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Sample records for acousto-optic tunable filters

  1. Error Measurements in an Acousto-Optic Tunable Filter Fiber Bragg Grating Sensor System

    DTIC Science & Technology

    1994-05-01

    Acousto - Optic Tunable Filter--Fiber Bragg Grating (AOTF-FBG) system. This analysis was targeted to investigate the measurement error in the AOTF-FBG system...Fiber bragg grating, Wavelength division multiplexing, Acousto - optic tunable filter.

  2. Acousto-optic tunable filter imaging spectrometers

    NASA Technical Reports Server (NTRS)

    Chao, Tien-Hsin; Yu, Jeffrey; Reyes, George; Rider, David; Cheng, Li-Jen

    1991-01-01

    A remote sensing multispectral imaging instrument is being developed that uses a high resolution, fast programmable acoustooptic tunable filter (AOTF) as the spectral bandpass filter. A compact and fully computer controllable AOTF-based imaging spectrometer that operates in the visible wavelength range (0.5-0.8 microns) has been built and tested with success. A second imaging spectrometer operating in the near-infrared wavelength range (1.2-2.4 microns) is also under experimental investigation. The design criteria meeting various system issues, such as imaging quality, spectral response, and field of view (FOV), are discussed. An experiment using this AOTF imaging spectrometer breadboard is described.

  3. Acousto-Optic Tunable Filter for Time-Domain Processing of Ultra-Short Optical Pulses,

    DTIC Science & Technology

    The application of acousto - optic tunable filters for shaping of ultra-fast pulses in the time domain is analyzed and demonstrated. With the rapid...advance of acousto - optic tunable filter (AOTF) technology, the opportunity for sophisticated signal processing capabilities arises. AOTFs offer unique

  4. Acousto-optic tunable filter multispectral imaging system

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    This paper discusses recent activities of Jet Propulsion Laboratory in the development of a new type of remote sensing multispectral imaging instruments using acousto-optic tunable filter (AOTF) as programmable bandpass filter. This remote sensor provides real-time operation; observational flexibility; measurements of spectral, spatial, and polarization information using a single instrument; and compact, solid state structure without moving parts. Two microcomputer-controlled AOTF imaging spectrometer breadboard systems were designed and built. One operates in the wavelength range of 0.48-0.76 micron and the other in the range of 1.2-2.5 micron. Experiments were performed using these two systems to observe geological and botanical objects in laboratory and outdoor environment. Results have demonstrated the feasibility of using the AOTF multispectral imaging system as a real-time versatile remote sensor with operational flexibility for future Army tactical applications.

  5. Display system employing acousto-optic tunable filter

    NASA Technical Reports Server (NTRS)

    Lambert, James L. (Inventor)

    1993-01-01

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

  6. 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.

  7. Bioimaging system using acousto-optic tunable filter

    NASA Astrophysics Data System (ADS)

    Kasili, Paul M.; Mobley, Joel; Cullum, Brian M.; Vo-Dinh, Tuan

    2000-05-01

    The interaction of light with tissue has ben used to recognize disease since the mid-1800s. The recent developments of light sources, detectors, and fiber optic probes provide opportunities to measure these interactions, which yield information for tissue diagnosis at the biochemical, structural, or physiological level. In this paper, we describe a bioimaging system designed for biomedical applications and show laser-indued fluorescence (LIF) images mammalian brain tissue. The LIF imaging of tissue was carried out in vitro using two laser excitations: 488 nm and 514 nm. Images were recorded through an acousto- optic tunable filter over the range 500 nm-650 nm with a charged coupled device camera. Background subtracted images were generated across the fluorescent wavelength. Subtraction allowed a safe comparison to be made with well- contrasted images. Of the two tested excitation wavelengths, 488 nm excitation gave the more distinctive contrast.

  8. Materials for imaging acousto-optic tunable filters

    NASA Astrophysics Data System (ADS)

    Gupta, Neelam

    2014-05-01

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

  9. Swept laser source based on acousto-optic tunable filter

    NASA Astrophysics Data System (ADS)

    Chen, Minghui; Li, Hao; Chen, Rong

    2014-12-01

    The design and development of the swept laser for optical coherence tomography is presented. It is manifested by a semiconductor optical amplifier, a fiber coupler, two fiber isolators, a semiconductor optical amplifier (SOA) and an acousto-optic tunable filter (AOTF) for frequency tuning within a unidirectional all-fiber ring cavity. Light output from the coupler is further amplified and spectral shaped by a booster SOA terminated at both ends with two isolators. The total loss in ring cavity is 8.2 dB. The gain SOA provides fiber-to-fiber small signal gain of 22.2 dB with saturation output power of 9.0 dBm. The developed laser source provides up to 100 kHz over a full-width wavelength tuning range of 140 nm at center wavelength of 1308 nm with an average power of 8 mW, yielding an axial resolution of 5.4 μm in air for OCT imaging. Theoretically, the measurement principle and the feasibility of the system are analyzed. Implementing the laser source in swept source based OCT (SS-OCT) system, real-time structural imaging of biological tissue is realized.

  10. Compact tunable microwave filter using retroreflective acousto-optic filtering and delay controls.

    PubMed

    Riza, Nabeel A; Ghauri, Farzan N

    2007-03-01

    Programmable broadband rf filters are demonstrated using a compact retroreflective optical design with an acousto-optic tunable filter and a chirped fiber Bragg grating. This design enables fast 34 micros domain analog-mode control of rf filter time delays and weights. Two proof-of-concept filters are demonstrated including a two-tap notch filter with >35 dB notch depth and a four-tap bandpass filter. Both filters have 2-8 GHz tunability and a 34 micros reset time.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  12. CONTROL OF LASER RADIATION PARAMETERS: Tunable acousto-optic filters with the multiple interaction of light and sound

    NASA Astrophysics Data System (ADS)

    Voloshinov, V. B.; Magdich, L. N.; Knyazev, G. A.

    2005-11-01

    Optical multipass schemes of the interaction of light and sound, which are promising for filtration of optical beams based on tunable acousto-optic filters, are studied. The features of operation of acousto-optic filters in the rejection and transmission regimes are considered. It is proved theoretically and confirmed experimentally that the use of multiple interaction improves the spectral and energy parameters of acousto-optic devices. The collinear and transverse geometry of acousto-optic interaction in cells based on a paratellurite crystal is studied in the double-pass, three-pass, and multipass diffraction regimes.

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  14. A new method for determining the transfer function of an acousto optical tunable filter.

    PubMed

    Mahieux, A; Wilquet, V; Drummond, R; Belyaev, D; Federova, A; Vandaele, A C

    2009-02-02

    The current study describes the determination of the transfer function of an Acousto Optical Tunable Filter from the in-flight solar observations of the SOIR instrument on board Venus Express. An approach is proposed in order to reconstruct the transfer function profile from the analysis of various solar lines. Moreover this technique allows the determination of the evolution of the transfer function as a function of the AOTF radio frequency.

  15. Efficient double-filtering with a single acousto-optic tunable filter.

    PubMed

    You, Jang-Woo; Ahn, Jeongho; Kim, Soohyun; Kim, Daesuk

    2008-12-22

    We describe an efficient double-filtering method that uses a single acousto-optic tunable filter (AOTF) to improve the spectral resolution and intrinsic sidelobes for the spectral domain analysis systems. Double filtering with a single AOTF is realized by applying a unique feedback scheme based on the fact that incident light can be diffracted into two orthogonally polarized beams of light by an AOTF. Our theoretical explanation attempts to address and satisfy the main prerequisite for the proposed idea. The experimental results confirm that the proposed method achieves a 20% to 30% improvement in spectral resolution and 10 dB suppression of sidelobes with minimized light loss for the extraordinary incident light. We believe that the results of using an AOTF are comparable to the results achieved with two AOTFs in tandem.

  16. 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.

  17. Ultraviolet-visible imaging acousto-optic tunable filters in KDP.

    PubMed

    Voloshinov, Vitaly; Gupta, Neelam

    2004-07-01

    There is a need to develop large-aperture acousto-optic tunable filters (AOTFs) in the UV region for applications in astronomy, environmental sciences, biology, etc. We have developed a high-quality noncollinear AOTF cell that uses a single crystal of KDP that has nearly a four times larger acousto-optic figure of merit, M2, than quartz. The linear and angular apertures of this cell are 1.5 cm x 1.5 cm and 1.2 degrees, respectively. The spectral range is 220-480 nm, with 160-cm(-1) spectral resolution and high transmission in the UV. We present an analysis of the design and describe the characterization results.

  18. LIGHT MODULATION: Quasi-collinear tunable acousto-optic paratellurite crystal filters for wavelength division multiplexing and optical channel selection

    NASA Astrophysics Data System (ADS)

    Molchanov, V. Ya; Voloshinov, V. B.; Makarov, O. Yu

    2009-04-01

    Quasi-collinear acousto-optic interaction is studied in acoustically and optically anisotropic paratellurite crystals. The possible applications of this interaction in acousto-optic tunable filters with a high spectral resolution are discussed. Different modifications of devices are compared and variants of devices intended for processing light beams and selection of light signals in fibreoptic communication systems with wavelength division multiplexing (WDM) at λ simeq 1550 nm are considered.

  19. A Very Compact, High Speed and Rugged Acousto-Optic Tunable Filter for Wavelength Division Demultiplexing in Fiber Optic Communication Networks. Phase 1

    DTIC Science & Technology

    2007-11-02

    Novel concepts of near-collinear/collinear acousto - optic interactions have been investigated during this SBIR Phase I program. As a result, several...new acousto - optic tunable filters have been built and tested. The program is highlighted by: (1) Design, fabrication and experimental demonstration of...a novel TeO2 near-collinear acousto - optic tunable filter has been designed, fabricated and tested. The device exhibits a 1.29 nm spectral resolution

  20. Tunable transportable spectroradiometer based on an acousto-optical tunable filter: Development and optical performance

    NASA Astrophysics Data System (ADS)

    Kozlova, O.; Sadouni, A.; Truong, D.; Briaudeau, S.; Himbert, M.

    2016-12-01

    We describe a high-performance, transportable, versatile spectroradiometer based on an acousto-optical tunable filter (AOTF). The instrument was developed for temperature metrology, namely, to determine the thermodynamic temperature of black bodies above the Ag freezing point (961.78 °C). Its main design feature is the attenuation of the diffraction side lobes (and, thus, out-of-band stray light) thanks to the use of a double-pass configuration. The radiofrequency tuning of the AOTF allows continuous, fine, and rapid wavelength control over a wide spectral range (650 nm-1000 nm). The instrument tunability can be easily calibrated with an Ar spectral lamp with reproducibility within 10 pm over one week. The instrument was characterised in terms of relative signal stability (few 10-4) and wavelength stability (1 pm) over several hours. The spectral responsivity of the instrument was calibrated with two complementary methods: tuning of the wavelength of the optical source or tuning the radiofrequency of the AOTF. Besides the application for thermodynamic temperature determination at the lowest uncertainty level, this instrument can also be used for multispectral non-contact thermometry of processed materials of non-grey and non-unitary emissivity (in the glass or metallurgical industries).

  1. Hyperspectral imager, from ultraviolet to visible, with a KDP acousto-optic tunable filter.

    PubMed

    Gupta, Neelam; Voloshinov, Vitaly

    2004-05-01

    Hyperspectral imaging in the ultraviolet to visible spectral region has applications in astronomy, biology, chemistry, medical sciences, etc. A novel electronically tunable, random-wavelength access, compact, no-moving-parts, vibration-insensitive, computer-controlled hyperspectral imager operating from 220 to 480 nm with a spectral resolution of 160 cm(-1), e.g., 2 nm at 350 nm, has been developed by use of a KDP acousto-optic tunable filter (AOTF) with an enhanced CCD camera and a pair of crossed calcite Glan-Taylor polarizing prisms. The linear and angular apertures of the AOTF are 1.5 x 1.5 cm2 and 1.2 degrees, respectively. Imager setup and spectral imaging results as well as analyses and discussion of various factors affecting image quality are presented.

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

    NASA Technical Reports Server (NTRS)

    Mickey, Donald L.

    1994-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Prasad, Narasimha S.

    2006-01-01

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

  4. Configurable-bandwidth imaging spectrometer based on an acousto-optic tunable filter

    NASA Astrophysics Data System (ADS)

    Vila-Francés, Joan; Calpe-Maravilla, Javier; Muñoz-Mari, Jordi; Gómez-Chova, Luis; Amorós-López, Julia; Ribes-Gómez, Emilio; Durán-Bosch, Vicente

    2006-07-01

    This article presents a new imaging spectrometer called autonomous tunable filtering system. The instrument acquires sequential images at different spectral wavelengths in the visible and near infrared range of the electromagnetic spectrum. The spectral selection is performed by an acousto-optic tunable filter (AOTF), which is driven by a custom radio-frequency (rf) generator based on a direct digital synthesizer (DDS). The DDS allows a high flexibility in terms of acquisition speed and bandwidth selection. The rf power is dynamically controlled to drive the AOTF with the optimum value for each wavelength. The images are formed through a carefully designed optical layout and acquired with a high performance digital camera. The application software controls the instrument and acquires the raw spectral images from the camera. This software optionally corrects the image for the AOTF nonidealities, such as diffraction efficiency variations, spatial nonuniformity, and chromatic aberration, and generates a single multiband image file. Moreover, the software can calculate the reflectance or transmittance of the acquired images. The instrument has been calibrated to give precise and repetitive measurements and has been validated against a high performance point spectrometer. As a case example, the instrument has been successfully used for the mapping of chlorophyll content of plant leaves from their multispectral reflectance images.

  5. Acousto-optic tunable filter for dispersion characterization of time-domain optical coherence tomography systems.

    PubMed

    Chin, Catherine; Toadere, Florin; Feuchter, Thomas; Leick, Lasse; Moselund, Peter; Bradu, Adrian; Podoleanu, Adrian

    2016-07-20

    A broadband supercontinuum light source with an acousto-optic tunable filter (AOTF) are used to characterize dispersion in two time-domain OCT systems, at 850 and 1300 nm. The filter is designed to sweep across two spectral ranges, which are restricted here from 800 to 900 nm and from 1200 to 1500 nm, respectively. Dispersion compensation for 850 nm was achieved with a spectral delay line. Dispersion compensation for 1300 nm was achieved using BK 7 rod glasses in the reference arm. The AOTF allows evaluation of dispersion in under as well as overcompensated systems. The AOTF method is based on wavelength dependence of the optical path difference corresponding to the maximum strength of the interference signal recorded using a mirror as object. Comparison is made between the AOTF method and the more usual method based on measurement of the full width at half-maximum of the autocorrelation peak. This comparison shows that the AOTF method is more accurate in terms of evaluation of the dispersion left uncompensated after each adjustment. The AOTF method additionally provides information on the direction of dispersion compensation.

  6. An acousto-optic tunable filter enhanced CO{sub 2} lidar atmospheric monitor

    SciTech Connect

    Taylor, L.H.; Suhre, D.R.; Mani, S.S.

    1996-12-31

    The atmospheric monitor conceptual design is based on a pulsed CO{sub 2} laser. The narrow laser lines provide high spectral selectivity in the 9-11 {mu}m region, within the 8-14 {mu}m ``fingerprint`` region where most large molecules have unique spectral absorption signatures. Laser power has been chosen so that topological objects, e.g., trees or buildings, as far as 4 km can be used as backreflectors, but the laser intensity is sufficiently low that the laser beam is eye-safe. Time-of-flight measurements give the distance to the topological reflector. The lidar system is augmented with an acousto-optic tunable filter (AOTF) which measures the thermal emission spectra from 3 to 14 {mu}m with a 3 cm{sup -1} passband. Sensitivity to narrow emission lines is enhanced by derivative spectroscopy in which the passband of the AOTF is dithered via the rf drive. Path-averaged concentrations are determined from the emission intensity and laser- determined range.

  7. Narrow-band acousto-optic tunable filtering in a two-mode fiber.

    PubMed

    Ostling, D; Engan, H E

    1995-06-01

    We demonstrate an optical filter that utilizes acousto-optic coupling between the spatial modes that propagate in a two-mode elliptical-core fiber. The optical bandwidth at 1090 nm is 0.85 nm, which is in agreement with predictions based on measurement of differential group delay between the modes. The filter is slightly polarization dependent, with a 0.28-nm wavelength difference between the passband peaks for the two polarization eigenstates. The optical insertion loss is dominated by 2-4-dB bending loss in nonoptimized mode strippers, and the coupling loss is negligible. Full acousto-optic mode conversion was achieved at an 8-mW electrical input power to the acoustic transducer.

  8. Hyperspectral imaging performance based on two TeO2 acousto-optic tunable filters.

    PubMed

    Wang, Pengchong; Zhang, Zhonghua

    2017-02-20

    The performance parameters of an acousto-optic tunable filter (AOTF) were reasonably optimized based on the previous research, according to which two AOTFs that could be applied to hyperspectral imaging were produced. Through testing, the basic tuning relationship of the two AOTFs was basically in line with the principle. Then, a hyperspectral imaging system was built based on the two AOTFs, and a long-range perspective target imaging experiment was carried out in the entire white light region. Finally, the proposed double-filtering method was applied to the hyperspectral imaging for the first time, and the imaging result was analyzed in detail.

  9. Pure electrical, highly-efficient and sidelobe free coherent Raman spectroscopy using acousto-optics tunable filter (AOTF)

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    Fast and sensitive Raman spectroscopy measurements are imperative for a large number of applications in biomedical imaging, remote sensing and material characterization. Stimulated Raman spectroscopy offers a substantial improvement in the signal-to-noise ratio but is often limited to a discrete number of wavelengths. In this report, by introducing an electronically-tunable acousto-optical filter as a wavelength selector, a novel approach to a broadband stimulated Raman spectroscopy is demonstrated. The corresponding Raman shift covers the spectral range from 600 cm‑1 to 4500 cm‑1, sufficient for probing most vibrational Raman transitions. We validated the use of the new instrumentation to both coherent anti-Stokes scattering (CARS) and stimulated Raman scattering (SRS) spectroscopies.

  10. Pure electrical, highly-efficient and sidelobe free coherent Raman spectroscopy using acousto-optics tunable filter (AOTF).

    PubMed

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

    2016-02-01

    Fast and sensitive Raman spectroscopy measurements are imperative for a large number of applications in biomedical imaging, remote sensing and material characterization. Stimulated Raman spectroscopy offers a substantial improvement in the signal-to-noise ratio but is often limited to a discrete number of wavelengths. In this report, by introducing an electronically-tunable acousto-optical filter as a wavelength selector, a novel approach to a broadband stimulated Raman spectroscopy is demonstrated. The corresponding Raman shift covers the spectral range from 600 cm(-1) to 4500 cm(-1), sufficient for probing most vibrational Raman transitions. We validated the use of the new instrumentation to both coherent anti-Stokes scattering (CARS) and stimulated Raman scattering (SRS) spectroscopies.

  11. Acousto-optic filtering of lidar signals

    NASA Astrophysics Data System (ADS)

    Kolarov, G.; Deleva, A.; Mitsev, Ts.

    1992-07-01

    The predominant part of the noise in lidar receivers is created by the background radiation; therefore, one of the most important elements of the receiving optics is a spectrally selecting filter placed in front of the photodetector. Interference filters are usually used to transmit a given wavelength. Specific properties of the interference filters, such as simple design, reliability, small size, and large aperture, combined with high transmission coefficient and narrow spectral band, make them the preferred spectral device in many cases. However, problems arise in applications such as the Differential Absorption Lidar (DIAL) technique, where fast tuning within a wide spectral region is necessary. Tunable acousto-optical filters (TAOF), used recently in astrophysical observations to suppress the background radiation, can be employed with success in lidar sounding. They are attractive due to the possibility for fast spectral scanning with a narrow transmission band. The TAOF's advantages are fully evident in DIAL lidars where one must simultaneously receive signals at two laser frequencies.

  12. Acousto-optic filtering of lidar signals

    NASA Technical Reports Server (NTRS)

    Kolarov, G.; Deleva, A.; Mitsev, TS.

    1992-01-01

    The predominant part of the noise in lidar receivers is created by the background radiation; therefore, one of the most important elements of the receiving optics is a spectrally selecting filter placed in front of the photodetector. Interference filters are usually used to transmit a given wavelength. Specific properties of the interference filters, such as simple design, reliability, small size, and large aperture, combined with high transmission coefficient and narrow spectral band, make them the preferred spectral device in many cases. However, problems arise in applications such as the Differential Absorption Lidar (DIAL) technique, where fast tuning within a wide spectral region is necessary. Tunable acousto-optical filters (TAOF), used recently in astrophysical observations to suppress the background radiation, can be employed with success in lidar sounding. They are attractive due to the possibility for fast spectral scanning with a narrow transmission band. The TAOF's advantages are fully evident in DIAL lidars where one must simultaneously receive signals at two laser frequencies.

  13. A rapid excitation-emission matrix fluorometer utilizing supercontinuum white light and acousto-optic tunable filters.

    PubMed

    Wang, Wenbo; Wu, Zhenguo; Zhao, Jianhua; Lui, Harvey; Zeng, Haishan

    2016-06-01

    Scanning speed and coupling efficiency of excitation light to optic fibres are two major technical challenges that limit the potential of fluorescence excitation-emission matrix (EEM) spectrometer for on-line applications and in vivo studies. In this paper, a novel EEM system, utilizing a supercontinuum white light source and acousto-optic tunable filters (AOTFs), was introduced and evaluated. The supercontinuum white light, generated by pumping a nonlinear photonic crystal fiber with an 800 nm femtosecond laser, was efficiently coupled into a bifurcated optic fiber bundle. High speed EEM spectral scanning was achieved using AOTFs both for selecting excitation wavelength and scanning emission spectra. Using calibration lamps (neon and mercury argon), wavelength deviations were determined to vary from 0.18 nm to -0.70 nm within the spectral range of 500-850 nm. Spectral bandwidth for filtered excitation light broadened by twofold compared to that measured with monochromatic light between 650 nm and 750 nm. The EEM spectra for methanol solutions of laser dyes were successfully acquired with this rapid fluorometer using an integration time of 5 s.

  14. Novel time-of-flight fiber dispersion measurement technique using supercontinuum light sources and acousto-optical tunable filters.

    PubMed

    Blume, Niels Göran; Wagner, Steven

    2015-07-20

    Long-distance fiber links require precise knowledge of fiber dispersion characteristics. Similar dispersion characteristics are necessary for supercontinuum broadband laser absorption spectroscopy (SCLAS) to allow proper data evaluation and species concentration determination, as well as numerous other applications. In this work, a time-of-flight approach to measuring the dispersion characteristic of fibers with supercontinuum laser light sources (SCLs) and acousto-optical tunable filters (AOTFs) is presented. Broadband emission of the SCL is filtered with a narrowband AOTF and dispersed in time by the fiber under test. By using the wavelength-specific delay, the dispersion characteristic can be calculated. The technique is especially suited for longer fibers and was verified against a state-of-the-art phase-shift-based dispersion measurement system. Advantages of the new approach include solely utilizing SCLAS system components, as well as a high level of automation and wide spectral coverage, ranging from 1100 to 1700 nm in a single measurement setup.

  15. Wet/dry film thickness measurement of paint by absorption spectroscopy with acousto-optic tunable filter spectrometer

    NASA Astrophysics Data System (ADS)

    Sinha, Pranay G.; Xiong, Xiangchun; Jin, Feng; Trivedi, Sudhir; Prasad, Narashima S.

    2005-08-01

    Controlling/monitoring the thickness of applied paint in real time is important to many situations including painting ship and submarine hulls in dry docks for maintaining health of ships and submarines against the harshness of the sea, in automobile and aerospace industries, and in a variety of other industries as a control sensor that plays significant role in product quality, process control, and cost control. Insufficient thickness results to inadequate protection while overspray leads to waste and pollution of the environment. A rugged instrumentation for the real time non-contact accurate measurement of wet and dry paint film thickness measurement will be immensely valuable. As paint is applied with several layers of the same or different type, thickness of each newly sprayed wet layer is of most interest, but measurement on dry paint is also useful. In this study, we use acousto-optic tunable filter-based near infrared spectrometer to obtain the absorption spectrum of layers of paint sprayed on sand blasted steel surface and thus measure the thickness of coating under both wet and dry situations. NIR spectra are obtained from 1100 to 2300 nm on four sample of different thickness of paint up to 127 micron. Partial least squares model built with the spectra shows good correlation with standard error of prediction within ~ 0.7 micron. Results indicate that the spectra also respond to the amount of organic solvent in the wet paint and can be used to monitor the degree of dryness of the paint in real time.

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

    PubMed

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

    2017-01-05

    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.

  17. 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

  18. Acousto-Optically Addressed Fourier Transform Matched Filters.

    DTIC Science & Technology

    1984-08-01

    ACOUSTO - OPTIC DEFLECTOR .............................. II. THE EXPERIMENT............................................. 2 FV XPERIMENTAl. RESULTS...tcohniqtie1 arc addressed using an acousto - optic beam deflector with good correlation signals resulting. Th is method may be used to address arrays of matched...essentially the standard Vander Lugt method for making matched filters, except for the addition of the acousto - optic deflector between the Fourier

  19. Numerical Analysis of the Crosstalk on an Integrated Acousto-Optic Tunable Filter (AOTF) for Network Applications

    NASA Astrophysics Data System (ADS)

    Sobrinho, C. S.; de Oliveira, M. V. N.; Silva, M. G. Da; Lima, J. L. S.; de Almeida, E. F.; Sombra, A. S. B.

    In this article, we did a study of the crosstalk level (Xtalk) and extinction ratio (Xratio) of an acousto-optic tunable filter (AOTF) operating with ultra-short light pulses (2 ps). It is clear that the transmission bandwidth decreases as the length of the device increases. The compression factor was studied for the switched pulse in an AOTF without loss considering five nonlinearity profiles. One can observe that there is always an optimum value for β (final value of the nonlinearity) that one can obtain a switched pulse with the same time duration of the input pulse. The study of the crosstalk level, of this device, considering the optimum values of β obtained from the compression studies, as a function of the pump power (P0) was done. For the soliton profile at 1 W of pump power one can notice that the Gaussian profile presents the lower Xtalk value (-13 dB), and the constant profile presents the worst value (-9.8 dB). However, if one is looking for a specific Xtalk value, one can conclude that with the constant profile one can obtain this value with a lower power. For the quasi-soliton profile of the same device, with low pump power (1 W), one can notice again that the Gaussian profile presents the lower Xtalk value (-13 dB) and the constant profile presents the worst value (-9.87 dB). This fact can be explained because, with pump power at 1 W, soliton and quasi-soliton profiles lead equivalent input pulses and under the same conditions produce equal results. The Xtalk level, considering all the profiles as a function of the β value, was studied. For all the profiles one has a strong increase of the Xtalk level with the increase of the final β value of the nonlinearity profile. Comparing all the profiles one can conclude that the Gaussian profile presents the lower Xtalk value in the range of β values in use. At the same time the value of the Xtalk for this profile does not change much with the change in the β value, presenting values in interval (-13 d

  20. Fiber-optic tunable multiwavelength variable attenuator and routing module designs that use bulk acousto-optics.

    PubMed

    Riza, Nabeel A; Mughal, M Junaid

    2005-02-10

    A compact fiber-coupled bulk acousto-optical multiwavelength variable optical attenuator module design that uses a retroreflective double-pass geometry within a single bulk acousto-optic tunable filter device is presented. The proposed attenuator module demonstrates a high 17-dB notch dynamic range at a low 100-mW drive power and uses a single bulk collinear-interaction acousto-optic tunable-filter device. Experiments show a low (<1.8-dB) fiber-to-fiber insertion loss with a fast 34-micros speed within a wide 1520-1640-nm agile multinotch band. The basic broadband attenuator module design is extended to allow for efficient architectures for routing modules such as agile drop filters, analog hitless tap filters, and digital add-drop switches.

  1. Acousto-optic collinear filter with optoelectronic feedback

    NASA Astrophysics Data System (ADS)

    Mantsevich, S. N.; Balakshy, V. I.; Kuznetsov, Yu. I.

    2017-04-01

    A spectral optoelectronic system combining a collinear acousto-optic cell fabricated of calcium molybdate single crystal and a positive electronic feedback is proposed first and examined theoretically and experimentally. The feedback signal is formed at the cell output due to the optical heterodyning effect with the use of an unconventional regime of cell operation. It is shown that the feedback enables controlling spectral characteristics of the acousto-optic cell, resulting in enhancing the spectral resolution and the accuracy of optical wavelength determination. In the experiment, maximal filter passband narrowing was as great as 37 times.

  2. Contrast enhancement in microscopy of human thyroid tumors by means of acousto-optic adaptive spatial filtering

    NASA Astrophysics Data System (ADS)

    Yushkov, Konstantin B.; Molchanov, Vladimir Y.; Belousov, Pavel V.; Abrosimov, Aleksander Y.

    2016-01-01

    We report a method for edge enhancement in the images of transparent samples using analog image processing in coherent light. The experimental technique is based on adaptive spatial filtering with an acousto-optic tunable filter in a telecentric optical system. We demonstrate processing of microscopic images of unstained and stained histological sections of human thyroid tumor with improved contrast.

  3. Fiber-Coupled Acousto-Optical-Filter Spectrometer

    NASA Technical Reports Server (NTRS)

    Levin, Kenneth H.; Li, Frank Yanan

    1993-01-01

    Fiber-coupled acousto-optical-filter spectrometer steps rapidly through commanded sequence of wavelengths. Sample cell located remotely from monochromator and associated electronic circuitry, connected to them with optical fibers. Optical-fiber coupling makes possible to monitor samples in remote, hazardous, or confined locations. Advantages include compactness, speed, and no moving parts. Potential applications include control of chemical processes, medical diagnoses, spectral imaging, and sampling of atmospheres.

  4. Compact high-resolution spaceborne echelle grating spectrometer with acousto-optical tunable filter based order sorting for the infrared domain from 2.2 to 4.3 microm.

    PubMed

    Nevejans, Dennis; Neefs, Eddy; Van Ransbeeck, Emiel; Berkenbosch, Sophie; Clairquin, Roland; De Vos, Lieve; Moelans, Wouter; Glorieux, Stijn; Baeke, Ann; Korablev, Oleg; Vinogradov, Imant; Kalinnikov, Yuri; Bach, Benny; Dubois, Jean-Pierre; Villard, Eric

    2006-07-20

    A new compact spaceborne high-resolution spectrometer developed for the European Space Agency's Venus Express spacecraft is described. It operates in the IR wavelength range of 2.2 to 4.3 microm and measures absorption spectra of minor constituents in the Venusian atmosphere. It uses a novel echelle grating with a groove density of 4 lines/mm in a Littrow configuration in combination with an IR acousto-optic tunable filter for order sorting and an actively cooled HgCdTe focal plane array of 256 by 320 pixels. It is designed to obtain an instrument line profile of 0.2 cm(-1). First results on optical and spectral properties are reported.

  5. Acousto-Optical Imaging Spectropolarimeter

    NASA Technical Reports Server (NTRS)

    Saif, Babak; Glenar, David; Zimmerman, Robert; Seery, Bernard

    1992-01-01

    Imaging spectropolarimeter designed around acousto-optical tunable filter (AOTF) takes polarization-specific spectral images of solid surfaces, aerosols, and absorption and emission phenomena in gas phase, at wavelengths from 500 to 1,000 nm. Produces side-by-side spectral images in two mutually perpendicular polarizations, one corresponding to ordinary, other corresponding to extraordinary waves in acousto-optical material. Offers large aperture, high resolving power, and rapid tunability, with no moving parts.

  6. Effect of optoelectronic feedback on the characteristics of acousto-optical collinear filtering

    SciTech Connect

    Balakshy, V I; Kuznetsov, Yu I; Mantsevich, S N

    2016-02-28

    The first results of the theoretical and experimental studies of an acousto-optical system with feedback based on a collinear cell made of a calcium molybdate crystal are presented. It is shown that the positive electronic feedback allows essential sharpening of the instrument function of the acousto-optical collinear filter, thus increasing the precision of measuring the optical radiation wavelength. (acoustooptics)

  7. Analysis of quality of images obtained by acousto-optic filtering

    NASA Astrophysics Data System (ADS)

    Bogomolov, Dennis V.; Voloshinov, Vitaly B.

    2005-03-01

    The paper is devoted to the theoretical and experimental investigation of spatial resolution of images obtained during acousto-optic spectral filtration. The consideration was carried out for a wide angle acousto-optic filter designed on the base of paratellurite single crystal. The crystal was cut in the (1 1 0) plane with the direction of acoustic wave propagation at the angle 10 ° relative to the axis [110]. It was found that optical quality of a filtered image is influenced by a spectral bandwidth of a filter. The spectral bandwidth is determined by a length of piezoelectric transducer that generates ultrasonic waves in an acousto-optic cell. The dependence of a number of resolvable spots on the piezotransducer length was examined theoretically. It was shown that a wavelength of the filtered radiation influences the quality of the processed image. Precise and approximate equations have been derived to determine the spectral passband of the acousto-optic filer, the angular field of view of a single pixel, the angular aperture of the device and the number of resolvable spots in a line. Resolution of the images obtained during the acousto-optic filtration was also measured in the experiment.

  8. Tunable acousto-optic spectral imager for atmospheric composition measurements in the visible spectral domain.

    PubMed

    Dekemper, Emmanuel; Loodts, Nicolas; Van Opstal, Bert; Maes, Jeroen; Vanhellemont, Filip; Mateshvili, Nina; Franssens, Ghislain; Pieroux, Didier; Bingen, Christine; Robert, Charles; De Vos, Lieve; Aballea, Ludovic; Fussen, Didier

    2012-09-01

    We describe a new spectral imaging instrument using a TeO(2) acousto-optical tunable filter (AOTF) operating in the visible domain (450-900 nm). It allows for fast (~1 second), monochromatic (FWHM ranges from 0.6 nm at 450 nm to 3.5 nm at 800 nm) picture acquisition with good spatial resolution. This instrument was designed as a breadboard of the visible channel of a new satellite-borne atmospheric limb spectral imager, named the Atmospheric Limb Tracker for the Investigation of the Upcoming Stratosphere (ALTIUS), that is currently being developed. We tested its remote sensing capabilities by observing the dense, turbulent plume exhausted by a waste incinerator stack at two wavelengths sensitive to NO(2). An average value of 6.0±0.4×10(17) molecules cm(-2) has been obtained for the NO(2) slant column density within the plume, close to the stack outlet. Although this result was obtained with a rather low accuracy, it demonstrates the potential of spectral imaging by using AOTFs in remote sensing.

  9. Wide-aperture diffraction of unpolarised radiation in a system of two acousto-optic filters

    SciTech Connect

    Magdich, L N; Yushkov, K B; Voloshinov, V B

    2009-04-30

    Light diffraction is studied in two tandem acousto-optic cells filtering unpolarised radiation with a wide angular spectrum. It is shown that the side lobes of the ultrasonic radiation pattern of a piezoelectric transducer produce side diffraction intensity maxima at the output of the system consisting of two filters. Diffraction in paratellurite filters is studied experimentally at 1.06 {mu}m. (light modulation)

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  11. Wide spectral range imaging acousto-optic turnable filter used in outer space probe

    NASA Astrophysics Data System (ADS)

    Zhang, Zehong; Wang, Liangqiu; He, Xiaoliang; Zhou, Yong

    2014-02-01

    This article introduces a wide spectral range imaging acousto-optic turnable filter made of two transducers. "Mismatch rate" was firstly put forward to represent the degree to which the impedance mismatch and a three stage matching circuit was designed for the filter to improve its spectral range and operating bandwidth. Now the spectral range is from 0.4μm to 1.1μm, the overall operating bandwidth reaches 1.14 octave, the diffraction efficiency over 60%, spectral resolution from 1.3nm to 7.5nm. To get rid of " tin pest", alloy material was used to make bonding layer material instead of pure tin, making the storage temperature of the acousto-optic turnable filter ranges from -65 °C to 85 °C, and the operating temperature from -35 °C to 70 °C.

  12. Narrow linewidth broadband tunable semiconductor laser at 840 nm with dual acousto-optic tunable configuration for OCT applications

    NASA Astrophysics Data System (ADS)

    Chamorovskiy, Alexander; Shramenko, Mikhail V.; Lobintsov, Andrei A.; Yakubovich, Sergei D.

    2016-03-01

    We demonstrate a tunable narrow linewidth semiconductor laser for the 840 nm spectral range. The laser has a linear cavity comprised of polarization maintaining (PM) fiber. A broadband semiconductor optical amplifier (SOA) in in-line fiber-coupled configuration acts as a gain element. It is based on InGaAs quantum-well (QW) active layer. SOA allows for tuning bandwidth exceeding 25 nm around 840 nm. Small-signal fiber-to-fiber gain of SOA is around 30 dB. A pair of acousto-optic tunable filters (AOTF) with a quasi-collinear interaction of optical and acoustic waves are utilized as spectrally selective elements. AOTF technology benefits in continuous tuning, broadband operation, excellent reproducibility and stability of the signal, as well as a high accuracy of wavelength selectivity due to the absence of mechanically moving components. A single AOTF configuration has typical linewidth in 0.05-0.15 nm range due to a frequency shift obtained during each roundtrip. A sequential AOTF arrangement enables instantaneous linewidth generation of <0.01 nm by compensating for this shift. Linewidth as narrow as 0.0036 nm is observed at 846 nm wavelength using a scanning Fabry-Perot interferometer with 50 MHz spectral resolution. Output power is in the range of 1 mW. While the majority of commercial tunable sources operate in 1060-1550 nm spectral ranges, the 840 nm spectral range is beneficial for optical coherence tomography (OCT). The developed narrow linewidth laser can be relevant for OCT with extended imaging depth, as well as spectroscopy, non-destructive testing and other applications.

  13. Development of New Electro-Optic and Acousto-Optic Materials.

    DTIC Science & Technology

    1983-11-01

    Improved materials are required for active optical devices, including electro - optic and acousto-optic modulators, switches and tunable filters, as...many microwave applications. In addition, electro - optic and acousto-optic devices are materials limited because the materials currently available are...these materials for applications involving the electro - optic effect, degenerate four-wave mixing and surface acoustic wave technology.

  14. LIGHT MODULATION: Wide-aperture diffraction of unpolarised radiation in a system of two acousto-optic filters

    NASA Astrophysics Data System (ADS)

    Magdich, L. N.; Yushkov, K. B.; Voloshinov, V. B.

    2009-04-01

    Light diffraction is studied in two tandem acousto-optic cells filtering unpolarised radiation with a wide angular spectrum. It is shown that the side lobes of the ultrasonic radiation pattern of a piezoelectric transducer produce side diffraction intensity maxima at the output of the system consisting of two filters. Diffraction in paratellurite filters is studied experimentally at 1.06 μm.

  15. A RAPIDLY-TUNABLE ACOUSTO-OPTIC SPECTROMETER FOR A SPACE ENVIRONMENT

    SciTech Connect

    D. THOMPSON; C. HEWITT; C. WILSON

    2000-08-01

    As a complement to our work developing rapidly-tunable ({approximately}10-100 kHz) CO{sub 2} lasers for differential absorption lidar (DIAL) applications,l we have developed a rapidly-tunable spectrometer. A rapid spectral diagnostic is critical for a high speed DIAL system, since analysis of the return signals depends on knowing the spectral purity of the transmitted beam. The spectrometer developed for our lidar system is based on a double-passed large- (75 mm) aperture acousto-optic deflector, a grating, and a fast single-element room temperature mercury-cadmium-telluride detector. The spectrometer has a resolution of {approximately}0.5 cm{sup {minus}1}, a tuning range of 9.0-11.4 pm, a random-access tuning speed of greater than 80 kHz and a S/N ratio of greater than 100:1. We describe the design and performance of this device, as well as of future devices featuring improved resolution, higher speed and easier and more robust alignment. We will also briefly discuss the applications and limitations of the technique in a space environment.

  16. Compact interrogator for fiber optic Bragg sensors based on an acousto-optic filter formed by photonic crystal rows of air holes.

    PubMed

    Tsarev, Andrei V; De Leonardis, Francesco; Passaro, Vittorio M N

    2011-10-01

    Fiber optic sensors are typically used with expensive tunable lasers or optical spectrum analyzers for wavelength interrogation. We propose to replace the tunable laser by a broadband optical source incorporated with a novel thin linewidth acousto-optic tunable filter. It utilizes optical beam expanders constituted by photonic crystal rows of air holes in LiNbO(3) waveguide. A new design is numerically studied for a short structure (with 32 photonic crystal rows) by a two-dimensional finite-difference time-domain method. Extrapolation of these results to larger structure sizes (about 1 cm) demonstrates the possibility to develop compact interrogators with 0.4 pm wavelength resolution and 40 nm tunable range around 1550 nm.

  17. All-fiber tunable filter and laser based on two-mode fiber.

    PubMed

    Yun, S H; Hwang, I K; Kim, B Y

    1996-01-01

    We demonstrate an all-fiber acousto-optic tunable filter based on two-spatial-mode coupling, with improved ruggedness and efficiency, by using a new acoustic-transducer design. We use a rigorous modeling of the flexural acoustic wave to analyze the mode coupling with better accuracy. Using the acousto-optic tunable filter, we demonstrate a novel all-fiber tunable laser with a tuning range of more than 20 nm and a linewidth of 0.2 nm.

  18. Advanced fluorescence imaging endoscopy using an acousto-optic tuneable filter

    NASA Astrophysics Data System (ADS)

    Whelan, Maurice P.; Bouhifd, Mounir; Aprahamian, Marc

    2004-07-01

    Two novel prototype instruments for in vivo fluorescence-based medical diagnostics are described. The devices are based on an acousto-optic tuneable filter (AOTF) and can be easily attached to the eyepiece of most commercially available endoscopes. The instruments developed offer significant advantages over typical fixed-filter or filter-wheel fluorescence imaging systems in terms of flexibility, performance and diagnostic potential. Any filtering center-wavelength in the range from 450 to 700 nm can be rapidly selected either by random access or sequential tuning using simple commands delivered over a PC serial interface. In addition, both filtered and unfiltered light can be imaged to facilitate the direct association of fluorescence signals with specific anatomical sites. To demonstrate the system in vivo, a study of the diagnostic potential of fluorescence imaging for pancreatitis was conducted on rats. The aim was to detect extremely low-levels of endogenous protoporphyrin IX (PpIX) that has been shown to accumulate in early-stage diseased tissue undergoing an inflammatory response. Results show clearly that the device is effective in diagnosing mild pancreatitis in rats without the necessity of administering PpIX promoting agents such as ALA. Planning of human clinical trials is currently underway to demonstrate its potential as a tool for non-invasive early diagnosis of gastroenterological diseases.

  19. Experimental study of the use of multiband acousto-optic filters for spectral encoding / decoding the optical signals

    NASA Astrophysics Data System (ADS)

    Proklov, V. V.; Byshevski-Konopko, O. A.; Filatov, A. L.; Lugovskoi, A. V.; Pisarevsky, Yu V.

    2016-08-01

    A prototype of the acousto-optic (AO) decoder of optical signals is created on the base of the multiband AO filter. The joint work of the decoder with the developed previously AO coder has been verified experimentally. The main qualitative and quantitate characteristics of the spectral coding and decoding by Walsh sequences of the industrial LED radiation in the near infrared range are investigated. It is shown, that in the proposed data transmission system realization Signal-to-Interference Ratio (SIR) is not less than 13 dB.

  20. Acousto-Optic-Based Wavelength-Comb-Swept Laser for Extended Displacement Measurements.

    PubMed

    Park, Nam Su; Chun, Soo Kyung; Han, Ga-Hee; Kim, Chang-Seok

    2017-03-31

    We demonstrate a novel wavelength-comb-swept laser based on two intra-cavity filters: an acousto-optic tunable filter (AOTF) and a Fabry-Pérot etalon filter. The AOTF is used for the tunable selection of the output wavelength with time and the etalon filter for the narrowing of the spectral linewidth to extend the coherence length. Compared to the conventional wavelength-swept laser, the acousto-optic-based wavelength-comb-swept laser (WCSL) can extend the measureable range of displacement measurements by decreasing the sensitivity roll-off of the point spread function. Because the AOTF contains no mechanical moving parts to select the output wavelength acousto-optically, the WCSL source has a high wavenumber (k) linearity of R² = 0.9999 to ensure equally spaced wavelength combs in the wavenumber domain.

  1. On the possibility of developing incoherent fibre-optic data transmission systems based on signal spectral coding with matched acousto-optical filters

    SciTech Connect

    Proklov, Valerii V; Byshevski-Konopko, O A; Grigorievski, V I

    2013-06-30

    The scheme is suggested for developing the optical communication line based on the principle of code division of multiple access with matched acousto-optical filters and a 16-bit long Walsh sequence. Results of modelling show that such a line can operate if adjacent spectral lines are separated by at least double the Rayleigh criterion. (optical information transmission)

  2. Acousto-Optic Interactions.

    DTIC Science & Technology

    The document reports the results of the experimental and theoretical investigation of acousto - optic interactions in guided wave structure for optical...waves and acoustic surface waves and experimental results of isotropic and anisotropic diffraction in LiNbO3 and quartz. A simple acousto - optic plate...CVD ZnO films on sapphire, which may be needed for the acousto - optic devices in thin films are also included. (Author)

  3. 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.

  4. The Role of Adaptive Photorefractive Power Limiting on Acousto-Optic Radio Frequency (RF) Signal Excision

    DTIC Science & Technology

    2001-12-01

    Adaptive RF interference reduction for broadband communication systems continues to be problematic. The acousto - optic RF signal excision system...novel photorefractive optical power limiting device to achieve adaptive notch filtering, and multi- channel acousto - optic deflection to achieve angle...of-arrival signal discrimination at the notch filter. This dissertation describes basic principles of acousto - optic RF signal excision, including

  5. Rigorous coupled wave analysis of acousto-optics with relativistic considerations.

    PubMed

    Xia, Guoqiang; Zheng, Weijian; Lei, Zhenggang; Zhang, Ruolan

    2015-09-01

    A relativistic analysis of acousto-optics is presented, and a rigorous coupled wave analysis is generalized for the diffraction of the acousto-optical effect. An acoustic wave generates a grating with temporally and spatially modulated permittivity, hindering direct applications of the rigorous coupled wave analysis for the acousto-optical effect. In a reference frame which moves with the acoustic wave, the grating is static, the medium moves, and the coupled wave equations for the static grating may be derived. Floquet's theorem is then applied to cast these equations into an eigenproblem. Using a Lorentz transformation, the electromagnetic fields in the grating region are transformed to the lab frame where the medium is at rest, and relativistic Doppler frequency shifts are introduced into various diffraction orders. In the lab frame, the boundary conditions are considered and the diffraction efficiencies of various orders are determined. This method is rigorous and general, and the plane waves in the resulting expansion satisfy the dispersion relation of the medium and are propagation modes. Properties of various Bragg diffractions are results, rather than preconditions, of this method. Simulations of an acousto-optical tunable filter made by paratellurite, TeO(2), are given as examples.

  6. Exploring Novel Crystals and Designs for Acousto-Optic Devices

    NASA Astrophysics Data System (ADS)

    Pfeiffer, Jonathan B.

    Acousto-optic devices are a versatile technology that are driven electronically to precisely and rapidly control the intensity, frequency, and propagation direction of a laser beam. Applications include acousto-optic scanners, filters, mode lockers, and modulators. Despite the popularity of acousto-optic devices, there currently is no UV transparent device that can satisfy the requirements of the atomic clock and quantum computing communities. In this thesis, I describe my experimental efforts for discovering a new UV transparent, acousto-optic crystal that can meet the experimental requirements. I also present my graphical representations for locating practical and efficient acousto-optic designs in a given medium. The first part of this thesis describes how to measure the elastic-stiffness and photoelastic coefficients of a given crystal. The elastic-stiffness coefficients are essential for designing acousto-optic devices because they determine the velocity, diffraction, and polarization of acoustic waves in a given medium. I used both resonant ultrasound spectroscopy and a modified version of Schaefer-Bergman diffraction to measure elastic coefficients. I discuss in detail the strengths, differences, and similarities of the two experiments. The photoelastic coefficients are necessary for determining the diffraction efficiency of a given acousto-optic geometry. Similar to the elastic coefficients, I employ a modified version of the Schaefer-Bergmann experiment to measure the photoelastic coefficients. I corroborate the measured results with the well established Dixon experiment. The second part of this thesis describes four different graphical representations that help locate practical and efficient acousto-optic designs. I describe in detail each algorithm and how to interpret the calculated results. Several examples are provided for commonly used acosuto-optic materials. The thesis concludes by describing the design and performance of an acousto-optic frequency

  7. Projecting multichannel acousto-optic cells with low crosstalk

    NASA Astrophysics Data System (ADS)

    Kludzin, Victor V.; Kulakov, Sergei V.; Molotok, Victor V.

    1997-09-01

    An acousto-optic method for spectral processing of rf signals is proposed. This method is based on a multichannel cell with frequency separated channels within a given band. The optimum structure of such a system is a multichannel cell with the slow shear mode in the (110) direction in TeO2 and far- axis anisotropic diffraction. A system with 12 channels covering the frequency band of 84 - 96 MHz with the bandwidth of each channel of approximately 0.5 MHz and frequency separation of approximately 1 MHz is experimentally studied. An optical beam which spreads in the plane orthogonal to that of the acousto-optic interaction must be used in this system. The influence of the transducer electrode shape on the acoustic crosstalk in the adjacent channels is studied. The experimental results are in good agreement with the calculated data. The expansion of acousto-optic processing requires that multichannel acousto-cells be used. Narrow-band acousto-optic interaction regimes can be used for frequency-domain filtering of rf signals in multichannel cells. This scheme can be used for the parallel analysis of an rf signal spectrum. This paper describes the process of the design and manufacturing of a multichannel acousto-optic filter for an rf signal with a narrow bandwidth of each channel and estimates its possible parameters. Each channel of the filter is tuned to its own frequency different from those of the adjacent channels within a given overall bandwidth of the whole device.

  8. Growth of Acousto-Optic Crystals for Applications in Infrared Region of Spectrum

    DTIC Science & Technology

    2005-04-30

    Acousto - optic (AO) modulators, deflectors, filters offer convenience, reliability, compact size and fast speed in regulation of optical beams. So far...extremely low acousto - optic figure of merit, which automatically results in high requirements on driving electric power and poor diffraction efficiency. It

  9. Thin-film tunable filters for hyperspectral fluorescence microscopy.

    PubMed

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

    2014-01-01

    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.

  10. Acousto-optic tunable filter (AOTF) imaging spectrometer for NASA applications - System issues

    NASA Technical Reports Server (NTRS)

    Yu, Jeffrey; Chao, Tien H.; Cheng, Li-Jen

    1990-01-01

    A recently developed AOTF operating in the visible, 0.4-0.8 micron bandpass is presently compared with other spectrometer designs, with a view to the advantages it may uniquely offer for prospective NASA missions. Since spectral identification is accomplished by this system through the scanning of a few spectral bands, data storage requirements for spectral image analysis can be significantly reduced. Attention is given to spectral and imaging capabilities and their applicability to defense, remote sensing, and industrial uses.

  11. Acousto-optic tunable filter (AOTF) imaging spectrometer for NASA applications - Breadboard demonstration

    NASA Technical Reports Server (NTRS)

    Chao, Tien-Hsin; Yu, Jeffrey; Cheng, Li-Jen; Lambert, Jim

    1990-01-01

    Considerations of performance criteria in image quality, spectral response, programmability, and field-of-view, are presently discussed for a NASA AOTF system. Experimental data obtained with an AOTF imaging spectrometer breadboard are presented. Attention is given to the identification of Nd(3+) contained in bastanite rock by means of this imaging spectrometer.

  12. Acousto-Optic Imaging Spectrometers for Mars Surface Science

    NASA Technical Reports Server (NTRS)

    Glenar, D. A.; Blaney, D. L.

    2000-01-01

    NASA's long term plan for Mars sample collection and return requires a highly streamlined approach for spectrally characterizing a landing site, documenting the mineralogical make-up of the site and guiding the collections of samples which represent the diversity of the site. Ideally, image data should be acquired at hundreds of VIS and IR wavelengths, in order to separately distinguish numerous anticipated species, using principal component analysis and linear unmixing. Cameras with bore-sighted point spectrometers can acquire spectra of isolated scene elements, but it requires 10(exp 2) to 10(exp 2) successive motions and precise relative pointing knowledge in order to create a single data cube which qualifies as a spectral map. These and other competing science objectives have to be accomplished within very short lander/rover operational lifetime (a few sols). True, 2-D imaging spectroscopy greatly speeds up the data acquisition process, since the spectra of all pixels in the scene are collected at once. This task can be accomplished with cameras that use electronically tunable acousto-optic tunable filters (AOTFs) as the optical tuning element. AOTFs made from TeO2 are now a mature technology, and operate at wavelengths from near-UV to about 5 microns. Because of incremental improvements in the last few years, present generation devices are rugged, radiation-hard and operate at temperatures down to at least 150K so they can be safely integrated into the ambient temperature optics of in-situ instruments such as planetary or small-body landers. They have been used for ground-based astronomy, and were also baselined for the ST-4 Champollion IR comet lander experiment (CIRCLE), prior to cancellation of the ST-4 mission last year. AIMS (for Acousto-optic Imaging spectrometer), is a prototype lander instrument which is being built at GSFC with support by the NASA OSS Advanced Technologies and Mission Studies, Mars Instrument Definition and Development Program (MIDP

  13. Acousto-Optic Adaptive Processing (AOAP).

    DTIC Science & Technology

    1983-12-01

    I ~.sls Phe Report December 1963 •- ACOUSTO - OPTIC ADAPTIVE <PROCESSING (AOAP) General Electric Company W. A. Penn, D. R. Morgan, A. Aridgides and M. L...numnber) Optical signal processing Acousto - optical modulators Adaptive signal processing - Adaptive sidelobe cancellation 20. ABSTRACT (Contnue an...required operations of multiplication and time delay are provided by acousto - optical (AO) delay lines. The required time integraticO is provided by

  14. Wideband Waveguide Acousto-Optic Bragg Cell.

    DTIC Science & Technology

    The results of an effort to improve the performance specifications of acousto - optic Bragg cells are reported. Various configurations of multiple...would provide a 700 MHz acousto - optic bandwidth. Investigated were Bragg cells fabricated on Ti diffused LiNb03 waveguides as well as Ti diffused LiNb03

  15. Experimental Investigation of Acousto-Optic Communications

    DTIC Science & Technology

    2003-09-01

    acousto - optic sensor shows promise as a means for detecting acoustic data projected towards the water surface from a submerged platform. The laser...simulation studies were conducted to demonstrate acousto - optic sensor feasibility for obtaining robust recordings of acoustic communication signals across

  16. Acousto-optic effect in random media

    NASA Astrophysics Data System (ADS)

    Hoskins, Jeremy G.; Schotland, John C.

    2017-03-01

    We consider the acousto-optic effect in a random medium. We derive the radiative transport equations that describe the propagation of multiply scattered light in a medium whose dielectric permittivity is modulated by an acoustic wave. Using this result, we present an analysis of the sensitivity of an acousto-optic measurement to the presence of a small absorbing inhomogeneity.

  17. Optically tunable optical filter

    NASA Astrophysics Data System (ADS)

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

    1995-12-01

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

  18. AIMS: Acousto-optic imaging spectrometer for spectral mapping of solid surfaces

    NASA Astrophysics Data System (ADS)

    Glenar, David A.; Blaney, Diana L.; Hillman, John J.

    2003-01-01

    A compact, two-channel acousto-optic tunable filter (AOTF) camera is being built at GSFC as a candidate payload instrument for future Mars landers or small-body rendezvous missions. This effort is supported by the NASA Mars Instrument Development Program (MIDP), Office of Space Science Advanced Technologies and Mission Studies. Acousto-optic Imaging Spectrometer (AIMS) is electronically programmable and provides arbitrary spatial and spectral selection from 0.48 to 2.4 μm. The geometric throughput of AOTF's are well matched to the requirements for lander mounted cameras since (I) they can be made very compact, (II) "slow" (f/14-f/18) optics required for large depth-of-field fall well within the angular aperture limit of AOTF's, and (III) they operate at low ambient temperatures. A breadboard of the AIMS short-wavelength channel is now being used for spectral imaging of high-interest Mars analog materials (iron oxides, carbonates, sulfates and sedimentary basalts) as part of the initial instrument validation exercises.

  19. Investigation of a mercurous chloride acousto-optic cell based on longitudinal acoustic mode.

    PubMed

    Gupta, Neelam

    2009-03-01

    A number of spectral imagers using acousto-optic tunable filters (AOTFs) operating from the UV to the longwave infrared (LWIR) using KDP, MgF(2), TeO(2), and Tl(3)AsSe(3) crystals to cover different spectral regions have been developed. In the LWIR there is a lack of high quality acousto-optic (AO) materials. Mercurous halide (Hg(2)Cl(2) and Hg(2)Br(2)) crystals are highly anisotropic with a high AO figure of merit due to slow acoustic velocities and high photoelastic constants and are transparent over a wide spectral region from 0.35 to 20 mum for Hg(2)Cl(2) and from 0.4 to 30 mum for Hg(2)Br(2). AO modulators, deflectors, and AOTFs based on these crystals can operate over a wide spectral range. Single crystals of these materials are being grown and some prototype devices have been fabricated. Results are presented from device characterization for an AO cell fabricated in Hg(2)Cl(2) based on longitudinal acoustic mode propagation. This device was very useful in demonstrating the AO interaction as well as soundness of the transducer bonding technique. Acoustic phase velocity is calculated and measured, diffraction efficiency is obtained from experiments, and the AO figure of merit of the sample is evaluated.

  20. Tunable Microwave Transversal Filters.

    DTIC Science & Technology

    1984-05-01

    GOVT ACCESSION NO. 3. RECIPIENT’S CATALOG NUMBER AFOSR-TR. 84-0977 S4. TI TLE (and Subtitle) 5. TYP ?FE&T&PEO OEE U!NABLE MICROWAVE TRANSVERSAL FILTERS...this goal through magnetostatic waves MSW propagating at microwave frequency in magnetically biased, liquid phase epitaxial films of yttrium iron...garnet (YIG) grown on gadolinium gallium garnet (GGG). This technology has a number of advantages; low loss (greater than 30db/usec at xband), tunable by

  1. Acousto-Optic Beam Steering Study

    DTIC Science & Technology

    1994-08-01

    8217111 INK $ 1 1 illl iII Ill i, R L-TR-94-121 !1!1Il t 11I1!I!11! ilI, / Final Technical Report August 1994 ACOUSTO - OPTIC BEAM STEERING STUDY Harris...contractual obligations or notices on a specific document require that it be returned. For i ..........I ,, ACOUSTO - OPTIC BEAM STEERING STUDY H. W...4. TITLE AND SUBTITLE 5. FUNDING NUMBERS ACOUSTO - OPTIC BEAM STEERING STUDY C - F30602-91-C-0131 PE - 63215C 6. AUTHOR(S) PR - 1405 TA - 02 H. W

  2. Acousto-optic control of the LPG spectrum for sensing applications

    NASA Astrophysics Data System (ADS)

    Oliveira, Roberson A.; Possetti, Gustavo R. C.; Marques, Carlos A. F.; Neves, Paulo T., Jr.; Bavastri, Carlos A.; Kamikawachi, Ricardo C.; Fabris, José L.; Muller, Marcia; Nogueira, Rogério N.; Canning, John; Pohl, Alexandre A. P.

    2011-05-01

    Experimental and numerical demonstration of the acousto-optic effect applied in long period grating by means of flexural waves is presented. The interaction between acoustic and optical waves is modeled with help of the method of assumed modes, which delivers the strain field inside the grating and the transfer matrix method, which, given the strain field as input, calculate the resultant grating spectrum. The experimental and theoretical results are found to be in good agreement. The main effect of the bends in the grating is the break of degeneracy of the circular cladding modes, leading the attenuation band to be changed. Among all the applications of this methodology, it is important to mention the possibility of use as a tunable filter, laser cavity gain controller, switching device and transducer in sensing systems.

  3. Wavelet transform: fundamentals, applications, and implementation using acousto-optic correlators

    NASA Astrophysics Data System (ADS)

    DeCusatis, Casimer M.; Koay, J.; Litynski, Daniel M.; Das, Pankaj K.

    1995-10-01

    In recent years there has been a great deal of interest in the use of wavelets to supplement or replace conventional Fourier transform signal processing. This paper provides a review of wavelet transforms for signal processing applications, and discusses several emerging applications which benefit from the advantages of wavelets. The wavelet transform can be implemented as an acousto-optic correlator; perfect reconstruction of digital signals may also be achieved using acousto-optic finite impulse response filter banks. Acousto-optic image correlators are discussed as a potential implementation of the wavelet transform, since a 1D wavelet filter bank may be encoded as a 2D image. We discuss applications of the wavelet transform including nondestructive testing of materials, biomedical applications in the analysis of EEG signals, and interference excision in spread spectrum communication systems. Computer simulations and experimental results for these applications are also provided.

  4. Acousto-optic spectrometer for radio astronomy

    NASA Technical Reports Server (NTRS)

    Chin, G.; Buhl, D.; Florez, J. M.

    1980-01-01

    A prototype acousto-optic spectrometer which uses a discrete bulk acoustic wave Itek Bragg cell, 5 mW Helium Neon laser, and a 1024 element Reticon charge coupled photodiode array is described. The analog signals from the photodiode array are digitized, added, and stored in a very high speed custom built multiplexer board which allows synchronous detection of weak signals to be performed. The experiment is controlled and the data are displayed and stored with an LSI-2 microcomputer system with dual floppy discs. The performance of the prototype acousto-optic spectrometer obtained from initial tests is reported.

  5. Improving the signal-to-noise ratio of the beat note between a frequency comb and a tunable laser using a dynamically tracking optical filter.

    PubMed

    Bergeron, Hugo; Deschênes, Jean-Daniel; Genest, Jérôme

    2016-09-15

    An acousto-optic filter is locked to a tunable continuous wave (CW) laser so that a frequency comb can be dynamically filtered around the wavelength of the CW source. The signal-to-noise ratio (SNR) of the heterodyne beat note between the comb and the CW laser is improved by a factor of up to 19 dB. Furthermore, a SNR of more than 56 dB in 100 kHz is obtained over an 85 nm wavelength span. This technique could enable wideband, agile, and cycle-slip-free phase tracking of a beat note across a full comb spectrum.

  6. Electrothermally tunable MEMS filters

    NASA Astrophysics Data System (ADS)

    Prasad, A. V. S. S.; K. P., Venkatesh; Bhat, Navakanta; Pratap, Rudra

    2014-03-01

    MEMS resonators have potential application in the area of frequency selective devices (e.g., gyroscopes, mass sensors, etc.). In this paper, design of electro thermally tunable resonators is presented. SOIMUMPs process is used to fabricate resonators with springs (beams) and a central mass. When voltage is applied, due to joule heating, temperature of the conducting beams goes up. This results in increase of electrical resistance due to mobility degradation. Due to increase in the temperature, springs start softening and therefore the fundamental frequency decreases. So for a given structure, one can modify the original fundamental frequency by changing the applied voltage. Coupled thermal effects result in non-uniform heating. It is observed from measurements and simulations that some parts of the beam become very hot and therefore soften more. Consequently, at higher voltages, the structure (equivalent to a single resonator) behaves like coupled resonators and exhibits peak splitting. In this mode, the given resonator can be used as a band rejection filter. This process is reversible and repeatable. For the designed structure, it is experimentally shown that by varying the voltage from 1 to 16V, the resonant frequency could be changed by 28%.

  7. Ultrasonic power measurement system based on acousto-optic interaction

    NASA Astrophysics Data System (ADS)

    He, Liping; Zhu, Fulong; Chen, Yanming; Duan, Ke; Lin, Xinxin; Pan, Yongjun; Tao, Jiaquan

    2016-05-01

    Ultrasonic waves are widely used, with applications including the medical, military, and chemical fields. However, there are currently no effective methods for ultrasonic power measurement. Previously, ultrasonic power measurement has been reliant on mechanical methods such as hydrophones and radiation force balances. This paper deals with ultrasonic power measurement based on an unconventional method: acousto-optic interaction. Compared with mechanical methods, the optical method has a greater ability to resist interference and also has reduced environmental requirements. Therefore, this paper begins with an experimental determination of the acoustic power in water contained in a glass tank using a set of optical devices. Because the light intensity of the diffraction image generated by acousto-optic interaction contains the required ultrasonic power information, specific software was written to extract the light intensity information from the image through a combination of filtering, binarization, contour extraction, and other image processing operations. The power value can then be obtained rapidly by processing the diffraction image using a computer. The results of this work show that the optical method offers advantages that include accuracy, speed, and a noncontact measurement method.

  8. Feedback and Acousto Optic Isolation Effects on Laser Stability.

    DTIC Science & Technology

    1977-03-01

    This paper analyzes the effect of optical feedback on laser frequency stability and the acousto optic isolator concept, which was demonstrated...nonlinearity such as saturation in the laser medium. The analysis mathematically corroborates the initial acousto optic isolator concept and the...limited experimental data available. In the study of the acousto optic isolator, it was determined that an acceptable analytic expression for the

  9. Tunable acoustical optical filter

    NASA Technical Reports Server (NTRS)

    Lane, A. L.

    1977-01-01

    Solid state filter with active crystal element increases sensitivity and resolution of passive and active spectrometers. Filter is capable of ranging through infrared and visible spectra, can be built as portable device for field use, and is suitable for ecological surveying, for pollution detection, and for pollutant classification.

  10. Scheme for Terminal Guidance Utilizing Acousto-Optic Correlator.

    DTIC Science & Technology

    longitudinally extending acousto - optic device as index of refraction variation pattern signals. Real time signals corresponding to the scene actually being viewed...by the vehicle are propagated across the stored signals, and the results of an acousto - optic correlation are utilized to determine X and Y error

  11. Signal Coherence Recovery Using Acousto-Optic Fourier Transform Architectures

    DTIC Science & Technology

    1990-06-14

    processing of data in ground- and space-based applications. We have implemented a prototype one-dimensional time-integrating acousto - optic (AO) Fourier...theory of optimum coherence recovery (CR) applicable in computation-limited environments. We have demonstrated direct acousto - optic implementation of CR

  12. Passive long range acousto-optic sensor

    NASA Astrophysics Data System (ADS)

    Slater, Dan

    2006-08-01

    Alexander Graham Bell's photophone of 1880 was a simple free space optical communication device that used the sun to illuminate a reflective acoustic diaphragm. A selenium photocell located 213 m (700 ft) away converted the acoustically modulated light beam back into sound. A variation of the photophone is presented here that uses naturally formed free space acousto-optic communications links to provide passive multichannel long range acoustic sensing. This system, called RAS (remote acoustic sensor), functions as a long range microphone with a demonstrated range in excess of 40 km (25 miles).

  13. Acousto-optic devices for operation with 2μm fibre lasers

    NASA Astrophysics Data System (ADS)

    Ward, J. D.; Stevens, G.; Shardlow, P. C.

    2016-03-01

    Fibre lasers operating in the 2μm region are of increasing interest for a range of applications, including laser machining and biomedical systems. The large mode area compared to 1μm fibre lasers combined with operation in an "eye-safe" region of the spectrum makes them particularly attractive. When developing fibre lasers at 1μm and 1·5μm manufacturers were able to call upon enabling technologies used by the telecoms industry, but at longer wavelengths, including 2μm, many such components are either unavailable or immature. We report on recent developments of Acousto-Optic Modulators and Tunable Filters that are specifically optimised for use with fibre systems operating at or around 2μm. AO devices are interesting due to their ability to conserve spatial-coherence, making them appropriate for use with single-mode optical fibres. We describe how the choice of interaction medium is an important consideration, particularly affecting the drive power and the polarisation behaviour of the device - the latter being an important parameter when used in a fibre system. We also describe two designs of AO Tunable Filter intended for laser tuning. Both designs have been demonstrated intracavity in 2μm fibre lasers. The first gives exceptionally narrow resolution (δλ/λ<0·1%). The second design is of a novel type of AOTF where a matched pair of AOTFs is configured to give a substantially net zero frequency-shift with little or no loss of pointing stability, any minor deviations in manufacture being self-compensated. Furthermore, small controlled frequency-shifts (up to about 10kHz) may be introduced with little or no detriment to the alignment of the system.

  14. Acousto-Optic Beam Sampler, Part 2. Green’s Function Solution to Acousto-Optic Interaction Problem.

    DTIC Science & Technology

    This part of the ’ Acousto - Optic Beam Sampler,’ series lays down the formalism behind the Green’s function integral approach to solving the acousto ... optic scattering problem. The advantage of this formulation which is applicable to gases is shown through developing the solution to the scattering

  15. Pre-Juno Optical Analysis of Jupiter's Atmosphere with the NMSU Acousto-optic Imaging Camera

    NASA Astrophysics Data System (ADS)

    Dahl, Emma; Chanover, Nancy J.; Voelz, David; Kuehn, David M.; Strycker, Paul D.

    2016-10-01

    Jupiter's upper atmosphere is a highly dynamic system in which clouds and storms change color, shape, and size on variable timescales. The exact mechanism by which the deep atmosphere affects these changes in the uppermost cloud deck is still unknown. With Juno's arrival at Jupiter in July 2016, the thermal radiation from the deep atmosphere will be measurable with the spacecraft's Microwave Radiometer. By taking detailed optical measurements of Jupiter's uppermost cloud deck in conjunction with Juno's microwave observations, we can provide a context in which to better understand these observations. This data will also provide a complement to the near-IR sensitivity of the Jovian InfraRed Auroral Mapper and will expand on the limited spectral coverage of JunoCam. Ultimately, we can utilize the two complementary datasets in order to thoroughly characterize Jupiter's atmosphere in terms of its vertical cloud structure, color distribution, and dynamical state throughout the Juno era. In order to obtain high spectral resolution images of Jupiter's atmosphere in the optical regime, we use the New Mexico State University Acousto-optic Imaging Camera (NAIC). NAIC contains an acousto-optic tunable filter, which allows us to take hyperspectral image cubes of Jupiter from 450-950 nm at an average spectral resolution (λ/dλ) of 242. We present an analysis of our pre-Juno dataset obtained with NAIC at the Apache Point Observatory 3.5-m telescope during the night of March 28, 2016. Under primarily photometric conditions, we obtained 6 hyperspectral image cubes of Jupiter over the course of the night, totaling approximately 2,960 images. From these data we derive low-resolution optical spectra of the Great Red Spot and a representative belt and zone to compare with previous work and laboratory measurements of candidate chromophore materials. Future work will focus on radiative transfer modeling to elucidate the Jovian cloud structure during the Juno era. This work was supported

  16. Designing an acousto-optical spectrometer for Guillermo Haro Astrophysical Observatory

    NASA Astrophysics Data System (ADS)

    Shcherbakov, Alexandre S.; Arellanes Bernabe, Adan Omar; Chavushyan, Vahram

    2013-09-01

    The Guillermo Haro astrophysical observatory (Mexico) realizes investigations in the visible and near-infrared range . Actually, the classical grating spectrometer with mechanically removable optical filters and diffraction gratings is exploited there. Unfortunately, the regular process of changing the diffraction gratings with different resolutions and recalibrating the spectrometer is inconvenient and wastes expensive time for observations. This is why exploiting an acousto-optical cell as a dynamic dispersive element is practically desirable, because potentially it realizes tuning the spectral resolution and the range of observation electronically and excludes filters. Some aspects of inserting just one dynamic acousto-optical diffraction grating instead of a set of the traditional static diffraction gratings are preliminarily considered.

  17. Physical basis of Acousto-Optical Imaging

    NASA Astrophysics Data System (ADS)

    Jarrett, Christopher W.

    Acousto-Optical Imaging (AOI) is an emerging hybrid multi-modal imaging technique that combines the high spatial resolution of ultrasound with the versatile molecular sensitivity of optical detection to improve upon the limited spatial resolution of purely optical techniques. However, the precise mechanisms that contribute to the contrast in AOI have been relatively little explored, and the influence of several physical factors are not well understood. Kobayashi et al. previously reported observations of modulated fluorescence capable of locating fluorescent regions of interest within turbid media, suggesting the ability to use incoherent light for AOI. This research aimed to develop and extend such an approach for applications in biomedical imaging. We aimed to demonstrate the modulation of incoherent light by ultrasound and investigate what factors affect the magnitude of such effects. We proposed the following specific aims: (1) To design and develop instrumentation to detect and quantify Acousto-Optical interactions; (2) To evaluate the contributions of different mechanisms of ultrasonic modulation of fluorescence and the factors that influence these effects in turbid media like tissues; (3) To test a variety of fluorescent contrast agents to determine if their light output may be directly affected by ultrasonic modulation, which would suggest a novel approach to AOI. This work achieved these aim. We were successful in designing and developing an experimental apparatus capable of detecting and quantifying Acousto-Optical Interactions. We determined this signal scales linearly with squared ultrasound pressure but unlike the interpretation of Kobayashi et al., we found the apparent modulated fluorescence is dominated by acoustic modulation of the excitation light. In addition, we report a novel finding that ultrasound can modulate incoherent light via modulation of tissue absorption and density, incidentally providing a new way to image sound fields. Lastly, we

  18. Tunable-Bandwidth Filter System

    NASA Technical Reports Server (NTRS)

    Bailey, John W.

    2004-01-01

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

  19. Tunable-Bandwidth Filter System

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

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

  20. A Compact Bulk Acousto-Optic Time Integrating Correlator.

    DTIC Science & Technology

    1984-11-01

    AD-A156 668 A COMPACT BULK ACOUSTO - OPTIC TIME INTEGRATING 1/1 CORRELATOR(U) ELECTRONICS RESEARCH LAB ADELAIDE (AUSTRALIA) D A FOGG NOV 84 ERL-9323-TR...DEFENCE RESEARCH CENTRE SALISBURY SOUTH AUSTRALIA TECHNICAL REPORT ER L-0323-TR A COMPACT BULK ACOUSTO - OPTIC TIME INTEGRATING CORRELATOR D.A.B. FOGG...LABORATORY TECHNICAL REPORT ERL-0323-TR A COMPACT BULK ACOUSTO - OPTIC TIME INTEGRATING CORRELATOR D.A.B. Fogg SUMMARY This report describes the design and

  1. Modeling the noise figure of an acousto-optic receiver

    NASA Astrophysics Data System (ADS)

    Ristic, V. M.; Lee, J. P. Y.

    1996-02-01

    By defining the processing gain of an acousto-optic receiver as the ratio of the signal-to-noise ratio at the output of the detector to the signal-to-noise ratio of the intermediate-frequency input, one can model a noise figure for the acousto-optic receiver. The noise figure has a minimum of 0 dB and depends on the ratio of the noise power (internal to the acousto-optic cell) to the intermediate-frequency input noise power multiplied by the frequency and the spatially dependent exponential factor.

  2. Frequency Resolution of an Acousto-Optical Spectrometer

    DTIC Science & Technology

    1993-08-03

    AD-A267 822 FOREIGN AEROSPACE SCIENCE AND TECHNOLOGY CENTER DTIC S ELECTE AUG 111993 D FREQUENCY RESOLUTION OF AN ACOUSTO - OPTICAL SPECTROMETER by... D ~t• i,5"t~o’• A i +’- 1 Av.:+l +,O ,J Dist Avi! .. DTIC QUALITY I1V’PEMTED 3 FREQUENCY RESOLUTION OF AN ACOUSTO - OPTICAL SPECTROMETER... optical spectrometer (AOS) system as affected by the acousto - optical deflector and the coherent light beam truncation ratio, and examines the response

  3. Tunable Optical Filters for Space Exploration

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

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

  4. Acousto-Optics as an Efficient Method for Physical Measurements

    NASA Astrophysics Data System (ADS)

    Kulakov, Sergei V.; Balysheva, Olga L.; Zhdanov, Arcenii Yu.; Kludzin, Victor V.; Shakin, Oleg V.

    In addition to acousto-optic information processing and manufacturing of such devices, the interaction between optical and acoustic waves are an efficient method for physical measurements. The paper analyses the potential of the acousto-optic method for measurement and investigation of crystal properties. It also presents some examples of this method applied to such measurements and investigations. The acousto-optic implementation of the pulse-phase method is used for acoustic velocity measurements. Velocities in an arbitrary directions can be measured using the Shaefer-Bergman method (the visualization of the angular distribution of the inverse phase velocities) together with the pulse-phase method. The matrices of crystal elastic coefficients can be evaluated using the Shaefer-Bergman patterns, using the minimum number of tested samples. The Schlieren (shadow) image method can give information both on the characteristics of acoustic and optical fields. The acousto-optic interaction is Efficient Method for determination of elastic material nonlinearity parameters.

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

    NASA Astrophysics Data System (ADS)

    Turner, John Frederick, II

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

  6. Laser-Based Acousto-Optic Uplink Communications Technique

    DTIC Science & Technology

    2003-08-18

    An apparatus for enabling acousto - optic communication comprising an in-water platform comprising means for emitting an acoustic signal to an acousto ...portion of the first interrogation beam and a second laser beam formed from the reflection of the first interrogation beam off of the acousto - optic interaction... optic interaction zone, an in-air platform comprising the ability for transmitting a first optical interrogation beam, the ability for receiving a

  7. Wavelength-swept fiber laser based on acousto-optic tuning method

    NASA Astrophysics Data System (ADS)

    Chen, Ming-hui; Fan, Yun-ping; Zhang, Hao; Tao, Jian-feng; Zheng, Gang

    2016-10-01

    In this study, we have demonstrated a wavelength-swept fiber laser based on an acousto-optic tunable filter(AOTF) as a selective element and a semiconductor optical amplifier(SOA) as a gain medium in an internal fiber ring cavity. The light deriving from one port of the SOA goes through an optical isolator, the AOTF, a fiber coupler and a polarized controller successively, then it goes back to the other port of the SOA to form a ring cavity. The laser output is from another port of the fiber coupler. The laser made by this method is mainly used for swept-source optical coherence tomography(SS-OCT). The application of the SOA provides a sufficiently broad range and can ensure an increased axial resolution of SS-OCT. AOTF offers a wide tuning range, high switching speed and stable operation against vibration for the non-mechanical structure. The proposed wavelength-swept fiber laser ensures a high axial resolution of tomographic images and has a stable laser output. We have discussed the influence of the SOA injection current to the tuning range of the laser. In the SOA injection current of 280 mA, a continuous wavelength tuning range from 1295 to 1370 nm centered at a wavelength of 1330nm is obtained at the sweep rate of 1.06 kHz, and the power of the swept source was 1.14 mW. In addition, for quantitative characterization of the wavelength-swept performance with a AOTF, we have theoretically and experimentally analyzed the influence of the following controllable parameters: injection current, output power and sweeping frequency.

  8. Acousto-optical properties of metamaterials

    SciTech Connect

    Pustovoit, V I

    2016-02-28

    The possibility of the effective use of metamaterials in acousto-optics is demonstrated. It is shown that photoelastic constants that determine a change in the dielectric constant of a heterogeneous medium under the action of a sound wave can significantly exceed the corresponding constants for conventional crystals. We have analysed the mechanisms of the dielectric constant variation in a heterogeneous medium consisting of nanoparticles in the form of ellipsoids and have found explicitly the values of the photoelastic constants. It is shown that the mechanism of the dielectric constant variation in a longitudinal sound wave is reduced to a change in the local concentration of nanoparticles in the bulk and in a transverse acoustic wave – to a local rotation of space-oriented nanoellipsoids. It is also shown that the use of metamedia with a nonuniform distribution of nanoparticles provides a unique opportunity for designing qualitatively new instruments and devices that cannot be produced on the basis of conventional crystals. It is noted that metamaterials open ample opportunities for creating devices of the IR region of the spectrum due to the absence of restrictions on the size of such media. (metamaterials)

  9. A new multifunction acousto-optic signal processor

    NASA Technical Reports Server (NTRS)

    Berg, N. J.; Casseday, M. W.; Filipov, A. N.; Pellegrino, J. M.

    1984-01-01

    An acousto-optic architecture for simultaneously obtaining time integration correlation and high-speed power spectrum analysis was constructed using commercially available TeO2 modulators and photodiode detector-arrays. The correlator section of the processor uses coherent interferometry to attain maximum bandwidth and dynamic range while achieving a time-bandwidth product of 1 million. Two correllator outputs are achieved in this system configuration. One is optically filtered and magnified 2 : 1 to decrease the spatial frequency to a level where a 25-MHz bandwidth may be sampled by a 62-mm array with elements on 25-micro centers. The other output is magnified by a factor of 10 such that the center 4 microseconds of information is available for estimation of time-difference-of-arrival to within 10 ns. The Bragg cell spectrum-analyzer section, which also has two outputs, resolves a 25-MHz instantaneous bandwidth to 25 kHz and can determine discrete-frequency reception time to within 15 microseconds. A microprocessor combines spectrum analysis information with that obtained from the correlator.

  10. Acousto-optic mode coupling excited by flexural waves in simplified hollow-core photonic crystal fibers

    NASA Astrophysics Data System (ADS)

    Zhang, Hao; Qiu, Minghui; Wu, Zhifang; Dong, Hongguang; Liu, Bo; Miao, Yinping

    2013-05-01

    We have demonstrated the formation of an acoustic grating in a simplified hollow-core photonic crystal fiber, which consists of a hollow hexagonal core and six crown-like air holes, by applying flexural acoustic waves along the fiber axis. The dependence of the resonance wavelength on the applied acoustic frequency has been acquired on the basis of the theoretical calculation of the phase matching curve; it is in good agreement with our experimental observation of the transmission spectral evolution as the applied acoustic frequency varies. Experimental results show that the acoustic grating resonance peak possesses acoustic frequency and strain dependences of 728 nm MHz-1 and -6.98 pm μɛ-1, respectively, based on which high-performance acousto-optic tunable filters and fiber-optic strain sensors with high sensitivity could be achieved. And furthermore, the research work presented in this paper indicates that microbending rather than physical deformation is the main physical mechanism that leads to the formation of equivalent long-period gratings, which would be of significance for developing related grating devices based on simplified hollow-core photonic crystal fibers.

  11. Theory and Experiment Analysis of Two-Dimensional Acousto-Optic Interaction.

    DTIC Science & Technology

    1995-01-03

    The universal coupled wave equation of two dimensional acousto optic effect has been deduced and the solution of normal Raman-Hath acousto optic diffraction...was derived from it. The theory was compared with the experimental results of a two dimensional acousto optic device consisting of two one dimensional modulators. The experiment results agree with the theory. (AN)

  12. Acousto-optics of liquid crystals: Yesterday, today, and tomorrow

    NASA Astrophysics Data System (ADS)

    Kapustina, O. A.

    2014-09-01

    The most important results of the recent theoretical and experimental studies in the field of acousto-optics of liquid crystals (LCs) in research lines initiated by the pioneering studies of Professor A.P. Kapustin at the Institute of Crystallography of the Russian Academy of Sciences and carried out at the Acoustic Institute of the Russian Academy of Sciences are generalized and analyzed. These lines include the study of the nature of acoustically induced supramolecular structures in nematic liquid crystals (NLCs) and cholesteric liquid crystals (CLCs) and the development of physical bases of practical LC acousto-optics, related to the detection of acoustic signals.

  13. Application of acousto-optic actuator applied in holographic system

    NASA Astrophysics Data System (ADS)

    Ling, FuRi; Wang, Biao

    2002-09-01

    In this paper, we discuss acousto-optical scanning and deflection, and design an acousto-optical actuator for steering the laser beam in the direction of vertical and horizon. In this system a laser whose wavelength is 532 nm is used and is expanded by a cylindrical lens. This horizontal actuator produces the horizontal deflection and the spherical lens following the horizontal actuator rotates the beam to match the aperture of the vertical actuator. The cylindrical lens restores the beam to its original circular cross-section, after which the microscope optics brings it to a focus in the lithium niobate crystal in which we store information.

  14. Holographic topography using acousto-optically generated large synthetic wavelengths

    NASA Astrophysics Data System (ADS)

    Abeywickrema, U.; Beamer, D.; Banerjee, P.; Poon, T.-C.

    2016-03-01

    Digital holography uses phase imaging in a variety of techniques to produce a three-dimensional phase resolved image that includes accurate depth information about the object of interest. Multi-wavelength digital holography is an accurate method for measuring the topography of surfaces. Typically, the object phases are reconstructed for two wavelengths separately and the phase corresponding to the synthetic wavelength (obtained from the two wavelengths) is obtained by calculating the phase difference. Then the surface map can be obtained using proper phase-unwrapping techniques. Usually these synthetic wavelengths are on the order of microns which can be used to resolve depths on the order of microns. In this work, two extremely close wavelengths generated by an acousto-optic modulator (AOM) are used to perform two-wavelength digital holography. Since the difference between the two wavelengths is on the order of picometers, a large synthetic wavelength (on the order of centimeters) can be obtained which can be used to determine the topography of macroscopic surface features. Also since the synthetic wavelength is large, an accurate surface map can be obtained without using a phase-unwrapping technique. A 514 nm Argon-ion laser is used as the optical source, and used with an AOM to generate the zeroth-order and frequency-shifted first-order diffracted orders which are used as the two wavelengths. Both beams are aligned through the same spatial filter assembly. Holograms are captured sequentially using a typical Mach-Zehnder interferometric setup by blocking one beam at a time. Limitations of the large synthetic wavelength are also discussed.

  15. Designing the acousto-optical cell for optical spectrometer incorporated into the Guillermo Haro Astrophysical Observatory

    NASA Astrophysics Data System (ADS)

    Shcherbakov, Alexandre S.; Arellanes Bernabe, Adan Omar; Chavushyan, Vahram

    2013-09-01

    Optical spectrometer of the Guillermo Haro astrophysical observatory (Mexico) exploits mechanically removable traditional static diffraction gratings as dispersive elements. There is a set of the static gratings with the slit-density 50 - 600 lines/mm and optical apertures 9 cm x 9 cm that provide the first order spectral resolution from 9.6 to 0.8 A/pixel, respectively, in the range 400 - 1000 nm. However, the needed mechanical manipulations, namely, replacing the static diffraction gratings with various resolutions and following recalibration of spectrometer within studying even the same object are inconvenient and lead to losing rather expensive observation time. We suggest exploiting an acousto-optical cell, i.e. the dynamic diffraction grating tunable electronically, as dispersive element in that spectrometer. Involving the acousto-optical technique, which can potentially provide electronic control over the spectral resolution and the range of observations, leads to possible eliminating the above-mentioned demerits and to improving the efficiency of analysis.

  16. Actively mode-locked fiber ring laser by intermodal acousto-optic modulation.

    PubMed

    Bello-Jiménez, M; Cuadrado-Laborde, C; Sáez-Rodríguez, D; Diez, A; Cruz, J L; Andrés, M V

    2010-11-15

    We report an actively mode-locked fiber ring laser. A simple and low-insertion-loss acousto-optic modulator driven by standing flexural waves, which couples core-to-cladding modes in a standard single-mode optical fiber, is used as an active mechanism for mode locking. Among the remarkable features of the modulator, we mention its high modulation depth (72%), broad bandwidth (187 GHz), easy tunability in the optical wavelength, and low insertion losses (0.7 dB). The narrowest optical pulses obtained were of 95 ps time width, 21 mW peak power, repetition rate of 4.758 MHz, and 110 mW of pump power.

  17. External cavity quantum cascade lasers with ultra rapid acousto-optic tuning

    SciTech Connect

    Lyakh, A. Barron-Jimenez, R.; Dunayevskiy, I.; Go, R.; Patel, C. Kumar N.

    2015-04-06

    We report operation of tunable external cavity quantum cascade lasers with emission wavelength controlled by an acousto-optic modulator (AOM). A long-wave infrared quantum cascade laser wavelength tuned from ∼8.5 μm to ∼9.8 μm when the AOM frequency was changed from ∼41MHz to ∼49 MHz. The laser delivered over 350 mW of average power at the center of the tuning curve in a linewidth of ∼4.7 cm{sup −1}. Measured wavelength switching time between any two wavelengths within the tuning range of the QCL was less than 1 μs. Spectral measurements of infrared absorption features of Freon demonstrated a capability of obtaining complete spectral data in less than 20 μs.

  18. Acousto-optic laser projection systems for displaying TV information

    SciTech Connect

    Gulyaev, Yu V; Kazaryan, M A; Mokrushin, Yu M; Shakin, O V

    2015-04-30

    This review addresses various approaches to television projection imaging on large screens using lasers. Results are presented of theoretical and experimental studies of an acousto-optic projection system operating on the principle of projecting an image of an entire amplitude-modulated television line in a single laser pulse. We consider characteristic features of image formation in such a system and the requirements for its individual components. Particular attention is paid to nonlinear distortions of the image signal, which show up most severely at low modulation signal frequencies. We discuss the feasibility of improving the process efficiency and image quality using acousto-optic modulators and pulsed lasers. Real-time projectors with pulsed line imaging can be used for controlling high-intensity laser radiation. (review)

  19. Electro-optic and Acousto-optic Laser Beam Scanners

    NASA Astrophysics Data System (ADS)

    Römer, G. R. B. E.; Bechtold, P.

    Optical solid state deflectors rely on the electro-optical or acousto-optic effect. These Electro-Optical Deflectors (EODs) and Acousto-Optical Deflectors (AODs) do not contain moving parts and therefore exhibit high deflection velocities and are free of drawbacks associated with mechanical scanners. A description of the principles of operation of EODs and AODs is presented. In addition, characteristics, properties and the (dis)advantages of EODs and AODs, when compared to mirror based mechanical deflectors, is discussed. Deflection angles, speed and accuracy are discussed in terms of resolvable spots and related quantities. Also, response time, damage threshold, efficiency and the type and magnitude of beam distortions is addressed. Optical deflectors are characterized by high angular deflection velocities, but small deflection angles. Whereas mechanical mechanical scanners are characterized by relatively small deflection velocities, but large deflection angles. Arranging an optical deflector and a mechanical scanner in series allows to take advantage of the best of both worlds.

  20. Bending effect on fiber acousto-optic mode coupling.

    PubMed

    Zhao, Jianhui; Liu, Xiaoming; Wang, Yan; Luo, Ye

    2005-08-20

    The acousto-optic effect in a bent fiber is studied experimentally and numerically by using the scalar finite-element method. The resulting transmission spectra show that new mode-coupling peaks appear due to the breaking of the mode spatial symmetry. The strength of new peaks increases as the fiber-bending curvature increases with a redshift or blueshift in wavelength, strongly depending on the orientation of fiber bending with respect to the acoustic-wave vibration direction.

  1. High-efficiency acousto-optic coupling in phoxonic resonator based on silicon fishbone nanobeam cavity.

    PubMed

    Chiu, Chien-Chang; Chen, Wei-Min; Sung, Kuen-Wei; Hsiao, Fu-Li

    2017-03-20

    We investigate the acousto-optic coupling rates between different acoustic resonance modes and a specified optical resonance mode in a one-dimensional phoxonic crystal fishbone nanobeam formed by periodically arranging semi-cylinders of air on both sides of a suspended silicon waveguide. The gradually tapered unit cells form optical and acoustic resonators. In acousto-optic coupling rate calculation, the acoustic fields and optical fields are obtained by steady state monochromatic analysis and eigen-mode computation, respectively. Results showed that the acoustic polarizations and symmetries of the acoustic resonance modes are dominant factors in the acousto-optic coupling efficiency, and appropriate selection of these parameters can prevent cancellation of acousto-optic interactions, thereby enhancing acousto-optic coupling rates. This study provides important insights that can be applied to acousto-optic device designs.

  2. Bulk and integrated acousto-optic spectrometers for molecular astronomy with heterodyne spectrometers

    NASA Technical Reports Server (NTRS)

    Chin, G.; Buhl, D.; Florez, J. M.

    1981-01-01

    A survey of acousto-optic spectrometers for molecular astronomy is presented, noting a technique of combining the acoustic bending of a collimated coherent light beam with a Bragg cell followed by an array of sensitive photodetectors. This acousto-optic spectrometer has a large bandwidth, a large number of channels, high resolution, and is energy efficient. Receiver development has concentrated on high-frequency heterodyne systems for the study of the chemical composition of the interstellar medium. RF spectrometers employing acousto-optic diffraction cells are described. Acousto-optic techniques have been suggested for applications to electronic warfare, electronic countermeasures and electronic support systems. Plans to use integrated optics for the further miniaturization of acousto-optic spectrometers are described. Bulk acousto-optic spectrometers with 300 MHz and 1 GHz bandwidths are being developed for use in the back-end of high-frequency heterodyne receivers for astronomical research.

  3. Ultrafast acousto-optic mode conversion in optically birefringent ferroelectrics

    PubMed Central

    Lejman, Mariusz; Vaudel, Gwenaelle; Infante, Ingrid C.; Chaban, Ievgeniia; Pezeril, Thomas; Edely, Mathieu; Nataf, Guillaume F.; Guennou, Mael; Kreisel, Jens; Gusev, Vitalyi E.; Dkhil, Brahim; Ruello, Pascal

    2016-01-01

    The ability to generate efficient giga–terahertz coherent acoustic phonons with femtosecond laser makes acousto-optics a promising candidate for ultrafast light processing, which faces electronic device limits intrinsic to complementary metal oxide semiconductor technology. Modern acousto-optic devices, including optical mode conversion process between ordinary and extraordinary light waves (and vice versa), remain limited to the megahertz range. Here, using coherent acoustic waves generated at tens of gigahertz frequency by a femtosecond laser pulse, we reveal the mode conversion process and show its efficiency in ferroelectric materials such as BiFeO3 and LiNbO3. Further to the experimental evidence, we provide a complete theoretical support to this all-optical ultrafast mechanism mediated by acousto-optic interaction. By allowing the manipulation of light polarization with gigahertz coherent acoustic phonons, our results provide a novel route for the development of next-generation photonic-based devices and highlight new capabilities in using ferroelectrics in modern photonics. PMID:27492493

  4. Acousto-Optic Spectrum Analyzer: Temporal Response and Detection of Pulsed Signals.

    DTIC Science & Technology

    1986-12-01

    ACOUSTO - OPTIC SPECTRUM ANALYZER: TEMPORAL RESPONSE AND I/i DETECTION OF PULSED SIGUALS(U) DEFENCE RESEARCH ESTABLISHMENT OTTANA (ONTARIO) J...8217:. -.....:.-...............--.. - ---:-..--.-..,. ,: i’,.. IJT~c FILE C P National Defe’ se + Deence nationale 0 0 ACOUSTO - OPTIC SPECTRUM ANALYZER: TEMPORAL RESPONSE AND DETECTION 0 OF PULSED...Ottawa |S, .±~ |-----------------------..,---.-- -- - - - rNatiorna! Defen~se Deterice r dornale ACOUSTO - OPTIC SPECTRUM ANALYZER: TEMPORAL RESPONSE

  5. Acousto-Optic Processing of 2-D Signals Using Temporal and Spatial Integration.

    DTIC Science & Technology

    1986-04-29

    AD-AI?3 411 ACOUSTO - OPTIC PROCESSING OF 2-D SIGNALS USING TEMPORAL 1/ AND SPATIAL INTEGR..(U) CRLIFORNIA INST OF TECH PASADENA DEPT OF ELECTRICAL...LECTE 3 FINAL REORT4 Submitted to: Al FORCE OFFICE OF SCIENTIFIC RESEARCH Grant Number AFOSR-82-0128 :A of % ACOUSTO - OPTIC PROCISSING OF 2-D SIGNALS...Psaltis, Applied Optics, Vol. 21, No. 3, 1 February 1982. (3) " Acousto - Optic /CCD Image Processor, Demetri Psaltis, Eung Gi Paek and Santosh Venkatesh

  6. The Study of the Phase Characteristics of Bragg Cells for Acousto-Optic Signal Processing

    DTIC Science & Technology

    1998-01-01

    THE FINAL REPORT ON THE SPECIAL CONTRACT SPC-97-4025 The Study of the Phase Characteristics of Bragg Cells for Acousto - Optic Signal Processing...for Acousto - Optic Signal Processing Unclassified 5a. CONTRACT NUMBER F6170897W0095 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Yurchenko...Characteristics of Bragg Cells for Acousto - Optic Signal Processing 5. FUNDING NUMBERS F6170897W0095 6. AUTHOR(S) Dr. Alexander Yurchenko 7. PERFORMING

  7. Acousto-Optic and Linear Electro-Optic Properties of Organic Polymeric Materials

    DTIC Science & Technology

    1989-04-27

    Naval Research Laboratory Washington, DC 20375-5000 NRL Memorandum Report 6454 od I3 Acousto - Optic and Linear Electro-Optic Properties of Organic...PROGRAM P1RC;EC7 ASK Arlington, VA 22217-5000 ELEMENT NO NO1 I1I TITLE (Include Security Classification) Acousto - Optic and Linear Electro-Optic...briefly discussing the important molecular properties for enhanced acousto ~ optic and electro-Ooptic ef fects and then relating these to "current

  8. 2-D Acousto-Optic Signal Processors for Simultaneous Spectrum Analysis and Direction Finding

    DTIC Science & Technology

    1990-11-01

    National Dfense Defence nationale 2-D ACOUSTO - OPTIC SIGNAL PROCESSORS FOR SIMULTANEOUS SPECTRUM ANALYSIS 00 AND DIRECTION FINDING (U) by NM Jim P.Y...Wr pdft .1w I0~1111191 3 05089 National DIfense Defence nationale 2-D ACOUSTO - OPTIC SIGNAL PROCESSORS FOR SIMULTANEOUS SPECTRUM ANALYSIS AND DIRECTION...Processing, J.T. Tippet et al., Eds., Chapter 38, pp. 715-748, MIT Press, Cambridge 1965. [6] A.E. Spezio," Acousto - optics for Electronic Warfare

  9. Guided-Wave TeO2 Acousto-Optic Devices

    DTIC Science & Technology

    1991-01-12

    In this research program, Guided-wave TeO2 Acousto - Optic Devices, the properties of surface acoustic waves on tellurium dioxide single crystal...surfaces has been studied for its potential applications as acousto - optic signal processing devices. Personal computer based numerical method has been...interaction with laser beams. Use of the acousto - optic probe, the surface acoustic wave velocity and field distribution have been obtained and compared

  10. Classification of Acousto-Optic Correlation Signatures of Spread Spectrum Signals Using Artificial Neural Networks

    DTIC Science & Technology

    1989-12-01

    Ohio ’aPw iorlipuab muo i 0I2, AFIT/GE/ENG/89D-10 CLASSIFICATION OF ACOUSTO - OPTIC CORRELATION SIGNATURES OF SPREAD SPECTRUM SIGNALS USING ARTIFICIAL...ENG/89D- 10 CLASSIFICATION OF ACOUSTO - OPTIC CORRELATION SIGNATURES OF SPREAD SPECTRUM SIGNALS USING ARTIFICIAL NEURAL NETWORKS THESIS John W. DeBerry...Captain, USAF AFIT/GE/ENG/89D- 10 Approved for public release; distribution unlimited. AFIT/GE/ENG/89D-10 CLASSIFICATION OF ACOUSTO - OPTIC CORRELATION

  11. Discussion on the Modelling and Processing of Signals fom an Acousto-Optic Spectrum Analyzer.

    DTIC Science & Technology

    1987-06-01

    AD-AIBS 639 DISCUSSION ON THE MODELLING AND PROCESSIN OF SIGNALS 1/1 FOR RN ACOUSTO - OPTIC SPECTRUM ANALYZER(U)G DFENCE RESERCH ESTABGLISHMENT OTTANA...8217’~ AV - I National DefenseI Defence nationale DISCUSSION ON THE MODELLING AND PROCESSING OF SIGNALS FROM AN ACOUSTO - OPTIC SPECTRUM ANALYZER by Guy...signals generated by an Acousto - Optic Spectrum Analyzer (AOSA). It also shows how this calculation can be related to pulse modu- lated signals. In its

  12. Three & Four Product Surface-Wave Acousto-Optic Time Integrating Correlators.

    DTIC Science & Technology

    four product correlated signals. A laser beam is split and shaped into first and second sheet beams. The first beam is directed to a first acousto - optic medium...where it is doubly diffracted by first and second signals. The second beam is directed to a second acousto - optic medium which is spatially...rotated 90 degs relative to the first acousto - optic medium where the second sheet beam is either singly diffracted by a third signal or doubly diffracted

  13. Design of acousto-optic chaos based secure free-space optical communication links

    NASA Astrophysics Data System (ADS)

    Ghosh, A. K.; Verma, P.; Cheng, S.; Huck, R. C.; Chatterjee, M. R.; Al-Saedi, M.

    2009-08-01

    We discuss the design of an acousto-optic cell based free space optical communication link where the data beam is made secure through chaos encryption. Using external signal modulation of the diffracted light from a hybrid acousto-optic cell chaos (or directly via incorporation in the sound-cell driver's bias voltage) encryption of data is possible. We have shown numerically that decryption of the encoded data is possible by using an identical acousto-optic system in the receiver.

  14. 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

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

    PubMed

    Binh, Le Nguyen

    2009-05-20

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

  16. Demonstration of optical interference filters utilizing tunable refractive index layers.

    PubMed

    Poxson, David J; Mont, Frank W; Schubert, Martin F; Kim, Jong Kyu; Cho, Jaehee; Schubert, E Fred

    2010-11-08

    Optical interference filters utilizing tunable refractive index layers are shown to have higher spectral fidelity as compared to conventional filters consisting of non-tunable refractive index layers. To demonstrate this increase in spectral fidelity, we design and compare a variety of optical interference filters employing both tunable and non-tunable refractive index layers. Additionally, a five-layer optical interference filter utilizing tunable refractive index layers is designed and fabricated for use with a Xenon lamp to replicate the Air Mass 0 solar irradiance spectrum and is shown to have excellent spectral fidelity.

  17. Electro-optical tunable birefringent filter

    SciTech Connect

    Levinton, Fred M

    2012-01-31

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

  18. Compact, robust, and spectrally pure diode-laser system with a filtered output and a tunable copy for absolute referencing

    NASA Astrophysics Data System (ADS)

    Kirilov, E.; Mark, M. J.; Segl, M.; Nägerl, H.-C.

    2015-05-01

    We report on a design of a compact laser system composed of an extended-cavity diode laser with high passive stability and a pre-filter Fabry-Perot cavity. The laser is frequency-stabilized relative to the cavity using a serrodyne technique with a correction bandwidth of ≥6 MHz and a dynamic range of ≥700 MHz. The free-running laser system has a power spectral density (PSD) ≤100 Hz2/Hz centered mainly in the acoustic frequency range. A highly tunable, 0.5-1.3 GHz copy of the spectrally pure output beam is provided, which can be used for further stabilization of the laser system to an ultra-stable reference. We demonstrate a simple one-channel lock to such a reference that brings down the PSD to the sub-Hz level. The tuning, frequency stabilization, and sideband imprinting are achieved by a minimum number of key elements comprising a fibered electro-optic modulator, acousto-optic modulator, and a nonlinear transmission line. The system is easy to operate, scalable, and highly applicable to atomic/molecular experiments demanding high spectral purity, long-term stability, and robustness.

  19. Magnetically tunable wideband microwave filter using ferrite-based metamaterials

    NASA Astrophysics Data System (ADS)

    Bi, Ke; Zhu, Wenting; Lei, Ming; Zhou, Ji

    2015-04-01

    Magnetically tunable wideband microwave filters have been designed and prepared by using ferrite-based metamaterial structures. The microwave properties of the filters have been investigated by experiments and simulations. The negative permeability appears around the ferromagnetic resonance frequency, which leads to a remarkable stopband for the bandstop filter. The bandpass filter is composed of two kinds of ferrite rods with different saturation magnetization. The bandwidth of the passband can be tuned by adjusting the saturation magnetization of the ferrite rods. Both the experimental and the simulated results show that those filters possess magnetically tunable property. This approach opens a way for designing tunable wideband microwave filters.

  20. Modelling Time-of-Arrival Ambiguities in a Combined Acousto-Optic and Crystal Video Receiver

    DTIC Science & Technology

    1995-11-01

    The probability of pulses overlapping in time being received by a combined acousto - optic /crystal video receiver is investigated. Theoretical analysis...number of pulses in that bandwidth. The number of frequency subbands with crystal detectors required to cover the acousto - optic receiver bandwidth is therefore a compromise between cost and complexity of implementation.

  1. Real-Time and Memory Correlation via Acousto-Optic Processing,

    DTIC Science & Technology

    1978-06-01

    acousto - optic technology as an answer to these requirements appears very attractive. Three fundamental signal-processing schemes using the acousto ... optic interaction have been investigated: (i) real-time correlation and convolution, (ii) Fourier and discrete Fourier transformation, and (iii

  2. A Comparative Study of Acousto-Optic Time-Integrating Correlators for Adaptive Jamming Cancellation

    DTIC Science & Technology

    1997-10-01

    This final report presents a comparative study of the space-integrating and time-integrating configurations of an acousto - optic correlator...systematically evaluate all existing acousto - optic correlator architectures and to determine which would be most suitable for adaptive jamming

  3. Acousto-Optic Technology for Topographic Feature Extraction and Image Analysis.

    DTIC Science & Technology

    1981-03-01

    This report contains all findings of the acousto - optic technology study for feature extraction conducted by Deft Laboratories Inc. for the U.S. Army...topographic feature extraction and image analysis using acousto - optic (A-O) technology. A conclusion of this study was that A-O devices are potentially

  4. Ferroic Crystals for Electro-Optic and Acousto-Optic Applications.

    DTIC Science & Technology

    properties for potential application in acousto - optic devices; and, (2) A systematic examination of the role of domain structures in modifying the...macroscopic properties of all types of ferroic crystals and the manner in which these property modifications could be exploited in acousto - optic , electro

  5. Acousto-Optic Beam Sampler, Part III: Diffraction Experiments at 10.6 micrometers.

    DTIC Science & Technology

    This report deals with the results of acousto - optic diffraction experiments in air at 10.6 micron. The laser used for the experiments was operated...fields. Detailed experiments were performed to investigate the dependence of the acousto - optic diffraction on incident laser power, acoustic drive voltage and angle of incidence.

  6. Kilohertz generation of high contrast polarization states for visible femtosecond pulses via phase-locked acousto-optic pulse shapers

    SciTech Connect

    Seiler, Hélène; Walsh, Brenna; Palato, Samuel; Kambhampati, Patanjali; Thai, Alexandre; Forget, Nicolas; Crozatier, Vincent

    2015-09-14

    We present a detailed analysis of a setup capable of arbitrary amplitude, phase, and polarization shaping of broadband visible femtosecond pulses at 1 kHz via a pair of actively phase stabilized acousto-optic programmable dispersive filters arranged in a Mach-Zehnder interferometer geometry. The setup features phase stability values around λ/225 at 580 nm as well as degrees of polarization of at least 0.9 for any polarization state. Both numbers are important metrics to evaluate a setup's potential for applications based on polarization-shaped femtosecond pulses, such as fully coherent multi-dimensional electronic spectroscopy.

  7. Imaging Spectrometer Using a Liquid Crystal Tunable Filter

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

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

    PubMed

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

    2013-03-01

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

  9. The Brazilian tunable filter imager for SOAR

    NASA Astrophysics Data System (ADS)

    Taylor, Keith; Mendes de Oliveira, Cláudia; Laporte, Rene; Guzman, Christian D.; Ramirez Fernandez, Javier; Scarano, Sergio, Jr.; Ramos, Giseli; Plana, Henri; Lourenco, Fernando E.; Gach, Jean-Luc; Fontes, Fernando L.; Ferrari, Fabricio; Cavalcanti, Luiz; Gutierrez Castañeda, Edna C.; de Calasans, Alvaro; Balard, Philippe; Amram, Philippe; Andrade, Denis

    2010-07-01

    A scientific and engineering team led by the Department of Astronomy of the IAG, at the University of São Paulo, is engaged in the development of a highly versatile, new technology, optical imaging interferometer to be used both in seeing-limited mode and at high spatial resolution using the SOAR Adaptive Optics Module (SAM: the GLAO facility for the SOAR telescope). Such an instrument opens up important new science capabilities for the SOAR astronomical community: from studies of nearby galaxies and the ISM to statistical cosmological investigations. The Brazilian Tunable Filter Imager (BTFI) concept takes advantage of two new technologies that have been successfully demonstrated in the laboratory environment but have yet to be deployed in any astronomical instrument. The iBTF (imaging Bragg Tunable Filter) concept utilizes a Volume Phase Holographic Grating in double-pass configuration (Blais-Ouellette et al. 20061) while the new Fabry-Perot concept involves the use of commercially available technology allowing a single etalon to act over a very large range of interference orders. Both technologies will be used in the same instrument. The combination allows for highly versatile capabilities. Spectral resolutions spanning the full range between 5 and 35,000 can be achieved in the same instrument through the use of iBTF at low resolution and scanning Fabry-Perots beyond R ~2,000 with some overlap in the mid-range. The instrument is being developed in collaboration with several other Brazilian Institutions (Poli/USP, INPE, LNA and Unipampa) and international collaborations with the Laboratoire d'Astrophysique de Marseille and the University of Montreal. The reader is directed to the URL http://www.astro.iag.usp.br/~btfi/index.php for a full representation of the project and its current status. The instrument should see first light, mounted on the SOAR telescope, as a visiting instrument, on semester 2010B.

  10. The Acousto-Optic Interaction in an Infinite Slab of Isotropic Material,

    DTIC Science & Technology

    1980-04-01

    AD-A097 202 HARRY DIAMOND LABS ADELPHI MD F/S 17/1 THE ACOUSTO - OPTIC INTERACTION IN AN INFINITE SLAB OF ISOTROPIC -- ETC(U) APR 80 S D SCHARF...611101.91A0011 .A1.A1 HOL Project: A10935 1S. KEY WONS (Cf ft "W reweee eld. It neceseeM md Io.t.Itl by block nm er) Acousto - optics Diffraction Mathieu... Acousto - Optic Interaction for Bragg Angles ...................... 13 FIGURES 1. Incident wave is split by acoustic wave into discrete diffracted orders

  11. Acousto-Optic Interaction in Surface Acoustic Waves and Its Application to Real Time Signal Processing.

    DTIC Science & Technology

    1977-12-30

    ACOUSTO - OPTIC INTERACTION IN SURFACE ACOUSTIC WAVES AND ITS APP--ETC(U) DEC 77 0 SCHUMER, P DAS NOOOIJ -75-C-0772 NCLASSIFIED MA-ONR-30 Nt.EE E’h...CHART NAT*NAL BUREAU OF STANDARDS 1-63- ACOUSTO - OPTIC INTERACTION IN SURFACE ACOUSTIC WAVES AND ITS APPLICATION TO REAL TIME SIGNAL PROCESSING By 00 D... Acousto - optics , Integrated optics, Optical Signal Processing. 20. AbSKTRACT (Continue an reverse side it neceary and idewnt& by block mum ber) The

  12. Acousto-optic imaging with a smart-pixels sensor

    NASA Astrophysics Data System (ADS)

    Barjean, K.; Contreras, K.; Laudereau, J.-B.; Tinet, E.; Ettori, D.; Ramaz, F.; Tualle, J.-M.

    2015-03-01

    Acousto-optic imaging (AOI) is an emerging technique in the field of biomedical optics which combines the optical contrast allowed by diffuse optical tomography with the resolution of ultrasound (US) imaging. In this work we report the implementation, for that purpose, of a CMOS smart-pixels sensor dedicated to the real-time analysis of speckle patterns. We implemented a highly sensitive lock-in detection in each pixel in order to extract the tagged photons after an appropriate in-pixel post-processing. With this system we can acquire images in scattering samples with a spatial resolution in the 2mm range, with an integration time compatible with the dynamic of living biological tissue.

  13. Acousto-optic/CCD real-time SAR data processor

    NASA Technical Reports Server (NTRS)

    Psaltis, D.

    1983-01-01

    The SAR processor which uses an acousto-optic device as the input electronic-to-optical transducer and a 2-D CCD image sensor, which is operated in the time-delay-and-integrate (TDI) mode is presented. The CCD serves as the optical detector, and it simultaneously operates as an array of optically addressed correlators. The lines of the focused SAR image form continuously (at the radar PRF) at the final row of the CCD. The principles of operation of this processor, its performance characteristics, the state-of-the-art of the devices used and experimental results are outlined. The methods by which this processor can be made flexible so that it can be dynamically adapted to changing SAR geometries is discussed.

  14. Acousto-Optic Measurements in CFRP Laminates Using Fiber Bragg Grating Sensors

    DTIC Science & Technology

    2011-09-01

    level. The main objective of this paper is to describe the results of an acousto - optic experiment using FBG sensors and present FR as a potential way of determining accumulated damage in a carbon composite structure.

  15. Acousto-Optic Processing of 2-D Signals Using Temporal and Spatial Integration.

    DTIC Science & Technology

    1983-05-31

    Documents includes data on: Architectures; Coherence Properties of Pulsed Laser Diodes; Acousto - optic device data; Dynamic Range Issues; Image correlation; Synthetic aperture radar; 2-D Fourier transform; and Moments.

  16. Acoustic field structure simulation in quasi-collinear acousto-optic cells with ultrasound beam reflection.

    PubMed

    Mantsevich, S N; Molchanov, V Ya; Yushkov, K B; Khorkin, V S; Kupreychik, M I

    2017-04-02

    Ultrasound wave reflection from one of the crystal faces is the convenient way to arouse the acoustic beam with a desired propagation direction in acousto-optic cells with collinear and quasi-collinear interaction geometries. The reflection process effects on the ultrasound field amplitude and phase structure. The method to simulate the reflected finite ultrasound beam structure in the case of acoustically anisotropic media is presented in this paper. The investigation is carried on the example of two quasi-collinear acousto-optic cells fabricated on the base of tellurium dioxide crystal. The cells have special geometry that allows to obtain extremely long acousto-optic interaction length and to achieve unprecedented spectral resolution. The influence of reflection process in the acousto-optic diffraction characteristics was also examined.

  17. Acousto-optic modulation of a photonic crystal nanocavity with Lamb waves in microwave K band

    NASA Astrophysics Data System (ADS)

    Tadesse, Semere A.; Li, Huan; Liu, Qiyu; Li, Mo

    2015-11-01

    Integrating nanoscale electromechanical transducers and nanophotonic devices potentially can enable acousto-optic devices to reach unprecedented high frequencies and modulation efficiency. Here, we demonstrate acousto-optic modulation of a photonic crystal nanocavity using Lamb waves with frequency up to 19 GHz, reaching the microwave K band. The devices are fabricated in suspended aluminum nitride membrane. Excitation of acoustic waves is achieved with interdigital transducers with period as small as 300 nm. Confining both acoustic wave and optical wave within the thickness of the membrane leads to improved acousto-optic modulation efficiency in these devices than that obtained in previous surface acoustic wave devices. Our system demonstrates a scalable optomechanical platform where strong acousto-optic coupling between cavity-confined photons and high frequency traveling phonons can be explored.

  18. Acousto-optic modulation of a photonic crystal nanocavity with Lamb waves in microwave K band

    SciTech Connect

    Tadesse, Semere A.; Li, Huan; Liu, Qiyu; Li, Mo

    2015-11-16

    Integrating nanoscale electromechanical transducers and nanophotonic devices potentially can enable acousto-optic devices to reach unprecedented high frequencies and modulation efficiency. Here, we demonstrate acousto-optic modulation of a photonic crystal nanocavity using Lamb waves with frequency up to 19 GHz, reaching the microwave K band. The devices are fabricated in suspended aluminum nitride membrane. Excitation of acoustic waves is achieved with interdigital transducers with period as small as 300 nm. Confining both acoustic wave and optical wave within the thickness of the membrane leads to improved acousto-optic modulation efficiency in these devices than that obtained in previous surface acoustic wave devices. Our system demonstrates a scalable optomechanical platform where strong acousto-optic coupling between cavity-confined photons and high frequency traveling phonons can be explored.

  19. Narrow-Band WGM Optical Filters With Tunable FSRs

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

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

  20. Submillimeter Wave Astronomy Satellite (SWAS) acousto-optical spectrometer

    NASA Astrophysics Data System (ADS)

    Klumb, Markus; Frerick, J.; Tolls, Volker; Schieder, Rudolf; Winnewisser, Gisbert F.

    1994-09-01

    The first fully space qualified acousto-optical spectrometer (AOS) is described. It is built for the Submillimeter Wave Astronomy Satellite (SWAS) to be launched in July 1995. It has a very large bandwidth from 1400 to 2800 MHz covered by 1365 channels. This corresponds to a nearly 1 MHz channel spacing. The design is optimized for very high stability, which is demonstrated by means of Allan variance stability test. The Allan plot minimum time was found well above 800 seconds. The AOS can operate within a temperature range from -5 to +30 degree(s)C (+5 to +25 degree(s)C nominal) and with temperature variations of up to 2 degree(s)C/h. The performance was verified also after environmental testing such as random vibration (10.2 G rms) and thermal cycling of -30 to +50 degree(s)C. The lightweight mechanical design resulted in a total weight of 7.2 kg including electronics. A detailed optical design study was performed in order to achieve diffraction limited channel resolution, high efficiency and low sensitivity to mechanical distortion. The RF input power needed for full scale is 11 mW. The power consumption is 5.4 Watts (including data pre-averaging and DC-DC converter losses). The development has shown that AOSs are well suited for spaceborne applications.

  1. Acousto-optics studied in polaritonic photonic crystals

    NASA Astrophysics Data System (ADS)

    Singh, Mahi R.; Racknor, C.

    2010-10-01

    We have studied the acousto-optic effect on the photon transmission and the spontaneous emission in polaritonic photonic crystal. We have considered that photonic crystals are fabricated from polaritonic materials such as GaP, MgO, LiNbO3 , and LiTaO3 . A two-level quantum dot is doped in a polaritonic crystal to study the decay rate of the spontaneous emission. The decay rate of quantum dots, band structure, and photon transmission coefficient have been calculated. It is found that band-gap width and the decay rate of quantum dots depends strongly on the high-frequency dielectric constant of the polaritonic crystals while the photonic band edges vary inversely by the ratio of longitudinal- to transverse-optical phonon energies. The spontaneous decay rate of the quantum dot can be controlled by the external strain field. This finding is significant because it is well known that the spontaneous emission is source of undesirable noise in different types of electronic and optical devices. Finally, we have also found the system can be switched from transmitting state to reflecting state by applying an external strain field. These are distinct and interesting results and can be used to fabricate new types of photonic couplers and fibers which in turn can be used to fabricate all photonic switches.

  2. Acousto-optical imaging using a powerful long pulse laser

    NASA Astrophysics Data System (ADS)

    Rousseau, Guy; Blouin, Alain; Monchalin, Jean-Pierre

    2008-06-01

    Acousto-optical imaging is an emerging biodiagnostic technique which provides an optical spectroscopic signature and a spatial localization of an optically absorbing target embedded in a strongly scattering medium. The transverse resolution of the technique is determined by the lateral extent of ultrasound beam focal zone while the axial resolution is obtained by using short ultrasound pulses. Although very promising for medical diagnostic, the practical application of this technique is presently limited by its poor sensitivity. Moreover, any method to enhance the signal-to-noise ratio must obviously satisfy the in vivo safety limits regarding the acceptable power level of both the ultrasonic pressure wave and the laser beam. In this paper, we propose to improve the sensitivity by using a pulsed single-frequency laser source to raise the optical peak power applied to the scattering medium and to collect more ultrasonically tagged photons. Such a laser source also allows illuminating the tissues mainly during the transit time of the ultrasonic wave to maintain the average optical power below the maximum permissible exposure. In our experiment, a single-frequency Nd:YAG laser emitting 500-μs pulses with a peak power superior to 100 W was used. Photons were tagged in few-cm thick optical phantoms with tone bursts generated by an ultrasonic transducer. Tagged photons were detected with a GaAs photorefractive interferometer characterized by a large optical etendue to process simultaneously a large number of speckle grains. When pumped by high intensity laser pulses, such an interferometer also provides the fast response time essential to obtain an apparatus insensitive to the speckle decorrelation due to mechanical vibrations or tissues movements. The use of a powerful long pulse laser appears promising to enhance the signal level in ultrasound modulated optical imaging. When combined with a photorefractive interferometer of large optical etendue, such a source could

  3. Applications of acousto-optics in holographic memories

    NASA Astrophysics Data System (ADS)

    Gurevich, Boris S.; Gurevich, Simon B.; Zhumaliev, Kubanychbek M.; Akkoziev, Imil A.; Alymkulov, Salmor A.

    1999-09-01

    Acousto-optic deflectors (AODs) are used for data by-page recording as holograms, and for data extraction from the hologram sampled by the AOD. The possibilities and characteristics of AODs define information capacity of the holographic memory devices as well as architecture and parameters of their separate components. Usually 2 AODs are used for 2-D hologram recording, and 3 AODs -- for volume multiplex recording. The calculations of amount of the recorded holograms which can be provided by different AODs have been carried out in the present work, and the limits of information capacity increasing at expense of optimal using of both AODs and recording media, have been appointed. The specific attention have been paid to the hologram 3-D recording with angular multiplexing where information capacity can be increased by 2 orders. The difficulties to be overcome in order to achieve the biggest information capacity, have been noted. Another subject of study is the problem of the sampled data arbitrary access rate increasing which can be provided by AODs application. It has been noted that minimum access time is limited, and this limitation is connected with the duration of the signal transmission through Bragg cell and with the time of signal transmission and processing in other components of holographic memory. It has been shown that information quality of holographic memory grows along with increasing of the number of used AODs. It has also been noted that if the memory parameters are close to their limits, the cross-talks grow, and the optimum must be found.

  4. CMOS-integrated geometrically tunable optical filters.

    PubMed

    Lerose, Damiana; Hei, Evie Kho Siaw; Ching, Bong Ching; Sterger, Martin; Yaw, Liau Chu; Schulze, Frank Michael; Schmidt, Frank; Schmidt, Andrei; Bach, Konrad

    2013-03-10

    We present a method for producing monolithically integrated complementary metal-oxide-semiconductor (CMOS) optical filters with different and customer-specific responses. The filters are constituted by a Fabry-Perot resonator formed by two Bragg mirrors separated by a patterned cavity. The filter response can be tuned by changing the geometric parameters of the patterning, and consequently the cavity effective refractive index. In this way, many different filters can be produced at once on a single chip, allowing multichanneling. The filter has been designed, produced, and characterized. The results for a chip with 24 filters are presented.

  5. A Statistical Analysis of the Output Signals of an Acousto-Optic Spectrum Analyzer for CW (Continuous-Wave) Signals

    DTIC Science & Technology

    1988-10-01

    A statistical analysis on the output signals of an acousto - optic spectrum analyzer (AOSA) is performed for the case when the input signal is a...processing, Electronic warfare, Radar countermeasures, Acousto - optic , Spectrum analyzer, Statistical analysis, Detection, Estimation, Canada, Modelling.

  6. Tunable reflecting terahertz filter based on chirped metamaterial structure.

    PubMed

    Yang, Jing; Gong, Cheng; Sun, Lu; Chen, Ping; Lin, Lie; Liu, Weiwei

    2016-12-12

    Tunable reflecting terahertz bandstop filter based on chirped metamaterial structure is demonstrated by numerical simulation. In the metamaterial, the metal bars are concatenated to silicon bars with different lengths. By varying the conductivity of the silicon bars, the reflectivity, central frequency and bandwidth of the metamaterial could be tuned. Light illumination could be introduced to change the conductivity of the silicon bars. Numerical simulations also show that the chirped metamaterial structure is insensitive to the incident angle and polarization-dependent. The proposed chirped metamaterial structure can be operated as a tunable bandstop filter whose modulation depth, bandwidth, shape factor and center frequency can be controlled by light pumping.

  7. Tunable reflecting terahertz filter based on chirped metamaterial structure

    PubMed Central

    Yang, Jing; Gong, Cheng; Sun, Lu; Chen, Ping; Lin, Lie; Liu, Weiwei

    2016-01-01

    Tunable reflecting terahertz bandstop filter based on chirped metamaterial structure is demonstrated by numerical simulation. In the metamaterial, the metal bars are concatenated to silicon bars with different lengths. By varying the conductivity of the silicon bars, the reflectivity, central frequency and bandwidth of the metamaterial could be tuned. Light illumination could be introduced to change the conductivity of the silicon bars. Numerical simulations also show that the chirped metamaterial structure is insensitive to the incident angle and polarization-dependent. The proposed chirped metamaterial structure can be operated as a tunable bandstop filter whose modulation depth, bandwidth, shape factor and center frequency can be controlled by light pumping. PMID:27941833

  8. Tunable reflecting terahertz filter based on chirped metamaterial structure

    NASA Astrophysics Data System (ADS)

    Yang, Jing; Gong, Cheng; Sun, Lu; Chen, Ping; Lin, Lie; Liu, Weiwei

    2016-12-01

    Tunable reflecting terahertz bandstop filter based on chirped metamaterial structure is demonstrated by numerical simulation. In the metamaterial, the metal bars are concatenated to silicon bars with different lengths. By varying the conductivity of the silicon bars, the reflectivity, central frequency and bandwidth of the metamaterial could be tuned. Light illumination could be introduced to change the conductivity of the silicon bars. Numerical simulations also show that the chirped metamaterial structure is insensitive to the incident angle and polarization-dependent. The proposed chirped metamaterial structure can be operated as a tunable bandstop filter whose modulation depth, bandwidth, shape factor and center frequency can be controlled by light pumping.

  9. An approach for mechanically tunable, dynamic terahertz bandstop filters

    NASA Astrophysics Data System (ADS)

    Li, Quan; Zhang, Xueqian; Cao, Wei; Lakhtakia, Akhlesh; O'Hara, John F.; Han, Jiaguang; Zhang, Weili

    2012-05-01

    Theoretical and experimental work was carried out on a terahertz metamaterial bandstop filter comprising an array of identical subwavelength resonators, each formed by fusing a pair of printable metallic U-shapes that have their openings pointing in opposite directions. Linear frequency tunability of the stopband electromagnetic response can be achieved by altering the overlap distance between the two fused shapes. Tuning does not significantly affect the strength or quality factor of the resonance. An approach to create mechanically tunable, dynamic terahertz filters is thereby suggested, with several functional advantages. Meanwhile, an effective equivalent circuit model based on self-inductance, mutual inductance, and capacitance has been proposed.

  10. Temperature Tunable Air-Gap Etalon Filter

    NASA Technical Reports Server (NTRS)

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

    1998-01-01

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

  11. Lyapunov exponent of chaos generated by acousto-optic modulators with feedback

    NASA Astrophysics Data System (ADS)

    Ghosh, Anjan K.; Verma, Pramode

    2011-01-01

    Generation of chaos from acousto-optic modulators with an electronic feedback has been studied for several years. Such chaotic signals have an important application in providing secure encryption in free-space optical communication systems. Lyapunov exponent is an important parameter for analysis of chaos generated by a nonlinear system. The Lyapunov exponent of an acousto-optic system is determined and calculated in this paper to understand the dependence of the chaotic response on the system parameters such as bias, feedback gain, input intensity and initial condition exciting the cell. Analysis of chaos using Lyapunov exponent is consistent with bifurcation analysis and is useful in encrypting data signals.

  12. Acousto-optical combined frequency splitters and shifters as components of a ring optical gyroscope

    SciTech Connect

    Kotov, V M

    1999-03-31

    An analysis is made of the task of symmetrisation of a Y-type directional coupler and of shifting the frequency of counterpropagating waves in a ring gyroscope by means of the relatively recently discovered new type of acousto-optical diffraction when the incident radiation is diffracted simultaneously into two orders. Anisotropic and isotropic acousto-optical diffraction in a uniaxial crystal is considered and expressions convenient for calculations are derived. Experiments carried out on isotropic diffraction in LiNbO{sub 3} confirm, on the whole, the theoretical predictions. (laser applications and other topics in quantum electronics)

  13. Wide-band acousto-optic deflectors with high efficiency for visible range fringe pattern projector.

    PubMed

    Dupont, S; Kastelik, J C; Causa, F

    2007-10-01

    A laser fringe projection system based on a pair of identical acousto-optic TeO(2) deflectors operated at the same frequency and using tangential phase matching anisotropic interaction is demonstrated, achieving large bandwidth and high efficiency. A 40 MHz bandwidth and an acousto-optic efficiency higher than 60% have been measured at wavelength of 514 nm. The specific pris-matic configuration of the in-house developed deflectors greatly facilitates optical alignment of the instrument. The spatial period of the interference fringes can be dynamically controlled over almost one decade by tuning the frequency of the acoustic carriers.

  14. Construction and characterization of ultraviolet acousto-optic based femtosecond pulse shapers

    SciTech Connect

    Mcgrane, Shawn D; Moore, David S; Greenfield, Margo T

    2008-01-01

    We present all the information necessary for construction and characterization of acousto optic pulse shapers, with a focus on ultraviolet wavelengths, Various radio-frequency drive configurations are presented to allow optimization via knowledgeable trade-off of design features. Detailed performance characteristics of a 267 nm acousto-optic modulator (AOM) based pulse shaper are presented, Practical considerations for AOM based pulse shaping of ultra-broad bandwidth (sub-10 fs) amplified femtosecond pulse shaping are described, with particular attention paid to the effects of the RF frequency bandwidth and optical frequency bandwidth on the spatial dispersion of the output laser pulses.

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

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

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

  16. Tunable, nondispersive optical filter using photonic Hilbert transformation.

    PubMed

    Bazargani, Hamed Pishvai; Fernández-Ruiz, María del Rosario; Azaña, José

    2014-09-01

    We propose and numerically demonstrate a new design concept for implementing nondispersive complementary (band-pass/band-reject) optical filters with a wide range of bandwidth tunability. The device consists of two photonic Hilbert transformers (PHTs) incorporated into a Michelson interferometer (MI). By controlling the central frequency of PHTs with respect to each other, both the central frequency and the spectral width of the rejection/pass bands of the filter are proved to be tunable. Bandwidth tuning from 260 MHz to 60 GHz is numerically demonstrated using two readily feasible fiber Bragg grating-based PHTs. The designed filter offers a high extinction ratio between the pass band and rejection band (>20  dB in the narrow-band filtering case) with a very sharp transition with a slope of 170  dB/GHz from rejection to pass band.

  17. Invited Article: Acousto-optic finite-difference frequency-domain algorithm for first-principles simulations of on-chip acousto-optic devices

    NASA Astrophysics Data System (ADS)

    Shi, Yu; Cerjan, Alexander; Fan, Shanhui

    2017-02-01

    We introduce a finite-difference frequency-domain algorithm for coupled acousto-optic simulations. First-principles acousto-optic simulation in time domain has been challenging due to the fact that the acoustic and optical frequencies differ by many orders of magnitude. We bypass this difficulty by formulating the interactions between the optical and acoustic waves rigorously as a system of coupled nonlinear equations in frequency domain. This approach is particularly suited for on-chip devices that are based on a variety of acousto-optic interactions such as the stimulated Brillouin scattering. We validate our algorithm by simulating a stimulated Brillouin scattering process in a suspended waveguide structure and find excellent agreement with coupled-mode theory. We further provide an example of a simulation for a compact on-chip resonator device that greatly enhances the effect of stimulated Brillouin scattering. Our algorithm should facilitate the design of nanophotonic on-chip devices for the harnessing of photon-phonon interactions.

  18. Instrumentation for time-resolved dynamic and static dichroic measurements of polymers with a near-IR acoustooptic tunable filter

    NASA Astrophysics Data System (ADS)

    Sweat, Joseph Allen

    1999-11-01

    The optical measurement of the orientational response of chemical functional groups of a polymer as it is subjected to conventional dynamic mechanical analysis can give insight into the rheological behavior of the polymer while under repetitive strain based on the chemical structure. Instrumentation used in the mid infrared has included the use of grating monochromators and interferometers. The use of a multiply modulated optical signal has decreased the level of noise to observe the small amplitude changes (typically >10-3 absorbance units) associated with the repetitive oscillatory strain. The use of digital signal processing to replace phase sensitive detection for demodulation of the optical signal has greatly reduced the spectral collection time. In addition, multiplexing gained with the use of step-scan interferometry in making time resolved measurements has aided in making the procedure more practical. However, instrumental complexity and expense are drawbacks. By incorporating the high throughput, polarized tuned beam, and rapid wavelength switching capability of an acousto-optic tunable filter (AOTF), a dynamic instrument with integrated centralized control by a single microprocessor has been built. it operates in the near infrared with a rapid dynamic data collection time and requires the use of only a single modulation in the form of the sample oscillatory strain. The near infrared permits thicker samples to reduce sample preparation tune or allows polymers to be tested without pretreatment. The use of Fourier based digital filtering improves the signal to noise ratio of the dynamic differential spectra. The instrument is cost effective and rugged in comparison to step-scan interferometers yet has a rapid data collection rate allowing use in a routine industrial setting. Information from these measurements can aid in determining the rheological properties necessary for the end use functionality of a polymer. Additionally, AOTF instrumentation can be used

  19. The Brazilian Tunable Filter Imager for the SOAR Telescope

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  20. Optical Oscillation Established Using Acousto-Optic Bragg Angle Defraction In Conjunction With Closed Cavity Feedback

    NASA Astrophysics Data System (ADS)

    Vezzoli, G. C.; Cadwallender, W.; Megargel, L. R.; Mentzer, M. A.; Craley, D. E.

    1987-03-01

    An optical oscillator has been designed, constructed, and operated by using a HeNe laser and acousto-optic modulator in conjunction with two opposed fiber optic feedback circuits. Depending on round-trip feedback time, a low frequency ( 1Hz) sinusoidal oscillator or a high frequency (100KHz) square wave (,..%,1 us rise time) is obtained.

  1. Highly efficient acousto-optic diffraction in Sn2P2S6 crystals.

    PubMed

    Martynyuk-Lototska, I Yu; Mys, O G; Grabar, A A; Stoika, I M; Vysochanskii, Yu M; Vlokh, R O

    2008-01-01

    We have studied the acousto-optic (AO) diffraction in Sn2P2S6 crystals and found that they manifest high values of an AO figure of merit. The above crystals may therefore be used as highly efficient materials in different AO applications.

  2. Tunable metamaterial bandstop filter based on ferromagnetic resonance

    NASA Astrophysics Data System (ADS)

    Wang, Qingmin; Zeng, Lingyu; Lei, Ming; Bi, Ke

    2015-07-01

    Tunable wideband microwave bandstop filters have been investigated by experiments and simulations. The negative permeability is realized around the ferromagnetic resonance frequency which can be influenced by the demagnetization factor of the ferrite rods. For the filter composed of two ferrite rods with different size, it exhibits a -3 db stop bandwidth as large as 500 MHz, peak absorption of -40 db and an out-of-stopband insertion loss of -1.5 db. This work provides a new way to fabricate the microwave bandstop filters.

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

    PubMed

    Alboon, Shadi A; Lindquist, Robert G

    2008-01-07

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

  4. A tunable microwave plasma photonic crystal filter

    SciTech Connect

    Wang, B.; Cappelli, M. A.

    2015-10-26

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

  5. Design of Hilbert transformers with tunable THz bandwidths using a reconfigurable integrated optical FIR filter

    NASA Astrophysics Data System (ADS)

    Ngo, Nam Quoc; Song, Yufeng; Lin, Bo

    2011-02-01

    We present the design and analysis of a wideband and tunable optical Hilbert transformer (OHT) using a tunable waveguide-based finite-impulse response (FIR) filter structure by using the digital filter design method and the Remez algorithm. The tunable Nth-order waveguide-based FIR filter, which simply consists of N delay lines, N tunable couplers, N tunable phase shifters and a combiner, can be tuned, by thermally adjusting the tunable couplers and tunable phase shifters, to tune the bandwidth of an OHT using silica-based planar lightwave circuit (PLC) technology. To demonstrate the effectiveness of the method, the simulation results have an excellent agreement with the theoretical predictions. The tunable OHT can function as a wideband and tunable 90° phase shifter and thus has many potential applications. The two unique features of wideband characteristic (up to ~ 2 THz) and tunable bandwidth (THz tuning range) of the proposed OHT cannot be obtained from the existing OHTs.

  6. Ultra-Narrow Band Tunable Filter

    DTIC Science & Technology

    2005-12-20

    the prototype system would require a design that would minimize the impact of cooler vibration on the filter. The cooler is nominally driven at 60 H-z...vibrations from an unbalanced cooler can be reduced in excess of 400x (26 dB) using the active vibration cancellation system (AVCS) that was developed...provide the RF feedback, and to build the system around a passively-balanced cooler , in order to complete delivery without further delays. We also had

  7. Gelled colloidal crystals as tunable optical filters for spectrophotometers

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  8. Imaging Spectrometer With Liquid-Crystal Tunable Filter

    NASA Technical Reports Server (NTRS)

    Chrien, Thomas G.

    1996-01-01

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

  9. Development of a Flyable Acousto-Optic Laser Beam Deflection System for a Head Up Display of the Future.

    DTIC Science & Technology

    Rayleigh criteria). The system was designed for stroke writing but was demonstrated with lissajous writing. The acousto - optic deflectors employed...The report describes a laser display which is to be used in a Head-Up Display of the future. The uniqueness of the display is that it uses acousto ... optic components for the modulation and deflection of the laser beam. As a result, there are no moving parts, which increases the reliability and life

  10. Piezo-optic, photoelastic, and acousto-optic properties of SrB4O7 crystals.

    PubMed

    Mytsyk, Bohdan; Demyanyshyn, Natalia; Martynyuk-Lototska, Irina; Vlokh, Rostyslav

    2011-07-20

    On the basis of studies of the piezo-optic effect, it has been shown that SrB(4)O(7) crystals can be used as efficient acousto-optic materials in the vacuum ultraviolet spectral range. The full matrices of piezo-optic and photoelastic coefficients have been experimentally obtained for these crystals. The acousto-optic figure of merit and the diffraction efficiency have been estimated for both the visible and deep ultraviolet spectral ranges.

  11. Tunable Filter Made From Three Coupled WGM Resonators

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

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

  12. Tunable high-q superconducting notch filter

    DOEpatents

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

    1979-11-29

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

  13. Acousto-optical pulsar processor usage for interstellar medium dispersion measurements

    NASA Astrophysics Data System (ADS)

    Esepkina, Nelli A.; Lavrov, Aleksandr P.; Molodyakov, Sergey A.

    2005-02-01

    The acousto-optical processor (AOP) of a new type for the investigation of pulsar radio emission is proposed that provides for the compensation of signal dispersion in a wide frequency bandwidth. The AOP is based on an acousto-optical spectrum analyzer with a CCD photodetector operating in a special pipeline operational mode (shift-and-add mode), which allows spectral components of the input signal to be added with a controlled time delay immediately in the CCD photodetector. The proposed AOP was successfully used on an RT-64 radio telescope (Kalyazin Radio Astronomy Observatory FIAN) for the observation of pulsars at 1.4 GHz band with bandwidth 45 MHz. The method of direct interstellar medium dispersion measurement on two-frequency band observations with application AOP is described. The measurements of DM for pulsar PSR 1937 + 21 are submitted.

  14. Note: Laser frequency shifting by using two novel triple-pass acousto-optic modulator configurations

    SciTech Connect

    Carlos-Lopez, E. de; Lopez, J. M.; Lopez, S.; Espinosa, M. G.; Lizama, L. A.

    2012-11-15

    We report the design of two novel triple-pass acousto-optic modulator systems. These designs are extensions of the well known acousto-optic modulator (AOM) double-pass configuration, which eliminates the angle dependence of the diffracted beam with respect to the modulation frequency. In a triple-pass system, however, the frequency dependence of the angle does not disappear but the frequency shift is larger, spanning 3 times the AOM central frequency. In some applications, such as optically pumped Cesium-beam frequency standards, the frequencies of the two laser beams remain fixed and a triple-pass optical system can be used to reduce to one the number of lasers used in such atomic clocks. The two triple-pass configurations use either a retro-reflecting mirror, or a right angle prism to pass for third time the laser beam through the AOM, obtaining diffraction efficiencies of about 27% and 44%, respectively.

  15. Photon frequency-mode matching using acousto-optic frequency beam splitters

    SciTech Connect

    Jones, Nick S.; Stace, T. M.

    2006-03-15

    It is a difficult engineering task to create distinct solid state single photon sources which nonetheless emit photons at the same frequency. It is also hard to create entangled photon pairs from quantum dots. In the spirit of quantum engineering we propose a simple optical circuit which can, in the right circumstances, make frequency distinguishable photons frequency indistinguishable. Our circuit can supply a downstream solution to both problems, opening up a large window of allowed frequency mismatches between physical mechanisms. The only components used are spectrum analysers or prisms and an acousto-optic modulator. We also note that an acousto-optic modulator can be used to obtain Hong-Ou-Mandel two photon interference effects from the frequency distinguishable photons generated by distinct sources.

  16. Acousto-optical modulation of light at a doubled sound frequency

    SciTech Connect

    Kotov, V M; Averin, S V; Shkerdin, G N

    2016-02-28

    A method of acousto-optical (AO) Bragg diffraction is proposed that provides the amplitude modulation of optical radiation at a doubled acoustic frequency. The method is based on the double transmission of the light through the AO modulator made of a gyrotropic crystal and is experimentally tested by the example of the modulation of light with a wavelength of 0.63 μm, controlled by the paratellurite AO cell. (acoustooptics)

  17. Laser identification system based on acousto-optical barcode scanner principles

    NASA Astrophysics Data System (ADS)

    Khansuvarov, Ruslan A.; Korol, Georgy I.; Preslenev, Leonid N.; Bestugin, Aleksandr R.; Paraskun, Arthur S.

    2016-09-01

    The main purpose of the bar code in the modern world is the unique identification of the product, service, or any of their features, so personal and stationary barcode scanners so widely used. One of the important parameters of bar code scanners is their reliability, accuracy of the barcode recognition, response time and performance. Nowadays, the most popular personal barcode scanners contain a mechanical part, which extremely impairs the reliability indices. Group of SUAI engineers has proposed bar code scanner based on laser beam acoustic deflection effect in crystals [RU patent No 156009 issued 4/16/2015] Through the use of an acousto-optic deflector element in barcode scanner described by a group of engineers SUAI, it can be implemented in the manual form factor, and the stationary form factor of a barcode scanner. Being a wave electronic device, an acousto-optic element in the composition of the acousto-optic barcode scanner allows you to clearly establish a mathematical link between the encoded function of the bar code with the accepted input photodetector intensities function that allows you to speak about the great probability of a bar code clear definition. This paper provides a description of the issued patent, the description of the principles of operation based on the mathematical analysis, a description of the layout of the implemented scanner.

  18. Two-dimensional refractive index modulation by phased array transducers in acousto-optic deflectors.

    PubMed

    Wang, Tiansi; Zhang, Chong; Aleksov, Aleksandar; Salama, Islam; Kar, Aravinda

    2017-01-20

    Acousto-optic deflectors are photonic devices that are used for scanning high-power laser beams in advanced microprocessing applications such as marking and direct writing. The operation of conventional deflectors mostly relies on one-dimensional sinusoidal variation of the refractive index in an acousto-optic medium. Sometimes static phased array transducers, such as step configuration or planar configuration transducer architecture, are used to tilt the index modulation planes for achieving higher performance and higher resolution than a single transducer AO device. However, the index can be modulated in two dimensions, and the modulation plane can be tilted arbitrarily by creating dynamic phase gratings in the medium using phased array transducers. This type of dynamic two-dimensional acousto-optic deflector can provide better performance using, for example, a large deflection angle and high diffraction efficiency. This paper utilizes an ultrasonic beam steering approach to study the two-dimensional strain-induced index modulation due to the photoelastic effect. The modulation is numerically simulated, and the effects of various parameters, such as the operating radiofrequency of the transducers, the ultrasonic beam steering angle, and different combinations of pressure on each element of the transducer array, are demonstrated.

  19. 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.

  20. An advanced regime of the anomalous acousto-optical interaction with tangential phase matching in crystalline materials

    NASA Astrophysics Data System (ADS)

    Shcherbakov, Alexandre S.; Arellanes, Adan O.

    2016-09-01

    Regime of effective non-collinear acousto-optical interaction with tangential phase matching had been identified and previously observed only in two limiting cases: in tellurium dioxide (TeO2) at low acoustic frequencies ( 60 MHz) and in rutile (TiO2) at ultra-high frequencies ( 5 GHz). Both these limits are motivated by optical properties of the chosen materials. Low frequencies in TeO2 admit designing a wide-aperture acousto-optical cell, but limit the frequency bandwidth. While an acousto-optical cell made of TiO2 has very small aperture and exhibits low spectral resolution due to the effect of linear acoustic attenuation. Instead of those limits, we propose an advanced regime of the anomalous acousto-optical interaction with tangential phase matching, which allows us varying the frequency range and optimizing all the performances (for instance, the spectral resolution) of a wide-aperture acousto-optical cell made of the chosen crystal, as the case requires. Recently, we had suggested and successfully tested experimentally the revealed additional degree of freedom, i.e. the action of the tilt angle within the refractive indices ellipsoids to manipulate by the performances of crystalline acousto-optical cells. Now, we consider an opportunity of refining this additional degree of freedom within those ellipsoids of crystalline acousto-optical cell through some declination of the acoustic beam. For our investigations, the lithium niobate (LiNbO3) and rutile (TiO2) crystals of about 5 cm length, operating with the slow-shear acoustic mode along the acoustic axes had been selected. The needed theoretical analysis, numerical estimations, and 3D-vector diagrams have been developed to reveal potential benefits of the proposed technique.

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

    PubMed

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

    2015-01-01

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

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

    SciTech Connect

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

    2014-10-15

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

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

    PubMed

    Mudge, Jason; Tarbell, Theodore

    2014-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

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

  5. Acousto-optic interaction in alpha-BaB(2)O(4)and Li(2)B(4)O(7) crystals.

    PubMed

    Martynyuk-Lototska, Irina; Mys, Oksana; Dudok, Taras; Adamiv, Volodymyr; Smirnov, Yevgen; Vlokh, Rostyslav

    2008-07-01

    Experimental studies and analysis of acousto-optic diffraction in alpha-BaB(2)O(4) and Li(2)B(4)O(7) crystals are given. Ultrasonic wave velocity, elastic compliance and stiffness coefficients, and piezo-optic and photoelastic coefficients of alpha-BaB(2)O(4) and Li(2)B(4)O(7) crystals are determined. The acousto-optic figure of merit has been estimated for different possible geometries of acousto-optic interaction. It is shown that the acousto-optic figures of merit for alpha-BaB(2)O(4) crystals reach the value M(2)=(270 +/- 70) x 10(-15) s(3)/kg for the case of interaction with the slowest ultrasonic wave. The directions of propagation and polarization of those acoustic waves are obtained on the basis of construction of acoustic slowness surfaces. The acousto-optic diffraction is experimentally studied for alpha-BaB(2)O(4) and Li(2)B(4)O(7) crystals.

  6. Arrangement of an advanced acousto-optical processor for modeling the triple correlations of low-power optical pulse trains

    NASA Astrophysics Data System (ADS)

    Shcherbakov, Alexandre S.; Hanessian de la Garza, Ana V.; Chavushyan, Vahram; Campos Acosta, Joaquin

    2012-02-01

    Both a high level of developing the spatially spot-like and one-dimensional input devices and the flexibility of a design inherent in two-dimensional optical systems with similar modulating components make it possible to realize various high-bit-rate opto-electronic processors. This is why a one-dimension acousto-optic technique has been involved in data processing and its modeling based on the algorithm of triple product correlations. Practically, triple product correlations originate within an optical scheme including the modulated light source, representing the first input port, and two wideaperture acousto-optical cells forming two other input ports. Due to specifically constructed lens system, initially modulated light beam is crossing sequentially the apertures of acousto-optical cells oriented at right angle to each other. Finally, a CCD-matrix integrates the received optical signal with respect to time and registers the resulting triple product correlations. In a view of arranging similar acousto-optical processor for modeling triple product correlations, we characterize a novel version of the acousto-optical cells exploiting now tellurium-dioxide crystals. Together with this, potential performances of the progressed design for similar processor are estimated as well.

  7. Bio-Inspired Dynamically Tunable Polymer-Based Filters for Multi-Spectral Infrared Imaging

    DTIC Science & Technology

    2010-05-01

    learned from UCSB’s analyses of the molecular mechanisms driving dynamically tunable reflectance in cephalopod skin to the development of a high-gain...Spectral, IR, polymer, tunable, cephalopod Daniel E. Morse University of California - Santa Barbara Office of Research The Regents of the University of...tunable reflectance in cephalopod skin to the development of a high-gain, dynamically tunable, polymer-based IR filter. Based on a revolutionary but simple

  8. Tunable color filters based on metal-insulator-metal resonators.

    PubMed

    Diest, Kenneth; Dionne, Jennifer A; Spain, Merrielle; Atwater, Harry A

    2009-07-01

    We report a method for filtering white light into individual colors using metal-insulator-metal resonators. The resonators are designed to support photonic modes at visible frequencies, and dispersion relations are developed for realistic experimental configurations. Experimental results indicate that passive Ag/Si(3)N(4)/Au resonators exhibit color filtering across the entire visible spectrum. Full field electromagnetic simulations were performed on active resonators for which the resonator length was varied from 1-3 microm and the output slit depth was systematically varied throughout the thickness of the dielectric layer. These resonators are shown to filter colors based on interference between the optical modes within the dielectric layer. By careful design of the output coupling, the resonator can selectively couple to intensity maxima of different photonic modes and, as a result, preferentially select any of the primary colors. We also illustrate how refractive index modulation in metal-insulator-metal resonators can yield actively tunable color filters. Simulations using lithium niobate as the dielectric layer and the top and bottom Ag layers as electrodes, indicate that the output color can be tuned over the visible spectrum with an applied field.

  9. Micromachined Tunable Fabry-Perot Filters for Infrared Astronomy

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

  10. Noise tolerance in wavelength-selective switching of optical differential quadrature-phase-shift-keying pulse train by collinear acousto-optic devices.

    PubMed

    Goto, Nobuo; Miyazaki, Yasumitsu

    2014-06-01

    Optical switching of high-bit-rate quadrature-phase-shift-keying (QPSK) pulse trains using collinear acousto-optic (AO) devices is theoretically discussed. Since the collinear AO devices have wavelength selectivity, the switched optical pulse trains suffer from distortion when the bandwidth of the pulse train is comparable to the pass bandwidth of the AO device. As the AO device, a sidelobe-suppressed device with a tapered surface-acoustic-wave (SAW) waveguide and a Butterworth-type filter device with a lossy SAW directional coupler are considered. Phase distortion of optical pulse trains at 40 to 100  Gsymbols/s in QPSK format is numerically analyzed. Bit-error-rate performance with additive Gaussian noise is also evaluated by the Monte Carlo method.

  11. Switchable and Tunable Ferroelectric Bulk Acoustic Wave Resonators and Filters

    NASA Astrophysics Data System (ADS)

    Saddik, George Nabih

    Ferroelectric materials such as barium titanate (BaTiO 3 or BTO), strontium titanate (SrTiO3 or STO), and their solid solution barium strontium titanate (BaxSr1-xTiO 3 or BST) have been under investigation for over 50 years. BTO, STO, and BST are high-k dielectric materials, with a field dependent permittivity and a perovskite crystal structure. At room temperature BTO is a ferroelectric with a ferroelectric to paraelectric transition temperature of about 116°C (Curie temperature), while STO has no ferroelectric phase. The formation of a solid solution between BTO and STO allows for the engineering of the Curie temperature; the Curie temperature decreses as the mole ratio of barium decreases. Extensive research went into understanding the properties of BST and developing RF circuits such as tunable capacitors, tunable matching networks, tunable filters, phase shifters and harmonic generators. BST tunable capacitors have always had anomalous resonances in the one port scattering parameter measurements, although they are very small they degrade the quality factor of the device, and research went into reducing these resonances as much as possible. The goal of this thesis is to investigate these anomalous resonances and exploit them into RF devices and circuits. Careful investigation showed that these resonances were field induced piezoelectric resonance. Piezoelectric materials such as AlN, ZnO, and PZT are used in many applications, such as resonators, and filters. Thin film bulk acoustic wave resonators (FBAR) have been in use by research and industry since the early 1980s, and in high volume production for cell phone duplexers since early 2000s. FBAR filters and duplexers have several advantages over surface acoustic wave (SAW) and ceramic devices such as high quality factors necessary for sharp filter skirts, small size, high performance, and ease of integration. There are two approaches to designing bulk acoustic wave resonators. The first is an FBAR where a

  12. Electro-Optic Effect in the PESO Acousto-Optic Modulator

    DTIC Science & Technology

    1994-11-09

    AD-A286 355 NAIC-ID(RS)T-0395-94 NATIONAL AIR INTELLIGENCE CENTER ELECTRO - OPTIC EFFECT IN THE PESO ACOUSTO-OPTIC MODULATOR by Tai Renzhong, Lu Futun...owing to coupling.betw;ee.elecuc grazing" and "acou- tic grating". Linear electro - optic effect in PESO modulator is helpful to the diffraction and...crystaO A-l/Am,ARjAb, anl / ar:.. thtta=30 and theta=900 . Along these two orientations. th;- electro - optic effect is restricted tcŽ the rn :-t m:,n e

  13. Acoustic wave velocities in two-dimensional composite structures based on acousto-optical crystals

    NASA Astrophysics Data System (ADS)

    Mal'neva, P. V.; Trushin, A. S.

    2015-04-01

    Sound velocities in two-dimensional composite structures based on isotropic and anisotropic acousto-optical crystals have been determined by numerical simulations. The isotropic materials are represented by fused quartz (SiO2) and flint glass, while anisotropic materials include tetragonal crystals of paratellurite (TeO2) and rutile (TiO2) and a trigonal crystal of tellurium (Te). It is established that the acoustic anisotropy of periodic composite structures strongly depends on both the chemical composition and geometric parameters of components.

  14. Acousto-optic diffraction of multicolour Ar-laser radiation in crystalline quartz

    SciTech Connect

    Kotov, V M; Averin, S V; Voronko, A I; Kuznetsov, P I; Tikhomirov, S A; Shkerdin, G N; Bulyuk, A N

    2015-10-31

    We have studied acousto-optic Bragg diffraction of multicolour radiation, generated by an Ar laser in the blue-green region of the spectrum, on an acoustic wave propagating in crystalline quartz. It is shown that crystalline quartz significantly exceeds commonly used paratellurite in terms of phase matching of optical beams with a single acoustic wave. We have performed experiments on pulse modulation of Ar-laser radiation. It is shown that distortions introduced into optical pulses are substantially less when use is made of a quartz crystal rather than paratellurite. (acoustooptics)

  15. Acousto-optic resonant coupling of three spatial modes in an optical fiber.

    PubMed

    Park, Hee Su; Song, Kwang Yong

    2014-01-27

    A fiber-optic analogue to an externally driven three-level quantum state is demonstrated by acousto-optic coupling of the spatial modes in a few-mode fiber. Under the condition analogous to electromagnetically induced transparency, a narrow-bandwidth transmission within an absorption band for the fundamental mode is demonstrated. The presented structure is an efficient converter between the fundamental mode and the higher-order modes that cannot be easily addressed by previous techniques, therefore can play a significant role in the next-generation space-division multiplexing communications as an arbitrarily mode-selectable router.

  16. Actively mode-locked fiber laser using acousto-optic modulator

    NASA Astrophysics Data System (ADS)

    Nikodem, Michal P.; Sergeant, Hendrik; Kaczmarek, Pawel; Abramski, Krzysztof M.

    2008-12-01

    In recent years we have observed growing interest in mode-locked fiber lasers. Development of erbium doped fiber (EDF) amplifiers and WDM technique made 3rd telecommunication window extremely interesting region for ultrafast optics. The main advantages of fiber lasers i.e. narrow linewidth and wide gain bandwidth make them very attractive sources in various applications. In this paper we present an actively mode-locked erbium doped fiber ring laser. Modelocking is obtained using an acousto-optic modulator (AOM) coupled into the laser cavity. The impact of different parameters (e.g. light polarization, modulation frequency) is investigated. We study mechanisms of controlling the wavelength of the laser.

  17. Acousto-optic parallel read/write head for optical disk data storage.

    PubMed

    McLeod, Robert R; Walter, Sarah K

    2006-09-20

    Parallel read and write of optical disks has traditionally used a static grating for read or a linear array of independent lasers for read and write. Depending on the implementation, these systems suffer from coherent cross talk, excessive space between spots, and an inability to independently track. We show that a dynamic acousto-optic grating can generate multiple parallel read/write spots on the disk, each of which can be independently modulated and tracked and all of which are incoherent in less that a bit period. The resulting disk pickup can potentially reach gigabit per second transfer rates with only a modest increase in the drive complexity.

  18. Acousto-optic parallel read/write head for optical disk data storage

    NASA Astrophysics Data System (ADS)

    McLeod, Robert R.; Walter, Sarah K.

    2006-09-01

    Parallel read and write of optical disks has traditionally used a static grating for read or a linear array of independent lasers for read and write. Depending on the implementation, these systems suffer from coherent cross talk, excessive space between spots, and an inability to independently track. We show that a dynamic acousto-optic grating can generate multiple parallel read/write spots on the disk, each of which can be independently modulated and tracked and all of which are incoherent in less that a bit period. The resulting disk pickup can potentially reach gigabit per second transfer rates with only a modest increase in the drive complexity.

  19. Acousto-optical interaction in fishbone-like one-dimensional phoxonic crystal nanobeam

    NASA Astrophysics Data System (ADS)

    Hsiao, Fu-Li; Hsieh, Hao-Yu; Hsieh, Cheng-Yi; Chiu, Chien-Chang

    2014-09-01

    We demonstrate the simultaneous existence of slow photonic and phononic modes in a fishbone-like one-dimensional phoxonic crystal nanobeam. The phoxonic crystal nanobeam, which is formed by a suspended fishbone-like silicon waveguide, is not only an optical one-dimensional grating waveguide but also a waveguide with acoustic local resonance. Because of the slow group velocities, the acousto-optical interactions are significantly enhanced. The operating optical wavelength and acoustic frequency can be manipulated individually by varying certain geometric parameters of the nanobeam.

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  1. Anisotropy of an acousto-optic figure of merit for NaBi(MoO4)2 crystals.

    PubMed

    Mys, Oksana; Krupych, Oleh; Vlokh, Rostyslav

    2016-10-01

    We develop a technique for analyzing the anisotropy of an acousto-optic figure of merit for crystals belonging to tetragonal symmetry groups 4/m, 4, and 4¯. The technique is based on phenomenological relations that describe anisotropies of the effective elasto-optic coefficients and the acoustic wave velocities. Our approach is verified on the example of NaBi(MoO4)2 crystals for all possible types and geometries of acousto-optic interactions. We list and characterize the acousto-optic interaction geometries at which the maximal acousto-optic figures of merit are reached for both isotropic and anisotropic interaction types. Finally, we show that the acousto-optic efficiency of NaBi(MoO4)2 originates mainly from large elasto-optic coefficients.

  2. Incoherent acousto-optic image correlator with the kinoform

    NASA Astrophysics Data System (ADS)

    Starikov, Sergey N.; Rodin, Vladislav G.; Solyakin, Ivan V.; Shapkarina, Ekaterina A.; Chervonkin, Alexander P.

    2004-04-01

    Fourier holograms are commonly used for reference images storing in diffraction correlators with spatially coherent or spatially incoherent illumination. Kinoforms can be a real alternative to Fourier holograms in the correlators. The kinoform represents a computer-synthesized optical element which performs only a phase modulation of a light wave. The kinoform restores true intensity of the recorded image and random distribution of phase. Therefore, it can be utilized for storing reference images, first of all, in correlators with spatially incoherent illumination. The absence of carrier frequency reduces demanded number of pixels of the spatial light modulator being used. Since the kinoform provides reconstruction of reference image in zero diffraction order, requirement on monochromaticity of illumination are decreased as well. The diffraction correlator with the kinoform used as spatial frequency filter is considered. The 2-D acoustooptic deflector was employed to form input images in real time by monochromatic spatially incoherent light. The reference images were recorded on the commercially available kinoforms. The input and reference images were of 256×256 pixels and 200×200 pixels respectively. Since input images were consisted of approximately 400 pixels with non-zero brightness, the image update frequency was gained at 200 Hz. The experimental setup and experimental results on images recognition are presented.

  3. Spin-to-orbit conversion at acousto-optic diffraction of light: conservation of optical angular momentum.

    PubMed

    Skab, Ihor; Vlokh, Rostyslav

    2012-04-01

    Acousto-optic diffraction of light in optically active cubic crystals is analyzed from the viewpoint of conservation of optical angular momentum. It is shown that the availability of angular momentum in the diffracted optical beam can be necessarily inferred from the requirements of angular momentum conservation law. As follows from our analysis, a circularly polarized diffracted wave should bear an orbital angular momentum. The efficiency of the spin-to-orbit momentum conversion is governed by the efficiency of acousto-optic diffraction.

  4. Acousto-optically tuned isotopic CO{sub 2} lasers for long-range differential absorption LIDAR

    SciTech Connect

    Thompson, D.C.; Busch, G.E.; Hewitt, C.J.; Remelius, D.K.; Shimada, Tsutomu; Strauss, C.E.M.; Wilson, C.W.

    1998-12-01

    The authors are developing 2--100 kHz repetition rate CO{sub 2} lasers with milliJoule pulse energies, rapid acousto-optic tuning and isotopic gas mixes, for Differential Absorption LIDAR (DIAL) applications. The authors explain the tuning method, which uses a pair of acousto-optic modulators and is capable of random access to CO{sub 2} laser lines at rates of 100 kHz or more. The laser system is also described, and they report on performance with both normal and isotopic gas mixes.

  5. Addressable, large-field second harmonic generation microscopy based on 2D acousto-optical deflector and spatial light modulator.

    PubMed

    Shao, Yonghong; Liu, Honghai; Qin, Wan; Qu, Junle; Peng, Xiang; Niu, Hanben; Gao, Bruce Z

    2012-09-01

    We present an addressable, large-field second harmonic generation microscope by combining a 2D acousto-optical deflector with a spatial light modulator. The SLM shapes an incoming mode-locked, near-infrared Ti:Sapphire laser beam into a multifocus array, which can be rapidly scanned by changing the incident angle of the laser beam using a 2D acousto-optical deflector. Compared to the single-beam-scan technique, the multifocus array scan can increase the scanning rate and the field-of-view size with the multi-region imaging ability.

  6. Addressable, large-field second harmonic generation microscopy based on 2D acousto-optical deflector and spatial light modulator

    PubMed Central

    Shao, Yonghong; Liu, Honghai; Qin, Wan; Qu, Junle; Peng, Xiang; Niu, Hanben

    2013-01-01

    We present an addressable, large-field second harmonic generation microscope by combining a 2D acousto-optical deflector with a spatial light modulator. The SLM shapes an incoming mode-locked, near-infrared Ti:Sapphire laser beam into a multifocus array, which can be rapidly scanned by changing the incident angle of the laser beam using a 2D acousto-optical deflector. Compared to the single-beam-scan technique, the multifocus array scan can increase the scanning rate and the field-of-view size with the multi-region imaging ability. PMID:24307756

  7. JWST tunable filter imager: etalon prototype test results

    NASA Astrophysics Data System (ADS)

    Touahri, D.; Cameron, P.; Evans, C.; Greenberg, E.; Rowlands, N.; Scott, A.; Doyon, R.; Beaulieu, M.; Djazovski, O.

    2008-07-01

    We present the prototyping results and laboratory characterization of a narrow band Fabry-Perot etalon flight model which is one of the wavelength selecting elements of the Tunable Filter Imager. The latter is a part of the Fine Guidance Sensor which represents the Canadian contribution to NASA's James Webb Space Telescope. The unique design of this etalon provides the JWST observatory with the ability to image at 30 Kelvin, a 2.2'x2.2' portion of its field of view in a narrow spectral bandwidth of R~100 at any wavelength ranging between 1.6 and 4.9 μm (with a gap in coverage between 2.5 and 3.2 μm). Extensive testing has resulted in better understanding of the thermal properties of the piezoelectric transducers used as an actuation system for the etalon gap tuning. Good throughput, spectral resolution and contrast have been demonstrated for the full wavelength range.

  8. Wide-band acousto-optic deflectors for large field of view two-photon microscope.

    PubMed

    Jiang, Runhua; Zhou, Zhenqiao; Lv, Xiaohua; Zeng, Shaoqun

    2012-04-01

    Acousto-optic deflector (AOD) is an attractive scanner for two-photon microscopy because it can provide fast and versatile laser scanning and does not involve any mechanical movements. However, due to the small scan range of available AOD, the field of view (FOV) of the AOD-based microscope is typically smaller than that of the conventional galvanometer-based microscope. Here, we developed a novel wide-band AOD to enlarge the scan angle. Considering the maximum acceptable acoustic attenuation in the acousto-optic crystal, relatively lower operating frequencies and moderate aperture were adopted. The custom AOD was able to provide 60 MHz 3-dB bandwidth and 80% peak diffraction efficiency at 840 nm wavelength. Based on a pair of such AOD, a large FOV two-photon microscope was built with a FOV up to 418.5 μm (40× objective). The spatiotemporal dispersion was compensated simultaneously with a single custom-made prism. By means of dynamic power modulation, the variation of laser intensity within the FOV was reduced below 5%. The lateral and axial resolution of the system were 0.58-2.12 μm and 2.17-3.07 μm, respectively. Pollen grain images acquired by this system were presented to demonstrate the imaging capability at different positions across the entire FOV.

  9. Acousto-optic Imaging System for In-situ Measurement of the High Temperature Distribution in Micron-size Specimens

    NASA Astrophysics Data System (ADS)

    Machikhin, Alexander S.; Zinin, Pavel V.; Shurygin, Alexander V.

    We developed a unique acousto-optic imaging system for in-situ measurement of high temperature distribution on micron-size specimens. The system was designed to measure temperature distribution inside minerals and functional material phases subjected to high pressure and high temperatures in a diamond anvil cell (DAC) heated by a high powered laser.

  10. All-optically reconfigurable and tunable fiber surface grating for in-fiber devices: a wideband tunable filter.

    PubMed

    Yu, Jianhui; Han, Yuqi; Huang, Hankai; Li, Haozi; Hsiao, Vincent K S; Liu, Weiping; Tang, Jieyuan; Lu, Huihui; Zhang, Jun; Luo, Yunhan; Zhong, Yongchun; Zang, Zhigang; Chen, Zhe

    2014-03-10

    A fiber surface grating (FSG) formed from a photosensitive liquid crystal hybrid (PLCH) film overlaid on a side-polished fiber (SPF) is studied and has been experimentally shown to be able to function as an all-optically reconfigurable and tunable fiber device. The device is all-optically configured to be a short period fiber surface grating (SPFSG) when a phase mask is used, and then reconfigured to be a long period FSG (LPFSG) when an amplitude mask is used. Experimental results show that both the short and long period FSGs can function as an optically tunable band-rejection filter and have different performances with different pump power and different configured period of the FSG. When configured as a SPFSG, the device can achieve a high extinction ratio (ER) of 21.5dB and a wideband tunability of 31nm are achieved. When configured as a LPFSG, the device can achieve an even higher ER of 23.4dB and a wider tunable bandwidth of 60nm. Besides these tunable performances of the device, its full width at half maximum (FWHM) can also be optically tuned. The reconfigurability and tunability of the fiber device open up possibilities for other all-optically programmable and tunable fiber devices.

  11. Performance analysis on cascaded asymmetric photonic crystal Mach-Zehnder tunable filter

    NASA Astrophysics Data System (ADS)

    Chen, Ying; Zhao, Zhiyong; Liu, Teng; He, Lei; di, Yuanjian; Cui, Xingning

    2017-02-01

    A cascaded asymmetric photonic crystal Mach-Zehnder filter structure is proposed to improve the quality factor (Q value) and the sensitivity of the tunable optical filter. The mathematical relationship between the output wavelength of M-Z filter and the voltage applied on the multilayer PZT is established. The simulation results show that the full width at half maximum can be decreased from 17 nm to 9 nm, in addition, the transmission peak wavelength varies by adjusting the applied voltage and the sensitivity can attain to 0.7 nm/V by using the multilayer PZT, which can achieve tunable filtering effectively.

  12. A method to design tunable quadrature filters in phase shifting interferometry.

    PubMed

    Mosiño, J F; Doblado, D Malacara; Hernández, D Malacara

    2009-08-31

    The main purpose of this paper is to present a method to design tunable quadrature filters in phase shifting interferometry. The algorithm is obtained from a generalized Fourier transform of a symmetrical quadrature filter. This formalism allows us to represent the detuning phase shift error and bias modulation as geometrical conditions. Therefore, the design of the filter becomes a set of solvable linear equations. Hence, to prove our method, several general tunable filters, like three and four frame algorithms, are obtained. Finally, from our results we reproduce particular symmetrical four frame algorithms reported in literature.

  13. Tunable laser diode system for noninvasive blood glucose measurements

    NASA Astrophysics Data System (ADS)

    Olesberg, Jonathon T.; Arnold, Mark A.; Mermelstein, Carmen; Schmitz, Johannes; Wagner, Joachim

    2005-03-01

    Tight control of blood glucose levels has been shown to dramatically reduce the long-term complications of diabetes. Current invasive technology for monitoring glucose levels is effective but underutilized by people with diabetes because of the pain of repeated finger-sticks and the cost of reagent strips. Optical sensing of glucose could potentially allow more frequent monitoring and tighter glucose control for people with diabetes. The key to a successful optical non-invasive measurement of glucose is the collection of an optical spectrum with a very high signal-to-noise-ratio in a spectral region with significant glucose absorption. Unfortunately, the optical throughput of skin is very small due to absorption and scattering. To overcome these difficulties, we have developed a high-brightness tunable laser system for measurements in the 2.0-2.5 μm wavelength range. The system is based on a 2.3 micron wavelength, strained quantum-well laser diode incorporating GaInAsSb wells and AlGaAsSb barrier and cladding layers. Wavelength control is provided by coupling the laser diode to an external cavity that includes an acousto-optic tunable filter. Tuning ranges of greater than 110 nm have been obtained. Because the tunable filter has no moving parts, scans can be completed very quickly, typically in less than 10 ms. We describe the performance of the laser system and its potential for use in a non-invasive glucose sensor.

  14. Quasi-4D laser diagnostics using an acousto-optic deflector scanning system

    NASA Astrophysics Data System (ADS)

    Li, Tao; Pareja, Jhon; Becker, Lukas; Heddrich, Wolfgang; Dreizler, Andreas; Böhm, Benjamin

    2017-03-01

    In this paper, a novel scanning system for laser diagnostics was developed and characterized. The system is based on the acousto-optic deflection of a high-speed pulsed laser. Results showed that quasi-volumetric laser illumination with high precision and accuracy can be achieved with a simplified and flexible optical setup. The feasibility of the method for performing high-speed quasi-4D laser diagnostics was demonstrated by the tomographic visualization of a lifted turbulent jet flame using Mie-scattering and multi-plane particle image velocimetry measurements of a turbulent non-reactive mixing case. Three-dimensional flame and flow structures can be detected and tracked with this new scanning system.

  15. Secure chaotic transmission of electrocardiography signals with acousto-optic modulation under profiled beam propagation.

    PubMed

    Almehmadi, Fares S; Chatterjee, Monish R

    2015-01-10

    Electrocardiography (ECG) signals are used for both medical purposes and identifying individuals. It is often necessary to encrypt this highly sensitive information before it is transmitted over any channel. A closed-loop acousto-optic hybrid device acting as a chaotic modulator is applied to ECG signals to achieve this encryption. Recently improved modeling of this approach using profiled optical beams has shown it to be very sensitive to key parameters that characterize the encryption and decryption process, exhibiting its potential for secure transmission of analog and digital signals. Here the encryption and decryption is demonstrated for ECG signals, both analog and digital versions, illustrating strong encryption without significant distortion. Performance analysis pertinent to both analog and digital transmission of the ECG waveform is also carried out using output signal-to-noise, signal-to-distortion, and bit-error-rate measures relative to the key parameters and presence of channel noise in the system.

  16. Acousto-Optic Modulation and Optoacoustic Gating in Piezo-Optomechanical Circuits

    NASA Astrophysics Data System (ADS)

    Balram, Krishna C.; Davanço, Marcelo I.; Ilic, B. Robert; Kyhm, Ji-Hoon; Song, Jin Dong; Srinivasan, Kartik

    2017-02-01

    Acoustic-wave devices provide a promising chip-scale platform for efficiently coupling radio frequency (rf) and optical fields. Here, we use an integrated piezo-optomechanical circuit platform that exploits both the piezoelectric and photoelastic coupling mechanisms to link 2.4-GHz rf waves to 194-THz (1550 nm) optical waves, through coupling to propagating and localized 2.4-GHz acoustic waves. We demonstrate acousto-optic modulation, resonant in both the optical and mechanical domains, in which waveforms encoded on the rf carrier are mapped to the optical field. We also show optoacoustic gating, in which the application of modulated optical pulses interferometrically gates the transmission of propagating acoustic pulses. The time-domain characteristics of this system under both pulsed rf and pulsed optical excitation are considered in the context of the different physical pathways involved in driving the acoustic waves, and modeled through the coupled mode equations of cavity optomechanics.

  17. Stabilisation of a fibre frequency synthesiser using acousto-optical and electro-optical modulators

    NASA Astrophysics Data System (ADS)

    Koliada, N. A.; Nyushkov, B. N.; Pivtsov, V. S.; Dychkov, A. S.; Farnosov, S. A.; Denisov, V. I.; Bagayev, S. N.

    2016-12-01

    A fibre-optic frequency synthesiser is developed that is stabilised to the optical frequency standard based on molecular iodine ({\\text{Nd : YAG/I}}2). The possibility of transferring stability of the optical frequency standard to other optical frequencies in the IR range 1 - 2 \\unicode{956}{\\text{m}} and to the RF range by using synthesiser phase-locked loops (PLLs) with acousto-optical and electro-optical modulators is experimentally demonstrated. The additive instability introduced into the optical frequency comb of the synthesiser (which arises due to PLL residual random errors) is several orders less than the intrinsic instability of the reference optical frequency standard employed (i.e., is noticeably less than 1 × 10-13 for 1 {\\text{s}} and 5 × 10-15 for 1000 {\\text{s}}).

  18. Research of acousto-optic correlator for new telecommunication receiver system

    NASA Astrophysics Data System (ADS)

    Shao, Dingrong; Li, Shujian; Zhou, Bin

    1994-01-01

    A promising receive system model working in high frequency and wideband, with large processing gain, is researched. As the crux, an acousto-optic correlator is discussed especially. Analyzing the principle of a bulk wave space integrating A-O correlator/convolver, an experimental signal processor with large Gp using a high frequency wideband A-O device is configured. By this system, operation of correlation/convolution with BPSK modulated by Barker code is completed. The result is in accordance with the theoretic calculation. This model works in 175 MHz center frequency, 120 MHz bandwidth, and 29.4 dB processing gain. The method of detecting the first order diffracted light beam is proved theoretically and experimentally to expend dynamic range.

  19. Mode locking of an all-fiber laser by acousto-optic superlattice modulation.

    PubMed

    Cuadrado-Laborde, C; Diez, A; Delgado-Pinar, M; Cruz, J L; Andrés, M V

    2009-04-01

    Active mode locking of an erbium-doped all-fiber laser with a Bragg-grating-based acousto-optic modulator is demonstrated. The fiber Bragg grating was acoustically modulated by a standing longitudinal elastic wave, which periodically modulates the sidebands at twice the acoustic frequency. The laser has a Fabry-Perot configuration in which cavity loss modulation is achieved by tuning the output fiber Bragg grating to one of the acoustically induced sidebands. Optical pulses at 9 MHz repetition rate, 120 mW peak power, and 780 ps temporal width were obtained. The output results to be stable and has a timing jitter below 40 ps. The measured linewidth, 2.8 pm, demonstrates that these pulses are transform limited.

  20. Spatial and temporal thermal analysis of acousto-optic deflectors using finite element analysis model.

    PubMed

    Jiang, Runhua; Zhou, Zhenqiao; Lv, Xiaohua; Zeng, Shaoqun; Huang, Zhifeng; Zhou, Huaichun

    2012-07-01

    Thermal effects greatly influence the optical properties of the acousto-optic deflectors (AODs). Thermal analysis plays an important role in modern AOD design. However, the lack of an effective method of analysis limits the prediction in the thermal performance. In this paper, we propose a finite element analysis model to analyze the thermal effects of a TeO(2)-based AOD. Both transducer heating and acoustic absorption are considered as thermal sources. The anisotropy of sound propagation is taken into account for determining the acoustic absorption. Based on this model, a transient thermal analysis is employed using ANSYS software. The spatial temperature distributions in the crystal and the temperature changes over time are acquired. The simulation results are validated by experimental results. The effect of heat source and heat convection on temperature distribution is discussed. This numerical model and analytical method of thermal analysis would be helpful in the thermal design and practical applications of AODs.

  1. Ultrasound sensing using the acousto-optic effect in polymer dispersed liquid crystals

    NASA Astrophysics Data System (ADS)

    Trushkevych, O.; Eriksson, T. J. R.; Ramadas, S. N.; Dixon, S.; Edwards, R. S.

    2015-08-01

    Acousto-optic effects are demonstrated in polymer dispersed liquid crystal (PDLC) films, showing promise for applications in ultrasound sensing. The PDLC films are used to image two displacement profiles of air-coupled flexural transducers' resonant modes at 295 kHz and 730 kHz. Results are confirmed using laser vibrometry. The regions on the transducers with the largest displacements are clearly imaged by the PDLC films, with the resolution agreeing well with laser vibrometry scanning. Imaging takes significantly less time than a scanning system (switching time of a few seconds, as compared to 8 h for laser vibrometry). Heating effects are carefully monitored using thermal imaging and are found not to be the main cause of PDLC clearing.

  2. Acousto-optic liquid-crystal analog beam former for phased-array antennas.

    PubMed

    Riza, N A

    1994-06-10

    A compact phased-array antenna acousto-optic beam former with element-level analog phase (0-2π) and amplitude control using nematic-liquid-crystal display-type technology is experimentally demonstrated. Measurements indicate > 6-bit phase control and 52.6 dB of amplitude-attenuation control. High-quality error calibration and antenna sidelobe-level control is possible with this low-control-power analog beam former. Optical system options using rf Bragg cells or wideband Bragg cells are discussed, with the rf design being the current preferred approach. Transmit-receive beam forming based on frequency upconversion-downconversion by electronic mixing is introduced for the rf Bragg-cell beam former, and comparisons with digital beam forming are highlighted. A millimeter-wave signal generation and control optical architecture is described.

  3. Exact solution for four-order acousto-optic Bragg diffraction with arbitrary initial conditions.

    PubMed

    Pieper, Ron; Koslover, Deborah; Poon, Ting-Chung

    2009-03-01

    An exact solution to the four-order acousto-optic (AO) Bragg diffraction problem with arbitrary initial conditions compatible with exact Bragg angle incident light is developed. The solution, obtained by solving a 4th-order differential equation, is formalized into a transition matrix operator predicting diffracted light orders at the exit of the AO cell in terms of the same diffracted light orders at the entrance. It is shown that the transition matrix is unitary and that this unitary matrix condition is sufficient to guarantee energy conservation. A comparison of analytical solutions with numerical predictions validates the formalism. Although not directly related to the approach used to obtain the solution, it was discovered that all four generated eigenvalues from the four-order AO differential matrix operator are expressed simply in terms of Euclid's Divine Proportion.

  4. Performance of an acousto-optic Bragg cell under ion microbeam irradiation

    SciTech Connect

    Paxton, A.H.; Schone, H.; Taylor, E.W.; McKinney, S.; Doyle, B.L.

    1997-08-01

    An acousto optic (AO) deflector composed of PbMoO{sub 4} was exposed to 4 MeV protons while operating under Bragg angle conditions. An ion beam in air of 1 mm width was directed normal to the crystal face and laser beam. Between exposures, the approximately 13 mm x 8.5 mm AO deflector was mechanically translated in two dimensions in front of the fixed ion beam. The AO diffraction efficiency was mapped and was observed to change as a function of ion beam location and dose rate. These effects are attributed to the induced change in the temperature distribution of the crystal, which changed the sonic velocity and refractive index. Similar effects were observed when the ion beam was directed at the acoustic transducer.

  5. Optical Multiplications With Single Element 2-D Acousto-Optic Laser Beam Deflector

    NASA Astrophysics Data System (ADS)

    Soos, Jolanta I.; Leepa, Douglas C.; Rosemeier, Ronald G.

    1989-05-01

    With the current need for developing very fast computers in comparison to conventional digital chip based systems, the future for optical based signal processing is very bright. Attention has turned to a different application of optics utilizing mathematical operations, in which case operations are numerical, sometimes discrete, and often algebraic in nature. Interest has been so vigorous that many view it as a small revolution in optics, whereby optical signal processing is beginning to encompass what is frequently described as optical computing. The term is fully intended to imply a close comparison with the operations performed by scientific digital canputers. This paper will describe the applications of single element 2-D acousto-optic deflectors for optical multiplication systems.

  6. Matrix operations utilizing multichannel two-dimensional acousto-optic deflector

    NASA Astrophysics Data System (ADS)

    Barocsi, Attila; Jakab, Laszlo; Richter, Peter I.

    1994-01-01

    A linear scanning light deflector, or Bragg-cell, is a widely utilized acousto-optic (AO) signal processing device. Its application is, however, limited due to its line scanning property. To overcome this deficiency an area (or matrix) scanning deflector can be built by consecutively placing two, orthogonally positioned, linear deflectors. A more sophisticated method, however, is the realization of a `monolithic' area scanning device, or 2-D (XY-) deflector, that contains a single Bragg cell. If each dimension of the cell has several input channels the element can serve as a special optical processor in various applications. In this work a multichannel XY-deflector is examined with special regard to its utilization as a fast optical crossbar switch and matrix processor. An experimental set-up with a 2 * 2 channel cell is also demonstrated.

  7. Spatial mapping of transient atomic concentrations using acousto-optic deflection

    SciTech Connect

    Huie, C.W.; Yeung, E.S.

    1986-08-01

    We report a new imaging system for obtaining spatially and temporally resolved atomic absorption profiles for transient events. This is based on an acousto-optic beam deflector that scans the probe laser beam in one dimension repeatedly across the spatial region of interest. Scan rates of 10 ..mu..s durations essentially freeze the absorbing species in time to allow a spatial resolution of 0.06 cm over a 1.2 cm length. With the use of 2K of buffer memory and a digitization interval of 200 nm (12 bits), the time evolution can be followed up to a total of 400 ..mu..s. The capabilities are demonstrated in the study of atom formation in a laser generated plume for a sodium tungstate surface.

  8. Gain-switched Ho:YAG ceramic laser with an acousto-optic modulator

    NASA Astrophysics Data System (ADS)

    Zhang, Jianing; Shen, Deyuan; Zhang, Jian; Tang, Dingyuan; Chen, Hao

    2016-04-01

    We demonstrate a gain-switched Ho:YAG ceramic laser in-band pumped by an acousto-optically modulated thulium fiber laser at ˜1908 nm. The laser pulse repetition rate could be tuned continuously from 60 to 100 kHz with the pulse energy kept constant for a certain pump power level. The shortest pulse width of 204 ns and a maximum peak power of 75 W have been obtained at 60 kHz under the maximum pump power level of 11 W. A maximum average output power of 1.4 W has been achieved with a pulse repetition rate of 100 kHz, corresponding to a slope efficiency of 57% with respect to the incident pump power. The prospects for further improvement in laser performance are discussed.

  9. Acousto-optical post-processor time-integrating correlator calibration updates

    NASA Astrophysics Data System (ADS)

    Baker, P.

    1992-02-01

    The acousto-optical signal processing facility and time integrating correlator system has been updated to allow proper handling of multiple peaks and to increase the readout rate. These modifications are described. In the supervisor task, a phase shift dialog box has been added to the phase shift menu items. This dialog box allows the operator to limit the area examined while searching for peaks or to specify the peak location directly. An amplitude offset calibration dialog box has been added to the amplitude offset menu item. This dialog box allows the operator to limit the area examined during the amplitude offset calibration, which is designed to perform calculations on a portion of the correlogram that does not contain a peak. In addition, the interface between the photodetector and personal computer has been modified to double the maximum pixel clock rate to 10 MHz.

  10. Acousto-optic gyrotropic-crystal-based modulator with a rotating polarisation vector

    NASA Astrophysics Data System (ADS)

    Kotov, V. M.; Averin, S. V.; Kotov, E. V.; Voronko, A. I.; Tikhomirov, S. A.

    2017-02-01

    We study the influence of ellipticity of gyrotropic-crystal eigenwaves on the output characteristics of an acousto-optic (AO) modulator based on the interferometer scheme. The schemes of AO modulators are considered, which provide the polarisation vector rotation frequency fn/2, where f is the frequency of the acoustic wave, and n is the integer. Preference is given to the scheme combining cascade and polarisation-independent diffraction. An experimental layout of the AO modulator operating at f = 44.5 MHz is described, the modulation frequency of the output laser light intensity being 89 MHz. The frequency of the electrical signal from the photodetector is equal to 179.5 MHz.

  11. Dynamic acousto-optic control of a strongly coupled photonic molecule

    PubMed Central

    Kapfinger, Stephan; Reichert, Thorsten; Lichtmannecker, Stefan; Müller, Kai; Finley, Jonathan J.; Wixforth, Achim; Kaniber, Michael; Krenner, Hubert J.

    2015-01-01

    Strongly confined photonic modes can couple to quantum emitters and mechanical excitations. To harness the full potential in quantum photonic circuits, interactions between different constituents have to be precisely and dynamically controlled. Here, a prototypical coupled element, a photonic molecule defined in a photonic crystal membrane, is controlled by a radio frequency surface acoustic wave. The sound wave is tailored to deliberately switch on and off the bond of the photonic molecule on sub-nanosecond timescales. In time-resolved experiments, the acousto-optically controllable coupling is directly observed as clear anticrossings between the two nanophotonic modes. The coupling strength is determined directly from the experimental data. Both the time dependence of the tuning and the inter-cavity coupling strength are found to be in excellent agreement with numerical calculations. The demonstrated mechanical technique can be directly applied for dynamic quantum gate operations in state-of-the-art-coupled nanophotonic, quantum cavity electrodynamic and optomechanical systems. PMID:26436203

  12. Prolonged acousto-optic interaction with Lamb waves in crystalline plates

    PubMed

    Parygin; Vershoubskiy; Mozhaev; Weihnacht

    2000-03-01

    The propagation and acousto-optic interaction of Lamb modes in an anisotropic plate of tellurium dioxide (TeO2) are studied numerically and analytically. In the case of a Y-cut X-propagating TeO2 plate, the very high elastic anisotropy of the crystal greatly modifies the dispersion curves, giving rise to their multiple oscillations. The existence ranges of backward Lamb modes increase with the mode order contrary to the case of isotropic plates. The quasi-collinear light scattering by Lamb waves is considered. Owing to the structure of Lamb wave field, a simultaneous light diffraction at two different optical frequencies can take place while Lamb waves are excited only at the single frequency. It is demonstrated with the Z-cut (110)-propagating plate that a small change in the acoustic frequency can result in a significant shift in the frequency of the scattered light.

  13. Time and space integrating acousto-optic folded spectrum processing for SETI

    NASA Technical Reports Server (NTRS)

    Wagner, K.; Psaltis, D.

    1986-01-01

    Time and space integrating folded spectrum techniques utilizing acousto-optic devices (AOD) as 1-D input transducers are investigated for a potential application as wideband, high resolution, large processing gain spectrum analyzers in the search for extra-terrestrial intelligence (SETI) program. The space integrating Fourier transform performed by a lens channels the coarse spectral components diffracted from an AOD onto an array of time integrating narrowband fine resolution spectrum analyzers. The pulsing action of a laser diode samples the interferometrically detected output, aliasing the fine resolution components to baseband, as required for the subsequent charge coupled devices (CCD) processing. The raster scan mechanism incorporated into the readout of the CCD detector array is used to unfold the 2-D transform, reproducing the desired high resolution Fourier transform of the input signal.

  14. Tunable first-order resistorless all-pass filter with low output impedance.

    PubMed

    Beg, Parveen

    2014-01-01

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

  15. Self-acousto-optic modulation and orthogonality violation in the transverse modes of a broad-area Nd-doped yttrium-aluminum-garnet single-shot laser

    SciTech Connect

    Soler Rus, M. Odin; Cabrera-Granado, E.; Guerra Perez, J. M.

    2011-05-15

    Self-acousto-optic Raman-Nath modulation and nonorthogonal transversal modes are found in a broad-area Nd:YAG single-shot laser. The device is free from the thermal-induced effects previously related to orthogonality violation and the acousto-optic modulation comes from a shock wave produced by the discharge of the flash lamps that optically pump the laser. The experimental findings are reproduced by a general model of a class B laser.

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

    PubMed

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

    2014-12-01

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

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

    PubMed

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

    2014-03-15

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

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

    PubMed

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

    2015-08-01

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

  19. Widely tunable mode-locked fiber laser using carbon nanotube and LPG W-shaped filter.

    PubMed

    Wang, Jie; Zhang, A Ping; Shen, Yong Hang; Tam, Hwa-yaw; Wai, P K A

    2015-09-15

    A widely tunable mode-locked fiber laser using a carbon nanotube absorber and a fiber-optic W-shaped spectral filter is presented. The W-shaped filter is constructed by sandwiching a phase-shifted long-period grating between two LPGs of different periods. By adjusting the temperature of the W-shaped filter from 23°C to 100°C, the central wavelength of the mode-locked fiber laser can be continuously tuned from 1597 to 1553 nm. The tuning range is further extended to 1531.6 nm when a shorter erbium-doped fiber is used in the fiber oscillator. The experimental results reveal that the large thermal tunability of the proposed LPG filter provides an effective approach to achieve compact widely tunable mode-locked fiber lasers covering both C and L bands.

  20. Acousto-optical pulsar processor frequency scale calibration for increase accuracy measurement of time of arrival radioemission impulses

    NASA Astrophysics Data System (ADS)

    Esepkina, Nelli A.; Lavrov, Aleksandr P.; Molodyakov, Sergey A.

    2006-04-01

    The acousto-optical processor (AOP) is based on an acousto-optical spectrum analyzer with a CCD photodetector operating in special pipeline mode (shift-and-add mode), which allows spectral components of the input signal to be added with controlled time delay immediately in the CCD photodetector. The proposed AOP was successfully used on radiotelescope RT-64 (Kalyazin Radio Astronomy Observatory FIAN) for the observation of pulsars at 1 .4 GHz in 45 MHz bandwidth. The AOP frequency scale calibration allows increasing accuracy of measurement of time of arrival radioemission pulses. Experimental results on investigation of AOP work on RT-64 and radioemission pulses profiles for pulsar PSR 1937+21 are submitted.

  1. Algorithm of Shaping Multiple-beam Braggs Acousto-optic Diffraction Laser Field Into 1D and 2D Patterns

    NASA Astrophysics Data System (ADS)

    Zakharchenko, S.; Baturin, A.

    2015-09-01

    Algorithm of solving a direct problem of acousto-optic interaction between laser emission and acoustic signal consisting of a set of equidistant frequency components is proposed. An infinite system of coupled wave differential equations is reduced to eigenvalue problem. The contribution of the higher rediffraction orders is analyzed separately. Inverse problem of finding an optimal set of equidistant frequency components of a driving acoustic signal to form the objective diffraction pattern is also considered and a few optimization approaches are analyzed. A naïve heuristic method of splitting 2D pattern into subframes, each suitable for simultaneous projection by two acousto-optical deflectors driven by multifrequency composite signal, is developed.

  2. Experimental analysis of distributed pump absorption and refractive index changes in Yb-doped fibers using acousto-optic interaction.

    PubMed

    Alcusa-Sáez, E P; Díez, A; Andrés, M V

    2015-03-01

    In-fiber acousto-optic interaction is used to characterize the refractive index changes at the C band in a single-mode ytterbium-doped optical fiber under 980 nm pumping. The transmission notch created by the acoustic-induced coupling between the core mode and a cladding mode shifts to longer wavelengths when the pump is delivered to the fiber. The electronic contribution to the refractive index change is quantified from the wavelength shift. Using a time-resolved acousto-optic method, we investigate the distribution of pump absorption, and the resulting refractive index change profile, along sections of ytterbium-doped fiber exceeding 1 m long under different pump power levels.

  3. An acousto-optical method for registration of erythrocytes' agglutination reaction—sera color influence on the resolving power

    NASA Astrophysics Data System (ADS)

    Doubrovski, V. A.; Medvedeva, M. F.; Torbin, S. O.

    2016-01-01

    The absorption spectra of agglutinating sera were used to determine blood groups. It was shown experimentally that the sera color significantly affects the resolving power of the acousto-optical method of blood typing. In order to increase the resolving power of the method and produce an invariance of the method for sera color, we suggested introducing a probing light beam individually for different sera. The proposed technique not only improves the resolving power of the method, but also reduces the risk of false interpretation of the experimental results and, hence, error in determining the blood group of the sample. The latter is especially important for the typing of blood samples with weak agglutination of erythrocytes. This study can be used in the development of an instrument for instrumental human blood group typing based on the acousto-optical method.

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

    NASA Astrophysics Data System (ADS)

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

    2011-02-01

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

  5. Analytical study of acousto/optical holography-interfacing methods for acoustical and optical holography NDT research

    NASA Technical Reports Server (NTRS)

    El-Sum, H. M. A.

    1976-01-01

    The international status of the art of acousto optical imaging techniques adaptable to nondestructive testing and, interfacing methods for acoustical and optical holography in nondestructive testing research are studied. Evaluation of 20 different techniques encompassed investigation of varieties of detectors and detection schemes, all of which are described and summarized. Related investigation is reported in an Appendix. Important remarks on image quality, factors to be considered in designing a particular system, and conclusions and recommendations are presented. Three bibliographies are included.

  6. Optical-mechanical operation of the F2T2 filter: a tunable filter designed to search for First Light

    NASA Astrophysics Data System (ADS)

    Mentuch, Erin; Scott, Alan; Abraham, Roberto; Barton, Elizabeth; Bershady, Matthew; Bland-Hawthorn, Joss; Crampton, David; Doyon, René; Eikenberry, Steve; Gladders, Mike; Glazebrook, Karl; Jenson, Joe; Julian, Jeff; Julian, Roger; Kneib, Jean-Paul; Loop, David; Raines, Nick; Rowlands, Neil; Smith, J. D.

    2008-07-01

    The Flamingos-2 Tandem Tunable filter is a tunable, narrow-band filter, consisting of two Fabry-Perot etalons in series, capable of scanning to any wavelength from 0.95 to 1.35 microns with a spectral resolution of R~800. It is an accessory mode instrument for the near-IR Flamingos-2 imaging-spectrograph designed for the Gemini South 8m Observatory and will be fed through the upcoming Multi-Conjugate Adaptive Optics feed. The primary science goal of the F2T2 filter is to perform a ground-based search for the first star forming regions in the universe at redshifts of 7 < z < 11. The construction of the F2T2 filter is complete and it is currently in its calibration and commissioning phases. In this proceeding, we describe the calibration and performance of the instrument.

  7. Calomel-made crystalline acousto-optical cell designed for an advanced regime of noncollinear two-phonon light scattering

    NASA Astrophysics Data System (ADS)

    Shcherbakov, Alexandre S.; Arellanes, Adan Omar

    2016-03-01

    We study the potentials of a wide-aperture crystalline calomel-made acousto-optical cell. Characterizing this cell is nontrivial due to the chosen regime based on an advanced noncollinear two-phonon light scattering. Recently revealed important features of this phenomenon are essentially exploited in the cell and are investigated in more detail. These features can be observed more easily and simply in tetragonal crystals, e.g., calomel, exhibiting specific acousto-optical nonlinearity caused by the acoustic waves of finite amplitude. This parametric nonlinearity manifests itself at low acoustic powers in calomel possessing linear acoustic attenuation. The formerly identified additional degree of freedom, unique to this regime, is exploited for designing the cell with an eye to doubling the resolution due to two-phonon processes. We clarify the role of varying the central acoustic frequency and acoustic attenuation using that degree of freedom. Then the efficiency of calomel is exploited to expand the cell's bandwidth with a cost of its efficiency. Proof-of-principle experiments confirm the developed approaches and illustrate their applicability to innovative techniques of optical spectrum analysis with the improved resolution. The achieved spectral resolution of 0.205 Å at 405 nm and the resolving power 19,800 are the best for acousto-optical spectrometers dedicated to space or airborne operations to date as far as we know.

  8. Single Element 2-DIMENSIONAL Acousto-Optic Deflectors Design, Fabrication and Implementation for Digital Optical Computing

    NASA Astrophysics Data System (ADS)

    Rosemeier, Jolanta Iwona

    1992-09-01

    With the need to develop very fast computers compared to the conventional digital chip based systems, the future is very bright for optical based signal processing. Attention has turned to a different application of optics utilizing mathematical operations, in which case operations are numerical, sometimes discrete, and often algebraic in nature. Interest has been so vigorous that many view it as a small revolution in optics whereby optical signal processing is beginning to encompass what many frequently describe as optical computing. The term is fully intended to imply close comparison with the operations performed by scientific digital computers. Most present computer intensive problem solving processors rely on a common set of linear equations found in numerical matrix algebra. Recently, considerable research focused on the use of systolic array, which can operate at high speeds with great efficiency. This approach addresses the acousto-optic digital and analog arrays utilizing three dimensional optical interconnect technology. In part I of this dissertation the first single element 2-dimensional (2-D) acousto-optic deflector was designed, fabricated and incorporated into an optical 3 x 3 vector-vector or matrix-matrix multiplier system. This single element deflector is used as a outer-product device. The input vectors are addressed by electronic means and the outer product matrix is displayed as a 2-D array of optical (laser) pixels. In part II of this work a multichannel single element 2-D deflector was designed, fabricated and implemented into a Programmable Logic Array (PLA) optical computing system. This system can be used for: word equality detection, free space optical interconnections, half adder optical system implementation. The PLA system described in this dissertation has capability of word equality detection. The 2-D multichannel deflector that was designed and fabricated is capable of comparing 16 x 16 words every 316 nanoseconds. Each word is 8

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  10. 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.

  11. LD-pumped acousto-optical Q-switched burst-mode Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Pan, Hu; Yan, Renpeng; Li, Xudong; Ma, Yufei; Yu, Xin; Chen, Deying

    2016-04-01

    A high-repetition-rate, high-peak-power burst-mode laser for laser-based measurement applications is presented by using a master oscillator power amplifier structure. An laser diode arrays (LDA) side-pumped Nd:YAG acousto-optical (A-O) Q-switched laser serves as the master oscillator. Under pulsed pumping, pulse trains with 2-25 pulses are obtained when the repetition rate changes from 10 kHz to 100 kHz. The maximum pulse burst energy of 31.2 mJ is achieved in the A-O Q-switched pulse burst laser oscillator at 10 kHz. Two LDA side pumped Nd:YAG modules are employed in the amplification stage. After the amplification, the pulse burst energy at 10 kHz reaches ~170 mJ with a single pulse energy of 85.2 mJ and a pulse width of 14.5 ns, generating a peak power of 6.1 MW. At 100 kHz, the total burst energy reaches 220 mJ with a single pulse energy of 8.8 mJ in the pulse burst laser system.

  12. High repetition rate laser-induced breakdown spectroscopy using acousto-optically gated detection

    SciTech Connect

    Pořízka, Pavel; Kaiser, Jozef

    2014-07-15

    This contribution introduces a new type of setup for fast sample analysis using laser-induced breakdown spectroscopy (LIBS). The novel design combines a high repetition rate laser (up to 50 kHz) as excitation source and an acousto-optical modulator (AOM) as a fast switch for temporally gating the detection of the emitted light. The plasma radiation is led through the active medium of the AOM where it is diffracted on the transient ultrasonic Bragg grid. The diffracted radiation is detected by a compact Czerny-Turner spectrometer equipped with a CCD line detector. Utilizing the new combination of high repetition rate lasers and AOM gated detection, rapid measurements with total integration times of only 10 ms resulted in a limit of detection (LOD) of 0.13 wt.% for magnesium in aluminum alloys. This short integration time corresponds to 100 analyses/s. Temporal gating of LIP radiation results in improved LODs and consecutively higher sensitivity of the LIBS setup. Therefore, an AOM could be beneficially utilized to temporally detect plasmas induced by high repetition rate lasers. The AOM in combination with miniaturized Czerny-Turner spectrometers equipped with CCD line detectors and small footprint diode pumped solid state lasers results in temporally gateable compact LIBS setups.

  13. Theoretical calculation and experimental study of acousto-optically Q-switched CO2 laser.

    PubMed

    Xie, Jijang; Guo, Ruhai; Li, Dianjun; Zhang, Chuansheng; Yang, Guilong; Geng, Yumin

    2010-06-07

    Using resonator inserted with acousto-optically modulator, the experiments of the compacted CO(2) laser were performed with Q-switch. According to various factors that influenced the output of laser, the theoretical calculation of its main parameters was conducted by Q-switched pulsed laser rate equations. Based on the results, the technical route and approach were presented for optimization design of this laser. The measured peak power of this laser device was more than 4000W and pulsed width was 180ns which agreed well with the theoretical calculation. The range of repetition frequency could adjust from 1 Hz to 100 kHz. The theoretical analyzes and experimental results showed that the acoustic traveling time of ultrasonic field could not influence the pulse width of laser so that it did not require inserting optical lens in the cavity to reduce the diameter of beam. The acoustic traveling time only extended the establishingtime of laser pulse. The optimum working frequency of laser is about 1 kHz, which it matched with the radiation life time (1 ms) of CO(2) molecular upper energy level. When the frequency is above 1 kHz, the pulse width of laser increased with the frequency. The full band of wavelength tuning between 9.2 microm and 10.8 microm was obtained by grating selection one by one which the measured spectrum lines were over 30 in the condition of Q-switch.

  14. State-of-the art of acousto-optic sensing and imaging of turbid media.

    PubMed

    Resink, Steffen G; Boccara, Albert C; Steenbergen, Wiendelt

    2012-04-01

    Acousto-optic (AO) is an emerging hybrid technique for measuring optical contrast in turbid media using coherent light and ultrasound (US). A turbid object is illuminated with a coherent light source leading to speckle formation in the remitted light. With the use of US, a small volume is selected,which is commonly referred to as the "tagging" volume. This volume acts as a source of modulated light, where modulation might involve phase and intensity change. The tagging volume is created by focusing ultrasound for good lateral resolution; the axial resolution is accomplished by making either the US frequency, amplitude, or phase time-dependent. Typical resolutions are in the order of 1 mm. We will concentrate on the progress in the field since 2003. Different schemes will be discussed to detect the modulated photons based on speckle detection, heterodyne detection, photorefractive crystal (PRC) assisted detection, and spectral hole burning (SHB) as well as Fabry-Perot interferometers. The SHB and Fabry-Perot interferometer techniques are insensitive to speckle decorrelation and therefore suitable for in vivo imaging. However, heterodyne and PRC methods also have potential for in vivo measurements. Besides measuring optical properties such as scattering and absorption, AO can be applied in fluorescence and elastography applications.

  15. The effect of scattering-medium parameters on signal magnitude under acousto-optic tomography

    NASA Astrophysics Data System (ADS)

    Zyuryukina, O. V.; Volkova, E. K.; Perchenko, M. I.; Solov'ev, A. P.

    2014-04-01

    We have experimentally studied the influence of scattering anisotropy parameter g of a medium on the magnitude of signal S (visualization parameter) at an ultrasonic frequency that is registered upon acoustooptic tomography. Aqueous solutions of mixtures of cream and skimmed milk with different ratios between them were used as scattering media. The optical properties of media (absorption coefficient μa and reduced scattering coefficient μ' S ) have been measured on a spectrophotometer (Perkin-Elmer Lambda 950 UV-VIS-NIR) using the inverse adding-doubling technique. As a result of the investigation, we have found that there is a certain correlation between the value of the scattering anisotropy parameter g of aqueous solutions of investigated mixtures and the percentage of the mixture in the aqueous solution, which ensures the required small value of extinction coefficient μ of the scattering medium. An increase in signal S has been revealed with increasing anisotropy parameter g of the medium at a invariable value of extinction coefficient μ. We have concluded that, to solve an inverse problem on the acousto-optic tomography, it is necessary to take into account possible changes in the g factor in scattering media, including biological ones.

  16. Compensation of temporal and spatial dispersion for multiphoton acousto-optic laser-scanning microscopy

    NASA Astrophysics Data System (ADS)

    Iyer, Vijay; Saggau, Peter

    2003-10-01

    In laser-scanning microscopy, acousto-optic (AO) deflection provides a means to quickly position a laser beam to random locations throughout the field-of-view. Compared to conventional laser-scanning using galvanometer-driven mirrors, this approach increases the frame rate and signal-to-noise ratio, and reduces time spent illuminating sites of no interest. However, random-access AO scanning has not yet been combined with multi-photon microscopy, primarily because the femtosecond laser pulses employed are subject to significant amounts of both spatial and temporal dispersion upon propagation through common AO materials. Left uncompensated, spatial dispersion reduces the microscope"s spatial resolution while temporal dispersion reduces the multi-photon excitation efficacy. In previous work, we have demonstrated, 1) the efficacy of a single diffraction grating scheme which reduces the spatial dispersion at least 3-fold throughout the field-of-view, and 2) the use of a novel stacked-prism pre-chirper for compensating the temporal dispersion of a pair of AODs using a shorter mechanical path length (2-4X) than standard prism-pair arrangements. In this work, we demonstrate for the first time the use of these compensation approaches with a custom-made large-area slow-shear TeO2 AOD specifically suited for the development of a high-resolution 2-D random-access AO scanning multi-photon laser-scanning microscope (AO-MPLSM).

  17. Analysis of the dispersion compensation of acousto-optic deflectors used for multiphoton imaging.

    PubMed

    Zeng, Shaoqun; Lv, Xiaohua; Bi, Kun; Zhan, Cheng; Li, Derong; Chen, Wei R; Xiong, Wenhui; Jacques, Steven L; Luo, Qingming

    2007-01-01

    The acousto-optic deflector (AOD) is highly preferred in laser scanning microscopy for its fast scanning ability and random-addressing capability. However, its application in two-photon microscopy is frustrated by the dispersion of the AOD, which results in beam distortion and pulse lengthening. We report the analysis of simultaneous compensation for the angular dispersion and temporal dispersion of the AOD by merely introducing a single dispersive element such as a prism or a grating. Besides serving as a scanner, the AOD is also a part of the compressor pair by integrating the dispersive nature of the AO interaction. This compensation principle is effective for both one-dimensional (1-D) AOD and two-dimensional (2-D) AOD scanning. Switching from a 1-D to a 2-D system requires proper optical alignment with the compensation element, but does not involve any new components. Analytical expressions are given to illustrate the working principle and to help with understanding the design of the system. Fluorescence images of beads and cells are shown to demonstrate the performance of two-photon microscopy when applying this compensated 2-D AOD as scanner.

  18. Post-Flight Test Results of Acousto-Optic Modulator Devices Subjected to Space Exposure

    NASA Technical Reports Server (NTRS)

    Prasad, Narasimha S.; Trivedi, Sudhir; Rosemeier, Jolanta; Diestler, Mark

    2014-01-01

    The objective of the Materials International Space Station Experiment (MISSE) is to study the performance of novel materials when subjected to the synergistic effects of the harsh space environment for several months. MISSE missions provide an opportunity for developing space qualifiable materials. Several laser and lidar components were sent by NASA Langley Research Center (LaRC) as a part of the MISSE 7 mission. The MISSE 7 module was transported to the international space station (ISS) via STS 129 mission that was launched on Nov 16, 2009. Later, the MISSE 7 module was brought back to the earth via the STS 134 that landed on June 1, 2011. The MISSE 7 module that was subjected to exposure in a space environment for more than one and a half years included fiber laser, solid-state laser gain materials, detectors, and semiconductor laser diode. Performance testing of these components is now progressing. In this paper, the results of performance testing of a laser diode module sent by NASA Langley Research Center on MISSE 7 mission will be discussed. This paper will present the comparison of pre-flight and post-flight performance of two different COTS acousto-optic modulator (AOM) devices. Post-flight measurements indicate that these two devices did not undergo any significant performance degradation.

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

    NASA Astrophysics Data System (ADS)

    Nicolescu, Elena

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  1. Back-to-back tunable ferroelectric resonator filters on flexible organic substrates.

    PubMed

    Courrèges, Stanis; Lacroix, Benjamin; Amadjikpe, Arnaud; Phillips, Stan; Zhao, Zhiyong; Choi, Kwang; Hunt, Andrew; Papapolymerou, John

    2010-06-01

    This paper presents the design and the fabrication of two low-loss X-band back-to-back tunable ferroelectric resonator filters on flexible liquid crystal polymer substrates using wire-bonded BST capacitors as analog tuning elements. The back-to-back topology consists of three resonators on both sides of the substrate coupled by apertures in their common ground plane, allowing the overall size of the filter to be reduced. BST varactors made on a sapphire substrate are easily diced and mounted on the polymer substrates to achieve the desired tuning. Both 3-pole tunable filters show a 1-dB bandwidth of 8 to 10%, low insertion loss (3.6 to 1.95 dB for the best one) with bias voltages from 0 to 35 V, a better compactness compared with classical tunable structures (reduced footprint area by 30% for the best filter) and a frequency tuning of about 11 to 13% at 8 GHz. The demonstrated feasibility opens interesting prospects for the fabrication of compact tunable filters with more resonators.

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

    PubMed

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

    2013-07-15

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

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

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  4. Liquid crystal tunable light filters for surveillance and remote sensing applications

    NASA Astrophysics Data System (ADS)

    Foukal, Peter V.; Miller, Peter J.; Hoyt, Clifford C.

    1993-11-01

    In this paper we put forward some conceptual designs for liquid crystal tunable filters (LCTF's) that offer improved wavelength flexibility, tuning speed, power consumption and reliability, over the mechanical filter wheels presently baselined for the High Resolution Earth Processing Imager (HEPI) and Advanced Lightning Mapper (ALM) geosynchronous remote sensing experiments. We also point out advantages that accrue from the extremely wide acceptance angle (F 1) achievable with birefringent filters. Thermal vacuum testing and radiation damage analysis will be required to investigate the space hardening of these new filters.

  5. Non-resonant parametric amplification in biomimetic hair flow sensors: Selective gain and tunable filtering

    NASA Astrophysics Data System (ADS)

    Droogendijk, H.; Bruinink, C. M.; Sanders, R. G. P.; Krijnen, G. J. M.

    2011-11-01

    We demonstrate that the responsivity of flow sensors for harmonic flows can be improved significantly by non-resonant parametric amplification. Using electrostatic spring softening by AC-bias voltages, increased responsivity and sharp filtering are achieved in our biomimetic flow sensors. Tunable filtering is obtained for non-resonant electromechanical parametric amplification, applicable at a wide range of non-resonant frequencies while achieving highly selective gain of up to 20 dB.

  6. Lumped-equivalent circuit model for multi-stage cascaded magnetoelectric dual-tunable bandpass filter

    NASA Astrophysics Data System (ADS)

    Zhang, Qiu-Shi; Zhu, Feng-Jie; Zhou, Hao-Miao

    2015-10-01

    A lumped-equivalent circuit model of a novel magnetoelectric tunable bandpass filter, which is realized in the form of multi-stage cascading between a plurality of magnetoelectric laminates, is established in this paper for convenient analysis. The multi-stage cascaded filter is degraded to the coupling microstrip filter with only one magnetoelectric laminate and then compared with the existing experiment results. The comparison reveals that the insertion loss curves predicted by the degraded circuit model are in good agreement with the experiment results and the predicted results of the electromagnetic field simulation, thus the validity of the model is verified. The model is then degraded to the two-stage cascaded magnetoelectric filter with two magnetoelectric laminates. It is revealed that if the applied external bias magnetic or electric fields on the two magnetoelectric laminates are identical, then the passband of the filter will drift under the changed external field; that is to say, the filter has the characteristics of external magnetic field tunability and electric field tunability. If the applied external bias magnetic or electric fields on two magnetoelectric laminates are different, then the passband will disappear so that the switching characteristic is achieved. When the same magnetic fields are applied to the laminates, the passband bandwidth of the two-stage cascaded magnetoelectric filter with two magnetoelectric laminates becomes nearly doubled in comparison with the passband filter which contains only one magnetoelectric laminate. The bandpass effect is also improved obviously. This research will provide a theoretical basis for the design, preparation, and application of a new high performance magnetoelectric tunable microwave device. Project supported by the National Natural Science Foundation of China (Grant Nos. 11172285 and 11472259) and the Natural Science Foundation of Zhejiang Province, China (Grant No. LR13A020002).

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

    PubMed

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

    2016-02-23

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

  8. Acousto-optic, point receiver hydrophone probe for operation up to 100 MHz.

    PubMed

    Lewin, P A; Mu, C; Umchid, S; Daryoush, A; El-Sherif, M

    2005-12-01

    This work describes the results of initial evaluation of a wideband acousto-optic hydrophone probe designed to operate as point receiver in the frequency range up to 100 MHz. The hydrophone was implemented as a tapered fiber optic (FO) probe sensor with a tip diameter of approximately 7 microm. Such small physical dimensions of the sensor eliminate the need for spatial averaging corrections so that true pressure-time (p-t) waveforms can be faithfully recorded. The theoretical considerations that predicted the FO probe sensitivity to be equal to 4.3 mV/MPa are presented along with a brief description of the manufacturing process. The calibration results that verified the theoretically predicted sensitivity are also presented along with a brief description of the improvements being currently implemented to increase this sensitivity level by approximately 20 dB. The results of preliminary measurements indicate that the fiber optic probes will exhibit a uniform frequency response and a zero phase shift in the frequency range considered. These features might be very useful in rapid complex calibration i.e. determining both magnitude and phase response of other hydrophones by the substitution method. Also, because of their robust design and linearity, these fiber optic hydrophones could also meet the challenges posed by high intensity focused ultrasound (HIFU) and other therapeutic applications. Overall, the outcome of this work shows that when fully developed, the FO probes will be well suited for high frequency measurements of ultrasound fields and will be able to complement the data collected by the current finite aperture piezoelectric PVDF hydrophones.

  9. Acousto-optical deflection-based laser beam scanning for fluorescence detection on multichannel electrophoretic microchips.

    PubMed

    Huang, Z; Munro, N; Hühmer, A F; Landers, J P

    1999-12-01

    Laser beam scanning driven by an acousto-optical deflector (AOD) is presented for multimicrochannel laser-induced fluorescence (LIF) detection during microchip-based electrophoresis. While fast laser beam scanning for LIF detection on capillary or microchannel arrays can been achieved with galvanometric scanning or a translating stage, it can also be accomplished by using acoustic waves to deflect the laser beam in a manner that is dependent on the acoustic frequency. AOD scanning differs from other approaches in that no moving parts are required, and the scan frequency is faster than conventional approaches. Using a digital/analog (D/A) converter to provide addressing voltages to a voltage/frequency converter, rapidly changing the frequency input to the AOD allows the laser beam to be addressed accurately on a microchip. With the ability to change the frequency on the nanosecond time scale, scanning rates as high as 30 Hz for Windows-based LabView programming are possible, with much faster scan rates achievable if a microprocessor-embedded system is utilized. In addition to spatial control, temporal control is easily attainable via raster scanning or random addressing, allowing for the scanning process to be self-aligning. Since the D/A output voltages drive the scanning of the laser beam over all channels, the software can define addressing voltages corresponding to the microchannel centers and, subsequently, fluorescence data can be collected from only those locations. This method allows for flexible, high-speed, self-align scanning for fluorescence detection in capillary or microchip electrophoresis and has the potential to be applied to a number of applications.

  10. Development of fast two-dimensional standing wave microscopy using acousto-optic deflectors

    NASA Astrophysics Data System (ADS)

    Gliko, Olga; Reddy, Duemani G.; Brownell, William E.; Saggau, Peter

    2008-02-01

    A novel scheme for two-dimensional (2D) standing wave fluorescence microscopy (SWFM) using acousto-optic deflectors (AODs) is proposed. Two laser beams were coupled into an inverted microscope and focused at the back focal plane of the objective lens. The position of each of two beams at the back focal plane was controlled by a pair of AODs. This resulted in two collimated beams that interfered in the focal plane, creating a lateral periodic excitation pattern with variable spacing and orientation. The phase of the standing wave pattern was controlled by phase delay between two RF sinusoidal signals driving the AODs. Nine SW patterns of three different orientations about the optical axis and three different phases were generated. The excitation of the specimen using these patterns will result in a SWFM image with enhanced 2D lateral resolution with a nearly isotropic effective point-spread function. Rotation of the SW pattern relative to specimen and varying the SW phase do not involve any mechanical movements and are only limited by the time required for the acoustic wave to fill the aperture of AOD. The resulting total acquisition time can be as short as 100 µs and is only further limited by speed and sensitivity of the employed CCD camera. Therefore, this 2D SWFM can provide a real time imaging of subresolution processes such as docking and fusion of synaptic vesicles. In addition, the combination of 2D SWFM with variable angle total internal reflection (TIR) can extend this scheme to fast microscopy with enhanced three-dimensional (3D) resolution.

  11. Depth discrimination in acousto-optic cerebral blood flow measurement simulation

    NASA Astrophysics Data System (ADS)

    Tsalach, A.; Schiffer, Z.; Ratner, E.; Breskin, I.; Zeitak, R.; Shechter, R.; Balberg, M.

    2016-03-01

    Monitoring cerebral blood flow (CBF) is crucial, as inadequate perfusion, even for relatively short periods of time, may lead to brain damage or even death. Thus, significant research efforts are directed at developing reliable monitoring tools that will enable continuous, bed side, simple and cost-effective monitoring of CBF. All existing non invasive bed side monitoring methods, which are mostly NIRS based, such as Laser Doppler or DCS, tend to underestimate CBF in adults, due to the indefinite effect of extra-cerebral tissues on the obtained signal. If those are to find place in day to day clinical practice, the contribution of extra-cerebral tissues must be eliminated and data from the depth (brain) should be extracted and discriminated. Recently, a novel technique, based on ultrasound modulation of light was developed for non-invasive, continuous CBF monitoring (termed ultrasound-tagged light (UTL or UT-NIRS)), and shown to correlate with readings of 133Xe SPECT and laser Doppler. We have assembled a comprehensive computerized simulation, modeling this acousto-optic technique in a highly scattering media. Using the combination of light and ultrasound, we show how depth information may be extracted, thus distinguishing between flow patterns taking place at different depths. Our algorithm, based on the analysis of light modulated by ultrasound, is presented and examined in a computerized simulation. Distinct depth discrimination ability is presented, suggesting that using such method one can effectively nullify the extra-cerebral tissues influence on the obtained signals, and specifically extract cerebral flow data.

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

    PubMed

    Kriegel, Ilka; Scotognella, Francesco

    2015-01-01

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

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

    PubMed Central

    Kriegel, Ilka

    2015-01-01

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

  14. Effect of Selectively Etched Ferroelectric Thin-Film Layer on the Performance of a Tunable Bandpass Filter

    NASA Technical Reports Server (NTRS)

    Subramanyam, Guru; Vignesparamoorthy, Sivaruban; Mueller, Carl; VanKeuls, Fred; Warner, Joseph; Miranda, Felix A.

    2001-01-01

    The main purpose of this work is to study the effect of a selectively etched ferroelectric thin film layer on the performance of an electrically tunable filter. An X-band tunable filter was designed, fabricated and tested on a selectively etched Barium Strontium Titanate (BSTO) ferroelectric thin film layer. Tunable filters with varying lengths of BSTO thin-film in the input and output coupling gaps were modeled, as well as experimentally tested. Experimental results showed that filters with coupling gaps partially filled with BSTO maintained frequency tunability and improved the insertion loss by approx. 2dB. To the best of our knowledge, these results represent the first experimental demonstration of the advantages of selective etching in the performance of thin film ferroelectric-based tunable microwave components.

  15. Development and application of a ray-based model of light propagation through a spherical acousto-optic lens.

    PubMed

    Evans, Geoffrey J; Kirkby, Paul A; Naga Srinivas Nadella, K M; Marin, Bóris; Angus Silver, R

    2015-09-07

    A spherical acousto-optic lens (AOL) consists of four acousto-optic deflectors (AODs) that can rapidly and precisely control the focal position of an optical beam in 3D space. Development and application of AOLs has increased the speed at which 3D random access point measurements can be performed with a two-photon microscope. This has been particularly useful for measuring brain activity with fluorescent reporter dyes because neuronal signalling is rapid and sparsely distributed in 3D space. However, a theoretical description of light propagation through AOLs has lagged behind their development, resulting in only a handful of simplified principles to guide AOL design and optimization. To address this we have developed a ray-based computer model of an AOL incorporating acousto-optic diffraction and refraction by anisotropic media. We extended an existing model of a single AOD with constant drive frequency to model a spherical AOL: four AODs in series driven with linear chirps. AOL model predictions of the relationship between optical transmission efficiency and acoustic drive frequency including second order diffraction effects closely matched experimental measurements from a 3D two-photon AOL microscope. Moreover, exploration of different AOL drive configurations identified a new simple rule for maximizing the field of view of our compact AOL design. By providing a theoretical basis for understanding optical transmission through spherical AOLs, our open source model is likely to be useful for comparing and improving different AOL designs, as well as identifying the acoustic drive configurations that provide the best transmission performance over the 3D focal region.

  16. Experimental research on the multi-order acousto-optic diffraction based on Raman-Nath diffraction

    NASA Astrophysics Data System (ADS)

    Gu, Huadong; Shao, Zhongxing; Zheng, Chenqi; Yang, Jie; Chen, Ruitao; Gu, Zetong

    2015-03-01

    In this paper, the experimental investigation on the interaction length for getting the optimum diffraction of the multi-order acousto-optic diffraction is presented. Based on these results, the feasibility of acousto-optic Q-switch taking H2O or TeO2 as medium respectively for ultraviolet and visible lasers are discussed. The fact that the optimum interaction length tightly relies on the frequency of the sound and does not relate to the wavelength and power of the light is found in the experiment. The interaction length will become longer as the frequency of the ultrasound becomes higher. The interaction length is about 8mm when the acoustic frequency is at about 9MHz and becomes about 4mm at 6MHz. A Q-switch that works with pure water is designed and a total diffractive efficiency of about 98% was obtained under the condition that the acoustic frequency is 9MHz and the acoustic power is 3.4W. An acousto-optic Q-switch made of TeO2, in terms of Raman-Nath diffraction is designed. With a cooling system on the device, a total diffractive efficiency of about 75% is obtained under the condition that the acoustic frequency is 10MHz and the acoustic power is 10W. The loss by one path of the device is about 5% on the best condition. Then the modulated pulse width is measured as about 200ns on the condition that the acoustic frequency is 11MHz, the acoustic power is 6W and the repetition frequency is 10kHz.

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

    SciTech Connect

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

    2013-05-24

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

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

    PubMed

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

    2013-07-21

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

  19. Secure transmission of static and dynamic images via chaotic encryption in acousto-optic hybrid feedback with profiled light beams

    NASA Astrophysics Data System (ADS)

    Chatterjee, Monish R.; Almehmadi, Fares S.

    2015-01-01

    Secure information encryption via acousto-optic (AO) chaos with profiled optical beams indicates substantially better performance in terms of system robustness. This paper examines encryption of static and time-varying (video) images onto AO chaotic carriers using Gaussian-profile beams with diffracted data numerically generated using transfer functions. The use of profiled beams leads to considerable improvement in the encrypted signal. While static image encryption exhibits parameter tolerances within about +/-10% for uniform optical beams, profiled beams reduce the tolerance to less than 1%, thereby vastly improving both the overall security of the transmitted information as well as the quality of the image retrieval.

  20. Dependence of integrated acousto-optical devices with one and two modulated arms on the static phase difference.

    PubMed

    Fan, Guofang; Li, Yuan; Hu, Chunguang; Lei, Lihua; Zhao, Dong; Li, Hongyu; Zhen, Zhen

    2014-10-01

    In this paper, we develop an analytical model of an integrated acousto-optical (AO) device with arms modulated by a single surface acoustic wave beam. A comparison between one-arm and two-arm modulation is presented, which shows that two-arm modulation can significantly enhance modulation efficiency by an optimized design. A detailed analysis of the influence of static phase difference on the behavior of the AO devices has been provided, and some interesting results have been obtained. These will be helpful for an optimized design of AO devices for different functionalities.

  1. Improvements on the refresh rate and dynamical properties of a SLM by sequential readout using an acousto-optic modulator

    NASA Astrophysics Data System (ADS)

    Mestre, Michael; Viaris de Lesegno, Bruno; Farcy, René; Pruvost, Laurence; Bourderionnet, Jérôme; Delboulbé, Anne; Loiseaux, Brigitte; Dolfi, Daniel

    2006-08-01

    We demonstrate the use of an acousto-optic modulator to enhance the refresh rate and dynamic properties of a liquid-crystal spatial light modulator (SLM). The useful area of the SLM surface is split in several zones which are addressed separately, and read in a sequence by a steered laser beam. This configuration allows to increase the refresh rate by five orders of magnitude. Furthermore, improvements on the nature of the transition between different holograms are experimentally shown. The advantages of this technique are discussed in the particular context of cold atom manipulation with holographic optical tweezers.

  2. Optimization of the input losses in fiber-optic communications with an acousto-optic all-optical switch.

    PubMed

    Danilyan, A V; Shulgin, V A; Chernov, V E

    2006-06-20

    We study optical losses in the single-mode fiber system with an all-optical switch based on the anisotropic acousto-optic (AO) TeO(2) 2D deflector. It is shown, theoretically and experimentally, that the mismatch of the output-fiber mode profile and the switched optical beam shape depends significantly on the monochromaticity of the light beam and is determined by the frequency dispersion of the laser beam diffracted on a Bragg AO cell. A quantitative analysis of the dependence of the input optical losses on the spectral width of the light beam is presented.

  3. Simple tunable dye laser using a dielectric multilayer filter

    SciTech Connect

    Nomura, A.; Shimomura, Y.; Saito, Y.; Kano, T.

    1982-04-01

    We describe a nitrogen laser pumped dye laser tuned by a dielectric multilayer filter. The construction is simple and the adjustment of tuning is easy. It is found that the tuning is possible over a range of 10 nm from 445 to 455 nm in alcoholic solutions of coumarin 1, that the linewidth (0.8 nm) is independent of the filter tilt angle, and that the output intensity is remarkably flat over this tuning range.

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

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

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

  5. Theoretical study on the ultra-narrow bandwidth tunable atomic filter with electromagnetically induced transparency

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Li, Shu-qing; Feng, Zhong-ying; Liu, Xiao-fei; Gao, Jin-yue

    2016-12-01

    To obtain the weak signal light detection from the high background noise, we present a theoretical study on the ultra-narrow bandwidth tunable atomic filter with electromagnetically induced transparency. In a three-level Λ -type atomic system in the rubidium D1 line, the bandwidth of the EIT atomic filter is narrowed to ~6.5 \\text{MHz} . And the single peak transmission of the filter can be up to 86% . Moreover, the transmission wavelength can be tuned by changing the coupling light frequency. This theoretical scheme can also be applied to other alkali atomic systems.

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

    NASA Astrophysics Data System (ADS)

    Foukal, Peter

    1992-10-01

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

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

    NASA Technical Reports Server (NTRS)

    Foukal, Peter

    1992-01-01

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

  8. Wavelength tunable liquid crystal imaging filters for remote sensing from geosynchronous platforms. Final Report

    SciTech Connect

    Foukal, P.

    1992-10-01

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

  9. Global maxima for the acousto-optic effect in SrB4O7 crystals.

    PubMed

    Oleh, Buryy; Nazariy, Andrushchak; Andriy, Ratych; Natalia, Demyanyshyn; Bohdan, Mytsyk; Anatoliy, Andrushchak

    2017-03-01

    For the first time, the global maxima of the acousto-optic interaction are theoretically determined for biaxial SrB4O7 crystals by the extreme surfaces method. As it is shown, the highest value of the acousto-optic figure-of-merit M2 is equal to 6.3×10-16  s3/kg and achieved in the case of the isotropic diffraction of the electromagnetic wave propagating in the [010] direction on the fast quasi-transversal acoustic wave.

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

    PubMed

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

    2011-06-20

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

  11. Optofluidic tunable plasmonic filter based on liquid-crystal microcavity structures

    NASA Astrophysics Data System (ADS)

    Chen, Fang; Yao, Duanzheng

    2014-10-01

    A theoretical demonstration of Optofluidic tunable wavelength filter in the near-infrared regime has been presented. By incorporating nematic liquid crystal (LC) into the slot resonator, a nanoscale LC optical filter is proposed and numerically investigated. The finite difference time domain method is used to simulate the optical characteristics of the plasmonic nanostructure. Two approaches are considered to tune the filter's resonant wavelength, a fine tuning based on optofluidic control LC length and a coarse tuning based on LC birefringence. Both fine tuning and coarse tuning are successful for manipulating the filter's resonant wavelength. This plasmonic structure permits the high-precision control of transmit of the input surface plasmon polaritons. The filters may have important potential application in highly integrated optical circuits.

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

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  13. UV laser with an acousto-optic intra-cavity control for GaN-sapphire cut

    NASA Astrophysics Data System (ADS)

    Gradoboev, Yury G.; Kazaryan, Mishik A.; Mokrushin, Yury M.; Shakin, Oleg V.

    2012-09-01

    A copper vapor laser is proposed as the basic component of the installation for processing of sapphire substrates with a GaN-coating. Laser radiation is transformed to UV range by optical frequency doubling. Powerful UV lasers are prospective tools for crystal cutting, photolithography and recording of the fiber Bragg gratings. The proposed approach is more promising in comparison with the use of excimer radiation because of instabilities of excimer laser generation and low coherence of its radiation, which makes difficult precise focusing and using interference pattern of UV radiation for exposing materials. UV laser based on second harmonic radiation of copper vapors laser has been designed. The UV laser system of high operation stability has been developed with output power 1 W at wavelengths 255.5 nm, 271.1 nm, 289.1 nm and coherence length radiation about 4 cm. The original intra-cavity acousto-optic control of output radiation is developed. It is allows adjusting frequency and on-off time ratio of output laser pulses with high accuracy. The stable heat regime was achieved for an active element of copper vapor laser̤ The laser system allows to select an optimum mode of ultra-violet radiation exposition for production of different optical elements. Intra-cavity acousto-optic cell was used for controlling of single pulse amplitude and number of pulses without any power supply tuning providing the stable operation of the laser system.

  14. In-plane vibration characterization of microelectromechanical systems using acousto-optic modulated partially incoherent stroboscopic imaging

    NASA Astrophysics Data System (ADS)

    Wang, Dung-An; Sheu, Fang-Wen; Chiu, Yen-Sih

    2011-07-01

    A technique using acousto-optic modulated partially incoherent stroboscopic imaging for measurement of in-plane motion of microelectromechanical systems (MEMS) is presented. Vibration measurement is allowed by using flashes of the partially incoherent light source to freeze the positions of the microstructure at 12 equally spaced phases of the vibration period. The first-order diffracted beam taken out by an acousto-optic modulator (AOM) from the light beam of a laser is made partially incoherent by a rotating diffuser and then serves as the stroboscopic light source. Both the MEMS excitation signal and the flash control signal are provided by a dual-channel function generator. The main advantage of this measurement method is the absence of a stroboscopic generator and a high speed digital camera. Microscale prototypes are fabricated and tested. Quantitative estimates of the harmonic responses of the prototypes are obtained from the recorded images. The results agree with those obtained with a commercial MEMS motion analyzer TM with relative errors less than 2%.

  15. A novel acousto-optic modulation-deflection mechanism using refractive index grating as graded index beam router

    NASA Astrophysics Data System (ADS)

    Jangjoo, Alireza; Reza Baezzat, Mohammad; Razavizadeh, Ahmad

    2014-03-01

    A novel acousto-optic modulation mechanism will be addressed in this paper. Focused Gaussian beam passing through acousto-optic media experiences different refractive index regions arising from acoustic waves generated by ultrasonic source. In this way according to the snell's law of refraction the beam propagation path will be altered when these periodic traveling waves reach the incoming radiation where a typical p-n junction photodiode located inside the rising or falling lobe of the undiffracted Gaussian beam senses these small lateral deflections. Due to small variations of the refractive index the magnitude of deflection will be up to tens of micron outside the modulator. Hence, sharp intensity gradient is required for detecting such small beam movements by appropriate lens configuration to focus the Gaussian profile on the detector junction area. In the other words intensity profile of zero order beam oscillates proportional to the time dependent amplitude of the acoustic waves versus previous methods that intensity of diffracted beam changes with applied ultrasonic intensity. The extracted signal properties depend on the beam collimation, quality of beam profile and depth of focus inside the modulator. The first experimental approach was proceeded using a collimated 532 nm diode laser source (TEM00), distilled water as interaction media and 10 MHz transducer as ultrasonic generator where a cylindrical glass column with input-output flat windows was used for liquid support. The present method has advantages over common acoustooptical techniques as low cost, simplicity of operation, direct modulation of the signal and minimum alignment requirement.

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

    PubMed Central

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

    2016-01-01

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

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

    SciTech Connect

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

    2015-10-15

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

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

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

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

  19. Tunable band notch filters by manipulating couplings of split ring resonators.

    PubMed

    Sun, Haibin; Wen, Guangjun; Huang, Yongjun; Li, Jian; Zhu, Weiren; Si, Li-Ming

    2013-11-01

    The couplings between single/dual split ring resonators (SRRs) and their mirror images in a rectangular waveguide are systematically investigated through theoretical analysis and experimental measurements. Such couplings can be manipulated mechanically by rotating the SRRs along a dielectric rod and/or shifting the SRRs up/down along the sidewall of the rectangular waveguide, resulting in shifts of the resonant frequencies and modulations of the resonant magnitudes. These controllable properties of SRRs pave the routers toward designing tunable band notch filters. In particular, it is experimentally demonstrated that the designed filters possess 7.5% tuning range in the X-band.

  20. A liquid crystals modulated optical tunable filter based on Fano resonance of Au nanorod trimer

    NASA Astrophysics Data System (ADS)

    Xin, Huan Peng; Liu, Fei; Ren, Guang Jun; Zhao, Hong Liang; Yao, Jian Quan

    2017-04-01

    We theoretically studied the liquid crystals modulated optical tunable filter based on Fano resonance of Au nanorod trimer. Plasmonic nanorods can support Fano resonances, where the line shape characteristics are controlled by the geometry of nanorods. Here a polarization-dependent Au nanorod trimer was designed, where the three nanorods have the same geometric parameters and form a C-shape. When the plasmon modes of the longitudinal nanorod and the two transverse nanorods couple at resonance wavelength, a Fano resonance occurs. Due to liquid crystals can change the polarization direction of light, the transmission spectra of Au nanorod trimer can be switched on and off with different phases of liquid crystals when incident light passes through liquid crystals before reaching the Au nanorod trimer. Furthermore, filter optical characteristics are highly tunable by changing the thicknesses of Au nanorod trimer and its coating layer. Fano resonances show a large light extinction in periodic array of assembled nanorods, which can be used in optical tunable filter and optical switch.

  1. GaN-based metamaterial terahertz bandpass filter design: tunability and ultra-broad passband attainment.

    PubMed

    Khodaee, M; Banakermani, M; Baghban, H

    2015-10-10

    Engineering metamaterial-based devices such as terahertz bandpass filters (BPFs) play a definitive role in advancement of terahertz technology. In this article, we propose a design procedure to obtain a considerably broadband terahertz BPF at a normal incidence; it shows promising filtering characteristics, including a wide passband of ∼1.34  THz at a central frequency of 1.17 THz, a flat top in a broad band, and high transmission, compared to previous reports. Then, exploiting the voltage-dependent carrier density control in an AlGaN/GaN heterostructure with a Schottky gate configuration, we investigate the tuning of the transmission properties in a narrow-band terahertz filter. A combination of the ultra-wide, flat-top BPF in series with the tunable, narrow band filter designed in the current study offers the ability to tune the desired resonance frequency along with high out-of-band rejection and the suppression of unwanted resonances in a large spectral range. The proposed structure exhibits a frequency tunability of 103 GHz for a voltage change between -8 and 2 V, and a transmission amplitude change of ∼0.51. This scheme may open up a route for the improved design of terahertz filters and modulators.

  2. Self-tuning acousto-optic deflectors with acoustic line made of NaBi(MoO4)2 crystal

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

    The idea of acousto-optic self-tuning deflector, which automatically returns the position of the acoustic line, corresponding to the mode of Bragg diffraction feedback implementation is proposed. Features of sodium bismuthate's double molybdate grown by new technology - low gradient Czochralski process are illustrated.

  3. Lumped modeling with circuit elements for nonreciprocal magnetoelectric tunable band-pass filter

    NASA Astrophysics Data System (ADS)

    Li, Xiao-Hong; Zhou, Hao-Miao; Zhang, Qiu-shi; Hu, Wen-Wen

    2016-11-01

    This paper presents a lumped equivalent circuit model of the nonreciprocal magnetoelectric tunable microwave band-pass filter. The reciprocal coupled-line circuit is based on the converse magnetoelectric effect of magnetoelectric composites, includes the electrical tunable equivalent factor of the piezoelectric layer, and is established by the introduced lumped elements, such as radiation capacitance, radiation inductance, and coupling inductance, according to the transmission characteristics of the electromagnetic wave and magnetostatic wave in an inverted-L-shaped microstrip line and ferrite slab. The nonreciprocal transmission property of the filter is described by the introduced T-shaped circuit containing controlled sources. Finally, the lumped equivalent circuit of a nonreciprocal magnetoelectric tunable microwave band-pass filter is given and the lumped parameters are also expressed. When the deviation angles of the ferrite slab are respectively 0° and 45°, the corresponding magnetoelectric devices are respectively a reciprocal device and a nonreciprocal device. The curves of S parameter obtained by the lumped equivalent circuit model and electromagnetic simulation are in good agreement with the experimental results. When the deviation angle is between 0° and 45°, the maximum value of the S parameter predicted by the lumped equivalent circuit model is in good agreement with the experimental result. The comparison results of the paper show that the lumped equivalent circuit model is valid. Further, the effect of some key material parameters on the performance of devices is predicted by the lumped equivalent circuit model. The research can provide the theoretical basis for the design and application of nonreciprocal magnetoelectric tunable devices. Project supported by the National Natural Science Foundation of China (Grant Nos. 11172285, 11472259, and 11302217) and the Natural Science Foundation of Zhejiang Province, China (Grant No. LR13A020002).

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

    SciTech Connect

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

    1997-01-01

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

  5. Integrated acousto-optic polarization converter in a ZX-cut LiNbO(3) waveguide superlattice.

    PubMed

    Yudistira, D; Janner, D; Benchabane, S; Pruneri, V

    2009-10-15

    We report an integrated acousto-optic polarization converter exploiting a novel surface acoustic superlattice (S-ASL) transducer. The S-ASL transducer is made of a ZX-cut periodically poled lithium niobate (PPLN) crystal with uniform coplanar electrodes for surface acoustic wave (SAW) generation. For a PPLN period of 20 microm the SAW is excited at an rf of about 190 MHz, while the phase matching occurs at an optical wavelength of around 1456 nm. The measured mode conversion efficiency of 90% at an input rf power of 1 W and the 3 dB optical bandwidth of 2.5 nm confirm the confinement of the SAW between the electrode gap and the constructive interaction along the whole 10 mm electrode length.

  6. Chaos control and synchronization in Bragg acousto-optic bistable systems driven by a separate chaotic system.

    PubMed

    Wang, Rong; Gao, Jin-Yue

    2005-09-01

    In this paper we propose a new scheme to achieve chaos control and synchronization in Bragg acousto-optic bistable systems. In the scheme, we use the output of one system to drive two identical chaotic systems. Using the maximal conditional Lyapunov exponent (MCLE) as the criterion, we analyze the conditions for realizing chaos synchronization. Numerical calculation shows that the two identical systems in chaos with negative MCLEs and driven by a chaotic system can go into chaotic synchronization whether or not they were in chaos initially. The two systems can go into different periodic states from chaos following an inverse period-doubling bifurcation route as well when driven by a periodic system.

  7. A compact acousto-optic lens for 2D and 3D femtosecond based 2-photon microscopy

    PubMed Central

    Kirkby, Paul A.; Naga Srinivas, N.K.M.; Silver, R. Angus

    2010-01-01

    We describe a high speed 3D Acousto-Optic Lens Microscope (AOLM) for femtosecond 2-photon imaging. By optimizing the design of the 4 AO Deflectors (AODs) and by deriving new control algorithms, we have developed a compact spherical AOL with a low temporal dispersion that enables 2-photon imaging at 10-fold lower power than previously reported. We show that the AOLM can perform high speed 2D raster-scan imaging (>150 Hz) without scan rate dependent astigmatism. It can deflect and focus a laser beam in a 3D random access sequence at 30 kHz and has an extended focusing range (>137 μm; 40X 0.8NA objective). These features are likely to make the AOLM a useful tool for studying fast physiological processes distributed in 3D space PMID:20588506

  8. Femtosecond terahertz time-domain spectroscopy at 36 kHz scan rate using an acousto-optic delay

    NASA Astrophysics Data System (ADS)

    Urbanek, B.; Möller, M.; Eisele, M.; Baierl, S.; Kaplan, D.; Lange, C.; Huber, R.

    2016-03-01

    We present a rapid-scan, time-domain terahertz spectrometer employing femtosecond Er:fiber technology and an acousto-optic delay with attosecond precision, enabling scanning of terahertz transients over a 12.4-ps time window at a waveform refresh rate of 36 kHz, and a signal-to-noise ratio of 1.7 × 105 / √{ H z } . Our approach enables real-time monitoring of dynamic THz processes at unprecedented speeds, which we demonstrate through rapid 2D thickness mapping of a spinning teflon disc at a precision of 10 nm/ √{ H z } . The compact, all-optical design ensures alignment-free operation even in harsh environments.

  9. Ultrafast, large-field multiphoton microscopy based on an acousto-optic deflector and a spatial light modulator

    PubMed Central

    Shao, Yonghong; Qin, Wan; Liu, Honghai; Qu, Junle; Peng, Xiang; Niu, Hanben; Gao, Bruce Z.

    2013-01-01

    We present an ultrafast, large-field multiphoton excitation fluorescence microscope with high lateral and axial resolutions based on a two-dimensional (2-D) acousto-optical deflector (AOD) scanner and spatial light modulator (SLM). When a phase-only SLM is used to shape the near-infrared light from a mode-locked titanium:sapphire laser into a multifocus array including the 0-order beam, a 136 μm × 136 μm field of view is achieved with a 60× objective using a 2-D AOD scanner without any mechanical scan element. The two-photon fluorescence image of a neuronal network that was obtained using this system demonstrates that our microscopy permits observation of dynamic biological events in a large field with high-temporal and -spatial resolution. PMID:22743445

  10. Ultrafast, large-field multiphoton microscopy based on an acousto-optic deflector and a spatial light modulator.

    PubMed

    Shao, Yonghong; Qin, Wan; Liu, Honghai; Qu, Junle; Peng, Xiang; Niu, Hanben; Gao, Bruce Z

    2012-07-01

    We present an ultrafast, large-field multiphoton excitation fluorescence microscope with high lateral and axial resolutions based on a two-dimensional (2-D) acousto-optical deflector (AOD) scanner and spatial light modulator (SLM). When a phase-only SLM is used to shape the near-infrared light from a mode-locked titanium:sapphire laser into a multifocus array including the 0-order beam, a 136 μm × 136 μm field of view is achieved with a 60× objective using a 2-D AOD scanner without any mechanical scan element. The two-photon fluorescence image of a neuronal network that was obtained using this system demonstrates that our microscopy permits observation of dynamic biological events in a large field with high-temporal and -spatial resolution.

  11. Acousto-optical deflection-based whole channel scanning for microchip isoelectric focusing with laser-induced fluorescence detection.

    PubMed

    Sanders, J C; Huang, Z; Landers, J P

    2001-12-01

    This paper describes the development of a technique amenable to the separation of proteins on a microchip by isoelectric focusing (IEF) with entire channel scanning laser-induced fluorescence detection using acousto-optical deflection (AOD). The ability to use AOD to scan the portions of or the entire length of an IEF separation channel allows for high-speed analysis since the mobilization step is circumvented with this technique. Employing no moving parts eliminates mechanical noise and, not only is there no loss of resolution, AOD scanning can potentially increase resolution. The ability of AOD to provide ultra-fast scanning rates (kHz timescale) allows for real-time imaging of the focusing process. This is demonstrated with the separation of naturally fluorescent proteins using entire channel (total scanning range of 2.4 cm) AOD-mediated scanning laser-induced fluorescence detection.

  12. Development of a wavelength tunable filter using MEMS technology

    NASA Astrophysics Data System (ADS)

    Liu, Junting

    Microelectromechanical systems (MEMS) for optical applications have received intensive attention in recent years because of their potential applications in optical telecommunication. Traditional wavelength division multiplexing (WDM) offers high capacity but requires the fabrication of selective add-drop filters. MEMS technology offers an effective way to fabricate these components at low cost. This thesis presents the development of a device that tunes the Bragg wavelength by coupling into the evanescent field of the grating. A Bragg grating is a periodic perturbation of the refractive index along a fiber or a periodic perturbation of the structure of a planar waveguide. The Bragg wavelength can be tuned by changing the degree to which a dielectric slab couples into the evanescent field. The result is a change in the effective index of the grating, and thus a change in the wavelength that which it reflects. In this thesis Bragg gratings were successfully written into an optical fiber using phase mask technique. Mechanical polishing was used to side-polish the fiber and remove cladding to expose the core. Grating structures were also fabricated in planar waveguide using E-beam writing and dry etching. In order to achieve the smoothest possible morphology of the waveguide, plasma dry etching of transparent substrates was studied in great detail. It is found that the pre-etch cleaning procedure greatly influences the ability to obtain a smooth etched surface. Upper limits of evanescent field tuning were investigated by applying different index liquids such as D. I. water and index matching oils or by positioning different dielectric materials such as glass and silicon close to the grating. Planar waveguides were found to be more sensitive to effective index change. Two kinds of computer simulation were carried out to understand the mode profile and to estimate the value of effective index of planar waveguide under "dry" and "wet" conditions. The first one used an

  13. A continuously tunable microwave photonic notch filter with complex coefficient based on phase modulation

    NASA Astrophysics Data System (ADS)

    Xu, Dong; Cao, Ye; Tong, Zheng-rong; Yang, Jing-peng

    2017-01-01

    A continuously tunable microwave photonic notch filter with complex coefficient based on phase modulation is proposed and demonstrated. The complex coefficient is generated using a Fourier-domain optical processor (FD-OP) to control the amplitude and phase of the optical carrier and radio-frequency (RF) phase modulation sidebands. By controlling the FD-OP, the frequency response of the filter can be tuned in the full free spectral range ( FSR) without changing the shape and the FSR of the frequency response. The results show that the center frequency of the notch filter can be continuously tuned from 17.582 GHz to 29.311 GHz with FSR of 11.729 GHz. The shape of the frequency response keeps unchanged when the phase is tuned.

  14. Tunable Plasmonic Band-Pass Filter with Dual Side-Coupled Circular Ring Resonators

    PubMed Central

    Liu, Dongdong; Wang, Jicheng; Zhang, Feng; Pan, Yuewu; Lu, Jian; Ni, Xiaowu

    2017-01-01

    A wavelength band-pass filter with asymmetric dual circular ring resonators in a metal-insulator-metal (MIM) structure is proposed and numerically simulated. For the interaction of the local discrete state and the continuous spectrum caused by the side-coupled resonators and the baffle, respectively, the transmission spectrum exhibits a sharp and asymmetric profile. By adjusting the radius and material imbedded in one ring cavity, the off-to-on plasmon-induced absorption (PIA) optical response can be tunable achieved. In addition, the structure can be easily extended to other similar compact structures to realize the filtering task. Our structures have important potential applications for filters and sensors at visible and near-infrared regions. PMID:28335398

  15. New prototype of acousto-optical radio-wave spectrometer with parallel frequency processing for astrophysical applications

    NASA Astrophysics Data System (ADS)

    Shcherbakov, Alexandre S.; Chavez Dagostino, Miguel; Arellanes, Adan O.; Aguirre Lopez, Arturo

    2016-09-01

    We develop a multi-band spectrometer with a few spatially parallel optical arms for the combined processing of their data flow. Such multi-band capability has various applications in astrophysical scenarios at different scales: from objects in the distant universe to planetary atmospheres in the Solar system. Each optical arm exhibits original performances to provide parallel multi-band observations with different scales simultaneously. Similar possibility is based on designing each optical arm individually via exploiting different materials for acousto-optical cells operating within various regimes, frequency ranges and light wavelengths from independent light sources. Individual beam shapers provide both the needed incident light polarization and the required apodization to increase the dynamic range of a system. After parallel acousto-optical processing, data flows are united by the joint CCD matrix on the stage of the combined electronic data processing. At the moment, the prototype combines still three bands, i.e. includes three spatial optical arms. The first low-frequency arm operates at the central frequencies 60-80 MHz with frequency bandwidth 40 MHz. The second arm is oriented to middle-frequencies 350-500 MHz with frequency bandwidth 200-300 MHz. The third arm is intended for ultra-high-frequency radio-wave signals about 1.0-1.5 GHz with frequency bandwidth <300 MHz. To-day, this spectrometer has the following preliminary performances. The first arm exhibits frequency resolution 20 KHz; while the second and third arms give the resolution 150-200 KHz. The numbers of resolvable spots are 1500- 2000 depending on the regime of operation. The fourth optical arm at the frequency range 3.5 GHz is currently under construction.

  16. Frequency response of a TeO{sub 2} slow shear wave acousto-optic cell exposed to radiation

    SciTech Connect

    Erteza, I.A.; Craft, D.C.; Stalker, K.T.; Taylor, E.W.; Kelley, M.A.; Sanchez, A.D.; Chapman, S.P.; Craig, D.M.; Kinsley, E.

    1994-12-31

    Radiation testing of photonic components is not new, however component level testing to date has not completely addressed quantities which are important to system behavior. One characteristic that is of particular importance for optical processing systems is the frequency response. In this paper, the authors present the results of the analysis of data from an experiment designed to provide a preliminary understanding of the effects of radiation on the frequency response of acousto-optic devices. The goal is to present possible physical mechanisms responsible for the radiation effects and to discuss the effects on signal processing functionality. The experiment discussed in this paper was designed by Sandia National Laboratories (SNL) and performed by SNL and Phillips Laboratory (PL) personnel at White Sands Missile Range (WSMR). In the experiment, a TeO{sub 2} slow shear-wave acousto-optic cell was exposed to radiation from the WSMR linear accelerator. The TeO{sub 2} cell was placed in an experimental configuration which allowed swept frequency diffracted power measurements to be taken during radiation exposure and recovery. A series of exposures was performed. Each exposure consisted of between 1 to 800, 1 {mu}sec radiation pulses (yielding exposures of 2.25 kRad(Si) to 913 kRad(Si)), followed by recovery time. At low total and cumulative doses, the bandshape of the frequency response (i.e. diffracted power vs. frequency) remained almost identical during and after radiation. At the higher exposures, however, the amplitude and width of the frequency response changed as the radiation continued, but returned to the original shape slowly after the radiation stopped and recovery proceeded. It is interesting to note that the location of the Bragg degeneracy does not change significantly with radiation. In this paper, the authors discuss these effects, and they discuss the effect on the signal processing functionality.

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

    NASA Technical Reports Server (NTRS)

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

    1998-01-01

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

  18. 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

  19. 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.

  20. 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.

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

    PubMed Central

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

    2015-01-01

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

  2. Evaluation of hydrazine reduction by cellulose acetate filters using infrared tunable diode laser spectroscopy.

    PubMed

    Harward, Charles N; Parrish, Milton E; Plunkett, Susan E; Banyasz, Joseph L; Shafer, Kenneth H

    2002-11-15

    Cellulose acetate (CA) filters have been investigated to determine their hydrazine (N2H4) breakthrough characteristics using a system based on tunable diode laser absorption spectroscopy (TDIAS). The breakthrough mass loading sorption curves for hydrazine were dependent on both the flow rate and the concentration. In experiments using a 4.5 ppmv hydrazine standard, the amounts of hydrazine retained by the CA filter were 4.25 microg at a flow rate of 2.82 L/min and 65 microg at a flow rate of 0.28 L/min. These loadings are much greater than the 31.5 ng/cigarette of hydrazine reported in smoke for unfiltered cigarettes. Further, CA filters exposed to four and eight puffs of smoke actually made the filter more efficient in retaining hydrazine compared to CA filters that had not been exposed to smoke. Therefore, if hydrazine is present in smoke at the levels reported in unfiltered cigarettes, all of the hydrazine would be trapped by the CA filter, and would be unable to break through during smoking. A unique feature of this analytical method is that the instrument does not require calibration after molecular parameters have been determined, in this case from previously acquired quantitative hydrazine FT-IR reference spectra.

  3. Fast fiber-optic tunable filter based on axial compression on a fiber Bragg grating.

    PubMed

    Zu, Wen; Gu, Xijia

    2006-09-01

    We describe the design, fabrication, and performance of a fiber Bragg grating-based tunable optic filter. The filter, driven by two piezostacks, consists of a flexural hinge structure for displacement magnification and a fiber-ferrule assembly for axial compression of the fiber grating. Finite-element analysis was used to design the mechanical structure to achieve the required displacement magnification and the force for grating compression. A passive thermal compensation design was implemented to reduce thermal-induced wavelength drift. A feedback control system with a linear variable differential transformer was employed to control the displacement for accurate wavelength tuning and fine-tuning resolution. This tunable filter has achieved a closed-loop switching time of 17.3 ms, and a passive thermal compensation that reduced the thermal drift of the Bragg wavelength to 1.5 pm/C. The flexural-hinge structure that offers negligible backlash, noise-free motion, no need of lubricants, and no wear ensures its long-term reliability.

  4. Design and experimental research of a high-precision wavelength controller for tunable fiber Fabry-Perot filters

    NASA Astrophysics Data System (ADS)

    Qi, Hai-bing; Wei, Shu-hua; Wei, Chen

    2013-03-01

    A high-precision wavelength controller is presented in this paper. It is necessary to find out the difference between the central wavelength of a tunable fiber Fabry-Perot (FFP) filter and that of the input laser, while the wavelength controller operates at the states of wavelength-scanning and wavelength-locking modes. Firstly, a dynamic simulation model of tunable FFP filter is established, and the dynamic characteristic of tunable FFP filter modulated by an alternating current (AC) signal is simulated. Then the measuring time at wavelength-scanning mode compared with the theory time is discussed, and this time difference shows the difference between the central wavelength of a tunable FFP filter and that of the input laser. At last, the effects on wavelength-locking precision of time delays, including the time delay of opened-loop circuit, the time constant of the closed-loop circuit and the intrinsic hysteresis of piezoelectric (PZT) element, are analyzed. A wavelength controller of tunable FFP filter is designed and prepared. The experimental results at wavelength-locking mode show that a high locking precision is obtained.

  5. Fast spectral coherent anti-Stokes Raman scattering microscopy with high-speed tunable picosecond laser.

    PubMed

    Cahyadi, Harsono; Iwatsuka, Junichi; Minamikawa, Takeo; Niioka, Hirohiko; Araki, Tsutomu; Hashimoto, Mamoru

    2013-09-01

    We develop a coherent anti-Stokes Raman scattering (CARS) microscopy system equipped with a tunable picosecond laser for high-speed wavelength scanning. An acousto-optic tunable filter (AOTF) is integrated in the laser cavity to enable wavelength scanning by varying the radio frequency waves applied to the AOTF crystal. An end mirror attached on a piezoelectric actuator and a pair of parallel plates driven by galvanometer motors are also introduced into the cavity to compensate for changes in the cavity length during wavelength scanning to allow synchronization with another picosecond laser. We demonstrate fast spectral imaging of 3T3-L1 adipocytes every 5  cm-1 in the Raman spectral region around 2850  cm-1 with an image acquisition time of 120 ms. We also demonstrate fast switching of Raman shifts between 2100 and 2850  cm-1, corresponding to CD2 symmetric stretching and CH2 symmetric stretching vibrations, respectively. The fast-switching CARS images reveal different locations of recrystallized deuterated and nondeuterated stearic acid.

  6. Portable AOTF Raman integrated Tunable Sensor (RAMiTS) for chemical and biosensing

    NASA Astrophysics Data System (ADS)

    Chen, K.; Martin, M. E.; Vo-Dinh, Tuan

    2005-11-01

    This paper describes the development of a compact, self-contained, and portable Raman Integrated Tunable Sensor (RAMiTS) for chemical and biosensing. The RAMiTS consists of a frequency-stabilized diode laser for excitation, an acousto-optic tunable filter (AOTF) for wavelength discrimination, and an avalanche photodiode (APD) for detection. It can provide direct identification and quantitative analysis of chemical and biological samples in a few seconds under field conditions. Instrument control and data acquisition was coordinated by software developed in house using the C language. Evaluation of this instrument was performed by analyzing several model compounds and the high spectral resolution of this instrument was demonstrated by the discrimination of several structurally similar molecules (benzene, toluene and naphthalene) as well as m-, o-, p- isomers of xylene. The potential applications of the RAMiTS coupled with the surface-enhanced Raman scattering (SERS) for the detection of chemical and biological warfare agents will also be discussed in this paper.

  7. Tunable dual-wavelength filter and its group delay dispersion in domain-engineered lithium niobate

    NASA Astrophysics Data System (ADS)

    Shao, Guang-hao; Song, Jing; Ruan, Ya-ping; Cui, Guo-xin; Lu, Yan-qing

    2016-12-01

    A tunable dual-wavelength filter is experimentally demonstrated in domain-engineered lithium niobate. Application of an electric field on the y-surfaces of the sample results in the optical axes rotating clockwise and anticlockwise, which makes selective polarization rotation. The quasi phase-matching wavelengths could be adjusted through suitable domain design. A unique dual valley spectrum is obtained in a periodically poled lithium niobate structure with a central defect if the sample is placed between two parallel polarizers. The expected bandwidth could be varied from ˜1 nm to ˜40 nm. Moreover, both the spectral response and group delay dispersion could be engineered.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

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

    PubMed

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

    2016-02-01

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

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

    NASA Astrophysics Data System (ADS)

    Li, Shenping; Chan, K. T.

    1999-07-01

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

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

    PubMed

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

    2015-10-10

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

  13. Tunable band-stop plasmonic waveguide filter with symmetrical multiple-teeth-shaped structure.

    PubMed

    Wang, Hongqing; Yang, Junbo; Zhang, Jingjing; Huang, Jie; Wu, Wenjun; Chen, Dingbo; Xiao, Gongli

    2016-03-15

    A nanometeric plasmonic filter with a symmetrical multiple-teeth-shaped structure is investigated theoretically and numerically. A tunable wide bandgap is achievable by adjusting the depth and number of teeth. This phenomenon can be attributed to the interference superposition of the reflected and transmitted waves from each tooth. Moreover, the effects of varying the number of identical teeth are also discussed. It is found that the bandgap width increases continuously with the increasing number of teeth. The finite difference time domain method is used to simulate and compute the coupling of surface plasmon polariton waves with different structures in this Letter. The plasmonic waveguide filter that we propose here may have meaningful applications in ultra-fine spectrum analysis and high-density nanoplasmonic integration circuits.

  14. Investigation of utilizing a VCSEL diode to work as a tunable optical bandpass filter

    NASA Astrophysics Data System (ADS)

    Chang, Ching-Hung; Huang, Yi-Syuan; Li, Chung-Yi

    2017-04-01

    Tunable optical band-pass filter (TOBPF) composed of a vertical-cavity surface-emitting laser (VCSEL) is proposed for multi-wavelength optical fiber transport systems. Experimental results prove that through properly adjusting VCSEL driving current, one of multiple injected lightwaves can properly flow through the proposed optical filter and others will be attenuated roughly 12 dB. Furthermore, by changing the VCSEL driving current, the pass-band window of the VCSEL-based TOBPF can be shifted to align with different designated injected lightwave and to block the others. By employing the TOBPF in multi-wavelength optical fiber transport systems, proper eye diagrams are experimentally observed for each dedicated optical signal. The proposed scheme is shown to be a practical and flexible component for multi-wavelength optical fiber transport systems.

  15. High-speed wavelength tunable DPSK demodulation using a phase modulator based loop mirror filter.

    PubMed

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

    2014-06-15

    A high-speed wavelength tunable differential phase-shift-keying (DPSK) signal demodulator is presented using a phase modulator (PM) based fiber loop mirror filter. By controlling the birefringence of the PM inside the loop through electro-optic effect, wavelength tuning speed of tens of GHz and tuning range of over two free spectral ranges are achieved. Stable filter spectra with extinction ratio over 30 dB are obtained through the tuning process. By combining the birefringence of polarization maintaining fiber and PM, error-free demodulation performance is experimentally achieved throughout the wavelength tuning range for DPSK signals with flexible bit-rate range from 2.5 to 10  Gb/s. This design significantly improves the wavelength tuning speed and is potentially valuable for high-speed switching and tuning applications.

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

    SciTech Connect

    Liu, Yang; Yi, Lin

    2014-12-14

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

  17. Acousto-optic Bragg diffraction in a LiNbO3 channel-planar composite waveguide with application to optical computing

    NASA Astrophysics Data System (ADS)

    Tsai, C. S.; Zang, D. Y.; Le, P.

    1985-09-01

    Successful experimentation on acousto-optic Bragg diffraction in a LiNbO3 composite waveguide that consists of an array of parallel but uncoupled channel waveguides directly extended to a single-mode planar waveguide and a titanium-indiffused proton-exchanged (TIPE) microlens array is reported for the first time. A channel-waveguide array, a planar waveguide, a linear TIPE microlens array, a 500-MHz surface acoustic wave transducer, and an integrating lens have all been integrated in a substrate size of 0.2 x 1.0 x 2.0 cm to form an integrated acousto-optic Bragg modulator that should find a variety of applications in optical computing, signal processing, and communications. The resulting modulator module has been utilized to perform matrix-vector multiplication.

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

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

    SciTech Connect

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

    2013-10-01

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

  20. An experimental distribution of analog and digital information in a hybrid wireless visible light communication system based on acousto-optic modulation and sinusoidal gratings

    NASA Astrophysics Data System (ADS)

    Gómez Colín, R.; García Juárez, A.; Zaldívar Huerta, I. E.; Marquina, A. Vera; García Delgado, L. A.; Leal Cruz, A. L.; Gómez Fuentes, R.

    2016-03-01

    In this paper we propose a photonic architecture as an alternative tool to distribute point to multipoint analog and digital information over a hybrid wireless visible optical communication system. The experimental set-up is composed of a red laser pointer, an acousto-optic modulator, a sinusoidal grating and a photo-detector array. By using a simple and variable interferometric system, diffraction gratings with different spatial frequencies are generated and recorded on a photoemulsion which is composed of vanilla with dichromate gelatin. Analog video and digital information are first transmitted and recovered over a wireless communication system using a microwave carrier at 4.52 GHz which is generated by distributed feedback lasers operating in the low laser threshold current region. Separately, the recovered video information and digital data are combined with a radio frequency signal of 80 MHz, obtaining a subcarrier of information that is imposed on the optical carrier of the pointer laser using an acousto-optic modulator which is operated with an angle of incident light that satisfies the Bragg condition. The modulated optical carrier is sent to a sinusoidal grating, the diffraction pattern is photo-detected using an array of PIN photo-detectors. The use of sinusoidal gratings with acousto-optic modulators allows that number of channels to be increased when both components are placed in cascade.

  1. Optically Tunable Gratings for Optical Interconnects

    DTIC Science & Technology

    1989-10-30

    OPTICALLY TUNABLE GRATINGS FOR OPTICAL INTERCONNECTS Final Report SELECTED JAN 2 31990 D ~ Submitted...such as acousto - optic or electro- optic deflectors . Using the strengths of our research program, we investigated optically tuneable gratings in...are those ~!,f~~ a~Sh~;~~L~~ d ~~9~H ~~t.:~~!-r~~~’~IU! 2 ~’h!~ ~H~~!~g:rtment of the Army position, 17. COSATI CODES 1 I. SUBJECT TERMS (Continut on

  2. Acousto-optic multiphoton laser scanning microscopy and multiphoton photon counting spectroscopy: Applications and implications for optical neurobiology

    NASA Astrophysics Data System (ADS)

    Iyer, Vijay

    Multiphoton excitation of molecular probes has become an important tool in experimental neurobiology owing to the intrinsic optical sectioning and low light scattering it affords. Using molecular functional indicators, multiphoton excitation allows physiological signals within single neurons to be observed from within living brain tissue. Ideally, it would be possible to record from multiple sites located throughout the elaborately branching dendritic arbors, in order to study the correlations of structure and function both within and across experiments. However, existing multiphoton microscope systems based on scanning mirrors do not allow optical recordings to be obtained from more than a handful of sites simultaneously at the high rates required to capture the fast physiological signals of interest (>100Hz for Ca2+ signals, >1kHz for membrane potential transients). In order to overcome this limitation, two-dimensional acousto-optic deflection was employed, to allow an ultrafast laser beam suited for multiphoton excitation to be rapidly repositioned with low latency (˜15mus). This supports a random-access scanning mode in which the beam can repeatedly visit a succession of user-selected sites of interest within the microscope's field-of-view at high rates, with minimal sacrifice of pixel dwell time. This technique of acousto-optic multiphoton laser scanning microscope (AO-MPLSM) was demonstrated to allow the spatial profile of signals arising in response to physiological stimulation to be rapidly mapped. Means to compensate or avoid problems of dispersion which have hampered AO-MPLSM in the past are presented, with the latter being implemented. Separately, the combination of photon counting detection with multiphoton excitation, termed generally multiphoton photon counting spectroscopy (MP-PCS), was also considered, with particular emphasis on the technique of fluorescence correlation spectroscopy (FCS). MP-PCS was shown to allow information about molecular

  3. Submersible UV-B spectroradiometer using an acouto-optic tunable fiber

    NASA Astrophysics Data System (ADS)

    Egorov, V. G.; Nalivaiko, S. E.; Pavlenko, V. S.; Rzshevsky, O. S.; Gordon, E. B.; Cooper, L. W.; Grebmeier, J. M.; Shugart, Lee R.

    1997-02-01

    Measurements of solar irradiance in the UV-B region are complicated by large variance in radiation fluxes over it. Normally, measurement requires use of double monochromators with high spectral contrast. We have successfully tested a narrow bandwidth acousto-optic tunable filter (AOTF) with low spectral contrast. The conditions for deployment were use of (i) a double-beam scheme with simultaneous recording of illumination in measuring and reference channels; and (ii) the intrinsic property of the AOTF to be a neutral filter outside of its passband. To apply the necessary contrast the background intensity determined in the reference channel was subtracted from intensity in the measuring channel. Two identical solar-blind photomultipliers in photon-counting regime were used. The integral solar intensity was averaged over the whole period of spectral record in order to shorten the period of time required for measurement at each wavelength. Formulae determining the spectroradiometer sensitivity and resolution, as well as comparison with US commercial instrument are presented. The testing was undertaken during US-Russian work at Kasitsna Bay, Alaska, in 1995, where additional genetic and cytological studies of the UV-B radiation impact on marine organisms were made.

  4. Q-switching an all-fiber laser using acousto-optic null coupler

    NASA Astrophysics Data System (ADS)

    Berg, Yuval; Goldring, Sharone; Pearl, Shaul; Arie, Ady

    2013-05-01

    A new method for Q-switching an all-fiber laser is presented. It is based on induced acoustic long period grating operating on a null coupler, which acts as acoustically controlled tunable output coupler. Q-switching is achieved by switching on and off the acoustic wave in a burst mode, thereby generating laser pulses that are ~400 times shorter than the acoustically controlled coupler's rise time. Output pulse energy of 22 μJ and temporal width of ~100 ns were measured at a wavelength of 1.54 μm.

  5. All-fiber widely tunable mode-locked thulium-doped laser using a curvature multimode interference filter

    NASA Astrophysics Data System (ADS)

    Li, N.; Liu, M. Y.; Gao, X. J.; Zhang, L.; Jia, Z. X.; Feng, Y.; Ohishi, Y.; Qin, G. S.; Qin, W. P.

    2016-07-01

    We demonstrated a widely tunable mode-locked thulium doped fiber laser (TDFL) by using a homemade multimode interference filter (MMIF). The MMIF had a structure of single mode fiber (SMF)—multimode fiber (MMF)—SMF and three main transmission peaks at 1901.2, 1957.2 and 2043.2 nm. By mechanically bending the MMIF, the three main transmission peaks were tuned in the range of 1860-2024 nm due to multimode interference effect. By inserting the MMIF into a passively mode-locked TDFL cavity pumped by a 1570 nm fiber laser, a tunable mode-locked TDFL with a tuning range of 1919.6-2014.9 nm was achieved by adjusting the MMIF. To the best of our knowledge, such a tunable range is the largest among all-fiber tunable mode-locked TDFLs.

  6. 3D-NTT: A New Instrument for the NTT Based on Versatile Tunable Filter Technology

    NASA Astrophysics Data System (ADS)

    Marcelin, M.

    The 3D-NTT will be a visitor instrument for the NTT, built by GEPI (Paris) and LAM (Marseille) with the collaboration of LAE (Montréal, Canada) and AAO (Australia). It is a spectro-imager offering two modes: a low resolution mode (100-5000) with a Tunable Filter, and a high resolution mode (5000 - 40 000) with a standard scanning Fabry-Perot. A large variety of programmes may be led with such an instrument as has been shown recently (1997-2003) with the Taurus Tunable Filter on the AAT and WHT. In the frame of a large scientific coollaboration, gathering European teams as well as collaborators from other countries, we propose a Large Programme (IOGA) dedicated to the study of ionized gas in galaxies, at low and high z, to be undertaken with the 3D-NTT. Nearby IR galaxies (IRGs) are the key to understanding the formation and evolution of galaxies, as they are believed to be the local counter-part of the numerous luminous starburst galaxies at high z. To understand the nature, origin and evolution of IRGs, we propose to map the star formation and kinematics in 500 galaxies and obtain dust extinction, metal abundances and electron density maps in 50 of them for obtaining a reference sample with high spectral and spatial resolution (sub-kpc) to be compared with distant objects being observed on the VLT (GIRAFFE, SINFONI). We will take advantage of both modes proposed by the instrument: high resolution mode with scanning Fabry Perot (FOV 5.5' or 11'), and low resolution mode with Tunable Filter and larger field (FOV 20'). This mode will be used at high z to look for star forming galaxies around quasars with a range of intrinsic UV luminosity. Star forming galaxies exist in significant numbers around low power quasars and we want to check if this remains true around more distant and luminous quasars. This may be the first evidence that powerful UV fields can suppress or delay widespread star formation in galaxies and, as such, may provide important constraints on

  7. Tunable PIE and synchronized gating detections by FastFLIM for quantitative microscopy measurements of fast dynamics of single molecules

    NASA Astrophysics Data System (ADS)

    Sun, Yuansheng; Coskun, Ulas; Ferreon, Allan Chris; Barbieri, Beniamino; Liao, Shih-Chu Jeff

    2016-03-01

    The crosstalk between two fluorescent species causes problems in fluorescence microscopy imaging, especially for quantitative measurements such as co-localization, Förster resonance energy transfer (FRET), fluorescence cross correlation spectroscopy (FCCS). In laser scanning confocal microscopy, the lasers can be switched on and off by acousto-optic tunable filters (AOTF) in the microsecond scale for alternative line scanning in order to avoid the crosstalk while minimizing the time delay between two lasers on the same pixel location. In contrast, the pulsed interleaved excitation (PIE) technique synchronizes two pulsed lasers of different wavelengths in the nanosecond scale to enable measuring superfast dynamics of two fluorescent species simultaneously and yet quantitatively without the crosstalk contamination. This feature is critical for many cell biology applications, e.g. accurate determination of stoichiometry in FRET measurements for studying protein-protein interactions or cell signal events, detection of weaker bindings in FCCS by eliminating the false cross correlation due to the crosstalk. The PIE has been used with the time correlated single photon counting (TCSPC) electronics. Here, we describe a novel PIE development using the digital frequency domain (DFD) technique -- FastFLIM, which provides tunable PIE setups and synchronized gating detections, tailored and optimized to specific applications. A few PIE setups by FastFLIM and measurement examples are described. Combined with the sensitivity of Alba and Q2 systems, the PIE allowed us to quantitatively measure the fast dynamics of single molecules.

  8. Modeling-based design and assessment of an acousto-optic guided high-intensity focused ultrasound system

    NASA Astrophysics Data System (ADS)

    Adams, Matthew T.; Cleveland, Robin O.; Roy, Ronald A.

    2017-01-01

    Real-time acousto-optic (AO) sensing has been shown to noninvasively detect changes in ex vivo tissue optical properties during high-intensity focused ultrasound (HIFU) exposures. The technique is particularly appropriate for monitoring noncavitating lesions that offer minimal acoustic contrast. A numerical model is presented for an AO-guided HIFU system with an illumination wavelength of 1064 nm and an acoustic frequency of 1.1 MHz. To confirm the model's accuracy, it is compared to previously published experimental data gathered during AO-guided HIFU in chicken breast. The model is used to determine an optimal design for an AO-guided HIFU system, to assess its robustness, and to predict its efficacy for the ablation of large volumes. It was found that a through transmission geometry results in the best performance, and an optical wavelength around 800 nm was optimal as it provided sufficient contrast with low absorption. Finally, it was shown that the strategy employed while treating large volumes with AO guidance has a major impact on the resulting necrotic volume and symmetry.

  9. Application of the acousto-optic effect to pressure measurements in ultrasound fields in water using a laser vibrometer

    NASA Astrophysics Data System (ADS)

    Buick, J. M.; Cosgrove, J. A.; Douissard, P.-A.; Greated, C. A.; Gilabert, B.

    2004-10-01

    A non-intrusive measuring technique, applied to sensing and measuring acoustic waves at ultrasonic frequencies is considered. The method is optically based and so does not interfere with the ultrasound field. The measurement procedure relies on the acousto-optic effect, that is the change in refractive index which occurs with changing pressure in the ultrasound field. This change in refractive index is detected through the change in the path length of a laser beam propagating through the region of interest. Typically these changes are small corresponding to a physical change of the order of 10-6 m. Fourier analysis is used to separate the component of the signal corresponding to the pressure variation from background noise and vibrations which can be dominant. Application of the technique is illustrated for an underwater ultrasound transducer. Measurements are made using the optical technique and compared to measurements taken with a hydrophone. The effectiveness of the optical measuring technique is discussed. It is shown that the laser vibrometer produces a good estimation of the mean beam pressure provided an estimation of the beam width is available, a restriction which is often satisfied; and the acoustic field can be assumed to be approximately constant across the beam.

  10. Research Cooperation between Catholic Universityof Leuven Campus Kortrijk and University of Gdansk in Acousto-optics - A Historical Recollection1

    NASA Astrophysics Data System (ADS)

    Śliwiński, A.

    A short review of results achieved during many years of cooperation between the Belgian group of KULAK and the Polish group of Gdansk University (UG) is presented as a tribute to Oswald Leroy for his significant contribution. The scientific research in examination of ultrasonic light interaction phenomena was the area of this fruitful joint collaboration since 1971. Oswald Leroy's crucial role in the cooperation is emphasized and some historical events are recalled. His original theoretical papers predicted new theoretical phenomena which were successfully experimentally verified in the A. O. laboratory at the University of Gdansk. Later on, they have become inspiration for further fundamental search in acousto-optics. Members of Gdansk AO group many times visited Kortrijk to work together on ULD phenomena or attending seminars and symposia organized in Belgium and the Belgian group took part in the international Spring Schools and Applications systematically organized by Gdansk University as the triennial meetings since 1980. Leroy's contribution to the mutual co-operation has been recognized as so important and significant that in 1991 he was honored with the Doctorate Honoris Causa of the University of Gdansk.

  11. Real-Time Display Of 3-D Computed Holograms By Scanning The Image Of An Acousto-Optic Modulator

    NASA Astrophysics Data System (ADS)

    Kollin, Joel S.; Benton, Stephen A.; Jepsen, Mary Lou

    1989-10-01

    The invention of holography has sparked hopes for a three-dimensional electronic imaging systems analogous to television. Unfortunately, the extraordinary spatial detail of ordinary holographic recordings requires unattainable bandwidth and display resolution for three-dimensional moving imagery, effectively preventing their commercial development. However, the essential bandwidth of holographic images can be reduced enough to permit their transmission through fiber optic or coaxial cable, and the required resolution or space-bandwidth product of the display can be obtained by raster scanning the image of a commercially available acousto-optic modulator. No film recording or other photographic intermediate step is necessary as the projected modulator image is viewed directly. The design and construction of a working demonstration of the principles involved is also presented along with a discussion of engineering considerations in the system design. Finally, the theoretical and practical limitations of the system are addressed in the context of extending the system to real-time transmission of moving holograms synthesized from views of real and computer-generated three-dimensional scenes.

  12. Measured optical performance of three Fabry-Perot interferometers for use in a tunable ultraviolet filter

    NASA Technical Reports Server (NTRS)

    Korendyke, Clarence M.; Socker, Dennis G.

    1993-01-01

    A narrowband ultraviolet (UV) filter would allow the first monochromatic two-dimensional images of astrophysical plasmas to be obtained in UV emission lines. The high etendue and spectral resolving power of the Fabry-Perot (FP) interferometer make it an excellent candidate for use in a tunable UV filter, provided that adequate optical performance can be obtained. Laboratory measurements of three UV FP interferometers with progressively greater dielectric mirror reflectances are described. The measurements demonstrate the adequate reflectivity, absorption, and small-scale smoothness of currently available coatings and substrates for UV interferometry. The measurements are conducted at 228.8 nm utilizing a cadmium hollow cathode light source. The best performing interferometer has a finesse of 41 and maximum transmittance of 0.38 over a coating-performance-dominated 3-mm-diam subaperture and a finesse of 26 and maximum transmittance of 0.32 over a parabolic-defect-dominated 30-mm-diam aperture. This interferometer is well suited for use in a UV filter system.

  13. Bandwidth tunable guided-mode resonance filter using contact coupled gratings at oblique incidence

    NASA Astrophysics Data System (ADS)

    Sang, Tian; Wang, Yueke; Li, Junlang; Zhou, Jianyu; Jiang, Wenwen; Wang, Jicheng; Chen, Guoqing

    2017-01-01

    A novel bandwidth tunable guided-mode resonance filter (GMRF) is proposed based on the contact coupled gratings (CCGs) with the absentee layers at oblique incidence. The design principle of the CCGs with double absentee layers is presented. The lateral shift of the CCGs changes the magnetic field distributions of the waveguide mode in the grating cavity and the surface-confined mode at the cover/grating interface thus facilitates the dynamic control of both the spectral and angular bandwidth of the GMRF. The resonance locations are almost immune to the variation of the lateral shift of the CCGs. The sideband level of the GMRF is almost unaffected by the lateral shift due to the Brewster AR effect. The resonance peak red-shifts quasi-linearly as the incident angle is increased, and the resonance wavelength can be selected by merely tuning the incident angle. The tunable ranges of both the spectral and angular bandwidth can be significantly enhanced by increasing the refractive-index contrast. Low-sideband reflection with controllable bandwidth at 650 nm is designed to demonstrate this concept.

  14. Multispectral integral imaging acquisition and processing using a monochrome camera and a liquid crystal tunable filter.

    PubMed

    Latorre-Carmona, Pedro; Sánchez-Ortiga, Emilio; Xiao, Xiao; Pla, Filiberto; Martínez-Corral, Manuel; Navarro, Héctor; Saavedra, Genaro; Javidi, Bahram

    2012-11-05

    This paper presents an acquisition system and a procedure to capture 3D scenes in different spectral bands. The acquisition system is formed by a monochrome camera, and a Liquid Crystal Tunable Filter (LCTF) that allows to acquire images at different spectral bands in the [480, 680]nm wavelength interval. The Synthetic Aperture Integral Imaging acquisition technique is used to obtain the elemental images for each wavelength. These elemental images are used to computationally obtain the reconstruction planes of the 3D scene at different depth planes. The 3D profile of the acquired scene is also obtained using a minimization of the variance of the contribution of the elemental images at each image pixel. Experimental results show the viability to recover the 3D multispectral information of the scene. Integration of 3D and multispectral information could have important benefits in different areas, including skin cancer detection, remote sensing and pattern recognition, among others.

  15. Tunable Solid-Etalon Filter for the ICESat/GLAS 532 nm Channel Lidar Receiver

    NASA Technical Reports Server (NTRS)

    Krainak, Michael A.; Stephen, Mark A.; Martino, Anthony J.; Lunt, David L.

    2003-01-01

    The Geoscience Laser Altimeter System (GLAS) was launched into Earth orbit on board the Ice, Cloud and land Elevation Satellite (ICESat) on January 12, 2003. GLAS is a laser altimeter designed to measure ice-sheet topography and associated temporal changes, as well as cloud and atmospheric properties. Each (of the three identical) GLAS lasers is a diode pumped, Q-switched Nd:YAG laser with energy levels of 75 mJ (1064 nm) and 35 mJ (532 nm). The infrared pulse is used for both surface altimetry and atmospheric measurements while the green pulse is used primarily for atmospheric measurements. The receiver uses a 1 meter diameter telescope. We report on the tunable solid-etalon filter used in the ICESat/GLAS 532 nm channel lidar receiver.

  16. A thermally tunable terahertz bandpass filter with insulator-metal phase transition of VO2 thin film

    NASA Astrophysics Data System (ADS)

    Li, Wei; Chang, Sheng-jiang; Wang, Xiang-hui; Lin, Lie; Bai, Jin-jun

    2014-05-01

    A terahertz bandpass filter with the sandwich structure consisting of thermally tunable vanadium dioxide (VO2) thin film, silica substrate and subwavelength rectangular Cu hole arrays is designed and theoretically analyzed. The results show that the transmittance of the filter can be actively tuned by controlling the temperature of VO2, the narrow band terahertz (THz) waves with the transmittance from 85.2% to 10.5% can be well selected at the frequency of 1.25 THz when the temperature changes from 50 °C to 80 °C, and the maximum modulation depth of this terahertz bandpass filter can achieve 74.7%.

  17. Thermo-mechanically tunable Bragg grating filters on silicon-on-insulator rib waveguide bridges

    NASA Astrophysics Data System (ADS)

    Raum, Christopher R.

    This thesis explores the integration of an optical device within a micromechanical structure to enhance its performance and enable behaviour it would otherwise be incapable of. Thermo-mechanically tunable Bragg grating filters on silicon-on-insulator rib waveguide bridges have been designed, fabricated and characterised to demonstrate what happens when an optical device, and the actuator used to tune its optical response, are physically the same structure. The process flow developed to fabricate the device was a five mask process that included a bridge waveguide, integrated filter, and integrated heater. A surface micromachining technique was developed to release up to 4000 mum long, 5 mum thick waveguide bridges. The device has three distinct operating regimes: pre-buckle, buckle, and post-buckle. The pre-buckle experimental thermal sensitivity of the filter was 76 pm/°C and the theoretical sensitivity was 83 pm/°C. During the transient buckle regime, the Bragg filter wavelength was measured to shift 0.95 nm, and theorised to shift 0.55 nm. The post-buckle experimental thermal sensitivity of the filter was 88 pm/°C and the theoretical sensitivity was 99 pm/°C. The rib waveguide bridge was observed to possess a meta-stable regime between the pre- and post-buckle regimes. Before the critical buckle temperature could be attained, the bridge deflected 0.5 mum out-of-plane and remained static over a range of 7.5 °C, whereupon it deflected to its full 15.1 mum buckling mode height. This metastable deflection caused a Bragg wavelength shift of 0.39 nm. The thermal sensitivity of the Bragg filter wavelength in this meta-stable regime was 62 pm/°C. Rectangular cross-section beams did not produce this behaviour. Mechano-optical bi-stability was also observed. In this bi-stable regime there would be two possible Bragg wavelengths for a given temperature, depending on whether the device was in a forward or return path. The bi-stable regime occurred over a span of 15

  18. 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.

  19. Tunable microwave bandpass filter integrated power divider based on the high anisotropy electro-optic nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Liu, Yupeng; Liu, Yang; Li, Haiyan; Jiang, Di; Cao, Weiping; Chen, Hui; Xia, Lei; Xu, Ruimin

    2016-07-01

    A novel, compact microwave tunable bandpass filter integrated power divider, based on the high anisotropy electro-optic nematic liquid crystal, is proposed in this letter. Liquid crystal, as the electro-optic material, is placed between top inverted microstrip line and the metal plate. The proposed structure can realize continuous tunable bandpass response and miniaturization. The proposed design concept is validated by the good performance of simulation results and experimental results. The electro-optic material has shown great potential for microwave application.

  20. 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

  1. Rapid spontaneous Raman light sheet microscopy using cw-lasers and tunable filters.

    PubMed

    Rocha-Mendoza, Israel; Licea-Rodriguez, Jacob; Marro, Mónica; Olarte, Omar E; Plata-Sanchez, Marcos; Loza-Alvarez, Pablo

    2015-09-01

    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.

  2. Discretely tunable Tm-doped fiber-based MOPA using FBG arrays as spectral filters

    NASA Astrophysics Data System (ADS)

    Tiess, T.; Junaid, S.; Becker, M.; Rothhardt, M.; Bartelt, H.; Jäger, M.

    2016-03-01

    Over the past years, Thulium (Tm) -doped fiber lasers in the 2μm region have gained a lot of interest due to many potential applications in materials processing and biophotonics. Based on the broad gain regions spanning from 1800nm to 2100nm, they offer the perfect basis to implement broadly tunable and user-friendly light sources like they are increasingly demanded in spectroscopic applications. Recently, a novel tuning mechanism based on a fiber Bragg grating (FBG) array as versatile spectral filter has been reported. This concept combines unique spectral freedom for customized tuning ranges and ultrabroad bandwidths with a fiber-integrated setup in order to maintain the advantages of the waveguide geometry. In this work, we demonstrate such a dispersion tuned and pulsed fiber laser in the Tm domain around 1950nm using a modulator and a discrete FBG array to control the emission wavelength. In order to comply with the demands of potential applications in biophotonics, for the first time, this tuning concept is realized in a polarization maintaining (PM) configuration ensuring linearly polarized output. While a simple FBG array is employed containing five gratings inscribed in PM fiber, we also outline the prospect to implement FBGs fabricated in a standard single mode fiber. The emission characteristics of the system are investigated showing pulse durations down to 11ns and a good spectral signal contrast. In order to highlight the prospect for tunable high-power operation, we have also implemented an amplification stage scaling the average power to more than 25W.

  3. The simulation and improved design of tunable channel drop filter using hexagonal photonic crystal ring resonator

    SciTech Connect

    Chhipa, Mayur Kumar

    2014-10-15

    In this paper, we have proposed a new design of tunable two dimensional (2D) photonic crystal (PhC) channel drop filter (CDF) using ring resonators. The increasing interest in photonic integrated circuits (PIC's) and the increasing use of all-optical fiber networks as backbones for global communication systems have been based in large part on the extremely wide optical transmission bandwidth provided by dielectric materials. Based on the analysis we present novel photonic crystal channel drop filters. Simulations demonstrate that these filters exhibit ideal transfer characteristics. Channel dropping filters (CDF's) that access one channel of a wavelength division multiplexed (WDM) signal while leaving other channels undisturbed are essential components of PIC's and optical communication systems. In this paper we have investigated such parameters which have an effect on resonant wavelength in this Channel Drop Filter, such as dielectric constant of inner, coupling, adjacent and whole rods of the structure. The dimensions of these structures are taken as 20a×19a and the area of the proposed structure is about 125.6μm{sup 2}; therefore this structure can be used in the future photonic integrated circuits. While using this design the dropping efficiency at the resonance of single ring are 100%. The spectrum of the power transmission is obtained with finite difference time domain (FDTD) method. FDTD method is the most famous method for PhC analysis. In this paper the dielectric rods have a dielectric constant of 10.65, so the refractive index is 3.26 and radius r=0.213a is located in air, where a is a lattice constant. In this we have used five scatter rods for obtaining more coupling efficiency; radius of scatter rods is set to 0.215a. The proposed structure is simulated with OptiFDTD.v.8.0 software, the different dielectric constant of rods equal to ε{sub r}−0.4, ε{sub r} and ε{sub r}+0.4 at wavelength of 1570 nm.

  4. TUNABLE RING LASER BASED ON A SEMICONDUCTOR OPTICAL AMPLIFIER AT 1300 NM USING A SIMPLE WAVELENGTH SELECTION FILTER

    PubMed Central

    Jeon, Mansik; Kim, Jeehyun; Song, Jae-Won; Lee, Ho; Choi, Sanghoon; Nelson, J. Stuart

    2009-01-01

    A simple, compact, and low cost tunable ring laser with a commercial semiconductor optical amplifier (SOA) was demonstrated. The tunable ring laser is based on an external wavelength filter cavity that is analogous with the Littman configuration with a diffraction grating, a mirror, and a simple slit. The unique structural advantage of this new system is that the slit is displaced to select a desired wavelength instead of tilting the mirror as in the Littman configuration. This allows easy control over the selected wavelength by the translating action of the slit. The full width half maximum (FWHM) wavelength turning range is 45 nm, and the wavelength resolution is about 2 pm. The demonstrated tunable ring laser has 2 mW output power. The side mode suppression ratios is 70–73 dB. PMID:20539831

  5. Random depth access full-field heterodyne low-coherence interferometry utilizing acousto-optic modulation and a complementary metaloxide semiconductor camera.

    PubMed

    Egan, Patrick; Connelly, Michael J; Lakestani, Fereydoun; Whelan, Maurice P

    2006-04-01

    With analog scanning, time-domain low-coherence interferometry lacks precise depth information, and optical carrier generation demands a linear scanning speed. Full-field heterodyne low-coherence interferometry that uses a logarithmic complementary metal-oxide semiconductor camera, acousto-optic modulation, and digital depth stepping is reported, with which random regions of interest, lateral and axial, can be accessed. Furthermore, nanometer profilometry is possible through heterodyne phase retrieval of the interference signal. The approach demonstrates inexpensive yet high-precision functional machine vision offering true digital random access in three dimensions.

  6. Numerical simulation of dual-loss-modulated Q-switched and mode-locked laser with an acousto-optic and Cr4+:YAG saturable absorber.

    PubMed

    Zhao, Shengzhi; Li, Guiqiu; Li, Dechun; Yang, Kejian; Li, Yufei; Li, Ming; Li, Tao; Zhang, Gang; Cheng, Kang

    2010-04-01

    By considering the influence of the turn-off time and the modulation frequency of the acousto-optic (AO) modulator as well as the Gaussian spatial distribution of the photon density, we give a developed rate equation model for a diode-pumped dual-loss-modulated Q-switched and mode-locked (QML) Nd:GdVO(4) laser with AO modulator and Cr(4+):YAG saturable absorber. With this developed model, the dual-loss-modulated QML laser characteristics, such as pulse width and pulse energy, can be numerically simulated, and the theoretical evaluations are in good agreement with the experimental results.

  7. Time-resolved acousto-optic interaction in single-mode optical fibers: characterization of axial nonuniformities at the nanometer scale.

    PubMed

    Alcusa-Sáez, E P; Díez, A; González-Herráez, M; Andrés, M V

    2014-03-15

    We report on a time-resolved acousto-optic interaction technique for the detection of axial nonuniformities in single-mode fibers. It is based on the propagation of short packets of flexural acoustic waves. Small axial nonuniformities (of the order of nanometers) are detected by measuring the transmittance of the fundamental mode as a function of time. It is shown that the technique allows the detection of axial nonuniformities along sections of single-mode fiber exceeding 1 m long with spatial resolution of the order of a few centimeters.

  8. Efficient diode end-pumped acousto-optically Q-switched Nd:YAG/BaTeMo2O9 Raman laser.

    PubMed

    Bai, Fen; Wang, Qingpu; Jiao, Zhiyong; Xu, Xianfeng; Zhang, Hui; Tao, Xutang

    2016-11-10

    BaTeMo2O9 (BTM) is employed to achieve efficient stimulated Raman scattering conversion in a diode end-pumped acousto-optically Q-switched Nd:YAG laser. With an incident diode power of 8.6 W, 732 mW of 1179 nm first-Stokes average output power was generated at a pulse repetition rate of 10 kHz, corresponding to a diode-to-Raman conversion efficiency of 8.5%.

  9. Laser frequency stabilisation by the Pound - Drever - Hall method using an acousto-optic phase modulator operating in the pure Raman - Nath diffraction regime

    SciTech Connect

    Baryshev, Vyacheslav N

    2012-04-30

    Frequency stabilisation of diode laser radiation has been implemented by the Pound - Drever - Hall method using a new acousto-optic phase modulator, operating in the pure Raman - Nath diffraction regime. It is experimentally shown that, as in the case of saturated-absorption spectroscopy in atomic vapour, the spatial divergence of the frequency-modulated output spectrum of this modulator does not interfere with obtaining error signals by means of heterodyne frequency-modulation spectroscopy with a frequency discriminator based on a high-Q Fabry - Perot cavity with finesse of several tens of thousands.

  10. LD end-pumped acousto-optic Q-switched 1319 nm/1338 nm dual-wavelength Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Wu, C. T.; Yu, M.; Wang, C.; Yu, K.; Yu, Y. J.; Chen, X. Y.; Jin, G. Y.

    2016-10-01

    Laser characteristics of acousto-optic Q-switched operation of 1319 nm/1338 nm dual-wavelength composite Nd:YAG laser were studied. Maximum output power of 5.77 W was achieved in CW operation. Under Q-switched operation, the maximum peak power of 3.96 kW and minimum pulse width of 65.6 ns was obtained at repetition frequency of 20 kHz with the duty ratio of 96%. The influence of the duration of the ultrasonic field acted on the Q-switch to the output characteristics of dual-wavelength composite Nd:YAG laser had been reported first time.

  11. Combination of a 2-D acousto-optic deflector with laser amplifier for efficient scanning of a Q-switched ND:YAG laser

    NASA Astrophysics Data System (ADS)

    Maák, P.; Jakab, L.; Richter, P. I.; Brignon, A.; Huignard, J.-P.

    2000-03-01

    A two-dimensional acousto-optic deflector has been combined with a large angular acceptance, laser diode-pumped Nd:YAG optical amplifier in order to obtain a scanning system with high angular resolution and with high and uniform optical transmission. Experiments have been carried out in order to optimize the set-up for intensity distribution and optical losses. The combination of newly developed nonlinear and active optical elements provides a relatively uniform intensity distribution over the scanned region corresponding to 300×300 discrete points in the back focal plane of a Fourier lens, at laser pulse energy levels of 1-5 mJ.

  12. Long-cavity all-fiber ring laser actively mode locked with an in-fiber bandpass acousto-optic modulator.

    PubMed

    Cuadrado-Laborde, C; Bello-Jiménez, M; Díez, A; Cruz, J L; Andrés, M V

    2014-01-01

    We demonstrate low-frequency active mode locking of an erbium-doped all-fiber ring laser. As the mode locker, we used a new in-fiber bandpass acousto-optic modulator showing 74% modulation depth, 3.7 dB power insertion losses, 4.5 nm of optical bandwidth, and 20 dB of nonresonant light suppression. The laser generates 330 ps mode-locked pulses over a 10 ns pedestal, at a 1.538 MHz frequency, with 130 mW of pump power.

  13. Smart Environmental Monitor Based on Neural Networks and Multi-Spectral Pattern Recognition

    DTIC Science & Technology

    1993-09-01

    acousto-optic Tunable Filter," Applied Spectroscopy , 46, 1211 (1992). 11. P. J. Treado, I. W. Levin, and E. N. Lewis, "Near-Infrared Acousto-Optic...Spectroscopic Microscopy: A Solid-State Approach to Chemical Imaging," Applied Spectroscopy , 46, 553 (1992). 14

  14. All-optical wavelength-routing switch with monolithically integrated filter-free tunable wavelength converters and an AWG.

    PubMed

    Segawa, Toru; Matsuo, Shinji; Kakitsuka, Takaaki; Shibata, Yasuo; Sato, Tomonari; Kawaguchi, Yoshihiro; Kondo, Yasuhiro; Takahashi, Ryo

    2010-03-01

    We present a compact 4x8 wavelength-routing switch that monolithically integrates fast tunable wavelength converters (TWCs) and an arrayed-waveguide grating (AWG) for optical packet switching. The TWC consists of a double-ring-resonator-coupled tunable laser which allows rapid and stable switching, and an optical gate based on a parallel amplifier structure which prevents an input optical signal from being routed through the AWG (filter-free operation). A deep-ridge waveguide technology, employed for the AWG and ring resonators, facilitates the fabrication of the switch and makes the device compact. The filter-free TWCs achieve low crosstalk of the input optical signal of less than -22 dB. The wavelength routing operation of a non-return-to-zero (NRZ) signal at 10 Gbit/s is achieved with a switching time of less than 5 ns.

  15. Note: Broadly tunable all-fiber ytterbium laser with 0.05 nm spectral width based on multimode interference filter

    SciTech Connect

    Mukhopadhyay, Pranab K. Gupta, Pradeep K.; Singh, Amarjeet; Sharma, Sunil K.; Bindra, Kushvinder S.; Oak, Shrikant M.

    2014-05-15

    A multimode interference filter with narrow transmission bandwidth and large self-imaging wavelength interval is constructed and implemented in an ytterbium doped fiber laser in all-fiber format for broad wavelength tunability as well as narrow spectral width of the output beam. The peak transmission wavelength of the multimode interference filter was tuned with the help of a standard in-fiber polarization controller. With this simple mechanism more than 30 nm (1038 nm–1070 nm) tuning range is demonstrated. The spectral width of the output beam from the laser was measured to be 0.05 nm.

  16. Measurement and optimization of fiber mechanical properties for use in a novel HTS tunable filter

    NASA Astrophysics Data System (ADS)

    Guo, Libing

    2003-10-01

    This dissertation is a study of the thermal physical properties of a single fiber to be used as a key part of an HTS tunable filter. Eight classes of candidate fibers were narrowed down to carbon and borosilicate fibers for more study. Novel measurement methods were used in this project that overcame the shortcomings of literature methods, which can only measure the properties at room temperature. The experimental apparatus was designed and built, and measurements were made of Young's modulus, tensile strength, ultimate strain, torsional modulus and thermal linear expansion of both types of fibers at both room temperature and 95K. The errors of the measurement, including random variations in fiber diameter, were analyzed statistically to determine error bounds. The measurement results were used to determine the mechanical performance of each of the fibers when applied to suspending the toractor system. Based on the working conditions of both carbon fiber and borosilicate fiber, the borosilicate fiber was chosen for this purpose. The performance margin of the fiber suspending system was estimated by using a statistical model. A new model was proposed to demonstrate the relationship of the cross-section structure of Polyacrylonitrile (PAN)-based carbon fiber and its mechanical properties. The theoretical predictions on the properties of PAN-based carbon fiber based on this model agree very well with the experimental data. The Young's modulus and tensile strength of PAN-based carbon fiber with known diameter can be calculated by a simple equation without taking time to do an experimental measurement.

  17. Liquid-crystal tunable filter spectral imaging for brain tumor demarcation

    NASA Astrophysics Data System (ADS)

    Gebhart, Steven C.; Thompson, Reid C.; Mahadevan-Jansen, Anita

    2007-04-01

    Past studies have demonstrated that combined fluorescence and diffuse reflectance spectroscopy can successfully discriminate between normal, tumor core, and tumor margin tissues in the brain. To achieve efficient, real-time surgical resection guidance with optical biopsy, probe-based spectroscopy must be extended to spectral imaging to spatially demarcate the tumor margins. We describe the design and characterization of a combined fluorescence and diffuse reflectance imaging system that uses liquid-crystal tunable filter technology. Experiments were conducted to quantitatively determine the linearity, field of view, spatial and spectral resolution, and wavelength sensitivity of the imaging system. Spectral images were acquired from tissue phantoms, mouse brain in vitro, and human cortex in vivo for functional testing of the system. The spectral imaging system produces measured intensities that are linear with sample emission intensity and integration time and possesses a 1 in. (2.54 cm) field of view for a 7 in. (18 cm) object distance. The spectral resolution is linear with wavelength, and the spatial resolution is pixel-limited. The sensitivity spectra for the imaging system provide a guide for the distribution of total image integration time between wavelengths. Functional tests in vitro demonstrate the capability to spectrally discriminate between brain tissues based on exogenous fluorescence contrast or endogenous tissue composition. In vivo imaging captures adequate fluorescence and diffuse reflectance intensities within a clinically viable 2 min imaging time frame and demonstrates the importance of hemostasis to acquired signal strengths and imaging speed.

  18. Brain tumor demarcation with liquid-crystal tunable filter spectral imaging

    NASA Astrophysics Data System (ADS)

    Gebhart, Steven C.; Mahadevan-Jansen, Anita

    2006-02-01

    Past studies have demonstrated that combined fluorescence and diffuse reflectance spectroscopy can successfully discriminate between normal, tumor core, and tumor margin tissues in the brain. To achieve efficient surgical resection guidance with optical biopsy, probe-based spectroscopy must be extended to spectral imaging to spatially demarcate the tumor margins. This paper describes the design and testing of a combined fluorescence and diffuse reflectance imaging system which uses liquid-crystal tunable filter technology. Experiments were conducted to quantitatively determine its linearity, field of view, spatial and spectral resolution, and wavelength sensitivity. For functional testing, spectral images were acquired from tissue phantoms, mouse brain in vitro, and rat brain cortex in vivo. The spectral imaging system is characterized by measured intensities which are linear with sample emission intensity and integration time, a one-inch field of view for a seven-inch object distance, spectral resolution which is linear with wavelength, spatial resolution which is pixel-limited, and sensitivity functions which provide a guide for the distribution of total image integration time between wavelengths. Functional testing demonstrated good spatial and spectral constrast between brain tissue types, the capability to acquire adequate fluorescence and diffuse reflectance intensities within a one-minute imaging timeframe, and the importance of hemostasis to acquired signal strengths and imaging speed.

  19. Electro-Mechanical Simulation of a Large Aperture MOEMS Fabry-Perot Tunable Filter

    NASA Technical Reports Server (NTRS)

    Kuhn, Jonathan L.; Barclay, Richard B.; Greenhouse, Matthew A.; Mott, D. Brent; Satyapal, Shobita; Powers, Edward I. (Technical Monitor)

    2000-01-01

    We are developing a micro-machined electrostatically actuated Fabry-Perot tunable filter with a large clear aperture for application in high through-put wide-field imaging spectroscopy and lidar systems. In the first phase of this effort, we are developing key components based on coupled electro-mechanical simulations. In particular, the movable etalon plate design leverages high coating stresses to yield a flat surface in drum-head tension over a large diameter (12.5 mm). In this approach, the cylindrical silicon movable plate is back etched, resulting in an optically coated membrane that is suspended from a thick silicon support ring. Understanding the interaction between the support ring, suspended membrane, and coating is critical to developing surfaces that are flat to within stringent etalon requirements. In this work, we present the simulations used to develop the movable plate, spring suspension system, and electrostatic actuation mechanism. We also present results from tests of fabricated proof of concept components.

  20. A modeling-based assessment of acousto-optic sensing for monitoring high-intensity focused ultrasound lesion formation

    NASA Astrophysics Data System (ADS)

    Adams, Matthew Tyler

    Real-time acousto-optic (AO) sensing---a dual-wave modality that combines ultrasound with diffuse light to probe the optical properties of turbid media---has been demonstrated to non-invasively detect changes in ex vivo tissue optical properties during high-intensity focused ultrasound (HIFU) exposure. The AO signal indicates the onset of lesion formation and predicts resulting lesion volumes. Although proof-of-concept experiments have been successful, many of the underlying parameters and mechanisms affecting thermally induced optical property changes and the AO detectability of HIFU lesion formation are not well understood. In thesis, a numerical simulation was developed to model the AO sensing process and capture the relevant acoustic, thermal, and optical transport processes. The simulation required data that described how optical properties changed with heating. Experiments were carried out where excised chicken breast was exposed to thermal bath heating and changes in the optical absorption and scattering spectra (500 nm--1100 nm) were measured using a scanning spectrophotometer and an integrating sphere assembly. Results showed that the standard thermal dose model currently used for guiding HIFU treatments needs to be adjusted to describe thermally induced optical property changes. To model the entire AO process, coupled models were used for ultrasound propagation, tissue heating, and diffusive light transport. The angular spectrum method was used to model the acoustic field from the HIFU source. Spatial-temporal temperature elevations induced by the absorption of ultrasound were modeled using a finite-difference time-domain solution to the Pennes bioheat equation. The thermal dose model was then used to determine optical properties based on the temperature history. The diffuse optical field in the tissue was then calculated using a GPU-accelerated Monte Carlo algorithm, which accounted for light-sound interactions and AO signal detection. The simulation was

  1. A Bio-Realistic Analog CMOS Cochlea Filter With High Tunability and Ultra-Steep Roll-Off.

    PubMed

    Wang, Shiwei; Koickal, Thomas Jacob; Hamilton, Alister; Cheung, Rebecca; Smith, Leslie S

    2015-06-01

    This paper presents the design and experimental results of a cochlea filter in analog very large scale integration (VLSI) which highly resembles physiologically measured response of the mammalian cochlea. The filter consists of three specialized sub-filter stages which respectively provide passive response in low frequencies, actively tunable response in mid-band frequencies and ultra-steep roll-off at transition frequencies from pass-band to stop-band. The sub-filters are implemented in balanced ladder topology using floating active inductors. Measured results from the fabricated chip show that wide range of mid-band tuning including gain tuning of over 20 dB, Q factor tuning from 2 to 19 as well as the bio-realistic center frequency shift are achieved by adjusting only one circuit parameter. Besides, the filter has an ultra-steep roll-off reaching over 300 dB/dec. By changing biasing currents, the filter can be configured to operate with center frequencies from 31 Hz to 8 kHz. The filter is 9th order, consumes 59.5 ∼ 90.0 μW power and occupies 0.9 mm2 chip area. A parallel bank of the proposed filter can be used as the front-end in hearing prosthesis devices, speech processors as well as other bio-inspired auditory systems owing to its bio-realistic behavior, low power consumption and small size.

  2. Tunable Q-switched thulium-doped Fiber Laser using multiwall carbon nanotube and Fabry-Perot Etalon filter

    NASA Astrophysics Data System (ADS)

    Ahmad, H.; Muhamad, A.; Sharbirin, A. S.; Samion, M. Z.; Ismail, M. F.

    2017-01-01

    In this paper, we demonstrate an electro-tunable Thulium-doped Fiber Laser (TDFL) using a voltage-controlled Fabry-Perot Etalon (FPE) filter with passive Q-switching capability, obtained by using a multi-walled carbon-nanotube (MWCNT) thin-film as a saturable absorber (SA). To the best of our knowledge, this is the first demonstration of a wavelength-tunable Q-switched TDFL using an FPE filter. The tunable TDFL has a wavelength-tuning range of 41.95 nm, from 1965.40 nm up to 2007.35 nm. Q-switching operation starts at a pump power of 94.72 mW and destabilizes at a maximum input pump power of 146.39 mW. By varying the pump power, the repetition rate and the pulse width can be tuned with a maximum tuning range of 15.5 kHz and 7.0 μs respectively. The laser also has a maximum pulse energy of 82.6 nJ and a peak power of 27.52 mW. The use of the MWCNT thin-film as an SA generates a stable Q-switching operation, which is verified by its relatively high signal-to-noise ratio at a value of 55.0 dB.

  3. Design of multistack Fabry-Perot structure with defect as tunable transmission filter for CWDM using FDTD method

    NASA Astrophysics Data System (ADS)

    Bandyopadhyay, Rajorshi; Chakraborty, Rajib

    2015-06-01

    The translational symmetry of the periodicity in a photonic crystal can be disturbed by introducing a controlled defect in its periodicity. The photon localization causes a pass band in the photonic bandgap. Based on this concept, we are proposing the design of a tunable narrow band filter for multiple wavelengths used for coarse wave length division multiplexing (CWDM) system. To achieve that, a multiple stack Fabry Perot structure with suitable stack materials and controllable defect is considered. The proposed Fabry Perot structure consists of periodic layers of electro optic material Lithium Niobate (nH) and Magnesium Fluoride (nL). The optical length of each such layer is their corresponding quarter wave length width at the design wavelength λ0 (1.55 μm). The reflection band of the quarter wavelength multilayer structure is formed due to the periodic repetition of the (LH)NL, where L and H are the quarter wavelength width of the nL and nH material respectively and N is the number of bilayers. A quarter wave layer L is then inserted between the groups of (LH)N and (HL)N to form the Fabry Perot resonator structure which can be used for narrow band transmission filter. The simulation has been carried out in both FDTD and TMM method and compared. As the refractive index of the Lithium Niobate can be tuned electro-optically, the filter can also be made tunable.

  4. Two wavelength operation of an acousto-optically tuned quantum cascade laser and direct measurements of quantum cascade laser level lifetimes

    NASA Astrophysics Data System (ADS)

    Patel, C. Kumar N.; Barron-Jimenez, Rodolfo; Dunayevskiy, Ilya; Tsvid, Gene; Lyakh, Arkadiy

    2017-01-01

    We report simultaneous two wavelength operation of an acousto-optically tuned quantum cascade laser (QCL). The two wavelengths can be independently tuned as well as independently switched, retaining the submicrosecond switching capability. In addition, we have used the two wavelength operation as a tool for the direct measure of the lifetimes of the lasing states in a practical QCL. The lifetime measurements in an operational QCL are facilitated by our ability to vary the frequency separation between two simultaneously lasing wavelengths. The measured lifetime is 0.6 ps ± 0.2 ps for our quantum cascade laser. The two wavelength operation of QCLs paves the way for time resolved pump/probe studies of infrared phenomena and provides direct insight into the effectiveness of various QCL structure designs.

  5. Tunable extended depth of field using a liquid crystal annular spatial filter.

    PubMed

    Klapp, Iftach; Solodar, Asi; Abdulhalim, Ibrahim

    2014-03-15

    A tunable extended depth of field (EDOF) imaging is presented using temporal multiplexing and a low-cost eight-ring, annular liquid crystal spatial light modulator. By changing between different phase profiles in the pupil plane of a lens we perform several levels of EDOF. Using these levels as a "database" it is shown by temporal multiplexing how to decompose tunable levels of EDOF.

  6. Analysis of the frequency response of a TeO{sub 2} slow shear wave acousto-optic cell exposed to radiation

    SciTech Connect

    Erteza, I.A.

    1995-04-01

    Radiation testing of photonic components is not new, however component level testing to date has not completely addressed quantities which are important to system behavior. One characteristic that is of particular importance for optical processing systems is the frequency response. In this report, we present the analysis of data from an experiment designed to provide a preliminary understanding of the effects of radiation on the frequency response of acousto-optic devices. The goal of the analysis is to describe possible physical mechanisms responsible for the radiation effects and to discuss the effects on signal processing functionality. The experiment discussed in this report was designed by Sandia National Laboratories and performed by Sandia and Phillips Laboratory personnel at White Sands Missile Range (WSMR). In the experiment, a TeO{sub 2} slow shear wave acousto-optic cell was exposed to radiation from the WSMR linear accelerator. The TeO{sub 2} cell was placed in an experimental configuration which allowed swept frequency diffracted power measurements to be taken during radiation exposure and recovery. A series of exposures was performed. Each exposure consisted of between 1 to 800, 1{mu}sec radiation pulses (yielding exposures of 2.25 kRad(Si) to 913 kRad(Si)), followed by recovery time. At low total and cumulative doses, the bandshape of the frequency response (i.e. diffracted power vs. frequency) remained almost identical during and after radiation. At the higher exposures, however, the amplitude and width of the frequency response changed as the radiation continued, but returned to the original shape slowly after the radiation stopped and recovery proceeded. It is interesting to note that the location of the Bragg degeneracy does not change significantly with radiation. In this report, we discuss these effects from the perspective of anisotropic Bragg diffraction and momentum mismatch, and we discuss the effect on the signal processing functionality.

  7. Versatile tunable current-mode universal biquadratic filter using MO-DVCCs and MOSFET-based electronic resistors.

    PubMed

    Chen, Hua-Pin

    2014-01-01

    This paper presents a versatile tunable current-mode universal biquadratic filter with four-input and three-output employing only two multioutput differential voltage current conveyors (MO-DVCCs), two grounded capacitors, and a well-known method for replacement of three grounded resistors by MOSFET-based electronic resistors. The proposed configuration exhibits high-output impedance which is important for easy cascading in the current-mode operations. The proposed circuit can be used as either a two-input three-output circuit or a three-input single-output circuit. In the operation of two-input three-output circuit, the bandpass, highpass, and bandreject filtering responses can be realized simultaneously while the allpass filtering response can be easily obtained by connecting appropriated output current directly without using additional stages. In the operation of three-input single-output circuit, all five generic filtering functions can be easily realized by selecting different three-input current signals. The filter permits orthogonal controllability of the quality factor and resonance angular frequency, and no inverting-type input current signals are imposed. All the passive and active sensitivities are low. Postlayout simulations were carried out to verify the functionality of the design.

  8. Nano-optomechanical characterization of surface-plasmon-based tunable filter integrated with comb-drive actuator

    NASA Astrophysics Data System (ADS)

    Honma, H.; Mitsudome, M.; Ishida, M.; Sawada, K.; Takahashi, K.

    2017-03-01

    We report a tunable plasmonic color filter consisting of a metamaterial periodic grating and microelectromechanical systems (MEMS) actuator. An aluminum subwavelength grating is integrated with electrostatic comb-drive actuators to expand the metal subwavelength period, which allows continuous control of the excitation wavelength of surface plasmons (SPs). We develop a batch fabrication process by employing a liftoff technique using an electron beam resist altered by the electron dose depending on different aspect ratios (length/width) for various components such as the subwavelength grating, nanohinge flexural suspensions, and comb fingers. We successfully demonstrate a continuous shift in the excitation wavelength over the 514–635 nm range by nanopitch expansion. The design margin of the grating period for SP excitation is evaluated by comparing the experimental pitch variation and theoretically calculated values. The resonance frequency of the tunable filter is optically measured to be approximately 10 kHz. The optically and mechanically obtained values agree well with the theory of electrostatic actuation and finite-difference time-domain simulation.

  9. Low power consumption and continuously tunable all-optical microwave filter based on an opto-mechanical microring resonator.

    PubMed

    Liu, Li; Yang, Yue; Li, Zhihua; Jin, Xing; Mo, Wenqin; Liu, Xing

    2017-01-23

    We propose and experimentally demonstrate a continuously tunable all-optical microwave filter using a silicon opto-mechanical microring resonator (MRR). By finely adjusting the pump light with submilliwatt power level, transmission spectrum of the MRR could be continuously shifted based on the nonlinear effects, including the opto-mechanical effect and thermo-optic effect. Therefore, in the case of optical single sideband (OSSB) modulation, the frequency intervals between the optical carrier (near one MRR resonance) and the corresponding resonance could be flexibly manipulated, which is the critical factor to achieve continuously tunable microwave photonic filter (MPF). In the experiment, the central frequency of the MPF could be continuously tuned from 6 GHz to 19 GHz with the pump power lower than -2.5 dBm. The proposed opto-mechanical device is competent to process microwave signals with dominant advantages, such as compact footprint, all-optical control and low power consumption. In the future, using light to control light, the opto-mechanical structure on silicon platforms might have many other potential applications in microwave systems, such as microwave switch.

  10. MWIR/LWIR filter based on Liquid-Crystal Fabry-Perot structure for tunable spectral imaging detection

    NASA Astrophysics Data System (ADS)

    Zhang, Huaidong; Muhammad, Afzal; Luo, Jun; Tong, Qing; Lei, Yu; Zhang, Xinyu; Sang, Hongshi; Xie, Changsheng

    2015-03-01

    An electrically tunable medium-wave infrared (MWIR)/long-wave infrared (LWIR) filter based on the key structure of Liquid-Crystal (LC) Fabry-Perot (FP), which works in the wavelength range from 2.5 μm to 12 μm, is designed and fabricated successfully in this paper. According to the optical interference principle of the FP cavity and electrically controlled birefringence of nematic LC molecules, the particular functions including spectral selection and spectral staring and spectral adjustment, can be realized by the developed MWIR/LWIR filter driven and controlled electrically. As to the LC-FP filter, both planar reflective mirrors are shaped by depositing a layer of aluminum (Al) film (∼60 nm) over one side of double-side polished Zinc Selenide (ZnSe) wafer (∼1 mm), and then polyimide (PI) layer with the thickness of ∼100 nm is coated directly on Al film. With typical sandwich architecture, the depth of the cavity with nematic LC molecules sealed in is ∼7.5 μm. To make sure the LC molecules parallel aligned and twist regularly under voltage driving signal applied on Al film, which also acts as electrode, the V-grooves are formed in PI layer with the depth of ∼90 nm and the width of ∼350 nm at average by strong rubbing. The typical transmission spectrum in MWIR&LWIR wavelength range and several spectral images in MWIR wavelength range based on the fabricated LC-FP filter, have been obtained through applying a voltage driving-signal with different root-means-square (RMS) value over the electrodes of LC-FP filter in the selected voltage range from 0VRMS to 19.8VRMS. The testing result demonstrates a prospect of realization smart spectral imaging and further integrating the LC-FP filter with infrared focal plane arrays (FPAs) to achieve the purpose infrared multispectral imaging. The developed MWIR&LWIR LC-FP filters show some obvious advantages such as wide working wavelength range, electrically tunable spectral selection, ultra-compact, low cost, being

  11. Tunable RF photonic phase shifter based on optical DSB modulation and FBG filtering

    NASA Astrophysics Data System (ADS)

    Wei, Yongfeng; Huang, Shanguo; Sun, Kai; Gao, Xinlu; Gu, Wanyi

    2016-01-01

    A broadband RF photonic phase shifter that can achieve the tunable phase shift with little RF amplitude variation is presented. It is based on homodyne mixing technique. The beating between phase-modulated optical carrier and the sidebands can generate RF signal with desired phase shift. Results show the RF phase shifter can achieve a continuous phase shift with low amplitude variation.

  12. Acoustically tunable optical transmission through a subwavelength hole with a bubble

    NASA Astrophysics Data System (ADS)

    Maksymov, Ivan S.; Greentree, Andrew D.

    2017-03-01

    Efficient manipulation of light with sound in subwavelength-sized volumes is important for applications in photonics, phononics, and biophysics, but remains elusive. We theoretically demonstrate the control of light with MHz-range ultrasound in a subwavelength, 300-nm-wide water-filled hole with a 100-nm-radius air bubble. Ultrasound-driven pulsations of the bubble modulate the effective refractive index of the hole aperture, which gives rise to spectral tuning of light transmission through the hole. This control mechanism opens up novel opportunities for tunable acousto-optic and optomechanical metamaterials, and all-optical ultrasound transduction.

  13. Tetravalent chromium (Cr(4+)) as laser-active ion for tunable solid-state lasers

    NASA Technical Reports Server (NTRS)

    Seas, A.; Petricevic, V.; Alfano, Robert R.

    1992-01-01

    Generation of femtosecond pulses from a continuous-wave mode-locked chromium-doped forsterite (Cr(4+):Mg2SiO4) laser has been accomplished. The forsterite laser was actively mode-locked using an acousto-optic modulator operating at 78 MHz with two Brewster high-dispersion glass prisms for intra-cavity chirp compensation. Transform-limited sub-100-fs pulses were routinely generated in the TEM(sub 00) mode with 85 mW of continuous power (with 1 percent output coupler), tunable over 1230-1280 nm. The shortest pulses of 60-fs pulsewidth were measured.

  14. Development and Acceptance Testing of the Dual Wheel Mechanism for the Tunable Filter Imager Cryogenic Instrument on the JWST

    NASA Technical Reports Server (NTRS)

    Leckie, Martin; Ahmad, Zakir

    2010-01-01

    The James Webb Space Telescope (JWST) will carry four scientific instruments, one of which is the Tunable Filter Imager (TFI), which is an instrument within the Fine Guidance Sensor. The Dual Wheel (DW) mechanism is being designed, built and tested by COM DEV Ltd. under contract from the Canadian Space Agency. The DW mechanism includes a pupil wheel (PW) holding seven coronagraphic masks and two calibration elements and a filter wheel (FW) holding nine blocking filters. The DW mechanism must operate at both room temperature and at 35K. Successful operation at 35K comprises positioning each optical element with the required repeatability, for several thousand occasions over the five year mission. The paper discusses the results of testing geared motors and bearings at the cryogenic temperature. In particular bearing retainer design and PGM-HT material, the effects of temperature gradients across bearings and the problems associated with cooling mechanisms down to cryogenic temperatures. The results of additional bearing tests are described that were employed to investigate an abnormally high initial torque experienced at cryogenic temperatures. The findings of these tests, was that the bearing retainer and the ball/race system could be adversely affected by the large temperature change from room temperature to cryogenic temperature and also the temperature gradient across the bearing. The DW mechanism is now performing successfully at both room temperature and at cryogenic temperature. The life testing of the mechanism is expected to be completed in the first quarter of 2010.

  15. Improved tunable filter-based multispectral imaging system for detection of blood stains on construction material substrates

    NASA Astrophysics Data System (ADS)

    Janchaysang, Suwatwong; Sumriddetchkajorn, Sarun; Buranasiri, Prathan

    2013-06-01

    We present the improved tunable filter based multispectral imaging system for detecting blood stains on construction materials. Based upon the reflectance and Kubelka Munk absorbance spectra stocked from our previous work, we modify the blood discrimination criteria to make the system more efficient by replacing the old criteria which make use of polynomial fitting with new criteria associated with a few wavelengths images. The newly established criteria are tested to be able to detect blood against other stains almost as efficient as the old criteria, while the number of spectral images required for detecting blood stains are reduced significantly from 64 to 9 spectral images. The reduction of required spectral images will reduce the time needed for image capturing and blood detection criteria application with little sacrificing of the specificity and sensitivity of the system.

  16. C- and L-band tunable fiber ring laser using a two-taper Mach-Zehnder interferometer filter.

    PubMed

    Wang, Xiaozhen; Li, Yi; Bao, Xiaoyi

    2010-10-15

    A stable C- and L-band tunable fiber ring laser, using a two-taper Mach-Zehnder interferometer (MZI) as a filter, is proposed and demonstrated experimentally. One of the two taper waists is mechanically bent to tune the laser wavelength. Being amplified by an L-band erbium-doped fiber amplifier and an erbium-doped fiber, respectively, the fiber ring laser has a full L-band (1564-1605nm) and C-band (1550-1565nm) tuning range with a side-mode suppression ratio as high as 50dB. The laser linewidth and the minimum tuning step are related to the MZI's cavity length. It was also found that thermal annealing relieved the internal stresses of the tapers and greatly improved the laser performance.

  17. Electrically tunable infrared filter based on the liquid crystal Fabry-Perot structure for spectral imaging detection.

    PubMed

    Zhang, Huaidong; Muhammmad, Afzal; Luo, Jun; Tong, Qing; Lei, Yu; Zhang, Xinyu; Sang, Hongshi; Xie, Changsheng

    2014-09-01

    An electrically tunable infrared (IR) filter based on the liquid crystal (LC) Fabry-Perot (FP) key structure, which works in the wavelength range from 5.5 to 12 μm, is designed and fabricated successfully. Both planar reflective mirrors with a very high reflectivity of ∼95%, which are shaped by depositing a layer of aluminum (Al) film over one side of a double-sided polished zinc selenide wafer, are coupled into a dual-mirror FP cavity. The LC materials are filled into the FP cavity with a thickness of ∼7.5  μm for constructing the LC-FP filter, which is a typical type of sandwich architecture. The top and bottom mirrors of the FP cavity are further coated by an alignment layer with a thickness of ∼100  nm over Al film. The formed alignment layer is rubbed strongly to shape relatively deep V-grooves to anchor LC molecules effectively. Common optical tests show some particular properties; for instance, the existing three transmission peaks in the measured wavelength range, the minimum full width at half-maximum being ∼120  nm, and the maximum adjustment extent of the imaging wavelength being ∼500  nm through applying the voltage driving signal with a root mean square (RMS) value ranging from 0 to ∼19.8  V. The experiment results are consistent with the simulation, according to our model setup. The spectral images obtained in the long-wavelength IR range, through the LC-FP device driven by the voltage signal with a different RMS value, demonstrates the prospect of the realization of smart spectral imaging and further integrating the LC-FP filter with IR focal plane arrays. The developed LC-FP filters show some advantages, such as electrically tunable imaging wavelength, very high structural and photoelectronic response stability, small size and low power consumption, and a very high filling factor of more than 95% compared with common MEMS-FP spectral imaging approaches.

  18. An arrayed infrared filter based on liquid crystal Fabry-Perot effect for electrically tunable spectral imaging detection

    NASA Astrophysics Data System (ADS)

    Lin, Jiuning; Tong, Qing; Luo, Jun; Lei, Yu; Zhang, Xinyu; Sang, Hongshi; Xie, Changsheng

    2015-12-01

    An arrayed electrically tunable infrared (IR) filter based on the key structure of liquid crystal Fabry-Perot (LC-FP) working in the wavelength range from 2.5 to 12 μm, is designed and fabricated successfully. According to the electrically controlled birefringence characteristics of nematic LC molecules, the refractive index of LC materials filled into a prefabricated microcavity can be adjusted by the spatial electric field stimulated between the top aluminum electrode patterned by conventional UV-photolithography and the bottom aluminum electrode in the LC-FP. The particular functions including key spectral selection and spectral adjustment, can be performed by the developed LC-FP filter driven and controlled electrically. Our experiments show that the maximum transmittance of the transmission peaks is ~24% and the peaks of transmission spectrum shift through applying different voltage signals with a root mean square (RMS) value ranging from 0 to ~21.7Vrms. The experimental results are consistent with the simulation according to the model constructed by us. As a 4-channel array-type IR filter, the top electrode of the device is composed of four same sub-electrodes, which is powered, respectively, to select desired transmission spectrum. Each of the units in the device is operated separately and synchronously, which means that spectral images of the same object can be obtained with different wavelengths in one shot. Without any mechanical parts, the developed LC-FP filter exhibits several advantages including ultra-small size, low cost, high reliability, high spectral selectivity, and compact integration.

  19. High coherent bi-chromatic laser with gigahertz splitting produced by the high diffraction orders of acousto-optic modulator used for coherent population trapping experiments.

    PubMed

    Yun, Peter; Tan, Bozhong; Deng, Wei; Gu, Sihong

    2011-12-01

    To prepare the coherent population trapping (CPT) states with rubidium and cesium, the commonly used atoms in CPT studies, a coherent bi-chromatic light field with frequency difference of several GHz is a basic requirement. With a 200 MHz center frequency acousto-optic modulator (AOM), we have realized bi-chromatic laser fields with several GHz frequency splits through high diffraction orders. We have experimentally studied the coherence between two frequency components of a bi-chromatic laser beam, which is composed of ±6 orders with frequency split of 3 GHz diffracted from the same laser beam, and the measured residual phase noise is Δφ(2)<0.019 rad(2). The bi-chromatic laser fields were used to prepare CPT states with (85)Rb and (87)Rb atoms, and high contrast CPT signals were obtained. For CPT states preparation, our study result shows that it is a feasible approach to generate the bi-chromatic light field with larger frequency splits through high diffraction orders of AOM.

  20. Optimization of doubly Q-switched lasers with both an acousto-optic modulator and a GaAs saturable absorber.

    PubMed

    Li, Dechun; Zhao, Shengzhi; Li, Guiqiu; Yang, Kejian

    2007-08-20

    A doubly Q-switched laser with both an acousto-optic (AO) modulator and a GaAs saturable absorber can obtain a more symmetric and shorter pulse with high pulse peak power, which has been experimentally proved. The key parameters of an optimally coupled doubly Q-switched laser with both an AO modulator and a GaAs saturable absorber are determined, and a group of general curves are generated for what we believe is the first time, when the single-photon absorption (SPA) and two-photon absorption (TPA) processes of GaAs are combined, and the Gaussian spatial distributions of the intracavity photon density and the initial population-inversion density as well as the influence of the AO Q-switch are considered. These key parameters include the optimal normalized coupling parameter, the optimal normalized GaAs saturable absorber parameters, and the normalized parameters of the AO Q-switch, which can maximize the output energy. Meanwhile, the corresponding normalized energy, the normalized peak power, and the normalized pulse width are given. The curves clearly show the dependence of the optimal key parameters on the parameters of the gain medium, the GaAs saturable absorber, the AO Q-switch, and the resonator. Sample calculations for a diode-pumped Nd3+:YVO4 laser with both an AO modulator and a GaAs saturable absorber are presented to demonstrate the use of the curves and the relevant formulas.

  1. Hybrid wide-band, low-phase-noise scheme for Raman lasers in atom interferometry by integrating an acousto-optic modulator and a feedback loop.

    PubMed

    Wang, Kai; Yao, Zhanwei; Li, Runbing; Lu, Sibin; Chen, Xi; Wang, Jin; Zhan, Mingsheng

    2016-02-10

    We report a hybrid scheme for phase-coherent Raman lasers with low phase noise in a wide frequency range. In this scheme, a pair of Raman lasers with a frequency difference of 3.04 GHz is generated by the ±1-order diffracted lights of an acousto-optic modulator (1.52 GHz), where a feedback loop is simultaneously applied for suppressing the phase noise. The beat width of the Raman lasers is narrower than 3 Hz. In the low-frequency range, the phase noise of the Raman lasers is suppressed by 35 dB with the feedback. The phase noise is less than -109  dBc/Hz in the high-frequency range. The sensitivity of an atom gyroscope employing the hybrid Raman lasers can be implicitly improved 10 times. Due to the better high-frequency response, the sensitivity is not limited by the durations of Raman pulses. This work is important for improving the performance of atom-interferometer-based measurements.

  2. Improved performance of analog and digital acousto-optic modulation with feedback under profiled beam propagation for secure communication using chaos

    NASA Astrophysics Data System (ADS)

    Almehmadi, Fares S.; Chatterjee, Monish R.

    2014-12-01

    Using intensity feedback, the closed-loop behavior of an acousto-optic hybrid device under profiled beam propagation has been recently shown to exhibit wider chaotic bands potentially leading to an increase in both the dynamic range and sensitivity to key parameters that characterize the encryption. In this work, a detailed examination is carried out vis-à-vis the robustness of the encryption/decryption process relative to parameter mismatch for both analog and pulse code modulation signals, and bit error rate (BER) curves are used to examine the impact of additive white noise. The simulations with profiled input beams are shown to produce a stronger encryption key (i.e., much lower parametric tolerance thresholds) relative to simulations with uniform plane wave input beams. In each case, it is shown that the tolerance for key parameters drops by factors ranging from 10 to 20 times below those for uniform plane wave propagation. Results are shown to be at consistently lower tolerances for secure transmission of analog and digital signals using parameter tolerance measures, as well as BER performance measures for digital signals. These results hold out the promise for considerably greater information transmission security for such a system.

  3. Doppler-free, multiwavelength acousto-optic deflector for two-photon addressing arrays of Rb atoms in a quantum information processor

    NASA Astrophysics Data System (ADS)

    Kim, Sangtaek; McLeod, Robert R.; Saffman, M.; Wagner, Kelvin H.

    2008-04-01

    We demonstrate a dual wavelength acousto-optic deflector (AOD) designed to deflect two wavelengths to the same angles by driving with two RF frequencies. The AOD is designed as a beam scanner to address two-photon transitions in a two-dimensional array of trapped neutral Rb87 atoms in a quantum computer. Momentum space is used to design AODs that have the same diffraction angles for two wavelengths (780 and 480 nm) and have nonoverlapping Bragg-matched frequency response at these wavelengths, so that there will be no cross talk when proportional frequencies are applied to diffract the two wavelengths. The appropriate crystal orientation, crystal shape, transducer size, and transducer height are determined for an AOD made with a tellurium dioxide crystal (TeO2). The designed and fabricated AOD has more than 100 resolvable spots, widely separated band shapes for the two wavelengths within an overall octave bandwidth, spatially overlapping diffraction angles for both wavelengths (780 and 480 nm), and a 4 μs or less access time. Cascaded AODs in which the first device upshifts and the second downshifts allow Doppler-free scanning as required for addressing the narrow atomic resonance without detuning. We experimentally show the diffraction-limited Doppler-free scanning performance and spatial resolution of the designed AOD.

  4. In-plane deeply-etched optical MEMS notch filter with high-speed tunability

    NASA Astrophysics Data System (ADS)

    Sabry, Yasser M.; Eltagoury, Yomna M.; Shebl, Ahmed; Soliman, Mostafa; Sadek, Mohamed; Khalil, Diaa

    2015-12-01

    Notch filters are used in spectroscopy, multi-photon microscopy, fluorescence instrumentation, optical sensors and other life science applications. One type of notch filter is based on a fiber-coupled Fabry-Pérot cavity, which is formed by a reflector (external mirror) facing a dielectric-coated end of an optical fiber. Tailoring this kind of optical filter for different applications is possible because the external mirror has fewer mechanical and optical constraints. In this paper we present optical modeling and implementation of a fiber-coupled Fabry-Pérot filter based on dielectric-coated optical fiber inserted into a micromachined fiber groove facing a metallized micromirror, which is driven by a high-speed MEMS actuator. The optical MEMS chip is fabricated using deep reactive ion etching (DRIE) technology on a silicon on insulator wafer, where the optical axis is parallel to the substrate (in-plane) and the optical/mechanical components are self-aligned by the photolithographic process. The DRIE etching depth is 150 μm, chosen to increase the micromirror optical throughput and improving the out-of-plane stiffness of the MEMS actuator. The MEMS actuator type is closing-gap, while its quality factor is almost doubled by slotting the fixed plate. A low-finesse Fabry-Pérot interferometer is formed by the metallized surface of the micromirror and a cleaved end of a standard single-mode fiber, for characterization of the MEMS actuator stroke and resonance frequency. The actuator achieves a travel distance of 800 nm at a resonance frequency of 89.9 kHz. The notch filter characteristics were measured using an optical spectrum analyzer, and the filter exhibits a free spectral range up to 100 nm and a notch rejection ratio up to 20 dB around a wavelength of 1300 nm. The presented device provides batch processing and low-cost production of the filter.

  5. Fast wavelength-tunable picosecond pulses from a passively mode-locked Er fiber laser using a galvanometer-driven intracavity filter.

    PubMed

    Ozeki, Yasuyuki; Tashiro, Daigo

    2015-06-15

    We experimentally investigate fast wavelength-tuning characteristics of a polarization-maintaining Er fiber laser, which is mode-locked with a semiconductor saturable absorber mirror. Wavelength tuning was accomplished with an intracavity filter incorporating a galvanometer mirror and a diffraction grating. Within the tunability of 30 nm, we achieved a wavelength-tuning speed of <5 ms. We also show that the variation of repetition rates can be suppressed to <200 Hz by simply shifting the position of the grating. The presented scheme for generating wavelength-tunable pulses will be potentially useful for coherent Raman spectral imaging.

  6. Wide wavelength range tunable one-dimensional silicon nitride nano-grating guided mode resonance filter based on azimuthal rotation

    NASA Astrophysics Data System (ADS)

    Yukino, Ryoji; Sahoo, Pankaj K.; Sharma, Jaiyam; Takamura, Tsukasa; Joseph, Joby; Sandhu, Adarsh

    2017-01-01

    We describe wavelength tuning in a one dimensional (1D) silicon nitride nano-grating guided mode resonance (GMR) structure under conical mounting configuration of the device. When the GMR structure is rotated about the axis perpendicular to the surface of the device (azimuthal rotation) for light incident at oblique angles, the conditions for resonance are different than for conventional GMR structures under classical mounting. These resonance conditions enable tuning of the GMR peak position over a wide range of wavelengths. We experimental demonstrate tuning over a range of 375 nm between 500 nm˜875 nm. We present a theoretical model to explain the resonance conditions observed in our experiments and predict the peak positions with show excellent agreement with experiments. Our method for tuning wavelengths is simpler and more efficient than conventional procedures that employ variations in the design parameters of structures or conical mounting of two-dimensional (2D) GMR structures and enables a single 1D GMR device to function as a high efficiency wavelength filter over a wide range of wavelengths. We expect tunable filters based on this technique to be applicable in a wide range of fields including astronomy and biomedical imaging.

  7. Tunable multi-wavelength thulium-doped fiber laser incorporating two-stage cascaded Sagnac loop comb filter

    NASA Astrophysics Data System (ADS)

    Zhu, Lianqing; He, Wei; Dong, Mingli; Lou, Xiaoping; Luo, Fei

    2016-08-01

    A tunable multi-wavelength narrow-linewidth thulium-doped fiber laser employing two-stage cascaded Sagnac loop mirrors is proposed and experimentally demonstrated. The designed fiber laser is composed of a pump source, wavelength division multiplex, circulator, thulium-doped fiber, polarization controllers (PCs), couplers and polarization-maintaining fibers (PMFs). Two cascaded Sagnac loops are used as the cavity reflector and filter, and the proposed filter is fabricated using two sections of PMFs with 2-m and 1-m lengths, respectively. In the experiment, the laser threshold is 110 mW, and laser can emit single, double, triple, quadruple and quintuple wavelengths in the spectral range of 1873-1901 nm through the simultaneous adjustment of the two PCs. The power fluctuations and 3-dB linewidth are less than 2.1 dB and 0.2 nm, respectively, over 10 min at room temperature, and the side-mode suppression ratio is greater than 20 dB. The proposed laser will be useful in various fields, such as spectral analysis, fiber sensing and optical communication.

  8. A low-noise widely tunable Gm-C filter with frequency calibration

    NASA Astrophysics Data System (ADS)

    Yu, Wang; Jing, Liu; Na, Yan; Hao, Min

    2016-09-01

    A fourth-order Gm-C Chebyshev low-pass filter is presented as channel selection filter for reconfigurable multi-mode wireless receivers. Low-noise technologies are proposed in optimizing the noise characteristics of both the Gm cells and the filter topology. A frequency tuning strategy is used by tuning both the transconductance of the Gm cells and the capacitance of the capacitor banks. To achieve accurate cut-off frequencies, an on-chip calibration circuit is presented to compensate for the frequency inaccuracy introduced by process variation. The filter is fabricated in a 0.13 μm CMOS process. It exhibits a wide programmable bandwidth from 322.5 kHz to 20 MHz. Measured results show that the filter has low input referred noise of 5.9 \\text{nV}/\\sqrt {\\text{Hz}} and high out-of-band IIP3 of 16.2 dBm. It consumes 4.2 and 9.5 mW from a 1 V power supply at its lowest and highest cut-off frequencies respectively. Project supported by the National Natural Science Foundation of China (No. 61574045).

  9. Baseband integrated acousto-optic frequency shifter/modulator module for fiber optic at 1.3 mum.

    PubMed

    Tsai, C S; Cheng, Z Y

    1993-01-01

    A baseband integrated acoustooptic (AO) frequency shifter/modulator module that consists of a pair of titanium-indiffused proton-exchanged (TIPE) waveguide lenses and a pair of cascaded guided-wave AO Bragg cells has been realized in a Y-cut LiNbO(3) waveguide substrate 0.1 cmx1.0 cmx2.0 cm in size. A device module operating at the optical wavelength of 1.3 mum has provided a -3-dB tunable bandwidth of 120 MHz at baseband. The frequency-shifted or -modulated light propagates in a fixed direction, irrespective of the magnitude of frequency shift or modulation, and is focused into a spot (FWHM) of 6.2-mum size on the output edge of the waveguide. Accordingly, this optical frequency shifter/module can be directly interfaced with single-mode optical fibers to facilitate applications in fiber optic systems.

  10. Tunable narrowband microwave photonic filter created by stimulated Brillouin scattering from a silicon nanowire.

    PubMed

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

    2015-09-01

    We demonstrate the first, to the best of our knowledge, functional signal processing device based on stimulated Brillouin scattering in a silicon nanowire. We use only 1 dB of on-chip stimulated Brillouin scattering gain to create an RF photonic notch filter with 48 dB of suppression, 98 MHz linewidth, and 6 GHz frequency tuning. This device has potential applications in on-chip microwave signal processing and establishes the foundation for the first CMOS-compatible high-performance RF photonic filter.

  11. Fluid-controlled tunable infrared filtering in hollow plasmonic nanofin cavities

    NASA Astrophysics Data System (ADS)

    Ho, Ya-Lun; Abasaki, Minoru; Yin, Shichen; Liu, Xin; Delaunay, Jean-Jacques

    2016-10-01

    Subwavelength structures sustaining surface plasmons have been employed in numerous fields due to their small size and ability to manipulate light beyond the diffraction limit. Light filtering using small-size plasmonic devices is a promising means of portable spectroscopy for purposes such as on-site chemical analyses. However, most plasmonic filters can only tune the resonance band by modifying the geometry of the structure or changing the incident light angle. Here, we present a plasmonic nanofin-cavity structure having a narrow band with its resonance wavelength controlled by varying the fluid in the hollow cavities of the filter. Control of the narrow-band resonance is realized over a wide range because of the coupling between the stationary surface plasmons generated from the nanofin-cavity mode and the propagating surface plasmons. The hollow cavity design enables fluid to be easily injected and removed, so that the filtered band can be controlled without the need for a complex and bulky structure or application of an external voltage.

  12. Band-gap tunable dielectric elastomer filter for low frequency noise

    NASA Astrophysics Data System (ADS)

    Jia, Kun; Wang, Mian; Lu, Tongqing; Zhang, Jinhua; Wang, Tiejun

    2016-05-01

    In the last decades, diverse materials and technologies for sound insulation have been widely applied in engineering. However, suppressing the noise radiation at low frequency still remains a challenge. In this work, a novel membrane-type smart filter, consisting of a pre-stretched dielectric elastomer membrane with two compliant electrodes coated on the both sides, is presented to control the low frequency noise. Since the stiffness of membrane dominates its acoustic properties, sound transmission band-gap of the membrane filter can be tuned by adjusting the voltage applied to the membrane. The impedance tube experiments have been carried out to measure the sound transmission loss (STL) of the filters with different electrodes, membrane thickness and pre-stretch conditions. The experimental results show that the center frequency of sound transmission band-gap mainly depends on the stress in the dielectric elastomer, and a large band-gap shift (more than 60 Hz) can be achieved by tuning the voltage applied to the 85 mm diameter VHB4910 specimen with pre-stretch {λ }0=3. Based on the experimental results and the assumption that applied electric field is independent of the membrane behavior, 3D finite element analysis has also been conducted to calculate the membrane stress variation. The sound filter proposed herein may provide a promising facility to control low frequency noise source with tonal characteristics.

  13. High-repetition-rate widely tunable LiF : \\mathbf{\\mathsf{F}}_\\mathbf{\\mathsf{2}}^{-} color center lasers

    NASA Astrophysics Data System (ADS)

    Men, Shaojie; Liu, Zhaojun; Cong, Zhenhua; Rao, Han; Zhang, Sasa; Liu, Yang; Zverev, Petr G.; Konyushkin, Vasily A.; Zhang, Xingyu

    2016-02-01

    High-repetition-rate tunable LiF:\\text{F}2- color center lasers pumped by quasi-continuous-wave diode-side-pumped acousto-optically Q-switched Nd:YAG laser are demonstrated. Littrow-grating and Littman-grating tuning schemes are studied respectively. In the Littrow-grating scheme, the tuning range was 1085 nm to 1275 nm, and the maximal average output power was 275 mW. In the Littman-grating scheme, the tuning range was 1105.5 nm to 1215.5 nm, and the maximal average output power was 135 mW.

  14. Temperature effect on a tilted birefringent filter in a tunable laser: A limitation for Raman spectroscopy

    SciTech Connect

    Burneau, A.; Humbert, B. )

    1989-12-15

    The temperature effect on the wave number selected by a tilted birefringent filter inside a dye laser cavity is measured and theoretically discussed. For a quartz plate at Brewster angle, the wave-number shift is observed between 1.1 and 1.35 cm{sup {minus}1} K{sup {minus}1} according to the angle between the crystal optical axis and the incident plane. A thorough calculation is fully in agreement with these results: the main part of the shift is related to the variation of refractive indices, but both the thickness expansion and the wavelength disperson of indices moderate the temperature effect. The observed shift is still larger than the width at half height of the exciting line necessary for Raman spectroscopy. A filter with three plates whose thicknesses are in ratio 1:4:16, which transmits a band of satisfactory width, cannot be used however if a rigorous temperature stability is not achieved. A practical solution is found by combining a 1:4 filter and a Fabry--Perot etalon.

  15. Carrier tracking and tunable passband filters for TDM-LDV mine detection

    NASA Astrophysics Data System (ADS)

    Burgett, Richard; Sabatier, James M.; Aranchuk, Vyacheslav

    2010-04-01

    Using laser Doppler vibrometers (LDVs) to find buried land mines has been shown to have a high probability of detection coupled with a low probability of false alarms. Equally good results have been achieved using a 16-beam LDV. Time division multiplexing (TDM) of this multiple-beam LDV has also been investigated as a means of increasing the scanning speed and potentially allowing the sensor to move down the road at speeds faster than that allowed using stop-and-stare LDVs. A moving platform induces Doppler shifts in the LDV beams that are not perpendicular to the motion vector. This shift can be much greater than the modulation bandwidth of a stationary LDV signal; therefore, the demodulation must allow for the shift either by increasing the processing bandwidth, which increases the system noise or by tracking the Doppler offset and adjusting a band pass filter's center frequency. A method has been developed to track the carrier frequency to compensate for the Doppler offset for each of the 16 channels caused by the moving platform and then adjusting the center frequency of a digital band pass filter. This paper will present the basic filter structure and compare the noise statistics from two different carrier tracking methods that were investigated.

  16. A Large Aperture Fabry-Perot Tunable Filter Based On Micro Opto Electromechanical Systems Technology

    NASA Technical Reports Server (NTRS)

    Greenhouse, Matt; Mott, Brent; Powell, Dan; Barclay, Rich; Hsieh, Wen-Ting

    2002-01-01

    A research and development effort sponsored by the NASA Goddard Spaceflight Center (GSFC) is focused on applying Micro Opto Electromechanical Systems (MOEMS) technology to create a miniature Fabry-Perot tunable etalon for space and ground-based near infrared imaging spectrometer applications. Unlike previous devices developed for small-aperture telecommunications systems, the GSFC research is directed toward a novel 12 - 40 mm aperture for astrophysical studies, including emission line imaging of galaxies and nebulae, and multi-spectral redshift surveys in the 1.1 - 2.3 micron wavelength region. The MOEMS design features integrated electrostatic scanning of the 11-micron optical gap, and capacitance micrometry for closed loop control of parallelism within a 10-nm tolerance. The low thermal mass and inertia inherent in MOEMS devices allows for rapid cooling to the proposed 30 K operating temperature, and high frequency response. Achieving the proposed 6-nm aperture flatness (with an effective finesse of 50) represents the primary technical challenge in the current 12-mm prototype.

  17. Anemia detection utilizing diffuse reflectance spectra from the palpebral conjunctiva and tunable liquid crystal filter technology

    NASA Astrophysics Data System (ADS)

    McMurdy, John W., III; Jay, Gregory D.; Suner, Selim; Crawford, Gregory P.

    2006-03-01

    Anemia is a serious worldwide disorder affecting 2 billion people globally. While the only clinically accepted method of diagnosis remains an invasive blood draw and laboratory analysis, numerous attempts have been made to measure total blood hemoglobin noninvasively. Although the palpebral conjunctiva can be used as a poor qualitative indicator of anemia, a quantitative analysis of the conjunctiva using visible diffuse reflectance spectroscopy can provide an accurate and easy method of noninvasive measurement. Preliminary studies using a traditional grating based spectrometer have shown this method of analysis to be effective and accurate at diagnosing anemia and are presented here. An alternative device to collect diffuse reflectance spectroscopy based on tunable liquid crystal technology that is comparatively inexpensive and compact is also presented. Deformed helix ferroelectric liquid crystals (DHFLC) can be tuned fully across the visible spectrum and have a narrow bandwidth of reflection. A handheld microspectrometer facilitates this technique becoming a clinically viable method of analysis and enables total hemoglobin to be measured quickly, and without the need of a blood draw. The rapidity of this test can make total hemoglobin measurement a new vital sign, increasingly important because of the concurrent appearance of anemia with numerous other disorders.

  18. Modeling of power spectral density of modified von Karman atmospheric phase turbulence and acousto-optic chaos using scattered intensity profiles over discrete time intervals

    NASA Astrophysics Data System (ADS)

    Chatterjee, Monish R.; Mohamed, Fathi H. A.

    2014-10-01

    In recent research, propagation of plane electromagnetic (EM) waves through a turbulent medium with modified von Karman phase characteristics was modeled and numerically simulated using transverse planar apertures representing narrow phase turbulence along the propagation path. The case for extended turbulence was also studied by repeating the planar phase screens multiple times over the propagation path and incorporating diffractive effects via a split-step algorithm. The goal of the research reported here is to examine two random phenomena: (a) atmospheric turbulence due to von Karman-type phase fluctuations, and (b) chaos generated in an acousto-optic (A-O) Bragg cell under hybrid feedback. The latter problem has been thoroughly examined for its nonlinear dynamics and applications in secure communications. However, the statistical characteristics (such as the power spectral density (PSD)) of the chaos have not been estimated in recent work. To that end, treating the chaos phenomena as a random process, the time waveforms of the chaos intensity and their spectra are numerically evaluated over a (large) number of time iterations. These spectra are then averaged to derive the equivalent PSD of the A-O chaos. For the turbulence problem, an optical beam passing through an input pinhole is propagated through a random phase screen (placed at different locations) to a desired distance (typically near-field) under different levels of turbulence strength. The resulting spatial intensity profile is then averaged and the process repeated over a (large) number of pre-specified time intervals. From this data, once again, the turbulence PSD is calculated via the Fourier spectra of the average intensity snapshots. The results for the two systems are compared.

  19. Gate-tunable valley-spin filtering in silicene with magnetic barrier

    SciTech Connect

    Wu, X. Q.; Meng, H.

    2015-05-28

    We theoretically study the valley- and spin-resolved scattering through magnetic barrier in a one layer thick silicene, using the mode-matching method for the Dirac equation. We show that the spin-valley filtering effect can be achieved and can also be tuned completely through both a top and bottom gate. Moreover, when reversing the sign of the staggered potential, we find the direction of the valley polarization is switched while the direction of spin polarization is unchanged. These results can provide some meaningful information to design valley valve residing on silicene.

  20. A tunable electrochromic fabry-perot filter for adaptive optics applications.

    SciTech Connect

    Blaich, Jonathan David; Kammler, Daniel R.; Ambrosini, Andrea; Sweatt, William C.; Verley, Jason C.; Heller, Edwin J.; Yelton, William Graham

    2006-10-01

    The potential for electrochromic (EC) materials to be incorporated into a Fabry-Perot (FP) filter to allow modest amounts of tuning was evaluated by both experimental methods and modeling. A combination of chemical vapor deposition (CVD), physical vapor deposition (PVD), and electrochemical methods was used to produce an ECFP film stack consisting of an EC WO{sub 3}/Ta{sub 2}O{sub 5}/NiO{sub x}H{sub y} film stack (with indium-tin-oxide electrodes) sandwiched between two Si{sub 3}N{sub 4}/SiO{sub 2} dielectric reflector stacks. A process to produce a NiO{sub x}H{sub y} charge storage layer that freed the EC stack from dependence on atmospheric humidity and allowed construction of this complex EC-FP stack was developed. The refractive index (n) and extinction coefficient (k) for each layer in the EC-FP film stack was measured between 300 and 1700 nm. A prototype EC-FP filter was produced that had a transmission at 500 nm of 36%, and a FWHM of 10 nm. A general modeling approach that takes into account the desired pass band location, pass band width, required transmission and EC optical constants in order to estimate the maximum tuning from an EC-FP filter was developed. Modeling shows that minor thickness changes in the prototype stack developed in this project should yield a filter with a transmission at 600 nm of 33% and a FWHM of 9.6 nm, which could be tuned to 598 nm with a FWHM of 12.1 nm and a transmission of 16%. Additional modeling shows that if the EC WO{sub 3} absorption centers were optimized, then a shift from 600 nm to 598 nm could be made with a FWHM of 11.3 nm and a transmission of 20%. If (at 600 nm) the FWHM is decreased to 1 nm and transmission maintained at a reasonable level (e.g. 30%), only fractions of a nm of tuning would be possible with the film stack considered in this study. These tradeoffs may improve at other wavelengths or with EC materials different than those considered here. Finally, based on our limited investigation and material set

  1. Tunable negative-tap photonic microwave filter based on a cladding-mode coupler and an optically injected laser of large detuning.

    PubMed

    Chan, Sze-Chun; Liu, Qing; Wang, Zhu; Chiang, Kin Seng

    2011-06-20

    A tunable negative-tap photonic microwave filter using a cladding-mode coupler together with optical injection locking of large wavelength detuning is demonstrated. Continuous and precise tunability of the filter is realized by physically sliding a pair of bare fibers inside the cladding-mode coupler. Signal inversion for the negative tap is achieved by optical injection locking of a single-mode semiconductor laser. To couple light into and out of the cladding-mode coupler, a pair of matching long-period fiber gratings is employed. The large bandwidth of the gratings requires injection locking of an exceptionally large wavelength detuning that has never been demonstrated before. Experimentally, injection locking with wavelength detuning as large as 27 nm was achieved, which corresponded to locking the 36-th side mode. Microwave filtering with a free-spectral range tunable from 88.6 MHz to 1.57 GHz and a notch depth larger than 35 dB was obtained.

  2. Validity of retinal oxygen saturation analysis: Hyperspectral imaging in visible wavelength with fundus camera and liquid crystal wavelength tunable filter

    NASA Astrophysics Data System (ADS)

    Hirohara, Yoko; Okawa, Yoshitaka; Mihashi, Toshifumi; Yamaguchi, Tatsuo; Nakazawa, Naoki; Tsuruga, Yasuko; Aoki, Hiroyuki; Maeda, Naoyuki; Uchida, Ichiro; Fujikado, Takashi

    2007-05-01

    The purpose of this paper was to investigate the feasibility of a newly developed hyperspectral fundus imaging camera with a liquid crystal tunable filter. The intensities of different wavelengths of light transmitted through an artery, vein, and the area surrounding these vessels and reflected out were measured, and the differential spectral absorptions were analyzed. Measurements were made from 16 normal eyes and from two artificial capillaries. The ratios of absorption (ROA) of arteries to veins from 500 to 580 nm (range 1) and from 600 to 720 nm (range 2) were calculated. For all eyes, the ROArange1 was larger than ROArange2. The ROA obtained from the artificial capillary filled with blood saturated with oxygen or nitrogen was similar to that of simulated data of oxy- and deoxyhemoglobin extinction rate. Most ROAs of human eyes were lower than those of the simulated data and the artificial capillaries. Oxygen saturation analysis by hyperspectral fundus imaging of retinal vessels were qualitatively in agreement with the in vitro analysis or simulated values. However, further improvements are necessary to evaluate the oxygen saturation quantitatively in the retinal blood vessels.

  3. Tunable ultracompact chip-integrated multichannel filter based on plasmon-induced transparencies

    SciTech Connect

    Yang, Xiaoyu; Chai, Zhen; Lu, Cuicui; Yang, Hong; Hu, Xiaoyong E-mail: qhgong@pku.edu.cn; Gong, Qihuang E-mail: qhgong@pku.edu.cn

    2014-06-02

    Nanoscale multichannel filter is realized in plasmonic circuits directly, which consists of four plasmonic nanocavities coupled via a plasmonic waveguide etched in a gold film. The feature device size is only 1.35 μm, which is reduced by five orders of magnitude compared with previous reports. The optical channels are formed by transparency windows of plasmon-induced transparencies. A shift of 45 nm in the central wavelengths of optical channels is obtained when the plasmonic coupled-nanocavities are covered with a 100-nm-thick poly(methyl methacrylate) layer. This work opens up the possibility for the realization of solid quantum chips based on plasmonic circuits.

  4. Realization of spectral tunable filter based on thermal effect in microfiber structure

    NASA Astrophysics Data System (ADS)

    Nodehi, S.; Mohammed, W. S.; Ahmad, H.; Harun, S. W.

    2016-03-01

    This paper demonstrates a new approach for tuning the extinction ratio of a complex microfiber structure output using thermal effect. The microfiber filter device comprises of a microfiber Mach-Zehnder interferometer followed a knot structure, where temperature is controlled by a DC current applied to a copper wire placed inside the knot. This enables electrical tuning, where applying electrical current increases the temperature and affects the optical path. The change of temperature facilitates the fine tuning of the resonance output spectrum. From the experiment, it was observed that the extinction ratio of the output comb spectrum can be controlled within 2 dB to 10 dB by varying the current rating from 0 A to 1.22 A.

  5. A tunable line filter polychromator for gas temperature measurements using laser Raman scattering

    NASA Technical Reports Server (NTRS)

    Grossman, J. J.; Muramoto, M.

    1975-01-01

    A proprietary laser line filter spectrograph (LLFS) was modified to test for improved remote measurement of atmospheric temperature by Raman spectroscopy of the rotational bands of N2 and O2. Both grating scan measurements with fixed PMT and polychromator image plane PMT scans with fixed grating setting were made using HeNe and Ar(+) lasers. The LLFS was found to have a laser line rejection ratio at 6A from the laser line and provides resolved rotational Raman spectral display at the polychromator exit plane. Spectral resolution is adequate to measure and correct for background in the Stokes spectrum. It is anticipated that this system should allow measurement of gas or atmospheric temperature to + or - 1 C.

  6. Highly-efficient, tunable green, phosphor-converted LEDs using a long-pass dichroic filter and a series of orthosilicate phosphors for tri-color white LEDs.

    PubMed

    Oh, Ji Hye; Oh, Jeong Rok; Park, Hoo Keun; Sung, Yeon-Goog; Do, Young Rag

    2012-01-02

    This study introduces a long-pass dichroic filter (LPDF) on top of a phosphor-converted LED (pc-LED) packing associated with each corresponding tunable orthosilicate ((Ba,Sr)2SiO4:Eu) phosphor in order to fabricate tunable green pc-LEDs. These LPDF-capped green pc-LEDs provide luminous efficacies between 143–173 lm/W at 60 mA in a wavelength range between 515 and 560 nm. These tunable green pc-LEDs can replace green semiconductor-type III-V LEDs, which present challenges with respect to generating high luminous efficacy. We also introduce the highly-efficient tunable green pc-LEDs into tri-color white LED systems that combine an InGaN blue LED and green/red full down-converted pc-LEDs. The effect of peak wavelength in the tunable green pc-LEDs on the optical properties of a tri-color package white LED is analyzed to determine the proper wavelength of green color for tri-color white LEDs. The tri-color white LED provides excellent luminous efficacy (81.5–109 lm/W) and a good color rendering index (64–87) at 6500 K of correlated color temperature (CCT) with the peak wavelength of green pc-LEDs. The luminous efficacy of the LPDF-capped green monochromatic pc-LED and tri-color package with tunable green pc-LEDs can be increased by improving the external quantum efficiency of blue LEDs and the conversion efficiency of green pc-LEDs.

  7. MO-A-BRD-01: An Investigation of the Dynamic Response of a Novel Acousto-Optic Liquid Crystal Detector for Full-Field Transmission Ultrasound Breast Imaging

    SciTech Connect

    Rosenfield, J.R.; La Riviere, P.J.; Sandhu, J.S.

    2014-06-15

    Purpose: To characterize the dynamic response of a novel acousto-optic (AO) liquid crystal detector for high-resolution transmission ultrasound breast imaging. Transient and steady-state lesion contrast were investigated to identify optimal transducer settings for our prototype imaging system consistent with the FDA limits of 1 W/cm{sup 2} and 50 J/cm{sup 2} on the incident acoustic intensity and the transmitted acoustic energy flux density. Methods: We have developed a full-field transmission ultrasound breast imaging system that uses monochromatic plane-wave illumination to acquire projection images of the compressed breast. The acoustic intensity transmitted through the breast is converted into a visual image by a proprietary liquid crystal detector operating on the basis of the AO effect. The dynamic response of the AO detector in the absence of an imaged breast was recorded by a CCD camera as a function of the acoustic field intensity and the detector exposure time. Additionally, a stereotactic needle biopsy breast phantom was used to investigate the change in opaque lesion contrast with increasing exposure time for a range of incident acoustic field intensities. Results: Using transducer voltages between 0.3 V and 0.8 V and exposure times of 3 minutes, a unique one-to-one mapping of incident acoustic intensity to steady-state optical brightness in the AO detector was observed. A transfer curve mapping acoustic intensity to steady-state optical brightness shows a high-contrast region analogous to the linear portion of the Hurter-Driffield curves of radiography. Using transducer voltages between 1 V and 1.75 V and exposure times of 90 s, the lesion contrast study demonstrated increasing lesion contrast with increasing breast exposure time and acoustic field intensity. Lesion-to-background contrast on the order of 0.80 was observed. Conclusion: Maximal lesion contrast in our prototype system can be obtained using the highest acoustic field intensity and the

  8. Tunable and switchable dual-wavelength single polarization narrow linewidth SLM erbium-doped fiber laser based on a PM-CMFBG filter.

    PubMed

    Yin, Bin; Feng, Suchun; Liu, Zhibo; Bai, Yunlong; Jian, Shuisheng

    2014-09-22

    A tunable and switchable dual-wavelength single polarization narrow linewidth single-longitudinal-mode (SLM) erbium-doped fiber (EDF) ring laser based on polarization-maintaining chirped moiré fiber Bragg grating (PM-CMFBG) filter is proposed and demonstrated. For the first time as we know, the CMFBG inscribed on the PM fiber is applied for the wavelength-tunable and-switchable dual-wavelength laser. The PM-CMFBG filter with ultra-narrow transmission band (0.1 pm) and a uniform polarization-maintaining fiber Bragg grating (PM-FBG) are used to select the laser longitudinal mode. The stable single polarization SLM operation is guaranteed by the PM-CMFBG filter and polarization controller. A tuning range of about 0.25 nm with about 0.075 nm step is achieved by stretching the uniform PM-FBG. Meanwhile, the linewidth of the fiber laser for each wavelength is approximate 6.5 and 7.1 kHz with a 20 dB linewidth, which indicates the laser linewidth is approximate 325 Hz and 355 Hz FWHM.

  9. Discretely tunable thulium-doped fiber-based polarization-maintaining master oscillator power amplifier using fiber Bragg grating arrays as spectral filters

    NASA Astrophysics Data System (ADS)

    Tiess, Tobias; Junaid, Saher; Becker, Martin; Rothhardt, Manfred; Bartelt, Hartmut; Jäger, Matthias

    2016-06-01

    Thulium (Tm)-doped fiber lasers offer a broad emission bandwidth in the 2-μm region, providing the perfect basis to develop broadly tunable laser sources, e.g., for spectroscopic applications. Recently, a tuning principle for pulsed fiber lasers has been reported, which is based on a fiber Bragg grating (FBG) array as a discrete spectral filter. This concept uniquely combines an unrivaled spectral freedom for tailored tuning ranges with a monolithic layout preserving the inherent advantages of fiber-integrated systems. In this study, we investigate this discrete tuning method using a Tm-doped fiber laser in the spectral domain around 1950 nm. While the laser emits linearly polarized light based on a polarization-maintaining (PM) resonator, we also examine the possibility of using standard FBG arrays inscribed in non-PM fiber. In order to highlight the prospect for tunable high-power operation, the tunable seed laser is implemented in a master oscillator power amplifier configuration scaling the average power to ˜28 W. With a tuning range of up to 76 nm, the emission characteristics of the system are investigated showing pulse durations down to 11 ns and a very good spectral signal contrast with narrow linewidth.

  10. Tunable UV Filters

    NASA Technical Reports Server (NTRS)

    Bruner, Marilyn E. (Principal Investigator); Rosenberg, William A.

    1996-01-01

    This report describes an investigation intended to determine the practical short wavelength limit for Fabry-Perot etalons operating in the far ultraviolet. This portion of the investigation includes a design study of multilayer dielectric reflector coatings that would be required by such an etalon. Results of the study indicate that etalons may be made to operate at wavelengths as short as 121 nm.

  11. High-peak-power sub-nanosecond intracavity KTiOPO4 optical parametric oscillator pumped by a dual-loss modulated laser with acousto-optic modulator and single-walled carbon nanotube

    NASA Astrophysics Data System (ADS)

    Qiao, Junpeng; Zhao, Shengzhi; Yang, Kejian; Zhao, Jia; Li, Guiqiu; Li, Dechun; Li, Tao; Qiao, Wenchao; Lu, Jianren; Wang, Yonggang; Chu, Hongwei; Luan, Chao

    2016-08-01

    A high-peak-power low-repetition-rate sub-nanosecond intracavity KTiOPO4 (KTP) optical parametric oscillator (OPO) pumped by a doubly Q-switched and mode-locked (QML) YVO4/Nd:YVO4 laser with an acousto-optic modulator (AOM) and a single-walled carbon nanotube saturable absorber (SWCNT-SA) has been demonstrated. A maximum output power of 373 mW at a signal wavelength of 1570 nm was obtained. The smallest pulse width, highest pulse energy, and greatest peak power of mode-locking pulses were estimated to be 119 ps, 124 µJ, and 1.04 MW, respectively, under a maximum incident pump power of 8.3 W and an AOM repetition rate of 2 kHz. This OPO operation paves a simple way to produce eye-safe laser sources at 1570 nm with low repetition rates, small pulse widths, and high peak powers.

  12. Tunable narrow-bandpass filter based on an asymmetric photonic bandgap structure with a dual-mode liquid crystal.

    PubMed

    Wang, Hsiao-Tsung; Timofeev, Ivan V; Chang, Kai; Zyryanov, Victor Ya; Lee, Wei

    2014-06-16

    A one-dimensional asymmetric photonic crystal with dual-frequency liquid crystal as a central defect layer was demonstrated. Such asymmetric structure was characterized by the dramatic increase in intensity of the electric field of light localized at the overlapped photonic bandgap edges, thereby enhancing the observed transmittance of the spectral windows originating from the defect layer. The defect layer was made of a dual-mode liquid crystal that exhibited not only electrical tunability and switchability but also optical bistability. Consequently, tunable and bistable defect modes can be realized in the photonic structure. This asymmetric photonic crystal structure is promising and should be further explored for photonic device applications.

  13. Improved flatness and tunable bandwidth of the supercontinuum generation in all-normal dispersion-flattened PCF using Littman-Metcalf optical bandpass filter

    NASA Astrophysics Data System (ADS)

    Jing, Qi; zhang, Xia; Ma, Huifang; Huang, Yongqing; Ren, Xiaomin

    2012-09-01

    We have proved that in an all-normal dispersion-flattened photonic crystal fiber (PCF), the four-wave mixing (FWM) process dominantly affects the flatness of the generated supercontinuum (SC). The numerical results show that pulses with steepened edges can enhance the FWM conversion efficiency during the SC's generation and the minima of the spectral oscillatory structure will be smoothed. A double-pass Littman-Metcalf optical bandpass filter is used to make the 1.60 ps hyperbolic-Secant shaped pulses obtain steepened edges. The experimental results show that the flatness of the SC generated from the 4 nm filtered pulses is improved by 0.21 dB. The SC with 10-65 nm tunable bandwidths is obtained by adjusting the filter bandwidth from 1 nm to 7 nm. Further numerical results show that the filter induced SC's flatness improvement is more effective for pulses with 2.0-4.0 ps FWHM. The improved SC can be used for applications which require stable modulation carriers and flexible bandwidth.

  14. Tunable plasmonic crystal

    DOEpatents

    Dyer, Gregory Conrad; Shaner, Eric A.; Reno, John L.; Aizin, Gregory

    2015-08-11

    A tunable plasmonic crystal comprises several periods in a two-dimensional electron or hole gas plasmonic medium that is both extremely subwavelength (.about..lamda./100) and tunable through the application of voltages to metal electrodes. Tuning of the plasmonic crystal band edges can be realized in materials such as semiconductors and graphene to actively control the plasmonic crystal dispersion in the terahertz and infrared spectral regions. The tunable plasmonic crystal provides a useful degree of freedom for applications in slow light devices, voltage-tunable waveguides, filters, ultra-sensitive direct and heterodyne THz detectors, and THz oscillators.

  15. Teal Ruby Experiment. Phase I Definition Study. Volume I. Part 2. Appendixes

    DTIC Science & Technology

    1977-05-01

    the optics and fixed filters * Hughes Aircraft Company for the monolithic focal plane and processor * Rockwell International Science Center for... filters , and pointing sub- system; manufacture and subsystem test of these elements * Final assembly and system level tests of the complete sensor system...LOCKHEED MISSILES & SPACE COMPANY. INC. LMSC-5699533 WADIM I. DOBROV - Acousto-Optical Tunable Filter Assemblies Responsibilities * Detailed design, analysis

  16. Tunable radio frequency photonics filter using a comb-based optical tapped delay line with an optical nonlinear multiplexer.

    PubMed

    Ziyadi, Morteza; Mohajerin-Ariaei, Amirhossein; Chitgarha, Mohammad Reza; Khaleghi, Salman; Almaiman, Ahmed; Cao, Yinwen; Abouzaid, Amin; Shamee, Bishara; Tur, Moshe; Paraschis, Loukas; Langrock, Carsten; Fejer, Martin M; Touch, Joseph D; Willner, Alan E

    2015-07-15

    A radio frequency (RF) photonic filter is experimentally demonstrated using an optical tapped delay line (TDL) based on an optical frequency comb and a periodically poled lithium niobate (PPLN) waveguide as multiplexer. The approach is used to implement RF filters with variable bandwidth, shape, and center-frequency.

  17. Discovery of a high-z protocluster with tunable filters: the case of 6C0140+326 at z= 4.4

    NASA Astrophysics Data System (ADS)

    Kuiper, E.; Hatch, N. A.; Venemans, B. P.; Miley, G. K.; Röttgering, H. J. A.; Kurk, J. D.; Overzier, R. A.; Pentericci, L.; Bland-Hawthorn, J.; Cepa, J.

    2011-10-01

    We present the first results obtained using a tunable narrow-band filter in the search for high-z protoclusters. Using the recently commissioned red tunable filter on the Gran Telescopio Canarias, we have searched for Lyα emitters in a 75 arcmin2 field centred on the z= 4.413 radio galaxy 6C0140+326. With three different wavelength tunings, we find a total of 27 unique candidate Lyα emitters. The availability of three different wavelength tunings allows us to make estimates of the redshifts for each of the objects. It also allows us to separate a possible protocluster from a structure in the immediate foreground. This division shows that the foreground region contains significantly fewer Lyα emitters. Also, the spatial distribution of the objects in the protocluster field deviates from a random distribution at the 2.5σ level. The observed redshift distribution of the emitters is different from the expected distribution of a blank field at the ˜3σ level, with the Lyα emitters concentrated near the radio galaxy at z > 4.38. The 6C0140+326 field is denser by a factor of 9 ± 5 than a blank field, and the number density of Lyα emitters close to the radio galaxy is similar to that of the z˜ 4.1 protocluster around TN J1338-1942. We thus conclude that there is an overdensity of Lyα emitters around the radio galaxy 6C0140+326. This is one of few known overdensities at such a high redshift.

  18. Measurement of Isotope Shifts, Hyperfine Splittings and Stark Shift for the Ytterbium (6S)2 SINGLET-S(0) to (6S6P) TRIPLET-P(1) Transition Using AN Acousto-Optically Modulated Laser Beam.

    NASA Astrophysics Data System (ADS)

    Li, Jian

    1995-11-01

    Accurate measurements of isotope shifts, hyperfine splittings and Stark shifts are of interest for studying atomic structure. This thesis reports a new method to precisely measure small frequency intervals. This was done using an acousto-optic modulator to frequency shift part of a laser beam. The frequency shifted and unshifted laser beams were then superimposed and excited an atomic beam. The laser frequency was scanned across the transition while fluorescence produced by the radiative decay of the excited state was detected by a photomultiplier. Each transition generated two peaks in the spectrum separated by the acousto-optic modulation frequency, which permitted the frequency to be calibrated. This method was tested by measuring the isotope shifts and hyperfine splittings of the ytterbium rm (6s)^2 ^1S_0to(6s6p) ^3P_1 transition at 555.6 nm. The shifts (MHz) relative to ^{176} Yb are: ^{173}Yb {it F}=7/2,-1432.1+/-1.2; ^{171}Yb {it F}=1/2, -1176.9+/-1.1; ^{174}Yb, 953.8+/-1.0; ^{172}Yb 1953.9+/-1.6; ^{170}Yb 3240.4+/-2.8; ^{173}Yb {it F}=5/2,3265.8+/-2.8; ^ {168}Yb, 4611.9+/-4.4; ^ {171,173}Yb {it F}=3/2,4760.1 +/-3.7 where the negative sign indicates that the transition occurs at a lower frequency than in ^{176}Yb. The magnetic dipole (a) and electric quadrupole (b) hyperfine coupling constants (MHz) of the (6s6p) ^3P_1 state for ^{171,173}Yb were determined to be a_{171}=3959.1 +/-3.0, a_{173}=-1094.44+/-0.84 and b_{173}=-827.89+/-0.85. These results were in agreement with the most accurate data found in the literature that were obtained by measuring frequency shifts using a Fabry Perot etalon whose length was stabilized with a helium neon laser locked to an iodine line. In contrast, our method uses cheaper and simpler apparatus. Next, the Stark shift of the ytterbium rm (6s)^2 ^1S_0to(6s6p) ^3P_1 transition was measured by passing the atomic beam through a uniform electric field. The Stark shift rate was found to be -15.419+/-0.048 kHz/(kV/cm)^2. No

  19. Design and implementation of film coating for tunable liquid crystal Fabry-Perot filter working in mid-infrared spectral region

    NASA Astrophysics Data System (ADS)

    Zhang, Huaidong; Fu, Anbang; Zhang, Xinyu; Sang, Hongshi; Xie, Changsheng

    2013-10-01

    In this paper, we design and implementation anti-reflection and high reflection film for tunable LC-FP filter working in typical medium wave infrared (MWIR) spectral region. As to reflection mirror, we complete it by depositing gold film on the silicon substrate. By using the analytical method of dividing amplitude multiple beam interference to simulate the reflectance, the reflectivity result of the gold film is around 98% at the average in the MWIR spectral region. When take the absorption of the gold film into consideration, the gold film should be thin under the condition that it is conductive well. The anti-reflection film is introduced to reduce the reflection of the other side of the wafer. In anti-reflection structure, we simulate the reflection of the films with the algorithm of the equivalent membrane and fulfill our design with the technology of vapor deposition. Finally, we test the total transmittance of the wafer deposited gold films and anti-reflection films, which is about 0.2% of single chip. By making use of the wafer designed by us, we fabricate the LC-FP filter by placing two wafers side by side with the anti-reflection structure face to the direction of wavelength incident. Simultaneously, the LC layer with fixed thickness is sealed between the two high reflection mirrors formed by gold film. Compared with other method to fabricate mid-infrared FP filter, deposition of reflection and anti-reflection films on wafer have the advantage of low cost, simple technology.

  20. Optimization of a femtosecond Ti : sapphire amplifier using a acouto-optic programmable dispersive filter and a genetic algorithm.

    SciTech Connect

    Korovyanko, O. J.; Rey-de-Castro, R.; Elles, C. G.; Crowell, R. A.; Li, Y.

    2006-01-01

    The temporal output of a Ti:Sapphire laser system has been optimized using an acousto-optic programmable dispersive filter and a genetic algorithm. In-situ recording the evolution of spectral phase, amplitude and temporal pulse profile for each iteration of the algorithm using SPIDER shows that we are able to lock the spectral phase of the laser pulse within a narrow margin. By using the second harmonic of the CPA laser as feedback for the genetic algorithm, it has been demonstrated that severe mismatch between the compressor and stretcher can be compensated for in a short period of time.

  1. High-power PPMgLN-based optical parametric oscillator pumped by a linearly polarized, semi-fiber-coupled acousto-optic Q-switched fiber master oscillator power amplifier.

    PubMed

    Chen, Tao; Jiang, Peipei; Yang, Dingzhong; Hu, Chengzhi; Wu, Bo; Shen, Yonghang

    2013-09-01

    We have experimentally demonstrated a periodically poled magnesium-oxide-doped lithium niobate (PPMgLN)-based, fiber-laser-pumped optical parametric oscillator (OPO) generating idler wavelength of 3.82 μm. The pump fiber laser was constructed with a linearly polarized, semi-fiber-coupled acousto-optic Q-switched fiber oscillator and a polarization-maintaining fiber amplifier with pulse duration of 190 ns at the highest output power. The OPO was specifically configured in single-pass, singly resonant linear cavity structure to avoid the damage risk of the pump fiber laser, which is always a serious issue in the fiber-laser-pumped, double-pass, singly oscillating structured OPOs. Under the highest pump power of 25 W, an idler average output power of 3.27 W with one-hour peak-to-peak instability of 5.2% was obtained. The measured M2 factors were 1.98 and 1.44 for horizontal and vertical axis, respectively. The high power stability and good beam quality demonstrated the suitability of such technology for practical application.

  2. Tunable Microwave Transversal Filters and Dispersive Delay Lines Based on Oblique Incidence Reflection of Magnetostatic Wave Propagating in Epitaxial Garnets.

    DTIC Science & Technology

    1986-09-30

    based on Epitaxial Ferrites . This final report summarizes the results of viable realizations of these goals. Transversal filters at microwave ...DISPLACEMENT IN DIELECTRIC IMAGE GUIDES At microwave or millimeter wave frequency range, ferrite materials play important roles in the design of...isolators utilizing epitaxial YIG on gadolinium Gallium Garnet at 90-100GHz. These experiments have shown that the concept is feasible but that ferrite

  3. Extraction of orientation-and-scale-dependent information from GPR B-scans with tunable two-dimensional wavelet filters

    NASA Astrophysics Data System (ADS)

    Tzanis, A.

    2012-04-01

    GPR is an invaluable tool for civil and geotechnical engineering applications. One of the most significant objectives of such applications is the detection of fractures, inclined interfaces, empty or filled cavities frequently associated with jointing/faulting and a host of other oriented features. These types of target, especially fractures, are usually not good reflectors and are spatially localized. Their scale is therefore a factor significantly affecting their detectability. Quite frequently, systemic or extraneous noise, or other significant structural characteristics swamp the data with information which blurs, or even masks reflections from such targets, rendering their recognition difficult. This paper reports a method of extracting information (isolating) oriented and scale-dependent structural characteristics, based on oriented two-dimensional B-spline wavelet filters and Gabor wavelet filters. In addition to their advantageous properties (e.g. compact support, orthogonality etc), B-spline wavelets comprise a family with a broad spectrum of frequency localization properties and frequency responses that mimic, more or less, the shape of the radar source wavelet. For instance, the Ricker wavelet is also approximated by derivatives of Cardinal B-splines. An oriented two-dimensional B-spline filter is built by sidewise arranging a number of identical one-dimensional wavelets to create a matrix, tapering the edge-parallel direction with an orthogonal window function and rotating the resulting matrix to the desired orientation. The length of the one-dimensional wavelet (edge-normal direction) determines the width of the topographic features to be isolated. The number of parallel wavelets (edge-parallel direction) determines the feature length over which to smooth. The Gabor wavelets were produced by a Gabor kernel that is a product of an elliptical Gaussian and a complex plane wave: it is two-dimensional by definition. Their applications have hitherto focused

  4. Tunable filter-based multispectral imaging for detection of blood stains on construction material substrates. Part 1. Developing blood stain discrimination criteria.

    PubMed

    Janchaysang, Suwatwong; Sumriddetchkajorn, Sarun; Buranasiri, Prathan

    2012-10-10

    In this article, we establish blood stain detection criteria that are less substrate dependent for use in a liquid crystal tunable filter-based multispectral-imaging system. Kubelka-Munk (KM) theory is applied to transform the acquired stains' reflectance spectra into the less substrate dependent spectra. Chosen spectral parameters are extracted from the KM absorbance spectra of several stain samples on several substrates. Blood discrimination criteria based upon those spectral parameters are then established from empirical data, tested, and refined. In our newly invented method, instead of introducing conventional contrast enhancement on the blood stain image, blood stain determination is executed mathematically via Boolean logic, resulting in more discriminative blood stain identification. This proposed approach allows for nondestructive, quick, discriminative, and easy-to-improve presumptive blood stain detection. Experimental results confirm that our blood stain discrimination criteria can be used to locate blood stains on several construction materials with high precision. True positive rates (sensitivity) from 0.60 to 0.95 are achieved depending on blood stain faintness and substrate types. Also, true negative rates (specificity) between 0.55 and 0.96 and identification time of 4-5 min are accomplished, respectively. The established blood stain discrimination criteria will be incorporated in a real blood stain detection system in part 2 of this article, where system design and considerations as well as speed issues are discussed.

  5. Hyperspectral microscope imaging methods to classify gram-positive and gram-negative foodborne pathogenic bacteria

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An acousto-optic tunable filter-based hyperspectral microscope imaging method has potential for identification of foodborne pathogenic bacteria from microcolony rapidly with a single cell level. We have successfully developed the method to acquire quality hyperspectral microscopic images from variou...

  6. The potential for early and rapid pathogen detection within poultry processing through hyperspectral microscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The acquisition of hyperspectral microscopic images containing both spatial and spectral data has shown potential for the early and rapid optical classification of foodborne pathogens. A hyperspectral microscope with a metal halide light source and acousto-optical tunable filter (AOTF) collects 89 ...

  7. High power, tunable mid-infrared BaGa4Se7 optical parametric oscillator pumped by a 2.1 μm Ho:YAG laser.

    PubMed

    Yuan, Jin-He; Li, Chao; Yao, Bao-Quan; Yao, Ji-Yong; Duan, Xiao-Ming; Li, Ying-Yi; Shen, Ying-Jie; Wu, Yi-Cheng; Cui, Zheng; Dai, Tong-Yu

    2016-03-21

    We, for the first time, demonstrate a tunable mid-infrared BaGa4Se7-based optical parametric oscillator pumped by a acousto-optical Q-switched Ho:YAG laser at 2090.6 nm. Up to 1.55 W of average power was generated in the 3-5 μm range, corresponding to an optical-to-optical conversion efficiency of 14.4% and a slope efficiency of 19.9%. The mid-IR radiation spectra were also seriously researched at different phase-matched angles. The tunable range was 3.49-4.13 μm for the signal, and 5.19-4.34 μm for the idler.

  8. Micro-Mechanical Voltage Tunable Fabry-Perot Filters Formed in (111) Silicon. Degree awarded by Colorado Univ., Boulder, CO

    NASA Technical Reports Server (NTRS)

    Patterson, James D.

    1997-01-01

    The MEMS (Micro-Electro-Mechanical-Systems) technology is quickly evolving as a viable means to combine micro-mechanical and micro-optical elements on the same chip. One MEMS technology that has recently gained attention by the research community is the micro-mechanical Fabry-Perot optical filter. A MEMS based Fabry-Perot consists of a vertically integrated structure composed of two mirrors separated by an air gap. Wavelength tuning is achieved by applying a bias between the two mirrors resulting in an attractive electrostatic force which pulls the mirrors closer. In this work, we present a new micro-mechanical Fabry-Perot structure which is simple to fabricate and is integratable with low cost silicon photodetectors and transistors. The structure consists of a movable gold coated oxide cantilever for the top mirror and a stationary Au/Ni plated silicon bottom mirror. The fabrication process is single mask level, self aligned, and requires only one grown or deposited layer. Undercutting of the oxide cantilever is carried out by a combination of RIE and anisotropic KOH etching of the (111) silicon substrate. Metallization of the mirrors is provided by thermal evaporation and electroplating. The optical and electrical characteristics of the fabricated devices were studied and show promissing results. A wavelength shift of 120nm with 53V applied bias was demonstrated by one device geometry using 6.27 micrometer air gap. The finesse of the structure was 2.4. Modulation bandwidths ranging from 91KHz to greater than 920KHz were also observed. Theoretical calculations show that if mirror reflectivity, smoothness, and parallelism are improved, a finesse of 30 is attainable. The predictions also suggest that a reduction of the air gap to 1 micrometer results in an increased wavelength tuning range of 175 nm with a CMOS compatible 4.75V.

  9. Widely tunable erbium-doped fiber laser based on multimode interference effect.

    PubMed

    Castillo-Guzman, A; Antonio-Lopez, J E; Selvas-Aguilar, R; May-Arrioja, D A; Estudillo-Ayala, J; LiKamWa, P

    2010-01-18

    A widely tunable erbium-doped all-fiber laser has been demonstrated. The tunable mechanism is based on a novel tunable filter using multimode interference effects (MMI). The tunable MMI filter was applied to fabricate a tunable erbium-doped fiber laser via a standard ring cavity. A tuning range of 60 nm was obtained, ranging from 1549 nm to 1609 nm, with a signal to noise ratio of 40 dB. The tunable MMI filter mechanism is very simple and inexpensive, but also quite efficient as a wavelength tunable filter.

  10. Plasmonic filters.

    SciTech Connect

    Passmore, Brandon Scott; Shaner, Eric Arthur; Barrick, Todd A.

    2009-09-01

    Metal films perforated with subwavelength hole arrays have been show to demonstrate an effect known as Extraordinary Transmission (EOT). In EOT devices, optical transmission passbands arise that can have up to 90% transmission and a bandwidth that is only a few percent of the designed center wavelength. By placing a tunable dielectric in proximity to the EOT mesh, one can tune the center frequency of the passband. We have demonstrated over 1 micron of passive tuning in structures designed for an 11 micron center wavelength. If a suitable midwave (3-5 micron) tunable dielectric (perhaps BaTiO{sub 3}) were integrated with an EOT mesh designed for midwave operation, it is possible that a fast, voltage tunable, low temperature filter solution could be demonstrated with a several hundred nanometer passband. Such an element could, for example, replace certain components in a filter wheel solution.

  11. Depth selective acousto-optic flow measurement

    PubMed Central

    Tsalach, Adi; Schiffer, Zeev; Ratner, Eliahu; Breskin, Ilan; Zeitak, Reuven; Shechter, Revital; Balberg, Michal

    2015-01-01

    Optical based methods for non-invasive measurement of regional blood flow tend to incorrectly assess cerebral blood flow, due to contribution of extra-cerebral tissues to the obtained signal. We demonstrate that spectral analysis of phase-coded light signals, tagged by specific ultrasound patterns, enables differentiation of flow patterns at different depths. Validation of the model is conducted by Monte Carlo simulation. In-vitro experiments demonstrate good agreement with the simulations' results and provide a solid validation to depth discrimination ability. These results suggest that signal contamination originating from extra-cerebral tissue may be eliminated using spectral analysis of ultrasonically tagged light. PMID:26713201

  12. Multiple acousto-optic q-switch

    DOEpatents

    Deason, Vance A.

    1993-01-01

    An improved dynamic moire interferometer comprised of a lasing medium providing a plurality of beams of coherent light, a multiple q-switch producing multiple trains of 100,000 or more pulses per second, a combining means collimating multiple trains of pulses into substantially a single train and directing beams to specimen gratings affixed to a test material, and a controller, triggering and sequencing the emission of the pulses with the occurrence and recording of a dynamic loading event.

  13. Multiple acousto-optic q-switch

    DOEpatents

    Deason, Vance A.

    1993-12-07

    An improved dynamic moire interferometer comprised of a lasing medium providing a plurality of beams of coherent light, a multiple q-switch producing multiple trains of 100,000 or more pulses per second, a combining means collimating multiple trains of pulses into substantially a single train and directing beams to specimen gratings affixed to a test material, and a controller, triggering and sequencing the emission of the pulses with the occurrence and recording of a dynamic loading event.

  14. Applications of Optical Coherent Transient Technology to Pulse Shaping, Spectral Filtering, Arbitrary Waveform Generation and RF Beamforming

    DTIC Science & Technology

    2006-04-15

    optical pulses: (1) using acousto - optic modulators (AOMs) driven with a chirped RF source, ( 2 ) using EOPMs driven with a chirped RF source, (3) utilizing a...holograms (SSH) have the potential to duplicate the functional operation of acousto - optic (AO) deflectors , but with bandwidths (BW) in excess of 10 GHz... acousto - optic deflector to create a scanned optical signal that was recorded in an OCT crystal. The scanner functionality of the AOD was thus

  15. Narrowing of the linewidth of an optical parametric oscillator by an acousto-optic modulator for the realization of mid-IR noise-immune cavity-enhanced optical heterodyne molecular spectrometry down to 10⁻¹⁰ cm⁻¹ Hz⁻¹/².

    PubMed

    Hausmaninger, Thomas; Silander, Isak; Axner, Ove

    2015-12-28

    The linewidth of a singly resonant optical parametric oscillator (OPO) has been narrowed with respect to an external cavity by the use of an acousto-optic modulator (AOM). This made possible an improvement of the sensitivity of a previously realized OPO-based noise-immune cavity-enhanced optical heterodyne molecular spectrometry instrument for the 3.2 - 3.9 µm mid-infrared region by one order of magnitude. The resulting system shows a detection sensitivity for methane of 2.4 × 10(-10) cm(-1) Hz(-1∕2) and 1.3 × 10(-10) cm(-1) at 20 s, which allows for detection of both the environmentally important (13)CH(4) and CH(3)D isotopologues in atmospheric samples.

  16. A tunable, single frequency, fiber ring at 1053 nm

    SciTech Connect

    Wilcox, R.B.

    1997-02-21

    This laser is a tunable source designed for applications where a shorter pulse will be chopped from a long Q-switched pulse by electrooptic modulators, then amplified in Nd:phosphate glass. The laser employs ytterbium-doped silica fiber as the gain medium, pumped by a laser diode at 980nm. Gain in Yb:silica is distributed over an 90nm range, making it suitable for operation at many wavelengths. Our previous experiments with this medium demonstrated oscillation over a 50nm wide band. In addition, pumping at 980nm allows the use of stable pump diodes used in erbium-doped fiber amplifiers (EDFA`s). We designed the laser to take advantage of this wideband gain medium, and yet operate on a single cavity mode. A circulator causes unidirectional operation, and allows use of a fiber grating in reflection. This grating has a 0.2 Angstrom bandwidth, and defines the coarse tuning of the laser. It is piezoelectrically stretch tuned to the desired wavelength band. A single mode of the cavity is selected by a piezoelectrically tuned fiber grating Fabry-Perot etalon with 64MHz bandwidth. The laser is Q-switched by a bulk acousto-optic device at lkhz reprate. The loss is controlled to allow the oscillator to lase close to threshold for 500{micro}s before the Q-switch is turned off completely, creating a pulse. This ``pre-lasing`` stabilizes the single mode, since Q-switch pulse builds up from the prelase level. To prevent mode hopping during long term operation, cavity length is feedback controlled. Another piezoelectric device stretches a fiber in the cavity according to an error signal derived from the output optical signal. Due to the long, high loss cavity, the Q-switched pulse is about 3OOns long. The central part of this pulse will be gated by an electrooptic modulator to produce a 30ns square pulse, used for further amplification and modulation.

  17. The Development and Implementation of an Optical Communications Laboratory.

    DTIC Science & Technology

    1984-12-01

    102 VII- 2 . Acousto - Optic Interaction in the Bragg Regime ...... ................ 104 VII-3. Bragg Diffraction Sound Cell Used as Spectrum Analyzer...I. Bragg Cell with Plane Wave Illumination . . 124 VIII- 2 . Bragg Diffraction of an Acousto - Optic Cell . 127 VIII-3. Illustration of an Acousto - Optic ...Diffraction with lenses. 2 3. Imaging and Spatial Filtering. 4. Measurement of the Bragg Angle of an Acousto - Optic Modulator (Bragg Cell). 5. Beam

  18. Elastomer based electrically tunable, optical microcavities

    NASA Astrophysics Data System (ADS)

    Slowik, Irma; Kronenberg, Nils M.; Franke, Markus; Fischer, Axel; Richter, Andreas; Gather, Malte C.; Leo, Karl

    2016-10-01

    Tunable optical elements are mostly realized by microelectromechanical systems, which require expensive and complex lithography during processing. We demonstrate an alternative device based on an electrically tunable microcavity employing a dielectric soft elastomer actuator. The cavity resonance is varied by changing the physical cavity thickness due to electrostriction of the soft elastomer. We realize a tunable metal-elastomer-distributed Bragg reflector multi-half wavelength microcavity with a cavity layer thickness around 12 μm and quality factors up to 700. Applying a voltage up to 60 V between bottom ITO and top metal electrode tunes the wavelength of the cavity modes up to Δ λ = 14 nm, which relates to a cavity thickness change of about 200 nm. This concept allows the implementation of tunable optical elements like tunable filters or resonators with low cost and simple processing.

  19. Semiconductor lasers with a continuous tuning range above 100 nm in the nearest IR spectral region

    SciTech Connect

    Kostin, Yu O; Lobintsov, A A; Shramenko, M V; Ladugin, M A; Marmalyuk, A A; Chamorovsky, A Yu; Yakubovich, S D

    2015-08-31

    We have developed two new types of lasers based on quantum-confined semiconductor optical amplifiers with an acousto-optic tunable filter in an external fibre ring cavity. The lasers offer continuous wavelength tuning ranges from 780 to 885 and from 880 to 1010 nm, 20 mW of cw output power, and a tuning rate up to 10{sup 4} nm s{sup -1} at an instantaneous spectral linewidth less than 0.1 nm. (lasers)

  20. Demonstration AOTF Imaging Spectrometer

    NASA Technical Reports Server (NTRS)

    Chao, Tien-Hsin; Yu, Jeffrey; Cheng, Li-Jen

    1993-01-01

    Spectral images of high quality obtained. Acousto-optical-tunable-filter (AOTF) imaging spectrometer is optical system in which AOTF serves as spectrally dispersive element causing image on final focal plane to be shifted on plane by distance depending on wavelength of light emanating from scene. Useful in several applications involving identification, via characteristic spectras, of substances in observed scenes: examples include prospecting for minerals and detecting chemical pollutants.

  1. Tetravalent chromium (Cr(4+)) as laser-active ion for tunable solid-state lasers

    NASA Technical Reports Server (NTRS)

    Seas, A.; Petricevic, V.; Alfano, Robert R.

    1993-01-01

    Major accomplishments under NASA grant NAG-1-1346 are summarized. (1) numerical modeling of the four mirror astigmatically compensated, Z-fold cavity was performed and several design parameters to be used for the construction of a femtosecond forsterite laser were revealed by simulation. (2) femtosecond pulses from a continuous wave mode-locked chromium doped forsterite laser were generated. The forsterite laser was actively mode-locked using an acousto-optic modulator operating at 78 MHz with two Brewster high dispersion glass prisms for intra-cavity chirp compensation. Transform-limited sub-100-fs pulses were routinely generated in the TEM(sub 00) mode with 85 mW of continuous power tunable over 1230-1280 nm. The shortest pulses of 60-fs pulsewidth were measured. (3) Self-mode-locked operation of the Cr:forsterite laser was achieved. Synchronous pumping was used to mode lock the forsterite laser resulting in picosecond pulses, which in turn provided the starting mechanism for self-mode-locking. The pulses generated had an FWHM of 105 fs and were tunable between 1230-1270 nm. (4) Numerical calculations indicated that the pair of SF 14 prisms used in the cavity compensated for quadratic phase but introduced a large cubic phase term. Further calculations of other optical glasses indicated that a pair of SFN 64 prisms can introduce the same amount of quadratic phase as SF 14 prisms but introduce a smaller cubic phase. When the SF 14 prisms were replaced by SFN 64 prisms the pulsewidth was reduced to 50 fs. Great improvement was observed in the stability of the self mode-locked forsterite laser and in the ease of achieving mode locking. Using the same experimental arrangement and a new forsterite crystal with improved FOM the pulse width was reduced to 36 fs.

  2. Fine-Tunable Absorption of Uniformly Aligned Polyurea Thin Films for Optical Filters Using Sequentially Self-Limited Molecular Layer Deposition.

    PubMed

    Park, Yi-Seul; Choi, Sung-Eun; Kim, Hyein; Lee, Jin Seok

    2016-05-11

    Development of methods enabling the preparation of uniformly aligned polymer thin films at the molecular level is a prerequisite for realizing their optoelectronic characteristics as innovative materials; however, these methods often involve a compromise between scalability and accuracy. In this study, we have grown uniformly aligned polyurea thin films on a SiO2 substrate using molecular layer deposition (MLD) based on sequential and self-limiting surface reactions. By integrating plane-polarized Fourier-transform infrared, Raman spectroscopic tools, and density functional theory calculations, we demonstrated the uniform alignment of polyurea MLD films. Furthermore, the selective-wavelength absorption characteristics of thickness-controlled MLD films were investigated by integrating optical measurements and finite-difference time-domain simulations of reflection spectra, resulting from their thickness-dependent fine resonance with photons, which could be used as color filters in optoelectronics.

  3. Peak power tunable mid-infrared oscillator pumped by a high power picosecond pulsed fiber amplifier with bunch output

    NASA Astrophysics Data System (ADS)

    Wei, Kaihua; Guo, Yan; Lai, Xiaomin; Fan, Shanhui

    2016-07-01

    A high power mid-infrared optical parametric oscillator (OPO) with picosecond pulse bunch output is experimentally demonstrated. The pump source was a high power master oscillation power amplifier (MOPA) picosecond pulsed fiber amplifier. The seed of the MOPA was a gain-switched distributed Bragg reflector (DBR) laser diode (LD) with picosecond pulse operation at a high repetition rate. The seed laser was amplified to 50 W by two-stage pre-amplifiers and a large mode area (LMA) Yb fiber based power-amplifier. A fiber-pigtailed acousto-optic modulator with the first order diffraction transmission was inserted into the second pre-amplifier to form a picosecond pulse bunch train and to change the peak power simultaneously. The power-amplified pulse bunches were focused to pump a wavelength-tunable OPO for emitting high power mid-infrared laser. By adjusting the OPO cavity length, the maximum average idler powers obtained at 3.1, 3.3 and 3.5 μm were 7, 6.6 and 6.4 W respectively.

  4. Proposal of Tunable Hollow Waveguide Distributed Bragg Reflectors

    NASA Astrophysics Data System (ADS)

    Sakurai, Yasuki; Koyama, Fumio

    2004-05-01

    We propose a novel tunable distributed Bragg reflector (DBR) consisting of a grating loaded slab hollow waveguide with a variable air core. A change in an air core thickness of the tunable hollow waveguide gives us a large shift of over 100 nm in Bragg wavelength due to a change of several percents in a propagation constant. In order to obtain the high reflectivity and wide tunability of the tunable hollow waveguide DBR, the optimisation of the grating depth and grating length is carried out with minimizing radiation loss and distortion of reflection spectra induced by the corrugation. The modelling result shows a possibility of wide tunability of several tens nm with maintaining a high reflectivity of more than 90% without noticeable radiation loss and distortion of reflection spectra. We expect various device applications of the proposed tunable hollow waveguide DBR, which may include tunable band-pass filters, gain equalizers and dispersion compensators.

  5. Electrically tunable materials for microwave applications

    SciTech Connect

    Ahmed, Aftab Goldthorpe, Irene A.; Khandani, Amir K.

    2015-03-15

    Microwave devices based on tunable materials are of vigorous current interest. Typical applications include phase shifters, antenna beam steering, filters, voltage controlled oscillators, matching networks, and tunable power splitters. The objective of this review is to assist in the material selection process for various applications in the microwave regime considering response time, required level of tunability, operating temperature, and loss tangent. The performance of a variety of material types are compared, including ferroelectric ceramics, polymers, and liquid crystals. Particular attention is given to ferroelectric materials as they are the most promising candidates when response time, dielectric loss, and tunability are important. However, polymers and liquid crystals are emerging as potential candidates for a number of new applications, offering mechanical flexibility, lower weight, and lower tuning voltages.

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

    SciTech Connect

    Kita, Tomohiro 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.

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

    NASA Astrophysics Data System (ADS)

    Kita, Tomohiro; Tang, Rui; Yamada, Hirohito

    2015-03-01

    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.

  8. Solc filter engineering

    NASA Technical Reports Server (NTRS)

    Rosenberg, W. J.; Title, A. M.

    1982-01-01

    A Solc (1965) filter configuration is presented which is both tunable and spectrally variable, since it possesses an adjustable bandwidth, and which although less efficient than a Lyot filter is attractive because of its spectral versatility. The lossless design, using only an entrance and exit polarizer, improves throughput generally and especially in the IR, where polarizers are less convenient than dichroic sheet polarizers. Attention is given to the transmission profiles of Solc filters with different numbers of elements and split elements, as well as their mechanical design features.

  9. Underwater tunable organ-pipe sound source.

    PubMed

    Morozov, Andrey K; Webb, Douglas C

    2007-08-01

    A highly efficient frequency-controlled sound source based on a tunable high-Q underwater acoustic resonator is described. The required spectrum width was achieved by transmitting a linear frequency-modulated signal and simultaneously tuning the resonance frequency, keeping the sound source in resonance at the instantaneous frequency of the signal transmitted. Such sound sources have applications in ocean-acoustic tomography and deep-penetration seismic tomography. Mathematical analysis and numerical simulation show the Helmholtz resonator's ability for instant resonant frequency switching and quick adjustment of its resonant frequency to the instantaneous frequency signal. The concept of a quick frequency adjustment filter is considered. The discussion includes the simplest lumped resonant source as well as the complicated distributed system of a tunable organ pipe. A numerical model of the tunable organ pipe is shown to have a form similar to a transmission line segment. This provides a general form for the principal results, which can be applied to tunable resonators of a different physical nature. The numerical simulation shows that the "state-switched" concept also works in the high-Q tunable organ pipe, and the speed of frequency sweeping in a high-Q tunable organ pipe is analyzed. The simulation results were applied to a projector design for ocean-acoustic tomography.

  10. Hybrid Micro-Electro-Mechanical Tunable Filter

    DTIC Science & Technology

    2007-09-01

    Turn on (button switches to ’off’): Gas (fast rise), Skip Purge , Helium (if necessary, click up/down arrow to converge), Pressure, Magnets (dummy...inconclusive, multi-layer stripe etch study results: 30-min citric-acid/tripotassium-citrate/ hydrogen -peroxide etch at 25 ◦C, stripe oriented parallel to ...tripotassium- citrate/ hydrogen -peroxide etch at 25 ◦C, deep and irregular anisotropic etching of the GaAs substrate was observed as indi- cated on left side

  11. Tunable Optical Polymer Systems

    DTIC Science & Technology

    2007-11-02

    Background and MURI Program Objectives Chromogenic phenomena (for example: electrochromism, photochromism , thermochromism, piezochromism, and...achieving real time tunability of optical properties of materials. Photochromism and electrochromism in polymeric and organic materials have been...chromogenic phenomena, especially electrochromism, photochromism , photoelectrochromism, thermochromism, tunable luminescence, and tunable reflection, in

  12. Tunable Terahertz Hybrid Metal-Graphene Plasmons.

    PubMed

    Jadidi, Mohammad M; Sushkov, Andrei B; Myers-Ward, Rachael L; Boyd, Anthony K; Daniels, Kevin M; Gaskill, D Kurt; Fuhrer, Michael S; Drew, H Dennis; Murphy, Thomas E

    2015-10-14

    We report here a new type of plasmon resonance that occurs when graphene is connected to a metal. These new plasmon modes offer the potential to incorporate a tunable plasmonic channel into a device with electrical contacts, a critical step toward practical graphene terahertz optoelectronics. Through theory and experiments, we demonstrate, for example, anomalously high resonant absorption or transmission when subwavelength graphene-filled apertures are introduced into an otherwise conductive layer. These tunable plasmon resonances are essential yet missing ingredients needed for terahertz filters, oscillators, detectors, and modulators.

  13. The Stark anomalous dispersion optical filter: The theory

    NASA Technical Reports Server (NTRS)

    Yin, B.; Shay, T. M.

    1994-01-01

    The Stark anomalous dispersion optical filter is a wide-frequency-tunable ultra-narrow-bandwidth optical filter. The first theoretical investigation of this filter matched to the wavelength of a doubled Nd:YAG laser is reported. The calculations show that such a filter may provide above 80 percent transmission, and a noise equivalent bandwidth of 3 GHz.

  14. Preconditioning of real-time optical Wiener filters for array processing

    NASA Astrophysics Data System (ADS)

    Ghosh, Anjan; Paparao, Palacharla

    1992-07-01

    In adaptive array processors, a performance measure, such as mean square error or signal to noise ration, coverages to the optimum Wiener solution starting from an initial setting. The choice of adaptive algorithms to solve the Wiener filtering problem is mainly guided by the desired processing time. In an optical realization for direct calculation of the optimum weights the covariance matrix and vector for a Wiener filter are computed at a high speed on acousto-optic processors. The resulting linear system of equations can be solved on an iterative optical processor. The matrix and vector data should be recomputed in every iteration for better tracking and adaptation. This introduces variations in their values due to the time-varying jamming and interference noise and the optical errors and noise. Time variant steepest descent algorithm is a simple method that converges to the common solution. In this paper, we describe a real-time preconditioning technique for such nonstationary iterative methods. Preconditioning will progressively lower the condition number of each matrix in the sequence, thereby improving the convergence speed and accuracy of the solution. This preconditioning process involves matrix-matrix multiplications that can be performed at high speed on parallel optical processors. Results of simulations illustrate the superlinear convergence obtained from preconditioning.

  15. Tunable C- and L-band laser source based on colorless laser diode

    NASA Astrophysics Data System (ADS)

    Peng, P. C.; Jhang, J. J.; Peng, Y. W.; Bitew, M. A.; Chi, Y. C.; Wu, W. C.; Wang, H. Y.; Lin, G. R.; Li, C. Y.; Lu, H. H.

    2017-03-01

    In this letter, we propose and demonstrate a tunable laser source which covers C- and L-bands based on a colorless laser diode. The proposed laser source is tunable widely and it can tune single-wavelength, dual-wavelength, and triple-wavelength. Additionally, the optical side mode suppression ratio exceeds 30 dB. Since we combine the colorless laser diode with a tunable optical filter, the proposed tunable laser source stabilizes multi-wavelengths simultaneously. Our proposed tunable laser source is very useful for applications such as optical test instruments, optical communication systems, and optical fiber sensing systems.

  16. Accurate band-to-band registration of AOTF imaging spectrometer using motion detection technology

    NASA Astrophysics Data System (ADS)

    Zhou, Pengwei; Zhao, Huijie; Jin, Shangzhong; Li, Ningchuan

    2016-05-01

    This paper concerns the problem of platform vibration induced band-to-band misregistration with acousto-optic imaging spectrometer in spaceborne application. Registrating images of different bands formed at different time or different position is difficult, especially for hyperspectral images form acousto-optic tunable filter (AOTF) imaging spectrometer. In this study, a motion detection method is presented using the polychromatic undiffracted beam of AOTF. The factors affecting motion detect accuracy are analyzed theoretically, and calculations show that optical distortion is an easily overlooked factor to achieve accurate band-to-band registration. Hence, a reflective dual-path optical system has been proposed for the first time, with reduction of distortion and chromatic aberration, indicating the potential of higher registration accuracy. Consequently, a spectra restoration experiment using additional motion detect channel is presented for the first time, which shows the accurate spectral image registration capability of this technique.

  17. 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.

  18. Perovskite Superlattices as Tunable Microwave Devices

    NASA Technical Reports Server (NTRS)

    Christen, H. M.; Harshavardhan, K. S.

    2003-01-01

    Experiments have shown that superlattices that comprise alternating epitaxial layers of dissimilar paraelectric perovskites can exhibit large changes in permittivity with the application of electric fields. The superlattices are potentially useful as electrically tunable dielectric components of such microwave devices as filters and phase shifters. The present superlattice approach differs fundamentally from the prior use of homogeneous, isotropic mixtures of base materials and dopants. A superlattice can comprise layers of two or more perovskites in any suitable sequence (e.g., ABAB..., ABCDABCD..., ABACABACA...). Even though a single layer of one of the perovskites by itself is not tunable, the compositions and sequence of the layers can be chosen so that (1) the superlattice exhibits low microwave loss and (2) the interfacial interaction between at least two of the perovskites in the superlattice renders either the entire superlattice or else at least one of the perovskites tunable.

  19. The Lockheed alternate partial polarizer universal filter

    NASA Technical Reports Server (NTRS)

    Title, A. M.

    1976-01-01

    A tunable birefringent filter using an alternate partial polarizer design has been built. The filter has a transmission of 38% in polarized light. Its full width at half maximum is .09A at 5500A. It is tunable from 4500 to 8500A by means of stepping motor actuated rotating half wave plates and polarizers. Wave length commands and thermal compensation commands are generated by a PPD 11/10 minicomputer. The alternate partial polarizer universal filter is compared with the universal birefringent filter and the design techniques, construction methods, and filter performance are discussed in some detail. Based on the experience of this filter some conclusions regarding the future of birefringent filters are elaborated.

  20. Applications of Optical Coherent Transient Technology to Pulse Shaping, Spectral Filtering Arbitrary Waveform Generation and RF Beamforming

    DTIC Science & Technology

    2006-04-14

    for creating fast (~MHz/µs) linear frequency chirped optical pulses: (1) using acousto - optic modulators (AOMs) driven with a chirped RF source, ( 2 ...the cavity. The frequencies allowed in a Fabry–Perot cavity are: where =1,2,... and optical path length of cavity 2 qcv q d d = = (29) The...the functional operation of acousto - optic (AO) deflectors , but with bandwidths (BW) in excess of 10 GHz and Time-Bandwidth Prod- ucts (TB) over 103 by