

The development of a high-efficiency CW YLF laser doped with Er,Tm,Ho: and featuring a strongly focusing resonator that collects a high density of pump power on the active crystal is described. The emission is investigated at 2.06 microns and a tuning range both at liquid-nitrogen (77 K) and at dry-ice (210 K) temperature. The noise characteristics and the long-term power stability of the laser is studied with an eye to employing this source for high-resolution spectroscopy in the 2-micron wavelength region. The detection of several absorption lines of NH3 at low pressure is described. The output power of the laser as a function of the power impinging on the crystal for different transmission of the output mirror is illustrated. The best result obtained is 1.46 W output for 3.2 W of argon pump. The minimum threshold achieved is 3.5 mW with a 1-percent transmission mirror. It is concluded that it is possible to develop a highly efficient Ho:YLF laser featuring low noise and sufficient tunability for high-resolution spectroscopy in the 2-micron region.

High refractive index immersion liquid for superresolution 3D imaging using sapphire-based aplanatic numerical aperture increasing lens optics.

PubMed

Laskar, Junaid M; Shravan Kumar, P; Herminghaus, Stephan; Daniels, Karen E; Schröter, Matthias

2016-04-20

Optically transparent immersion liquids with refractive index (n∼1.77) to match the sapphire-based aplanatic numerical aperture increasing lens (aNAIL) are necessary for achieving deep 3D imaging with high spatial resolution. We report that antimony tribromide (SbBr₃) salt dissolved in liquid diiodomethane (CH₂I₂) provides a new high refractive index immersion liquid for optics applications. The refractive index is tunable from n=1.74 (pure) to n=1.873 (saturated), by adjusting either salt concentration or temperature; this allows it to match (or even exceed) the refractive index of sapphire. Importantly, the solution gives excellent light transmittance in the ultraviolet to near-infrared range, an improvement over commercially available immersion liquids. This refractive-index-matched immersion liquid formulation has enabled us to develop a sapphire-based aNAIL objective that has both high numerical aperture (NA=1.17) and long working distance (WD=12  mm). This opens up new possibilities for deep 3D imaging with high spatial resolution.

Development of a tunable femtosecond stimulated raman apparatus and its application to beta-carotene.

PubMed

Shim, Sangdeok; Mathies, Richard A

2008-04-17

We have developed a tunable femtosecond stimulated Raman spectroscopy (FSRS) apparatus and used it to perform time-resolved resonance Raman experiments with <100 fs temporal and <35 cm(-1) spectral resolution. The key technical change that facilitates this advance is the use of a tunable narrow-bandwidth optical parametric amplifier (NB-OPA) presented recently by Shim et al. (Shim, S.; Mathies, R. A. Appl. Phys. Lett. 2006, 89, 121124). The practicality of tunable FSRS is demonstrated by examining the photophysical dynamics of beta-carotene. Using 560 nm Raman excitation, the resonant S1 state modes are enhanced by a factor of approximately 200 compared with 800 nm FSRS experiments. The improved signal-to-noise ratios facilitate the measurement of definitive time constants for beta-carotene dynamics including the 180 fs appearance of the S1 vibrational features due to direct internal conversion from S2 and their characteristic 9 ps decay to S0. By tuning the FSRS system to 590 nm Raman excitation, we are able to selectively enhance vibrational features of the hot ground state S hot 0 and monitor its approximately 5 ps cooling dynamics. This tunable FSRS system is valuable because it facilitates the direct observation of structural changes of selected resonantly enhanced states and intermediates during photochemical and photobiological reactions.

Large-area synthesis of monolayered MoS(2(1-x))Se(2x) with a tunable band gap and its enhanced electrochemical catalytic activity.

PubMed

Yang, Lei; Fu, Qi; Wang, Wenhui; Huang, Jian; Huang, Jianliu; Zhang, Jingyu; Xiang, Bin

2015-06-21

"Band gap engineering" in two-dimensional (2D) materials plays an important role in tailoring their physical and chemical properties. The tuning of the band gap is typically achieved by controlling the composition of the semiconductor alloys. However, large-area preparation of 2D alloys remains a major challenge. Here, we report the large-area synthesis of high-quality monolayered MoS2(1-x)Se2x with a size coverage of hundreds of microns using a chemical vapor deposition method. The photoluminescence (PL) spectroscopy results confirm the tunable band gap in MoS2(1-x)Se2x, which is modulated by varying the Se content. Atomic-scale analysis was performed and the chemical composition was characterized using high-resolution scanning transmission electron microscopy and X-ray photoemission spectroscopy. With the introduction of Se into monolayered MoS2, it leads to enhanced catalytic activity in an electrochemical reaction for hydrogen generation, compared to monolayered MoS2 and MoSe2. It is promising as a potential alternative to expensive noble metals.

A Novel, Poly-Etalon, Fabry-Perot for Planetary Research

NASA Technical Reports Server (NTRS)

Kerr, Robert B.; Doe, Richard; Noto, John

1997-01-01

In an effort to develop a mechanically robust, high throughput and solid state spectrometer several liquid crystal Fabry-Perot etalons were constructed. The etalons were tested for spectral response, radiation resistance and optical transmission. The first year of this project was spent developing and understanding the properties of the liquid crystal etalons; in the second year an intensified all-sky imaging system was developed around a pair of LC etalons. The imaging system, developed jointly with SRI International represents a unique brassboard to demonstrate the use of LC etalons as tunable filters. The first set of etalons constructed in year one of this project were tested for spectral response and throughput while etalon surrogates were exposed to proton radiation simulating the exposure of an object in Low Earth Orbit (LEO). The 2" diameter etalons had a measure finesse of approximately 10 and were tunable over five orders. Liquid crystals exposed to proton irradiation showed no signs of damage. In year two two larger diameter (3") etalons were constructed with gaps of 3 and 5 microns. This pair of etalons is for use in a high resolution, all-sky spectral imager. The WATUMI imager system follows the heritage of all sky, narrow band, intensified imagers however it includes two LC Fabry-Perot etalons to provide tunability and the ability to switch wavelengths rapidly, an import consideration in auroral airglow imaging. This work also resulted in two publications and one poster presentation. The instrument will be uniquely capable, with superior throughput and speed, to measure optical airglow of multiple emission lines in harsh conditions.

CITIUS: An infrared-extreme ultraviolet light source for fundamental and applied ultrafast science

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grazioli, C.; Gauthier, D.; Ivanov, R.

2014-02-15

We present the main features of CITIUS, a new light source for ultrafast science, generating tunable, intense, femtosecond pulses in the spectral range from infrared to extreme ultraviolet (XUV). The XUV pulses (about 10{sup 5}-10{sup 8} photons/pulse in the range 14-80 eV) are produced by laser-induced high-order harmonic generation in gas. This radiation is monochromatized by a time-preserving monochromator, also allowing one to work with high-resolution bandwidth selection. The tunable IR-UV pulses (10{sup 12}-10{sup 15} photons/pulse in the range 0.4-5.6 eV) are generated by an optical parametric amplifier, which is driven by a fraction of the same laser pulse thatmore » generates high order harmonics. The IR-UV and XUV pulses follow different optical paths and are eventually recombined on the sample for pump-probe experiments. We also present the results of two pump-probe experiments: with the first one, we fully characterized the temporal duration of harmonic pulses in the time-preserving configuration; with the second one, we demonstrated the possibility of using CITIUS for selective investigation of the ultra-fast dynamics of different elements in a magnetic compound.« less

Fault detection technique for wavelength division multiplexing passive optical network using chaotic fiber laser

NASA Astrophysics Data System (ADS)

Xu, Naijun; Yang, Lingzhen; Zhang, Juan; Zhang, Xiangyuan; Wang, Juanfen; Zhang, Zhaoxia; Liu, Xianglian

2014-03-01

We propose a fault localization method for wavelength division multiplexing passive optical network (WDM-PON). A proof-of-concept experiment was demonstrated by utilizing the wavelength tunable chaotic laser generated from an erbium-doped fiber ring laser with a manual tunable fiber Bragg grating (TFBG) filter. The range of the chaotic lasing wavelength can cover the C-band. Basing on the TFBG filter, we can adjust the wavelength of the chaotic laser to match the WDM-PON channel with identical wavelength. We determined the fault location by calculating the cross-correlation between the reference and return signals. Analysis of the characteristics of the wavelength tunable chaotic laser showed that the breakpoint, the loose connector, and the mismatch connector could be precisely located. A dynamic range of approximately 23.8 dB and a spatial resolution of 4 cm, which was independent of the measuring range, were obtained.

Near-field spectroscopic investigation of dual-band heavy fermion metamaterials.

PubMed

Gilbert Corder, Stephanie N; Chen, Xinzhong; Zhang, Shaoqing; Hu, Fengrui; Zhang, Jiawei; Luan, Yilong; Logan, Jack A; Ciavatti, Thomas; Bechtel, Hans A; Martin, Michael C; Aronson, Meigan; Suzuki, Hiroyuki S; Kimura, Shin-Ichi; Iizuka, Takuya; Fei, Zhe; Imura, Keiichiro; Sato, Noriaki K; Tao, Tiger H; Liu, Mengkun

2017-12-22

Broadband tunability is a central theme in contemporary nanophotonics and metamaterials research. Combining metamaterials with phase change media offers a promising approach to achieve such tunability, which requires a comprehensive investigation of the electromagnetic responses of novel materials at subwavelength scales. In this work, we demonstrate an innovative way to tailor band-selective electromagnetic responses at the surface of a heavy fermion compound, samarium sulfide (SmS). By utilizing the intrinsic, pressure sensitive, and multi-band electron responses of SmS, we create a proof-of-principle heavy fermion metamaterial, which is fabricated and characterized using scanning near-field microscopes with <50 nm spatial resolution. The optical responses at the infrared and visible frequency ranges can be selectively and separately tuned via modifying the occupation of the 4f and 5d band electrons. The unique pressure, doping, and temperature tunability demonstrated represents a paradigm shift for nanoscale metamaterial and metasurface design.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gilbert Corder, Stephanie N.; Chen, Xinzhong; Zhang, Shaoqing

Broadband tunability is a central theme in contemporary nanophotonics and metamaterials research. Combining metamaterials with phase change media offers a promising approach to achieve such tunability, which requires a comprehensive investigation of the electromagnetic responses of novel materials at subwavelength scales. In this work, we demonstrate an innovative way to tailor band-selective electromagnetic responses at the surface of a heavy fermion compound, samarium sulfide (SmS). By utilizing the intrinsic, pressure sensitive, and multi-band electron responses of SmS, we create a proof-of-principle heavy fermion metamaterial, which is fabricated and characterized using scanning near-field microscopes with < 50 nm spatial resolution. Themore » optical responses at the infrared and visible frequency ranges can be selectively and separately tuned via modifying the occupation of the 4f and 5d band electrons. The unique pressure, doping, and temperature tunability demonstrated represents a paradigm shift for nanoscale metamaterial and metasurface design.« less

Near-field spectroscopic investigation of dual-band heavy fermion metamaterials

DOE PAGES

Gilbert Corder, Stephanie N.; Chen, Xinzhong; Zhang, Shaoqing; ...

2017-12-22

Broadband tunability is a central theme in contemporary nanophotonics and metamaterials research. Combining metamaterials with phase change media offers a promising approach to achieve such tunability, which requires a comprehensive investigation of the electromagnetic responses of novel materials at subwavelength scales. In this work, we demonstrate an innovative way to tailor band-selective electromagnetic responses at the surface of a heavy fermion compound, samarium sulfide (SmS). By utilizing the intrinsic, pressure sensitive, and multi-band electron responses of SmS, we create a proof-of-principle heavy fermion metamaterial, which is fabricated and characterized using scanning near-field microscopes with < 50 nm spatial resolution. Themore » optical responses at the infrared and visible frequency ranges can be selectively and separately tuned via modifying the occupation of the 4f and 5d band electrons. The unique pressure, doping, and temperature tunability demonstrated represents a paradigm shift for nanoscale metamaterial and metasurface design.« less

Continuously tunable photonic fractional Hilbert transformer using a high-contrast germanium-doped silica-on-silicon microring resonator.

PubMed

Shahoei, Hiva; Dumais, Patrick; Yao, Jianping

2014-05-01

We propose and experimentally demonstrate a continuously tunable fractional Hilbert transformer (FHT) based on a high-contrast germanium-doped silica-on-silicon (SOS) microring resonator (MRR). The propagation loss of a high-contrast germanium-doped SOS waveguide can be very small (0.02 dB/cm) while the lossless bend radius can be less than 1 mm. These characteristics lead to the fabrication of an MRR with a high Q-factor and a large free-spectral range (FSR), which is needed to implement a Hilbert transformer (HT). The SOS MRR is strongly polarization dependent. By changing the polarization direction of the input signal, the phase shift introduced at the center of the resonance spectrum is changed. The tunable phase shift at the resonance wavelength can be used to implement a tunable FHT. A germanium-doped SOS MRR with a high-index contrast of 3.8% is fabricated. The use of the fabricated MRR for the implementation of a tunable FHT with tunable orders at 1, 0.85, 0.95, 1.05, and 1.13 for a Gaussian pulse with the temporal full width at half-maximum of 80 ps is experimentally demonstrated.

Compact fixed wavelength femtosecond oscillators as an add-on for tunable Ti:sapphire lasers extend the range of applications towards multimodal imaging and optogenetics

NASA Astrophysics Data System (ADS)

Hakulinen, T.; Klein, J.

2016-03-01

Two-photon (2P) microscopy based on tunable Ti:sapphire lasers has become a widespread tool for 3D imaging with sub-cellular resolution in living tissues. In recent years multi-photon microscopy with simpler fixed-wavelength femtosecond oscillators using Yb-doped tungstenates as gain material has raised increasing interest in life-sciences, because these lasers offer one order of magnitude more average power than Ti:sapphire lasers in the wavelength range around 1040 nm: Two-photon (2P) excitation of mainly red or yellow fluorescent dyes and proteins (e.g. YFP, mFruit series) simultaneously has been proven with a single IR laser wavelength. A new approach is to extend the usability of existing tunable Titanium sapphire lasers by adding a fixed IR wavelength with an Yb femtosecond oscillator. By that means a multitude of applications for multimodal imaging and optogenetics can be supported. Furthermore fs Yb-lasers are available with a repetition rate of typically 10 MHz and an average power of typically 5 W resulting in pulse energy of typically 500 nJ, which is comparably high for fs-oscillators. This makes them an ideal tool for two-photon spinning disk laser scanning microscopy and holographic patterning for simultaneous photoactivation of large cell populations. With this work we demonstrate that economical, small-footprint Yb fixed-wavelength lasers can present an interesting add-on to tunable lasers that are commonly used in multiphoton microscopy. The Yb fs-lasers hereby offer higher power for imaging of red fluorescent dyes and proteins, are ideally enhancing existing Ti:sapphire lasers with more power in the IR, and are supporting pulse energy and power hungry applications such as spinning disk microscopy and holographic patterning.

Investigation of active regions at high resolution by balloon flights of the Solar Optical Universal Polarimeter (SOUP)

NASA Technical Reports Server (NTRS)

Tarbell, T.; Frank, Z.; Gilbreth, C.; Shine, R.; Title, A.; Topka, K.; Wolfson, J.

1989-01-01

SOUP is a versatile, visible-light solar observatory, built for space or balloon flight. It is designed to study magnetic and velocity fields in the solar atmosphere with high spatial resolution and temporal uniformity, which cannot be achieved from the surface of the earth. The SOUP investigation is carried out by the Lockheed Palo Alto Research Laboratory, under contract to NASA's Marshall Space Flight Center. Co-investigators include staff members at a dozen observatories and universities in the U.S. and Europe. The primary objectives of the SOUP experiment are: to measure vector magnetic and velocity fields in the solar atmosphere with much better spatial resolution than can be achieved from the ground; to study the physical processes that store magnetic energy in active regions and the conditions that trigger its release; and to understand how magnetic flux emerges, evolves, combines, and disappears on spatial scales of 400 to 100,000 km. SOUP is designed to study intensity, magnetic, and velocity fields in the photosphere and low chromosphere with 0.5 arcsec resolution, free of atmospheric disturbances. The instrument includes: a 30 cm Cassegrain telescope; an active mirror for image stabilization; broadband film and TV cameras; a birefringent filter, tunable over 5100 to 6600 A with 0.05 A bandpass; a 35 mm film camera and a digital CCD camera behind the filter; and a high-speed digital image processor.

Investigation of active regions at high resolution by balloon flights of the Solar Optical Universal Polarimeter (SOUP)

NASA Astrophysics Data System (ADS)

Tarbell, T.; Frank, Z.; Gilbreth, C.; Shine, R.; Title, A.; Topka, K.; Wolfson, J.

SOUP is a versatile, visible-light solar observatory, built for space or balloon flight. It is designed to study magnetic and velocity fields in the solar atmosphere with high spatial resolution and temporal uniformity, which cannot be achieved from the surface of the earth. The SOUP investigation is carried out by the Lockheed Palo Alto Research Laboratory, under contract to NASA's Marshall Space Flight Center. Co-investigators include staff members at a dozen observatories and universities in the U.S. and Europe. The primary objectives of the SOUP experiment are: to measure vector magnetic and velocity fields in the solar atmosphere with much better spatial resolution than can be achieved from the ground; to study the physical processes that store magnetic energy in active regions and the conditions that trigger its release; and to understand how magnetic flux emerges, evolves, combines, and disappears on spatial scales of 400 to 100,000 km. SOUP is designed to study intensity, magnetic, and velocity fields in the photosphere and low chromosphere with 0.5 arcsec resolution, free of atmospheric disturbances. The instrument includes: a 30 cm Cassegrain telescope; an active mirror for image stabilization; broadband film and TV cameras; a birefringent filter, tunable over 5100 to 6600 A with 0.05 A bandpass; a 35 mm film camera and a digital CCD camera behind the filter; and a high-speed digital image processor.

Characterizing Scitillation and Cherenkov Light Yield in Water-Based Liquid Scintillators

NASA Astrophysics Data System (ADS)

Land, B. J.; Caravaca, J.; Descamps, F. B.; Orebi Gann, G. D.

2016-03-01

The recent development of Water-based Liquid Scintillator (WbLS) has made it possible to produce scintillating materials with highly tunable light yields and excellent optical clarity. This allows for a straightforward combination of the directional properties of Cherenkov light with the greater energy resolution afforded by the typically brighter scintillation light, which lends itself well to a broad program of neutrino physics. Here we explore the light yields and optical properties of WbLS materials in development for Theia (formerly ASDC) as measured in our benchtop Theia R&D at Berkeley Lab and extrapolate to larger detectors.

Radar image processing of real aperture SLAR data for the detection and identification of iceberg and ship targets

NASA Technical Reports Server (NTRS)

Marthaler, J. G.; Heighway, J. E.

1979-01-01

An iceberg detection and identification system consisting of a moderate resolution Side Looking Airborne Radar (SLAR) interfaced with a Radar Image Processor (RIP) based on a ROLM 1664 computer with a 32K core memory updatable to 64K is described. The system can be operated in high- or low-resolution sampling modes. Specifically designed algorithms are applied to digitized signal returns to provide automatic target detection and location, geometrically correct video image display and data recording. The real aperture Motorola AN/APS-94D SLAR operates in the X-band and is tunable between 9.10 and 9.40 GHz; its output power is 45 kW peak with a pulse repetition rate of 750 pulses per hour. Schematic diagrams of the system are provided, together with preliminary test data.

High Efficient Ultra-Thin Flat Optics Based on Dielectric Metasurfaces

NASA Astrophysics Data System (ADS)

Ozdemir, Aytekin

Metasurfaces which emerged as two-dimensional counterparts of metamaterials, facilitate the realization of arbitrary phase distributions using large arrays with subwavelength and ultra-thin features. Even if metasurfaces are ultra-thin, they still effectively manipulate the phase, amplitude, and polarization of light in transmission or reflection mode. In contrast, conventional optical components are bulky, and they lose their functionality at sub-wavelength scales, which requires conceptually new types of nanoscale optical devices. On the other hand, as the optical systems shrink in size day by day, conventional bulky optical components will have tighter alignment and fabrication tolerances. Since metasurfaces can be fabricated lithographically, alignment can be done during lithographic fabrication, thus eliminating the need for post-fabrication alignments. In this work, various types of metasurface applications are thoroughly investigated for robust wavefront engineering with enhanced characteristics in terms of broad bandwidth, high efficiency and active tunability, while beneficial for application. Plasmonic metasurfaces are not compatible with the CMOS process flow, and, additionally their high absorption and ohmic loss is problematic in transmission based applications. Dielectric metasurfaces, however, offer a strong magnetic response at optical frequencies, and thus they can offer great opportunities for interacting not only with the electric component of a light field, but also with its magnetic component. They show great potential to enable practical device functionalities at optical frequencies, which motivates us to explore them one step further on wavefront engineering and imaging sensor platforms. Therefore, we proposed an efficient ultra-thin flat metalens at near-infrared regime constituted by silicon nanodisks which can support both electric and magnetic dipolar Mie-type resonances. These two dipole resonances can be overlapped at the same frequency by varying the geometric parameters of silicon nanodisks. Having two resonance mechanisms at the same frequency allows us to achieve full (0-2?) phase shift on the transmitted beam. To enable the miniaturization of pixel size for achieving high-resolution, planar, compact-size focal plane arrays (FPAs), we also present and explore the metasurface lens array-based FPAs. The investigated dielectric metasurface lens arrays achieved high focusing efficiency with superior optical crosstalk performance. We see a magnificent application prospect for metasurfaces in enhancing the fill factor and reducing the pixel size of FPAs and CCD, CMOS imaging sensors as well. Moreover, it is of paramount importance to design metasurfaces possessing tunable properties. Thus, we also propose a tunable beam steering device by combining phase manipulating metasurfaces concept and liquid crystals. Tunability feature is implemented by nematic liquid crystals infiltrated into nano holes in SiO2. Using electrically tunable nematic liquid crystals, dynamic beam steering is achieved.

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.

Measurement of temperature and density fluctuations in turbulence using an ultraviolet laser

NASA Technical Reports Server (NTRS)

Massey, G. A.

1984-01-01

Noninvasive measurement of density and temperature fluctuations in turbulent air flow was examined. The approach used fluorescence of oxygen molecules which are selectively excited by a tunable vacuum ultraviolet laser beam. The strength of the fluorescence signal and its dependence on laser wavelength vary with the density and temperature of the air in the laser beam. Because fluorescence can be detected at 90 degrees from the beam propagation direction, spatial resolution in three dimensions, rather than path-integrated measurements can be achieved. With spatial resolutions of the order of a millimeter and at supersonic air velocities it is necessary to perform each measurement in a time of the order of a microsecond; this is possible by by using laser pulses of ten nanosecond duration. In this method atmospheric O2 is excited by the emission of a tunable ArF excimer laser, and the fluorescence, which spans the 210 to 420 range, is detected by an ultraviolet phototube.

Tunable electro-optic filter stack

DOEpatents

Fontecchio, Adam K.; Shriyan, Sameet K.; Bellingham, Alyssa

2017-09-05

A holographic polymer dispersed liquid crystal (HPDLC) tunable filter exhibits switching times of no more than 20 microseconds. The HPDLC tunable filter can be utilized in a variety of applications. An HPDLC tunable filter stack can be utilized in a hyperspectral imaging system capable of spectrally multiplexing hyperspectral imaging data acquired while the hyperspectral imaging system is airborne. HPDLC tunable filter stacks can be utilized in high speed switchable optical shielding systems, for example as a coating for a visor or an aircraft canopy. These HPDLC tunable filter stacks can be fabricated using a spin coating apparatus and associated fabrication methods.

Correlation between tunability and anisotropy in magnetoelectric voltage tunable inductor (VTI).

PubMed

Yan, Yongke; Geng, Liwei D; Zhang, Lujie; Gao, Xiangyu; Gollapudi, Sreenivasulu; Song, Hyun-Cheol; Dong, Shuxiang; Sanghadasa, Mohan; Ngo, Khai; Wang, Yu U; Priya, Shashank

2017-11-22

Electric field modulation of magnetic properties via magnetoelectric coupling in composite materials is of fundamental and technological importance for realizing tunable energy efficient electronics. Here we provide foundational analysis on magnetoelectric voltage tunable inductor (VTI) that exhibits extremely large inductance tunability of up to 1150% under moderate electric fields. This field dependence of inductance arises from the change of permeability, which correlates with the stress dependence of magnetic anisotropy. Through combination of analytical models that were validated by experimental results, comprehensive understanding of various anisotropies on the tunability of VTI is provided. Results indicate that inclusion of magnetic materials with low magnetocrystalline anisotropy is one of the most effective ways to achieve high VTI tunability. This study opens pathway towards design of tunable circuit components that exhibit field-dependent electronic behavior.

In-Plane Electrical Connectivity and Near-Field Concentration of Isolated Graphene Resonators Realized by Ion Beams.

PubMed

Luo, Weiwei; Cai, Wei; Xiang, Yinxiao; Wu, Wei; Shi, Bin; Jiang, Xiaojie; Zhang, Ni; Ren, Mengxin; Zhang, Xinzheng; Xu, Jingjun

2017-08-01

Graphene plasmons provide great opportunities in light-matter interactions benefiting from the extreme confinement and electrical tunability. Structured graphene cavities possess enhanced confinements in 3D and steerable plasmon resonances, potential in applications for sensing and emission control at the nanoscale. Besides graphene boundaries obtained by mask lithography, graphene defects engineered by ion beams have shown efficient plasmon reflections. In this paper, near-field responses of structured graphene achieved by ion beam direct-writing are investigated. Graphene nanoresonators are fabricated easily and precisely with a spatial resolution better than 30 nm. Breathing modes are observed in graphene disks. The amorphous carbons around weaken the response of edge modes in the resonators, but meanwhile render the isolated resonators in-plane electrical connections, where near-fields are proved gate-tunable. The realization of gate-tunable near-fields of graphene 2D resonators opens up tunable near-field couplings with matters. Moreover, graphene nonconcentric rings with engineered near-field confinement distributions are demonstrated, where the quadrupole plasmon modes are excited. Near-field mappings reveal concentrations at the scale of 3.8×10-4λ02 within certain zones which can be engineered. The realization of electrically tunable graphene nanoresonators by ion beam direct-writing is promising for active manipulation of emission and sensing at the nanoscale. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Compact silicon photonic wavelength-tunable laser diode with ultra-wide wavelength tuning range

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kita, Tomohiro, E-mail: tkita@ecei.tohoku.ac.jp; Tang, Rui; Yamada, Hirohito

2015-03-16

We present a wavelength-tunable laser diode with a 99-nm-wide wavelength tuning range. It has a compact wavelength-tunable filter with high wavelength selectivity fabricated using silicon photonics technology. The silicon photonic wavelength-tunable filter with wide wavelength tuning range was realized using two ring resonators and an asymmetric Mach-Zehnder interferometer. The wavelength-tunable laser diode fabricated by butt-joining a silicon photonic filter and semiconductor optical amplifier shows stable single-mode operation over a wide wavelength range.

All-fibre ytterbium laser tunable within 45 nm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdullina, S R; Babin, S A; Vlasov, A A

2007-12-31

A tunable ytterbium-doped fibre laser is fabricated. The laser is tuned by using a tunable fibre Bragg grating (FBG) as a selecting intracavity element. The laser is tunable within 45 nm (from 1063 to 1108 nm) and emits {approx}6 W in the line of width {approx}0.15 nm, the output power and linewidth being virtually invariable within the tuning range. The method is proposed for synchronous tuning the highly reflecting and output FBGs, and a tunable ytterbium all-fibre laser is built. (lasers)

Tunable diode-laser heterodyne spectrometer for remote observations near 8 microns

NASA Technical Reports Server (NTRS)

Glenar, D.; Kostiuk, T.; Jennings, D. E.; Buhl, D.; Mumma, M. J.

1982-01-01

A diode-laser-based, ultrahigh resolution IR heterodyne spectrometer for laboratory and field use has been developed for operation between 7.5 and 8.5 microns. The local oscillator is a PbSe tunable diode laser kept continuously at operating temperatures of 12-60 K using a closed-cycle cooler. The laser output frequency is controlled and stabilized using a high-precision diode current supply, constant temperature controller, and a shock isolator mounted between the refrigerator cold tip and the diode mount. The system largely employs reflecting optics to minimize losses from internal reflection and absorption and to eliminate chromatic effects. Spectral analysis of the diode-laser output between 0 and 1 GHz reveals excess noise at many diode current settings, which limits the IR spectral regions over which useful heterodyne operation can be achieved. Observations have been made of atmospheric N2O, O3, and CH4 between 1170 and 1200/cm, using both a single-frequency swept IF channel and a 64-channel RF spectral line receiver with a total IF coverage of 1600 MHz.

In vivo multiphoton imaging of a diverse array of fluorophores to investigate deep neurovascular structure

PubMed Central

Miller, David R.; Hassan, Ahmed M.; Jarrett, Jeremy W.; Medina, Flor A.; Perillo, Evan P.; Hagan, Kristen; Shams Kazmi, S. M.; Clark, Taylor A.; Sullender, Colin T.; Jones, Theresa A.; Zemelman, Boris V.; Dunn, Andrew K.

2017-01-01

We perform high-resolution, non-invasive, in vivo deep-tissue imaging of the mouse neocortex using multiphoton microscopy with a high repetition rate optical parametric amplifier laser source tunable between λ=1,100 and 1,400 nm. By combining the high repetition rate (511 kHz) and high pulse energy (400 nJ) of our amplifier laser system, we demonstrate imaging of vasculature labeled with Texas Red and Indocyanine Green, and neurons expressing tdTomato and yellow fluorescent protein. We measure the blood flow speed of a single capillary at a depth of 1.2 mm, and image vasculature to a depth of 1.53 mm with fine axial steps (5 μm) and reasonable acquisition times. The high image quality enabled analysis of vascular morphology at depths to 1.45 mm. PMID:28717582

Multimodal Broadband Vibrational Sum Frequency Generation (MM-BB-V-SFG) Spectrometer and Microscope.

PubMed

Lee, Christopher M; Kafle, Kabindra; Huang, Shixin; Kim, Seong H

2016-01-14

A broadband sum frequency generation (BB-SFG) spectrometer with multimodal (MM) capabilities was constructed, which could be routinely reconfigured for tabletop experiments in reflection, transmission, and total internal reflection (TIR) geometries, as well as microscopic imaging. The system was constructed using a Ti:sapphire amplifier (800 nm, pulse width = 85 fs, repetition rate = 2 kHz), an optical parameter amplification (OPA) system for production of broadband IR pulses tunable between 1000 and 4000 cm(-1), and two Fabry-Pérot etalons arranged in series for production of narrowband 800 nm pulses. The key feature allowing the MM operation was the nearly collinear alignment of the visible (fixed, 800 nm) and infrared (tunable, 1000-4000 cm(-1)) pulses which were spatially separated. Physical insights discussed in this paper include the comparison of spectral bandwidth produced with 40 and 85 fs pump beams, the improvement of spectral resolution using etalons, the SFG probe volume in bulk analysis, the normalization of SFG signals, the stitching of multiple spectral segments, and the operation in different modes for air/liquid and adsorbate/solid interfaces, bulk samples, as well as spectral imaging combined with principle component analysis (PCA). The SFG spectral features obtained with the MM-BB-SFG system were compared with those obtained with picosecond-scanning-SFG system and high-resolution BB-SFG system (HR-BB-SFG) for dimethyl sulfoxide, α-pinene, and various samples containing cellulose (purified commercial products, Cladophora cell wall, cotton and flax fibers, and onion epidermis cell wall).

Development of tunable high pressure CO2 laser for lidar measurements of pollutants and wind velocities

NASA Technical Reports Server (NTRS)

Levine, J. S.; Guerra, M.; Javan, A.

1980-01-01

The problem of laser energy extraction at a tunable monochromatic frequency from an energetic high pressure CO2 pulsed laser plasma, for application to remote sensing of atmospheric pollutants by Differential Absorption Lidar (DIAL) and of wind velocities by Doppler Lidar, was investigated. The energy extraction principle analyzed is based on transient injection locking (TIL) at a tunable frequency. Several critical experiments for high gain power amplification by TIL are presented.

[Gas pipeline leak detection based on tunable diode laser absorption spectroscopy].

PubMed

Zhang, Qi-Xing; Wang, Jin-Jun; Liu, Bing-Hai; Cai, Ting-Li; Qiao, Li-Feng; Zhang, Yong-Ming

2009-08-01

The principle of tunable diode laser absorption spectroscopy and harmonic detection technique was introduced. An experimental device was developed by point sampling through small multi-reflection gas cell. A specific line near 1 653. 7 nm was targeted for methane measurement using a distributed feedback diode laser as tunable light source. The linearity between the intensity of second harmonic signal and the concentration of methane was determined. The background content of methane in air was measured. The results show that gas sensors using tunable diode lasers provide a high sensitivity and high selectivity method for city gas pipeline leak detection.

Optical frequency switching scheme for a high-speed broadband THz measurement system based on the photomixing technique.

PubMed

Song, Hajun; Hwang, Sejin; Song, Jong-In

2017-05-15

This study presents an optical frequency switching scheme for a high-speed broadband terahertz (THz) measurement system based on the photomixing technique. The proposed system can achieve high-speed broadband THz measurements using narrow optical frequency scanning of a tunable laser source combined with a wavelength-switchable laser source. In addition, this scheme can provide a larger output power of an individual THz signal compared with that of a multi-mode THz signal generated by multiple CW laser sources. A swept-source THz tomography system implemented with a two-channel wavelength-switchable laser source achieves a reduced time for acquisition of a point spread function and a higher depth resolution in the same amount of measurement time compared with a system with a single optical source.

Enhanced performance configuration for fast-switching deformed helix ferroelectric liquid crystal continuous tunable Lyot filter.

PubMed

Tam, A M W; Qi, G; Srivastava, A K; Wang, X Q; Fan, F; Chigrinov, V G; Kwok, H S

2014-06-10

In this paper, we present a novel design configuration of double DHFLC wave plate continuous tunable Lyot filter, which exhibits a rapid response time of 185 μs, while the high-contrast ratio between the passband and stop band is maintained throughout a wide tunable range. A DHFLC tunable filter with a high-contrast ratio is attractive for realizing high-speed optical processing devices, such as multispectral and hyperspectral imaging systems, real-time remote sensing, field sequential color display, and wavelength demultiplexing in the metro network. In this work, an experimental prototype for a single-stage DHFLC Lyot filter of this design has been fabricated using photoalignment technology. We have demonstrated that the filter has a continuous tunable range of 30 nm for a blue wavelength, 45 nm for a green wavelength, and more than 50 nm for a red wavelength when the applied voltage gradually increases from 0 to 8 V. Within this tunable range, the contrast ratio of the proposed double wave plate configuration is maintained above 20 with small deviation in the transmittance level. Simulation and experimental results showed the proposed double DHFLC wave plate configuration enhances the contrast ratio of the tunable filter and, thus, increases the tunable range of the filter when compared with the Lyot filter using a single DHFLC wave plate. Moreover, we have proposed a polarization insensitive configuration for which the efficiency of the existing prototype can theoretically be doubled by the use of polarization beam splitters.

Broadband high-resolution multi-species CARS in gas-filled hollow-core photonic crystal fiber.

PubMed

Trabold, Barbara M; Hupfer, Robert J R; Abdolvand, Amir; St J Russell, Philip

2017-09-01

We report the use of coherent anti-Stokes Raman spectroscopy (CARS) in gas-filled hollow-core photonic crystal fiber (HC-PCF) for trace gas detection. The long optical path-lengths yield a 60 dB increase in the signal level compared with free-space arrangements. This enables a relatively weak supercontinuum (SC) to be used as Stokes seed, along with a ns pump pulse, paving the way for broadband (>4000  cm -1 ) single-shot CARS with an unprecedented resolution of ∼100  MHz. A kagomé-style HC-PCF provides broadband guidance, and, by operating close to the pressure-tunable zero dispersion wavelength, we can ensure simultaneous phase-matching of all gas species. We demonstrate simultaneous measurement of the concentrations of multiple trace gases in a gas sample introduced into the core of the HC-PCF.

Fluorescence lifetime imaging of induced pluripotent stem cells

NASA Astrophysics Data System (ADS)

Uchugonova, Aisada; Batista, Ana; König, Karsten

2014-02-01

The multiphoton FLIM tomograph MPTflex with its flexible scan head, articulated arm, and the tunable femtosecond laser source was employed to study cell monolayers and 3D cell clusters. FLIM was performed with 250 ps temporal resolution and submicron special resolution using time-correlated single photon counting. The autofluorescence based on NAD(P)H and flavins/flavoproteins has been measured in mouse embryonic fibroblasts, induced pluripotent stem cells (iPS cells) originated from mouse embryonic fibroblasts and non-proliferative mouse embryonic fibroblasts.

Imaging spectrometry - Technology and applications

NASA Technical Reports Server (NTRS)

Solomon, Jerry E.

1989-01-01

The development history and current status of NASA imaging-spectrometer (IS) technology are discussed in a review covering the period 1982-1988. Consideration is given to the Airborne IS first flown in 1982, the second-generation Airborne Visible and IR IS (AVIRIS), the High-Resolution IS being developed for the EOS polar platform, improved two-dimensional focal-plane arrays for the short-wave IR spectral region, and noncollinear acoustooptic tunable filters for use as spectral dispersing elements. Also examined are approaches to solving the data-processing problems posed by the high data volumes of state-of-the-art ISs (e.g., 160 MB per 600 x 600-pixel AVIRIS scene), including intelligent data editing, lossless and lossy data compression techniques, and direct extraction of scientifically meaningful geophysical and biophysical parameters.

Temporal, thermal, and light stability of continuously tunable cholesteric liquid crystal laser array.

PubMed

Jeong, Mi-Yun; Chung, Ki Soo; Wu, Jeong Weon

2014-11-01

Fine-structured polymerized cholesteric liquid crystal (PCLC) wedge laser devices have been realized, with high fine spatial tunability of the lasing wavelength. With resolution less than 0.3 nm in a broad spectral range, more than one hundred laser lines could be obtained in a PCLC cell without extra devices. For practical device application, we studied the stability of the device in detail over time, and in response to strong external light sources, and thermal perturbation. The PCLC wedge cells had good temporal stability for 1 year and showed good stability for strong perturbations, with the lasing wavelength shifting less than 1 nm, while the laser peak intensities decreased by up to 34%, and the high energy band edge of the photonic band gap (PBG) was red shifted 3 nm by temperature perturbation. However, when we consider the entire lasing spectrum for the PCLC cell, the 1-nm wavelength shift may not matter. Although the laser peak intensities were decreased by up to 34% in total for all of the perturbation cases, the remaining 34% laser peak intensity is considerable extent to make use. This good stability of the PCLC laser device is due to the polymerization of the CLC by UV curing. This study will be helpful for practical CLC laser device development.

Wavelength-Scanning SPR Imaging Sensors Based on an Acousto-Optic Tunable Filter and a White Light Laser

PubMed Central

Zeng, Youjun; Wang, Lei; Wu, Shu-Yuen; He, Jianan; Qu, Junle; Li, Xuejin; Ho, Ho-Pui; Gu, Dayong; Gao, Bruce Zhi; Shao, Yonghong

2017-01-01

A fast surface plasmon resonance (SPR) imaging biosensor system based on wavelength interrogation using an acousto-optic tunable filter (AOTF) and a white light laser is presented. The system combines the merits of a wide-dynamic detection range and high sensitivity offered by the spectral approach with multiplexed high-throughput data collection and a two-dimensional (2D) biosensor array. The key feature is the use of AOTF to realize wavelength scan from a white laser source and thus to achieve fast tracking of the SPR dip movement caused by target molecules binding to the sensor surface. Experimental results show that the system is capable of completing a SPR dip measurement within 0.35 s. To the best of our knowledge, this is the fastest time ever reported in the literature for imaging spectral interrogation. Based on a spectral window with a width of approximately 100 nm, a dynamic detection range and resolution of 4.63 × 10−2 refractive index unit (RIU) and 1.27 × 10−6 RIU achieved in a 2D-array sensor is reported here. The spectral SPR imaging sensor scheme has the capability of performing fast high-throughput detection of biomolecular interactions from 2D sensor arrays. The design has no mechanical moving parts, thus making the scheme completely solid-state. PMID:28067766

A tunable single-monochromator Raman system based on the supercontinuum laser and tunable filters for resonant Raman profile measurements.

PubMed

Liu, X-L; Liu, H-N; Tan, P-H

2017-08-01

Resonant Raman spectroscopy requires that the wavelength of the laser used is close to that of an electronic transition. A tunable laser source and a triple spectrometer are usually necessary for resonant Raman profile measurements. However, such a system is complex with low signal throughput, which limits its wide application by scientific community. Here, a tunable micro-Raman spectroscopy system based on the supercontinuum laser, transmission grating, tunable filters, and single-stage spectrometer is introduced to measure the resonant Raman profile. The supercontinuum laser in combination with transmission grating makes a tunable excitation source with a bandwidth of sub-nanometer. Such a system exhibits continuous excitation tunability and high signal throughput. Its good performance and flexible tunability are verified by resonant Raman profile measurement of twisted bilayer graphene, which demonstrates its potential application prospect for resonant Raman spectroscopy.

Self-referenced axial chromatic dispersion measurement in multiphoton microscopy through 2-color THG imaging.

PubMed

Du, Yu; Zhuang, Ziwei; He, Jiexing; Liu, Hongji; Qiu, Ping; Wang, Ke

2018-05-16

With tunable excitation light, multiphoton microscopy (MPM) is widely used for imaging biological structures at subcellular resolution. Axial chromatic dispersion, present in virtually every transmissive optical system including the multiphoton microscope, leads to focal (and the resultant image) plane separation. Here we demonstrate experimentally a technique to measure the axial chromatic dispersion in a multiphoton microscope, using simultaneous 2-color third-harmonic generation (THG) imaging excited by a 2-color soliton source with tunable wavelength separation. Our technique is self-referenced, eliminating potential measurement error when 1-color tunable excitation light is used which necessitates reciprocating motion of the mechanical translation stage. Using this technique, we demonstrate measured axial chromatic dispersion with 2 different objective lenses in a multiphoton microscope. Further measurement in a biological sample also indicates that this axial chromatic dispersion, in combination with 2-color imaging, may open up opportunity for simultaneous imaging of two different axial planes. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

High Si-H local mode overtones in SiHD/sub 3/

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bernheim, R.A.; Lampe, F.W.; O'Keefe, J.F.

1984-01-01

Spectra for SiHD/sub 3/ obtained using a nonresonant photoacoustic cell mounted within the cavity of a CR490 tunable CW laser are reported herein. The symmetric top spectra exhibit partial rotational resolution. A relation for determining the Si-H bond distance is reported, and the Si-D bond distance is taken to be the same as the Si-H distance in the ground vibrational state. The bond angle is assumed to remain tetrahedral in both situations. The noted spectral vibrational band widths arise only from rotational structure with contributions from fast vibrational relaxation not being evident. 10 references, 2 figures, 1 table.

Effect of anisotropic MoS2 nanoparticles on the blue phase range of a chiral liquid crystal.

PubMed

Lavrič, Marta; Cordoyiannis, George; Kralj, Samo; Tzitzios, Vassilios; Nounesis, George; Kutnjak, Zdravko

2013-08-01

Liquid-crystalline blue phases are attracting significant interest due to their potential for applications related to tunable photonic crystals and fast optical displays. In this work a brief theoretical model is presented accounting for the impact of anisotropic nanoparticles on the blue phase stability region. This model is tested by means of high-resolution calorimetric and optical measurements of the effect of anisotropic, surface-functionalized MoS2 nanoparticles on the blue phase range of a chiral liquid crystal. The addition of these nanoparticles effectively increases the temperature range of blue phases and especially the cubic structure of blue phase I.

Tunable X-ray speckle-based phase-contrast and dark-field imaging using the unified modulated pattern analysis approach

NASA Astrophysics Data System (ADS)

Zdora, M.-C.; Thibault, P.; Deyhle, H.; Vila-Comamala, J.; Rau, C.; Zanette, I.

2018-05-01

X-ray phase-contrast and dark-field imaging provides valuable, complementary information about the specimen under study. Among the multimodal X-ray imaging methods, X-ray grating interferometry and speckle-based imaging have drawn particular attention, which, however, in their common implementations incur certain limitations that can restrict their range of applications. Recently, the unified modulated pattern analysis (UMPA) approach was proposed to overcome these limitations and combine grating- and speckle-based imaging in a single approach. Here, we demonstrate the multimodal imaging capabilities of UMPA and highlight its tunable character regarding spatial resolution, signal sensitivity and scan time by using different reconstruction parameters.

Focal plane instrument for the Solar UV-Vis-IR Telescope aboard SOLAR-C

NASA Astrophysics Data System (ADS)

Katsukawa, Yukio; Suematsu, Yoshinori; Shimizu, Toshifumi; Ichimoto, Kiyoshi; Takeyama, Norihide

2011-10-01

It is presented the conceptual design of a focal plane instrument for the Solar UV-Vis-IR Telescope (SUVIT) aboard the next Japanese solar mission SOLAR-C. A primary purpose of the telescope is to achieve precise as well as high resolution spectroscopic and polarimetric measurements of the solar chromosphere with a big aperture of 1.5 m, which is expected to make a significant progress in understanding basic MHD processes in the solar atmosphere. The focal plane instrument consists of two packages: A filtergraph package is to get not only monochromatic images but also Dopplergrams and magnetograms using a tunable narrow-band filter and interference filters. A spectrograph package is to perform accurate spectro-polarimetric observations for measuring chromospheric magnetic fields, and is employing a Littrow-type spectrograph. The most challenging aspect in the instrument design is wide wavelength coverage from 280 nm to 1.1 μm to observe multiple chromospheric lines, which is to be realized with a lens unit including fluoride glasses. A high-speed camera for correlation tracking of granular motion is also implemented in one of the packages for an image stabilization system, which is essential to achieve high spatial resolution and high polarimetric accuracy.

Photoacoustic and Colorimetric Visualization of Latent Fingerprints.

PubMed

Song, Kai; Huang, Peng; Yi, Chenglin; Ning, Bo; Hu, Song; Nie, Liming; Chen, Xiaoyuan; Nie, Zhihong

2015-12-22

There is a high demand on a simple, rapid, accurate, user-friendly, cost-effective, and nondestructive universal method for latent fingerprint (LFP) detection. Herein, we describe a combination imaging strategy for LFP visualization with high resolution using poly(styrene-alt-maleic anhydride)-b-polystyrene (PSMA-b-PS) functionalized gold nanoparticles (GNPs). This general approach integrates the merits of both colorimetric imaging and photoacoustic imaging. In comparison with the previous methods, our strategy is single-step and does not require the signal amplification by silver staining. The PSMA-b-PS functionalized GNPs have good stability, tunable color, and high affinity for universal secretions (proteins/polypeptides/amino acids), which makes our approach general and flexible for visualizing LFPs on different substrates (presumably with different colors) and from different people. Moreover, the unique optical property of GNPs enables the photoacoustic imaging of GNPs-deposited LFPs with high resolution. This allows observation of level 3 hyperfine features of LFPs such as the pores and ridge contours by photoacoustic imaging. This technique can potentially be used to identify chemicals within LFP residues. We believe that this dual-modality imaging of LFPs will find widespread use in forensic investigations and medical diagnostics.

Compact Two-step Laser Time-of-Flight Mass Spectrometer for in Situ Analyses of Aromatic Organics on Planetary Missions

NASA Technical Reports Server (NTRS)

Getty, Stephanie; Brickerhoff, William; Cornish, Timothy; Ecelberger, Scott; Floyd, Melissa

2012-01-01

RATIONALE A miniature time-of-flight mass spectrometer has been adapted to demonstrate two-step laser desorption-ionization (LOI) in a compact instrument package for enhanced organics detection. Two-step LDI decouples the desorption and ionization processes, relative to traditional laser ionization-desorption, in order to produce low-fragmentation conditions for complex organic analytes. Tuning UV ionization laser energy allowed control ofthe degree of fragmentation, which may enable better identification of constituent species. METHODS A reflectron time-of-flight mass spectrometer prototype measuring 20 cm in length was adapted to a two-laser configuration, with IR (1064 nm) desorption followed by UV (266 nm) postionization. A relatively low ion extraction voltage of 5 kV was applied at the sample inlet. Instrument capabilities and performance were demonstrated with analysis of a model polycyclic aromatic hydrocarbon, representing a class of compounds important to the fields of Earth and planetary science. RESULTS L2MS analysis of a model PAH standard, pyrene, has been demonstrated, including parent mass identification and the onset o(tunable fragmentation as a function of ionizing laser energy. Mass resolution m/llm = 380 at full width at half-maximum was achieved which is notable for gas-phase ionization of desorbed neutrals in a highly-compact mass analyzer. CONCLUSIONS Achieving two-step laser mass spectrometry (L2MS) in a highly-miniature instrument enables a powerful approach to the detection and characterization of aromatic organics in remote terrestrial and planetary applications. Tunable detection of parent and fragment ions with high mass resolution, diagnostic of molecular structure, is possible on such a compact L2MS instrument. Selectivity of L2MS against low-mass inorganic salt interferences is a key advantage when working with unprocessed, natural samples, and a mechanism for the observed selectivity is presented.

A multi-plate velocity-map imaging design for high-resolution photoelectron spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kregel, Steven J.; Thurston, Glen K.; Zhou, Jia

A velocity map imaging (VMI) setup consisting of multiple electrodes with three adjustable voltage parameters, designed for slow electron velocity map imaging applications, is presented. The motivations for this design are discussed in terms of parameters that influence the VMI resolution and functionality. Particularly, this VMI has two tunable potentials used to adjust for optimal focus, yielding good VMI focus across a relatively large energy range. It also allows for larger interaction volumes without significant sacrifice to the resolution via a smaller electric gradient at the interaction region. All the electrodes in this VMI have the same dimensions for practicalitymore » and flexibility, allowing for relatively easy modifications to suit different experimental needs. We have coupled this VMI to a cryogenic ion trap mass spectrometer that has a flexible source design. The performance is demonstrated with the photoelectron spectra of S- and CS 2 -. The latter has a long vibrational progression in the ground state, and the temperature dependence of the vibronic features is probed by changing the temperature of the ion trap.« less

A multi-plate velocity-map imaging design for high-resolution photoelectron spectroscopy

DOE PAGES

Kregel, Steven J.; Thurston, Glen K.; Zhou, Jia; ...

2017-09-01

A velocity map imaging (VMI) setup consisting of multiple electrodes with three adjustable voltage parameters, designed for slow electron velocity map imaging applications, is presented. The motivations for this design are discussed in terms of parameters that influence the VMI resolution and functionality. Particularly, this VMI has two tunable potentials used to adjust for optimal focus, yielding good VMI focus across a relatively large energy range. It also allows for larger interaction volumes without significant sacrifice to the resolution via a smaller electric gradient at the interaction region. All the electrodes in this VMI have the same dimensions for practicalitymore » and flexibility, allowing for relatively easy modifications to suit different experimental needs. We have coupled this VMI to a cryogenic ion trap mass spectrometer that has a flexible source design. The performance is demonstrated with the photoelectron spectra of S- and CS 2 -. The latter has a long vibrational progression in the ground state, and the temperature dependence of the vibronic features is probed by changing the temperature of the ion trap.« less

High-efficiency water-loaded microwave antenna in ultra-high-frequency band

NASA Astrophysics Data System (ADS)

Gong, Zilun; Bartone, Chris; Yang, Fuyi; Yao, Jie

2018-03-01

High-index dielectrics are widely used in microwave antennas to control the radiation characteristics. Liquid water, with a high dielectric index at microwave frequency, is an interesting material to achieving tunable functionalities. Here, we demonstrate a water-loaded microwave antenna system that has high loss-tolerance and wideband tunability enabled by fluidity. Our simulation and experimental results show that the resonance frequency can be effectively tuned by the size of loading water. Furthermore, the antenna systems with water loading can achieve high radiation efficiency (>90%) in the ultra-high-frequency (0.3-3 GHz) band. This work brings about opportunities in realistic tunable microwave antenna designs enabled by liquid.

[The design of all solid-state tunable pulsed Ti:sapphire laser system].

PubMed

Chen, Zhe; Ku, Geng; Wan, Junchao; Wang, Wei; Zhou, Chuanqing

2013-05-01

This paper presented a design of broadly all solid-state tunable pulsed Ti:sapphire laser with high power and stable performance. The laser was pumped by custom-made Nd:YAG laser which had water cooling system and amplified by two stage amplifier. The method accomplished tunable output of all solid-state tunable pulsed Ti:sapphire laser by modifying the reflection angle of the back mirror. We investigated the relationship between the power of the pumping laser and the all solid-state tunable pulsed Ti: sapphire laser by changing the power of the pumping source.

Tunable Superconducting Qubits with Flux-Independent Coherence

NASA Astrophysics Data System (ADS)

Hutchings, M. D.; Hertzberg, J. B.; Liu, Y.; Bronn, N. T.; Keefe, G. A.; Brink, Markus; Chow, Jerry M.; Plourde, B. L. T.

2017-10-01

We study the impact of low-frequency magnetic flux noise upon superconducting transmon qubits with various levels of tunability. We find that qubits with weaker tunability exhibit dephasing that is less sensitive to flux noise. This insight is used to fabricate qubits where dephasing due to flux noise is suppressed below other dephasing sources, leading to flux-independent dephasing times T2*˜15 μ s over a tunable range of approximately 340 MHz. Such tunable qubits have the potential to create high-fidelity, fault-tolerant qubit gates and to fundamentally improve scalability for a quantum processor.

Mid-infrared Laser Absorption Diagnostics for Detonation Studies

NASA Astrophysics Data System (ADS)

Spearrin, R. M.; Goldenstein, C. S.; Jeffries, J. B.; Hanson, R. K.

Detonation-based engines represent a challenging application for diagnostics due to the wide range of thermodynamic conditions involved (T~500-3000 K, P~2-60 atm) and the short time scales of change (~10- 6 to 10- 4 sec) associated with such systems. Non-intrusive laser absorption diagnostics can provide high time-resolution and have been employed extensively in shock tube kinetics experiments (P~1-20 atm), offering high potential for application in detonation environments with modest utilization to date [1-4]. Limiting factors in designing effective tunable laser absorption sensors for detonation engines can be divided into two sets of challenges: high-pressure, high-temperature absorption spectroscopy and harsh thermo-mechanical environments. The present work, conducted in a high-pressure shock tube and operating detonation combustor, addresses both sets of difficulties, with the objective of developing time-resolved, in-situ temperature and concentration sensors for detonation studies.

Fast focus-scanning head in two-photon photoacoustic microscopy with electrically controlled liquid lens

NASA Astrophysics Data System (ADS)

Yamaoka, Yoshihisa; Kimura, Yuka; Harada, Yoshinori; Takamatsu, Tetsuro; Takahashi, Eiji

2018-02-01

Conventional one-photon photoacoustic microscopy (PAM) utilizes high-frequency components of generated photoacoustic waves to improve the depth resolution. However, to obtain optically-high resolution in PAM in the depth direction, the use of high-frequency ultrasonic waves is to be avoided. It is because that the propagation distance is shortened as the frequency of ultrasonic waves becomes high. To overcome this drawback, we have proposed and developed two-photon photoacoustic microscopy (TP-PAM). Two-photon absorption occurs only at the focus point. TPPAM does not need to use the high-frequency components of photoacoustic waves. Thus, TP-PAM can improve the penetration depth while preserving the spatial resolution. However, the image acquisition time of TP-PAM is longer than that of conventional PAM, because TP-PAM needs to scan the laser spot both in the depth and transverse directions to obtain cross-sectional images. In this paper, we have introduced a focus-tunable electrically-controlled liquid lens in TP-PAM. Instead of a mechanical stepping-motor stage, we employed electrically-controlled liquid lens so that the depth of the focus spot can be quickly changed. In our system, the imaging speed of TP-PAM using the liquid lens and one-axis stepping-motor stage was 10 times faster than that using a two-axis stepping-motor stage only. TP-PAM with focus-scanning head consisting of the liquid lens and stepping-motor stage will be a promising method to investigate the inside of living tissues.

Tunable all-optical photonic crystal channel drop filter for DWDM systems

NASA Astrophysics Data System (ADS)

Habibiyan, H.; Ghafoori-Fard, H.; Rostami, A.

2009-06-01

In this paper we propose a tunable channel drop filter in a two-dimensional photonic crystal, based on coupled-cavity waveguides with alternating small and large defects and an electromagnetically induced transparency phenomenon. By utilizing this phenomenon a narrower linewidth is obtained and also the frequency of the dropped signal becomes tunable. Simulation results show that the proposed filter is suitable for dense wavelength-division multiplexing (DWDM) systems with 0.8 nm channel spacing. Using this novel component, two ultrasmall eight-channel double-sided and single-sided demultiplexers are introduced. The properties of these devices are investigated using the finite-difference time-domain method. For the single-sided device, transmission loss is 1.5 ± 0.5 dB, the cross-talk level between adjacent channels is better than -18 dB and the average 3 dB optical passband is 0.36 nm. Using planar silicon-on-insulator technology, the physical area for the single-sided component is 700 µm2 and for the double-sided component is 575 µm2. To the best of our knowledge, these are the smallest all-optical demultiplexers with this spectral resolution reported to date. Malfunction of the proposed device due to fabrication errors is modeled and its tunable characteristic is demonstrated.

AOTF-based near-infrared imaging spectrometer for rapid identification of camouflaged target

NASA Astrophysics Data System (ADS)

Gao, Zhifan; Zeng, Libo; Wu, Qiongshui

2014-11-01

Acousto-optic tunable filter (AOTF) is a novel device for spectrometer. The electronic tunability qualifies it with the most compelling advantages of higher wavelength scan rate over the conventional spectrometers that are mechanically tuned, and the feature of large angular aperture makes the AOTF particularly suitable in imaging applications. In this research, an AOTF-based near-infrared imaging spectrometer was developed. The spectrometer consists of a TeO2 AOTF module, a near-infrared imaging lens assembly, an AOTF controller, an InGaAs array detector, an image acquisition card, and a PC. A precisely designed optical wedge is placed at the emergent surface of the AOTF to deal with the inherent dispersion of the TeO2 that may degrade the spatial resolution. The direct digital synthesizer (DDS) techniques and the phase locked loop (PLL) techniques are combined for radio frequency (RF) signal synthesis. The PLL is driven by the DDS to take advantage of both their merits of high frequency resolution, high frequency scan rate and strong spurious signals resistance capability. All the functions relating to wavelength scan, image acquisition, processing, storge and display are controlled by the PC. Calibration results indicate that the spectral range is 898~1670 nm, the spectral resolution is 6.8 nm(@1064 nm), the wavelength separation between frames in the spectral image assembly is 1.0 nm, and the processing time of a single image is less than 1 ms if a TV camera with 640×512 detector is incorporated. A prototype device was assembled to test the capability of differentiating samples with similar appearances, and satisfactory results were achieved. By this device, the chemical compositions and the distribution information can be obtained simultaneously. This system has the most advantages of no moving parts, fast wavelength scan and strong vibration resistance. The proposed imaging spectrometer has a significant application prospect in the area of identification of camouflaged target from complex backgrounds. In addition, only the objective lens and its accessories are required to be replaced for its use in microscopic spectral imaging system, which may be popularized to a large number of other possible applications.

Nanoscale Infrared Spectroscopy of Biopolymeric Materials

Treesearch

Curtis Marcott; Michael Lo; Kevin Kjoller; Craig Prater; Roshan Shetty; Joseph Jakes; Isao Noda

2012-01-01

Atomic Force Microscopy (AFM) and infrared (IR) spectroscopy have been combined in a single instrument capable of producing 100 nm spatial resolution IR spectra and images. This new capability enables the spectroscopic characterization of biomaterial domains at levels not previously possible. A tunable IR laser source generating pulses on the order of 10 ns was used...

Optically Tunable Long Wavelength Infrared Quantum Cascade Laser Operated at Room Temperature

DTIC Science & Technology

2013-01-09

optics (Figure 2(d)). QCL emission spectra were obtained using a FTIR spectrometer with resolution of 0.125 cm1 and a photovoltaic MCT detector . A...frequency modulation (FM) optical data links,1 which can have orders of magnitude higher signal-to- noise ratio compared to the amplitude-modulation (AM

Spectral characterization of near-infrared acousto-optic tunable filter (AOTF) hyperspectral imaging systems using standard calibration materials.

PubMed

Bürmen, Miran; Pernuš, Franjo; Likar, Boštjan

2011-04-01

In this study, we propose and evaluate a method for spectral characterization of acousto-optic tunable filter (AOTF) hyperspectral imaging systems in the near-infrared (NIR) spectral region from 900 nm to 1700 nm. The proposed spectral characterization method is based on the SRM-2035 standard reference material, exhibiting distinct spectral features, which enables robust non-rigid matching of the acquired and reference spectra. The matching is performed by simultaneously optimizing the parameters of the AOTF tuning curve, spectral resolution, baseline, and multiplicative effects. In this way, the tuning curve (frequency-wavelength characteristics) and the corresponding spectral resolution of the AOTF hyperspectral imaging system can be characterized simultaneously. Also, the method enables simple spectral characterization of the entire imaging plane of hyperspectral imaging systems. The results indicate that the method is accurate and efficient and can easily be integrated with systems operating in diffuse reflection or transmission modes. Therefore, the proposed method is suitable for characterization, calibration, or validation of AOTF hyperspectral imaging systems. © 2011 Society for Applied Spectroscopy

Volumetric structured illumination microscopy enabled by tunable focus lens (Conference Presentation)

NASA Astrophysics Data System (ADS)

Hinsdale, Taylor; Malik, Bilal; Olsovsky, Cory; Jo, Javier A.; Maitland, Kristen C.

2016-03-01

We present a volumetric imaging method for biological tissue that is free of mechanically scanning components. The optical sectioning in the system is obtained by structured illumination microscopy (SIM) with the depth of focus being varied by the use of an electronic tunable-focus lens (ETL). The performance of the axial scanning mechanism was evaluated and characterized in conjunction with SIM to ensure volumetric images could be recorded and reconstructed without significant losses in optical section thickness and lateral resolution over the full desired scan range. It was demonstrated that sub-cellular image resolutions were obtainable in both microsphere films and in ex vivo oral mucosa, spanning multiple cell layers, without significant losses in image quality. The mechanism proposed here has the ability to be integrated into any wide-field microscopy system to convert it into a three-dimensional imaging platform without the need for axial scanning of the sample or imaging optics. The ability to axially scan independent of mechanical movement also provides the opportunity for the development of endoscopic systems which can create volumetric images of tissue in vivo.

Hybrid photonic signal processing

NASA Astrophysics Data System (ADS)

Ghauri, Farzan Naseer

This thesis proposes research of novel hybrid photonic signal processing systems in the areas of optical communications, test and measurement, RF signal processing and extreme environment optical sensors. It will be shown that use of innovative hybrid techniques allows design of photonic signal processing systems with superior performance parameters and enhanced capabilities. These applications can be divided into domains of analog-digital hybrid signal processing applications and free-space---fiber-coupled hybrid optical sensors. The analog-digital hybrid signal processing applications include a high-performance analog-digital hybrid MEMS variable optical attenuator that can simultaneously provide high dynamic range as well as high resolution attenuation controls; an analog-digital hybrid MEMS beam profiler that allows high-power watt-level laser beam profiling and also provides both submicron-level high resolution and wide area profiling coverage; and all optical transversal RF filters that operate on the principle of broadband optical spectral control using MEMS and/or Acousto-Optic tunable Filters (AOTF) devices which can provide continuous, digital or hybrid signal time delay and weight selection. The hybrid optical sensors presented in the thesis are extreme environment pressure sensors and dual temperature-pressure sensors. The sensors employ hybrid free-space and fiber-coupled techniques for remotely monitoring a system under simultaneous extremely high temperatures and pressures.

Quantum confinement-induced tunable exciton states in graphene oxide.

PubMed

Lee, Dongwook; Seo, Jiwon; Zhu, Xi; Lee, Jiyoul; Shin, Hyeon-Jin; Cole, Jacqueline M; Shin, Taeho; Lee, Jaichan; Lee, Hangil; Su, Haibin

2013-01-01

Graphene oxide has recently been considered to be a potential replacement for cadmium-based quantum dots due to its expected high fluorescence. Although previously reported, the origin of the luminescence in graphene oxide is still controversial. Here, we report the presence of core/valence excitons in graphene-based materials, a basic ingredient for optical devices, induced by quantum confinement. Electron confinement in the unreacted graphitic regions of graphene oxide was probed by high resolution X-ray absorption near edge structure spectroscopy and first-principles calculations. Using experiments and simulations, we were able to tune the core/valence exciton energy by manipulating the size of graphitic regions through the degree of oxidation. The binding energy of an exciton in highly oxidized graphene oxide is similar to that in organic electroluminescent materials. These results open the possibility of graphene oxide-based optoelectronic device technology.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dou, Letian; Lai, Minliang; Kley, Christopher S.

Halide perovskites are promising semiconductor materials for solution-processed optoelectronic devices. Their strong ionic bonding nature results in highly dynamic crystal lattices, inherently allowing rapid ion exchange at the solid–vapor and solid–liquid interface. In this paper, we show that the anion-exchange chemistry can be precisely controlled in single-crystalline halide perovskite nanomaterials when combined with nanofabrication techniques. We demonstrate spatially resolved multicolor CsPbX 3 (X = Cl, Br, I, or alloy of two halides) nanowire heterojunctions with a pixel size down to 500 nm with the photoluminescence tunable over the entire visible spectrum. In addition, the heterojunctions show distinct electronic states acrossmore » the interface, as revealed by Kelvin probe force microscopy. Finally, these perovskite heterojunctions represent key building blocks for high-resolution multicolor displays beyond current state-of-the-art technology as well as high-density diode/transistor arrays.« less

Towards Highly-Efficient Phototriggered Data Storage by Utilizing a Diketopyrrolopyrrole-Based Photoelectronic Small Molecule.

PubMed

Li, Yang; Li, Hua; He, Jinghui; Xu, Qingfeng; Li, Najun; Chen, Dongyun; Lu, Jianmei

2016-07-20

A cooperative photoelectrical strategy is proposed for effectively modulating the performance of a multilevel data-storage device. By taking advantage of organic photoelectronic molecules as storage media, the fabricated device exhibited enhanced working parameters under the action of both optical and electrical inputs. In cooperation with UV light, the operating voltages of the memory device were decreased, which was beneficial for low energy consumption. Moreover, the ON/OFF current ratio was more tunable and facilitated high-resolution multilevel storage. Compared with previous methods that focused on tuning the storage media, this study provides an easy approach for optimizing organic devices through multiple physical channels. More importantly, this method holds promise for integrating multiple functionalities into high-density data-storage devices. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

T-REX: Thomson-Radiated Extreme X-rays Moving X-Ray Science into the ''Nuclear'' Applications Space with Thompson Scattered Photons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barty, C P; Hartemann, F V

2004-09-21

The scattering of laser photons from relativistic electrons (Thomson scattering) has been demonstrated to be a viable method for the production of ultrashort-duration pulses of tunable radiation in the 10-keV to 100-keV range. Photons in this range are capable of exciting or ionizing even the most tightly bound of atomic electrons. A wide variety of atomistic scale applications are possible. For example, Thomson x-ray sources have been constructed at LLNL (PLEIADES) and LBL as picosecond, stroboscopic probes of atomic-scale dynamics and at Vanderbilt University as element-specific tools for medical radiography and radiology. While these sources have demonstrated an attractive abilitymore » to simultaneously probe on an atomic spatial and temporal scale, they do not necessarily exploit the full potential of the Thomson scattering process to produce high-brightness, high-energy photons. In this white paper, we suggest that the peak brightness of Thomson sources can scale as fast as the 4th power of electron beam energy and that production via Thomson scattering of quasi-monochromatic, tunable radiation in the ''nuclear-range'' between 100-keV and several MeV is potentially a much more attractive application space for this process. Traditional sources in this regime are inherently ultra-broadband and decline rapidly in brightness as a function of photon energy. The output from dedicated, national-laboratory-scale, synchrotron facilities, e.g. APS, SPring8, ESRF etc., declines by more than 10 orders from 100 keV to 1 MeV. At 1 MeV, we conservatively estimate that Thomson-source, peak brightness can exceed that of APS (the best machine in the DOE complex) by more than 15 orders of magnitude. In much the same way that tunable lasers revolutionized atomic spectroscopy, this ''Peta-step'' advance in tunable, narrow-bandwidth, capability should enable entirely new fields of study and new, programmatically-interesting, applications such as: micrometer-spatial-resolution, MeV, flash radiography of dense, energetic systems (NIF, JASPER), precision, photo-nuclear absorption spectroscopy (DNT, PAT), non-destructive, resonant nuclear fluorescent imaging of special nuclear materials (NAI, DHS), dynamic, micro-crack failure analysis (aerospace industry, SSP) etc. Concepts are presented for new Thomson-Radiated Extreme X-ray (T-REX) sources at LLNL. These leverage LLNL's world-leading expertise in high-intensity lasers, high average power lasers, diffractive optics, Thomson-based x-ray source development, and advanced photoguns to produce tunable, quasi-monochromatic radiation from 50-keV to several MeV. Above {approx}100 keV, T-REX would be unique in the world with respect to BOTH peak x-ray brilliance AND average x-ray brilliance. This capability would naturally compliment the x-ray capability of large-scale, synchrotron facilities currently within the DoE complex by significantly extending the x-ray energy range over which, tunable, high-brightness applications could be pursued. It would do so at a small fraction of the cost of the purely, accelerator-based facilities. It is anticipated that T-REX could provide new opportunities for interaction of LLNL with the DoE Office of Science, DARPA, DHS etc. and would place LLNL clearly at the forefront of laser-based, x-ray generation world-wide.« less

High Resolution Spectroscopy to Support Atmospheric Measurements

NASA Technical Reports Server (NTRS)

Venkataraman, Malathy Devi

2003-01-01

Spectroscopic parameters (such as line position, intensity, broadening and shifting coefficients and their temperature dependences, line mixing coefficients etc.) for various molecular species of atmospheric interest are determined. In order to achieve these results, infrared spectra of several molecular bands are obtained using high-resolution recording instruments such as tunable diode laser spectrometer and Fourier transform spectrometers. Using sophisticated analysis routines (Multispectrum nonlinear least squares technique) these high-resolution infrared spectra are processed to determine the various spectral line parameters that are cited above. Spectra were taken using the McMath-Pierce Fourier transform spectrometer (FTS) at the National Solar Observatory on Kitt Peak, Arizona as well as the Bruker FTS at the Pacific Northwest National Laboratory (PNNL) at Richland, Washington. Most of the spectra are acquired not only at room temperature, but also at several different cold temperatures. This procedure is necessary to study the variation of the spectral line parameters as a function of temperature in order to simulate the Earth's and other planetary atmospheric environments. Depending upon the strength or weakness of the various bands recorded and analyzed, the length(s) of the absorption cells in which the gas samples under study are kept varied from a few centimeters up to several meters and the sample temperatures varied from approximately +30 C to -63 C. Research on several infrared bands of various molecular species and their isotopomers are undertaken. Those studies are briefly described.

High Resolution Characterization of Engineered Nanomaterial Dispersions in Complex Media Using Tunable Resistive Pulse Sensing Technology

PubMed Central

2015-01-01

In vitro toxicity assessment of engineered nanomaterials (ENM), the most common testing platform for ENM, requires prior ENM dispersion, stabilization, and characterization in cell culture media. Dispersion inefficiencies and active aggregation of particles often result in polydisperse and multimodal particle size distributions. Accurate characterization of important properties of such polydisperse distributions (size distribution, effective density, charge, mobility, aggregation kinetics, etc.) is critical for understanding differences in the effective dose delivered to cells as a function of time and dispersion conditions, as well as for nano–bio interactions. Here we have investigated the utility of tunable nanopore resistive pulse sensing (TRPS) technology for characterization of four industry relevant ENMs (oxidized single-walled carbon nanohorns, carbon black, cerium oxide and nickel nanoparticles) in cell culture media containing serum. Harvard dispersion and dosimetry platform was used for preparing ENM dispersions and estimating delivered dose to cells based on dispersion characterization input from dynamic light scattering (DLS) and TRPS. The slopes of cell death vs administered and delivered ENM dose were then derived and compared. We investigated the impact of serum protein content, ENM concentration, and cell medium on the size distributions. The TRPS technology offers higher resolution and sensitivity compared to DLS and unique insights into ENM size distribution and concentration, as well as particle behavior and morphology in complex media. The in vitro dose–response slopes changed significantly for certain nanomaterials when delivered dose to cells was taken into consideration, highlighting the importance of accurate dispersion and dosimetry in in vitro nanotoxicology. PMID:25093451

SO2 Spectroscopy with A Tunable UV Laser

NASA Technical Reports Server (NTRS)

Morey, W. W.; Penney, C. M.; Lapp, M.

1973-01-01

A portion of the fluorescence spectrum of SO2 has been studied using a narrow wavelength doubled dye laser as the exciting source. One purpose of this study is to evaluate the use of SO2 resonance re-emission as a probe of SO2 in the atmosphere. When the SO2 is excited by light at 300.2 nm, for example, a strong reemission peak is observed which is Stokes-shifted from the incident light wavelength by the usual Raman shift (the VI symmetric vibration frequency 1150.5/cm ). The intensity of this peak is sensitive to small changes (.01 nm) in the incident wavelength. Measurements of the N2 quenching and self quenching of this re-emission have been obtained. Preliminary analysis of this data indicates that the quenching is weak but not negligible. The dye laser in our system is pumped by a pulsed N2 laser. Tuning 'and spectral narrowing are accomplished using a telescope-echelle grating combination. In a high power configuration the resulting pulses have a spectral width of about 5 x 10(exp -3) nm and a time duration of about 6 nsec. The echelle grating is rotated by a digital stepping motor, such that each step shifts the wavelength by 6 x 10(exp -4) nm. In addition to the tunable, narrow wavelength uv source and spectral analysis of the consequent re-emission, the system also provides time resolution of the re-emitted light to 6 nsec resolution. This capability is being used to study the lifetime of low pressure S02 fluorescence at different wavelengths and pressures.

A SPAD-based 3D imager with in-pixel TDC for 145ps-accuracy ToF measurement

NASA Astrophysics Data System (ADS)

Vornicu, I.; Carmona-Galán, R.; Rodríguez-Vázquez, Á.

2015-03-01

The design and measurements of a CMOS 64 × 64 Single-Photon Avalanche-Diode (SPAD) array with in-pixel Time-to-Digital Converter (TDC) are presented. This paper thoroughly describes the imager at architectural and circuit level with particular emphasis on the characterization of the SPAD-detector ensemble. It is aimed to 2D imaging and 3D image reconstruction in low light environments. It has been fabricated in a standard 0.18μm CMOS process, i. e. without high voltage or low noise features. In these circumstances, we are facing a high number of dark counts and low photon detection efficiency. Several techniques have been applied to ensure proper functionality, namely: i) time-gated SPAD front-end with fast active-quenching/recharge circuit featuring tunable dead-time, ii) reverse start-stop scheme, iii) programmable time resolution of the TDC based on a novel pseudo-differential voltage controlled ring oscillator with fast start-up, iv) a global calibration scheme against temperature and process variation. Measurements results of individual SPAD-TDC ensemble jitter, array uniformity and time resolution programmability are also provided.

Solar coronal magnetic field topology inferred from high resolution optical and x-ray movies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tarbell, T.; Frank, Z.; Hurlburt, N.

1993-01-01

The authors are using high resolution digital movies of solar active regions in optical and X-ray wavelengths to study solar flares and other transients. The optical movies were collected at the Swedish Solar Observatory on La Palma using the Lockheed tunable filtergraph system, in May-July, 1992. They include longitudinal and transverse magnetograms, H-alpha Doppler and intensity images at many wavelengths, Ca K, Na D, and white light images. Simultaneous X-ray images from Yohkoh are available much of the time. Several ways to establish the connectivity of some coronal magnetic field lines are being explored. Some of the clues available are:more » magnetic footpoint polarities and transverse field direction; H-alpha fibrils and loops seen in several wavelengths; proper motion and Dopper shifts of blobs moving along field lines; footprint brightening in micro-flares; spreading of flare ribbons during gradual phases of flares; X-ray morphology and correlations with H-alpha; and draining of flare loops. Examples of each of these will be shown on video.« less

Adsorption and Transport of Methane Molecules through One-Dimensional Channels in Dipeptide-Based Materials

NASA Astrophysics Data System (ADS)

Paradiso, Daniele; Perelli Cippo, Enrico; Gorini, Giuseppe; Rossi, Giorgio; Larese, John Z.

The development of new materials for use in energy and environmental applications is of great interest, in particular in the areas of gas separation and carbon capture, where molecular transport plays a significant role. The dipeptides are organic molecules that offer an attractive possibility in such areas, because they form open hexagonal crystalline structures (space group P61) with quasi one-dimensional channels of tunable pore diameters in the range 3-6 Å. These molecular crystals exhibit selective adsorption, as well as, water and gas transport properties: these are believed to result from collective vibrations of the crystal structure that are coupled to the motions of the guest molecules within the channels. Current studies focus on characterizing the system methane and L-Isoleucyl-L-Valine (IV): this was initially done with high-resolution adsorption isotherms; then, high-resolution Inelastic Neutron Scattering measurements at the Spallation Neutron Source (BASIS spectrometer) revealed clear rotational tunneling peaks, offering details to unravel the potential energy surface of the system, as well as, evidences that channels flexibility and dynamical motion of the molecules have influence on the dipeptides adsorption properties.

Thin-Film Ferroelectric Tunable Microwave Devices Being Developed

NASA Technical Reports Server (NTRS)

VanKeuls, Frederick W.

1999-01-01

Electronically tunable microwave components have become the subject of intense research efforts in recent years. Many new communications systems would greatly benefit from these components. For example, planned low Earth orbiting satellite networks have a need for electronically scanned antennas. Thin ferroelectric films are one of the major technologies competing to fill these applications. When a direct-current (dc) voltage is applied to ferroelectric film, the dielectric constant of the film can be decreased by nearly an order of magnitude, changing the high-frequency wavelength in the microwave device. Recent advances in film growth have demonstrated high-quality ferroelectric thin films. This technology may allow microwave devices that have very low power and are compact, lightweight, simple, robust, planar, voltage tunable, and affordable. The NASA Lewis Research Center has been designing, fabricating, and testing proof-of-concept tunable microwave devices. This work, which is being done in-house with funding from the Lewis Director's Discretionary Fund, is focusing on introducing better microwave designs to utilize these materials. We have demonstrated Ku- and K-band phase shifters, tunable local oscillators, tunable filters, and tunable diplexers. Many of our devices employ SrTiO3 as the ferroelectric. Although it is one of the more tunable and easily grown ferroelectrics, SrTiO3 must be used at cryogenic temperatures, usually below 100 K. At these temperatures, we frequently use high-temperature superconducting thin films of YBa2Cu3O7-8 to carry the microwave signals. However, much of our recent work has concentrated on inserting room-temperature ferroelectric thin films, such as BaxSr1- xTiO3 into these devices. The BaxSr1-xTiO3 films are used in conjuction with normal metal conductors, such as gold.

First Infrared Predissociation Spectra of He-TAGGED Protonated Primary Alcohols at 4 K

NASA Astrophysics Data System (ADS)

Stoffels, Alexander; Redlich, Britta; Oomens, J.; Asvany, Oskar; Brünken, Sandra; Jusko, Pavol; Thorwirth, Sven; Schlemmer, Stephan

2015-06-01

Cryogenic multipole ion traps have become popular devices in the development of sensitive action-spectroscopic techniques. The low ion temperature leads to enhanced spectral resolution, and less congested spectra. In the early 2000s, a 22-pole ion trap was coupled to the Free-Electron Laser for Infrared eXperiments (FELIX), yielding infrared Laser Induced Reaction (LIR) spectra of the molecular ions C_2H_2+ and CH_5+. This pioneering work showed the great opportunities combining cold mass-selected molecular ions with widely tunable broadband IR radiation. In the past year a cryogenic (T>3.9 K) 22-pole ion trap designed and built in Cologne (FELion) has been successfully coupled to FELIX, which in its current configuration provides continuously tunable infrared radiation from 3 μm to 150 μm, hence allowing to probe characteristic vibrational spectra in the so-called "fingerprint region" with a sufficient spectral energy density also allowing for multiple photon processes (IR-MPD). Here we present the first infrared predissociation spectra of He-tagged protonated methanol and ethanol (MeOH_2+/EtOH_2+) stored at 4 K. These vibrational spectra were recorded with both a commercial OPO and FELIX, covering a total spectral range from 3700 wn to 550 wn at a spectral resolution of a few wn. The H-O-H stretching and bending modes clearly distinguish the protonated alcohols from their neutral analoga. For EtOH_2+, also IR-MPD spectra of the bare ion could be recorded. The symmetric and antisymmetric H-O-H stretching bands at around 3 μm show no significant shift within the given spectral resolution in comparison to those recorded with He predissociation, indicating a rather small perturbation caused by the attached He. The vibrational bands were assigned using quantum-chemical calculations on different levels of theory. The computed frequencies correspond favorably to the experimental spectra. Subsequent high resolution measurements could lead to a better structural characterization of these protonated alcohols. Asvany et al.: Phys. Rev.Lett. 94, 073001 (2005), Asvany et al.: Science 309, 1219-1222 (2005)

Comparison of the Frequency Response and Voltage Tuning Characteristics of a FFP and a MEMS Fiber Optic Tunable Filter

DTIC Science & Technology

2004-05-12

Structural Engineering, La Jolla, CA 92093 14. ABSTRACT Tunable optical filters based on a Fabry - Perot element are a critical component in many...wavelength based fiber optic sensor systems. This report compares the performance of two fiber-pigtailed tunable optical filters, the fiber Fabry - Perot (FFP...both filters suggests that they can operate at frequencies up to 20 kHz and possibly as high as 100 kHz. 15. SUBJECT TERMS Tunable Fabry - Perot filters

Micromachined structures for vertical microelectrooptical devices on InP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seassal, C.; Leclercq, J.L.; Letartre, X.

1996-12-31

The authors presented a microstructuring method in order to fabricate tunable vertical resonant cavity optical devices. PL characterizations were performed on a test structure in order to evaluate the effect of the cavity thickness on the peak characteristics. Modeling of the mechanical, electrostatic, and optical behavior of the device, PL simulation were performed, and showed a good agreement with the experiments. This is a first preliminary validation of InP-based MOEMS for further realization of tunable wavelength-selective passive filters, or photodiodes and lasers by incorporating active region within the cavity. Micro-reflectivity measurements with a spatial resolution of 20 {micro}m are underwaymore » in their group, in order to measure directly the resonance shift and spectral linewidth.« less

Tunable and switchable dual-waveband ultrafast fiber laser with 100 GHz repetition-rate.

PubMed

Tan, Xiao-Mei; Chen, Hong-Jie; Cui, Hu; Lv, Yao-Kun; Zhao, Guan-Kai; Luo, Zhi-Chao; Luo, Ai-Ping; Xu, Wen-Cheng

2017-07-10

We demonstrate a tunable and switchable dual-waveband 100 GHz high-repetition-rate (HRR) ultrafast fiber laser based on dissipative four-wave-mixing (DFWM) mode-locked technique. Each waveband maintains HRR operation. The DFWM effect was realized by combining a Fabry-Perot (F-P) filter and a piece of highly nonlinear fiber (HNLF). The tunable and switchable operations were achieved by nonlinear polarization rotation (NPR) technique. Through appropriately controlling the filtering effect induced by NPR, the laser could operate at two kinds of tunable regimes. One is that the spacing between these two wavebands could be tuned while keeping their center at 1559 nm. The other is that the central position of the entire dual-waveband is tunable while with the same separation between these two wavebands of 13.2 nm. Moreover, the laser could switch between these two wavebands. Correspondingly, the center of the single-waveband has a tuning range of 15.2 nm. This versatile ultrafast fiber laser may find applications in fields of optical frequency combs, high speed optical communications, where HRR pulses are necessary.

A high-speed tunable beam splitter for feed-forward photonic quantum information processing.

PubMed

Ma, Xiao-Song; Zotter, Stefan; Tetik, Nuray; Qarry, Angie; Jennewein, Thomas; Zeilinger, Anton

2011-11-07

We realize quantum gates for path qubits with a high-speed, polarization-independent and tunable beam splitter. Two electro-optical modulators act in a Mach-Zehnder interferometer as high-speed phase shifters and rapidly tune its splitting ratio. We test its performance with heralded single photons, observing a polarization-independent interference contrast above 95%. The switching time is about 5.6 ns, and a maximal repetition rate is 2.5 MHz. We demonstrate tunable feed-forward operations of a single-qubit gate of path-encoded qubits and a two-qubit gate via measurement-induced interaction between two photons.

Outdoor, indoor, and human breath content measurements of ammonia by tunable diode laser spectroscopy technique

NASA Astrophysics Data System (ADS)

Moskalenko, Konstantin L.; Nadezhdinskii, Alexander I.

1996-10-01

Trace contents of ammonia in outdoor, indoor and exhaled air were measured on the base of high resolution absorption spectra. Tunable diode laser system developed for this purpose possesses approximately one second time constant, approximately 200 cm3 sample volume, 5 ppb sensitivity. The calibration of unit was based on measurements of relative intensities of sQ(3,1)...sQ(3,3) absorption lines of v2s and following calculation on the base of a priori data on strength and broadening coefficients of detected lines. Measured indoor contents of ammonia was in 5-10 times higher than outdoor contents. Approximately two times drop in NH3 room content after 6 p.m. was detected. Obtained behavior of ammonia content in respiration right after the smoking demonstrates that the removing of ammonia from lungs has the ventilation character. Measured contents of NH3 in human respiration was ranged between 120 and 220 ppb. The absence of ammonia content differences from respiration of smoking and non smoking persons demonstrates that the accumulation of NH3 by human organism seems to be rather negligible for a short time exposure, e.g. like smoking.

Interfacial Shear Strength of Multilayer Graphene Oxide Films.

PubMed

Daly, Matthew; Cao, Changhong; Sun, Hao; Sun, Yu; Filleter, Tobin; Singh, Chandra Veer

2016-02-23

Graphene oxide (GO) is considered as one of the most promising layered materials with tunable physical properties and applicability in many important engineering applications. In this work, the interfacial behavior of multilayer GO films was directly investigated via GO-to-GO friction force microscopy, and the interfacial shear strength (ISS) was measured to be 5.3 ± 3.2 MPa. Based on high resolution atomic force microscopy images and the available chemical data, targeted molecular dynamics simulations were performed to evaluate the influence of functional structure, topological defects, and interlayer registry on the shear response of the GO films. Theoretical values for shear strength ranging from 17 to 132 MPa were predicted for the different structures studied, providing upper bounds for the ISS. Computational results also revealed the atomic origins of the stochastic nature of friction measurements. Specifically, the wide scatter in experimental measurements was attributed to variations in functional structure and topological defects within the sliding volume. The findings of this study provide important insight for understanding the significant differences in strength between monolayer and bulk graphene oxide materials and can be useful for engineering topological structures with tunable mechanical properties.

Tunable resonance-domain diffraction gratings based on electrostrictive polymers.

PubMed

Axelrod, Ramon; Shacham-Diamand, Yosi; Golub, Michael A

2017-03-01

Critical combination of high diffraction efficiency and large diffraction angles can be delivered by resonance-domain diffractive optics with high aspect ratio and wavelength-scale grating periods. To advance from static to electrically tunable resonance-domain diffraction grating, we resorted to its replication onto 2-5 μm thick P(VDF-TrFE-CFE) electrostrictive ter-polymer membranes. Electromechanical and optical computer simulations provided higher than 90% diffraction efficiency, a large continuous deflection range exceeding 20°, and capabilities for adiabatic spatial modulation of the grating period and slant. A prototype of the tunable resonance-domain diffraction grating was fabricated in a soft-stamp thermal nanoimprinting process, characterized, optically tested, and provided experimental feasibility proof for the tunable sub-micron-period gratings on electrostrictive polymers.

High Quality Liquid Crystal Tunable Lenses and Optimization with Floating Electrodes

ERIC Educational Resources Information Center

Li, Liwei

2013-01-01

In addition to the display application, Liquid Crystals (LC) can be very useful in other applications such as beam steering, tunable lenses, etc. Electro-optical LC tunable lenses have been considered as an alternative to conventional glass lenses because of their ability to change their focal length with the application of a control voltage, as…

Spectral resolution control of acousto-optical cells operating with collimated and divergent beams

NASA Astrophysics Data System (ADS)

Voloshinov, Vitaly B.; Mishin, Dimitry D.

1994-01-01

The paper is devoted to theoretical and experimental investigations of acousto-optical interactions in crystals which may be used for spectral filtration of light in tunable acousto- optical filters. Attention is paid to spectral resolution control during operation with divergent or collimated noncoherent optical beams. In all examined cases spectral bands of anisotropic Bragg diffraction were regulated by means of novel electronical methods. Resolution control was achieved in paratellurite cells with non-collinear and quasi-collinear regimes of the diffraction. Filtration spectral bandwidths for visible light were electronically changed by a factor of 10 divided by 20 by drive electrical signals switching and drive electrical power regulations.

Development of an integrated sub-picometric SWIFTS-based wavelength meter

NASA Astrophysics Data System (ADS)

Duchemin, Céline; Thomas, Fabrice; Martin, Bruno; Morino, Eric; Puget, Renaud; Oliveres, Robin; Bonneville, Christophe; Gonthiez, Thierry; Valognes, Nicolas

2017-02-01

SWIFTSTM technology has been known for over five years to offer compact and high-resolution laser spectrum analyzers. The increase of wavelength monitoring demand with even better accuracy and resolution has pushed the development of a wavelength meter based on SWIFTSTM technology, named LW-10. As a reminder, SWIFTSTM principle consists in a waveguide in which a stationary wave is created, sampled and read out by a linear image sensor array. Due to its inherent properties (non-uniform subsampling) and aliasing signal (as presented in Shannon-Nyquist criterion), the system offers short spectral window bandwidths thus needs an a priori on the working wavelength and thermal monitoring. Although SWIFTSTM-based devices are barely sensitive to atmospheric pressure, temperature control is a key factor to master both high accuracy and wavelength meter resolution. Temperature control went from passive (temperature probing only) to active control (Peltier thermoelectric cooler) with milli-degree accuracy. The software part consists in dropping the Fourier-like transform, for a least-squares method directly on the interference pattern. Moreover, the consideration of the system's chromatic behavior provides a "signature" for automated wavelength detection and discrimination. This SWIFTSTM-based new device - LW-10 - shows outstanding results in terms of absolute accuracy, wavelength meter resolution as well as calibration robustness within a compact device, compared to other existing technologies. On the 630 - 1100 nm range, the final device configuration allows pulsed or CW lasers monitoring with 20 MHz resolution and 200 MHz absolute accuracy. Non-exhaustive applications include tunable laser control and frequency locking experiments

Two dimensional photoacoustic imaging using microfiber interferometric acoustic transducers

NASA Astrophysics Data System (ADS)

Wang, Xiu Xin; Li, Zhang Yong; Tian, Yin; Wang, Wei; Pang, Yu; Tam, Kin Yip

2018-07-01

Photoacoustic imaging transducer with a pair of wavelength-matched Bragg gratings (forming a Fabry-Perot cavity) inscribed on a short section of microfiber has been developed. A tunable laser with wavelength that matched to one of selected fringe slopes was used to transmit the acoustic induced wavelength. Interferometric fringes with high finesse in transmission significantly enhanced the sensitivity of the transducer even under very small acoustic perturbations. The performance of this novel transducer was evaluated through the imaging studies of human hairs (∼98 μm in diameter). The spatial resolution is 300 μm. We have demonstrated that the novel transducer developed in this study is a versatile tool for photoacoustic imaging study.

Fruit ripening using hyperspectral imaging

NASA Astrophysics Data System (ADS)

., Swetha; Chidangil, Santhosh; Karpate, Tanvi; Asundi, Anand

2017-06-01

The ripening of fruits is associated with changes, in some cases subtle, in the color of the fruit. Traditionally spectroscopy used to measure these subtle changes and infer the ripeness of fruits. Spectrometers provides high-resolution but only measure a small area of the fruit. That might not be a good indicator of the overall ripeness. In this paper, we propose a compact tunable LED based hyper spectral imaging system that scans through a set of wavelengths and images, the reflectance from the whole fruit. Based on the type of fruit, only specific wavelengths need to be scanned. Following a validation using a Rubik's cube, an example banana going through its ripening cycles is used to demonstrate the system.

Three-dimensional direct cell patterning in collagen hydrogels with near-infrared femtosecond laser

PubMed Central

Hribar, Kolin C.; Meggs, Kyle; Liu, Justin; Zhu, Wei; Qu, Xin; Chen, Shaochen

2015-01-01

We report a methodology for three-dimensional (3D) cell patterning in a hydrogel in situ. Gold nanorods within a cell-encapsulating collagen hydrogel absorb a focused near-infrared femtosecond laser beam, locally denaturing the collagen and forming channels, into which cells migrate, proliferate, and align in 3D. Importantly, pattern resolution is tunable based on writing speed and laser power, and high cell viability (>90%) is achieved using higher writing speeds and lower laser intensities. Overall, this patterning technique presents a flexible direct-write method that is applicable in tissue engineering systems where 3D alignment is critical (such as vascular, neural, cardiac, and muscle tissue). PMID:26603915

Tunable Heterodyne Receiver from 100 Micron to 1,000 Micron for Airborne Observations

NASA Technical Reports Server (NTRS)

Roeser, H. P.; Wattenbach, R.; Vanderwal, P.

1984-01-01

Interest in high resolution spectrometers for the submillimeter wavelength range from 100 micron to 1,000 micron is mostly stimulated by molecular spectroscopy in radioastronomy and atmospheric physics, and by plasma diagnostic experiments. Schottky diodes in waveguide mixer technology and InSb-hot electron bolometers are successfully used in the 0.5 to a few millimeter range whereas tandem Fabry-Perot spectrometers combined with photoconductive detectors (Ge:Sb and Ge:Ga) are used for the 100 micron range. Recent research on heterodyne spectrometers, with Schottky diodes in an open structure mixer and a molecular laser as local oscillators, which can be used over the whole wavelength range is summarized.

Characterization of (Ba(0.5)Sr(0.5)) TiO3 Thin Films for Ku-Band Phase Shifters

NASA Technical Reports Server (NTRS)

Mueller, Carl H.; VanKeuls, Fredrick W.; Romanofsky, Robert R.; Miranda, Felix A.; Warner, Joseph D.; Canedy, Chadwick L.; Ramesh, Rammamoorthy

1999-01-01

The microstructural properties of (Ba(0.5)Sr(0.5)TiO3) (BSTO) thin films (300, 700, and 1400 nm thick) deposited on LaAlO3 (LAO) substrates were characterized using high-resolution x-ray diffractometry. Film crystallinity was the parameter that most directly influenced tunability, and we observed that a) the crystalline quality was highest in the thinnest film and progressively degraded with increasing film thickness; and b) strain at the film/substrate interface was completely relieved via dislocation formation. Paraelectric films such as BSTO offer an attractive means of incorporating low-cost phase shifter circuitry into beam-steerable reflectarray antennas.

Measurement of two-dimensional thickness of micro-patterned thin film based on image restoration in a spectroscopic imaging reflectometer.

PubMed

Kim, Min-Gab; Kim, Jin-Yong

2018-05-01

In this paper, we introduce a method to overcome the limitation of thickness measurement of a micro-patterned thin film. A spectroscopic imaging reflectometer system that consists of an acousto-optic tunable filter, a charge-coupled-device camera, and a high-magnitude objective lens was proposed, and a stack of multispectral images was generated. To secure improved accuracy and lateral resolution in the reconstruction of a two-dimensional thin film thickness, prior to the analysis of spectral reflectance profiles from each pixel of multispectral images, the image restoration based on an iterative deconvolution algorithm was applied to compensate for image degradation caused by blurring.

Laser absorption spectroscopy of water vapor confined in nanoporous alumina: wall collision line broadening and gas diffusion dynamics.

PubMed

Svensson, Tomas; Lewander, Märta; Svanberg, Sune

2010-08-02

We demonstrate high-resolution tunable diode laser absorption spectroscopy (TDLAS) of water vapor confined in nanoporous alumina. Strong multiple light scattering results in long photon pathlengths (1 m through a 6 mm sample). We report on strong line broadening due to frequent wall collisions (gas-surface interactions). For the water vapor line at 935.685 nm, the HWHM of confined molecules are about 4.3 GHz as compared to 2.9 GHz for free molecules (atmospheric pressure). Gas diffusion is also investigated, and in contrast to molecular oxygen (that moves rapidly in and out of the alumina), the exchange of water vapor is found very slow.

Studies on lasers and laser devices

NASA Technical Reports Server (NTRS)

Harris, S. E.; Siegman, A. E.; Young, J. F.

1983-01-01

The goal of this grant was to study lasers, laser devices, and uses of lasers for investigating physical phenomena are studied. The active projects included the development of a tunable, narrowband XUV light source and its application to the spectroscopy of core excited atomic states, and the development of a technique for picosecond time resolution spectroscopy of fast photophysical processes.

High-speed wavelength switching of tunable MEMS vertical cavity surface emitting laser by ringing suppression

NASA Astrophysics Data System (ADS)

Inoue, Shunya; Nishimura, Shun; Nakahama, Masanori; Matsutani, Akihiro; Sakaguchi, Takahiro; Koyama, Fumio

2018-04-01

For use in wavelength division multiplexing (WDM) with high-speed wavelength routing functions, the fast wavelength switching of tunable lasers is a key function. A tunable MEMS vertical cavity surface emitting laser (VCSEL) is a good candidate as a light source for this purpose. The cantilever in MEMS VCSELs has a high mechanical resonance frequency thanks to its small size, but the switching time is limited by the ringing of the cantilever structure. In this paper, we analyzed the mechanical behavior of a cantilever MEMS mirror and demonstrated ringing-free operation with an engineered voltage signal. The applied voltage waveform was optimized in a two-step format and we experimentally obtained ringing free wavelength switching. We measured the transient response of the wavelength by inserting a tunable filter, exhibiting the settling time of less than 2.5 µs, which corresponds to a half period of the cantilever resonance frequency.

Nanoscale infrared (IR) spectroscopy and imaging of structural lipids in human stratum corneum using an atomic force microscope to directly detect absorbed light from a tunable IR laser source.

PubMed

Marcott, Curtis; Lo, Michael; Kjoller, Kevin; Domanov, Yegor; Balooch, Guive; Luengo, Gustavo S

2013-06-01

An atomic force microscope (AFM) and a tunable infrared (IR) laser source have been combined in a single instrument (AFM-IR) capable of producing ~200-nm spatial resolution IR spectra and absorption images. This new capability enables IR spectroscopic characterization of human stratum corneum at unprecendented levels. Samples of normal and delipidized stratum corneum were embedded, cross-sectioned and mounted on ZnSe prisms. A pulsed tunable IR laser source produces thermomechanical expansion upon absorption, which is detected through excitation of contact resonance modes in the AFM cantilever. In addition to reducing the total lipid content, the delipidization process damages the stratum corneum morphological structure. The delipidized stratum corneum shows substantially less long-chain CH2 -stretching IR absorption band intensity than normal skin. AFM-IR images that compare absorbances at 2930/cm (lipid) and 3290/cm (keratin) suggest that regions of higher lipid concentration are located at the perimeter of corneocytes in the normal stratum corneum. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Protein dynamics observed by tunable mid-IR quantum cascade lasers across the time range from 10ns to 1s.

PubMed

Schultz, Bernd-Joachim; Mohrmann, Hendrik; Lorenz-Fonfria, Victor A; Heberle, Joachim

2018-01-05

We have developed a spectrometer based on tunable quantum cascade lasers (QCLs) for recording time-resolved absorption spectra of proteins in the mid-infrared range. We illustrate its performance by recording time-resolved difference spectra of bacteriorhodopsin in the carboxylic range (1800-1700cm -1 ) and on the CO rebinding reaction of myoglobin (1960-1840cm -1 ), at a spectral resolution of 1cm -1 . The spectrometric setup covers the time range from 4ns to nearly a second with a response time of 10-15ns. Absorption changes as low as 1×10 -4 are detected in single-shot experiments at t>1μs, and of 5×10 -6 in kinetics obtained after averaging 100 shots. While previous time-resolved IR experiments have mostly been conducted on hydrated films of proteins, we demonstrate here that the brilliance of tunable quantum cascade lasers is superior to perform ns time-resolved experiments even in aqueous solution (H 2 O). Copyright © 2017 Elsevier B.V. All rights reserved.

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.

Polarization-maintaining, high-energy, wavelength-tunable, Er-doped ultrashort pulse fiber laser using carbon-nanotube polyimide film.

PubMed

Senoo, Y; Nishizawa, N; Sakakibara, Y; Sumimura, K; Itoga, E; Kataura, H; Itoh, K

2009-10-26

A high-energy, wavelength-tunable, all-polarization-maintaining Er-doped ultrashort fiber laser was demonstrated using a polyimide film dispersed with single-wall carbon nanotubes. A variable output coupler and wavelength filter were used in the cavity configuration, and high-power operation was demonstrated. The maximum average power was 12.6 mW and pulse energy was 585 pJ for stable single-pulse operation with an output coupling ratio as high as 98.3%. Wide wavelength-tunable operation at 1532-1562 nm was also demonstrated by controlling the wavelength filter. The RF amplitude noise characteristics were examined in terms of their dependence on output coupling ratio and oscillation wavelength.

Comparison of two structured illumination techniques based on different 3D illumination patterns

NASA Astrophysics Data System (ADS)

Shabani, H.; Patwary, N.; Doblas, A.; Saavedra, G.; Preza, C.

2017-02-01

Manipulating the excitation pattern in optical microscopy has led to several super-resolution techniques. Among different patterns, the lateral sinusoidal excitation was used for the first demonstration of structured illumination microscopy (SIM), which provides the fastest SIM acquisition system (based on the number of raw images required) compared to the multi-spot illumination approach. Moreover, 3D patterns that include lateral and axial variations in the illumination have attracted more attention recently as they address resolution enhancement in three dimensions. A threewave (3W) interference technique based on coherent illumination has already been shown to provide super-resolution and optical sectioning in 3D-SIM. In this paper, we investigate a novel tunable technique that creates a 3D pattern from a set of multiple incoherently illuminated parallel slits that act as light sources for a Fresnel biprism. This setup is able to modulate the illumination pattern in the object space both axially and laterally with adjustable modulation frequencies. The 3D forward model for the new system is developed here to consider the effect of the axial modulation due to the 3D patterned illumination. The performance of 3D-SIM based on 3W interference and the tunable system are investigated in simulation and compared based on two different criteria. First, restored images obtained for both 3D-SIM systems using a generalized Wiener filter are compared to determine the effect of the illumination pattern on the reconstruction. Second, the effective frequency response of both systems is studied to determine the axial and lateral resolution enhancement that is obtained in each case.

Development of a Fiber Laser with Independently Adjustable Properties for Optical Resolution Photoacoustic Microscopy.

PubMed

Aytac-Kipergil, Esra; Demirkiran, Aytac; Uluc, Nasire; Yavas, Seydi; Kayikcioglu, Tunc; Salman, Sarper; Karamuk, Sohret Gorkem; Ilday, Fatih Omer; Unlu, Mehmet Burcin

2016-12-08

Photoacoustic imaging is based on the detection of generated acoustic waves through thermal expansion of tissue illuminated by short laser pulses. Fiber lasers as an excitation source for photoacoustic imaging have recently been preferred for their high repetition frequencies. Here, we report a unique fiber laser developed specifically for multiwavelength photoacoustic microscopy system. The laser is custom-made for maximum flexibility in adjustment of its parameters; pulse duration (5-10 ns), pulse energy (up to 10 μJ) and repetition frequency (up to 1 MHz) independently from each other and covers a broad spectral region from 450 to 1100 nm and also can emit wavelengths of 532, 355, and 266 nm. The laser system consists of a master oscillator power amplifier, seeding two stages; supercontinuum and harmonic generation units. The laser is outstanding since the oscillator, amplifier and supercontinuum generation parts are all-fiber integrated with custom-developed electronics and software. To demonstrate the feasibility of the system, the images of several elements of standardized resolution test chart are acquired at multiple wavelengths. The lateral resolution of optical resolution photoacoustic microscopy system is determined as 2.68 μm. The developed system may pave the way for spectroscopic photoacoustic microscopy applications via widely tunable fiber laser technologies.

Development of a Fiber Laser with Independently Adjustable Properties for Optical Resolution Photoacoustic Microscopy

PubMed Central

Aytac-Kipergil, Esra; Demirkiran, Aytac; Uluc, Nasire; Yavas, Seydi; Kayikcioglu, Tunc; Salman, Sarper; Karamuk, Sohret Gorkem; Ilday, Fatih Omer; Unlu, Mehmet Burcin

2016-01-01

Photoacoustic imaging is based on the detection of generated acoustic waves through thermal expansion of tissue illuminated by short laser pulses. Fiber lasers as an excitation source for photoacoustic imaging have recently been preferred for their high repetition frequencies. Here, we report a unique fiber laser developed specifically for multiwavelength photoacoustic microscopy system. The laser is custom-made for maximum flexibility in adjustment of its parameters; pulse duration (5–10 ns), pulse energy (up to 10 μJ) and repetition frequency (up to 1 MHz) independently from each other and covers a broad spectral region from 450 to 1100 nm and also can emit wavelengths of 532, 355, and 266 nm. The laser system consists of a master oscillator power amplifier, seeding two stages; supercontinuum and harmonic generation units. The laser is outstanding since the oscillator, amplifier and supercontinuum generation parts are all-fiber integrated with custom-developed electronics and software. To demonstrate the feasibility of the system, the images of several elements of standardized resolution test chart are acquired at multiple wavelengths. The lateral resolution of optical resolution photoacoustic microscopy system is determined as 2.68 μm. The developed system may pave the way for spectroscopic photoacoustic microscopy applications via widely tunable fiber laser technologies. PMID:27929049

Ion irradiation effects on lithium niobate etalons for tunable spectral filters

NASA Astrophysics Data System (ADS)

Garranzo, D.; Ibarmia, S.; Alvarez-Herrero, A.; Olivares, J.; Crespillo, M.; Díaz, M.

2017-11-01

Solar Orbiter is a mission dedicated to solar and heliospheric physics. It was selected as the first mediumclass mission of ESA's Cosmic Vision 2015-2025 Programme. Solar Orbiter will be used to examine how the Sun creates and controls the heliosphere, the vast bubble of charged particles blown by the solar wind into the interstellar medium. One of the scientific payload elements of Solar Orbiter is the Polarimetric and Helioseismic Imager (PHI). The PHI instrument consists of two telescopes, a High Resolution Telescope (HRT) that will image a fraction of the solar disk at a resolution reaching {150 km at perihelion, and a Full Disk Telescope (FDT) to image the full solar disk during all phases of the orbit. PHI is a diffraction limited, wavelength tunable, quasi-monochromatic, polarisation sensitive imager. These capabilities are needed to infer the magnetic field and line-of-sight (LOS) velocity of the region targeted by the spacecraft. For the spectral analysis, PHI will use an order-sorting filter to isolate a bandpass of the order of 100 mÅ . The FilterGraph (FG) contains an etalon in single pass configuration as tunable spectral filter located inside a temperature stabilized oven. This filter will be made by means of a z-cut LiNbO3 crystal (about 300 microns thick) and multilayer coatings including a conductive one in order to apply a high voltage (up to 5 kV) and induce the required electric field to tune the filter. Solar Orbiter observing mission around the Sun will expose the PHI instrument to extreme radiation conditions, mainly dominated by solar high-energy particles released during severe solar events (protons with energies typically ranging from few keV up to several GeV) and the continuous isotropic background flux of galactic cosmic rays (heavy ions, from Z=1 to Z=92). The main concerns are whether the cumulated radiation damage can degrade the functionality of the filter or, in the worst case, the impact of a single highly ionizing particle, coupled with the HV field, could trigger a dielectric breakdown in the Lithium Niobate. In this paper we present the electro-optical results obtained when exposing a set of LN samples and a lowquality full size etalon to different radiation conditions. In a first irradiation campaign, performed at the Centre for Micro Analysis of Materials (CMAM-Madrid) facilities, we were mainly focused on the long-term degradation effects with a series of high flux (109 cm-2 s-1) proton tests at an energy of 10 MeV. In order to study the possibility of a single ion breakdown, a second campaign was carried out, at the Texas A&M University (TAMU), exposing Lithium Niobate to high LET ion species (78Kr, 40Ar, 129Xe, 197Au) accelerated to the GeV energy range to penetrate or even pass through the entire Lithium Niobate thickness.

Freely Tunable Broadband Polarization Rotator for Terahertz Waves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fan, Ren-Hao; Zhou, Yu; Ren, Xiao-Ping

2014-12-28

A freely tunable polarization rotator for broadband terahertz waves is demonstrated using a three-rotating-layer metallic grating structure, which can conveniently rotate the polarization of a linearly polarized terahertz wave to any desired direction with nearly perfect conversion efficiency. This low-cost, high-efficiency, and freely tunable device has potential applications as material analysis, wireless communication, and THz imaging.

Use of dimensionality to enhance tunable microwave dielectrics

NASA Astrophysics Data System (ADS)

Schlom, D. G.; Lee, Che-Hui; Haislmaier, R.; Vlahos, E.; Gopalan, V.; Birol, T.; Zhu, Y.; Kourkoutis, L. F.; Benedek, N.; Kim, Y.; Brock, J. D.; Muller, D. A.; Fennie, C. J.; Orloff, N. D.; Booth, J. C.; Goian, V.; Kamba, S.; Biegalski, M. D.; Bernhagen, M.; Uecker, R.; Xi, X. X.; Takeuchi, I.

2012-02-01

The miniaturization and integration of frequency-agile microwave circuits---tunable filters, resonators, phase shifters and more---with microelectronics offers tantalizing device possibilities, yet requires thin films whose dielectric constant at GHz frequencies can be tuned by applying a quasi-static electric field. Appropriate systems, e.g., BaxSr1-xTiO3, have a paraelectric-to-ferroelectric transition just below ambient temperature, providing high tunability. Unfortunately such films suffer significant losses arising from defects. Recognizing that progress is stymied by dielectric loss, we start with a system with exceptionally low loss---Srn+1TinO3n+1 phases---where in-plane crystallographic shear (SrO)2 faults provide an alternative to point defects for accommodating non-stoichiometry. In this talk we will establish both experimentally and theoretically the emergence of a ferroelectric and highly tunable ground state in biaxially strained Srn+1TinO3n+1 phases with n>=3 at frequencies up to 40 GHz. With increasing n the (SrO)2 faults are separated further than the ferroelectric coherence length perpendicular to the in-plane polarization, enabling tunability with a figure of merit at room temperature that rivals all known tunable microwave dielectrics.

Tunable emission in surface passivated Mn-ZnS nanophosphors and its application for Glucose sensing

NASA Astrophysics Data System (ADS)

Sharma, Manoj; Jain, Tarun; Singh, Sukhvir; Pandey, O. P.

2012-03-01

The present work describes the tunable emission in inorganic-organic hybrid NPs which can be useful for optoelectronic and biosensing applications. In this work, Mn- ZnS nanoparticles emitting various colors, including blue and orange, were synthesized by simple chemical precipitation method using chitosan as a capping agent. Earlier reports describe that emission color characteristics in nanoparticles are tuned by varying particle size and with doping concentration. Here in this article tunable emission has been achieved by varying excitation wavelength in a single sample. This tunable emission property with high emission intensity was further achieved by changing capping concentration keeping host Mn-ZnS concentration same. Tunable emission is explained by FRET mechanism. Commission Internationale de l'Eclairage (CIE) chromaticity coordinates shifts from (0.273, 0.20) and (0.344, 0.275) for same naocrystals by suitably tuning excitation energy from higher and lower ultra-violet (UV) range. Synthesized nanoparticles have been characterized by X-ray diffraction, SEM, HRTEM, UV- Visible absorption and PL spectroscopy for structural and optical studies. Using tunable emission property, these highly emissive nanoparticles functionalized with biocompatible polymer chitosan were further used for glucose sensing applications.

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.

High-power, fixed, and tunable wavelength, grating-free cascaded Raman fiber lasers

NASA Astrophysics Data System (ADS)

Balaswamy, V.; Arun, S.; Aparanji, Santosh; Choudhury, Vishal; Supradeepa, V. R.

2018-04-01

Cascaded Raman lasers enable high powers at various wavelength bands inaccessible with conventional rare-earth doped lasers. The input and output wavelengths of conventional implementations are fixed by the constituent fiber gratings necessary for cascaded Raman conversion. We demonstrate here, a simple architecture for high power, fixed and wavelength tunable, grating-free, cascaded Raman conversion between different wavelength bands. The architecture is based on the recently proposed distributed feedback Raman lasers. Here, we implement a module which converts the Ytterbium band to the eye-safe 1.5micron region. We demonstrate pump-limited output powers of over 30W in fixed and continuously wavelength tunable configurations.

Frequency-tunable superconducting resonators via nonlinear kinetic inductance

NASA Astrophysics Data System (ADS)

Vissers, M. R.; Hubmayr, J.; Sandberg, M.; Chaudhuri, S.; Bockstiegel, C.; Gao, J.

2015-08-01

We have designed, fabricated, and tested a frequency-tunable high-Q superconducting resonator made from a niobium titanium nitride film. The frequency tunability is achieved by injecting a DC through a current-directing circuit into the nonlinear inductor whose kinetic inductance is current-dependent. We have demonstrated continuous tuning of the resonance frequency in a 180 MHz frequency range around 4.5 GHz while maintaining the high internal quality factor Qi > 180 000. This device may serve as a tunable filter and find applications in superconducting quantum computing and measurement. It also provides a useful tool to study the nonlinear response of a superconductor. In addition, it may be developed into techniques for measurement of the complex impedance of a superconductor at its transition temperature and for readout of transition-edge sensors.

Cellulose nanocrystal and poly[di(ethylene glycol) adipate] blend for tunable lens

NASA Astrophysics Data System (ADS)

Ko, Hyun-U.; Kim, Hyun Chan; Li, Yaguang; Kim, Sang Youn; Kim, Jaehwan

2016-04-01

In these days, consumer electronics and medical device for optical diagnosis are minimalized and mobilized. The focusing part is one of crucial parts of optical diagnosis systems to reduce the size and weight. Thus, demand for tunable lens that change the focus itself is increased. To meet the demand, many tunable lens has been studied by utilizing smart materials that responded under mechanical, magnetic, optical, thermal, chemical, electrical or electrochemical stimuli. This paper reports a cellulose nanocrystal (CNC) and poly[di(ethylene glycol) adipate] (PDEGA) blend that is able to respond under electromechanical stimulus. The preparation of CNC/PDEGA and its characterization are illustrated and its actuation behavior is tested . Because the material has high dielectric constant and high reflection index, it is good candidate material for tunable lens.

Optofluidic fabrication for 3D-shaped particles

NASA Astrophysics Data System (ADS)

Paulsen, Kevin S.; di Carlo, Dino; Chung, Aram J.

2015-04-01

Complex three-dimensional (3D)-shaped particles could play unique roles in biotechnology, structural mechanics and self-assembly. Current methods of fabricating 3D-shaped particles such as 3D printing, injection moulding or photolithography are limited because of low-resolution, low-throughput or complicated/expensive procedures. Here, we present a novel method called optofluidic fabrication for the generation of complex 3D-shaped polymer particles based on two coupled processes: inertial flow shaping and ultraviolet (UV) light polymerization. Pillars within fluidic platforms are used to deterministically deform photosensitive precursor fluid streams. The channels are then illuminated with patterned UV light to polymerize the photosensitive fluid, creating particles with multi-scale 3D geometries. The fundamental advantages of optofluidic fabrication include high-resolution, multi-scalability, dynamic tunability, simple operation and great potential for bulk fabrication with full automation. Through different combinations of pillar configurations, flow rates and UV light patterns, an infinite set of 3D-shaped particles is available, and a variety are demonstrated.

Peculiar bonding associated with atomic doping and hidden honeycombs in borophene

NASA Astrophysics Data System (ADS)

Lee, Chi-Cheng; Feng, Baojie; D'angelo, Marie; Yukawa, Ryu; Liu, Ro-Ya; Kondo, Takahiro; Kumigashira, Hiroshi; Matsuda, Iwao; Ozaki, Taisuke

2018-02-01

Engineering atomic-scale structures allows great manipulation of physical properties and chemical processes for advanced technology. We show that the B atoms deployed at the centers of honeycombs in boron sheets, borophene, behave as nearly perfect electron donors for filling the graphitic σ bonding states without forming additional in-plane bonds by first-principles calculations. The dilute electron density distribution owing to the weak bonding surrounding the center atoms provides easier atomic-scale engineering and is highly tunable via in-plane strain, promising for practical applications, such as modulating the extraordinarily high thermal conductance that exceeds the reported value in graphene. The hidden honeycomb bonding structure suggests an unusual energy sequence of core electrons that has been verified by our high-resolution core-level photoelectron spectroscopy measurements. With the experimental and theoretical evidence, we demonstrate that borophene exhibits a peculiar bonding structure and is distinctive among two-dimensional materials.

Quantum confinement-induced tunable exciton states in graphene oxide

PubMed Central

Lee, Dongwook; Seo, Jiwon; Zhu, Xi; Lee, Jiyoul; Shin, Hyeon-Jin; Cole, Jacqueline M.; Shin, Taeho; Lee, Jaichan; Lee, Hangil; Su, Haibin

2013-01-01

Graphene oxide has recently been considered to be a potential replacement for cadmium-based quantum dots due to its expected high fluorescence. Although previously reported, the origin of the luminescence in graphene oxide is still controversial. Here, we report the presence of core/valence excitons in graphene-based materials, a basic ingredient for optical devices, induced by quantum confinement. Electron confinement in the unreacted graphitic regions of graphene oxide was probed by high resolution X-ray absorption near edge structure spectroscopy and first-principles calculations. Using experiments and simulations, we were able to tune the core/valence exciton energy by manipulating the size of graphitic regions through the degree of oxidation. The binding energy of an exciton in highly oxidized graphene oxide is similar to that in organic electroluminescent materials. These results open the possibility of graphene oxide-based optoelectronic device technology. PMID:23872608

Spatially resolved multicolor CsPbX 3 nanowire heterojunctions via anion exchange

DOE PAGES

Dou, Letian; Lai, Minliang; Kley, Christopher S.; ...

2017-06-26

Halide perovskites are promising semiconductor materials for solution-processed optoelectronic devices. Their strong ionic bonding nature results in highly dynamic crystal lattices, inherently allowing rapid ion exchange at the solid–vapor and solid–liquid interface. In this paper, we show that the anion-exchange chemistry can be precisely controlled in single-crystalline halide perovskite nanomaterials when combined with nanofabrication techniques. We demonstrate spatially resolved multicolor CsPbX 3 (X = Cl, Br, I, or alloy of two halides) nanowire heterojunctions with a pixel size down to 500 nm with the photoluminescence tunable over the entire visible spectrum. In addition, the heterojunctions show distinct electronic states acrossmore » the interface, as revealed by Kelvin probe force microscopy. Finally, these perovskite heterojunctions represent key building blocks for high-resolution multicolor displays beyond current state-of-the-art technology as well as high-density diode/transistor arrays.« less

Asymmetric mass acquisition in LaBi. Topological semimetal candidate

DOE PAGES

Wu, Yun; Kong, Tai; Wang, Lin-Lin; ...

2016-08-18

We use our high resolution He-lamp-based, tunable laser-based angle-resolved photoemission spectroscopy measurements and density functional theory calculations to study the electronic properties of LaBi, a binary system that was proposed to be a member of a new family of topological semimetals. Both bulk and surface bands are present in the spectra. Furthermore, the dispersion of the surface state is highly unusual. It resembles a Dirac cone, but upon closer inspection we can clearly detect an energy gap. The bottom band follows roughly a parabolic dispersion. The dispersion of the top band remains very linear, “V” -shape like, with the tipmore » approaching very closely to the extrapolated location of Dirac point. Finally, such asymmetric mass acquisition is highly unusual and opens a possibility of a new topological phenomenon that has yet to be understood.« less

Research about the high precision temperature measurement

NASA Astrophysics Data System (ADS)

Lin, J.; Yu, J.; Zhu, X.; Zeng, Z.; Deng, Y.

2012-12-01

High precision temperature control system is one of most important support conditions for tunable birefringent filter.As the first step,we researched some high precision temperature measurement methods for it. Firstly, circuits with a 24 bit ADC as the sensor's reader were carefully designed; Secondly, an ARM porcessor is used as the centrol processing unit, it provides sufficient reading and procesing ability; Thirdly, three kinds of sensors, PT100, Dale 01T1002-5 thermistor, Wheatstone bridge(constructed by pure copper and manganin) as the senor of the temperature were tested respectively. The resolution of the measurement with these three kinds of sensors are all better than 0.001 that's enough for 0.01 stability temperature control. Comparatively, Dale 01T1002-5 thermistor could get the most accurate temperature of the key point, Wheatstone bridge could get the most accurate mean temperature of the whole layer, both of them will be used in our futrue temperature controll system.

Noise Suppression on the Tunable Laser for Precise Cavity Length Displacement Measurement.

PubMed

Šmíd, Radek; Čížek, Martin; Mikel, Břetislav; Hrabina, Jan; Lazar, Josef; Číp, Ondřej

2016-09-06

The absolute distance between the mirrors of a Fabry-Perot cavity with a spacer from an ultra low expansion material was measured by an ultra wide tunable laser diode. The DFB laser diode working at 1542 nm with 1.5 MHz linewidth and 2 nm tuning range has been suppressed with an unbalanced heterodyne fiber interferometer. The frequency noise of laser has been suppressed by 40 dB across the Fourier frequency range 30-300 Hz and by 20 dB up to 4 kHz and the linewidth of the laser below 300 kHz. The relative resolution of the measurement was 10 - 9 that corresponds to 0.3 nm (sub-nm) for 0.178 m long cavity with ability of displacement measurement of 0.5 mm.

Tunable output-frequency filter algorithm for imaging through scattering media under LED illumination

NASA Astrophysics Data System (ADS)

Zhou, Meiling; Singh, Alok Kumar; Pedrini, Giancarlo; Osten, Wolfgang; Min, Junwei; Yao, Baoli

2018-03-01

We present a tunable output-frequency filter (TOF) algorithm to reconstruct the object from noisy experimental data under low-power partially coherent illumination, such as LED, when imaging through scattering media. In the iterative algorithm, we employ Gaussian functions with different filter windows at different stages of iteration process to reduce corruption from experimental noise to search for a global minimum in the reconstruction. In comparison with the conventional iterative phase retrieval algorithm, we demonstrate that the proposed TOF algorithm achieves consistent and reliable reconstruction in the presence of experimental noise. Moreover, the spatial resolution and distinctive features are retained in the reconstruction since the filter is applied only to the region outside the object. The feasibility of the proposed method is proved by experimental results.

Tunable nanoblock lasers and stretching sensors.

PubMed

Lu, T W; Wang, C; Hsiao, C F; Lee, P T

2016-09-22

Reconfigurable, reliable, and robust nanolasers with wavelengths tunable in the telecommunication bands are currently being sought after for use as flexible light sources in photonic integrated circuits. Here, we propose and demonstrate tunable nanolasers based on 1D nanoblocks embedded within stretchable polydimethylsiloxane. Our lasers show a large wavelength tunability of 7.65 nm per 1% elongation. Moreover, this tunability is reconfigurable and reliable under repeated stretching/relaxation tests. By applying excessive stretching, wide wavelength tuning over a range of 80 nm (spanning the S, C, and L telecommunication bands) is successfully demonstrated. Furthermore, as a stretching sensor, an enhanced wavelength response to elongation of 9.9 nm per % is obtained via the signal differential from two nanoblock lasers positioned perpendicular to each other. The minimum detectable elongation is as small as 0.056%. Nanoblock lasers can function as reliable tunable light sources in telecommunications and highly sensitive on-chip structural deformation sensors.

Wavelength-tunable Hermite-Gaussian modes and an orbital-angular-momentum-tunable vortex beam in a dual-off-axis pumped Yb:CALGO laser.

PubMed

Shen, Yijie; Meng, Yuan; Fu, Xing; Gong, Mali

2018-01-15

A dual-off-axis pumping scheme is presented to generate wavelength-tunable high-order Hermite-Gaussian (HG) modes in Yb:CaGdAlO 4 lasers. The mode and wavelength can be actively controlled by the off-axis displacements and pump power. The purities of the output HG modes are quantified by intensity distributions and the measured M 2 values. The highest order reaches m=15 for stable HG m,0 mode, and wavelength-tunable width is about 10 nm. Moreover, through externally converting the HG m,0 modes, the vortex beams carrying orbital angular momentum (OAM) with a large OAM-tunable range from ±1ℏ to ±15ℏ are produced. This work is effective for largely scaling the spectral and OAM tunable ranges of optical vortex beams.

High power tunable mid-infrared optical parametric oscillator enabled by random fiber laser.

PubMed

Wu, Hanshuo; Wang, Peng; Song, Jiaxin; Ye, Jun; Xu, Jiangming; Li, Xiao; Zhou, Pu

2018-03-05

Random fiber laser, as a kind of novel fiber laser that utilizes random distributed feedback as well as Raman gain, has become a research focus owing to its advantages of wavelength flexibility, modeless property and output stability. Herein, a tunable optical parametric oscillator (OPO) enabled by a random fiber laser is reported for the first time. By exploiting a tunable random fiber laser to pump the OPO, the central wavelength of idler light can be continuously tuned from 3977.34 to 4059.65 nm with stable temporal average output power. The maximal output power achieved is 2.07 W. So far as we know, this is the first demonstration of a continuous-wave tunable OPO pumped by a tunable random fiber laser, which could not only provide a new approach for achieving tunable mid-infrared (MIR) emission, but also extend the application scenarios of random fiber lasers.

Green high-power tunable external-cavity GaN diode laser at 515  nm.

PubMed

Chi, Mingjun; Jensen, Ole Bjarlin; Petersen, Paul Michael

2016-09-15

A 480 mW green tunable diode laser system is demonstrated for the first time to our knowledge. The laser system is based on a GaN broad-area diode laser and Littrow external-cavity feedback. The green laser system is operated in two modes by switching the polarization direction of the laser beam incident on the grating. When the laser beam is p-polarized, an output power of 50 mW with a tunable range of 9.2 nm is achieved. When the laser beam is s-polarized, an output power of 480 mW with a tunable range of 2.1 nm is obtained. This constitutes the highest output power from a tunable green diode laser system.

UV Raman scattering measurements in a Mach 2 H2-air flame for assessment of CFD models

NASA Technical Reports Server (NTRS)

Cheng, T. S.; Wehrmeyer, J. A.; Pitz, R. W.; Jarrett, O., Jr.; Northam, G. B.

1991-01-01

An UV narrowband tunable excimer laser is used for spontaneous Raman scattering measurements in hydrogen diffusion flames. The UV Raman system is characterized by a repetition rate of about 100 Hz, a temporal resolution of about 20 ns, and a spatial resolution of about 0.4 mm. It is concluded that a single KrF excimer laser based on spontaneous Raman scattering in conjunction with laser-induced predissociative fluorescence is capable of measuring instantaneously and simultaneously major species (H2, O2, N2, H2O), minor species (OH), and temperature.

Optically coupled methods for microwave impedance microscopy

NASA Astrophysics Data System (ADS)

Johnston, Scott R.; Ma, Eric Yue; Shen, Zhi-Xun

2018-04-01

Scanning Microwave Impedance Microscopy (MIM) measurement of photoconductivity with 50 nm resolution is demonstrated using a modulated optical source. The use of a modulated source allows for the measurement of photoconductivity in a single scan without a reference region on the sample, as well as removing most topographical artifacts and enhancing signal to noise as compared with unmodulated measurement. A broadband light source with a tunable monochrometer is then used to measure energy resolved photoconductivity with the same methodology. Finally, a pulsed optical source is used to measure local photo-carrier lifetimes via MIM, using the same 50 nm resolution tip.

High resolution laser-based detection of ammonia

NASA Astrophysics Data System (ADS)

Giubileo, G.; Puiu, A.; Dell'Unto, F.; Tomasi, M.; Fagnani, A.

2009-02-01

In the present paper we compare the response of two types of photoacoustic cells (resonant and nonresonant) to determine the amount of ammonia volatilized from biological liquid samples at constant temperature, pressure and pH. The home made detector was a photoacoustic spectroscopy apparatus developed by Molecular Spectroscopy Laboratory staff at ENEA Frascati Research Centre in Italy. The sensor makes use of photo-acoustic cells equipped with commercially available high sensitivity miniaturized microphones. The radiation source was a line-tunable stabilized 10 W CW CO2 laser. Ammonia measurements were performed by tuning the laser source on the 9R30 laser line (9.2197 µm radiation wavelength). Ammonium chloride standard solutions were prepared by us in laboratory, to serve as reproducible ideal samples. The photoacoustic response of the two type of photoacoustic cells was determined and compared. The feasibility study was reported.

Detection et caracterisation de naines brunes et exoplanetes avec un filtre accordable pour applications dans l'espace

NASA Astrophysics Data System (ADS)

Ingraham, Patrick Jon

This thesis determines the capability of detecting faint companions in the presence of speckle noise when performing space-based high-contrast imaging through spectral differential imagery (SDI) using a low-order Fabry-Perot etalon as a tunable filter. The performance of such a tunable filter is illustrated through the Tunable Filter Imager (TFI), an instrument designed for the James Webb Space Telescope (JWST). Using a TFI prototype etalon and a custom designed test bed, the etalon's ability to perform speckle-suppression through SDI is demonstrated experimentally. Improvements in contrast vary with separation, ranging from a factor of ˜10 at working angles greater than 11 lambda/D and increasing up to a factor of ˜60 at 5 lambda/D. These measurements are consistent with a Fresnel optical propagation model which shows the speckle suppression capability is limited by the test bed and not the etalon. This result demonstrates that a tunable filter is an attractive option to perform high-contrast imaging through SDI. To explore the capability of space-based SDI using an etalon, we perform an end-to-end Fresnel propagation of JWST and TFI. Using this simulation, a contrast improvement ranging from a factor of ˜7 to ˜100 is predicted, depending on the instrument's configuration. The performance of roll-subtraction is simulated and compared to that of SDI. The SDI capability of the Near-Infrared Imager and Slitless Spectrograph (NIRISS), the science instrument module to replace TFI in the JWST Fine Guidance Sensor is also determined. Using low resolution, multi-band (0.85-2.4 microm) multi-object spectroscopy, 104 objects towards the central region of the Orion Nebular Cluster have been assigned spectral types including 7 new brown dwarfs, and 4 new planetary mass candidates. These objects are useful for determining the substellar initial mass function and for testing evolutionary and atmospheric models of young stellar and substellar objects. Using the measured H band magnitudes, combined with our determined extinction values, the classified objects are used to create an Hertzsprung-Russell diagram for the cluster. Our results indicate a single epoch of star formation beginning ˜1 Myr ago. The initial mass function of the cluster is derived and found to be consistent with the values determined for other young clusters and the galactic disk.

Compositionally Graded Multilayer Ceramic Capacitors.

PubMed

Song, Hyun-Cheol; Zhou, Jie E; Maurya, Deepam; Yan, Yongke; Wang, Yu U; Priya, Shashank

2017-09-27

Multilayer ceramic capacitors (MLCC) are widely used in consumer electronics. Here, we provide a transformative method for achieving high dielectric response and tunability over a wide temperature range through design of compositionally graded multilayer (CGML) architecture. Compositionally graded MLCCs were found to exhibit enhanced dielectric tunability (70%) along with small dielectric losses (<2.5%) over the required temperature ranges specified in the standard industrial classifications. The compositional grading resulted in generation of internal bias field which enhanced the tunability due to increased nonlinearity. The electric field tunability of MLCCs provides an important avenue for design of miniature filters and power converters.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Hyun-Cheol; Zhou, Jie E.; Maurya, Deepam

Multilayer ceramic capacitors (MLCC) are widely used in consumer electronics. In this paper, we provide a transformative method for achieving high dielectric response and tunability over a wide temperature range through design of compositionally graded multilayer (CGML) architecture. Compositionally graded MLCCs were found to exhibit enhanced dielectric tunability (70%) along with small dielectric losses (<2.5%) over the required temperature ranges specified in the standard industrial classifications. The compositional grading resulted in generation of internal bias field which enhanced the tunability due to increased nonlinearity. The electric field tunability of MLCCs provides an important avenue for design of miniature filters andmore » power converters.« less

Airborne tunable diode laser spectrometer for trace-gas measurement in the lower stratosphere

NASA Technical Reports Server (NTRS)

Podolske, James; Loewenstein, Max

1993-01-01

This paper describes the airborne tunable laser absorption spectrometer, a tunable diode laser instrument designed for in situ trace-gas measurement in the lower stratosphere from an ER-2 high-altitude research aircraft. Laser-wavelength modulation and second-harmonic detection are employed to achieve the required constituent detection sensitivity. The airborne tunable laser absorption spectrometer was used in two polar ozone campaigns, the Airborne Antarctic Ozone Experiment and the Airborne Arctic Stratospheric Expedition, and measured nitrous oxide with a response time of 1 s and an accuracy not greater than 10 percent.

Thermal, optical, and electrical engineering of an innovative tunable white LED light engine

NASA Astrophysics Data System (ADS)

Trivellin, Nicola; Meneghini, Matteo; Ferretti, Marco; Barbisan, Diego; Dal Lago, Matteo; Meneghesso, Gaudenzio; Zanoni, Enrico

2014-02-01

Color temperature, intensity and blue spectrum of the light affects the ganglion receptors in human brain stimulating the human nervous system. With this work we review different methods for obtaining tunable light emission spectra and propose an innovative white LED lighting system. By an in depth study of the thermal, electrical and optical characteristics of GaN and GaP based compound semiconductors for optoelectronics a specific tunable spectra has been designed. The proposed tunable white LED system is able to achieve high CRI (above 95) in a large CCT range (3000 - 5000K).

High-power, fixed, and tunable wavelength, grating-free cascaded Raman fiber lasers.

PubMed

Balaswamy, V; Arun, S; Aparanji, Santosh; Choudhury, Vishal; Supradeepa, V R

2018-04-01

Cascaded Raman lasers enable high powers at various wavelength bands inaccessible with conventional rare-earth-doped lasers. The input and output wavelengths of conventional implementations are fixed by the constituent fiber gratings necessary for cascaded Raman conversion. We demonstrate here a simple architecture for high-power, fixed, and wavelength tunable, grating-free, cascaded Raman conversion between different wavelength bands. The architecture is based on the recently proposed distributed feedback Raman lasers. Here, we implement a module which converts the ytterbium band to the eye-safe 1.5 μm region. We demonstrate pump-limited output powers of over 30 W in fixed and continuously wavelength tunable configurations.

Frequency-tunable superconducting resonators via nonlinear kinetic inductance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vissers, M. R.; Hubmayr, J.; Sandberg, M.

2015-08-10

We have designed, fabricated, and tested a frequency-tunable high-Q superconducting resonator made from a niobium titanium nitride film. The frequency tunability is achieved by injecting a DC through a current-directing circuit into the nonlinear inductor whose kinetic inductance is current-dependent. We have demonstrated continuous tuning of the resonance frequency in a 180 MHz frequency range around 4.5 GHz while maintaining the high internal quality factor Q{sub i} > 180 000. This device may serve as a tunable filter and find applications in superconducting quantum computing and measurement. It also provides a useful tool to study the nonlinear response of a superconductor. In addition,more » it may be developed into techniques for measurement of the complex impedance of a superconductor at its transition temperature and for readout of transition-edge sensors.« less

Effects of Temperature and Air Density Profiles on Ozone Lidar Retrievals

NASA Astrophysics Data System (ADS)

Kirgis, G.; Langford, A. O.; Senff, C. J.; Alvarez, R. J. _II, II

2017-12-01

The recent reduction in the primary U.S. National Ambient Air Quality Standard (NAAQS) for ozone (O3) from 75 to 70 parts-per-billion by volume (ppbv) adds urgency to the need for better understanding of the processes that control ground-level concentrations in the United States. While ground-based in situ sensors are capable of measuring ozone levels, they don't give any insight into upper air transport and mixing. Differential absorption lidars such as the NOAA/ESRL Tunable Optical Profiler for Aerosol and oZone (TOPAZ) measure continuous vertical ozone profiles with high spatial and temporal resolution. However, the retrieved ozone mixing ratios depend on the temperature and air density profiles used in the analysis. This study analyzes the ozone concentrations for seven field campaigns from 2013 to 2016 to evaluate the impact of the assumed pressure and temperature profiles on the ozone mixing ratio retrieval. Pressure and temperature profiles from various spatial and temporal resolution models (Modern Era Retrospective-Analysis for Research and Applications, NCEP/NCAR Reanalysis, NCEP North American Regional Reanalysis, Rapid Refresh, and High-Resolution Rapid Refresh) are compared to reference ozone profiles created with pressure and temperature profiles from ozonesondes launched close to the TOPAZ measurement site. The results show significant biases with respect to time of day and season, altitude, and location of the model-extracted profiles. Limitations and advantages of all datasets used will also be discussed.

Effect of crystal structure on strontium titanate thin films and their dielectric properties

NASA Astrophysics Data System (ADS)

Kampangkeaw, Satreerat

Strontium titanate (SrTiO3 or STO) has application in radio and microwave-frequency tunable capacitor devices particularly at low temperatures due to its high dielectric constant, low loss and the electric field tunability of its dielectric constant. The main goal of improving the performance in these devices is to increase the tunability and decrease the dielectric loss at the same time, especially at microwave frequencies. Thin films of STO however, show dramatic differences compared to the bulk. The dielectric constant of bulk STO increases nonlinearly from 300 at room temperature to 30000 at 4 K and the loss range is 10-3--10 -4. On the other hand. STO thin films, while showing a dielectric constant close to 300 at room temperature, typically reach a maximum between 1000 and 10000 in the 30 K to 100 K range before decreasing, and the high-loss range is 10-2--10-3. We have grown strontium titanate thin films using a pulsed laser deposition technique on substrates selected to have a small lattice mismatch between the film and substrate. Neodymium gallate (NdGaO3 or NGO) and lanthanum aluminate (LaAlO3 or LAO) substrates were good candidates due to only 1--2% mismatching. Film capacitor devices were fabricated with 25 micron gap separation. 1.5 mm total gap length and an overall 1 x 2 mm dimension using standard lithography and gold metal evaporative techniques. Their nonlinear dielectric constant and loss tangent were measured at low frequencies and also at 2 GHz, and from room temperature down to 4 K. The resulting films show significant variations of dielectric properties with position on the substrates with respect to the deposition plume axis. In the presence of DC electric fields up to +/-4 V/mum, STO films show improved dielectric tunability and low loss in regions far from the plume axis. We found that the films grown on NCO have lower dielectric loss than those on LAO due to a closer match of the NCO lattice to that of STO. We investigated the possible causes that make dielectric behavior in STO thin films different from the bulk. We characterized such film structures as lattice parameters, out-of-plane grain size, in-plane grain size, thickness, roughness, strains, and defects using ellipsometry, atomic force microscopy, and a high-resolution X-ray diffractometry. In plane grain size and percentage of defects were found to play a major role on the dielectric performance of the films.

Absolute detector-based spectrally tunable radiant source using digital micromirror device and supercontinuum fiber laser.

PubMed

Li, Zhigang; Wang, Xiaoxu; Zheng, Yuquan; Li, Futian

2017-06-10

High-accuracy absolute detector-based spectroradiometric calibration techniques traceable to cryogenic absolute radiometers have made progress rapidly in recent decades under the impetus of atmospheric quantitative spectral remote sensing. A high brightness spectrally tunable radiant source using a supercontinuum fiber laser and a digital micromirror device (DMD) has been developed to meet demands of spectroradiometric calibrations for ground-based, aeronautics-based, and aerospace-based remote sensing instruments and spectral simulations of natural scenes such as the sun and atmosphere. Using a supercontinuum fiber laser as a radiant source, the spectral radiance of the spectrally tunable radiant source is 20 times higher than the spectrally tunable radiant source using conventional radiant sources such as tungsten halogen lamps, xenon lamps, or LED lamps, and the stability is better than ±0.3%/h. Using a DMD, the spectrally tunable radiant source possesses two working modes. In narrow-band modes, it is calibrated by an absolute detector, and in broad-band modes, it can calibrate for remote sensing instrument. The uncertainty of the spectral radiance of the spectrally tunable radiant source is estimated at less than 1.87% at 350 nm to 0.85% at 750 nm, and compared to only standard lamp-based calibration, a greater improvement is gained.

Thermal tuning On narrow linewidth fiber laser

NASA Astrophysics Data System (ADS)

Han, Peiqi; Liu, Tianshan; Gao, Xincun; Ren, Shiwei

2010-10-01

At present, people have been dedicated to high-speed and large-capacity optical fiber communication system. Studies have been shown that optical wavelength division multiplexing (WDM) technology is an effective means of communication to increase the channel capacity. Tunable lasers have very important applications in high-speed, largecapacity optical communications, and distributed sensing, it can provide narrow linewidth and tunable laser for highspeed optical communication. As the erbium-doped fiber amplifier has a large gain bandwidth, the erbium-doped fiber laser can be achieved lasing wavelength tunable by adding a tunable filter components, so tunable filter device is the key components in tunable fiber laser.At present, fiber laser wavelength is tuned by PZT, if thermal wavelength tuning is combined with PZT, a broader range of wavelength tuning is appearance . Erbium-doped fiber laser is used in the experiments,the main research is the physical characteristics of fiber grating temperature-dependent relationship and the fiber grating laser wavelength effects. It is found that the fiber laser wavelength changes continuously with temperature, tracking several temperature points observed the self-heterodyne spectrum and found that the changes in spectra of the 3dB bandwidth of less than 1kHz, and therefore the fiber laser with election-mode fiber Bragg grating shows excellent spectral properties and wavelength stability.

High yield and ultrafast sources of electrically triggered entangled-photon pairs based on strain-tunable quantum dots.

PubMed

Zhang, Jiaxiang; Wildmann, Johannes S; Ding, Fei; Trotta, Rinaldo; Huo, Yongheng; Zallo, Eugenio; Huber, Daniel; Rastelli, Armando; Schmidt, Oliver G

2015-12-01

Triggered sources of entangled photon pairs are key components in most quantum communication protocols. For practical quantum applications, electrical triggering would allow the realization of compact and deterministic sources of entangled photons. Entangled-light-emitting-diodes based on semiconductor quantum dots are among the most promising sources that can potentially address this task. However, entangled-light-emitting-diodes are plagued by a source of randomness, which results in a very low probability of finding quantum dots with sufficiently small fine structure splitting for entangled-photon generation (∼10(-2)). Here we introduce strain-tunable entangled-light-emitting-diodes that exploit piezoelectric-induced strains to tune quantum dots for entangled-photon generation. We demonstrate that up to 30% of the quantum dots in strain-tunable entangled-light-emitting-diodes emit polarization-entangled photons. An entanglement fidelity as high as 0.83 is achieved with fast temporal post selection. Driven at high speed, that is 400 MHz, strain-tunable entangled-light-emitting-diodes emerge as promising devices for high data-rate quantum applications.

Synthesis of Large-Size 1T' ReS2x Se2(1-x) Alloy Monolayer with Tunable Bandgap and Carrier Type.

PubMed

Cui, Fangfang; Feng, Qingliang; Hong, Jinhua; Wang, Renyan; Bai, Yu; Li, Xiaobo; Liu, Dongyan; Zhou, Yu; Liang, Xing; He, Xuexia; Zhang, Zhongyue; Liu, Shengzhong; Lei, Zhibin; Liu, Zonghuai; Zhai, Tianyou; Xu, Hua

2017-12-01

Chemical vapor deposition growth of 1T' ReS 2 x Se 2(1- x ) alloy monolayers is reported for the first time. The composition and the corresponding bandgap of the alloy can be continuously tuned from ReSe 2 (1.32 eV) to ReS 2 (1.62 eV) by precisely controlling the growth conditions. Atomic-resolution scanning transmission electron microscopy reveals an interesting local atomic distribution in ReS 2 x Se 2(1- x ) alloy, where S and Se atoms are selectively occupied at different X sites in each Re-X 6 octahedral unit cell with perfect matching between their atomic radius and space size of each X site. This structure is much attractive as it can induce the generation of highly desired localized electronic states in the 2D surface. The carrier type, threshold voltage, and carrier mobility of the alloy-based field effect transistors can be systematically modulated by tuning the alloy composition. Especially, for the first time the fully tunable conductivity of ReS 2 x Se 2(1- x ) alloys from n-type to bipolar and p-type is realized. Owing to the 1T' structure of ReS 2 x Se 2(1- x ) alloys, they exhibit strong anisotropic optical, electrical, and photoelectric properties. The controllable growth of monolayer ReS 2 x Se 2(1- x ) alloy with tunable bandgaps and electrical properties as well as superior anisotropic feature provides the feasibility for designing multifunctional 2D optoelectronic devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Generation of intensity-tunable structural color from helical photonic crystals for full color reflective-type display.

PubMed

Kim, Se-Um; Lee, Sin-Hyung; Lee, In-Ho; Lee, Bo-Yeon; Na, Jun-Hee; Lee, Sin-Doo

2018-05-14

A new concept of intensity-tunable structural coloration is proposed on the basis of a helical photonic crystal (HPC). The HPCs are constructed from a mixture of chiral reactive mesogens by spin-coating, followed by the photo-polymerization. A liquid crystal (LC) layer, being homogeneously aligned, is prepared on the HPCs to serve as a tunable waveplate. The electrical modulation of the phase retardation through the LC layer directly leads to the intensity-tunable Bragg reflection from the HPCs upon the incidence of the polarized light. The bandwidths of the structural colors are found to be well preserved regardless of the applied voltage. A prototype of a full color reflective-type display, incorporated with three primary color units, is demonstrated. Our concept of decoupling two mutually independent functions, the intensity modulation by the tunable waveplate and the color reflection by the HPCs provides a simple and powerful way of producing a full color reflective-type display which possesses high color purity, high optical efficiency, the cycling durability, and the design flexibility.

Local Oscillator Sub-Systems for Array Receivers in the 1-3 THz Range

NASA Technical Reports Server (NTRS)

Mehdi, Imran; Siles, Jose V.; Maestrini, Alain; Lin, Robert; Lee, Choonsup; Schlecht, Erich; Chattopadhyay, Goutam

2012-01-01

Recent results from the Heterodyne Instrument for the Far-Infrared (HIFI) on the Herschel Space Telescope have confirmed the usefulness of high resolution spectroscopic data for a better understanding of our Universe. This paper will explore the current status of tunable local oscillator sources with emphasis on building a multi-pixel LO subsystem for the scientifically important CII line around 1908 GHz. Recent results have shown that over 50 microwatts of output power at 1.9 THz are possible with an optimized single pixel LO chain. These power levels are now sufficient to pump array receivers in this frequency range. Further power enhancement can be obtained by cooling the chain to 120 K or by utilizing in-phase power combining technology.

Tunable photonic nanojet formed by generalized Luneburg lens.

PubMed

Mao, Xiurun; Yang, Yang; Dai, Haitao; Luo, Dan; Yao, Baoli; Yan, Shaohui

2015-10-05

Nanojet has been emerging as an interesting topic in variety photonics applications. In this paper, inspired by the properties of generalized Luneburg lens (GLLs), a two-dimensional photonic nanojet system has been developed, which focal distance can be tuned by engineering the refractive index profile of GLLs. Simulation and analysis results show that the maximum light intensity, transverse and longitudinal dimensions of the photonic nanojet are dependent on the focal distance of the GLLs, thereby, by simply varying the focal distance, it is possible to obtain localized photon fluxes with different power characteristics and spatial dimensions. This can be of interest for many promising applications, such as high-resolution optical detection, optical manipulation, technology of direct-write nano-patterning and nano-lithography.

Development of a high spectral resolution lidar based on confocal Fabry-Perot spectral filters.

PubMed

Hoffman, David S; Repasky, Kevin S; Reagan, John A; Carlsten, John L

2012-09-01

The high spectral resolution lidar (HSRL) instrument described in this paper utilizes the fundamental and second-harmonic output from an injection seeded Nd:YAG laser as the laser transmitter. The light scattered in the atmosphere is collected using a commercial Schmidt-Cassegrain telescope with the optical receiver train first splitting the fundamental and second-harmonic return signal with the fundament light monitored using an avalanche photodiode. The second-harmonic return signal is mode matched into a tunable confocal Fabry-Perot (CFP) interferometer with a free spectral range of 7.5 GHz and a finesse of 50.7 (312) at 532 nm (1064 nm) placed in the optical receiver for spectrally filtering the molecular and aerosol return signals. The light transmitted through the CFP is used to monitor the aerosol return signal while the light reflected from the CFP is used to monitor the molecular return signal. Data collected with the HSRL are presented and inversion results are compared to a co-located solar radiometer, demonstrating the successful operation of the instrument. The CFP-based filtering technique successfully employed by this HSRL instrument is easily portable to other arbitrary wavelengths, thus allowing for the future development of multiwavelength HSRL instruments.

Digitally controlled analog proportional-integral-derivative (PID) controller for high-speed scanning probe microscopy

NASA Astrophysics Data System (ADS)

Dukic, Maja; Todorov, Vencislav; Andany, Santiago; Nievergelt, Adrian P.; Yang, Chen; Hosseini, Nahid; Fantner, Georg E.

2017-12-01

Nearly all scanning probe microscopes (SPMs) contain a feedback controller, which is used to move the scanner in the direction of the z-axis in order to maintain a constant setpoint based on the tip-sample interaction. The most frequently used feedback controller in SPMs is the proportional-integral (PI) controller. The bandwidth of the PI controller presents one of the speed limiting factors in high-speed SPMs, where higher bandwidths enable faster scanning speeds and higher imaging resolution. Most SPM systems use digital signal processor-based PI feedback controllers, which require analog-to-digital and digital-to-analog converters. These converters introduce additional feedback delays which limit the achievable imaging speed and resolution. In this paper, we present a digitally controlled analog proportional-integral-derivative (PID) controller. The controller implementation allows tunability of the PID gains over a large amplification and frequency range, while also providing precise control of the system and reproducibility of the gain parameters. By using the analog PID controller, we were able to perform successful atomic force microscopy imaging of a standard silicon calibration grating at line rates up to several kHz.

Digitally controlled analog proportional-integral-derivative (PID) controller for high-speed scanning probe microscopy.

PubMed

Dukic, Maja; Todorov, Vencislav; Andany, Santiago; Nievergelt, Adrian P; Yang, Chen; Hosseini, Nahid; Fantner, Georg E

2017-12-01

Nearly all scanning probe microscopes (SPMs) contain a feedback controller, which is used to move the scanner in the direction of the z-axis in order to maintain a constant setpoint based on the tip-sample interaction. The most frequently used feedback controller in SPMs is the proportional-integral (PI) controller. The bandwidth of the PI controller presents one of the speed limiting factors in high-speed SPMs, where higher bandwidths enable faster scanning speeds and higher imaging resolution. Most SPM systems use digital signal processor-based PI feedback controllers, which require analog-to-digital and digital-to-analog converters. These converters introduce additional feedback delays which limit the achievable imaging speed and resolution. In this paper, we present a digitally controlled analog proportional-integral-derivative (PID) controller. The controller implementation allows tunability of the PID gains over a large amplification and frequency range, while also providing precise control of the system and reproducibility of the gain parameters. By using the analog PID controller, we were able to perform successful atomic force microscopy imaging of a standard silicon calibration grating at line rates up to several kHz.

The 12 micron band of ethane: A spectral catalog from 765 cm(-1) to 900 cm(-1)

NASA Technical Reports Server (NTRS)

Atakan, A. K.; Blass, W. E.; Brault, J. W.; Daunt, S. J.; Halsey, G. W.; Jennings, D. E.; Reuter, D. C.; Susskind, J.

1983-01-01

The high resolution laboratory absorption spectrum of the 12 micro band of ethane gas is studied. The data were obtained using the McMath Solar Telescope 1 meter Fourier Transform interferometer at Kitt Peak National Observatory and tunable diode laser spectrometers at the University of Tennessee and NASA/Goddard Space Flight Center. Over 200 individual vibration rotation transitions were analyzed taking into account many higher order effects including torsional splitting. Line positions were reproduced to better than 0.001/cm. Both ground and upper state molecular constants were determined in the analysis. The experimental details, the analysis procedures and the results are addressed. A list of ethane transitions occurring near (14)CO2 laser lines needed for heterodyne searches for C2H6 in extraterrestrial sources is also included. A spectral catalog of the ethane nu sub g fundamental from 765/cm to 900/cm is provided. A high dispersion (1/cm 12 in.) plot of both the Kitt Peak interferometric data and a simulated spectrum with Doppler limited resolution, a table of over 8500 calculated transitions listed quantum number assignments, frequencies and intensities are provided.

Microwave dielectric properties of BNT-BT0.08 thin films prepared by sol-gel technique

NASA Astrophysics Data System (ADS)

Huitema, L.; Cernea, M.; Crunteanu, A.; Trupina, L.; Nedelcu, L.; Banciu, M. G.; Ghalem, A.; Rammal, M.; Madrangeas, V.; Passerieux, D.; Dutheil, P.; Dumas-Bouchiat, F.; Marchet, P.; Champeaux, C.

2016-04-01

We report for the first time the microwave characterization of 0.92(Bi0.5Na0.5)TiO3-0.08BaTiO3 (BNT-BT0.08) ferroelectric thin films fabricated by the sol-gel method and integrated in both planar and out-of-plane tunable capacitors for agile high-frequency applications and particularly on the WiFi frequency band from 2.4 GHz to 2.49 GHz. The permittivity and loss tangent of the realized BNT-BT0.08 layers have been first measured by a resonant cavity method working at 12.5 GHz. Then, we integrated the ferroelectric material in planar inter-digitated capacitors (IDC) and in out-of-plane metal-insulator-metal (MIM) devices and investigated their specific properties (dielectric tunability and losses) on the whole 100 MHz-15 GHz frequency domain. The 3D finite-elements electromagnetic simulations of the IDC capacitances are fitting very well with their measured responses and confirm the dielectric properties determined with the cavity method. While IDCs are not exhibiting an optimal tunability, the MIM capacitor devices with optimized Ir/MgO(100) bottom electrodes demonstrate a high dielectric tunability, of 30% at 2.45 GHz under applied voltages as low as 10 V, and it is reaching 50% under 20 V voltage bias at the same frequency. These high-frequency properties of the MIM devices integrating the BNT-BT0.08 films, combining a high tunability under low applied voltages indicate a wide integration potential for tunable devices in the microwave domain and particularly at 2.45 GHz, corresponding to the widely used industrial, scientific, and medical frequency band.

Synchrotron-based intra-venous K-edge digital subtraction angiography in a pig model: a feasibility study.

PubMed

Schültke, Elisabeth; Fiedler, Stefan; Nemoz, Christian; Ogieglo, Lissa; Kelly, Michael E; Crawford, Paul; Esteve, Francois; Brochard, Thierry; Renier, Michel; Requardt, Herwig; Le Duc, Geraldine; Juurlink, Bernhard; Meguro, Kotoo

2010-03-01

K-edge digital subtraction angiography (KEDSA) combined with the tunability of synchrotron beam yields an imaging technique that is highly sensitive to low concentrations of contrast agents. Thus, contrast agent can be administered intravenously, obviating the need for insertion of a guided catheter to deliver a bolus of contrast agent close to the target tissue. With the high-resolution detectors used at synchrotron facilities, images can be acquired at high spatial resolution. Thus, the KEDSA appears particularly suited for studies of neurovascular pathology in animal models, where the vascular diameters are significantly smaller than in human patients. This feasibility study was designed to test the suitability of KEDSA after intravenous injection of iodine-based contrast agent for use in a pig model. Four adult male pigs were used for our experiments. Neurovascular angiographic images were acquired using KEDSA with a solid state Germanium (Ge) detector at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. After intravenous injection of 0.9 ml/kg iodinated contrast agent (Xenetix), the peak iodine concentrations in the internal carotid and middle cerebral arteries reached 35 mg/ml. KEDSA images in radiography mode allowed the visualization of intracranial arteries of less than 1.5mm diameter. Copyright 2009 Elsevier Ireland Ltd. All rights reserved.

In situ IR and X-ray high spatial-resolution microspectroscopy measurements of multistep organic transformation in flow microreactor catalyzed by Au nanoclusters.

PubMed

Gross, Elad; Shu, Xing-Zhong; Alayoglu, Selim; Bechtel, Hans A; Martin, Michael C; Toste, F Dean; Somorjai, Gabor A

2014-03-05

Analysis of catalytic organic transformations in flow reactors and detection of short-lived intermediates are essential for optimization of these complex reactions. In this study, spectral mapping of a multistep catalytic reaction in a flow microreactor was performed with a spatial resolution of 15 μm, employing micrometer-sized synchrotron-based IR and X-ray beams. Two nanometer sized Au nanoclusters were supported on mesoporous SiO2, packed in a flow microreactor, and activated toward the cascade reaction of pyran formation. High catalytic conversion and tunable products selectivity were achieved under continuous flow conditions. In situ synchrotron-sourced IR microspectroscopy detected the evolution of the reactant, vinyl ether, into the primary product, allenic aldehyde, which then catalytically transformed into acetal, the secondary product. By tuning the residence time of the reactants in a flow microreactor a detailed analysis of the reaction kinetics was performed. An in situ micrometer X-ray absorption spectroscopy scan along the flow reactor correlated locally enhanced catalytic conversion, as detected by IR microspectroscopy, to areas with high concentration of Au(III), the catalytically active species. These results demonstrate the fundamental understanding of the mechanism of catalytic reactions which can be achieved by the detailed mapping of organic transformations in flow reactors.

Utilization of UV and IR Supercontinua in Gas-Phase Subpicosecond Kinetic Spectroscopy

NASA Astrophysics Data System (ADS)

Glownia, J. H.; Misewich, J.; Sorokin, P. P.

Through the work of photochemists extending over many decades, there now exists a wealth of information on the various reactions that photoexcited gas phase molecules undergo. Most of this information relates to the product molecules that are formed, either as the direct result of a primary photochemical act, such as photodissociation, or through subsequent secondary reactions, involving collisions with other molecules in the gas. Recently, there has been an extensive effort directed at determining the exact energy distributions of the primary products formed in photodissociation. With the use of nanosecond tunable-laser techniques, such as laser-induced fluorescence (LIF) and coherent anti-Stokes Raman spectroscopy (CARS), scientists have successfully determined the nascent electronic, vibrational, and rotational energy distributions of various diatomic fragments such as CN, OH, NO, and O2 that are directly formed in the photodissociation of many kinds of molecules. The ready availability of high-quality, tunable, nanosecond lasers has made determination of the above-mentioned collisionless energy distributions a relatively straightforward process. The determination of product translational energies has long effectively been handled by angularly resolved time-of-flight (TOF) spectroscopy, or by sub-Doppler resolution spectroscopy, including a recently improved version of the latter, velocity-aligned Doppler spectroscopy (Xu et al., 1986).

Tunable Diode Laser Absorption Spectroscopy Sensor for Calibration Free Humidity Measurements in Pure Methane and Low CO2 Natural Gas.

PubMed

Nwaboh, Javis Anyangwe; Pratzler, Sonja; Werhahn, Olav; Ebert, Volker

2017-05-01

We report a new direct tunable diode laser absorption spectroscopy (dTDLAS) sensor for absolute measurements of H 2 O in methane, ethane, propane, and low CO 2 natural gas. The sensor is operated with a 2.7 µm DFB laser, equipped with a high pressure single pass gas cell, and used to measure H 2 O amount of substance fractions in the range of 0.31-25 000 µmol/mol. Operating total gas pressures are up to 5000 hPa. The sensor has been characterized, addressing the traceability of the spectrometric results to the SI and the evaluation of the combined uncertainty, following the guide to the expression of uncertainty in measurement (GUM). The relative reproducibility of H 2 O amount of substance fraction measurements at 87 µmol/mol is 0.26% (0.23 µmol/mol). The maximum precision of the sensor was determined using a H 2 O in methane mixture, and found to be 40 nmol/mol for a time resolution of 100 s. This corresponds to a normalized detection limit of 330 nmol mol -1 ·m Hz -1/2 . The relative combined uncertainty of H 2 O amount fraction measurements delivered by the sensor is 1.2%.

The temperature measurement research for high-speed flow based on tunable diode laser absorption spectroscopy

NASA Astrophysics Data System (ADS)

Di, Yue; Jin, Yi; Jiang, Hong-liang; Zhai, Chao

2013-09-01

Due to the particularity of the high-speed flow, in order to accurately obtain its' temperature, the measurement system should has some characteristics of not interfereing with the flow, non-contact measurement and high time resolution. The traditional measurement method cannot meet the above requirements, however the measurement method based on tunable diode laser absorption spectroscopy (TDLAS) technology can meet the requirements for high-speed flow temperature measurement. When the near-infared light of a specific frequency is through the media to be measured, it will be absorbed by the water vapor molecules and then the transmission light intensity is detected by the detector. The temperature of the water vapor which is also the high-speed flow temperature, can be accurately obtained by the Beer-Lambert law. This paper focused on the research of absorption spectrum method for high speed flow temperature measurement with the scope of 250K-500K. Firstly, spectral line selection method for low temperature measurement of high-speed flow is discussed. Selected absorption lines should be isolated and have a high peak absorption within the range of 250-500K, at the same time the interference of the other lines should be avoided, so that a high measurement accuracy can be obtained. According to the near-infrared absorption spectra characteristics of water vapor, four absorption lines at the near 1395 nm and 1409 nm are selected. Secondly, a system for the temperature measurement of the water vapor in the high-speed flow is established. Room temperature are measured through two methods, direct absorption spectroscopy (DAS) and wavelength modulation spectroscopy (WMS) ,the results show that this system can realize on-line measurement of the temperature and the measurement error is about 3%. Finally, the system will be used for temperature measurement of the high-speed flow in the shock tunnel, its feasibility of measurement is analyzed.

Compositionally Graded Multilayer Ceramic Capacitors

DOE PAGES

Song, Hyun-Cheol; Zhou, Jie E.; Maurya, Deepam; ...

2017-09-27

Multilayer ceramic capacitors (MLCC) are widely used in consumer electronics. In this paper, we provide a transformative method for achieving high dielectric response and tunability over a wide temperature range through design of compositionally graded multilayer (CGML) architecture. Compositionally graded MLCCs were found to exhibit enhanced dielectric tunability (70%) along with small dielectric losses (<2.5%) over the required temperature ranges specified in the standard industrial classifications. The compositional grading resulted in generation of internal bias field which enhanced the tunability due to increased nonlinearity. The electric field tunability of MLCCs provides an important avenue for design of miniature filters andmore » power converters.« less

Tunable rejection filters with ultra-wideband using zeroth shear mode plate wave resonators

NASA Astrophysics Data System (ADS)

Kadota, Michio; Sannomiya, Toshio; Tanaka, Shuji

2017-07-01

This paper reports wide band rejection filters and tunable rejection filters using ultra-wideband zeroth shear mode (SH0) plate wave resonators. The frequency range covers the digital TV band in Japan that runs from 470 to 710 MHz. This range has been chosen to meet the TV white space cognitive radio requirements of rejection filters. Wide rejection bands were obtained using several resonators with different frequencies. Tunable rejection filters were demonstrated using Si diodes connected to the band rejection filters. Wide tunable ranges as high as 31% were measured by applying a DC voltage to the Si diodes.

Adaptive Tunable Laser Spectrometer for Space Applications

NASA Technical Reports Server (NTRS)

Flesch, Gregory; Keymeulen, Didier

2010-01-01

An architecture and process for the rapid prototyping and subsequent development of an adaptive tunable laser absorption spectrometer (TLS) are described. Our digital hardware/firmware/software platform is both reconfigurable at design time as well as autonomously adaptive in real-time for both post-integration and post-launch situations. The design expands the range of viable target environments and enhances tunable laser spectrometer performance in extreme and even unpredictable environments. Through rapid prototyping with a commercial RTOS/FPGA platform, we have implemented a fully operational tunable laser spectrometer (using a highly sensitive second harmonic technique). With this prototype, we have demonstrated autonomous real-time adaptivity in the lab with simulated extreme environments.

Arbitrary-ratio power splitter based on nonlinear multimode interference coupler

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tajaldini, Mehdi; Young Researchers and Elite Club, Baft Branch, Islamic Azad University, Baft; Jafri, Mohd Zubir Mat

2015-04-24

We propose an ultra-compact multimode interference (MMI) power splitter based on nonlinear effects from simulations using nonlinear modal propagation analysis (NMPA) cooperation with finite difference Method (FDM) to access free choice of splitting ratio. Conventional multimode interference power splitter could only obtain a few discrete ratios. The power splitting ratio may be adjusted continuously while the input set power is varying by a tunable laser. In fact, using an ultra- compact MMI with a simple structure that is launched by a tunable nonlinear input fulfills the problem of arbitrary-ratio in integrated photonics circuits. Silicon on insulator (SOI) is used asmore » the offered material due to the high contrast refractive index and Centro symmetric properties. The high-resolution images at the end of the multimode waveguide in the simulated power splitter have a high power balance, whereas access to a free choice of splitting ratio is not possible under the linear regime in the proposed length range except changes in the dimension for any ratio. The compact dimensions and ideal performance of the device are established according to optimized parameters. The proposed regime can be extended to the design of M×N arbitrary power splitters ratio for programmable logic devices in all optical digital signal processing. The results of this study indicate that nonlinear modal propagation analysis solves the miniaturization problem for all-optical devices based on MMI couplers to achieve multiple functions in a compact planar integrated circuit and also overcomes the limitations of previously proposed methods for nonlinear MMI.« less

Bandwidth tunable amplifier for recording biopotential signals.

PubMed

Hwang, Sungkil; Aninakwa, Kofi; Sonkusale, Sameer

2010-01-01

This paper presents a low noise, low power, bandwidth tunable amplifier for bio-potential signal recording applications. By employing depletion-mode pMOS transistor in diode configuration as a tunable sub pA current source to adjust the resistivity of MOS-Bipolar pseudo-resistor, the bandwidth is adjusted without any need for a separate band-pass filter stage. For high CMRR, PSRR and dynamic range, a fully differential structure is used in the design of the amplifier. The amplifier achieves a midband gain of 39.8dB with a tunable high-pass cutoff frequency ranging from 0.1Hz to 300Hz. The amplifier is fabricated in 0.18εm CMOS process and occupies 0.14mm(2) of chip area. A three electrode ECG measurement is performed using the proposed amplifier to show its feasibility for low power, compact wearable ECG monitoring application.

RF-MEMS tunable interdigitated capacitor and fixed spiral inductor for band pass filter applications

NASA Astrophysics Data System (ADS)

Bade, Ladon Ahmed; Dennis, John Ojur; Khir, M. Haris Md; Wen, Wong Peng

2016-11-01

This research presents the tunable Radio Frequency Micro Electromechanical Systems (RF-MEMS) coupled band-pass filter (BPF), which possess a wide tuning range and constructed by using the Chebyshev fourth degree equivalent circuit consisting of fixed inductors and interdigitated tunable capacitors. The suggested method was authenticated by designing a new tunable BPF with a 100% tuning range from 3.1 GHz to 4.9 GHz. The Metal Multi-User MEMS Process (Metal MUMPs) was involved in the process of design of this band-pass filter. It aimed to achieve the reconfiguration of frequencies and show high efficiency of RF in the applications that using Ultra Wide Band (UWB) such as wireless sensor networks. The RF performance of this filter was found to be very satisfactory due to its simple fabrication. Moreover, it showed less insertion loss of around 4 dB and high return loss of around 20 dB.

A spectrally tunable all-graphene-based flexible field-effect light-emitting device

NASA Astrophysics Data System (ADS)

Wang, Xiaomu; Tian, He; Mohammad, Mohammad Ali; Li, Cheng; Wu, Can; Yang, Yi; Ren, Tian-Ling

2015-07-01

The continuous tuning of the emission spectrum of a single light-emitting diode (LED) by an external electrical bias is of great technological significance as a crucial property in high-quality displays, yet this capability has not been demonstrated in existing LEDs. Graphene, a tunable optical platform, is a promising medium to achieve this goal. Here we demonstrate a bright spectrally tunable electroluminescence from blue (~450 nm) to red (~750 nm) at the graphene oxide/reduced-graphene oxide interface. We explain the electroluminescence results from the recombination of Poole-Frenkel emission ionized electrons at the localized energy levels arising from semi-reduced graphene oxide, and holes from the top of the π band. Tuning of the emission wavelength is achieved by gate modulation of the participating localized energy levels. Our demonstration of current-driven tunable LEDs not only represents a method for emission wavelength tuning but also may find applications in high-quality displays.

Flux-tunable heat sink for quantum electric circuits.

PubMed

Partanen, M; Tan, K Y; Masuda, S; Govenius, J; Lake, R E; Jenei, M; Grönberg, L; Hassel, J; Simbierowicz, S; Vesterinen, V; Tuorila, J; Ala-Nissila, T; Möttönen, M

2018-04-20

Superconducting microwave circuits show great potential for practical quantum technological applications such as quantum information processing. However, fast and on-demand initialization of the quantum degrees of freedom in these devices remains a challenge. Here, we experimentally implement a tunable heat sink that is potentially suitable for the initialization of superconducting qubits. Our device consists of two coupled resonators. The first resonator has a high quality factor and a fixed frequency whereas the second resonator is designed to have a low quality factor and a tunable resonance frequency. We engineer the low quality factor using an on-chip resistor and the frequency tunability using a superconducting quantum interference device. When the two resonators are in resonance, the photons in the high-quality resonator can be efficiently dissipated. We show that the corresponding loaded quality factor can be tuned from above 10 5 down to a few thousand at 10 GHz in good quantitative agreement with our theoretical model.

1.5 W high efficiency and tunable single-longitudinal-mode Ho:YLF ring laser based on Faraday effect.

PubMed

Wu, Jing; Ju, Youlun; Dai, Tongyu; Yao, Baoquan; Wang, Yuezhu

2017-10-30

We demonstrated an efficient and tunable single-longitudinal-mode Ho:YLF ring laser based on Faraday effect for application to measure atmospheric carbon dioxide (CO 2 ). Single-longitudinal-mode power at 2051.65 nm achieved 528 mW with the slope efficiency of 39.5% and the M 2 factor of 1.07, and the tunable range of about 178 GHz was obtained by inserting a Fabry-Perot (F-P) etalon with the thickness of 0.5 mm. In addition, the maximum single-longitudinal-mode power reached 1.5 W with the injected power of 528 mW at 2051.65 nm by master oscillator power amplifier (MOPA) technique. High efficiency and tunable single-longitudinal-mode based on Faraday effect around 2 μm has not been reported yet to the best of our knowledge.

Spatial Soliton Interactions for Photonic Switching. Part I

DTIC Science & Technology

2000-03-07

technique , a fully vectorial, first-order nonlinear wave equation that consistently includes terms two -orders beyond the slowly-varying amplitude , slowly...by using two tunable mode-locked Er-doped fiber lasers ," in Conference on Optical Fiber Communications, OSA Technical Digest Series, vol. 4, 1994...instead, based on optical logic gates. In addition, optical logic could be used for contention resolution, real-time encryption /decryption, and other

Broadband SLED-based light source (BeST-SLEDTM) and spectrometer

NASA Astrophysics Data System (ADS)

Yadid-Pecht, Orly; Dattner, Yonathan

2016-03-01

A small footprint, low power, cost effective single mode fiber coupled broadband light source and spectrometer is presented. It is based on Super Luminescent Diode (SLED) devices and a compact design enables coverage of the 1250 nm-1750 nm region with a total optical power of 50 mW at the output of the fiber. This Broad Spectrum Tunable Super Luminescent (BeST-SLEDTM) light source can operate at temperatures ranging from -40°C to 60°C, and resides in a custom designed 26-pin package. The fiber is a polarization maintaining fiber with a FC/APC connector at the output. Three variations of the BeST-SLEDTM were developed, BEST-SLED™ Bands, BeST-SLEDTM Tunable and BeST-SLEDTM FTNIR. In the Bands version six SLEDs were packaged allowing for one SLED on at a time or any combination of the SLEDs on. In the Tunable version an Acoustic Optical Tunable Filter (AOTF) was integrated into the package allowing the user to select one wavelength at a time to pass into the fiber with resolution of ~1 nm @1550nm. In the FTNIR version, a Silicon Photonic based interferometer (the Nano-SpecTM) was integrated into the package for a Fourier Transform Near Infrared based Spectrometer and light source. The BeST-SLEDTM is being used in process control applications such as steam quality measurements, oil in water, gas composition and air quality monitoring.

1THz synchronous tuning of two optical synthesizers

NASA Astrophysics Data System (ADS)

Neuhaus, Rudolf; Rohde, Felix; Benkler, Erik; Puppe, Thomas; Raab, Christoph; Unterreitmayer, Reinhard; Zach, Armin; Telle, Harald R.; Stuhler, Jürgen

2016-04-01

Single-frequency optical synthesizers (SFOS) provide an optical field with arbitrarily adjustable frequency and phase which is phase-coherently linked to a reference signal. Ideally, they combine the spectral resolution of narrow linewidth frequency stabilized lasers with the broad spectral coverage of frequency combs in a tunable fashion. In state-of-the-art SFOSs tuning across comb lines requires comb line order switching,1, 2 which imposes technical overhead with problems like forbidden frequency gaps or strong phase glitches. Conventional tunable lasers often tune over only tens of GHz before mode-hops occur. Here, we present a novel type of SFOSs, which relies on a serrodyne technique with conditional flyback,3 shifting the carrier frequency of the employed frequency comb without an intrusion into the comb generator. It utilizes a new continuously tunable diode laser that tunes mode-hop-free across the full gain spectrum of the integrated laser diode. We investigate the tuning behavior of two identical SFOSs that share a common reference, by comparing the phases of their output signals. Previously, we achieved phase-stable and cycle-slip free frequency tuning over 28.1 GHz with a maximum zero-to-peak phase deviation of 62 mrad4 when sharing a common comb generator. With the new continuously tunable lasers, the SFOSs tune synchronously across nearly 17800 comb lines (1 THz). The tuning range in this approach can be extended to the full bandwidth of the frequency comb and the 110 nm mode-hop-free tuning range of the diode laser.

Tunable diode laser optogalvanic spectroscopy of molecules

NASA Technical Reports Server (NTRS)

Webster, C. R.; Menzies, R. T.

1983-01-01

The laser optogalvanic (LOG) technique for studying molecular spectra has been extended for the first time to the infrared wavelength region. Portions of the NH3 nu-2 band at 9.5 microns and the NO2 nu-3 band at 6.2 microns have been recorded at Doppler-limited resolution using CW tunable diode lasers to probe dc electrical discharges in pure NH3 and an NO2/He gas mixture. Using adjustable electrode positions and an orthogonal geometry between the probe laser and the discharge axis, two contributions to the optogalvanic signal are identified: one which corresponds to an increase in discharge impedance and is seen only for irradiation of the negative glow region; and a second which corresponds to a decrease in discharge impedance and is seen for irradiation of all other discharge regions.

Noise Suppression on the Tunable Laser for Precise Cavity Length Displacement Measurement

PubMed Central

Šmíd, Radek; Čížek, Martin; Mikel, Břetislav; Hrabina, Jan; Lazar, Josef; Číp, Ondřej

2016-01-01

The absolute distance between the mirrors of a Fabry-Perot cavity with a spacer from an ultra low expansion material was measured by an ultra wide tunable laser diode. The DFB laser diode working at 1542 nm with 1.5 MHz linewidth and 2 nm tuning range has been suppressed with an unbalanced heterodyne fiber interferometer. The frequency noise of laser has been suppressed by 40 dB across the Fourier frequency range 30–300 Hz and by 20 dB up to 4 kHz and the linewidth of the laser below 300 kHz. The relative resolution of the measurement was 10−9 that corresponds to 0.3 nm (sub-nm) for 0.178 m long cavity with ability of displacement measurement of 0.5 mm. PMID:27608024

Color-tunable and high-efficiency organic light-emitting diode by adjusting exciton bilateral migration zone

NASA Astrophysics Data System (ADS)

Liu, Shengqiang; Wu, Ruofan; Huang, Jiang; Yu, Junsheng

2013-09-01

A voltage-controlled color-tunable and high-efficiency organic light-emitting diode (OLED) by inserting 16-nm N,N'-dicarbazolyl-3,5-benzene (mCP) interlayer between two complementary emitting layers (EMLs) was fabricated. The OLED emitted multicolor ranging from blue (77.4 cd/A @ 6 V), white (70.4 cd/A @ 7 V), to yellow (33.7 cd/A @ 9 V) with voltage variation. An equivalent model was proposed to reveal the color-tunable and high-efficiency emission of OLEDs, resulting from the swing of exciton bilateral migration zone near mCP/blue-EML interface. Also, the model was verified with a theoretical arithmetic using single-EML OLEDs to disclose the crucial role of mCP exciton adjusting layer.

Highly coherent tunable mid-infrared frequency comb pumped by supercontinuum at 1 µm

NASA Astrophysics Data System (ADS)

Jin, Lei; Yamanaka, Masahito; Sonnenschein, Volker; Tomita, Hideki; Iguchi, Tetsuo; Sato, Atsushi; Oh-hara, Toshinari; Nishizawa, Norihiko

2017-01-01

We report a tunable mid-infrared frequency comb working at 184 MHz, which is based on difference frequency generation in a periodically poled Mg-doped stoichiometric lithium tantalate (PPMgSLT) crystal pumped by high-power supercontinuum pulses. Supercontinuum pulses from two fibers with different dispersion properties were examined. With a photonic crystal fiber (PCF) having normal dispersion properties, a tunable wavelength range of 2.9-4.7 µm was achieved. With another PCF having zero dispersion at 1040 nm, a maximum power of 1.34 mW was observed at 3.9 µm. The high coherence of the pulses generated with this scheme was verified experimentally, and a fringe visibility of 0.90 was observed.

Multimodal transmission property in a liquid-filled photonic crystal fiber

NASA Astrophysics Data System (ADS)

Lin, Wei; Miao, Yinping; Song, Binbin; Zhang, Hao; Liu, Bo; Liu, Yange; Yan, Donglin

2015-02-01

The multimode interference (MMI) effect in a liquid-filled photonic crystal fiber (PCF) has been experimentally demonstrated by fully infiltrating the air-hole cladding of a solid-core PCF with the refractive index (RI) matching liquid whose RI is close to the silica background. Due to the weak mode confinement capability of the cladding region, several high-order modes are excited to establish the multimode interference effect. The multimode interferometer shows a good temperature tunability of 12.30 nm/K, which makes it a good candidate for a highly tunable optical filtering as well as temperature sensing applications. Furthermore, this MMI effect would have great promise in various applications such as highly sensitive multi-parameter sensing, tunable optically filtering, and surface-enhanced Raman scattering.

Wavelength-tunable Q-switched Raman fiber laser

NASA Astrophysics Data System (ADS)

Ye, Jun; Xu, Jiangming; Zhang, Hanwei; Wu, Jian; Zhou, Pu

2018-03-01

In this presentation, a wavelength-tunable Q-switched Raman fiber laser is presented for the first time, which has a backward pumped configuration, including a section of 3 km passive fiber, a homemade tunable pump source and a highly reflective fiber loop mirror. The output wavelength of the Raman fiber laser can be tuned continuously with ~44 nm range via adjusting the pump wavelength. By inserting an acoustic-optical modulator, the Q-value of the cavity can be switched between high and low level. As a result, pulsed output with a repetition rate of 500 kHz and duration time of 60-80 ns is achieved.

Wavelength and bandwidth tunable photonic stopband of ferroelectric liquid crystals.

PubMed

Ozaki, Ryotaro; Moritake, Hiroshi

2012-03-12

The chiral smectic C phase of ferroelectric liquid crystals (FLCs) has a self-assembling helical structure which is regarded as a one-dimensional pseudo-photonic crystal. It is well known that a stopband of a FLC can be tuned in wavelength domain by changing temperature or electric field. We here have demonstrated an FLC stopband with independently tunable wavelength and bandwidth by controlling temperature and incident angle. At highly oblique incidence, the stopband does not have polarization dependence. Furthermore, the bandwidth at highly oblique incidence is much wider than that at normal incidence. The mechanism of the tunable stopband is clarified by considering the reflection at oblique incidence.

Electrically tunable hole g factor of an optically active quantum dot for fast spin rotations

NASA Astrophysics Data System (ADS)

Prechtel, Jonathan H.; Maier, Franziska; Houel, Julien; Kuhlmann, Andreas V.; Ludwig, Arne; Wieck, Andreas D.; Loss, Daniel; Warburton, Richard J.

2015-04-01

We report a large g factor tunability of a single hole spin in an InGaAs quantum dot via an electric field. The magnetic field lies in the in-plane direction x , the direction required for a coherent hole spin. The electrical field lies along the growth direction z and is changed over a large range, 100 kV/cm. Both electron and hole g factors are determined by high resolution laser spectroscopy with resonance fluorescence detection. This, along with the low electrical-noise environment, gives very high quality experimental results. The hole g factor ghx depends linearly on the electric field Fz,d ghx/d Fz=(8.3 ±1.2 ) ×10-4 cm/kV, whereas the electron g factor gex is independent of electric field d gex/d Fz=(0.1 ±0.3 ) ×10-4 cm/kV (results averaged over a number of quantum dots). The dependence of ghx on Fz is well reproduced by a 4 ×4 k .p model demonstrating that the electric field sensitivity arises from a combination of soft hole confining potential, an In concentration gradient, and a strong dependence of material parameters on In concentration. The electric field sensitivity of the hole spin can be exploited for electrically driven hole spin rotations via the g tensor modulation technique and based on these results, a hole spin coupling as large as ˜1 GHz can be envisaged.

Planetary investigation utilizing an imaging spectrometer system based upon charge injection technology

NASA Technical Reports Server (NTRS)

Wattson, R. B.; Harvey, P.; Swift, R.

1975-01-01

An intrinsic silicon charge injection device (CID) television sensor array has been used in conjunction with a CaMoO4 colinear tunable acousto optic filter, a 61 inch reflector, a sophisticated computer system, and a digital color TV scan converter/computer to produce near IR images of Saturn and Jupiter with 10A spectral resolution and approximately 3 inch spatial resolution. The CID camera has successfully obtained digitized 100 x 100 array images with 5 minutes of exposure time, and slow-scanned readout to a computer. Details of the equipment setup, innovations, problems, experience, data and final equipment performance limits are given.

A simulation study for determination of refractive index dispersion of dielectric film from reflectance spectrum by using Paul wavelet

NASA Astrophysics Data System (ADS)

Tiryaki, Erhan; Coşkun, Emre; Kocahan, Özlem; Özder, Serhat

2017-02-01

In this work, the Continuous Wavelet Transform (CWT) with Paul wavelet was improved as a tool for determination of refractive index dispersion of dielectric film by using the reflectance spectrum of the film. The reflectance spectrum was generated theoretically in the range of 0.8333 - 3.3333 μm wavenumber and it was analyzed with presented method. Obtained refractive index determined from various resolution of Paul wavelet were compared with the input values, and the importance of the tunable resolution with Paul wavelet was discussed briefly. The noise immunity and uncertainty of the method was also studied.

Highly Tunable Aptasensing Microarrays with Graphene Oxide Multilayers

NASA Astrophysics Data System (ADS)

Jung, Yun Kyung; Lee, Taemin; Shin, Eeseul; Kim, Byeong-Su

2013-11-01

A highly tunable layer-by-layer (LbL)-assembled graphene oxide (GO) array has been devised for high-throughput multiplex protein sensing. In this array, the fluorescence of different target-bound aptamers labeled with dye is efficiently quenched by GO through fluorescence resonance energy transfer (FRET), and simultaneous multiplex target detection is performed by recovering the quenched fluorescence caused by specific binding between an aptamer and a protein. Thin GO films consisting of 10 bilayers displayed a high quenching ability, yielding over 85% fluorescence quenching with the addition of a 2 μM dye-labeled aptamer. The limit for human thrombin detection in the 6- and 10-bilayered GO array is estimated to be 0.1 and 0.001 nM, respectively, indicating highly tunable nature of LbL assembled GO multilayers in controlling the sensitivity of graphene-based FRET aptasensor. Furthermore, the GO chip could be reused up to four times simply by cleaning it with distilled water.

Yb fiber laser pumped mid-IR source based on difference frequency generation and its application to ammonia detection

NASA Technical Reports Server (NTRS)

Matsuoka, N.; Yamaguchi, S.; Nanri, K.; Fujioka, T.; Richter, D.; Tittel, F. K.

2001-01-01

A Yb fiber laser pumped cw narrow-linewidth tunable mid-IR source based on a difference frequency generation (DFG) in a periodically poled LiNbO3 (PPLN) crystal for trace gas detection was demonstrated. A high power Yb fiber laser and a distributed feedback (DFB) laser diode were used as DFG pump sources. This source generated mid-IR at 3 microns with a powers of 2.5 microW and a spectral linewidth of less than 30 MHz. A frequency tuning range of 300 GHz (10 cm-1) was obtained by varying the current and temperature of the DFB laser diode. A high-resolution NH3 absorption Doppler-broadened spectrum at 3295.4 cm-1 (3.0345 microns) was obtained at a cell pressure of 27 Pa from which a detection sensitivity of 24 ppm m was estimated.

Versatile mid-infrared frequency-comb referenced sub-Doppler spectrometer

NASA Astrophysics Data System (ADS)

Gambetta, A.; Vicentini, E.; Coluccelli, N.; Wang, Y.; Fernandez, T. T.; Maddaloni, P.; De Natale, P.; Castrillo, A.; Gianfrani, L.; Laporta, P.; Galzerano, G.

2018-04-01

We present a mid-IR high-precision spectrometer capable of performing accurate Doppler-free measurements with absolute calibration of the optical axis and high signal-to-noise ratio. The system is based on a widely tunable mid-IR offset-free frequency comb and a Quantum-Cascade-Laser (QCL). The QCL emission frequency is offset locked to one of the comb teeth to provide absolute-frequency calibration, spectral-narrowing, and accurate fine frequency tuning. Both the comb repetition frequency and QCL-comb offset frequency can be modulated to provide, respectively, slow- and fast-frequency-calibrated scanning capabilities. The characterisation of the spectrometer is demonstrated by recording sub-Doppler saturated absorption features of the CHF3 molecule at around 8.6 μm with a maximum signal-to-noise ratio of ˜7 × 103 in 10 s integration time, frequency-resolution of 160 kHz, and accuracy of less than 10 kHz.

An external-cavity quantum cascade laser operating near 5.2 µm combined with cavity ring-down spectroscopy for multi-component chemical sensing

NASA Astrophysics Data System (ADS)

Dutta Banik, Gourab; Maity, Abhijit; Som, Suman; Pal, Mithun; Pradhan, Manik

2018-04-01

We report on the performance of a widely tunable continuous wave mode-hop-free external-cavity quantum cascade laser operating at λ ~ 5.2 µm combined with cavity ring-down spectroscopy (CRDS) technique for high-resolution molecular spectroscopy. The CRDS system has been utilized for simultaneous and molecule-specific detection of several environmentally and bio-medically important trace molecular species such as nitric oxide, nitrous oxide, carbonyl sulphide and acetylene (C2H2) at ultra-low concentrations by probing numerous rotationally resolved ro-vibrational transitions in the mid-IR spectral region within a relatively small spectral range of ~0.035 cm-1. This continuous wave external-cavity quantum cascade laser-based multi-component CRDS sensor with high sensitivity and molecular specificity promises applications in environmental sensing as well as non-invasive medical diagnosis through human breath analysis.

Solid organ fabrication: comparison of decellularization to 3D bioprinting.

PubMed

Jung, Jangwook P; Bhuiyan, Didarul B; Ogle, Brenda M

2016-01-01

Solid organ fabrication is an ultimate goal of Regenerative Medicine. Since the introduction of Tissue Engineering in 1993, functional biomaterials, stem cells, tunable microenvironments, and high-resolution imaging technologies have significantly advanced efforts to regenerate in vitro culture or tissue platforms. Relatively simple flat or tubular organs are already in (pre)clinical trials and a few commercial products are in market. The road to more complex, high demand, solid organs including heart, kidney and lung will require substantive technical advancement. Here, we consider two emerging technologies for solid organ fabrication. One is decellularization of cadaveric organs followed by repopulation with terminally differentiated or progenitor cells. The other is 3D bioprinting to deposit cell-laden bio-inks to attain complex tissue architecture. We reviewed the development and evolution of the two technologies and evaluated relative strengths needed to produce solid organs, with special emphasis on the heart and other tissues of the cardiovascular system.

Synchronization of electrically coupled micromechanical oscillators with a frequency ratio of 3:1

NASA Astrophysics Data System (ADS)

Pu, Dong; Wei, Xueyong; Xu, Liu; Jiang, Zhuangde; Huan, Ronghua

2018-01-01

In this Letter, synchronization of micromechanical oscillators with a frequency ratio of 3:1 is reported. Two electrically coupled piezoresistive micromechanical oscillators are built for the study, and their oscillation frequencies are tuned via the Joule heating effect to find out the synchronization region. Experimental results show that the larger coupling strength or bias driving voltage is applied and a wider synchronization region is obtained. Interestingly, however, the oscillator's frequency tunability is dramatically reduced from -809.1 Hz/V to -23.1 Hz/V when synchronization is reached. A nearly 10-fold improvement of frequency stability at 1 s is observed from one of the synchronized oscillators, showing a comparable performance of the other. The stable high order synchronization of micromechanical oscillators is helpful to design high performance resonant sensors with a better frequency resolution and a larger scale factor.

Novel solid state lasers for Lidar applications at 2 μm

NASA Astrophysics Data System (ADS)

Della Valle, G.; Galzerano, G.; Toncelli, A.; Tonelli, M.; Laporta, P.

2005-09-01

A review on the results achieved by our group in the development of novel solid-state lasers for Lidar applications at 2 μm is presented. These lasers, based on fluoride crystals (YLF4, BaY2F8, and KYF4) doped with Tm and Ho ions, are characterized by high-efficiency and wide wavelength tunability around 2 μm. Single crystals of LiYF4, BaY2F8, and KYF4 codoped with the same Tm3+ and Ho3+ concentrations were successfully grown by the Czochralski method. The full spectroscopic characterization of the different laser crystals and the comparison between the laser performance are presented. Continuous wave operation was efficiently demonstrated by means of a CW diode-pumping. These oscillators find interesting applications in the field of remote sensing (Lidar and Dial systems) as well as in high-resolution molecular spectroscopy, frequency metrology, and biomedical applications.

A Facile and General Approach to Recoverable High-Strain Multishape Shape Memory Polymers.

PubMed

Li, Xingjian; Pan, Yi; Zheng, Zhaohui; Ding, Xiaobin

2018-03-01

Fabricating a single polymer network with no need to design complex structures to achieve an ideal combination of tunable high-strain multiple-shape memory effects and highly recoverable shape memory property is a great challenge for the real applications of advanced shape memory devices. Here, a facile and general approach to recoverable high-strain multishape shape memory polymers is presented via a random copolymerization of acrylate monomers and a chain-extended multiblock copolymer crosslinker. As-prepared shape memory networks show a large width at the half-peak height of the glass transition, far wider than current classical multishape shape memory polymers. A combination of tunable high-strain multishape memory effect and as high as 1000% recoverable strain in a single chemical-crosslinking network can be obtained. To the best of our knowledge, this is the first thermosetting material with a combination of highly recoverable strain and tunable high-strain multiple-shape memory effects. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

2016-04-04

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.

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

Ultralow-threshold cascaded Brillouin microlaser for tunable microwave generation.

PubMed

Guo, Changlei; Che, Kaijun; Cai, Zhiping; Liu, Shuai; Gu, Guoqiang; Chu, Chengxu; Zhang, Pan; Fu, Hongyan; Luo, Zhengqian; Xu, Huiying

2015-11-01

We experimentally demonstrate an ultralow-threshold cascaded Brillouin microlaser for tunable microwave generation in a high-Q silica microsphere resonator. The threshold of the Brillouin microlaser is as low as 8 μW, which is close to the theoretical prediction. Moreover, the fifth-order Stokes line with a frequency shift up to 55 GHz is achieved with a coupled pump power of less than 0.6 mW. Benefiting from resonant wavelength shifts driven by thermal dynamics in the microsphere, we further realized tunable microwave signals with tuning ranges of 40 MHz at an 11 GHz band and 20 MHz at a 22 GHz band. To the best of our knowledge, it was the first attempt for tunable microwave source based on the whispering-gallery-mode Brillouin microlaser. Such a tunable microwave source from a cascaded Brillouin microlaser could find significant applications in aerospace, communication engineering, and metrology.

Unique dielectric tunability of Pb0.99[(Zr0.6Sn0.4)0.94Ti0.06]0.98Nb0.02O3 antiferroelectric ceramics

NASA Astrophysics Data System (ADS)

Li, Lei; Spreitzer, Matjaž; Suvorov, Danilo; Chen, Xiang Ming

2016-08-01

The tunable dielectric properties of Pb0.99[(Zr0.6Sn0.4)0.94Ti0.06]0.98Nb0.02O3 antiferroelectric ceramics were investigated, and high relative tunability of 49% was obtained at 25 °C under a low bias electric field of 50 kV/cm. Abrupt changes and a significant hysteresis in dielectric constant and dielectric loss against bias electric field were observed, which are very different from the previously reported antiferroelectric materials. The unique dielectric tunability is attributed to the square-shaped double hysteresis loop and indicates the possible applications in some special tunable devices, such as an electrically-controlled switch. Pb0.99[(Zr0.6Sn0.4)0.94Ti0.06]0.98Nb0.02O3 ceramics also exhibit unique dielectric tunability at -5 °C. Abrupt changes in dielectric constant and dielectric loss were observed when the bias electric field increased to 31 kV/cm for the fresh sample, which is similar to the antiferroelectric-like dielectric tunability at 25 °C. However, the dielectric tunability was ferroelectric-like in the following measurement. This response is consistent with the hysteresis loop and can be explained by the electric field-assisted irreversible antiferroelectric-ferroelectric phase transition.

Electro-optically tunable microwave source based on composite-cavity microchip laser.

PubMed

Qiao, Yunfei; Zheng, Shilie; Chi, Hao; Jin, Xiaofeng; Zhang, Xianmin

2012-12-17

A compact and electric tuning microwave source based on a diode-pumped composite Nd:YAG-LiNbO(3) cavity microchip laser is demonstrated. The electro-optical element introduces an electric tuning intra-cavity birefringence which causes a tunable frequency difference between two spilt orthogonal polarization states of a longitude mode. Thus a continuously tunable microwave signal with frequency up to 14.12 GHz can be easily generated by beating the two polarization modes on a high speed photodetector.

The design of a multi-harmonic step-tunable gyrotron

NASA Astrophysics Data System (ADS)

Qi, Xiang-Bo; Du, Chao-Hai; Zhu, Juan-Feng; Pan, Shi; Liu, Pu-Kun

2017-03-01

The theoretical study of a step-tunable gyrotron controlled by successive excitation of multi-harmonic modes is presented in this paper. An axis-encircling electron beam is employed to eliminate the harmonic mode competition. Physics images are depicted to elaborate the multi-harmonic interaction mechanism in determining the operating parameters at which arbitrary harmonic tuning can be realized by magnetic field sweeping to achieve controlled multiband frequencies' radiation. An important principle is revealed that a weak coupling coefficient under a high-harmonic interaction can be compensated by a high Q-factor. To some extent, the complementation between the high Q-factor and weak coupling coefficient makes the high-harmonic mode potential to achieve high efficiency. Based on a previous optimized magnetic cusp gun, the multi-harmonic step-tunable gyrotron is feasible by using harmonic tuning of first-to-fourth harmonic modes. Multimode simulation shows that the multi-harmonic gyrotron can operate on the 34 GHz first-harmonic TE11 mode, 54 GHz second-harmonic TE21 mode, 74 GHz third-harmonic TE31 mode, and 94 GHz fourth-harmonic TE41 mode, corresponding to peak efficiencies of 28.6%, 35.7%, 17.1%, and 11.4%, respectively. The multi-harmonic step-tunable gyrotron provides new possibilities in millimeter-terahertz source development especially for advanced terahertz applications.

Reconstructing Spectral Scenes Using Statistical Estimation to Enhance Space Situational Awareness

DTIC Science & Technology

2006-12-01

simultane- ously spatially and spectrally deblur the images collected from ASIS. The algorithms are based on proven estimation theories and do not...collected with any system using a filtering technology known as Electronic Tunable Filters (ETFs). Previous methods to deblur spectral images collected...spectrally deblurring then the previously investigated methods. This algorithm expands on a method used for increasing the spectral resolution in gamma-ray

Ultralow Energy Electron Attachment at Sub-Millielectron Volt Resolution

NASA Astrophysics Data System (ADS)

Chutjian, Ara

1999-10-01

The technique of rare-gas photoionization(J. M. Ajello and A. Chutjian, J. Chem. Phys. 65), 5524 (1976). has been extended(A. Kortyna, M. Darrach and A. Chutjian, Bull. Am. Phys. Soc. 43), 1336 (1998). by use of direct laser ionization to electron energies ɛ in the range 0-100 meV, with a resolution Δɛ of 0.4-0.5 meV (FWHM). Tunable UV light at λ276 nm is produced using a pulsed Nd:YAG laser and nonlinear mixing techniques. The beam is frequency tripled in a pulsed jet of xenon. The VUV radiation, tunable at λ92 nm, is then used to photoionize Xe at its ^2P_1/2 threshold (single-photon ionization). The photoelectrons produced interact with admixed target gas to generate negative ions through the s-wave capture process. Recent results in electron attachment to SF6 will be reported which show resonance structure at the opening of the ground-state vibrational channels.^3,(H. Hotop et al., AIP Conf. Proc. Ser. 360 (AIP, New York, 1995), and private communication.) This structure corresponds to the process of vibrational excitation + attachment, which is superimposed on the underlying s-wave (direct) capture process. It should be a general phenomenon, present in a wide variety of zero-energy electron attaching molecules.

Broadband and tunable high-performance microwave absorption of an ultralight and highly compressible graphene foam.

PubMed

Zhang, Yi; Huang, Yi; Zhang, Tengfei; Chang, Huicong; Xiao, Peishuang; Chen, Honghui; Huang, Zhiyu; Chen, Yongsheng

2015-03-25

The broadband and tunable high-performance microwave absorption properties of an ultralight and highly compressible graphene foam (GF) are investigated. Simply via physical compression, the microwave absorption performance can be tuned. The qualified bandwidth coverage of 93.8% (60.5 GHz/64.5 GHz) is achieved for the GF under 90% compressive strain (1.0 mm thickness). This mainly because of the 3D conductive network. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Evaluating the sensitivity of an ice sheet model to changes in bed elevation and inclusion of membrane stresses

NASA Astrophysics Data System (ADS)

Aschwanden, Andy; Bueler, Ed; Khroulev, Constantine

2010-05-01

To predict Greenland's contribution to global sea level rise in the next few centuries with some confidence, an accurate representation of its current state is crucial. Simulations of the present state of Greenland using the "Parallel Ice Sheet Model" (PISM) capture the essential flow features but overestimate the current volume by about 30%. Possible sources of error include (1) limited understanding of physical processes involved, (2) the choice of approximations made by the numerical model, (3) values of tunable parameters, and (4) uncertainties in boundary conditions. The response of an ice sheet model to given forcing contains the above mentioned error sources, with unknown weights. In this work we focus on a small subset, namely errors arising from uncertainties in bed elevation and whether or not membrane stresses are included in the stress balance. CReSIS provides recently updated bedrock maps for Greenland include high-resolution data for Jacobshavn Isbræ and Petermann Glacier. We present a four-way comparison between the original BEDMAP, the new CReSIS bedrock data, a non-sliding shallow ice model, and hybrid model which includes the shallow shelf approximation as a sliding law. Large gradients possibly found in high-resolution bedrock elevation are expected to make a hybrid model the more appropriate choice. To elucidate this question, runs are performed on a unprecedented high spatial resolution of 2km for the whole ice sheet. Finally, model predictions are evaluated against observed quantities such as surface velocities, ice thickness, and temperature profiles in bore holes using different metrics.

High resolution interrogation system for fiber Bragg grating (FBG) sensor application using radio frequency spectrum analyser

NASA Astrophysics Data System (ADS)

Muhammad, F. D.; Zulkifli, M. Z.; Harun, S. W.; Ahmad, H.

2013-05-01

In this paper, we propose a fiber Bragg grating (FBG) interrogation system for high resolution sensor application based on radio frequency (RF) generation technique by beating a single longitudinal mode (SLM) fiber ring laser with an external tunable laser source (TLS). The external TLS provides a constant wavelength (CW), functioning as the reference signal for the frequency beating technique. The TLS used has a constant output power and wavelength over time. The sensor signal is provided by the reflected wavelength of a typical fiber Bragg grating (FBG) in the SLM fiber ring laser, which consists of a 1 m long highly doped Erbium doped fiber as the gain medium. The key to ensure the SLM laser oscillation is the role of graphene as saturable absorber which is opposed to the commonly used unpumped erbiumdoped fiber and this consequently contributes to the simple and short cavity design of our proposed system. The signal from the SLM fiber ring laser, which is generated by the FBG in response to external changes, such as temperature, strain, air humidity and air movement, is heterodyned with the CW signal from the TLS at a 6 GHz photodetector using a 3-dB fused coupler to generate the frequency beating. This proposed system is experimentally demonstrated as a temperature sensor and the results shows that the frequency response of the system towards the changes in temperature is about 1.3 GHz/°C, taking into account the resolution bandwidth of 3 MHz of the radio frequency spectrum analyzer (RFSA).

Low-energy ion beamline scattering apparatus for surface science investigations

NASA Astrophysics Data System (ADS)

Gordon, M. J.; Giapis, K. P.

2005-08-01

We report on the design, construction, and performance of a high current (monolayers/s), mass-filtered ion beamline system for surface scattering studies using inert and reactive species at collision energies below 1500 eV. The system combines a high-density inductively coupled plasma ion source, high-voltage floating beam transport line with magnet mass-filter and neutral stripping, decelerator, and broad based detection capabilities (ions and neutrals in both mass and energy) for products leaving the target surface. The entire system was designed from the ground up to be a robust platform to study ion-surface interactions from a more global perspective, i.e., high fluxes (>100μA/cm2) of a single ion species at low, tunable energy (50-1400±5eV full width half maximum) can be delivered to a grounded target under ultrahigh vacuum conditions. The high current at low energy problem is solved using an accel-decel transport scheme where ions are created at the desired collision energy in the plasma source, extracted and accelerated to high transport energy (20 keV to fight space charge repulsion), and then decelerated back down to their original creation potential right before impacting the grounded target. Scattered species and those originating from the surface are directly analyzed in energy and mass using a triply pumped, hybrid detector composed of an electron impact ionizer, hemispherical electrostatic sector, and rf/dc quadrupole in series. With such a system, the collision kinematics, charge exchange, and chemistry occurring on the target surface can be separated by fully analyzing the scattered product flux. Key design aspects of the plasma source, beamline, and detection system are emphasized here to highlight how to work around physical limitations associated with high beam flux at low energy, pumping requirements, beam focusing, and scattered product analysis. Operational details of the beamline are discussed from the perspective of available beam current, mass resolution, projectile energy spread, and energy tunability. As well, performance of the overall system is demonstrated through three proof-of-concept examples: (1) elastic binary collisions at low energy, (2) core-level charge exchange reactions involving Ne+20 with Mg /Al/Si/P targets, and (3) reactive scattering of CF2+/CF3+ off Si. These studies clearly demonstrate why low, tunable incident energy, as well as mass and energy filtering of products leaving the target surface is advantageous and often essential for studies of inelastic energy losses, hard-collision charge exchange, and chemical reactions that occur during ion-surface scattering.

Hyperspectral Image Analysis for Skin Tumor Detection

NASA Astrophysics Data System (ADS)

Kong, Seong G.; Park, Lae-Jeong

This chapter presents hyperspectral imaging of fluorescence for nonin-vasive detection of tumorous tissue on mouse skin. Hyperspectral imaging sensors collect two-dimensional (2D) image data of an object in a number of narrow, adjacent spectral bands. This high-resolution measurement of spectral information reveals a continuous emission spectrum for each image pixel useful for skin tumor detection. The hyperspectral image data used in this study are fluorescence intensities of a mouse sample consisting of 21 spectral bands in the visible spectrum of wavelengths ranging from 440 to 640 nm. Fluorescence signals are measured using a laser excitation source with the center wavelength of 337 nm. An acousto-optic tunable filter is used to capture individual spectral band images at a 10-nm resolution. All spectral band images are spatially registered with the reference band image at 490 nm to obtain exact pixel correspondences by compensating the offsets caused during the image capture procedure. The support vector machines with polynomial kernel functions provide decision boundaries with a maximum separation margin to classify malignant tumor and normal tissue from the observed fluorescence spectral signatures for skin tumor detection.

A novel setup for femtosecond pump-repump-probe IR spectroscopy with few cycle CEP stable pulses.

PubMed

Bradler, Maximilian; Werhahn, Jasper C; Hutzler, Daniel; Fuhrmann, Simon; Heider, Rupert; Riedle, Eberhard; Iglev, Hristo; Kienberger, Reinhard

2013-08-26

We present a three-color mid-IR setup for vibrational pump-repump-probe experiments with a temporal resolution well below 100 fs and a freely selectable spectral resolution of 20 to 360 cm(-1) for the pump and repump. The usable probe range without optical realignment is 900 cm(-1). The experimental design employed is greatly simplified compared to the widely used setups, highly robust and includes a novel means for generation of tunable few-cycle pulses with stable carrier-envelope phase. A Ti:sapphire pump system operating with 1 kHz and a modest 150 fs pulse duration supplies the total pump energy of just 0.6 mJ. The good signal-to-noise ratio of the setup allows the determination of spectrally resolved transient probe changes smaller than 6·10(-5) OD at 130 time delays in just 45 minutes. The performance of the spectrometer is demonstrated with transient IR spectra and decay curves of HDO molecules in lithium nitrate trihydrate and ice and a first all MIR pump-repump-probe measurement.

Wavelength calibration with PMAS at 3.5 m Calar Alto Telescope using a tunable astro-comb

NASA Astrophysics Data System (ADS)

Chavez Boggio, J. M.; Fremberg, T.; Bodenmüller, D.; Sandin, C.; Zajnulina, M.; Kelz, A.; Giannone, D.; Rutowska, M.; Moralejo, B.; Roth, M. M.; Wysmolek, M.; Sayinc, H.

2018-05-01

On-sky tests conducted with an astro-comb using the Potsdam Multi-Aperture Spectrograph (PMAS) at the 3.5 m Calar Alto Telescope are reported. The proposed astro-comb approach is based on cascaded four-wave mixing between two lasers propagating through dispersion optimized nonlinear fibers. This approach allows for a line spacing that can be continuously tuned over a broad range (from tens of GHz to beyond 1 THz) making it suitable for calibration of low- medium- and high-resolution spectrographs. The astro-comb provides 300 calibration lines and his line-spacing is tracked with a wavemeter having 0.3 pm absolute accuracy. First, we assess the accuracy of Neon calibration by measuring the astro-comb lines with (Neon calibrated) PMAS. The results are compared with expected line positions from wavemeter measurement showing an offset of ∼5-20 pm (4%-16% of one resolution element). This might be the footprint of the accuracy limits from actual Neon calibration. Then, the astro-comb performance as a calibrator is assessed through measurements of the Ca triplet from stellar objects HD3765 and HD219538 as well as with the sky line spectrum, showing the advantage of the proposed astro-comb for wavelength calibration at any resolution.

Characterizing Scintillation and Cherenkov Light in Water-Based Liquid Scintillators

NASA Astrophysics Data System (ADS)

Land, Benjamin; Caravaca, Javier; Descamps, Freija; Orebi Gann, Gabriel

2016-09-01

The recent development of Water-based Liquid Scintillator (WbLS) has made it possible to produce scintillating materials with highly tunable light yields and excellent optical clarity. This allows for a straightforward combination of the directional properties of Cherenkov light with the greater energy resolution afforded by the typically brighter scintillation light which lends itself well to a broad program of neutrino physics. Here we explore the light yields and time profiles of WbLS materials in development for Theia (formerly ASDC) as measured in CheSS: our bench-top Cherenkov and scintillation separation R&D project at Berkeley Lab. This work was supported by the Laboratory Directed Research and Development Program of Lawrence Berkeley National Laboratory under U.S. Department of Energy Contract No. DE-AC02-05CH11231.

Acousto-optic infrared spectral imager for Pluto fast flyby

NASA Technical Reports Server (NTRS)

Glenar, D. A.; Hillman, J. J.

1993-01-01

Acousto-optic tunable filters (AOTF's) enable the design of compact, two-dimensional imaging spectrometers with high spectral and spatial resolution and with no moving parts. Tellurium dioxide AOTF's operate from about 400 nm to nearly 5 microns, and a single device will tune continuously over one octave by changing the RF acoustic frequency applied to the device. An infrared (1.2-2.5 micron) Acousto-Optic Imaging Spectrometer (AImS) was designed that closely conforms to the surface composition mapping objectives of the Pluto Fast Flyby. It features a 75-cm focal length telescope, infrared AOTF, and 256 x 256 NICMOS-3 focal plane array for acquiring narrowband images with a spectral resolving power (lambda/delta(lambda)) exceeding 250. We summarize the instrument design features and its expected performance at the Pluto-Charon encounter.

Analysis and design of tunable wideband microwave photonics phase shifter based on Fabry-Perot cavity and Bragg mirrors in silicon-on-insulator waveguide.

PubMed

Qu, Pengfei; Zhou, Jingran; Chen, Weiyou; Li, Fumin; Li, Haibin; Liu, Caixia; Ruan, Shengping; Dong, Wei

2010-04-20

We designed a microwave (MW) photonics phase shifter, consisting of a Fabry-Perot filter, a phase modulation region (PMR), and distributed Bragg reflectors, in a silicon-on-insulator rib waveguide. The thermo-optics effect was employed to tune the PMR. It was theoretically demonstrated that the linear MW phase shift of 0-2pi could be achieved by a refractive index variation of 0-9.68x10(-3) in an ultrawideband (about 38?GHz-1.9?THz), and the corresponding tuning resolution was about 6.92 degrees / degrees C. The device had a very compact size. It could be easily integrated in silicon optoelectronic chips and expected to be widely used in the high-frequency MW photonics field.

Generation of tunable high-repetition rate middle infrared transform-limited picosecond pulses

NASA Astrophysics Data System (ADS)

Yakovlev, Vladislav V.; Ballmann, Charles W.; Petrov, Georgi I.

2018-03-01

Tunable middle infrared generation is now affordable through optical parametric generation and amplification in a number of infrared nonlinear crystals. However, maintaining narrow bandwidth, while achieving high conversion efficiency, remains a challenge. In this report, we propose and experimentally demonstrate a relatively simple setup, which utilizes a single-wavelength diode laser as a seed laser for an optical parametric amplifier.

Tunable plasmon lensing in graphene-based structure exhibiting negative refraction.

PubMed

Zhong, Shifeng; Lu, Yanxin; Li, Chao; Xu, Haixia; Shi, Fenghua; Chen, Yihang

2017-02-02

We propose a novel method to achieve tunable plasmon focusing in graphene/photonic-crystal hybrid structure exhibiting all-angle negative refraction at terahertz frequencies. A two-dimensional photonic crystal composed of a square lattice of dielectric rods is constructed on the substrate of a graphene sheet to provide the hyperbolic dispersion relations of the graphene plasmon, giving rise to the all-angle plasmonic negative refraction. Plasmon lensing induced from the negative refraction is observed. We show that the ultracompact graphene-based system can produce sub-diffraction-limited images with the resolution significant smaller than the wavelength of the incident terahertz wave. Moreover, by adjusting the Fermi energy of the graphene, the imaging performance of the proposed system can remain almost invariant for different frequencies. Our results may find applications in diverse fields such as subwavelength spatial light manipulation, biological imaging, and so forth.

White-Light Supercontinuum Laser-Based Multiple Wavelength Excitation for TCSPC-FLIM of Cutaneous Nanocarrier Uptake

NASA Astrophysics Data System (ADS)

Volz, Pierre; Brodwolf, Robert; Zoschke, Christian; Haag, Rainer; Schäfer-Korting, Monika; Alexiev, Ulrike

2018-05-01

We report here on a custom-built time-correlated single photon-counting (TCSPC)-based fluorescence lifetime imaging microscopy (FLIM) setup with a continuously tunable white-light supercontinuum laser combined with acousto-optical tunable filters (AOTF) as an excitation source for simultaneous excitation of multiple spectrally separated fluorophores. We characterized the wavelength dependence of the white-light supercontinuum laser pulse properties and demonstrated the performance of the FLIM setup, aiming to show the experimental setup in depth together with a biomedical application. We herein summarize the physical-technical parameters as well as our approach to map the skin uptake of nanocarriers using FLIM with a resolution compared to spectroscopy. As an example, we focus on the penetration study of indocarbocyanine-labeled dendritic core-multishell nanocarriers (CMS-ICC) into reconstructed human epidermis. Unique fluorescence lifetime signatures of indocarbocyanine-labeled nanocarriers indicate nanocarrier-tissue interactions within reconstructed human epidermis, bringing FLIM close to spectroscopic analysis.

Tunable plasmon lensing in graphene-based structure exhibiting negative refraction

PubMed Central

Zhong, Shifeng; Lu, Yanxin; Li, Chao; Xu, Haixia; Shi, Fenghua; Chen, Yihang

2017-01-01

We propose a novel method to achieve tunable plasmon focusing in graphene/photonic-crystal hybrid structure exhibiting all-angle negative refraction at terahertz frequencies. A two-dimensional photonic crystal composed of a square lattice of dielectric rods is constructed on the substrate of a graphene sheet to provide the hyperbolic dispersion relations of the graphene plasmon, giving rise to the all-angle plasmonic negative refraction. Plasmon lensing induced from the negative refraction is observed. We show that the ultracompact graphene-based system can produce sub-diffraction-limited images with the resolution significant smaller than the wavelength of the incident terahertz wave. Moreover, by adjusting the Fermi energy of the graphene, the imaging performance of the proposed system can remain almost invariant for different frequencies. Our results may find applications in diverse fields such as subwavelength spatial light manipulation, biological imaging, and so forth. PMID:28150750

Free-space wavelength-multiplexed optical scanner demonstration.

PubMed

Yaqoob, Zahid; Riza, Nabeel A

2002-09-10

Experimental demonstration of a no-moving-parts free-space wavelength-multiplexed optical scanner (W-MOS) is presented. With fast tunable lasers or optical filters and planar wavelength dispersive elements such as diffraction gratings, this microsecond-speed scanner enables large several-centimeter apertures for subdegree angular scans. The proposed W-MOS design incorporates a unique optical amplifier and variable optical attenuator combination that enables the calibration and modulation of the scanner response, leading to any desired scanned laser beam power shaping. The experimental setup uses a tunable laser centered at 1560 nm and a 600-grooves/mm blazed reflection grating to accomplish an angular scan of 12.92 degrees as the source is tuned over an 80-nm bandwidth. The values for calculated maximum optical beam divergance, required wavelength resolution, beam-pointing accuracy, and measured scanner insertion loss are 1.076 mrad, 0.172 nm, 0.06 mrad, and 4.88 dB, respectively.

Design of tunable thermo-optic C-band filter based on coated silicon slab

NASA Astrophysics Data System (ADS)

Pinhas, Hadar; Malka, Dror; Danan, Yossef; Sinvani, Moshe; Zalevsky, Zeev

2018-03-01

Optical filters are required to have narrow band-pass filtering in the spectral C-band for applications such as signal tracking, sub-band filtering or noise suppression. These requirements lead to a variety of filters such as Mach-Zehnder interferometer inter-leaver in silica, which offer thermo-optic effect for optical switching, however, without proper thermal and optical efficiency. In this paper we propose tunable thermo-optic filtering device based on coated silicon slab resonator with increased Q-factor for the C-band optical switching. The device can be designed either for long range wavelength tuning of for short range with increased wavelength resolution. Theoretical examination of the thermal parameters affecting the filtering process is shown together with experimental results. Proper channel isolation with an extinction ratio of 20dBs is achieved with spectral bandpass width of 0.07nm.

MEMS tunable grating micro-spectrometer

NASA Astrophysics Data System (ADS)

Tormen, Maurizio; Lockhart, R.; Niedermann, P.; Overstolz, T.; Hoogerwerf, A.; Mayor, J.-M.; Pierer, J.; Bosshard, C.; Ischer, R.; Voirin, G.; Stanley, R. P.

2017-11-01

The interest in MEMS based Micro-Spectrometers is increasing due to their potential in terms of flexibility as well as cost, low mass, small volume and power savings. This interest, especially in the Near-Infrared and Mid- Infrared, ranges from planetary exploration missions to astronomy, e.g. the search for extra solar planets, as well as to many other terrestrial fields of application such as, industrial quality and surface control, chemical analysis of soil and water, detection of chemical pollutants, exhausted gas analysis, food quality control, process control in pharmaceuticals, to name a few. A compact MEMS-based Spectrometer for Near- Infrared and Mid-InfraRed operation have been conceived, designed and demonstrated. The design based on tunable MEMS blazed grating, developed in the past at CSEM [1], achieves state of the art results in terms of spectral resolution, operational wavelength range, light throughput, overall dimensions, and power consumption.

Photonic crystal nanocavity assisted rejection ratio tunable notch microwave photonic filter

PubMed Central

Long, Yun; Xia, Jinsong; Zhang, Yong; Dong, Jianji; Wang, Jian

2017-01-01

Driven by the increasing demand on handing microwave signals with compact device, low power consumption, high efficiency and high reliability, it is highly desired to generate, distribute, and process microwave signals using photonic integrated circuits. Silicon photonics offers a promising platform facilitating ultracompact microwave photonic signal processing assisted by silicon nanophotonic devices. In this paper, we propose, theoretically analyze and experimentally demonstrate a simple scheme to realize ultracompact rejection ratio tunable notch microwave photonic filter (MPF) based on a silicon photonic crystal (PhC) nanocavity with fixed extinction ratio. Using a conventional modulation scheme with only a single phase modulator (PM), the rejection ratio of the presented MPF can be tuned from about 10 dB to beyond 60 dB. Moreover, the central frequency tunable operation in the high rejection ratio region is also demonstrated in the experiment. PMID:28067332

Photonic crystal nanocavity assisted rejection ratio tunable notch microwave photonic filter

NASA Astrophysics Data System (ADS)

Long, Yun; Xia, Jinsong; Zhang, Yong; Dong, Jianji; Wang, Jian

2017-01-01

Driven by the increasing demand on handing microwave signals with compact device, low power consumption, high efficiency and high reliability, it is highly desired to generate, distribute, and process microwave signals using photonic integrated circuits. Silicon photonics offers a promising platform facilitating ultracompact microwave photonic signal processing assisted by silicon nanophotonic devices. In this paper, we propose, theoretically analyze and experimentally demonstrate a simple scheme to realize ultracompact rejection ratio tunable notch microwave photonic filter (MPF) based on a silicon photonic crystal (PhC) nanocavity with fixed extinction ratio. Using a conventional modulation scheme with only a single phase modulator (PM), the rejection ratio of the presented MPF can be tuned from about 10 dB to beyond 60 dB. Moreover, the central frequency tunable operation in the high rejection ratio region is also demonstrated in the experiment.

Photonic crystal nanocavity assisted rejection ratio tunable notch microwave photonic filter.

PubMed

Long, Yun; Xia, Jinsong; Zhang, Yong; Dong, Jianji; Wang, Jian

2017-01-09

Driven by the increasing demand on handing microwave signals with compact device, low power consumption, high efficiency and high reliability, it is highly desired to generate, distribute, and process microwave signals using photonic integrated circuits. Silicon photonics offers a promising platform facilitating ultracompact microwave photonic signal processing assisted by silicon nanophotonic devices. In this paper, we propose, theoretically analyze and experimentally demonstrate a simple scheme to realize ultracompact rejection ratio tunable notch microwave photonic filter (MPF) based on a silicon photonic crystal (PhC) nanocavity with fixed extinction ratio. Using a conventional modulation scheme with only a single phase modulator (PM), the rejection ratio of the presented MPF can be tuned from about 10 dB to beyond 60 dB. Moreover, the central frequency tunable operation in the high rejection ratio region is also demonstrated in the experiment.

A high speed, portable, multi-function, weigh-in-motion (WIM) sensing system and a high performance optical fiber Bragg grating (FBG) demodulator

NASA Astrophysics Data System (ADS)

Zhang, Hongtao; Wei, Zhanxiong; Fan, Lingling; Yang, Shangming; Wang, Pengfei; Cui, Hong-Liang

2010-04-01

A high speed, portable, multi-function WIM sensing system based on Fiber Bragg Grating (FBG) technology is reported in this paper. This system is developed to measure the total weight, the distribution of weight of vehicle in motion, the distance of wheel axles and the distance between left and right wheels. In this system, a temperature control system and a real-time compensation system are employed to eliminate the drifts of optical fiber Fabry-Pérot tunable filter. Carbon Fiber Laminated Composites are used in the sensor heads to obtain high reliability and sensitivity. The speed of tested vehicles is up to 20 mph, the full scope of measurement is 4000 lbs, and the static resolution of sensor head is 20 lbs. The demodulator has high speed (500 Hz) data collection, and high stability. The demodulator and the light source are packed into a 17'' rack style enclosure. The prototype has been tested respectively at Stevens' campus and Army base. Some experiences of avoiding the pitfalls in developing this system are also presented in this paper.

High-resolution digital movies of emerging flux and horizontal flows in active regions on the sun

NASA Astrophysics Data System (ADS)

Topka, K.; Ferguson, S.; Frank, Z.; Tarbell, T.; Title, A.

1988-11-01

High-resolution observations of active regions in many wavelength bands obtained at the Vacuum Tower Telescope of NSO/Sunspot (Sacramento Peak) are presented. The SOUP tunable filter, HRSO 1024 x 1024 CCD camera, and a sunspot tracker for image stabilization were used. Subarrays of 512 x 512 pixels were processed digitally and recorded on videodisk in movie format. The movies with 0.5 to 1 arcsecond resolution of the following simultaneous observations were shown: green continuum, longitudinal magnetogram, Doppler velocity, Fe I 5576 A line center, H alpha wings, and H alpha line center. The best set of movies show a 90 x 90 arcsecond field-of-view of an active region at S29, W11. When viewed at speeds of a few thousand times real-time, the photospheric movies clearly show the active region fields being distorted by a remarkable combination of systematic flows and small eruptions of new flux. Flux emergence is most easily discovered in line center movies: an elongated dark feature appears first, followed soon after by bright points at one or both ends. A brief, strong upflow is seen when the dark feature first appears; downflow in the bright points persists much longer. The magnetic flux appears to increase gradually over this extended period. Some of the flux emergence events were studied in detail, with measurements of horizontal and vertical velocities and magnetic flux versus time within one footpoint of the loop.

High-resolution digital movies of emerging flux and horizontal flows in active regions on the sun

NASA Technical Reports Server (NTRS)

Topka, K.; Ferguson, S.; Frank, Z.; Tarbell, T.; Title, A.

1988-01-01

High-resolution observations of active regions in many wavelength bands obtained at the Vacuum Tower Telescope of NSO/Sunspot (Sacramento Peak) are presented. The SOUP tunable filter, HRSO 1024 x 1024 CCD camera, and a sunspot tracker for image stabilization were used. Subarrays of 512 x 512 pixels were processed digitally and recorded on videodisk in movie format. The movies with 0.5 to 1 arcsecond resolution of the following simultaneous observations were shown: green continuum, longitudinal magnetogram, Doppler velocity, Fe I 5576 A line center, H alpha wings, and H alpha line center. The best set of movies show a 90 x 90 arcsecond field-of-view of an active region at S29, W11. When viewed at speeds of a few thousand times real-time, the photospheric movies clearly show the active region fields being distorted by a remarkable combination of systematic flows and small eruptions of new flux. Flux emergence is most easily discovered in line center movies: an elongated dark feature appears first, followed soon after by bright points at one or both ends. A brief, strong upflow is seen when the dark feature first appears; downflow in the bright points persists much longer. The magnetic flux appears to increase gradually over this extended period. Some of the flux emergence events were studied in detail, with measurements of horizontal and vertical velocities and magnetic flux versus time within one footpoint of the loop.

A spectrally tunable all-graphene-based flexible field-effect light-emitting device

PubMed Central

Wang, Xiaomu; Tian, He; Mohammad, Mohammad Ali; Li, Cheng; Wu, Can; Yang, Yi; Ren, Tian-Ling

2015-01-01

The continuous tuning of the emission spectrum of a single light-emitting diode (LED) by an external electrical bias is of great technological significance as a crucial property in high-quality displays, yet this capability has not been demonstrated in existing LEDs. Graphene, a tunable optical platform, is a promising medium to achieve this goal. Here we demonstrate a bright spectrally tunable electroluminescence from blue (∼450 nm) to red (∼750 nm) at the graphene oxide/reduced-graphene oxide interface. We explain the electroluminescence results from the recombination of Poole–Frenkel emission ionized electrons at the localized energy levels arising from semi-reduced graphene oxide, and holes from the top of the π band. Tuning of the emission wavelength is achieved by gate modulation of the participating localized energy levels. Our demonstration of current-driven tunable LEDs not only represents a method for emission wavelength tuning but also may find applications in high-quality displays. PMID:26178323

Thermo-optic devices on polymer platform

NASA Astrophysics Data System (ADS)

Zhang, Ziyang; Keil, Norbert

2016-03-01

Optical polymers possess in general relatively high thermo-optic coefficients and at the same time low thermal conductivity, both of which make them attractive material candidates for realizing highly efficient thermally tunable devices. Over the years, various thermo-optic components have been demonstrated on polymer platform, covering (1) tunable reflectors and filters as part of a laser cavity, (2) variable optical attenuators (VOAs) as light amplitude regulators in e.g. a coherent receiver, and (3) thermo-optic switches (TOSs) allowing multi-flow control in the photonic integrated circuits (PICs). This work attempts to review the recent progress on the above mentioned three component branches, including linearly and differentially tunable filters, VOAs based on 1×1 multimode interference structure (MMI) and Mach-Zehnder interferometer (MZI), and 1×2 TOS based on waveguide Y-branch, driven by a pair of sidelong placed heater electrodes. These thermo-optic components can well be integrated into larger PICs: the dual-polarization switchable tunable laser and the colorless optical 90° hybrid are presented in the end as examples.

Sub-kilohertz excitation lasers for quantum information processing with Rydberg atoms

NASA Astrophysics Data System (ADS)

Legaie, Remy; Picken, Craig J.; Pritchard, Jonathan D.

2018-04-01

Quantum information processing using atomic qubits requires narrow linewidth lasers with long-term stability for high fidelity coherent manipulation of Rydberg states. In this paper, we report on the construction and characterization of three continuous-wave (CW) narrow linewidth lasers stabilized simultaneously to an ultra-high finesse Fabry-Perot cavity made of ultra-low expansion (ULE) glass, with a tunable offset-lock frequency. One laser operates at 852~nm while the two locked lasers at 1018~nm are frequency doubled to 509~nm for excitation of $^{133}$Cs atoms to Rydberg states. The optical beatnote at 509~nm is measured to be 260(5)~Hz. We present measurements of the offset between the atomic and cavity resonant frequencies using electromagnetically induced transparency (EIT) for high-resolution spectroscopy on a cold atom cloud. The long-term stability is determined from repeated spectra over a period of 20 days yielding a linear frequency drift of $\\sim1$~Hz/s.

Three-Dimensional Printing of Bisphenol A-Free Polycarbonates.

PubMed

Zhu, Wei; Pyo, Sang-Hyun; Wang, Pengrui; You, Shangting; Yu, Claire; Alido, Jeffrey; Liu, Justin; Leong, Yew; Chen, Shaochen

2018-02-14

Polycarbonates are widely used in food packages, drink bottles, and various healthcare products such as dental sealants and tooth coatings. However, bisphenol A (BPA) and phosgene used in the production of commercial polycarbonates pose major concerns to public health safety. Here, we report a green pathway to prepare BPA-free polycarbonates (BFPs) by thermal ring-opening polymerization and photopolymerization. Polycarbonates prepared from two cyclic carbonates in different mole ratios demonstrated tunable mechanical stiffness, excellent thermal stability, and high optical transparency. Three-dimensional (3D) printing of the new BFPs was demonstrated using a two-photon laser direct writing system and a rapid 3D optical projection printer to produce structures possessing complex high-resolution geometries. Seeded C3H10T1/2 cells also showed over 95% viability with potential applications in biological studies. By combining biocompatible BFPs with 3D printing, novel safe and high-performance biomedical devices and healthcare products could be developed with broad long-term benefits to society.

Tunable features of magnetoelectric transformers.

PubMed

Dong, Shuxiang; Zhai, Junyi; Priya, Shashank; Li, Jie-Fang; Viehland, Dwight

2009-06-01

We have found that magnetostrictive FeBSiC alloy ribbons laminated with piezoelectric Pb(Zr,Ti)O(3) fiber can act as a tunable transformer when driven under resonant conditions. These composites were also found to exhibit the strongest resonant magnetoelectric voltage coefficient of 750 V/cm-Oe. The tunable features were achieved by applying small dc magnetic biases of -5

Geometrically tunable Fabry-Perot filters based on reflection phase shift of high contrast gratings

NASA Astrophysics Data System (ADS)

Fang, Liang; Shi, Zhendong; Cheng, Xin; Peng, Xiang; Zhang, Hui

2016-03-01

We propose tunable Fabry-Perot filters constituted by double high contrast gratings (HCGs) arrays with different periods acting as reflectors separated by a fixed short cavity, based on high reflectivity and the variety reflection phase shift of HCG array which realize dynamic regulation of the filtering condition. Single optimized HCG obtains the reflectivity of higher than 99% in a grating period ranging from 0.68μm to 0.8μm across a bandwidth of 30nm near the 1.55μm wavelength. The filters can achieve the full width at half maximum (FWHM) of spectral line of less than 0.15nm, and the linear relationship of peak wavelengths and grating periods is established. The simulation results indicate a potential new approach to design a tunable narrowband transmission filter.

Development and Evaluation of a High Sensitivity DIAL System for Profiling Atmospheric CO2

NASA Technical Reports Server (NTRS)

Ismail, Syed; Koch, Grady J.; Refaat, Tamer F.; Abedin, M. N.; Yu, Jirong; Singh, Upendra N.

2008-01-01

A ground-based 2-micron Differential Absorption Lidar (DIAL) CO2 profiling system for atmospheric boundary layer studies and validation of space-based CO2 sensors is being developed and tested at NASA Langley Research Center as part of the NASA Instrument Incubator Program. To capture the variability of CO2 in the lower troposphere a precision of 1-2 ppm of CO2 (less than 0.5%) with 0.5 to 1 km vertical resolution from near surface to free troposphere (4-5 km) is one of the goals of this program. In addition, a 1% (3 ppm) absolute accuracy with a 1 km resolution over 0.5 km to free troposphere (4-5 km) is also a goal of the program. This DIAL system leverages 2-micron laser technology developed under NASA's Laser Risk Reduction Program (LRRP) and other NASA programs to develop new solid-state laser technology that provides high pulse energy, tunable, wavelength-stabilized, and double-pulsed lasers that are operable over pre-selected temperature insensitive strong CO2 absorption lines suitable for profiling of lower tropospheric CO2. It also incorporates new high quantum efficiency, high gain, and relatively low noise phototransistors, and a new receiver/signal processor system to achieve high precision DIAL measurements. This presentation describes the capabilities of this system for atmospheric CO2 and aerosol profiling. Examples of atmospheric measurements in the lidar and DIAL mode will be presented.

Absorption sensor for CO in combustion gases using 2.3 µm tunable diode lasers

NASA Astrophysics Data System (ADS)

Chao, X.; Jeffries, J. B.; Hanson, R. K.

2009-11-01

Tunable diode laser absorption spectroscopy of CO was studied in the controlled laboratory environments of a heated cell and a combustion exhaust rig. Two absorption lines, R(10) and R(11) in the first overtone band of CO near 2.3 µm, were selected from a HITRAN simulation to minimize interference from water vapor at a representative combustion exhaust temperature (~1200 K). The linestrengths and collision broadening coefficients for these lines were measured in a heated static cell. This database was then used in a comparative study of direct absorption and wavelength-modulation absorption. CO concentration measurements using scanned-wavelength direct absorption (DA) and wavelength modulation with the second-harmonic signal normalized by the first-harmonic signal (WMS-2f/1f) all agreed with those measured by a conventional gas sampling analyzer over the range from <10 ppm to 2.3%. As expected, water vapor was found to be the dominant source of background interference for CO detection in combustion flows at high temperatures. Water absorption was measured to a high spectral resolution within the wavelength region 4295-4301 cm-1 at 1100 K, and shown to produce <10 ppm level interference for CO detection in combustion exhausts at temperatures up to 1200 K. We found that the WMS-2f/1f strategy avoids the need for WMS calibration measurements but requires characterization of the wavelength and injection-current intensity modulation of the specific diode laser. We conclude that WMS-2f/1f using the selected R(10) or R(11) transitions in the CO overtone band holds good promise for sensitive in situ detection of ppm-level CO in combustion flows, with high resistance to interference absorption from H2O.

Tunable optical coherence tomography in the infrared range using visible photons

NASA Astrophysics Data System (ADS)

Paterova, Anna V.; Yang, Hongzhi; An, Chengwu; Kalashnikov, Dmitry A.; Krivitsky, Leonid A.

2018-04-01

Optical coherence tomography (OCT) is an appealing technique for bio-imaging, medicine, and material analysis. For many applications, OCT in mid- and far-infrared (IR) leads to significantly more accurate results. Reported mid-IR OCT systems require light sources and photodetectors which operate in mid-IR range. These devices are expensive and need cryogenic cooling. Here, we report a proof-of-concept demonstration of a wavelength tunable IR OCT technique with detection of only visible range photons. Our method is based on the nonlinear interference of frequency correlated photon pairs. The nonlinear crystal, introduced in the Michelson-type interferometer, generates photon pairs with one photon in the visible and another in the IR range. The intensity of detected visible photons depends on the phase and loss of IR photons, which interact with the sample under study. This enables us to characterize sample properties and perform imaging in the IR range by detecting visible photons. The technique possesses broad wavelength tunability and yields a fair axial and lateral resolution, which can be tailored to the specific application. The work contributes to the development of versatile 3D imaging and material characterization systems working in a broad range of IR wavelengths, which do not require the use of IR-range light sources and photodetectors.

Controlling electronic couplings with tunable long wavelength pulses: Study of Autler-Townes splitting and XUV emission spectra

NASA Astrophysics Data System (ADS)

Harkema, Nathan; Liao, Chen-Ting; Sandhu, Arvinder

2017-04-01

Attosecond transient absorption spectroscopy (ATAS) enables the study of excited electron dynamics with unprecedented temporal and energy resolution. Many ATAS experiments use an extreme ultraviolet (XUV) pump pulse and a near-infrared (NIR) probe fixed at the fundamental laser frequency ( 800 nm) to study the light induced effects on electronic structure of atoms and molecules. We extend the technique by using an optical parametric amplifier in one arm of our setup, which allows us to independently tune the frequency of the probe pulse from 1200 to 1800 nm. These long-wavelength pulses allow us to explore a new regime, where we can control the couplings between nearby electronic states to alter the transient absorption lineshapes in atoms. We use this technique to investigate the 4p-3s detuning dependent Autler-Townes splitting of the 4p state in Helium. Light induced Floquet structures extending into the continuum are observed in our study. We demonstrate new tunable XUV emission channels from four-wave mixing processes, and the efficiency of these emissions can be strongly enhanced through resonant couplings. The tunable IR induced electronic couplings are also used to influence the autoionization dynamics in Argon. This work is supported by NSF Grant No. PHY-1505556 and ARO Grant No. W911NF-14-1-0383.

Tunable Fabry-Perot etalon-based long-wavelength infrared imaging spectroradiometer.

PubMed

Marinelli, W J; Gittins, C M; Gelb, A H; Green, B D

1999-04-20

Imaging spectrometry enables passive, stand-off detection and analysis of the chemical composition of gas plumes and surfaces over wide geographic areas. We describe the use of a long-wavelength infrared imaging spectroradiometer, comprised of a low-order tunable Fabry-Perot etalon coupled to a HgCdTe detector array, to perform multispectral detection of chemical vapor plumes. The tunable Fabry-Perot etalon used in this research provides coverage of the 9.5-14-microm spectral region with a resolution of 7-9 cm(-1). The etalon-based imaging system provides the opportunity to image a scene at only those wavelengths needed for chemical species identification and quantification and thereby minimize the data volume necessary for selective species detection. We present initial results using a brassboard imaging system for stand-off detection and quantification of chemical vapor plumes against near-ambient-temperature backgrounds. These data show detection limits of 22 parts per million by volume times meter (ppmv x m) and 0.6 ppmv x m for dimethyl methyphosphonate and SF6, respectively, for a gas/background DeltaT of 6 K. The system noise-equivalent spectral radiance is approximately 2 microW cm(-2) sr(-1) microm(-1). Model calculations are presented comparing the measured sensitivity of the sensor to the anticipated signal levels for two chemical release scenarios.

Fiber Bragg grating interrogation using a wavelength modulated 1651-nm tunable distributed feedback laser and a fiber ring resonator for wearable biomedical sensors

NASA Astrophysics Data System (ADS)

Roy, Anirban; Chakraborty, Arup Lal; Jha, Chandan Kumar

2017-04-01

This paper demonstrates the interrogation of a fiber Bragg grating with a flat-topped reflection spectrum centred on 1649.55 nm using only a single mode tunable 1651.93 nm semiconductor laser and a fiber ring resonator. The Bragg shift is accurately measured with the fiber-optic ring resonator that has a free spectral range (FSR) of 0.1008 GHz and a broadband photo-detector. Laser wavelength modulation and harmonic detection are used to transform the gentle edges of the flat-topped FBG spectrum into prominent leading and trailing peaks, either of which can be used to accurately measure spectral shifts of the FBG reflection spectrum with a resolution of 0.9 pm. A Raspberry Pi-based low-cost embedded processor is used to measure the temperature-induced spectral shifts over the range 30˚C - 80˚C. The shift was linear with a temperature sensitivity of 12.8 pm/˚C. This technique does not use an optical spectrum analyzer at any stage of its design or operation. The laser does not need to be pre-characterized either. This technique can be readily extended to all types of tunable diode lasers and is ideally suited for compact field instruments.

3D structured illumination microscopy using an incoherent illumination system based on a Fresnel biprism

NASA Astrophysics Data System (ADS)

Shabani, H.; Doblas, A.; Saavedra, G.; Preza, C.

2018-02-01

Three-dimensional (3D) structured illumination (SI) patterns that include lateral and axial variations have attracted more attention recently as their use in fluorescence microscope enhances the 3D resolution of the native imaging system. 3D SI patterns have already been created by interfering three mutually-coherent waves using a diffraction grating or some electro-optical devices such as spatial light modulators. Here, an interesting approach to generate a 3D SI pattern of tunable modulation frequency is shown. Our proposed illumination system is based on the incoherent illumination of a Fresnel biprism using several equidistant linear sources (i.e., slits). Previously, we investigated and compared numerically this tunable SI microscopy (SIM) system with the one achieved with three-wave interference. In this contribution, we implement our proposed incoherent 3D SIM system of tunable-frequency in an open-setup. We evaluate the axial confinement of the illumination pattern obtained with this system by recording the SI pattern using a mirror sample and different number of slits and compare these data with simulation results. Moreover, we verify that with a higher number of slits used, the axial confinement of the pattern increases, and consequently, the system's optical sectioning capability improves.

Supernova feedback in numerical simulations of galaxy formation: separating physics from numerics

NASA Astrophysics Data System (ADS)

Smith, Matthew C.; Sijacki, Debora; Shen, Sijing

2018-07-01

While feedback from massive stars exploding as supernovae (SNe) is thought to be one of the key ingredients regulating galaxy formation, theoretically it is still unclear how the available energy couples to the interstellar medium and how galactic scale outflows are launched. We present a novel implementation of six sub-grid SN feedback schemes in the moving-mesh code AREPO, including injections of thermal and/or kinetic energy, two parametrizations of delayed cooling feedback and a `mechanical' feedback scheme that injects the correct amount of momentum depending on the relevant scale of the SN remnant resolved. All schemes make use of individually time-resolved SN events. Adopting isolated disc galaxy set-ups at different resolutions, with the highest resolution runs reasonably resolving the Sedov-Taylor phase of the SN, we aim to find a physically motivated scheme with as few tunable parameters as possible. As expected, simple injections of energy overcool at all but the highest resolution. Our delayed cooling schemes result in overstrong feedback, destroying the disc. The mechanical feedback scheme is efficient at suppressing star formation, agrees well with the Kennicutt-Schmidt relation, and leads to converged star formation rates and galaxy morphologies with increasing resolution without fine-tuning any parameters. However, we find it difficult to produce outflows with high enough mass loading factors at all but the highest resolution, indicating either that we have oversimplified the evolution of unresolved SN remnants, require other stellar feedback processes to be included, and require a better star formation prescription or most likely some combination of these issues.

Supernova feedback in numerical simulations of galaxy formation: separating physics from numerics

NASA Astrophysics Data System (ADS)

Smith, Matthew C.; Sijacki, Debora; Shen, Sijing

2018-04-01

While feedback from massive stars exploding as supernovae (SNe) is thought to be one of the key ingredients regulating galaxy formation, theoretically it is still unclear how the available energy couples to the interstellar medium and how galactic scale outflows are launched. We present a novel implementation of six sub-grid SN feedback schemes in the moving-mesh code AREPO, including injections of thermal and/or kinetic energy, two parametrizations of delayed cooling feedback and a `mechanical' feedback scheme that injects the correct amount of momentum depending on the relevant scale of the SN remnant resolved. All schemes make use of individually time-resolved SN events. Adopting isolated disk galaxy setups at different resolutions, with the highest resolution runs reasonably resolving the Sedov-Taylor phase of the SN, we aim to find a physically motivated scheme with as few tunable parameters as possible. As expected, simple injections of energy overcool at all but the highest resolution. Our delayed cooling schemes result in overstrong feedback, destroying the disk. The mechanical feedback scheme is efficient at suppressing star formation, agrees well with the Kennicutt-Schmidt relation and leads to converged star formation rates and galaxy morphologies with increasing resolution without fine tuning any parameters. However, we find it difficult to produce outflows with high enough mass loading factors at all but the highest resolution, indicating either that we have oversimplified the evolution of unresolved SN remnants, require other stellar feedback processes to be included, require a better star formation prescription or most likely some combination of these issues.

A tunable emerald laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shand, M.L.; Walling, J.C.

1982-11-01

Emerald is a new broadly wavelength-tunable vibronic laser material with stimulated emission in the red to infrared due to /sup 4/T/sub 2/..-->../sup 4/A transitions of Cr/sup 3 +/. Emerald has gain from 12 050 cm/sup -1/ to 14 000 cm/sup -1/ with high gain from about 12 300 cm/sup -1/ to 13 700 cm/sup -1/. An emerald laser oscillator has been achieved, but has high losses.

Multiphoton autofluorescence lifetime imaging of induced pluripotent stem cells

NASA Astrophysics Data System (ADS)

Uchugonova, Aisada

2017-06-01

The multiphoton fluorescence lifetime imaging tomograph MPTflex with its flexible 360-deg scan head, articulated arm, and tunable femtosecond laser source was employed to study induced pluripotent stem cell (iPS) cultures. Autofluorescence (AF) lifetime imaging was performed with 250-ps temporal resolution and submicron spatial resolution using time-correlated single-photon counting. The two-photon excited AF was based on the metabolic coenzymes NAD(P)H and flavin adenine dinucleotide/flavoproteins. iPS cells generated from mouse embryonic fibroblasts (MEFs) and cocultured with growth-arrested MEFs as feeder cells have been studied. Significant differences on AF lifetime signatures were identified between iPS and feeder cells as well as between their differentiating counterparts.

FIFI: The MPE Garching/UC Berkeley Far-Infrared Imaging Fabry-Perot Interferometer

NASA Technical Reports Server (NTRS)

Geis, Norbert; Genzel, Reinhard; Haggerty, M.; Herrmann, F.; Jackson, J.; Madden, Suzanne C.; Nikola, T.; Poglitsch, Albrecht; Rumitz, M.; Stacey, G. J.

1995-01-01

We describe the performance characteristics of the MPE Garching/UC Berkeley Far-Infrared Imaging Fabry-Perot Interferometer (FIFI) for the Kuiper Airborne Observatory (KAO). The spectrometer features two or three cryogenic tunable Fabry-Perot filters in series giving spectral resolution R of up to 10(exp 5) in the range of 40 microns less than lambda less than 200 microns, and an imaging 5x5 array of photoconductive detectors with variable focal plane plate scale. The instrument works at background limited sensitivity of up to 2 x 10(exp -19) W cm(exp -2) Hz(exp -1/2) per pixel per resolution element at R = 10(exp 5) on the KAO.

Exploiting dimensionality and defect mitigation to create tunable microwave dielectrics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Che-Hui; Orloff, Nathan; Birol, Turan

2013-01-01

The miniaturization and integration of frequency-agile microwave circuits tunable filters, resonators, phase shifters and more with microelectronics offers tantalizing device possibilities, yet requires thin films whose dielectric constant at GHz frequencies can be tuned by applying a quasi-static electric field . Appropriate systems, e.g., BaxSr1 xTiO3, have a paraelectric-to-ferroelectric transition just below ambient temperature, providing high tunability1 . Unfortunately such films suffer significant losses arising from defects. Recognizing that progress is stymied by dielectric loss, we start with a system with exceptionally low loss Srn+1TinO3n+1 phases , where (SrO)2 crystallographic shear , planes provide an alternative to point defect formationmore » for accommodating non-stoichiometry , . Here, we report the experimental realization of a highly tunable ground state arising from the emergence of a local ferroelectric instability in biaxially strained Srn+1TinO3n+1 phases with n 3 at frequencies up to 120 GHz. In contrast to traditional methods of modifying ferroelectrics doping or strain in this rather unique system increasing the separation between the (SrO)2 planes bolsters the local ferroelectric instability. This new control parameter, n, can be exploited to achieve a figure of merit at room temperature that rivals all known tunable microwave dielectrics.« less

High power, widely tunable, mode-hop free, continuous wave external cavity quantum cascade laser for multi-species trace gas detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Centeno, R.; Marchenko, D.; Mandon, J.

We present a high power, widely tunable, continuous wave external cavity quantum cascade laser designed for infrared vibrational spectroscopy of molecules exhibiting broadband and single line absorption features. The laser source exhibits single mode operation with a tunability up to 303 cm{sup −1} (∼24% of the center wavelength) at 8 μm, with a maximum optical output power of 200 mW. In combination with off-axis integrated output spectroscopy, trace-gas detection of broadband absorption gases such as acetone was performed and a noise equivalent absorption sensitivity of 3.7 × 10{sup −8 }cm{sup −1 }Hz{sup −1/2} was obtained.

Electric field-tunable Ba{sub x}Sr{sub 1-x}TiO{sub 3} films with high figures of merit grown by molecular beam epitaxy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mikheev, Evgeny; Kajdos, Adam P.; Hauser, Adam J.

2012-12-17

We report on the dielectric properties of Ba{sub x}Sr{sub 1-x}TiO{sub 3} (BST) films grown by molecular beam epitaxy on epitaxial Pt bottom electrodes. Paraelectric films (x Less-Than-Or-Equivalent-To 0.5) exhibit dielectric losses that are similar to those of BST single crystals and ceramics. Films with device quality factors greater than 1000 and electric field tunabilities exceeding 1:5 are demonstrated. The results provide evidence for the importance of stoichiometry control and the use of a non-energetic deposition technique for achieving high figures of merit of tunable devices with BST thin films.

Spectrally tunable, temporally shaped parametric front end to seed high-energy Nd:glass laser systems

DOE PAGES

Dorrer, C.; Consentino, A.; Cuffney, R.; ...

2017-10-18

Here, we describe a parametric-amplification–based front end for seeding high-energy Nd:glass laser systems. The front end delivers up to 200 mJ by parametric amplification in 2.5-ns flat-in-time pulses tunable over more than 15 nm. Spectral tunability over a range larger than what is typically achieved by laser media at similar energy levels is implemented to investigate cross-beam energy transfer in multibeam target experiments. The front-end operation is simulated to explain the amplified signal’s sensitivity to the input pump and signal. A large variety of amplified waveforms are generated by closed-loop pulse shaping. Various properties and limitations of this front endmore » are discussed.« less

Spectrally tunable, temporally shaped parametric front end to seed high-energy Nd:glass laser systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dorrer, C.; Consentino, A.; Cuffney, R.

Here, we describe a parametric-amplification–based front end for seeding high-energy Nd:glass laser systems. The front end delivers up to 200 mJ by parametric amplification in 2.5-ns flat-in-time pulses tunable over more than 15 nm. Spectral tunability over a range larger than what is typically achieved by laser media at similar energy levels is implemented to investigate cross-beam energy transfer in multibeam target experiments. The front-end operation is simulated to explain the amplified signal’s sensitivity to the input pump and signal. A large variety of amplified waveforms are generated by closed-loop pulse shaping. Various properties and limitations of this front endmore » are discussed.« less

Design and measuring of a tunable hybrid metamaterial absorber for terahertz frequencies

NASA Astrophysics Data System (ADS)

Zhong, Min; Liu, Shui Jie; Xu, Bang Li; Wang, Jie; Huang, Hua Qing

2018-04-01

A tunable hybrid metamaterial absorber is designed and experimentally produced in THz band. The hybrid metamaterial absorber contains two dielectric layers: SU-8 and VO2 layers. An absorption peak reaching to 83.5% is achieved at 1.04 THz. The hybrid metamaterial absorber exhibits high absorption when the incident angle reaches to 45°. Measured results indicate that the absorption amplitude and peak frequency of the hybrid metamaterial absorber is tunable in experiments. It is due to the insulator-to-metal phase transition is achieved when the measured temperature reaches to 68 °C. Moreover, the hybrid metamaterial absorber reveals high figure of merit (FOM) value when the measured temperature reaches to 68 °C.

Microwave photonic filters using low-cost sources featuring tunability, reconfigurability and negative coefficients.

PubMed

Capmany, José; Mora, José; Ortega, Beatriz; Pastor, Daniel

2005-03-07

We propose and experimentally demonstrate two configurations of photonic filters for the processing of microwave signals featuring tunability, reconfigurability and negative coefficients based on the use of low cost optical sources. The first option is a low power configuration based on spectral slicing of a broadband source. The second is a high power configuration based on fixed lasers. Tunability, reconfigurability and negative coefficients are achieved by means of a MEMS cross-connect, a variable optical attenuator array and simple 2x2 switches respectively.

Electro-optical tunable waveguide embedded multiscan Bragg gratings in lithium niobate by direct femtosecond laser writing.

PubMed

Kroesen, Sebastian; Horn, Wolfgang; Imbrock, Jörg; Denz, Cornelia

2014-09-22

optical tunable Bragg gratings in lithium niobate fabricated by direct femtosecond laser writing. The hybrid design that consists of a circular type-II waveguide and a multiscan type-I Bragg grating exhibits low loss ordinary and extraordinary polarized guiding as well as narrowband reflections in the c-band of optical communications. High bandwidth tunability of more than a peak width and nearly preserved electro-optic coefficients of r(13) = 7.59 pm V(-1) and r(33) = 23.21 pm V(-1) are demonstrated.

Widely tunable femtosecond solitonic radiation in photonic crystal fiber cladding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peng Jiahui; Sokolov, Alexei V.; Benabid, F.

2010-03-15

We report on a means to generate tunable ultrashort optical pulses. We demonstrate that dispersive waves generated by solitons within the small-core features of a photonic crystal fiber cladding can be used to obtain femtosecond pulses tunable over an octave-wide spectral range. The generation process is highly efficient and occurs at the relatively low laser powers available from a simple Ti:sapphire laser oscillator. The described phenomenon is general and will play an important role in other systems where solitons are known to exist.

Polarization nondegenerate fiber Fabry-Perot cavities with large tunable splittings

NASA Astrophysics Data System (ADS)

Cui, Jin-Ming; Zhou, Kun; Zhao, Ming-Shu; Ai, Ming-Zhong; Hu, Chang-Kang; Li, Qiang; Liu, Bi-Heng; Peng, Jin-Lan; Huang, Yun-Feng; Li, Chuan-Feng; Guo, Guang-Can

2018-04-01

We demonstrate a type of microcavity with large tunable splitting of polarization modes. This polarization nondegenerate cavity consists of two ellipsoidal concave mirrors with controllable eccentricity by CO2 laser machining on fiber end facets. The experiment shows that the cavities can combine the advantages of high finesse above 104 and large tunable polarization mode splitting to the GHz range. As the splitting of the cavity can be finely controlled to match atom hyperfine levels or optomechanics phonons, it will blaze a way in experiments on cavity quantum electrodynamics and cavity optomechanics.

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.

A high-efficiency tunable TEM-TE11 mode converter for high-power microwave applications

NASA Astrophysics Data System (ADS)

Wang, Xiao-Yu; Fan, Yu-Wei; Shu, Ting; Yuan, Cheng-wei; Zhang, Qiang

2017-03-01

The tunable high power microwave source (HPM's) is considered to be an important research direction. However, the corresponding mode converter has been researched little. In this paper, a high-efficiency tunable mode converter (HETMC) is investigated for high-power microwave applications. The HETMC that is consisted of coaxial inner and outer conductors, with four metal plates arranged radially, at 90° in the coaxial gap, and matching rods can transform coaxial transverse electromagnetic (TEM) mode to TE11 coaxial waveguide mode. The results show that adjusting the length of the downstream plate, and the distance between the rods installed upstream and the closest edges of the plates, can improve the conversion efficiency and bandwidth remarkably. Moreover, when the frequency ranges from 1.63 GHz to 2.12 GHz, the conversion efficiency is above 95% between 1.63 GHz and 2.12 GHz with a bandwidth of 26.1%. Besides, the unwished reflection and transmission can be eliminated effectively in the HETMC.

Investigation of laser dynamics, modulation and control by means of intra-cavity time varying perturbation

NASA Technical Reports Server (NTRS)

Harris, S. E.; Siegman, A. E.; Kuizenga, D. J.; Kung, A. H.; Young, J. F.; Bekkers, G. W.; Bloom, D. M.; Newton, J. H.; Phillion, D. W.

1975-01-01

The generation of tunable visible, infrared, and ultraviolet light is examined, along with the control of this light by means of novel mode-locking and modulation techniques. Transient mode-locking of the Nd:YAG laser and generation of short tunable pulses in the visible and the alkali metal inert gas excimer laser systems were investigated. Techniques for frequency conversion of high power and high energy laser radiation are discussed, along with high average power blue and UV laser light sources.

ESCAPE : a first step to high resolution solar coronagraphy in Antarctica

NASA Astrophysics Data System (ADS)

Damé, L.; Abe, L.; Faurobert, M.; Fineschi, S.; Kuzin, S.; Lamy, P.; Meftah, M.; Vives, S.

2012-06-01

The Dome C high plateau is unique for coronagraphic observations: sky brightness is reduced, water vapour is low, seeing is excellent and continuity of observations on several weeks is possible. ESCAPE (the Extreme Solar Coronagraphy Antarctic Program Experiment) will perform 2-dimensional spectroscopy of the forbidden line of FeXIV at 530.285 nm: precise line profile analysis will allow the diagnostic of the nature of waves by simultaneous measurements of velocities and intensities in the corona. ESCAPE is proposed to Institut Paul-Emile Victor (IPEV) for a campaign in 2012-2013 at Dome C/Concordia since all subsystems are available in particular thanks to an ESA STARTIGER 2010 R&D "Toward a New Generation of Formation Flying Coronagraph". Using state-of-the-art technologies developed for Space missions (a Three Mirrors Anastigmat telescope, the TMA, a 4 stages Liquid Crystal Tunable-filter Polarimeter, the LCTP) allows us to propose an automated Coronal Green Line full-field Polarimeter for unique observations (waves nature and intensity to address coronal heating) with the best possible performances on Earth and for preparing and testing the technologies for the next steps in Space. No other site would allow such coronagraphic performances (the sky brightness is a factor 2 to 4 better than in Hawaï) and with high spatial resolution (better than an arcsec is possible).

Refractory oxide hosts for a high power, broadly tunable laser with high quantum efficiency and method of making same

DOEpatents

Chen, Yok; Gonzalez, Roberto

1986-01-01

Refractory oxide crystals having high-quantum efficiency and high thermal stability for use as broadly tunable laser host materials. The crystals are formed by removing hydrogen from a single crystal of the oxide material to a level below about 10.sup.12 protons per cm.sup.3 and subsequently thermochemically reducing the oxygen content of the crystal to form sufficient oxygen anion vacancies so that short-lived F.sup.+ luminescence is produced when the crystal is optically excited.

Refractory oxide hosts for a high power, broadly tunable laser with high quantum efficiency and method of making same

DOEpatents

Chen, Yok; Gonzalez, R.

1985-07-03

Refractory oxide crystals having high-quantum efficiency and high thermal stability for use as broadly tunable laser host materials. The crystals are formed by removing hydrogen from a single crystal of the oxide material to a level below about 10/sup 12/ protons per cm/sup 3/ and subsequently thermochemically reducing the oxygen content of the crystal to form sufficient oxygen anion vacancies so that short-lived F/sup +/ luminescence is produced when the crystal is optically excited.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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 andmore » 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.« less

Vacuum-ultraviolet lasers and spectroscopy

NASA Astrophysics Data System (ADS)

Hollenstein, U.

2012-01-01

Single-photon ionisation of most atoms and molecules requires short-wavelength radiation, typically in the vacuum-ultraviolet (VUV, λ < 200 nm) or extreme ultraviolet (XUV, λ < 105 nm) region of the electromagnetic spectrum. The first VUV and XUV radiation sources used to study molecular photoabsorption and photoionisation spectra were light sources emitting a broad continuous spectrum, such as high pressure lamps or synchrotrons. Monochromatic VUV and XUV radiation was obtained using diffraction gratings in evacuated monochromators, which resulted in a resolving power ν/Δv of at best 106 (i. e. 0.1 cm-1 at 100 000 cm-1), but more typically in the range 104-105 . The invention of the laser and the development of nonlinear optical frequency-upconversion techniques enabled the development of table-top narrow-bandwidth, coherent VUV and XUV laser sources with which VUV photoabsorption, photoionisation and photoelectron spectra of molecules can be recorded at much higher resolution, the best sources having bandwidths better than 50 MHz. Such laser sources are ideally suited to study the structure and dynamics of electronically excited states of atoms and molecules and molecular photoionisation using photoabsorption, photoionisation and photoelectron spectroscopy. This chapter presents the general principles that are exploited to generate tunable narrow-band laser radiation below 200 nm and describes spectroscopic methods such as photoabsorption spectroscopy, photoionisation spectroscopy and threshold photoelectron spectroscopy that relay on the broad tunability and narrow-bandwidth of VUV radiation sources.

Stress effects in ferroelectric perovskite thin-films

NASA Astrophysics Data System (ADS)

Zednik, Ricardo Johann

The exciting class of ferroelectric materials presents the engineer with an array of unique properties that offer promise in a variety of applications; these applications include infra-red detectors ("night-vision imaging", pyroelectricity), micro-electro-mechanical-systems (MEMS, piezoelectricity), and non-volatile memory (NVM, ferroelectricity). Realizing these modern devices often requires perovskite-based ferroelectric films thinner than 100 nm. Two such technologically important material systems are (Ba,Sr)TiO3 (BST), for tunable dielectric devices employed in wireless communications, and Pb(Zr,Ti)O3 (PZT), for ferroelectric non-volatile memory (FeRAM). In general, the material behavior is strongly influenced by the mechanical boundary conditions imposed by the substrate and surrounding layers and may vary considerably from the known bulk behavior. A better mechanistic understanding of these effects is essential for harnessing the full potential of ferroelectric thin-films and further optimizing existing devices. Both materials share a common crystal structure and similar properties, but face unique challenges due to the design parameters of these different applications. Tunable devices often require very low dielectric loss as well as large dielectric tunability. Present results show that the dielectric response of BST thin-films can either resemble a dipole-relaxor or follow the accepted empirical Universal Relaxation Law (Curie-von Schweidler), depending on temperature. These behaviors in a single ferroelectric thin-film system are often thought to be mutually exclusive. In state-of-the-art high density FeRAM, the ferroelectric polarization is at least as important as the dielectric response. It was found that these properties are significantly affected by moderate biaxial tensile and compressive stresses which reversibly alter the ferroelastic domain populations of PZT at room temperature. The 90-degree domain wall motion observed by high resolution synchrotron x-ray diffraction indicates that a small effective restoring stress of about 1 MPa acts on the domain walls in these nano-crystalline PZT films. This insight allows reversible control of the ferroelectric and dielectric behavior of these important functional oxide materials, with important implications for associated integrated devices.

The characterization of an economic and portable LED-based photoacoustic imaging system to facilitate molecular imaging.

PubMed

Hariri, Ali; Lemaster, Jeanne; Wang, Junxin; Jeevarathinam, AnanthaKrishnan S; Chao, Daniel L; Jokerst, Jesse V

2018-03-01

Photoacoustic imaging (PAI) is a non-invasive, high-resolution hybrid imaging modality that combines optical excitation and ultrasound detection. PAI can image endogenous chromophores (melanin, hemoglobin, etc.) and exogenous contrast agents in different medical applications. However, most current equipment uses sophisticated and complicated OPO lasers with tuning and stability features inconsistent with broad clinical deployment. As the number of applications of PAI in medicine increases, there is an urgent need to make the imaging equipment more compact, portable, and affordable. Here, portable light emitting diode - based photoacoustic imaging (PLED-PAI) was introduced and characterized in terms of system specifications, light source characterizations, photoacoustic spatial/temporal resolution, and penetration. The system uses two LED arrays attached to the sides of a conventional ultrasound transducer. The LED pulse repetition rate is tunable between 1 K Hz, 2 K Hz, 3 K Hz, and 4 K Hz. The axial resolution was 0.268 mm, and the lateral resolution was between 0.55 and 0.59 mm. The system could detect optical absorber (pencil lead) at a depth of 3.2 cm and the detection limits of indocyanine green (ICG) and methylene blue (MB) were 9 μM and 0.78 mM. In vivo imaging of labeled human mesenchymal stem cells was achieved to confirm compatibility with small animal imaging. The characterization we report here may have value to other groups evaluating commercially available photoacoustic imaging equipment.

Widely-duration-tunable nanosecond pulse Nd:YVO4 laser based on double Pockels cells

NASA Astrophysics Data System (ADS)

He, Li-Jiao; Liu, Ke; Bo, Yong; Wang, Xiao-Jun; Yang, Jing; Liu, Zhao; Zong, Qing-Shuang; Peng, Qin-Jun; Cui, Da-Fu; Xu, Zu-Yan

2018-05-01

The development of duration-tunable pulse lasers with constant output power is important for scientific research and materials processing. We present a widely-duration-tunable nanosecond (ns) pulse Nd:YVO4 laser based on double Pockels cells (PCs), i.e. inserting an extra PC into a conventional electro-optic Q-switched cavity dumped laser resonator. Under the absorbed pump power of 24.9 W, the pulse duration is adjustable from 31.9 ns to 5.9 ns by changing the amplitude of the high voltage on the inserted PC from 1100 V to 4400 V at the pulse repetition rate of 10 kHz. The corresponding average output power is almost entirely maintained in the range of 3.5–4.1 W. This represents more than three times increase in pulse duration tunable regime and average power compared to previously reported results for duration-tunable ns lasers. The laser beam quality factor was measured to be M 2  <  1.18.

Electronic sideband locking of a broadly tunable 318.6 nm ultraviolet laser to an ultra-stable optical cavity

NASA Astrophysics Data System (ADS)

Bai, Jiandong; Wang, Jieying; He, Jun; Wang, Junmin

2017-04-01

We demonstrate frequency stabilization of a tunable 318.6 nm ultraviolet (UV) laser system using electronic sideband locking. By indirectly changing the frequency of a broadband electro-optic phase modulator, the laser can be continuously tuned over 4 GHz, while a 637.2 nm laser is directly stabilized to a high-finesse ultra-stable optical cavity. The doubling cavity also remains locked to the 637.2 nm light. We show that the tuning range depends mainly on the gain-flattening region of the modulator and the piezo-tunable range of the seed laser. The frequency-stabilized tunable UV laser system is able to compensate for the offset between reference and target frequencies, and has potential applications in precision spectroscopy of cold atoms.

Broad Wavelength Tunable Robust Lasing from Single-Crystal Nanowires of Cesium Lead Halide Perovskites (CsPbX3, X = Cl, Br, I).

PubMed

Fu, Yongping; Zhu, Haiming; Stoumpos, Constantinos C; Ding, Qi; Wang, Jue; Kanatzidis, Mercouri G; Zhu, Xiaoyang; Jin, Song

2016-08-23

Lead halide perovskite nanowires (NWs) are emerging as a class of inexpensive semiconductors with broad bandgap tunability for optoelectronics, such as tunable NW lasers. Despite exciting progress, the current organic-inorganic hybrid perovskite NW lasers suffer from limited tunable wavelength range and poor material stability. Herein, we report facile solution growth of single-crystal NWs of inorganic perovskite CsPbX3 (X = Br, Cl) and their alloys [CsPb(Br,Cl)3] and a low-temperature vapor-phase halide exchange method to convert CsPbBr3 NWs into perovskite phase CsPb(Br,I)3 alloys and metastable CsPbI3 with well-preserved perovskite crystal lattice and NW morphology. These single crystalline NWs with smooth end facets and subwavelength dimensions are ideal Fabry-Perot cavities for NW lasers. Optically pumped tunable lasing across the entire visible spectrum (420-710 nm) is demonstrated at room temperature from these NWs with low lasing thresholds and high-quality factors. Such highly efficient lasing similar to what can be achieved with organic-inorganic hybrid perovskites indicates that organic cation is not essential for light emission application from these lead halide perovskite materials. Furthermore, the CsPbBr3 NW lasers show stable lasing emission with no measurable degradation after at least 8 h or 7.2 × 10(9) laser shots under continuous illumination, which are substantially more robust than their organic-inorganic counterparts. The Cs-based perovskites offer a stable material platform for tunable NW lasers and other nanoscale optoelectronic devices.

Electrically tunable metasurface perfect absorbers for ultrathin mid-infrared optical modulators.

PubMed

Yao, Yu; Shankar, Raji; Kats, Mikhail A; Song, Yi; Kong, Jing; Loncar, Marko; Capasso, Federico

2014-11-12

Dynamically reconfigurable metasurfaces open up unprecedented opportunities in applications such as high capacity communications, dynamic beam shaping, hyperspectral imaging, and adaptive optics. The realization of high performance metasurface-based devices remains a great challenge due to very limited tuning ranges and modulation depths. Here we show that a widely tunable metasurface composed of optical antennas on graphene can be incorporated into a subwavelength-thick optical cavity to create an electrically tunable perfect absorber. By switching the absorber in and out of the critical coupling condition via the gate voltage applied on graphene, a modulation depth of up to 100% can be achieved. In particular, we demonstrated ultrathin (thickness < λ0/10) high speed (up to 20 GHz) optical modulators over a broad wavelength range (5-7 μm). The operating wavelength can be scaled from the near-infrared to the terahertz by simply tailoring the metasurface and cavity dimensions.

Color display and encryption with a plasmonic polarizing metamirror

NASA Astrophysics Data System (ADS)

Song, Maowen; Li, Xiong; Pu, Mingbo; Guo, Yinghui; Liu, Kaipeng; Yu, Honglin; Ma, Xiaoliang; Luo, Xiangang

2018-01-01

Structural colors emerge when a particular wavelength range is filtered out from a broadband light source. It is regarded as a valuable platform for color display and digital imaging due to the benefits of environmental friendliness, higher visibility, and durability. However, current devices capable of generating colors are all based on direct transmission or reflection. Material loss, thick configuration, and the lack of tunability hinder their transition to practical applications. In this paper, a novel mechanism that generates high-purity colors by photon spin restoration on ultrashallow plasmonic grating is proposed. We fabricated the sample by interference lithography and experimentally observed full color display, tunable color logo imaging, and chromatic sensing. The unique combination of high efficiency, high-purity colors, tunable chromatic display, ultrathin structure, and friendliness for fabrication makes this design an easy way to bridge the gap between theoretical investigations and daily-life applications.

Tunable circuit for tunable capacitor devices

DOEpatents

Rivkina, Tatiana; Ginley, David S.

2006-09-19

A tunable circuit (10) for a capacitively tunable capacitor device (12) is provided. The tunable circuit (10) comprises a tunable circuit element (14) and a non-tunable dielectric element (16) coupled to the tunable circuit element (16). A tunable capacitor device (12) and a method for increasing the figure of merit in a tunable capacitor device (12) are also provided.

Highlighting the DNA damage response with ultrashort laser pulses in the near infrared and kinetic modeling

PubMed Central

Ferrando-May, Elisa; Tomas, Martin; Blumhardt, Philipp; Stöckl, Martin; Fuchs, Matthias; Leitenstorfer, Alfred

2013-01-01

Our understanding of the mechanisms governing the response to DNA damage in higher eucaryotes crucially depends on our ability to dissect the temporal and spatial organization of the cellular machinery responsible for maintaining genomic integrity. To achieve this goal, we need experimental tools to inflict DNA lesions with high spatial precision at pre-defined locations, and to visualize the ensuing reactions with adequate temporal resolution. Near-infrared femtosecond laser pulses focused through high-aperture objective lenses of advanced scanning microscopes offer the advantage of inducing DNA damage in a 3D-confined volume of subnuclear dimensions. This high spatial resolution results from the highly non-linear nature of the excitation process. Here we review recent progress based on the increasing availability of widely tunable and user-friendly technology of ultrafast lasers in the near infrared. We present a critical evaluation of this approach for DNA microdamage as compared to the currently prevalent use of UV or VIS laser irradiation, the latter in combination with photosensitizers. Current and future applications in the field of DNA repair and DNA-damage dependent chromatin dynamics are outlined. Finally, we discuss the requirement for proper simulation and quantitative modeling. We focus in particular on approaches to measure the effect of DNA damage on the mobility of nuclear proteins and consider the pros and cons of frequently used analysis models for FRAP and photoactivation and their applicability to non-linear photoperturbation experiments. PMID:23882280

High extinction ratio and low transmission loss thin-film terahertz polarizer with a tunable bilayer metal wire-grid structure.

PubMed

Huang, Zhe; Parrott, Edward P J; Park, Hongkyu; Chan, Hau Ping; Pickwell-MacPherson, Emma

2014-02-15

A thin-film terahertz polarizer is proposed and realized via a tunable bilayer metal wire-grid structure to achieve high extinction ratios and good transmission. The polarizer is fabricated on top of a thin silica layer by standard micro-fabrication techniques to eliminate the multireflection effects. The tunable alignment of the bilayer aluminum-wire grid structure enables tailoring of the extinction ratio and transmission characteristics. Using terahertz time-domain spectroscopy (THz-TDS), a fabricated polarizer is characterized, with extinction ratios greater than 50 dB and transmission losses below 1 dB reported in the 0.2-1.1 THz frequency range. These characteristics can be improved by further tuning the polarizer parameters such as the pitch, metal film thickness, and lateral displacement.

Compensation for first-order polarization-mode dispersion by using a novel tunable compensator

NASA Astrophysics Data System (ADS)

Qiu, Feng; Ning, Tigang; Pei, Shanshan; Xing, Yujun; Jian, Shuisheng

2005-01-01

Polarization-related impairments have become a critical issue for high-data-rate optical systems, particularly when considering polarization-mode dispersion (PMD). Consequently, compensation of PMD, especially for the first-order PMD is necessary to maintain adequate performance in long-haul systems at a high bit rate of 10 Gb/s or beyond. In this paper, we successfully demonstrated automatic and tunable compensation for first-order polarization-mode dispersion. Furthermore, we reported the statistical assessment of this tunable compensator at 10 Gbit/s. Experimental results, including bit error rate measurements, are successfully compared with theory, therefore demonstrating the compensator efficiency at 10 Gbit/s. The first-order PMD was max 274 ps before PMD compensation, and it was lower than 7ps after PMD compensation.

Tunable and high-purity room temperature single-photon emission from atomic defects in hexagonal boron nitride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grosso, Gabriele; Moon, Hyowon; Lienhard, Benjamin

Two-dimensional van der Waals materials have emerged as promising platforms for solid-state quantum information processing devices with unusual potential for heterogeneous assembly. Recently, bright and photostable single photon emitters were reported from atomic defects in layered hexagonal boron nitride (hBN), but controlling inhomogeneous spectral distribution and reducing multi-photon emission presented open challenges. Here, we demonstrate that strain control allows spectral tunability of hBN single photon emitters over 6 meV, and material processing sharply improves the single photon purity. We observe high single photon count rates exceeding 7 × 10 6 counts per second at saturation, after correcting for uncorrelated photonmore » background. Furthermore, these emitters are stable to material transfer to other substrates. High-purity and photostable single photon emission at room temperature, together with spectral tunability and transferability, opens the door to scalable integration of high-quality quantum emitters in photonic quantum technologies.« less

Overview of Mono-Energetic Gamma-Ray Sources and Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hartemann, Fred; /LLNL, Livermore; Albert, Felicie

2012-06-25

Recent progress in accelerator physics and laser technology have enabled the development of a new class of tunable gamma-ray light sources based on Compton scattering between a high-brightness, relativistic electron beam and a high intensity laser pulse produced via chirped-pulse amplification (CPA). A precision, tunable Mono-Energetic Gamma-ray (MEGa-ray) source driven by a compact, high-gradient X-band linac is currently under development and construction at LLNL. High-brightness, relativistic electron bunches produced by an X-band linac designed in collaboration with SLAC NAL will interact with a Joule-class, 10 ps, diode-pumped CPA laser pulse to generate tunable {gamma}-rays in the 0.5-2.5 MeV photon energymore » range via Compton scattering. This MEGaray source will be used to excite nuclear resonance fluorescence in various isotopes. Applications include homeland security, stockpile science and surveillance, nuclear fuel assay, and waste imaging and assay. The source design, key parameters, and current status are presented, along with important applications, including nuclear resonance fluorescence.« less

Tunable and high-purity room temperature single-photon emission from atomic defects in hexagonal boron nitride

DOE PAGES

Grosso, Gabriele; Moon, Hyowon; Lienhard, Benjamin; ...

2017-09-26

Two-dimensional van der Waals materials have emerged as promising platforms for solid-state quantum information processing devices with unusual potential for heterogeneous assembly. Recently, bright and photostable single photon emitters were reported from atomic defects in layered hexagonal boron nitride (hBN), but controlling inhomogeneous spectral distribution and reducing multi-photon emission presented open challenges. Here, we demonstrate that strain control allows spectral tunability of hBN single photon emitters over 6 meV, and material processing sharply improves the single photon purity. We observe high single photon count rates exceeding 7 × 10 6 counts per second at saturation, after correcting for uncorrelated photonmore » background. Furthermore, these emitters are stable to material transfer to other substrates. High-purity and photostable single photon emission at room temperature, together with spectral tunability and transferability, opens the door to scalable integration of high-quality quantum emitters in photonic quantum technologies.« less

Fluorescence tomography using synchrotron radiation at the NSLS

NASA Astrophysics Data System (ADS)

Boisseau, P.; Grodzins, L.

1987-03-01

Fluorescence tomography utilizing focussed, tunable, monoenergetic X-rays from synchrotron light sources hold the promise of a non-invasive analytic tool for studying trace elements in specimens, particularly biological, at spatial resolutions of the order of micrometers. This note reports an early test at the National Synchrotron Light Source at Brookhaven National Laboratories in which fluorescence tomographic scans were successfully made of trace elements of iron and titanium in NBS standard glass and in a bee.

Infrared absorption-coefficient data on SF6 applicable to atmospheric remote sensing

NASA Technical Reports Server (NTRS)

Varanasi, P.; Gopalan, A.; Brannon, J. F., Jr.

1992-01-01

Spectral absorption coefficients, k(nu)/cm per atm, of SF6 have been measured in the central Q-branches of the nu(3)-fundamental at 947/cm at various temperature-pressure combinations representing tangent heights in solar-occultation experiments or layers in the atmosphere. The data obtained with the Doppler-limited spectral resolution (about 0.0001/cm) of a tunable-diode laser spectrometer are useful in the atmospheric remote sensing of this trace gas.

Near-field examination of perovskite-based superlenses and superlens-enhanced probe-object coupling.

PubMed

Kehr, S C; Liu, Y M; Martin, L W; Yu, P; Gajek, M; Yang, S-Y; Yang, C-H; Wenzel, M T; Jacob, R; von Ribbeck, H-G; Helm, M; Zhang, X; Eng, L M; Ramesh, R

2011-01-01

A planar slab of negative-index material works as a superlens with sub-diffraction-limited resolution, as propagating waves are focused and, moreover, evanescent waves are reconstructed in the image plane. Here we demonstrate a superlens for electric evanescent fields with low losses using perovskites in the mid-infrared regime. The combination of near-field microscopy with a tunable free-electron laser allows us to address precisely the polariton modes, which are critical for super-resolution imaging. We spectrally study the lateral and vertical distributions of evanescent waves around the image plane of such a lens, and achieve imaging resolution of λ/14 at the superlensing wavelength. Interestingly, at certain distances between the probe and sample surface, we observe a maximum of these evanescent fields. Comparisons with numerical simulations indicate that this maximum originates from an enhanced coupling between probe and object, which might be applicable for multifunctional circuits, infrared spectroscopy and thermal sensors.

New design for a time-of-flight mass spectrometer with a liquid beam laser desorption ion source for the analysis of biomolecules

NASA Astrophysics Data System (ADS)

Charvat, A.; Lugovoj, E.; Faubel, M.; Abel, B.

2004-05-01

We describe a novel liquid beam mass spectrometer, based on a recently discovered nanosecond laser desorption phenomenon, [W. Kleinekofort, J. Avdiev, and B. Brutschy, Int. J. Mass Ion. Processes 152, 135 (1996)] which allows the liquid-to-vacuum transfer, and subsequent mass analysis of pre-existing ions and ionic associates from liquid microjets of aqueous solutions. The goal of our novel technical approach is to establish a system with good mass resolution that implements improvements on critical components that make the system more reliable and easier to operate. For laser desorption pulsed dye-laser difference frequency mixing is used that provides tunable infrared light near the absorption maximum of liquid water around 3 μm. Different types of liquid beam glass nozzles (convergent capillary and aperture plate nozzles) are investigated and characterized. Starting from theoretical considerations of hydrodynamic drag forces on micrometer size droplets in supersonic rarefied gas flows we succeeded in capturing efficiently the liquid beam in a liquid beam recycling trap operating at the vapor pressure of liquid water. For improving the pollution resistance, the liquid jet high vacuum ion source region is spatially separated from the reflectron time-of-flight mass spectrometer (TOF-MS) working behind a gate valve in an ultrahigh vacuum environment. A simple (simulation optimized) ion optics is employed for the ion transfer from the source to the high vacuum region. This new feature is also mostly responsible for the improved mass resolution. With the present tandem-TOF-MS setup a resolution of m/Δm≈1800 for the low and m/Δm≈700 in the high mass region has been obtained for several biomolecules of different mass and complexity (amino acids, insulin, and cytochrome c).

Responsive Hydrogel-based Photonic Nanochains for Microenvironment Sensing and Imaging in Real Time and High Resolution.

PubMed

Luo, Wei; Cui, Qian; Fang, Kai; Chen, Ke; Ma, Huiru; Guan, Jianguo

2018-01-17

Microenvironment sensing and imaging are of importance in microscale zones like microreactors, microfluidic systems, and biological cells. But they are so far implemented only based on chemical colors from dyes or quantum dots, which suffered either from photobleaching, quenching, or photoblinking behaviors, or from limited color gamut. In contrast, structural colors from hydrogel-based photonic crystals (PCs) may be stable and tunable in the whole visible spectrum by diffraction peak shift, facilitating the visual detection with high accuracy. However, the current hydrogel-based PCs are all inappropriate for microscale detection due to the bulk size. Here we demonstrate the smallest hydrogel-based PCs, responsive hydrogel-based photonic nanochains with high-resolution and real-time response, by developing a general hydrogen bond-guided template polymerization method. A variety of mechanically separated stimuli-responsive hydrogel-based photonic nanochains have been obtained in a large scale including those responding to pH, solvent, and temperature. Each of them has a submicrometer diameter and is composed of individual one-dimensional periodic structure of magnetic particles locked by a tens-of-nanometer-thick peapod-like responsive hydrogel shell. Taking the pH-responsive hydrogel-based photonic nanochains, for example, pH-induced hydrogel volume change notably alters the nanochain length, resulting in a significant variation of the structural color. The submicrometer size endows the nanochains with improved resolution and response time by 2-3 orders of magnitude than the previous counterparts. Our results for the first time validate the feasibility of using structural colors for microenvironment sensing and imaging and may further promote the applications of responsive PCs, such as in displays and printing.

Diode laser spectroscopy: precise spectral line shape measurements

NASA Astrophysics Data System (ADS)

Nadezhdinskii, A. I.

1996-07-01

When one speaks about modern trends in tunable diode laser spectroscopy (TDLS) one should mention that precise line shape measurements have become one of the most promising applications of diode lasers in high resolution molecular spectroscopy. Accuracy limitations of TDL spectrometers are considered in this paper, proving the ability to measure spectral line profile with precision better than 1%. A four parameter Voigt profile is used to fit the experimental spectrum, and the possibility of line shift measurements with an accuracy of 2 × 10 -5 cm -1 is shown. Test experiments demonstrate the error line intensity ratios to be less than 0.3% for the proposed approach. Differences between "soft" and "hard" models of line shape have been observed experimentally for the first time. Some observed resonance effects are considered with respect to collision adiabacity.

Dirac State in Giant Magnetoresistive Materials

NASA Astrophysics Data System (ADS)

Wu, Y.; Jo, N. H.; Ochi, M.; Huang, L.; Mou, D.; Kong, T.; Mun, E.; Wang, L.; Lee, Y.; Bud'Ko, S. L.; Canfield, P. C.; Trivedi, N.; Arito, R.; Kaminski, A.

We use ultrahigh resolution, tunable, vacuum ultraviolet laser-based angle-resolved photoemission spectroscopy (ARPES) to study the electronic properties of materials that recently were discovered to display titanic magnetoresistance. We find that that several of these materials have Dirac-like features in their band structure. In some materials those features are ``ordinary'' Dirac cones, while in others the linear Dirac dispersion of two crossing bands forms a linear object in 3D momentum space. Our observation poses an important question about the role of Dirac dispersion in the unusually high, non-saturating magnetoresistance of these materials. Research was supported by the US DOE, Office of Basic Energy Sciences under Contract No. DE-AC02-07CH11358; Gordon and Betty Moore Foundation EPiQS Initiative (Grant No. GBMF4411); CEM, a NSF MRSEC, under Grant No. DMR-1420451.

Erbium-doped fiber ring resonator for resonant fiber optical gyro applications

NASA Astrophysics Data System (ADS)

Li, Chunming; Zhao, Rui; Tang, Jun; Xia, Meijing; Guo, Huiting; Xie, Chengfeng; Wang, Lei; Liu, Jun

2018-04-01

This paper reports a fiber ring resonator with erbium-doped fiber (EDF) for resonant fiber optical gyro (RFOG). To analyze compensation mechanism of the EDF on resonator, a mathematical model of the erbium-doped fiber ring resonator (EDFRR) is established based on Jones matrix to be followed by the design and fabrication of a tunable EDFRR. The performances of the fabricated EDFRR were measured and the experimental Q-factor of 2 . 47 × 108 and resonant depth of 109% were acquired separately. Compared with the resonator without the EDF, the resonant depth and Q-factor of the proposed device are increased by 2.5 times and 14 times, respectively. A potential optimum shot noise limited resolution of 0 . 042∘ / h can be obtained for the RFOG, which is promising for low-cost and high precise detection.

Two-Dimensional Dirac Fermions Protected by Space-Time Inversion Symmetry in Black Phosphorus

NASA Astrophysics Data System (ADS)

Kim, Jimin; Baik, Seung Su; Jung, Sung Won; Sohn, Yeongsup; Ryu, Sae Hee; Choi, Hyoung Joon; Yang, Bohm-Jung; Kim, Keun Su

2017-12-01

We report the realization of novel symmetry-protected Dirac fermions in a surface-doped two-dimensional (2D) semiconductor, black phosphorus. The widely tunable band gap of black phosphorus by the surface Stark effect is employed to achieve a surprisingly large band inversion up to ˜0.6 eV . High-resolution angle-resolved photoemission spectra directly reveal the pair creation of Dirac points and their movement along the axis of the glide-mirror symmetry. Unlike graphene, the Dirac point of black phosphorus is stable, as protected by space-time inversion symmetry, even in the presence of spin-orbit coupling. Our results establish black phosphorus in the inverted regime as a simple model system of 2D symmetry-protected (topological) Dirac semimetals, offering an unprecedented opportunity for the discovery of 2D Weyl semimetals.

Hyperfine structure of atomic fluorine (F I)

NASA Astrophysics Data System (ADS)

Huo, Xiaoxue; Deng, Lunhua; Windholz, L.; Mu, Xiuli; Wang, Hailing

2018-01-01

A high resolution absorption spectrum of neutral fluorine(F I) was observed around 800 nm using concentration modulation absorption spectroscopy with a tunable Ti : Sapphire laser. The fluorine atoms were produced by discharging the mixed gases of helium and sulfur hexafluoride (SF6) in a glass tube. Thirty four hyperfine structure (hfs) resolved transitions were analyzed to obtain 23 magnetic dipole hfs constants A for 2p4(3P)3s, 2p4(3P)3p and 2p4(3P)3d configurations. The hfs constants in 2p4(3P)3s and 2p4(3P)3p configurations were compared with those obtained from experiments and calculations. Fifteen constants in 2p4(3P)3d configuration were reported - to our knowledge - for the first time.

Efficient multicolor tunability of ultrasmall ternary-doped LaF3 nanoparticles: energy conversion and magnetic behavior.

PubMed

Shrivastava, Navadeep; Khan, L U; Vargas, J M; Ospina, Carlos; Coaquira, J A Q; Zoppellaro, Giorgio; Brito, H F; Javed, Yasir; Shukla, D K; Felinto, M C F C; Sharma, Surender K

2017-07-19

Luminescence-tunable multicolored LaF 3 :xCe 3+ ,xGd 3+ ,yEu 3+ (x = 5; y = 1, 5, 10, and 15 mol%) nanoparticles have been synthesized via a low cost polyol method. Powder X-ray diffraction and high-resolution transmission electron microscopy studies confirm the hexagonal phase of the LaF 3 :xCe 3+ ,xGd 3+ ,yEu 3+ nanophosphors with average sizes (oval shape) ranging from 5 to 7 nm. Energy-dispersive X-ray spectroscopy analyses show the uniform distribution of Ce 3+ , Gd 3+ , and Eu 3+ dopants in the LaF 3 host matrix. The photoluminescence spectra and electron paramagnetic resonance measurements guarantee the presence of Eu 2+ , corroborated through DC susceptibility measurements of the samples displaying paramagnetic behavior at 300 K, whereas weak ferromagnetic ordering is shown at 2 K. The non-radiative energy transfer processes from the 4f( 2 F 5/2 ) → 5d state (Ce 3+ ) to the intraconfigurational 4f excited levels of rare earth ions and simultaneous emissions in the visible region from the 4f 6 5d 1 (Eu 2+ ) and 5 D 0 (Eu 3+ ) emitting levels, leading to overlapped broad and narrow emission bands, have been proclaimed. The energy transfer mechanism proposes involvement of the Gd 3+ ion sub-lattice as the bridge and finally trapping by Eu 2+/3+ , upon excitation of the Ce 3+ ion. The calculation of experimental intensity parameters (Ω 2,4 ) has been discussed and the highest emission quantum efficiency (η = 85%) of the Eu 3+ ion for the y = 10 mol% sample is reported. The advantageous existence of the Eu 2+ /Eu 3+ ratio along with variously doped nanomaterials described in this work, results in tunable emission color in the blue-white-red regions, highlighting the potential application of the samples in solid-state lighting devices, scintillation devices, and multiplex detection.

gram-scale metafluids and large area tunable metamaterials: design, fabrication, and nano-optical tomographic characterization (Conference Presentation)

NASA Astrophysics Data System (ADS)

Dionne, Jennifer A.

2016-09-01

Advances in metamaterials and metasurfaces have enabled unprecedented control of light-matter interactions. Metamaterial constituents support high-frequency electric and magnetic dipoles, which can be used as building blocks for new materials capable of negative refraction, electromagnetic cloaking, strong visible-frequency circular dichroism, and enhanced magnetic or chiral transitions in ions and molecules. However, most metamaterials to date have been limited to solid-state, static, narrow-band, and/or small-area structures. Here, we introduce the design, fabrication, and three-dimensional nano-optical characterization of large-area, dynamically-tunable metamaterials and gram-scale metafluids. First, we use transformation optics to design a broadband metamaterial constituent - a metallo-dielectric nanocrescent - characterized by degenerate electric and magnetic dipoles. A periodic array of nanocrescents exhibits large positive and negative refractive indices at optical frequencies, confirmed through simulations of plane wave refraction through a metamaterial prism. Simulations also reveal that the metamaterial optical properties are largely insensitive to the wavelength, orientation and polarization of incident light. Then, we introduce a new tomographic technique, cathodoluminescence (CL) spectroscopic tomography, to probe light-matter interactions in individual nanocrescents with nanometer-scale resolution. Two-dimensional CL maps of the three-dimensional nanostructure are obtained at various orientations, while a filtered back projection is used to reconstruct the CL intensity at each wavelength. The resulting tomograms allow us to locate regions of efficient cathodoluminescence in three dimensions across visible and near-infrared wavelengths, with contributions from material luminescence and radiative decay of electromagnetic eigenmodes. Finally, we demonstrate the fabrication of dynamically tunable large-area metamaterials and gram-scale metafluids, using a combination of colloidal synthesis, protein-directed assembly, self-assembly, etching, and stamping. The electric and magnetic response of the bulk metamaterial and metafluid are directly probed with optical scattering and spectroscopy. Using chemical swelling, these metamaterials exhibit reversible, unity-order refractive index changes that may provide a foundation for new adaptive optical materials in sensing, solar, and display applications.

Tunable mode and line selection by injection in a TEA CO2 laser

NASA Technical Reports Server (NTRS)

Menzies, R. T.; Flamant, P. H.; Kavaya, M. J.; Kuiper, E. N.

1984-01-01

Tunable mode selection by injection in pulsed CO2 lasers is examined, and both analytical and numerical models are used to compute the required injection power for a variety of experimental cases. These are treated in two categories: mode selection at a desired frequency displacement from the center frequency of a transition line in a dispersive cavity and mode (and line) selection at the center frequency of a selected transition line in a nondispersive cavity. The results point out the potential flexibility of pulsed injection in providing wavelength tunable high-energy single-frequency pulses.

Exploiting dimensionality and defect mitigation to create tunable microwave dielectrics

NASA Astrophysics Data System (ADS)

Lee, Che-Hui; Orloff, Nathan D.; Birol, Turan; Zhu, Ye; Goian, Veronica; Rocas, Eduard; Haislmaier, Ryan; Vlahos, Eftihia; Mundy, Julia A.; Kourkoutis, Lena F.; Nie, Yuefeng; Biegalski, Michael D.; Zhang, Jingshu; Bernhagen, Margitta; Benedek, Nicole A.; Kim, Yongsam; Brock, Joel D.; Uecker, Reinhard; Xi, X. X.; Gopalan, Venkatraman; Nuzhnyy, Dmitry; Kamba, Stanislav; Muller, David A.; Takeuchi, Ichiro; Booth, James C.; Fennie, Craig J.; Schlom, Darrell G.

2013-10-01

The miniaturization and integration of frequency-agile microwave circuits--relevant to electronically tunable filters, antennas, resonators and phase shifters--with microelectronics offers tantalizing device possibilities, yet requires thin films whose dielectric constant at gigahertz frequencies can be tuned by applying a quasi-static electric field. Appropriate systems such as BaxSr1-xTiO3 have a paraelectric-ferroelectric transition just below ambient temperature, providing high tunability. Unfortunately, such films suffer significant losses arising from defects. Recognizing that progress is stymied by dielectric loss, we start with a system with exceptionally low loss--Srn+1TinO3n+1 phases--in which (SrO)2 crystallographic shear planes provide an alternative to the formation of point defects for accommodating non-stoichiometry. Here we report the experimental realization of a highly tunable ground state arising from the emergence of a local ferroelectric instability in biaxially strained Srn+1TinO3n+1 phases with n>=3 at frequencies up to 125GHz. In contrast to traditional methods of modifying ferroelectrics--doping or strain--in this unique system an increase in the separation between the (SrO)2 planes, which can be achieved by changing n, bolsters the local ferroelectric instability. This new control parameter, n, can be exploited to achieve a figure of merit at room temperature that rivals all known tunable microwave dielectrics.

Generation of high-energy sub-20 fs pulses tunable in the 250-310 nm region by frequency doubling of a high-power noncollinear optical parametric amplifier.

PubMed

Beutler, Marcus; Ghotbi, Masood; Noack, Frank; Brida, Daniele; Manzoni, Cristian; Cerullo, Giulio

2009-03-15

We report on the generation of powerful sub-20 fs deep UV pulses with 10 microJ level energy and broadly tunable in the 250-310 nm range. These pulses are produced by frequency doubling a high-power noncollinear optical parametric amplifier and compressed by a pair of MgF2 prisms to an almost transform-limited duration. Our results provide a power scaling by an order of magnitude with respect to previous works.

LASER BIOLOGY AND MEDICINE: Application of tunable diode lasers for a highly sensitive analysis of gaseous biomarkers in exhaled air

NASA Astrophysics Data System (ADS)

Stepanov, E. V.; Milyaev, Varerii A.

2002-11-01

The application of tunable diode lasers for a highly sensitive analysis of gaseous biomarkers in exhaled air in biomedical diagnostics is discussed. The principle of operation and the design of a laser analyser for studying the composition of exhaled air are described. The results of detection of gaseous biomarkers in exhaled air, including clinical studies, which demonstrate the diagnostic possibilities of the method, are presented.

Optoelectronic Devices Based on Novel Semiconductor Structures

DTIC Science & Technology

2006-06-14

superlattices 4. TEM study and band -filling effects in quantum-well dots 5. Improvements on tuning ranges and output powers for widely-tunable THz sources...the pump power increases the relative strength for the QW emission in the QWD sample also increases. Eventually at the sufficiently- high pump power ...Ahopelto, Appl. Phys. Lett. 66, 2364 (1995). 5. A monochromatic and high - power THz source tunable in the ranges of 2.7-38.4 ptm and 58.2-3540 ptm for

Infrared fiber coupled acousto-optic tunable filter spectrometer

NASA Technical Reports Server (NTRS)

Levin, K. H.; Kindler, E.; Ko, T.; Lee, F.; Tran, D. C.; Tapphorn, R. M.

1990-01-01

A spectrometer design is introduced which combines an acoustooptic tunable filter (AOTF) and IR-transmitting flouride-glass fibers. The AOTF crystal is fabricated from TeO2 and permits random access to any wavelength in less than 50 microseconds, and the resulting spectrometer is tested for the remote analysis of gases and hydrocarbons. The AOTF spectrometer, when operated with a high-speed frequency synthesizer and optimized algorithms, permits accurate high-speed spectroscopy in the mid-IR spectral region.

Polarization-independent fiber filter with an all-polarization-maintaining fiber loop for tunable fiber lasers

NASA Astrophysics Data System (ADS)

Zhang, Jun; Wu, Weiran; Rao, Qi; Zhou, Kejiang

2018-05-01

Tunable fiber lasers are a promising light source in all-optical wavelength conversion, fiber grating sensing and optical add-drop multiplexing. In order to achieve a tunable wavelength in the output, optical filters are indispensable for the construction of tunable fiber lasers. Recently, much attention has been given to developing high-performance filters. This paper proposes an environment-insensitive filter based on a Sagnac interferometer which was designed by an all-polarization-maintaining fiber with linear birefringence. According to the Sagnac interferometer, we derived the transfer function of an environment-insensitive filter. Based on this principle, it is shown that the device is able to implement a precision filtering function that can be used in a fiber laser’s optical resonant cavity. The experiment results demonstrated the effectiveness of this structure.

1.7  μm band narrow-linewidth tunable Raman fiber lasers pumped by spectrum-sliced amplified spontaneous emission.

PubMed

Zhang, Peng; Wu, Di; Du, Quanli; Li, Xiaoyan; Han, Kexuan; Zhang, Lizhong; Wang, Tianshu; Jiang, Huilin

2017-12-10

A 1.7 μm band tunable narrow-linewidth Raman fiber laser based on spectrally sliced amplified spontaneous emission (SS-ASE) and multiple filter structures is proposed and experimentally demonstrated. In this scheme, an SS-ASE source is employed as a pump source in order to avoid stimulated Brillouin scattering. The ring configuration includes a 500 m long high nonlinear optical fiber and a 10 km long dispersion shifted fiber as the gain medium. A segment of un-pumped polarization-maintaining erbium-doped fiber is used to modify the shape of the spectrum. Furthermore, a nonlinear polarization rotation scheme is applied as the wavelength selector to generate lasers. A high-finesse ring filter and a ring filter are used to narrow the linewidth of the laser, respectively. We demonstrate tuning capabilities of a single laser over 28 nm between 1652 nm and 1680 nm by adjusting the polarization controller (PC) and tunable filter. The tunable laser has a 0.023 nm effective linewidth with the high-finesse ring filter. The stable multi-wavelength laser operation of up to four wavelengths can be obtained by adjusting the PC carefully when the pump power increases.

Efficient color-tunable multiexcitonic dual wavelength emission from Type II semiconductor tetrapods.

PubMed

Wu, Wen-Ya; Li, Mingjie; Lian, Jie; Wu, Xiangyang; Yeow, Edwin K L; Jhon, Mark H; Chan, Yinthai

2014-09-23

We synthesized colloidal InP/ZnS seeded CdS tetrapods by harnessing the structural stability of the InP/ZnS seed nanocrystals at the high reaction temperatures needed to grow the CdS arms. Because of an unexpected Type II band alignment at the interface of the InP/ZnS core and CdS arms that enhanced the occurrence of radiative excitonic recombination in CdS, these tetrapods were found to be capable of exhibiting highly efficient multiexcitonic dual wavelength emission of equal intensity at spectrally distinct wavelengths of ∼485 and ∼675 nm. Additionally, the Type II InP/ZnS seeded CdS tetrapods displayed a wider range of pump-dependent emission color-tunability (from red to white to blue) within the context of a CIE 1931 chromaticity diagram and possessed higher photostability due to suppressed multiexcitonic Auger recombination when compared to conventional Type I CdSe seeded CdS tetrapods. By employing time-resolved spectroscopy measurements, we were able to attribute the wide emission color-tunability to the large valence band offset between InP and CdS. This work highlights the importance of band alignment in the synthetic design of semiconductor nanoheterostructures, which can exhibit color-tunable multiwavelength emission with high efficiency and photostability.

Dynamics of person-to-person interactions from distributed RFID sensor networks.

PubMed

Cattuto, Ciro; Van den Broeck, Wouter; Barrat, Alain; Colizza, Vittoria; Pinton, Jean-François; Vespignani, Alessandro

2010-07-15

Digital networks, mobile devices, and the possibility of mining the ever-increasing amount of digital traces that we leave behind in our daily activities are changing the way we can approach the study of human and social interactions. Large-scale datasets, however, are mostly available for collective and statistical behaviors, at coarse granularities, while high-resolution data on person-to-person interactions are generally limited to relatively small groups of individuals. Here we present a scalable experimental framework for gathering real-time data resolving face-to-face social interactions with tunable spatial and temporal granularities. We use active Radio Frequency Identification (RFID) devices that assess mutual proximity in a distributed fashion by exchanging low-power radio packets. We analyze the dynamics of person-to-person interaction networks obtained in three high-resolution experiments carried out at different orders of magnitude in community size. The data sets exhibit common statistical properties and lack of a characteristic time scale from 20 seconds to several hours. The association between the number of connections and their duration shows an interesting super-linear behavior, which indicates the possibility of defining super-connectors both in the number and intensity of connections. Taking advantage of scalability and resolution, this experimental framework allows the monitoring of social interactions, uncovering similarities in the way individuals interact in different contexts, and identifying patterns of super-connector behavior in the community. These results could impact our understanding of all phenomena driven by face-to-face interactions, such as the spreading of transmissible infectious diseases and information.

Two-Photon-Excited Silica and Organosilica Nanoparticles for Spatiotemporal Cancer Treatment.

PubMed

Croissant, Jonas G; Zink, Jeffrey I; Raehm, Laurence; Durand, Jean-Olivier

2018-04-01

Coherent two-photon-excited (TPE) therapy in the near-infrared (NIR) provides safer cancer treatments than current therapies lacking spatial and temporal selectivities because it is characterized by a 3D spatial resolution of 1 µm 3 and very low scattering. In this review, the principle of TPE and its significance in combination with organosilica nanoparticles (NPs) are introduced and then studies involving the design of pioneering TPE-NIR organosilica nanomaterials are discussed for bioimaging, drug delivery, and photodynamic therapy. Organosilica nanoparticles and their rich and well-established chemistry, tunable composition, porosity, size, and morphology provide ideal platforms for minimal side-effect therapies via TPE-NIR. Mesoporous silica and organosilica nanoparticles endowed with high surface areas can be functionalized to carry hydrophobic and biologically unstable two-photon absorbers for drug delivery and diagnosis. Currently, most light-actuated clinical therapeutic applications with NPs involve photodynamic therapy by singlet oxygen generation, but low photosensitizing efficiencies, tumor resistance, and lack of spatial resolution limit their applicability. On the contrary, higher photosensitizing yields, versatile therapies, and a unique spatial resolution are available with engineered two-photon-sensitive organosilica particles that selectively impact tumors while healthy tissues remain untouched. Patients suffering pathologies such as retinoblastoma, breast, and skin cancers will greatly benefit from TPE-NIR ultrasensitive diagnosis and therapy. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Graphene based widely-tunable and singly-polarized pulse generation with random fiber lasers

PubMed Central

Yao, B. C.; Rao, Y. J.; Wang, Z. N.; Wu, Y.; Zhou, J. H.; Wu, H.; Fan, M. Q.; Cao, X. L.; Zhang, W. L.; Chen, Y. F.; Li, Y. R.; Churkin, D.; Turitsyn, S.; Wong, C. W.

2015-01-01

Pulse generation often requires a stabilized cavity and its corresponding mode structure for initial phase-locking. Contrastingly, modeless cavity-free random lasers provide new possibilities for high quantum efficiency lasing that could potentially be widely tunable spectrally and temporally. Pulse generation in random lasers, however, has remained elusive since the discovery of modeless gain lasing. Here we report coherent pulse generation with modeless random lasers based on the unique polarization selectivity and broadband saturable absorption of monolayer graphene. Simultaneous temporal compression of cavity-free pulses are observed with such a polarization modulation, along with a broadly-tunable pulsewidth across two orders of magnitude down to 900 ps, a broadly-tunable repetition rate across three orders of magnitude up to 3 MHz, and a singly-polarized pulse train at 41 dB extinction ratio, about an order of magnitude larger than conventional pulsed fiber lasers. Moreover, our graphene-based pulse formation also demonstrates robust pulse-to-pulse stability and wide-wavelength operation due to the cavity-less feature. Such a graphene-based architecture not only provides a tunable pulsed random laser for fiber-optic sensing, speckle-free imaging, and laser-material processing, but also a new way for the non-random CW fiber lasers to generate widely tunable and singly-polarized pulses. PMID:26687730

Microwave tunable laser source: A stable, precision tunable heterodyne local oscillator

NASA Technical Reports Server (NTRS)

Sachse, G. W.

1980-01-01

The development and capabilities of a tunable laser source utilizing a wideband electro-optic modulator and a CO2 laser are described. The precision tunability and high stability of the device are demonstrated with examples of laboratory spectroscopy. Heterodyne measurements are also presented to demonstrate the performance of the laser source as a heterodyne local oscillator. With the use of five CO2 isotope lasers and the 8 to 18 GHz sideband offset tunability of the modulator, calculations indicate that 50 percent spectral coverage in the 9 to 12 micron region is achievable. The wavelength accuracy and stability of this laser source is limited by the CO2 laser and is more than adequate for the measurement of narrow Doppler-broadened line profiles. The room-temperature operating capability and the programmability of the microwave tunable laser source are attractive features for its in-the-field implementation. Although heterodyne measurements indicated some S/N degradation when using the device as a local oscillator, there does not appear to be any fundamental limitation to the heterodyne efficiency of this laser source. Through the use of a lower noise-figure traveling wave tube amplifier and optical matching of the output beam with the photomixer, a substantial increase in the heterodyne S/N is expected.

Graphene based widely-tunable and singly-polarized pulse generation with random fiber lasers.

PubMed

Yao, B C; Rao, Y J; Wang, Z N; Wu, Y; Zhou, J H; Wu, H; Fan, M Q; Cao, X L; Zhang, W L; Chen, Y F; Li, Y R; Churkin, D; Turitsyn, S; Wong, C W

2015-12-21

Pulse generation often requires a stabilized cavity and its corresponding mode structure for initial phase-locking. Contrastingly, modeless cavity-free random lasers provide new possibilities for high quantum efficiency lasing that could potentially be widely tunable spectrally and temporally. Pulse generation in random lasers, however, has remained elusive since the discovery of modeless gain lasing. Here we report coherent pulse generation with modeless random lasers based on the unique polarization selectivity and broadband saturable absorption of monolayer graphene. Simultaneous temporal compression of cavity-free pulses are observed with such a polarization modulation, along with a broadly-tunable pulsewidth across two orders of magnitude down to 900 ps, a broadly-tunable repetition rate across three orders of magnitude up to 3 MHz, and a singly-polarized pulse train at 41 dB extinction ratio, about an order of magnitude larger than conventional pulsed fiber lasers. Moreover, our graphene-based pulse formation also demonstrates robust pulse-to-pulse stability and wide-wavelength operation due to the cavity-less feature. Such a graphene-based architecture not only provides a tunable pulsed random laser for fiber-optic sensing, speckle-free imaging, and laser-material processing, but also a new way for the non-random CW fiber lasers to generate widely tunable and singly-polarized pulses.

Workshop Proceedings of the Conference on Solid State Tunable Lasers Held at Hampton, Virginia on 13-15 June 1984.

DTIC Science & Technology

1985-07-01

87 Trivalent Cerium Doped Crystals as Tunable Laser Systems: Two Bad Apples Douglas S. Hamilton...161 Theory of Fluorescence Quenching in Low-Field Chromium ... trivalent types of luminescent centers can be grown. Mostly high quantum efficiencies at room-temperature are observed. Pulsed room-temperature lasing

Next-generation in vivo optical imaging with short-wave infrared quantum dots.

PubMed

Bruns, Oliver T; Bischof, Thomas S; Harris, Daniel K; Franke, Daniel; Shi, Yanxiang; Riedemann, Lars; Bartelt, Alexander; Jaworski, Frank B; Carr, Jessica A; Rowlands, Christopher J; Wilson, Mark W B; Chen, Ou; Wei, He; Hwang, Gyu Weon; Montana, Daniel M; Coropceanu, Igor; Achorn, Odin B; Kloepper, Jonas; Heeren, Joerg; So, Peter T C; Fukumura, Dai; Jensen, Klavs F; Jain, Rakesh K; Bawendi, Moungi G

2017-01-01

For in vivo imaging, the short-wavelength infrared region (SWIR; 1000-2000 nm) provides several advantages over the visible and near-infrared regions: general lack of autofluorescence, low light absorption by blood and tissue, and reduced scattering. However, the lack of versatile and functional SWIR emitters has prevented the general adoption of SWIR imaging by the biomedical research community. Here, we introduce a class of high-quality SWIR-emissive indium-arsenide-based quantum dots (QDs) that are readily modifiable for various functional imaging applications, and that exhibit narrow and size-tunable emission and a dramatically higher emission quantum yield than previously described SWIR probes. To demonstrate the unprecedented combination of deep penetration, high spatial resolution, multicolor imaging and fast-acquisition-speed afforded by the SWIR QDs, we quantified, in mice, the metabolic turnover rates of lipoproteins in several organs simultaneously and in real time as well as heartbeat and breathing rates in awake and unrestrained animals, and generated detailed three-dimensional quantitative flow maps of the mouse brain vasculature.

Resonant antenna probes for tip-enhanced infrared near-field microscopy.

PubMed

Huth, Florian; Chuvilin, Andrey; Schnell, Martin; Amenabar, Iban; Krutokhvostov, Roman; Lopatin, Sergei; Hillenbrand, Rainer

2013-03-13

We report the development of infrared-resonant antenna probes for tip-enhanced optical microscopy. We employ focused-ion-beam machining to fabricate high-aspect ratio gold cones, which replace the standard tip of a commercial Si-based atomic force microscopy cantilever. Calculations show large field enhancements at the tip apex due to geometrical antenna resonances in the cones, which can be precisely tuned throughout a broad spectral range from visible to terahertz frequencies by adjusting the cone length. Spectroscopic analysis of these probes by electron energy loss spectroscopy, Fourier transform infrared spectroscopy, and Fourier transform infrared near-field spectroscopy corroborates their functionality as resonant antennas and verifies the broad tunability. By employing the novel probes in a scattering-type near-field microscope and imaging a single tobacco mosaic virus (TMV), we experimentally demonstrate high-performance mid-infrared nanoimaging of molecular absorption. Our probes offer excellent perspectives for optical nanoimaging and nanospectroscopy, pushing the detection and resolution limits in many applications, including nanoscale infrared mapping of organic, molecular, and biological materials, nanocomposites, or nanodevices.

Phase-locking to a free-space terahertz comb for metrological-grade terahertz lasers.

PubMed

Consolino, L; Taschin, A; Bartolini, P; Bartalini, S; Cancio, P; Tredicucci, A; Beere, H E; Ritchie, D A; Torre, R; Vitiello, M S; De Natale, P

2012-01-01

Optical frequency comb synthesizers have represented a revolutionary approach to frequency metrology, providing a grid of frequency references for any laser emitting within their spectral coverage. Extending the metrological features of optical frequency comb synthesizers to the terahertz domain would be a major breakthrough, due to the widespread range of accessible strategic applications and the availability of stable, high-power and widely tunable sources such as quantum cascade lasers. Here we demonstrate phase-locking of a 2.5 THz quantum cascade laser to a free-space comb, generated in a LiNbO(3) waveguide and covering the 0.1-6 THz frequency range. We show that even a small fraction (<100 nW) of the radiation emitted from the quantum cascade laser is sufficient to generate a beat note suitable for phase-locking to the comb, paving the way to novel metrological-grade terahertz applications, including high-resolution spectroscopy, manipulation of cold molecules, astronomy and telecommunications.

Compartmentalized microchannel array for high-throughput analysis of single cell polarized growth and dynamics

DOE PAGES

Geng, Tao; Bredeweg, Erin L.; Szymanski, Craig J.; ...

2015-11-04

Here, interrogating polarized growth is technologically challenging due to extensive cellular branching and uncontrollable environmental conditions in conventional assays. Here we present a robust and high-performance microfluidic system that enables observations of polarized growth with enhanced temporal and spatial control over prolonged periods. The system has built-in tunability and versatility to accommodate a variety of science applications requiring precisely controlled environments. Using the model filamentous fungus, Neurospora crassa, this microfluidic system enabled direct visualization and analysis of cellular heterogeneity in a clonal fungal cell population, nuclear distribution and dynamics at the subhyphal level, and quantitative dynamics of gene expression withmore » single hyphal compartment resolution in response to carbon source starvation and exchange experiments. Although the microfluidic device is demonstrated on filamentous fungi, our technology is immediately extensible to a wide array of other biosystems that exhibit similar polarized cell growth with applications ranging from bioenergy production to human health.« less

Back-focal-plane position detection with extended linear range for photonic force microscopy.

PubMed

Martínez, Ignacio A; Petrov, Dmitri

2012-09-01

In photonic force microscopes, the position detection with high temporal and spatial resolution is usually implemented by a quadrant position detector placed in the back focal plane of a condenser. An objective with high numerical aperture (NA) for the optical trap has also been used to focus a detection beam. In that case the displacement of the probe at a fixed position of the detector produces a unique and linear response only in a restricted region of the probe displacement, usually several hundred nanometers. There are specific experiments where the absolute position of the probe is a relevant measure together with the probe position relative the optical trap focus. In our scheme we introduce the detection beam into the condenser with low NA through a pinhole with tunable size. This combination permits us to create a wide detection spot and to achieve the linear range of several micrometers by the probe position detection without reducing the trapping force.

On the properties of synchrotron-like X-ray emission from laser wakefield accelerated electron beams

NASA Astrophysics Data System (ADS)

McGuffey, C.; Schumaker, W.; Matsuoka, T.; Chvykov, V.; Dollar, F.; Kalintchenko, G.; Kneip, S.; Najmudin, Z.; Mangles, S. P. D.; Vargas, M.; Yanovsky, V.; Maksimchuk, A.; Thomas, A. G. R.; Krushelnick, K.

2018-04-01

The electric and magnetic fields responsible for electron acceleration in a Laser Wakefield Accelerator (LWFA) also cause electrons to radiate x-ray photons. Such x-ray pulses have several desirable properties including short duration and being well collimated with tunable high energy. We measure the scaling of this x-ray source experimentally up to laser powers greater than 100 TW. An increase in laser power allows electron trapping at a lower density as well as with an increased trapped charge. These effects resulted in an x-ray fluence that was measured to increase non-linearly with laser power. The fluence of x-rays was also compared with that produced from K-α emission resulting from a solid target interaction for the same energy laser pulse. The flux was shown to be comparable, but the LWFA x-rays had a significantly smaller source size. This indicates that such a source may be useful as a backlighter for probing high energy density plasmas with ultrafast temporal resolution.

Low-loss microelectrodes fabricated using reverse-side exposure for a tunable ferroelectric capacitor application

NASA Astrophysics Data System (ADS)

Yoon, Yong-Kyu; Stevenson Kenney, J.; Hunt, Andrew T.; Allen, Mark G.

2006-02-01

Narrowly spaced thick microelectrodes are fabricated using a self-aligned multiple reverse-side exposure scheme for an improved quality-factor tunable ferroelectric capacitor. The microelectrodes are fabricated on a functional substrate—a thin film ferroelectric (barium strontium titanate, BST; BaxSr1-xTiO3) coated sapphire substrate, which has an electric-field-dependent dielectric property providing tuning functionality, as well as UV transparency permitting an additional degree of freedom in photolithography steps. The microelectrode process has been applied to interdigitated capacitor fabrication, where a critical challenge is maintaining narrow gaps between electrodes for high tunability, while simultaneously forming thick electrodes to minimize conductor loss. A single mask, self-aligned reverse-side exposure through the transparent substrate achieves both these goals. A single-finger test capacitor with an electrode gap of 1.2 µm and an electrode thickness of 2.2 µm is fabricated and characterized. Tunability (T = 100 × (C0 - Cbias)/C0) of 33% at 10 V has been achieved at 100 kHz. The 2.2 µm thick structure shows improvement of Q-factor compared to that of a 0.1 µm thick structure. To demonstrate the scalability of this process, a 102-finger interdigitated capacitor is fabricated and characterized at 100 kHz and 1 GHz. The structure is embedded in a 25 µm thick epoxy resin SU-8 for passivation. A quality factor decrease of 15-25%, tunability decrease of 2-3% and capacitance increase of 6% are observed due to the expoxy resin after passivation. High frequency performance of the capacitor has been measured to be 15.9 pF of capacitance, 28.1% tunability at 10 V and a quality factor of 16 (at a 10 V dc bias) at 1 GHz.

Chemically Responsive Elastomers Exhibiting Unity-Order Refractive Index Modulation.

PubMed

Wu, Di M; Solomon, Michelle L; Naik, Gururaj V; García-Etxarri, Aitzol; Lawrence, Mark; Salleo, Alberto; Dionne, Jennifer A

2018-02-01

Chameleons are masters of light, expertly changing their color, pattern, and reflectivity in response to their environment. Engineered materials that share this tunability can be transformative, enabling active camouflage, tunable holograms, and novel colorimetric medical sensors. While progress has been made in creating artificial chameleon skin, existing schemes often require external power, are not continuously tunable, and may prove too stiff or bulky for applications. Here, a chemically tunable, large-area metamaterial is demonstrated that accesses a wide range of colors and refractive indices. An ordered monolayer of nanoresonators is fabricated, then its optical response is dynamically tuned by infiltrating its polymer substrate with solvents. The material shows a strong magnetic response with a dependence on resonator spacing that leads to a highly tunable effective permittivity, permeability, and refractive index spanning negative and positive values. The unity-order index tuning exceeds that of traditional electro-optic and photochromic materials and is robust to cycling, providing a path toward programmable optical elements and responsive light routing. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Generation of narrowband, high-intensity, carrier-envelope phase-stable pulses tunable between 4 and 18  THz.

PubMed

Liu, B; Bromberger, H; Cartella, A; Gebert, T; Först, M; Cavalleri, A

2017-01-01

We report on the generation of high-energy (1.9 μJ) far-infrared pulses tunable between 4 and 18 THz frequency. Emphasis is placed on tunability and on minimizing the bandwidth of these pulses to less than 1 THz, as achieved by difference-frequency mixing of two linearly chirped near-infrared pulses in the organic nonlinear crystal DSTMS. As the two near-infrared pulses are derived from amplification of the same white light continuum, their carrier envelope phase fluctuations are mutually correlated, and hence the difference-frequency THz field exhibits absolute phase stability. This source opens up new possibilities for the control of condensed matter and chemical systems by selective excitation of low-energy modes in a frequency range that has, to date, been difficult to access.

Observation of Fermi arcs in the type-II Weyl semimetal candidate WTe 2

DOE PAGES

Wu, Yun; Mou, Daixiang; Jo, Na Hyun; ...

2016-09-14

We use ultrahigh resolution, tunable, vacuum ultraviolet laser angle-resolved photoemission spectroscopy (ARPES) to study the electronic properties of WTe 2, a material that was predicted to be a type-II Weyl semimetal. The Weyl fermion states in WTe 2 were proposed to emerge at the crossing points of electron and hole pockets, and Fermi arcs connecting electron and hole pockets would be visible in the spectral function on (001) surface. Here we report the observation of such Fermi arcs in WTe 2 confirming the theoretical predictions. This provides strong evidence for type-II Weyl semimetallic states in WTe 2. Here, we alsomore » find that trivial and topological domains coexist on the same surface of the sample due to the presence of inhomogeneous strain detected by scanning electron microscopy data. This is in agreement with the theoretical prediction that strain can drive this system from topological Weyl to trivial semimetal. WTe 2 therefore provides a tunable playground for studying exotic topological quantum effects.« less

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

Experimental demonstration of the real-time online fault monitoring technique for chaos-based passive optical networks

NASA Astrophysics Data System (ADS)

Dou, Xinyu; Yin, Hongxi; Yue, Hehe; Jin, Yu; Shen, Jing; Li, Lin

2015-09-01

In this paper, a real-time online fault monitoring technique for chaos-based passive optical networks (PONs) is proposed and experimentally demonstrated. The fault monitoring is performed by the chaotic communication signal. The proof-of-concept experiments are demonstrated for two PON structures, i.e., wavelength-division-multiplexing (WDM) PON and Ethernet PON (EPON), respectively. For WDM PON, two monitoring approaches are investigated, one deploying a chaotic optical time domain reflectometry (OTDR) for each transmitter, and the other using only one tunable chaotic OTDR. The experimental results show that the faults at beyond 20 km from the OLT can be detected and located. The spatial resolution of the tunable chaotic OTDR is an order of magnitude of centimeter. Meanwhile, the monitoring process can operate in parallel with the chaotic optical secure communications. The proposed technique has benefits of real-time, online, precise fault location, and simple realization, which will significantly reduce the cost of operation, administration and maintenance (OAM) of PON.

Observation of Fermi arcs in the type-II Weyl semimetal candidate WTe 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Yun; Mou, Daixiang; Jo, Na Hyun

We use ultrahigh resolution, tunable, vacuum ultraviolet laser angle-resolved photoemission spectroscopy (ARPES) to study the electronic properties of WTe 2, a material that was predicted to be a type-II Weyl semimetal. The Weyl fermion states in WTe 2 were proposed to emerge at the crossing points of electron and hole pockets, and Fermi arcs connecting electron and hole pockets would be visible in the spectral function on (001) surface. Here we report the observation of such Fermi arcs in WTe 2 confirming the theoretical predictions. This provides strong evidence for type-II Weyl semimetallic states in WTe 2. Here, we alsomore » find that trivial and topological domains coexist on the same surface of the sample due to the presence of inhomogeneous strain detected by scanning electron microscopy data. This is in agreement with the theoretical prediction that strain can drive this system from topological Weyl to trivial semimetal. WTe 2 therefore provides a tunable playground for studying exotic topological quantum effects.« less

Compact and tunable focusing device for plasma wakefield acceleration

NASA Astrophysics Data System (ADS)

Pompili, R.; Anania, M. P.; Chiadroni, E.; Cianchi, A.; Ferrario, M.; Lollo, V.; Notargiacomo, A.; Picardi, L.; Ronsivalle, C.; Rosenzweig, J. B.; Shpakov, V.; Vannozzi, A.

2018-03-01

Plasma wakefield acceleration, either driven by ultra-short laser pulses or electron bunches, represents one of the most promising techniques able to overcome the limits of conventional RF technology and allows the development of compact accelerators. In the particle beam-driven scenario, ultra-short bunches with tiny spot sizes are required to enhance the accelerating gradient and preserve the emittance and energy spread of the accelerated bunch. To achieve such tight transverse beam sizes, a focusing system with short focal length is mandatory. Here we discuss the development of a compact and tunable system consisting of three small-bore permanent-magnet quadrupoles with 520 T/m field gradient. The device has been designed in view of the plasma acceleration experiments planned at the SPARC_LAB test-facility. Being the field gradient fixed, the focusing is adjusted by tuning the relative position of the three magnets with nanometer resolution. Details about its magnetic design, beam-dynamics simulations, and preliminary results are examined in the paper.

Spectroscopic Studies of Laser Produced Plasma Metasurfaces

NASA Astrophysics Data System (ADS)

Colon Quinones, Roberto; Underwood, Thomas; Cappelli, Mark

2016-10-01

In this presentation, we describe the spatial and temporal plasma characteristics of the dense plasma kernels that are used to construct a laser produced plasma metasurface (PM) that is intended to serve as a tunable THz reflector. The PM is an n x n array of plasmas generated by focusing the light from a 2 J/p Q-switched Nd:YAG laser through a multi-lens array (MLA) and into a gas of varying pressure. A gated CCD camera coupled to a high-resolution spectrometer is used to obtain chord-averaged H α broadening data for the cross section of a single plasma element at the lens focal point. The data is then Abel inverted to derive the radial plasma density distribution. Measurements are repeated for a range of pressures, laser energies, and lens f-number, with a time resolution of 100 ns and a gate width of 20 ns. Results are presented for the variation of plasma density and size over these different conditions. Work supported by the Air Force Office of Scientific Research (AFOSR). R. Colon Quinones and T. Underwood acknowledge the support of the Department of Defense (DoD) through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program.

Observations of the planetary nebula RWT 152 with OSIRIS/GTC

NASA Astrophysics Data System (ADS)

Aller, A.; Miranda, L. F.; Olguín, L.; Solano, E.; Ulla, A.

2016-11-01

RWT 152 is one of the few known planetary nebulae with an sdO central star. We present subarcsecond red tunable filter Hα imaging and intermediate-resolution, long-slit spectroscopy of RWT 152 obtained with OSIRIS/GTC (Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy/Gran Telescopio Canarias) with the goal of analysing its properties. The Hα image reveals a bipolar nebula with a bright equatorial region and multiple bubbles in the main lobes. A faint circular halo surrounds the main nebula. The nebular spectra reveal a very low excitation nebula with weak emission lines from H+, He+ and double-ionized metals, and absence of emission lines from neutral and single-ionized metals, except for an extremely faint [N II] λ6584 emission line. These spectra may be explained if RWT 152 is a density-bounded planetary nebula. Low nebular chemical abundances of S, O, Ar, N and Ne are obtained in RWT 152, which, together with the derived high peculiar velocity (˜ 92-131 km s-1), indicate that this object is a halo planetary nebula. The available data are consistent with RWT 152 evolving from a low-mass progenitor (˜1 M⊙) formed in a metal-poor environment.

Plasmon-Assisted Selective and Super-Resolving Excitation of Individual Quantum Emitters on a Metal Nanowire.

PubMed

Li, Qiang; Pan, Deng; Wei, Hong; Xu, Hongxing

2018-03-14

Hybrid systems composed of multiple quantum emitters coupled with plasmonic waveguides are promising building blocks for future integrated quantum nanophotonic circuits. The techniques that can super-resolve and selectively excite contiguous quantum emitters in a diffraction-limited area are of great importance for studying the plasmon-mediated interaction between quantum emitters and manipulating the single plasmon generation and propagation in plasmonic circuits. Here we show that multiple quantum dots coupled with a silver nanowire can be controllably excited by tuning the interference field of surface plasmons on the nanowire. Because of the period of the interference pattern is much smaller than the diffraction limit, we demonstrate the selective excitation of two quantum dots separated by a distance as short as 100 nm. We also numerically demonstrate a new kind of super-resolution imaging method that combines the tunable surface plasmon interference pattern on the NW with the structured illumination microscopy technique. Our work provides a novel high-resolution optical excitation and imaging method for the coupled systems of multiple quantum emitters and plasmonic waveguides, which adds a new tool for studying and manipulating single quantum emitters and single plasmons for quantum plasmonic circuitry applications.

Coherent cavity-enhanced dual-comb spectroscopy

PubMed Central

Fleisher, Adam J.; Long, David A.; Reed, Zachary D.; Hodges, Joseph T.; Plusquellic, David F.

2016-01-01

Dual-comb spectroscopy allows for the rapid, multiplexed acquisition of high-resolution spectra without the need for moving parts or low-resolution dispersive optics. This method of broadband spectroscopy is most often accomplished via tight phase locking of two mode-locked lasers or via sophisticated signal processing algorithms, and therefore, long integration times of phase coherent signals are difficult to achieve. Here we demonstrate an alternative approach to dual-comb spectroscopy using two phase modulator combs originating from a single continuous-wave laser capable of > 2 hours of coherent real-time averaging. The dual combs were generated by driving the phase modulators with step-recovery diodes where each comb consisted of > 250 teeth with 203 MHz spacing and spanned > 50 GHz region in the near-infrared. The step-recovery diodes are passive devices that provide low-phase-noise harmonics for efficient coupling into an enhancement cavity at picowatt optical powers. With this approach, we demonstrate the sensitivity to simultaneously monitor ambient levels of CO2, CO, HDO, and H2O in a single spectral region at a maximum acquisition rate of 150 kHz. Robust, compact, low-cost and widely tunable dual-comb systems could enable a network of distributed multiplexed optical sensors. PMID:27409866

Compact high-resolution echelle-AOTF NIR spectrometer for atmospheric measurements

NASA Astrophysics Data System (ADS)

Korablev, Oleg I.; Bertaux, Jean-Loup; Vinogradov, Imant I.; Kalinnikov, Yurii K.; Nevejans, D.; Neefs, E.; Le Barbu, T.; Durry, G.

2017-11-01

A new concept of a high-resolution near-IR spectrometer consisting of an echelle grating combined with an acousto-optic tunable filter (AOTF) for separation of diffraction orders, is developed for space-borne studies of planetary atmospheres. A compact design with no moving parts within the mass budget of 3-5 kg allows to reach the resolving power λ/Δλ of 20000-30000. Only a small piece of spectrum in high diffraction orders can be measured at a time, but thanks to flexibility of the AOTF electrical tuning, such pieces of spectrum can be measured randomly and rapidly within the spectral range. This development can be used for accurate measurements of important atmospheric gases, such as CO2 in terrestrial atmosphere, isotopic ratios and minor gases. A spectrometer, based on this principle, SOIR (Solar Occultation InfraRed) is being built for Venus Express (2005) ESA mission. Instruments based on this principle have high potential for the studies of the Earth, in particular for measurements of isotopes of water in the lower atmosphere, either in solar occultation profiling (tangent altitude <10 km), or observing solar glint for integral quantities of the components. Small size of hardware makes them ideal for micro-satellites, which are now agile enough to provide necessary pointing for solar occultation or glint observations. Also, the atmosphere of Mars has never been observed at local scales with such a high spectral resolution. A laboratory prototype consisting of 275-mm echelle spectrometer with Hamamatsu InGaAs 512-pixel linear array and the AOTF has demonstrated λ/Δλ≍30000 in the spectral range of 1-1.7 μm. The next set up, covering the spectral ranges of 1-1.7 μm and 2.3-4.3 μm, and the Venus Express SOIR are briefly discussed.

Nanostructure and strain effects in active thin films for novel electronic device applications

NASA Astrophysics Data System (ADS)

Yuan, Zheng

2007-12-01

There are many potential applications of ferroelectric thin films that take advantage of their unique dielectric and piezoelectric properties, such as tunable microwave devices and thin-film active sensors for structural health monitoring (SHM). However, many technical issues still restrict practical applications of ferroelectric thin films, including high insertion loss, limited figure of merit, soft mode effect, large temperature coefficients, and others. The main theme of this thesis is the advanced technique developments, and the new ferroelectric thin films syntheses and investigations for novel device applications. A novel method of additional doping has been adopted to (Ba,Sr)TiO 3 (BSTO) thin films on MgO. By introducing 2% Mn into the stoichiometric BSTO, Mn:BSTO thin films have shown a greatly enhanced dielectric tunability and a reduced insertion loss at high frequencies (10-30 GHz). A new record of a large tunability of 80% with a high dielectric constant of 3800 and an extra low dielectric loss of 0.001 at 1 MHz at room-temperature was achieved. Meanwhile, the new highly epitaxial ferroelectric (Pb,Sr)TiO3 (PSTO) thin films have been synthesized on (001) MgO substrates. PSTO films demonstrated excellent high frequency dielectric properties with high dielectric constants above 1420 and large dielectric tunabilities above 34% at room-temperature up to 20 GHz. In addition, a smaller temperature coefficient from 80 K to 300 K was observed in PSTO films compared to BSTO films. These results indicate that the Mn:BSTO and PSTO films are both good candidates for developing room-temperature tunable microwave devices. Furthermore, crystalline ferroelectric BaTiO3 (BTO) thin films have been deposited directly on metal substrate Ni through a unique in-situ substrate pre-oxidation treatment. The highly oriented nanopillar structural BTO films were grown on the buffered layers created by the pre-oxidation treatment. No interdiffusion or reaction was observed at the interface. As-grown BTO films demonstrated good ferroelectric properties and an extremely large piezoelectric response of 130 (x 10-12 C/N). These excellent preliminary results enable the long-term perspective on the unobtrusive ferroelectric thin-film active sensors for SHM applications.

Direct Observations of Reaction Zone Structure in Propagating Detonations

DTIC Science & Technology

2003-02-08

with sufficient spatial resolution and signal-to-noise ratio were achieved by using a tunable KrF laser with a pulse energy of 450 mJ exciting the OH...self-sustaining waves within the test section. The detonation reaction zone has been visualized by exciting OH fluorescence at about 284 nm with a...in some tests. The UV light for excitation of the OH molecules is produced by frequency dou- bling the output of an excimer-pumped dye laser. The

Bibliography of Soviet Laser Developments, Number 72, July - August 1984.

DTIC Science & Technology

1985-11-01

no. 2, 1984, 319-324. 131. ?4irza, S.Yu.; Soldatov, A.N.; Sukhanov , V.B.; . Troitskiy, V.0. C).Spatial structure of radiation 4 from a copper vapor...Soldatov, A.N.; Sukhanov , V.B. (. Current status in the development of metal vapor lasers and their use for pumping tunable lasers. CRNTShSL. Materialy...orthoscopic images of the same resolution in one hologram by rainbow holography. OPAPB, no. 3, 1983, 307-311. (RZFZA, 84/8L661). 641. Sukhanov , V.I

Flexible and tunable terahertz all-dielectric metasurface composed of ceramic spheres embedded in ferroelectric/ elastomer composite.

PubMed

Lan, Chuwen; Zhu, Di; Gao, Jiannan; Li, Bo; Gao, Zehua

2018-04-30

Terahertz (THz) all-dielectric metasurfaces made of high-index and low-loss resonators have attracted more and more attention due to their versatile properties. However, the all-dielectric metasurfaces in THz suffer from limited bandwidth and low tunability. Meanwhile, they are usually fabricated on flat and rigid substrates, and consequently their applications are restricted. Here, a simple approach is proposed and experimentally demonstrated to obtain a flexible and tunable THz all-dielectric metasurface. In this metasurface, micro ceramic spheres (ZrO 2 ) are embedded in a ferroelectric (strontium titanate) / elastomer (polydimethylsiloxane) composite. It is shown that the Mie resonances in micro ceramic spheres can be thermally and reversibly tuned resulting from the temperature dependent permittivity of the ferroelectric / PDMS composite. This metasurface characterized by flexibility and tunability is expected to have a more extensive application in active THz devices.

Tunable Microfluidic Devices for Hydrodynamic Fractionation of Cells and Beads: A Review

PubMed Central

Alvankarian, Jafar; Majlis, Burhanuddin Yeop

2015-01-01

The adjustable microfluidic devices that have been developed for hydrodynamic-based fractionation of beads and cells are important for fast performance tunability through interaction of mechanical properties of particles in fluid flow and mechanically flexible microstructures. In this review, the research works reported on fabrication and testing of the tunable elastomeric microfluidic devices for applications such as separation, filtration, isolation, and trapping of single or bulk of microbeads or cells are discussed. Such microfluidic systems for rapid performance alteration are classified in two groups of bulk deformation of microdevices using external mechanical forces, and local deformation of microstructures using flexible membrane by pneumatic pressure. The main advantage of membrane-based tunable systems has been addressed to be the high capability of integration with other microdevice components. The stretchable devices based on bulk deformation of microstructures have in common advantage of simplicity in design and fabrication process. PMID:26610519

Progress in Cherenkov femtosecond fiber lasers

PubMed Central

Liu, Xiaomin; Svane, Ask S.; Lægsgaard, Jesper; Tu, Haohua; Boppart, Stephen A.; Turchinovich, Dmitry

2016-01-01

We review the recent developments in the field of ultrafast Cherenkov fiber lasers. Two essential properties of such laser systems – broad wavelength tunability and high efficiency of Cherenkov radiation wavelength conversion are discussed. The exceptional performance of the Cherenkov fiber laser systems are highlighted - dependent on the realization scheme, the Cherenkov lasers can generate the femtosecond output tunable across the entire visible and even the UV range, and for certain designs more than 40 % conversion efficiency from the pump to Cherenkov signal can be achieved. The femtosecond Cherenkov laser with all-fiber architecture is presented and discussed. Operating in the visible range, it delivers 100–200 fs wavelength-tunable pulses with multimilliwatt output power and exceptionally low noise figure an order of magnitude lower than the traditional wavelength tunable supercontinuum-based femtosecond sources. The applications for Cherenkov laser systems in practical biophotonics and biomedical applications, such as bio-imaging and microscopy, are discussed. PMID:27110037

Trap-mediated electronic transport properties of gate-tunable pentacene/MoS2 p-n heterojunction diodes

PubMed Central

Kim, Jae-Keun; Cho, Kyungjune; Kim, Tae-Young; Pak, Jinsu; Jang, Jingon; Song, Younggul; Kim, Youngrok; Choi, Barbara Yuri; Chung, Seungjun; Hong, Woong-Ki; Lee, Takhee

2016-01-01

We investigated the trap-mediated electronic transport properties of pentacene/molybdenum disulphide (MoS2) p-n heterojunction devices. We observed that the hybrid p-n heterojunctions were gate-tunable and were strongly affected by trap-assisted tunnelling through the van der Waals gap at the heterojunction interfaces between MoS2 and pentacene. The pentacene/MoS2 p-n heterojunction diodes had gate-tunable high ideality factor, which resulted from trap-mediated conduction nature of devices. From the temperature-variable current-voltage measurement, a space-charge-limited conduction and a variable range hopping conduction at a low temperature were suggested as the gate-tunable charge transport characteristics of these hybrid p-n heterojunctions. Our study provides a better understanding of the trap-mediated electronic transport properties in organic/2-dimensional material hybrid heterojunction devices. PMID:27829663

Generation of a tunable environment for electrical oscillator systems.

PubMed

León-Montiel, R de J; Svozilík, J; Torres, Juan P

2014-07-01

Many physical, chemical, and biological systems can be modeled by means of random-frequency harmonic oscillator systems. Even though the noise-free evolution of harmonic oscillator systems can be easily implemented, the way to experimentally introduce, and control, noise effects due to a surrounding environment remains a subject of lively interest. Here, we experimentally demonstrate a setup that provides a unique tool to generate a fully tunable environment for classical electrical oscillator systems. We illustrate the operation of the setup by implementing the case of a damped random-frequency harmonic oscillator. The high degree of tunability and control of our scheme is demonstrated by gradually modifying the statistics of the oscillator's frequency fluctuations. This tunable system can readily be used to experimentally study interesting noise effects, such as noise-induced transitions in systems driven by multiplicative noise, and noise-induced transport, a phenomenon that takes place in quantum and classical coupled oscillator networks.

A tunable acoustic metamaterial with double-negativity driven by electromagnets

PubMed Central

Chen, Zhe; Xue, Cheng; Fan, Li; Zhang, Shu-yi; Li, Xiao-juan; Zhang, Hui; Ding, Jin

2016-01-01

With the advance of the research on acoustic metamaterials, the limits of passive metamaterials have been observed, which prompts the studies concerning actively tunable metamaterials with adjustable characteristic frequency bands. In this work, we present a tunable acoustic metamaterial with double-negativity composed of periodical membranes and side holes, in which the double-negativity pass band can be controlled by an external direct-current voltage. The tension and stiffness of the periodically arranged membranes are actively controlled by electromagnets producing additional stresses, and thus, the transmission and phase velocity of the metamaterial can be adjusted by the driving voltage of the electromagnets. It is demonstrated that a tiny direct-current voltage of 6V can arise a shift of double-negativity pass band by 40% bandwidth, which exhibits that it is an easily controlled and highly tunable acoustic metamaterial, and furthermore, the metamaterial marginally causes electromagnetic interference to the surroundings. PMID:27443196

Trap-mediated electronic transport properties of gate-tunable pentacene/MoS2 p-n heterojunction diodes

NASA Astrophysics Data System (ADS)

Kim, Jae-Keun; Cho, Kyungjune; Kim, Tae-Young; Pak, Jinsu; Jang, Jingon; Song, Younggul; Kim, Youngrok; Choi, Barbara Yuri; Chung, Seungjun; Hong, Woong-Ki; Lee, Takhee

2016-11-01

We investigated the trap-mediated electronic transport properties of pentacene/molybdenum disulphide (MoS2) p-n heterojunction devices. We observed that the hybrid p-n heterojunctions were gate-tunable and were strongly affected by trap-assisted tunnelling through the van der Waals gap at the heterojunction interfaces between MoS2 and pentacene. The pentacene/MoS2 p-n heterojunction diodes had gate-tunable high ideality factor, which resulted from trap-mediated conduction nature of devices. From the temperature-variable current-voltage measurement, a space-charge-limited conduction and a variable range hopping conduction at a low temperature were suggested as the gate-tunable charge transport characteristics of these hybrid p-n heterojunctions. Our study provides a better understanding of the trap-mediated electronic transport properties in organic/2-dimensional material hybrid heterojunction devices.

Trap-mediated electronic transport properties of gate-tunable pentacene/MoS2 p-n heterojunction diodes.

PubMed

Kim, Jae-Keun; Cho, Kyungjune; Kim, Tae-Young; Pak, Jinsu; Jang, Jingon; Song, Younggul; Kim, Youngrok; Choi, Barbara Yuri; Chung, Seungjun; Hong, Woong-Ki; Lee, Takhee

2016-11-10

We investigated the trap-mediated electronic transport properties of pentacene/molybdenum disulphide (MoS 2 ) p-n heterojunction devices. We observed that the hybrid p-n heterojunctions were gate-tunable and were strongly affected by trap-assisted tunnelling through the van der Waals gap at the heterojunction interfaces between MoS 2 and pentacene. The pentacene/MoS 2 p-n heterojunction diodes had gate-tunable high ideality factor, which resulted from trap-mediated conduction nature of devices. From the temperature-variable current-voltage measurement, a space-charge-limited conduction and a variable range hopping conduction at a low temperature were suggested as the gate-tunable charge transport characteristics of these hybrid p-n heterojunctions. Our study provides a better understanding of the trap-mediated electronic transport properties in organic/2-dimensional material hybrid heterojunction devices.

Progress in Cherenkov femtosecond fiber lasers.

PubMed

Liu, Xiaomin; Svane, Ask S; Lægsgaard, Jesper; Tu, Haohua; Boppart, Stephen A; Turchinovich, Dmitry

2016-01-20

We review the recent developments in the field of ultrafast Cherenkov fiber lasers. Two essential properties of such laser systems - broad wavelength tunability and high efficiency of Cherenkov radiation wavelength conversion are discussed. The exceptional performance of the Cherenkov fiber laser systems are highlighted - dependent on the realization scheme, the Cherenkov lasers can generate the femtosecond output tunable across the entire visible and even the UV range, and for certain designs more than 40 % conversion efficiency from the pump to Cherenkov signal can be achieved. The femtosecond Cherenkov laser with all-fiber architecture is presented and discussed. Operating in the visible range, it delivers 100-200 fs wavelength-tunable pulses with multimilliwatt output power and exceptionally low noise figure an order of magnitude lower than the traditional wavelength tunable supercontinuum-based femtosecond sources. The applications for Cherenkov laser systems in practical biophotonics and biomedical applications, such as bio-imaging and microscopy, are discussed.

Stimulated polariton scattering in an intracavity RbTiOPO₄ crystal generating frequency-tunable THz output.

PubMed

Ortega, Tiago A; Pask, Helen M; Spence, David J; Lee, Andrew J

2016-05-16

A high power, frequency-tunable THz source based on intracavity stimulated polariton scattering (SPS) in RbTiOPO₄ (RTP) is demonstrated for the first time. Frequency tunable THz output was obtained from 3.10 to 4.15 THz, with a gap at 3.17 to 3.49 THz, arising from the 104 cm^-1 A₁ mode in RTP. A maximum average output power of 16.2 µW was detected at 3.8 THz. This is the highest average output power ever reported for an intracavity polariton laser.

Strain engineered barium strontium titanate for tunable thin film resonators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khassaf, H.; Khakpash, N.; Sun, F.

2014-05-19

Piezoelectric properties of epitaxial (001) barium strontium titanate (BST) films are computed as functions of composition, misfit strain, and temperature using a non-linear thermodynamic model. Results show that through adjusting in-plane strains, a highly adaptive rhombohedral ferroelectric phase can be stabilized at room temperature with outstanding piezoelectric response exceeding those of lead based piezoceramics. Furthermore, by adjusting the composition and the in-plane misfit, an electrically tunable piezoelectric response can be obtained in the paraelectric state. These findings indicate that strain engineered BST films can be utilized in the development of electrically tunable and switchable surface and bulk acoustic wave resonators.

Laser-induced fluorescence microscopic system using an optical parametric oscillator for tunable detection in microchip analysis.

PubMed

Kumemura, Momoko; Odake, Tamao; Korenaga, Takashi

2005-06-01

A laser-induced fluorescence microscopic system based on optical parametric oscillation has been constructed as a tunable detector for microchip analysis. The detection limit of sulforhodamine B (Ex. 520 nm, Em. 570 nm) was 0.2 mumol, which was approximately eight orders of magnitude better than with a conventional fluorophotometer. The system was applied to the determination of fluorescence-labeled DNA (Ex. 494 nm, Em. 519 nm) in a microchannel and the detection limit reached a single molecule. These results showed the feasibility of this system as a highly sensitive and tunable fluorescence detector for microchip analysis.

Highly tunable birefringent microstructured optical fiber.

PubMed

Kerbage, C; Steinvurzel, P; Reyes, P; Westbrook, P S; Windeler, R S; Hale, A; Eggleton, B J

2002-05-15

We demonstrate a method for introducing and dynamically tuning birefringence in a microstructured optical fiber. Waveguide asymmetry in the fiber is obtained by selective filling of air holes with polymer, and tunability is achieved by temperature tuning of the polymer's index. The fiber is tapered such that the mode field expands into the cladding and efficiently overlaps the polymer that has been infused into the air holes, ensuring enhanced tunability and low splice loss. Experimental results are compared with numerical simulations made with the beam propagation method and confirm birefringence tuning that corresponds to a phase change of 6pi for a 1-cm length of fiber.

Highly Tunable Hollow Gold Nanospheres: Gaining Size Control and Uniform Galvanic Exchange of Sacrificial Cobalt Boride Scaffolds.

PubMed

Lindley, Sarah A; Cooper, Jason K; Rojas-Andrade, Mauricio D; Fung, Victoria; Leahy, Conor J; Chen, Shaowei; Zhang, Jin Z

2018-04-18

In principle, the diameter and surface plasmon resonance (SPR) frequency of hollow metal nanostructures can be independently adjusted, allowing the formation of targeted photoactivated structures of specific size and optical functionality. Although tunable SPRs have been reported for various systems, the shift in SPR is usually concomitant with a change in particle size. As such, more advanced tunability, including constant diameter with varying SPR or constant SPR with varying diameter, has not been properly achieved experimentally. Herein, we demonstrate this advanced tunability with hollow gold nanospheres (HGNs). HGNs were synthesized through galvanic exchange using cobalt-based nanoparticles (NPs) as sacrificial scaffolds. Co 2 B NP scaffolds were prepared by sodium borohydride nucleation of aqueous cobalt chloride and characterized using UV-vis, dynamic light scattering, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy. Careful control over the size of the Co 2 B scaffold and its galvanic conversion is essential to realize fine control of the resultant HGN diameter and shell thickness. In pursuit of size control, we introduce B(OH) 4 - (the final product of NaBH 4 hydrolysis) as a growth agent to obtain hydrodynamic diameters ranging from ∼17-85 nm with relative standard deviation <3%. The highly monodisperse Co 2 B NPs were then used as scaffolds for the formation of HGNs. In controlling HGN shell thickness and uniformity, environmental oxygen was shown to affect both the structural and optical properties of the resultant gold shells. With careful control of these key factors, we demonstrate an HGN synthesis that enables independent variation of diameter and shell thickness, and thereby SPR, with unprecedented uniformity. The new synthesis method creates a truly tunable plasmonic nanostructure platform highly desirable for a wide range of applications, including sensing, catalysis, and photothermal therapy.

Tunable infrared hyperbolic metamaterials with periodic indium-tin-oxide nanorods

DOE PAGES

Guo, Peijun; Chang, Robert P. H.; Schaller, Richard D.

2017-07-10

Hyperbolic metamaterials (HMMs) are artificially engineered optical media that have been used for light confinement, excited state decay rate engineering, and subwavelength imaging, due to their highly anisotropic permittivity and with it the capability of supporting high- k modes. HMMs in the infrared range can be conceived for additional applications such as free space communication, thermal engineering, and molecular sensing. Here, we demonstrate infrared HMMs comprised of periodic indium-tin-oxide nanorod arrays (ITO-NRAs). We show that the ITO-NRA based HMMs exhibit a stationary epsilon-near-pole resonance in the near-infrared regime that is insensitive to the filling ratio, and a highly tunable epsilon-near-zeromore » resonance in the mid-infrared range depending on the array periodicity. Experimental results are supported by finite-element simulations, in which the ITO-NRAs are treated both explicitly and as an effective hyperbolic media. Lastly, our work presents a low-loss HMM platform with favorable spectral tunability in the infrared range.« less

Graphene-Based Flexible and Transparent Tunable Capacitors.

PubMed

Man, Baoyuan; Xu, Shicai; Jiang, Shouzheng; Liu, Aihua; Gao, Shoubao; Zhang, Chao; Qiu, Hengwei; Li, Zhen

2015-12-01

We report a kind of electric field tunable transparent and flexible capacitor with the structure of graphene-Bi1.5MgNb1.5O7 (BMN)-graphene. The graphene films with low sheet resistance were grown by chemical vapor deposition. The BMN thin films were fabricated on graphene by using laser molecular beam epitaxy technology. Compared to BMN films grown on Au, the samples on graphene substrates show better quality in terms of crystallinity, surface morphology, leakage current, and loss tangent. By transferring another graphene layer, we fabricated flexible and transparent capacitors with the structure of graphene-BMN-graphene. The capacitors show a large dielectric constant of 113 with high dielectric tunability of ~40.7 % at a bias field of 1.0 MV/cm. Also, the capacitor can work stably in the high bending condition with curvature radii as low as 10 mm. This flexible film capacitor has a high optical transparency of ~90 % in the visible light region, demonstrating their potential application for a wide range of flexible electronic devices.

Tunable High-Intensity Electron Bunch Train Production Based on Nonlinear Longitudinal Space Charge Oscillation

NASA Astrophysics Data System (ADS)

Zhang, Zhen; Yan, Lixin; Du, Yingchao; Zhou, Zheng; Su, Xiaolu; Zheng, Lianmin; Wang, Dong; Tian, Qili; Wang, Wei; Shi, Jiaru; Chen, Huaibi; Huang, Wenhui; Gai, Wei; Tang, Chuanxiang

2016-05-01

High-intensity trains of electron bunches with tunable picosecond spacing are produced and measured experimentally with the goal of generating terahertz (THz) radiation. By imposing an initial density modulation on a relativistic electron beam and controlling the charge density over the beam propagation, density spikes of several-hundred-ampere peak current in the temporal profile, which are several times higher than the initial amplitudes, have been observed for the first time. We also demonstrate that the periodic spacing of the bunch train can be varied continuously either by tuning launching phase of a radio-frequency gun or by tuning the compression of a downstream magnetic chicane. Narrow-band coherent THz radiation from the bunch train was also measured with μ J -level energies and tunable central frequency of the spectrum in the range of ˜0.5 to 1.6 THz. Our results pave the way towards generating mJ-level narrow-band coherent THz radiation and driving high-gradient wakefield-based acceleration.

Carbon-bridged oligo(p-phenylenevinylene)s for photostable and broadly tunable, solution-processable thin film organic lasers

PubMed Central

Morales-Vidal, Marta; Boj, Pedro G.; Villalvilla, José M.; Quintana, José A.; Yan, Qifan; Lin, Nai-Ti; Zhu, Xiaozhang; Ruangsupapichat, Nopporn; Casado, Juan; Tsuji, Hayato; Nakamura, Eiichi; Díaz-García, María A.

2015-01-01

Thin film organic lasers represent a new generation of inexpensive, mechanically flexible devices for spectroscopy, optical communications and sensing. For this purpose, it is desired to develop highly efficient, stable, wavelength-tunable and solution-processable organic laser materials. Here we report that carbon-bridged oligo(p-phenylenevinylene)s serve as optimal materials combining all these properties simultaneously at the level required for applications by demonstrating amplified spontaneous emission and distributed feedback laser devices. A series of six compounds, with the repeating unit from 1 to 6, doped into polystyrene films undergo amplified spontaneous emission from 385 to 585 nm with remarkably low threshold and high net gain coefficients, as well as high photostability. The fabricated lasers show narrow linewidth (<0.13 nm) single mode emission at very low thresholds (0.7 kW cm−2), long operational lifetimes (>105 pump pulses for oligomers with three to six repeating units) and wavelength tunability across the visible spectrum (408–591 nm). PMID:26416643

Tunable High-Intensity Electron Bunch Train Production Based on Nonlinear Longitudinal Space Charge Oscillation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Zhen; Yan, Lixin; Du, Yingchao

2016-05-05

High-intensity trains of electron bunches with tunable picosecond spacing are produced and measured experimentally with the goal of generating terahertz (THz) radiation. By imposing an initial density modulation on a relativistic electron beam and controlling the charge density over the beam propagation, density spikes of several-hundred-ampere peak current in the temporal profile, which are several times higher than the initial amplitudes, have been observed for the first time. We also demonstrate that the periodic spacing of the bunch train can be varied continuously either by tuning launching phase of a radiofrequency gun or by tuning the compression of a downstreammore » magnetic chicane. Narrow-band coherent THz radiation from the bunch train was also measured with μJ-level energies and tunable central frequency of the spectrum in the range of ~0.5 to 1.6 THz. Our results pave the way towards generating mJ-level narrow-band coherent THz radiation and driving high-gradient wakefield-based acceleration.« less