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Sample records for acousto-optic tunable filters

  1. Imaging spectrometer based on a acousto-optic tunable filter

    SciTech Connect

    Beattie, M.E.; Harrison, D.C.

    1994-12-31

    Characterization of an Acousto-Optic Tunable Filter (AOTF) is performed by measuring the filter`s laser line response, tuning relationship, and diffraction efficiency. An imaging spectrometer that utilizes the filter is described. The system is comprised of an optical system, AOTF filter, dual focal plane CCD camera, and a control computer. Data from the system are presented.

  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 as a notch filter

    NASA Astrophysics Data System (ADS)

    Gupta, Neelam

    2016-05-01

    An acousto-optic tunable filter (AOTF) is an all solid-state robust device with no-moving parts that has been used in the development of hyperspectral imagers from the ultraviolet to the longwave infrared. Such a device is developed by bonding a piezoelectric transducer on a specially cut prism in a birefringent crystal. When broadband white light is incident on the prism input facet, two orthogonally polarized diffracted beams at a wavelength with a narrowband bandpass are transmitted. The transmitted wavelength can be tuned by varying the applied radio frequency (RF). This is what is done in a hyperspectral imager. An AOTF can also be used with multiple RFs applied at the same time to diffract a number of different wavelengths. This mode can be exploited to design a tunable optical notch filter where multiple RFs are applied simultaneously such that all wavelength in a specific range can transmit except for a specific wavelength which is notched. We designed an optical system using a TeO2 AOTF with telecentric confocal optics operating in the shortwave infrared (SWIR) with a 16-channel RF driver where both the amplitude and frequency can be controlled independently for each channel. We will discuss the optical system, its characterization and present results obtained.

  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. Tunable acousto-optic filters with the multiple interaction of light and sound

    SciTech Connect

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

    2005-11-30

    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. (control of laser radiation parameters)

  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. 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.

  8. Monolithic bulk shear-wave acousto-optic tunable filter.

    PubMed

    Gnewuch, Harald; Pannell, Christopher N

    2002-12-01

    We demonstrate a monolithic bulk shear-wave acousto-optic tunable filter combining a piezoelectric transducer array and the acoustic interaction medium in a single crystal. An X-propagating acoustic longitudinal wave is excited in the "crossed-field" scheme by an rf-Ey-field in a chirped acoustic superlattice formed by domain-inversion in lithium niobate (LiNbO3). The acoustic longitudinal wave is efficiently (97.5%) converted at a mechanically free boundary into a Y-propagating acoustic slow-shear wave that couples collinearly propagating e- and o-polarized optical waves. A relative conversion efficiency of 80%/W was measured at 980 nm. PMID:12546145

  9. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  11. Fast scanning synchronous luminescence spectrometer based on acousto-optic tunable filters

    SciTech Connect

    Hueber, D.M.; Stevenson, C.L.; Vo-Dinh, T.

    1995-11-01

    A new luminescence spectrometer based on quartz-collinear acousto-optic tunable filters (AOTFs) and capable of synchronous scanning is described. An acousto-optic tunable filter is an electronically tunable optical bandpass filter. Unlike a tunable grating monochromator, an AOTF has no moving mechanical parts, and an AOTF can be tuned to any wavelength within its operating range in microseconds. These characteristics, combined with the small size of these devices, make AOTFs an important new alternative to conventional monochromators, especially for portable instrumentation. The relevant performance of the AOTFs (efficiency, bandwidth, rejection, etc.) is compared with that of typical small-grating monochromator. {copyright} {ital 1995 Society for Applied Spectroscopy.}

  12. 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.

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

    PubMed

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

    2015-09-21

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

  14. Investigations of spread function of the optical spectral device based on acousto-optic tunable filter

    NASA Astrophysics Data System (ADS)

    Kazakov, Vasily; Korol, Georgy; Moskaletz, Oleg

    2016-04-01

    The analysis of the spectra of the dynamic signals in optical range by techniques of acousto-optics at light diffraction on a traveling acoustic wave excited by a periodic sequence of radio pulses with a rectangular envelope and linear variation of the instantaneous frequency is considered. The expression of the spread function of the spectral device based on acousto-optical tunable filter that allows to investigate in detail the advantages of this optical spectrometer is obtained. Mathematical modeling of the spread functions for different values of speed of change of the instantaneous control frequency is performed. The results of experimental research are provided.

  15. Spectral imagery with an acousto-optic tunable filter

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  16. 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.

  17. 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.

  18. 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.

  19. Quasi-collinear tunable acousto-optic paratellurite crystal filters for wavelength division multiplexing and optical channel selection

    SciTech Connect

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

    2009-04-30

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

  20. Double pass in acousto-optic tunable filter for telecommunication network

    NASA Astrophysics Data System (ADS)

    Issa, Hadeel; Quintard, Véronique; Pérennou, André; Sakkour, Afif

    2014-07-01

    We investigate an acousto-optic tunable filter setup for wavelength division multiplexing telecommunication applications in wideband C (100 nm around 1550 nm). Anisotropic Bragg diffraction of light in TeO2 bulk crystal is first investigated experimentally and theoretically in a quasi-collinear interaction configuration. Based on those characterizations, we propose a double-pass optical beam which allows us to improve the filter performances in terms of crosstalk and selectivity: the full width at half maximum and the sidelobe level are reduced.

  1. A remote sensor to monitor combustion products using a tunable acousto-optic filter

    SciTech Connect

    Bardash, M.J.

    1989-01-01

    An optical system using a tunable acousto-optic filter to measure the temperature and partial pressures of CO and CO[sub 2] in combustion gases has been designed and operated. The system measures the infrared absorption over a linear path through the combustion products from several lines of the vibration-rotation band of CO at 4.7[mu]m. The temperature and partial pressure of CO is then calculated using these data. The infrared absorption due the asymmetric stretch mode of CO[sub 2] is then measured. The entire system, under computer control, is self calibrating and is well suited for remote process control applications.

  2. Tunable semiconductor laser with an acousto-optic filter in an external fibre cavity

    SciTech Connect

    Andreeva, E V; Mamedov, D S; Ruenkov, A A; Shramenko, M V; Magdich, L N; Yakubovich, S D

    2006-04-30

    A tunable semiconductor laser with a laser amplifier based on a double-pass superluminescent diode as an active element and an acousto-optic filter in an external fibre cavity as a selective element is investigated. A continuous spectral tuning is achieved in a band of width 60 nm centered at a wavelength of 845 nm and the 'instant' linewidth below 0.05 nm is obtained. The sweep frequency within the tuning range achieves 200 Hz. The cw power at the output of a single-mode fibre was automatically maintained constant at the level up to 1.5 mW. (lasers and amplifiers)

  3. Remote spectral imaging system (RSIS) based on an acousto-optic tunable filter (AOTF)

    SciTech Connect

    Moreau, F.; Hueber, D.M.; Vo-Dinh, T.

    1996-12-31

    This paper describes a new remote spectral imaging system (RSIS) based on an acousto-optic tunable filter (AOTF) capable of remote sensing using an imaging fiberoptic probe (IFP). A two-dimensional charge coupled device (CCD) was used as a detector. The AOTF was used as a wavelength selector. Unlike a tunable grating or prism based monochromator, the tunable filter has no moving parts, and it can be rapidly tuned to any wavelength in its operating range. The large aperture of the AOTF and its high spatial resolution allowed the optical image from an IFP to be recorded by a CCD. These characteristics, combined with their small size, make AOTF`s important new alternatives to conventional monochromators, especially for spectral multisensing and imaging. A prototype RSIS system, using both IFP and AOTF, was developed and its feasibility for spectral imaging was demonstrated. 40 refs., 8 figs.

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

    PubMed

    Wang, Pengchong; Zhang, Zhonghua

    2016-05-01

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

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

    PubMed

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

    2014-12-15

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

  6. 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.

  7. Fiber-optic remote multisensor system based on an acousto-optic tunable filter (AOTF)

    SciTech Connect

    Moreau, F.; Moreau, S.M.; Hueber, D.M.; Vo-dinh, T.

    1996-10-01

    This paper describes a new fiber-optic multisensor based on an acousto-optic tunable filter (AOTF) and capable of remote sensing using a multioptical fiber array (MOFA). A two-dimensional charge-coupled device (CCD) was used as a detector, and the AOTF was used as a wavelength selector. Unlike a tunable grating or prism-based monochromator, an AOTF has no moving parts, and an AOTF can be rapidly tuned to any wavelength in its operating range within microseconds. The large aperture of the AOTF allows the optical signal from over 100 fiber-optic sensors to be measured simultaneously. These characteristics, combined with their small size, make AOTFs an important new alternative to conventional monochromators, especially for spectral multisensing and imaging. A prototype fiber-optic multisensor system has been developed, and its feasibility for simultaneous detection of molecular luminescence signal via fiber-optic probes is demonstrated. {copyright} {ital 1996} {ital Society for Applied Spectroscopy}

  8. 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.

  9. Three-surface model for the ray tracing of an imaging acousto-optic tunable filter.

    PubMed

    Zhao, Huijie; Li, Chongchong; Zhang, Ying

    2014-11-10

    A three-surface model is proposed for the ray tracing of an imaging acousto-optic tunable filter (AOTF) in the optical design of an AOTF imaging system. The first and last surfaces are two refractive planes corresponding to the incident and exit facets of the AOTF, while the property of the second surface is defined particularly to describe the change of the ray trace owing to the interaction of the acoustic and optic waves. One parameter, the acoustic angle, is first corrected using the test tuning relation to compensate for the nonideality of the acoustic wave. The model has been verified with a two-piezotransducer AOTF to show its usefulness. The differences between the measured diffracted angles and the modeling value are below 0.01°. The comparison demonstrates the accuracy and the efficiency of the three-surface model.

  10. 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.

  11. 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.

  12. Acousto-Optic Tunable Filter Spectroscopic Instrumentation for Quantitative Near-Ir Analysis of Organic Materials.

    NASA Astrophysics Data System (ADS)

    Eilert, Arnold James

    1995-01-01

    The utility of near-IR spectroscopy for routine quantitative analyses of a wide variety of compositional, chemical, or physical parameters of organic materials is well understood. It can be used for relatively fast and inexpensive non-destructive bulk material analysis before, during, and after processing. It has been demonstrated as being a particularly useful technique for numerous analytical applications in cereal (food and feed) science and industry. Further fulfillment of the potential of near-IR spectroscopic analysis, both in the process and laboratory environment, is reliant upon the development of instrumentation that is capable of meeting the challenges of increasingly difficult applications. One approach to the development of near-IR spectroscopic instrumentation that holds a great deal of promise is acousto-optic tunable filter (AOTF) technology. A combination of attributes offered by AOTF spectrometry, including speed, optical throughput, wavelength reproducibility, ruggedness (no -moving-parts operation) and flexibility, make it particularly desirable for numerous applications. A series of prototype (research model) acousto -optic tunable filter instruments were developed and tested in order to investigate the feasibility of the technology for quantitative near-IR spectrometry. Development included design, component procurement, assembly and/or configuration of the optical and electronic subsystems of which each functional spectrometer arrangement was comprised, as well as computer interfacing and acquisition/control software development. Investigation of this technology involved an evolution of several operational spectrometer systems, each of which offered improvements over its predecessor. Appropriate testing was conducted at various stages of development. Demonstrations of the potential applicability of our AOTF spectrometer to quantitative process monitoring or laboratory analysis of numerous organic substances, including food materials, were

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

    PubMed

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

    2016-07-20

    A broadband supercontinuum light source with an acousto-optic tunable filter (AOTF) are used to characterize dispersion in two time-domain OCT systems, at 850 and 1300 nm. The filter is designed to sweep across two spectral ranges, which are restricted here from 800 to 900 nm and from 1200 to 1500 nm, respectively. Dispersion compensation for 850 nm was achieved with a spectral delay line. Dispersion compensation for 1300 nm was achieved using BK 7 rod glasses in the reference arm. The AOTF allows evaluation of dispersion in under as well as overcompensated systems. The AOTF method is based on wavelength dependence of the optical path difference corresponding to the maximum strength of the interference signal recorded using a mirror as object. Comparison is made between the AOTF method and the more usual method based on measurement of the full width at half-maximum of the autocorrelation peak. This comparison shows that the AOTF method is more accurate in terms of evaluation of the dispersion left uncompensated after each adjustment. The AOTF method additionally provides information on the direction of dispersion compensation. PMID:27463927

  14. Hyper-spectral modulation fluorescent imaging using double acousto-optical tunable filter based on TeO2-crystals

    NASA Astrophysics Data System (ADS)

    Zaytsev, Kirill I.; Perchik, Alexey V.; Chernomyrdin, Nikita V.; Kudrin, Konstantin G.; Reshetov, Igor V.; Yurchenko, Stanislav O.

    2015-01-01

    We have proposed a method for hyper-spectral fluorescent imaging based on acousto-optical filtering. The object of interest was pumped using ultraviolet radiation of mercury lamp equipped with monochromatic excitation filter with the window of transparency centered at 365 nm. Double TeO2-based acousto-optical filter, tunable in range from 430 to 780 nm and having 2 nm bandwidth of spectral transparency, was used in order to detect quasimonochromatic images of object fluorescence. Modulating of ultraviolet pump intensity was used in order to reduce an impact of non-fluorescent background on the sample fluorescent imaging. The technique for signal-to-noise ratio improvement, based on fluorescence intensity estimation via digital processing of modulated video sequence of fluorescent object, was introduced. We have implemented the proposed technique for the test sample studying and we have discussed its possible applications.

  15. 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.

  16. Radiometric calibration and noise estimation of acousto-optic tunable filter hyperspectral imaging systems.

    PubMed

    Katrašnik, Jaka; Pernuš, Franjo; Likar, Boštjan

    2013-05-20

    The accuracy of the radiometric response of acousto-optic tunable filter (AOTF) hyperspectral imaging systems is crucial for obtaining reliable measurements. It is therefore important to know the radiometric response and noise characteristics of the hyperspectral imaging system used. A radiometric model of an AOTF hyperspectral imaging system composed of an imaging sensor radiometric model (CCD, CMOS, and sCMOS) and an AOTF light transmission model is proposed. Using the radiometric model, a method for obtaining the fixed pattern noise (FPN) of the imaging system by displacing and imaging an illuminated reference target is developed. Methods for estimating the temporal noise of the imaging system, using the photon transfer method, and for correcting FPN are also presented. Noise estimation and image restoration methods were tested on an AOTF hyperspectral imaging system. The results indicate that the developed methods can accurately calculate temporal and FPN, and can effectively correct the acquired images. After correction, the signal-to-noise ratio of the acquired images was shown to increase by 26%. PMID:23736239

  17. Radiometric calibration and noise estimation of acousto-optic tunable filter hyperspectral imaging systems.

    PubMed

    Katrašnik, Jaka; Pernuš, Franjo; Likar, Boštjan

    2013-05-20

    The accuracy of the radiometric response of acousto-optic tunable filter (AOTF) hyperspectral imaging systems is crucial for obtaining reliable measurements. It is therefore important to know the radiometric response and noise characteristics of the hyperspectral imaging system used. A radiometric model of an AOTF hyperspectral imaging system composed of an imaging sensor radiometric model (CCD, CMOS, and sCMOS) and an AOTF light transmission model is proposed. Using the radiometric model, a method for obtaining the fixed pattern noise (FPN) of the imaging system by displacing and imaging an illuminated reference target is developed. Methods for estimating the temporal noise of the imaging system, using the photon transfer method, and for correcting FPN are also presented. Noise estimation and image restoration methods were tested on an AOTF hyperspectral imaging system. The results indicate that the developed methods can accurately calculate temporal and FPN, and can effectively correct the acquired images. After correction, the signal-to-noise ratio of the acquired images was shown to increase by 26%.

  18. Spectropolarimetric detection using photoelastic modulators and acousto-optic tunable filter.

    PubMed

    Zhang, Rui; Wen, Tingdun; Wang, Yaoli; Wang, Zhibin; Li, Kewu

    2015-10-10

    This paper proposes a spectropolarimetric detection method based on three photoelastic modulators (3PEMs) and an acousto-optic tunable filter (AOTF). Operating the 3PEMs at slightly resonant frequencies (ω123) generates a different frequency signal that modulates the polarized component of the incident light at a low-frequency (0, 2ω1-2ω3, ω23). The frequency of the low-frequency modulation component is two to three orders of magnitude lower than the resonant frequency of any of the 3PEMs so the general area array detector can realize the detection. I, Q, and U of the incident light's Stokes parameters can be obtained in only one detection by extracting the low-frequency component from the detector's signals, and then combining it with an AOTF to finally realize the spectropolarimetric imaging detection. The paper introduces the basic principle, preliminarily verifies feasibility through a corresponding numerical simulation and experiment, and makes an error analysis on the polarization detection results according to factors of difference frequency and phase delay amplitude. The theory has potential application value to spectropolarimetric technology. PMID:26479804

  19. Influence of nonreciprocal effect on the operation of a collinear acousto-optic filter

    SciTech Connect

    Dobrolenskii, Yu S; Voloshinov, V B; Zyuryukin, Yu A

    2008-01-31

    The nonreciprocal effect is studied theoretically and experimentally by the example of collinear acousto-optic interaction in a birefringent crystal. It is shown that this effect at ultrasonic frequencies {approx}1 GHz and above considerably influences the parameters of modern acousto-optic devices, in particular, tunable acousto-optic filters. The nonreciprocal effect is estimated for different acousto-optic materials. (acoustooptics)

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

    PubMed

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

    2016-04-01

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

  1. Acousto-optic tunable filter for imaging application with high performance in the IR region

    NASA Astrophysics Data System (ADS)

    Valle, S.; Ward, J.; Pannell, C.; Johnson, N. P.

    2015-03-01

    Acousto-Optic Tunable Filters with large acceptance angle (parallel tangent configuration) are the component of choice for imaging application in visible and NIR region wavelength. AOTF in the wavelength range above 2μm could be impractical due to the λ2 and interaction length dependencies on acoustic field intensity to achieve peak diffraction efficiency. A potential solution to reduce the RF power requirement for full diffraction efficiency is to realize a resonant acoustic cavity, and "recycle" the phonons. This configuration could give a theoretical advantage factor between 4 and 10. A prototype device with an operational wavelength range between 1μm and 2μm has been designed and tested and an optimized design to operate between 2μm - 4μm has been prepared and under construction. Due to the presence of standing wave, when the device is not in resonance a feedback signal from the device is affecting the electrical matching and the power delivered to the device is mostly reflected back (VSWR > 25), therefore a special RF driver is required in order to maintain in resonance the device. The resonance frequencies are also affected by the temperature of the device, thus a temperature control mechanism with high accuracy is required. We present the preliminary results of the first prototype, which are in good agreement with the mathematical model and an advantage factor of about 4 has been measured. Further investigation are planned in order to improve the device performance and develop the RF driver for the resonant configuration.

  2. Near-infrared emission spectrometry based on an acousto-optical tunable filter.

    PubMed

    Gonzaga, Fabiano Barbieri; Pasquini, Celio

    2005-02-15

    A spectrometer has been constructed to detect the radiation emitted by thermally excited samples in the near-infrared spectral region extending from 1500 to 3000 nm. The instrument employs an acousto-optical tunable filter (AOTF) made of TeO2 and attains maximum sensitivity by making effective use of the two diffracted beams produced by the anisotropic AOTF. The full exploitation of the transmitted power of the monochromatic beams is reported for the first time and became possible because the detector does not saturate when employed for the acquisition of the weak emission signal in the NIR region, even when exposed to the total (nondiffracted) beam. Thus, modulation and lock-in-based detection can be employed to find the intensity of the diffracted beams superimposed on the nondiffracted beam. The resolution is slighted degraded in view of the small (approximately 10 nm) difference in the wavelength diffracted in the ordinary and extraordinary beams. The instrument has been evaluated in terms of signal-to-noise ratio, effect of sample thickness, and excitation temperature and for its potential in analytical applications in monitoring high-temperature kinetics, for qualitative identification of inorganic solids, for use with a closed cell to obtain spectra of species that evaporate at the temperatures (> 150 degrees C) necessary for sample excitation, and for quantitative purposes in the determination of soybean oil content in olive oil. The feasibility of near-infrared emission spectroscopy has been demonstrated together with some of its advantages over mid-infrared emission spectroscopy, such as greater tolerance to sample thickness, suitable signal-to-noise, and its use in the investigation of kinetic phenomena and phase transitions at high temperatures.

  3. Use of acousto-optic tunable filter in fluorescence imaging endoscopy

    NASA Astrophysics Data System (ADS)

    Bouhifd, Mounir; Whelan, Maurice; Aprahamian, Marc

    2003-10-01

    A prototype instrument for fluorescence-based medical diagnostics in vivo is described. The system consists of a rigid endoscope comprising a UV laser-source for fluorescence excitation and a white light source for direct imaging. An acousto-optic tuneable filter (AOTF) is employed as a full-field tuneable bandpass filter. This allows fast continuous or random-access tuning with high filtering efficiency. A study of the diagnostic potential of fluorescence imaging for pancreatitis was conducted on a rat model. In particular, the aim was to detect autofluorescence of endogenous protoporphyrin IX (PpIX) that has been shown to accumulate in early-stage diseased tissue undergoing an inflammatory response.

  4. Twisted optical-fiber-based acousto-optic tunable filter controlled by the flexural acoustic polarization

    NASA Astrophysics Data System (ADS)

    Park, Hyun Chul; Lee, Kwang Jo

    2015-08-01

    The spectral characteristics of twisted fiber-based acousto-optic filters are theoretically investigated. The influences of three types of flexural acoustic polarization states — linear, circular, and elliptical polarizations — on filter spectra are studied under realistic experimental conditions: a fiber length of 5 - 20 cm and a circumferential fiber twist angle of < 12 π. We will analytically show that either a single- or a dual-resonance filter spectrum is achievable depending on the input polarization state of applied acoustic waves and that the spectral position of each resonance peak can be scanned continuously and linearly in the wavelength domain by using the fiber twist. The feasible spectral tuning range of the resonances is calculated to > 80 nm for a twist angle of 12 π. We will describe how the transmission of each resonance peak can also be selectively tuned by adjusting the ellipticity of the input acoustic polarization from linear to circular. The results illustrate that our approach exploiting a combination of the fiber twist and acoustic polarization management offers an excellent route to the spectral shaping of all-fiber acousto-optic devices in that the transmission of multiple resonances, as well as their spectral positions, are readily and individually controllable in a single device configuration. In addition, we also propose a novel cosine apodization method to suppress the undesirable sidelobe spectra occurring between the dual resonance peaks. The technique is based on a cosine modulation of the AO coupling strength along the fiber, which is achieved by using a combination of the fiber's circumferential twist and the linear acoustic polarization. The proposed scheme is useful to minimize the crosstalk occurring between adjacent resonance peaks. We highlight that our approach is directly applicable to matched filtering as robust, adaptable, stable, and versatile optical filters.

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

    PubMed Central

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

    2016-01-01

    Fast and sensitive Raman spectroscopy measurements are imperative for a large number of applications in biomedical imaging, remote sensing and material characterization. Stimulated Raman spectroscopy offers a substantial improvement in the signal-to-noise ratio but is often limited to a discrete number of wavelengths. In this report, by introducing an electronically-tunable acousto-optical filter as a wavelength selector, a novel approach to a broadband stimulated Raman spectroscopy is demonstrated. The corresponding Raman shift covers the spectral range from 600 cm−1 to 4500 cm−1, sufficient for probing most vibrational Raman transitions. We validated the use of the new instrumentation to both coherent anti-Stokes scattering (CARS) and stimulated Raman scattering (SRS) spectroscopies. PMID:26828198

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

    PubMed

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

    2016-01-01

    Fast and sensitive Raman spectroscopy measurements are imperative for a large number of applications in biomedical imaging, remote sensing and material characterization. Stimulated Raman spectroscopy offers a substantial improvement in the signal-to-noise ratio but is often limited to a discrete number of wavelengths. In this report, by introducing an electronically-tunable acousto-optical filter as a wavelength selector, a novel approach to a broadband stimulated Raman spectroscopy is demonstrated. The corresponding Raman shift covers the spectral range from 600 cm(-1) to 4500 cm(-1), sufficient for probing most vibrational Raman transitions. We validated the use of the new instrumentation to both coherent anti-Stokes scattering (CARS) and stimulated Raman scattering (SRS) spectroscopies. PMID:26828198

  7. 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.

  8. 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.

  9. Acousto-Optic Tunable Filters (AOTFs) Optimised for Operation in the 2-4μm region

    NASA Astrophysics Data System (ADS)

    Ward, J. D.; Valle, S.; Pannell, C.; Johnson, N. P.

    2015-06-01

    Acousto-Optic Tunable Filters (AOTFs) are electronically-controlled bandpass optical filters. They are often preferred in applications in spectroscopy where their agility and rapid random-access tuning can be deployed to advantage. When used for spectral imaging a large aperture (typically 10mm or more) is desired in order to permit sufficient optical throughput. However, in the mid IR the λ2 dependence on RF drive power combined with the large aperture can prove to be a hurdle, often making them impractical for many applications beyond about 2μm. We describe and compare a series of specialised free-space configurations of AOTF made from single crystal tellurium dioxide, that require relatively low RF drive power. We report on AOTFs specifically optimised for operation with a new generation of Supercontinuum source operating in the 2-4μm window and show how these may be used in a spectral imaging system. Finally, we describe an AOTF with an (acoustic) Fabry-Perot cavity operating at acoustic resonance rather than the conventional travelling-wave mode; the acoustic power requirement therefore being reduced. We present an analysis of the predicted performance. In addition, we address the practical issues in deploying such a scheme and outline the design of a prototype “resonant AOTF” operating in the 1-2μm region.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

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

    PubMed

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

    2016-06-01

    Scanning speed and coupling efficiency of excitation light to optic fibres are two major technical challenges that limit the potential of fluorescence excitation-emission matrix (EEM) spectrometer for on-line applications and in vivo studies. In this paper, a novel EEM system, utilizing a supercontinuum white light source and acousto-optic tunable filters (AOTFs), was introduced and evaluated. The supercontinuum white light, generated by pumping a nonlinear photonic crystal fiber with an 800 nm femtosecond laser, was efficiently coupled into a bifurcated optic fiber bundle. High speed EEM spectral scanning was achieved using AOTFs both for selecting excitation wavelength and scanning emission spectra. Using calibration lamps (neon and mercury argon), wavelength deviations were determined to vary from 0.18 nm to -0.70 nm within the spectral range of 500-850 nm. Spectral bandwidth for filtered excitation light broadened by twofold compared to that measured with monochromatic light between 650 nm and 750 nm. The EEM spectra for methanol solutions of laser dyes were successfully acquired with this rapid fluorometer using an integration time of 5 s. PMID:27370436

  12. 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. PMID:26367820

  13. High-resolution spectroscopy using an acousto-optic tunable filter and a fiber-optic Fabry-Perot interferometer

    SciTech Connect

    Baldwin, D.P.; Zamzow, D.S.; DSilva, A.P.

    1996-04-01

    A compact, solid-state, high-resolution spectrometer consisting of an acousto-optic tunable filter (AOTF) and a fiber-optic Fabry{endash}Perot (FFP) interferometer has been developed. The system has been designed for high-resolution inductively coupled plasma atomic emission spectroscopy (ICP-AES) applications. A description of the AOTF-FFP and its performance is presented. The resolution of the AOTF-FFP was determined by measuring the physical widths of ICP emission lines using a 1.5-m-focal-length grating spectrometer and deconvoluting the physical line shapes from the acquired AOTF-FFP spectra. Over the optimum range of the FFP mirror coatings, the resolution is sufficient for the determination of isotopic and hyperfine emission features in ICP-AES experiments, and approaches that of the 1.5-m spectrometer. The application of the AOTF-FFP to the determination of uranium isotopes (U-235 and U-238) introduced into the ICP is presented. {copyright} {ital 1996 Society for Applied Spectroscopy.}

  14. Cosine apodization of dual-resonance all-fiber acousto-optic tunable filters.

    PubMed

    Park, Hyun Chul; Lee, Kwang Jo

    2015-09-01

    We experimentally demonstrate a novel cosine apodization technique for dual-resonance all-fiber acoustic-optic tunable filter. The technique is based on a hybrid control of input acoustic polarization state and circumferential fiber twist. We will show that intrinsic sidelobe spectra occurring between dual filtering bands are successfully suppressed through our approach, which will be also theoretically confirmed via our analytical and numerical studies. The results illustrate that the spectral positions of each resonance are tuned linearly and continuously by the fiber twist, and that overall sidelobe spectra between two resonances are suppressed regardless of fiber twist angle. The proposed scheme is useful to minimize cross talk between adjacent wavelength channels in optical sensor systems. We highlight that our approach is directly applicable to low-noise matched filtering. PMID:26368876

  15. Acousto-optic tunable filter field spectrometer for validation of airborne and spaceborne imaging spectrometers

    NASA Technical Reports Server (NTRS)

    Rider, David M.

    1990-01-01

    A new concept for a field portable spectrometer designed to meet the needs of the remote sensing community is presented. This instrument uses acoustooptic tunable filters (AOTFs) as wavelength sorters, allowing the design of a rugged, compact, light-weight tool that provides broad spectral coverage, great versatility, and ease of utilization. The spectrometer provides continuous spectral coverage from 0.4 to 2.5 microns with two channels defined by detector technology, while a visible channel covering the 0.4 to 1.0 micron spectral range uses silicon PV photodiodes. The short-wavelength IR channel covers the 0.9 to 2.5 micron special range with thermoelectrically cooled lead sulfide PC detectors.

  16. A novel collinear LiNbO3 acousto optical tunable filter with the improved range of transmission and spectral resolution

    NASA Astrophysics Data System (ADS)

    Arellanes, Adan Omar; Shcherbakov, Alexandre S.; Bertone, Emanuele

    2015-02-01

    This investigation represents a deep and advanced analysis of exploiting lithium niobate (LiNbO3) crystals for the collinear acousto-optical tunable filter (AOTF) in violet and near ultraviolet ranges. The selection of this material is motivated by its high birefringence, which is a key parameter for improving the resolution of AOTF. For this matter, we take into account all the important factors that can deteriorate the resolution in order to find extreme conditions for the best performances. In concrete, we analyze the well- known photorefraction effect accompanied by the light induced absorption in those ranges for the LiNbO3 crystals doped by selected materials. The best observed results have been obtained with magnesium (Mg) dopant in the congruent melt of LiNbO3, which also shifts the absorption edge far into the middle UV-range. This analysis had made it possible to formulate the physical criterion determining the enlarged practical limitations of the incident light power density. Together with previously studied non-uniformity and dispersion of the birefringence along the length of acousto-optical interaction in a crystal, we exploit the recently discovered and experimentally confirmed acousto-optical nonlinearity, which can improve the transmission function inherent in the collinear interaction via applying the acoustic waves of finite amplitude in the AOTF. As a result, the obtained spectral resolution is the best available for any collinear AOTF to our knowledge.

  17. Effect of direction of incident light on the basic performance of a TeO2 acousto-optic tunable filter.

    PubMed

    Wang, Pengchong; Zhang, Zhonghua

    2016-08-01

    The selection of the ultrasonic polar angle is vitally important to the performance of an acousto-optic tunable filter (AOTF). The effects of ultrasonic angle on various properties of AOTFs were studied. Then, according to the selected ultrasonic angle, the changes of internal and external separation angles were analyzed in detail when the light was incident upon the crystal surface in two different ways. Additionally, the drift of diffracted light caused by chromatic aberration was analyzed, and an appropriate compensation wedge angle was calculated by the improved derivation formula. The external separation angle increased obviously after placing a wedge angle on the output end. Finally, the effect of incident beam with a cone angle on spectral bandwidth and diffraction efficiency is discussed. PMID:27505364

  18. 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.

  19. Holmium laser with an acousto-optic paratellurite filter

    NASA Astrophysics Data System (ADS)

    Mukhin, A. V.; Velikanov, S. D.; Glukhodedov, V. D.; Zakharov, N. G.; Frolov, Yu N.

    2016-08-01

    Experimental results on a solid-state holmium laser (Ho : YAG) with an intracavity acousto-optic paratellurite filter are presented. The laser power in cw and repetitively pulsed regimes is determined experimentally. It is shown that the use of an acoustooptic filter in the Ho : YAG laser cavity makes it possible to solve several important problems such as obtaining repetitively pulsed lasing, wavelength tuning and linearly polarised emission.

  20. 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.

  1. 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.

  2. Bandwidth control in a hybrid fiber acousto-optic filter.

    PubMed

    Jung, Y; Lee, S B; Lee, Jhang W; Oh, K

    2005-01-01

    We report a bandwidth variation technique in an acousto-optic filter. Utilizing the adiabatic conversion in both optical and acoustic modes, we obtain a novel hybrid waveguide composed of serial concatenation of single-mode fiber (SMF) and two-mode hollow optical fiber (HOF). On the basis of dissimilarity in the phase-matching conditions and beat-length dispersion in SMF and HOF, the FWHM of the resonant bands is varied from 3.8 to 190 nm near the 1.5-microm region in a single device. Furthermore, we theoretically analyze the acousto-optic coupling among the guided modes in HOF, which shows good agreement with experimental observations. PMID:15648646

  3. 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.

  4. Acousto-optic filter for electronic laser tuning

    NASA Technical Reports Server (NTRS)

    Harris, S. E.

    1972-01-01

    Electronically tunable lithium niobate filter utilizes acoustic-optic diffraction for tuning laser to desired frequencies. Filter placed inside laser cavity diffracts incident optical signal of one polarization into orthogonal polarization by collinearly propagating acoustic beam to desired wavelength.

  5. Tunable beam shaping with a phased array acousto-optic modulator.

    PubMed

    Grinenko, A; MacDonald, M P; Courtney, C R P; Wilcox, P D; Demore, C E M; Cochran, S; Drinkwater, B W

    2015-01-12

    We demonstrate the generation of Bessel beams using an acousto-optic array based on a liquid filled cavity surrounded by a cylindrical multi-element ultrasound transducer array. Conversion of a Gaussian laser mode into a Bessel beam with tunable order and position is shown. Also higher-order Bessel beams up to the fourth order are successfully generated with experimental results very closely matching simulations.

  6. Bulk acousto-optic wavelength agile filter module for a wavelength-multiplexed optical scanner.

    PubMed

    Yaqoob, Zahid; Riza, Nabeel A

    2005-05-01

    An acousto-optic tunable filter-based wavelength-selection module with features optimized for a wavelength-multiplexed optical scanner (W-MOS) is proposed and demonstrated. The W-MOS produces high-speed multiple scan beams if it is engaged with an agile tunable source with multiwavelength generation capability. In particular, the proposed fiber-connected module features high-speed, low-loss, narrow-linewidth, and single-multiple wavelength selection by means of radio frequency drive signal control for single- or multiple-beam scan operations. The unique module offers input laser beam power control that in turn delivers the desired scanned laser beam power shaping. Experimental results match module design theory and demonstrate a fast 5.4-micros wavelength selection speed, a low (1.53-dB) fiber-to-fiber optical insertion loss, a 5.55-nm 3-dB spectral width, and a 1500-1600-nm agile wavelength operational band.

  7. 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)

  8. 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.

  9. 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.

  10. Finite-difference time-domain simulation of compact acousto-optic filters based on multireflection beam expanding

    SciTech Connect

    Tsarev, Andrei V

    2007-04-30

    The results of numerical simulation of acousto-optic (AO) tunable filters of a new type based on multireflection beam expanding in waveguide structures are discussed. Planar waveguide filters based on thin chalcogenide (As{sub 2}S{sub 3}) films of lithium niobate (LiNbO{sub 3}) are considered. The operation of filters is analysed by the finite-difference time-domain (FDTD) method by using the license FullWAVE software package (RSoft Design Group, Inc.). It is shown that AO filters have very good dispersion properties and AO filters of extremely small size provide a narrow filtration line within the tuning range of more than 100 nm (at a wavelength of 1.54 {mu}m). It is important that the normalised linewidth (measured in units of the reciprocal filter length) is an order of magnitude smaller than the theoretical limit for AO filters produced from the same material in the conventional way, without the use of multireflection beam expanding. (acoustooptics)

  11. 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.

  12. Automated acousto-optic infrared analyzer system

    SciTech Connect

    Steinbruegge, K.B.; Gottlieb, M.S.

    1984-12-25

    An automated acousto-optic tunable filter infrared analyzer system useable in a variety of industrial and commercial control applications. The system relies upon a narrow band pass tunable acousto-optic filter which is selectively tuned by predetermined rf frequency signals to selectively transmit the narrow band pass of interest which corresponds to a specific molecular species for identification and analysis. The system includes a microcomputer and associated memory function to measure and compare detected signals from an infrared detector which converts the filtered infrared signal to an electrical signal. The memory provides control signals for the computer and for controlling the sequence and frequency of rf energy applied to tune the filter. In this way, the near to mid range infrared can be analyzed for absorption bands corresponding to predetermined molecular species such as combustion product gases, and a feedback signal generated to control the combustion process.

  13. 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.

  14. Effect of the parameters of a wide-aperture acousto-optic filter on the image processing quality

    SciTech Connect

    Voloshinov, V B; Bogomolov, D V

    2006-05-31

    The properties of wide-aperture paratellurite crystal acousto-optic filters used for optical image processing are studied. The influence of parameters of these filters on the quality of optical imaging in laser and nonmonochromatic light is studied. The spatial resolution of filters is measured upon laser and nonmonochromatic illumination of objects. Filtration is performed in a broad wavelength range at different powers of a control electric signal. The optimisation of the filter parameters for improving its spatial resolution is discussed. (optical image processing)

  15. Advanced acousto-optic signal processors

    NASA Technical Reports Server (NTRS)

    Casasent, D.

    1983-01-01

    The basic acousto-optic signal processing architectures (spectrum analyzer, space-integrating, time-integrating, and triple product processor) systems and algorithms such as the chirp-Z transform are reviewed. New acousto-optic data processing systems and applications that utilze these basic architectures and new ones are described. These include a matched spatial filter acousto-optic processor, two new hybrid time and space-integrating systems, a triple product processor, and four new matrix-vector iterative feedback systems.

  16. 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.

  17. Design and testing of space-domain minimum average correlation energy (SMACE) filters for 2-D acousto-optic correlators

    SciTech Connect

    Connelly, J.M.; Vijaya Kumar, B.V.K. ); Molley, P.A.; Stalker, K.T.; Kast, B.A. )

    1991-01-01

    Two-dimensional Acousto-optic (AO) correlators differ from the frequency plane correlators in that multiplying, shifting, and adding, rather than Fourier transforming are used to obtain the correlations. Thus, many of the available composite filter design techniques are not aimed at designing filters for use in AO correlators since they yield frequency-domain functions. In this paper, a method is introduced for designing filter impulse responses of arbitrary extents for implementation on AO correlators. These filters are designed to yield sharp correlation peaks. Simulation results are included to illustrate the viability of the proposed approach. Also included are some initial results from the first successful use of grey-level composite filters on an AO correlator. 12 refs,. 14 figs., 3 tabs.

  18. 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)

  19. Demonstration of a tunable two-frequency projected fringe pattern with acousto-optic deflectors

    SciTech Connect

    Dupont, S.; Kastelik, J. C.

    2008-05-15

    We report on a fringe projector for three-dimensional shape measurement. The developed instrument is able to project a two-frequency fringe pattern, each frequency is independently controlled by electronics. Moreover, each phase of the two fringe patterns is also independently adjusted. The projection system is based on the use of a pair of custom large bandwidth (40 MHz) and high efficiency (60%) TeO{sub 2} deflectors. The developed instrument offers the combined advantages of a static two-frequency fringe projector and of a tunable single frequency fringe projector.

  20. 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.

  1. Investigation of acoustic beam reflection influence on the collinear acousto-optic interaction characteristics.

    PubMed

    Mantsevich, S N

    2016-08-01

    Significant part of acousto-optic devices apply the acoustic beam reflection to arouse the desired type of acoustic mode propagating along the required direction in crystal. The influence of acoustic beam reflection process on the ultrasound field structure in the acousto-optic cell and the collinear acousto-optic diffraction characteristics is examined in this paper. The investigation is carried on the example of the collinear acousto-optic filter fabricated on the base of calcium molybdate crystal. It is shown that the reflection process changes the acoustic field structure and affects the acousto-optic filter transmission function shape and diffraction efficiency.

  2. Investigation of acoustic beam reflection influence on the collinear acousto-optic interaction characteristics.

    PubMed

    Mantsevich, S N

    2016-08-01

    Significant part of acousto-optic devices apply the acoustic beam reflection to arouse the desired type of acoustic mode propagating along the required direction in crystal. The influence of acoustic beam reflection process on the ultrasound field structure in the acousto-optic cell and the collinear acousto-optic diffraction characteristics is examined in this paper. The investigation is carried on the example of the collinear acousto-optic filter fabricated on the base of calcium molybdate crystal. It is shown that the reflection process changes the acoustic field structure and affects the acousto-optic filter transmission function shape and diffraction efficiency. PMID:27153373

  3. 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. PMID:26367426

  4. 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.

  5. An acousto-optical imaging spectrometer for astrophysical measurements

    NASA Astrophysics Data System (ADS)

    Anikin, S. P.; Esipov, V. F.; Molchanov, V. Ya.; Tatarnikov, A. M.; Yushkov, K. B.

    2016-07-01

    An optical scheme of an acousto-optical imaging spectrometer for observing extended astrophysical objects with line emission spectra is proposed. The use of an additional prism with a specified angular dispersion makes it possible to separate images of an extended object at different emission lines and images generated by minor maxima of the acousto-optical filter transmission function. A prototype of the imaging spectrometer has been designed.

  6. Image transformation caused by wide-angle acousto-optic interaction

    SciTech Connect

    Machikhin, A S; Pozhar, V E

    2010-11-13

    The problem of diffraction of divergent image-transfer light beams by an acoustic wave is considered. Expressions that describe the transfer function as a function of spectral and angular coordinates and are valid for any birefringence are obtained for the first time. The main characteristics of wide-angle acousto-optic tunable filters (angular and spectral bandwidths) are calculated and compared with the experimental data. The dependence of the transfer function on the angle of light incidence is investigated and a fundamental change in its topology is shown. (acoustooptics)

  7. 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.

  8. 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.

  9. 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

  10. Collinear Acousto-Optical Transformation of Bessel Light Beams in Biaxial Gyrotropic Crystals

    NASA Astrophysics Data System (ADS)

    Belyi, V. N.; Kulak, G. V.; Krokh, G. V.; Shakin, O. V.

    2016-05-01

    The collinear acousto-optical transformation of Bessel light beams in biaxial gyrotropic crystals into two annular, internal conical refraction beams with orthogonal elliptical polarization is studied. It is found that the diffraction efficiency is maximal (~50-60%) for low ultrasound intensities and varies slightly with further increases in acoustic power. At high ultrasound intensities, the intensities of the transmitted and diffracted annular beams differ insignificantly. The possible use of this acousto-optical interaction for creating collinear tuneable narrow-band acousto-optical filters at low ultrasonic frequencies is demonstrated.

  11. 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.

  12. The Development and Field Testing of the Portable Acousto-optic Spectrometer for Astrobiology

    NASA Astrophysics Data System (ADS)

    Chanover, Nancy J.; Uckert, Kyle; Voelz, David; Boston, Penelope

    2014-11-01

    The development of in situ instrumentation for the detection of biomarkers on planetary surfaces is critical for the search for evidence of present or past life in our solar system. In our earlier instrument development efforts we addressed this need through the development of a near-infrared point spectrometer intended for quick-look examinations of samples that could be subsequently analyzed with a laser desorption time-of-flight mass spectrometer. The point spectrometer utilized an acousto-optic tunable filter (AOTF) crystal as the wavelength selecting element. In parallel with the aforementioned development efforts we identified the need for a portable version of the AOTF spectrometer that we could test and demonstrate in a range of field locations on Earth chosen to serve as terrestrial analogs for extreme environments elsewhere in the solar system. Here we describe the development and field testing of the Portable Acousto-optic Spectrometer for Astrobiology (PASA). We demonstrated this instrument in two very different cave environments, a predominantly gypsum and calcite cave in New Mexico and an actively forming cave rich in hydrated sulfates in Tabasco, Mexico. Both of these microbially active environments contain evidence of biologic alteration of minerals, which can be detected using IR spectroscopy. We will describe the instrument operations and present some data acquired with PASA to demonstrate its efficacy as a tool for biomarker detection on planetary surfaces. This work was supported by NASA's EPSCoR program through grant number NNX12AK77A.

  13. POLARIS-II - An acousto-optic imaging spectropolarimeter for ground-based astronomy

    NASA Technical Reports Server (NTRS)

    Glenar, D. A.; Hillman, J. J.; Saif, B.; Bergstralh, J.

    1992-01-01

    A compact, acousto-optic tunable filter (AOTF) imaging spectropolarimeter for ground based astronomy from 400-1100 nm has been constructed at NASA/GSFC. The key components of this instrument are a TeO2 non-collinear AOTF, CCD camera, and an all-reflective optical relay assembly which uses a single elliptical mirror to produce side-by-side orthogonally polarized spectral images. The instrument was used at the Lowell Observatory 42-inch telescope for 'first light' planetary imaging and measurements of photometric standard stars. Narrow-band images of Saturn near 700 nm appear to show polarization effects which result from multiple scattering by aerosols. The instrument has recently been upgraded in order to integrate the RF drive electronics and eliminate contamination by scattered light. Design of the instrument and some initial results are presented.

  14. Systolic acousto-optic binary convolver

    SciTech Connect

    Guilfoyle, P.S.

    1984-01-01

    A novel high speed array processing optical architecture is described. A multichannel acousto-optic binary convolver is architecturally configured as a systolic array processor. The architecture provides a high speed means of matrix/vector multiplications using the digital multiplication via an analog convolution algorithm. This algorithm and a systolic acousto-optic implementation permit the speed of optics to be combined with the accuracy of digital computation. 15 references.

  15. 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.

  16. Acousto-optic spectrometer for radio astronomy

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

    Recent developments in acousto-optic techniques and in photodetector arrays have made feasible a new type of RF spectrometer, offering the advantages of wide bandwidth, high resolution, large number of channels in compact, lightweight, energy efficient, and relatively low cost systems. Such a system employs an acousto-optic diffraction cell which serves the key role of converting RF signals to ultrasonic traveling-waves modulating the optical index of the cell. The cell is illuminated across its aperture by a monochromatic laser beam. A fraction of the light is diffracted by the acoustic waves. A focusing lens follows the cell and essentially performs a Fourier transform of the RF signal into a far-field intensity pattern. CSIRO in Australia and the Tokyo Astronomical Observatory in Japan have taken the lead in using acousto-optic techniques in astronomical applications. The first practical device was successfully made at CSIRO for obtaining dynamical spectrographs of solar radio emission.

  17. Electronically tunable thulium-holmium mode-locked fiber laser for the 1700-1800 nm wavelength band.

    PubMed

    Noronen, Teppo; Okhotnikov, Oleg; Gumenyuk, Regina

    2016-06-27

    We demonstrate a widely tunable, mode-locked fiber laser capable of producing sub-picosecond pulses between 1705 and 1805 nm. The 100 nm tuning range is achieved by using intracavity acousto-optic tunable filter. The laser delivers highly stable pulses via self-starting hybrid mode-locking triggered by frequency-shifting and nonlinear polarization evolution. PMID:27410623

  18. High-dynamic-range hybrid analog-digital control broadband optical spectral processor using micromirror and acousto-optic devices.

    PubMed

    Riza, Nabeel A; Reza, Syed Azer

    2008-06-01

    For the first time, to the best of our knowledge, the design and demonstration of a programmable spectral filtering processor is presented that simultaneously engages the power of an analog-mode optical device such as an acousto-optic tunable filter and a digital-mode optical device such as the digital micromirror device. The demonstrated processor allows a high 50 dB attenuation dynamic range across the chosen 1530-1565 nm (~C band). The hybrid analog-digital spectral control mechanism enables the processor to operate with greater versatility when compared to analog- or digital-only processor designs. Such a processor can be useful both as a test instrument in biomedical applications and as an equalizer in fiber communication networks.

  19. 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.

  20. 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. PMID:27628370

  1. 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.

  2. Acousto-optic Extensometer for Bolts

    NASA Technical Reports Server (NTRS)

    Maram, J.; Kuhr, G.

    1985-01-01

    Bolt torque or tension deduced from non contacting measurements. Pulsed Laser induces shockwave in bolthead while continuous-wave acousto-optic detector monitors distortion produced by shock. Shock travel time measured to determine bolt length. Solid-state position detector relatively inexpensive and keeps down cost of extensometer.

  3. Integrated acousto-optic mode locker

    SciTech Connect

    Myslinski, P.

    1986-11-01

    A new type of the acousto-optic modulator is presented. The novel design reduces the number of optical elements inside the laser cavity resulting in higher quality of the mode-locked pulses. An application of the modulator to an argon-ion laser is described.

  4. 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.

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

    PubMed

    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. PMID:27250458

  6. New Studies of Acousto-Optic Interactions.

    NASA Astrophysics Data System (ADS)

    Neev, Joseph

    1988-06-01

    Acousto-optics is the field of science pertaining to the study of interactions between light and acoustic vibrations in solids, liquids, or gases. In recent years this field has evolved to much more than just the point where acoustics and optics meet. It has become a crossroad for many disciplines and technologies. This diversity in itself makes it a difficult and interesting area of research. In this work some fundamental concepts of acousto -optic interactions are re-examined. New understanding was gained of the process of diffraction of light by a propagating sound column under the condition of changing interaction orientation and changing sound frequency. This new understanding has shown existing treatments of these problems to be incomplete. It is further shown that one such commonly used model yields wrong predictions which stand in violation of the principle of time reversal. A device whose principle of operation is based on the knowledge gained in this study was implemented in a ring laser to induce unidirectional operation. In addition, acousto -optic light deflectors were investigated and new insight to their theory of operation was obtained. New operating configurations for these devices were tested, and future uses and applications are suggested.

  7. Techniques for measuring radiation induced effects of acousto optic devices

    SciTech Connect

    Taylor, E.W.

    1995-08-01

    Innovative measurement techniques for determining radiation induced changes in acousto optic devices are briefly discussed. Measurements of acousto optic operational parameters such as signal transmission efficiency, diffraction efficiency, spatial intensity and bandwidth responses during electron irradiations are described. During exposure to pulsed electrons, only transient perturbations to the acousto optic operational parameters were experienced. Examples of new measurement procedures and typical data resulting from the measurements are presented.

  8. Acousto-optic differential optical absorption spectroscopy for atmospheric measurement of nitrogen dioxide in Hong Kong.

    PubMed

    Cheng, Andrew Y S; Chan, M H

    2004-12-01

    Measurement of the atmospheric concentration of nitrogen dioxide (NO(2)) pollutant was demonstrated by differential optical absorption spectroscopy (DOAS) using a visible acousto-optic tunable filter. In a traditional spectral scanning DOAS system for atmospheric concentration monitoring, a highly stable light source is required. When the light intensity fluctuates during scanning, the concentration retrieval will be inaccurate. In order to reduce the error due to intensity fluctuations, a modified DOAS system has been developed by introducing a broadband light intensity monitoring channel. Using the measured intensity of the broadband channel as the intensity of the light source, the spectrum can be de-biased and the residual intensity variation will primarily result from atmospheric extinction. In addition, by employing the lock-in detection technique, the background light interference is also removed in the modified DOAS system. The atmospheric NO(2) concentration measurement was performed at the campus of City University of Hong Kong, and the results were compared with the concentration reported from a nearby monitoring station in Sham Shui Po, operated by the Hong Kong Environmental Protection Department.

  9. The Aerosol Limb Imager: acousto-optic imaging of limb scattered sunlight for stratospheric aerosol profiling

    NASA Astrophysics Data System (ADS)

    Elash, B. J.; Bourassa, A. E.; Loewen, P. R.; Lloyd, N. D.; Degenstein, D. A.

    2015-12-01

    The Aerosol Limb Imager (ALI) is an optical remote sensing instrument designed to image scattered sunlight from the atmospheric limb. These measurements are used to retrieve spatially resolved information of the stratospheric aerosol distribution, including spectral extinction coefficient and particle size. Here we present the design, development and test results of an ALI prototype instrument. The long term goal of this work is the eventual realization of ALI on a satellite platform in low earth orbit, where it can provide high spatial resolution observations, both in the vertical and cross-track. The instrument design uses a large aperture Acousto-Optic Tunable Filter (AOTF) to image the sunlit stratospheric limb in a selectable narrow wavelength band ranging from the visible to the near infrared. The ALI prototype was tested on a stratospheric balloon flight from the Canadian Space Agency (CSA) launch facility in Timmins, Canada, in September 2014. Preliminary analysis of the hyperspectral images indicate that the radiance measurements are of high quality, and we have used these to retrieve vertical profiles of stratospheric aerosol extinction coefficient from 650-1000 nm, along with one moment of the particle size distribution. Those preliminary results are promising and development of a satellite prototype of ALI within the Canadian Space Agency is ongoing.

  10. Linearization of acousto-optic modulator transmission function

    NASA Astrophysics Data System (ADS)

    Korol, G.; Moskaletz, D.; Moskaletz, O.

    2016-08-01

    The procedure of linearization of nonlinear transmission function of the optical transparency in the form of an acousto-optic modulator by the methods of nonlinear functional analysis is described. The transmission function of a pair of acousto-optic modulators is linearized in the context of generalized superposition principle.

  11. Theoretical study of Fourier-transform acousto-optic imaging.

    PubMed

    Barjean, Kinia; Ramaz, François; Tualle, Jean-Michel

    2016-05-01

    We propose a full theoretical study of Fourier-transform acousto-optic imaging, which we recently introduced and experimentally assessed in [Opt. Lett.40, 705-708 (2015)OPLEDP0146-959210.1364/OL.40.000705] as an alternative to achieve axial resolution in acousto-optic imaging with a higher signal-to-noise ratio. PMID:27140883

  12. NASA applications for acousto-optic spectrometers

    NASA Technical Reports Server (NTRS)

    Chin, G.

    1984-01-01

    Small, compact, and rugged IF spectrometers are needed in high resolution heterodyne receivers designed for a new generation of space-borne telescopes planned for the next decade. Acousto-optic Spectrometers (AOS) promise to provide the necessary bandwidth and resolution in a package which is compact, power efficient, and ruggedized for space applications. Sensitivity, linearity, and stability are the primary goals of an astronomical receiver and these features must be demonstrated in order for an AOS to be accepted in place of more conventional RF or digital technology.

  13. 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).

  14. Acousto-optic image processing in coherent light

    SciTech Connect

    Balakshy, V I; Voloshinov, V B

    2005-01-31

    The results of recent studies on coherent acousto-optic image processing performed at the chair of physics of oscillations at the Department of Physics of Moscow State University are reported. It is shown that this processing method is based on the filtration of the spatial spectrum of an optical signal in an acousto-optic cell. The main attention is paid to the analysis of the dependence of the transfer function of the cell on the crystal cut, geometry of acousto-optic interaction, and acoustic-wave parameters. It is shown that an acousto-optic cell allows the image differentiation and integration as well as the visualisation of phase objects. The results of experiments and computer simulation are presented which illustrate the possibilities of acousto-optic image processing. (laser applications and other topics in quantum electronics)

  15. Towards acousto-optic tissue imaging with nanosecond laser pulses.

    PubMed

    Resink, S G; Hondebrink, E; Steenbergen, W

    2014-02-10

    We present a way to generate acousto-optical signals in timovssue-like media with nanosecond laser pulses. Our method is based on recording and analyzing speckle patterns formed by interaction of nanosecond laser pulses with tissue, without and with simultaneous application of ultrasound. Stroboscopic application allows visualizing the temporal behavior of speckles while the ultrasound is propagating through the medium. We investigate two ways of quantifying the acousto-optic effect, viz. adding and subtracting speckle patterns obtained at various ultrasound phases. Both methods are compared with the existing speckle contrast method using a 2D scan and are found to perform similarly. Our method gives outlook on overcoming the speckle decorrelation problem in acousto-optics, and therefore brings in-vivo acousto-optic measurements one step closer. Furthermore it enables combining acousto-optics and photoacoustics in one setup with a single laser.

  16. 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.

  17. 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

  18. 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

  19. 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

  20. Two-Dimensional Acousto-Optical Spectrum Analyzer

    NASA Technical Reports Server (NTRS)

    Ansari, Homayoon; Lesh, James R.; Metscher, Brian

    1991-01-01

    State-of-the-art two-dimensional acousto-optical spectrum analyzer processes input radio-frequency signal in real time into components in any number of spectral channels up to about 10(Sup5). Input radio-frequency signal to be analyzed launched via transducer into acousto-optical device along x axis. Acousto-optical device becomes Bragg cell. Pulsed plane waves of light from laser aimed at Bragg cell, which spatially modulates phases of plane waves and diffracts waves according to pattern of acoustic signal.

  1. Eliminating Bias In Acousto-Optical Spectrum Analysis

    NASA Technical Reports Server (NTRS)

    Ansari, Homayoon; Lesh, James R.

    1992-01-01

    Scheme for digital processing of video signals in acousto-optical spectrum analyzer provides real-time correction for signal-dependent spectral bias. Spectrum analyzer described in "Two-Dimensional Acousto-Optical Spectrum Analyzer" (NPO-18092), related apparatus described in "Three-Dimensional Acousto-Optical Spectrum Analyzer" (NPO-18122). Essence of correction is to average over digitized outputs of pixels in each CCD row and to subtract this from the digitized output of each pixel in row. Signal processed electro-optically with reference-function signals to form two-dimensional spectral image in CCD camera.

  2. 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.

  3. Ultrafast acousto-optic imaging with ultrasonic plane waves.

    PubMed

    Laudereau, Jean-Baptiste; Grabar, Alexander A; Tanter, Mickaël; Gennisson, Jean-Luc; Ramaz, François

    2016-02-22

    Due to multiple light scattering inside biological tissues, deep non-invasive optical medical imaging is very challenging. Acousto-optic imaging is a technique coupling ultrasound and light that allows recovering optical contrast at depths of few centimeters with a millimeter resolution. Recent advances in acousto-optic imaging are using short focused ultrasound pulses often averaged over several hundred or thousand pulses. As the pulsing rate of commercial probes is limited to about few ultrasound cycles every 100 μs, acquiring an acousto-optic image usually takes several tens of seconds due to the high number of acoustic pulses excitation. We propose here a new acousto-optic imaging technique based on the use of ultrasound plane waves instead of focused ones that allows increasing drastically the imaging rate. PMID:26907033

  4. Three-Dimensional Acousto-Optical Spectrum Analyzer

    NASA Technical Reports Server (NTRS)

    Ansari, Homayoon; Lesh, James R.

    1991-01-01

    Experimental acousto-optical Bragg-cell spectrum analyzer achieves subhertz frequency resolution. System represents extension to three dimensions of two-dimensional spectrum-analyzer concept described in, "Two-Dimensional Acousto-Optical Spectrum Analyzer" (NPO-18092). First and second dimensions two spatial dimensions of charge-coupled-device (CCD) imaging array. Third dimension time, as sampled at frame rate of CCD array.

  5. A miniature acousto-optic image correlator

    SciTech Connect

    Molley, P.A.; Sweatt, W.C.; Strong, D.S.

    1991-01-01

    An acousto-optic (AO) image correlator architecture will be presented that minimizes the overall system size while maintaining excellent image quality for large input scenes. The correlator can accommodate grayscale input scenes with dimensions of 512 {times} 244 pixels and grayscale reference templates of size 64 {times} 64 pixels. The size of the optical system, however is less than ten cubic inches, 1in. {times} 1in. {times} 9in. This design incorporates a surface emitting laser diode array that has a center-to-center spacing of the laser elements matched to the row spacing on the CCD. Furthermore, the space-bandwidth and center frequency of the AO cell are chosen to match the length of the input image information in the cell to the width of the CCD. These two design decisions allow close to one-to-one imaging through the entire optical system producing the shortest possible path length. The optics were then designed with a goal of producing nearly diffraction-limited quality. 8 refs., 3 figs., 1 tab.

  6. 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.

  7. Acousto-optic, electro-optic, and magneto-optic devices and applications

    SciTech Connect

    Lucero, J.

    1987-01-01

    These proceedings contain 30 papers grouped under the headings of: Acousto-optic devices; Signal processing architectures; Acousto-optic and electro-optic applications; Magneto-optic and guided wave optic devices.

  8. The Aerosol Limb Imager: acousto-optic imaging of limb-scattered sunlight for stratospheric aerosol profiling

    NASA Astrophysics Data System (ADS)

    Elash, B. J.; Bourassa, A. E.; Loewen, P. R.; Lloyd, N. D.; Degenstein, D. A.

    2016-03-01

    The Aerosol Limb Imager (ALI) is an optical remote sensing instrument designed to image scattered sunlight from the atmospheric limb. These measurements are used to retrieve spatially resolved information of the stratospheric aerosol distribution, including spectral extinction coefficient and particle size. Here we present the design, development and test results of an ALI prototype instrument. The long-term goal of this work is the eventual realization of ALI on a satellite platform in low earth orbit, where it can provide high spatial resolution observations, both in the vertical and cross-track. The instrument design uses a large-aperture acousto-optic tunable filter (AOTF) to image the sunlit stratospheric limb in a selectable narrow wavelength band ranging from the visible to the near infrared. The ALI prototype was tested on a stratospheric balloon flight from the Canadian Space Agency (CSA) launch facility in Timmins, Canada, in September 2014. Preliminary analysis of the hyperspectral images indicates that the radiance measurements are of high quality, and we have used these to retrieve vertical profiles of stratospheric aerosol extinction coefficient from 650 to 1000 nm, along with one moment of the particle size distribution. Those preliminary results are promising and development of a satellite prototype of ALI within the Canadian Space Agency is ongoing.

  9. Beam deformation within an acousto-optic lens.

    PubMed

    Zhou, Zhenqiao; Li, Longhui; Wang, Jiancun; Hu, Qinglei; Zeng, Shaoqun

    2015-05-15

    The acousto-optic lens (AOL) is becoming a popular tool in the neuroscience field. Here we analyzed the deformation of the diffraction beam after passage through an AOL consisting of a pair of acousto-optic deflectors using both theoretical and experimental data. The results showed that, because of the high sensitivity of optical spatial frequencies of acousto-optic deflectors, the boundary strength of the diffraction beam of the AOL decreases significantly. When the focal length of AOL diminishes, the deformation of the diffraction beam becomes more serious with a smaller beam size. This deformation of the diffraction beam finally leads to a decreased illuminative numerical aperture, which worsens the image's spatial resolution. PMID:26393698

  10. Dynamic fluorescence lifetime imaging based on acousto-optic deflectors

    NASA Astrophysics Data System (ADS)

    Yan, Wei; Peng, Xiao; Qi, Jing; Gao, Jian; Fan, Shunping; Wang, Qi; Qu, Junle; Niu, Hanben

    2014-11-01

    We report a dynamic fluorescence lifetime imaging (D-FLIM) system that is based on a pair of acousto-optic deflectors for the random regions of interest (ROI) study in the sample. The two-dimensional acousto-optic deflector devices are used to rapidly scan the femtosecond excitation laser beam across the sample, providing specific random access to the ROI. Our experimental results using standard fluorescent dyes in live cancer cells demonstrate that the D-FLIM system can dynamically monitor the changing process of the microenvironment in the ROI in live biological samples.

  11. Programmable Real-Time Acousto-Optic/CCD SAR processor

    NASA Technical Reports Server (NTRS)

    Haney, M.; Wagner, K.; Psaltis, D.

    1984-01-01

    The theory of operation of the Real-Time Acousto-Optic SAR Processor is reviewed and recent experimental results are presented. The results include a demonstration of the real-time imaging capability of the processor with simulated radar signals. An advanced version of this processor is then described in which a programmable reference function is entered via a second acousto-optic device to eliminate the need for a 2-D SLM. In this implementation the reference function is updated by electronic means to give the processor the flexibility to adapt rapidly to changes in the parameters of the radar/target geometry.

  12. Acousto-optic techniques for real SAR imaging

    NASA Technical Reports Server (NTRS)

    Haney, M.; Psaltis, D.

    1985-01-01

    Recent advancements in the development of the Real Time Acousto-optic SAR Processor are presented. In particular, the technique for introducing the azimuth reference function into the processor via an acousto-optic Bragg cell is discussed. This approach permits the reference function to be stored in electronic memory, thus giving the processor the flexibility needed to adapt rapidly to changes in the radar/target geometry. The architecture is described and results are presented which show the applicability of the technique to both spot-light and strip-map SAR.

  13. 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.

  14. Developing a stochastic model for acousto-optic tissue imaging

    NASA Astrophysics Data System (ADS)

    Resink, Steffen G.; Steenbergen, Wiendelt

    2012-02-01

    Direct optical measurements in scattering media offer poor resolution due to the high scattering. Ultrasound is scattered orders of magnitude less in tissue compared with light and therefore offers good resolution. Photoacoustics and acoustooptics are both relatively new hybrid techniques that enable measurements of optical properties in scattering media by combining ultrasound and light. Quantified measurements of the fluence and absorption coefficient however are desired and can not be performed by these separate techniques. A new approach to achieve this goal is to combine both hybrid techniques. By combining photoacoustic and acousto-optic measurements there is sufficient information to calculate the absorption coefficient and fluence at the ultrasound focus used for the acousto-optics. We require knowledge on the interaction of light and sound inside tissue, so the size of the so called tagging volume can be determined. This tagging volume is defined by the size and shape of the ultrasound focus used in the acousto-optic measurements. A stochastic model for acousto-optics is under development that used existing knowledge on the in the interaction between light and sound. By separating light transport and the interactions of light and sound and writing this interaction as a probability density function it is possible to find the effective geometrical properties of the tagging volume. At the moment multiple interaction mechanisms of sound and light are added to this model. In the future this model will be validated in phantoms and biological tissue.

  15. Acousto-optic tunable filter near-infrared spectroscopy for in-line monitoring liquid-liquid extraction of Gardenia jasminoides Ellis based on statistical analysis.

    PubMed

    Wu, Sha; Jin, Ye; Liu, Qi-An; Wu, Jian-Xiong; Bi, Yu-An; Wang, Zhen-Zhong; Xiao, Wei

    2015-10-01

    This study aimed to monitor liquid-liquid extraction of Gardenia jasminoides Ellis (Zhizi in Chinese) using in-line near-infrared spectroscopy. Shanzhiside (SZS), deacetyl asperulosidic acid methyl ester (DAAME), genipin-1-β-D-gentiobioside (GG), geniposide (GS), total acids (TA) and soluble solid content (SSC) were selected as quality control indicators, and measured by reference methods. Both partial least-squares regression (PLSR) and back propagation artificial neural networks (BP-ANN) were applied to create models to predict the content of above indicators. Paired-samples t-test and nonparametric test were used to compare differences in predictive values between two models of each indicator. Relative standard error of prediction (RSEP) and mean absolute percentage error (MAPE) were used to evaluate the predictive accuracy of the established models. The results showed that there was no significant difference in predicting DAAME, GS and TA between two models. However, PLSR model gave better accuracy in predicting GG and SZS than BP-ANN model. The BP-ANN model of SSC was better than PLSR model. This study shows that NIR spectroscopy can be used for rapid and accurate analysis of quality control indicators in the liquid-liquid extraction of Zhizi. Simultaneously, this study can serve as technical support for the application of NIR spectroscopy in the industrial production process. PMID:26601419

  16. Novel tunable Fabry-Perot filters for FBG sensing system

    NASA Astrophysics Data System (ADS)

    Wu, Wei; Tong, Xinglin; Liu, Xin; Chen, Ting

    2008-12-01

    Tunable filters with a wide tunable rang have been found wide applications and be the key component in fiber optical communication system and fiber sensor system. It is hard to fabricate a fiber Fabry-Perot tunable filter. In this paper, the principles of Fabry-Perot filter is introduced, and a novel tunable Fabry-Perot filter is designed and fabricated. The fabricated process of the tunable filter is described and the transmission spectrum of tunable F-P filter in experiment is given and discussed. The tunable F-P filter has the advantages of simple structure, low modulated voltage and cost effectiveness. The filter can be applied to wavelength interrogation in fiber Bragg grating (FBG) sensing system to detect the drift of the fiber Bragg wavelength.

  17. Cascaded Mach–Zehnder interferometer tunable filters

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    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-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.

  19. 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.

  20. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    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.

  2. Acousto-optical/Magneto-optical Correlator Or Convolver

    NASA Technical Reports Server (NTRS)

    Liu, Hua-Kuang; Davis, Jeffrey A.

    1989-01-01

    Experimental system demonstrates optical processing of multiple channels of binary signals. One input channel contains signal that varies with time and applied to one-dimensional acousto-optical cell. Other input channel contains two-dimensional pattern that is stationary or can vary with time and applied to magneto-optical spatial light modulator. Output is time-varying correlation or convolution of first input with one of rows in second input.

  3. 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.

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

    NASA Astrophysics Data System (ADS)

    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

    2016-08-01

    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.

  5. 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

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

    PubMed

    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

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

    PubMed

    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

    2016-08-05

    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.

  8. Fast, electrically tunable filters for hyperspectral imaging

    NASA Astrophysics Data System (ADS)

    Liberman, V.; Parameswaran, L.; Gear, C.; Cabral, A.; Rothschild, M.

    2014-06-01

    Tunable, narrow-wavelength spectral filters with a ms response in the mid-wave/long-wave infrared (MW/LWIR) are an enabling technology for hyperspectral imaging systems. Few commercial off-the-shelf (COTS) components for this application exist, including filter wheels, movable gratings, and Fabry-Perot (FP) etalon-based devices. These devices can be bulky, fragile and often do not have the required response speed. Here, we present a fundamentally different approach for tunable reflective IR filters, based on coupling subwavelength plasmonic antenna arrays with liquid crystals (LCs). Our device operates in reflective mode and derives its narrow bandwidth from diffractive coupling of individual antenna elements. The wavelength tunability of the device arises from electrically-induced re-orientation of the LC material in intimate contact with antenna array. This re-orientation, in turn, induces a change in the local dielectric environment of the antenna array, leading to a wavelength shift. We will first present results of full-field optimization of micron-size antenna geometries to account for complex 3D LC anisotropy. We have fabricated these antenna arrays on IR-transparent CaF2 substrates utilizing electron beam lithography, and have demonstrated tunability using 5CB, a commercially available LC. However, the design can be extended to high-birefringence liquid crystals for an increased tuning range. Our initial results demonstrate <60% peak reflectance in the 4- 6 μm wavelength range with a tunability of 0.2 μm with re-orientation of the surface alignment layers. Preliminary electrical switching has been demonstrated and is being optimized.

  9. 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

  10. Electro-optical tunable birefringent filter

    DOEpatents

    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.

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

    PubMed

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

    2016-09-01

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

  12. Bulk and integrated acousto-optic spectrometers for radio astronomy

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

    The development of sensitive heterodyne receivers (front end) in the centimeter and millimeter range, and the construction of sensitive RF spectrometers (back end) enable the spectral lines of interstellar molecules to be detected and identified. A technique was developed which combines acoustic bending of a collimated coherent light beam by a Bragg cell followed by detection by a sensitive array of photodetectors (thus forming an RF acousto-optic spectrometer (AOS). An AOS has wide bandwidth, large number of channels, and high resolution, and is compact, lightweight, and energy efficient. The thrust of receiver development is towards high frequency heterodyne systems, particularly in the millimeter, submillimeter, far infrared, and 10 micron spectral ranges.

  13. Acousto-optic mode-locked soliton laser

    SciTech Connect

    Pinto, J.F.; Yakymyshyn, C.P.; Pollock, C.R.

    1988-05-01

    An acousto-optic modulator has been used to actively mode lock a KCl:Tl/sup 0/ (1) color-center laser at 1.5 ..mu..m. The color-center laser is capable of generating transform-limited pulses as short as 6 psec with 2-W cw pump power. Based on this actively mode-locked KCl:Tl/sup 0/ (1) laser a stable soliton laser has been operated, with performance similar to that of the synchronously pumped soliton laser.

  14. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

    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.

  16. Fast acousto-optic q-switch laser

    SciTech Connect

    Ellis, F.E.

    1981-12-29

    A fast acousto-optic q-switch laser is taught comprising a lasing medium, reflecting means mounted substantially perpendicular to the longitudinal axis of the lasing medium and spaced from a first end thereof, feedback reflecting means spaced from a second end of the lasing medium, optical pumping means for pumping the lasing medium, an acousto-optic switch mounted along and tilted at a preselected angle with respect to the longitudinal axis of the lasing medium between the second end of the lasing medium and said feedback reflecting means and spaced from the second end of said lasing medium for deflecting a portion of the radiation emitted by the lasing medium, and first and second transducers mounted in opposition to each other on the switch, the first transducer mounted with respect to the switch such that the gradient of the envelope of the acoustic energy introduced into and propagated through the switch approximates the gradient of the non-uniform population inversion directly in the lasing medium, and the second transducer mounted with respect to the switch such that acoustic energy introduced into and propagated through the switch has a velocity vector opposite to the first transducer and timed to provide maximum feedback when lasing occurs, said feedback reflecting means positioned along and tilted at a preselected angle with respect to the longitudinal axis of said lasing medium related to the path to be taken by the deflected portion of radiation for reflecting said deflected portion of radiation back to said switch.

  17. A porous silicon thermally tunable optical filter

    NASA Astrophysics Data System (ADS)

    Song, Da; Tokranova, Natalya; Gracias, Alison; Castracane, James

    2008-02-01

    Porous silicon (PSi) is a promising material for the creation of optical components for chip-to-chip interconnects because of its unique optical properties, flexible fabrication methods and integration with conventional CMOS material sets. In this paper, we present a novel active optical filter made of PSi to select desired optical wavelengths. The tunable membrane type optical filter is based on a Fabry-Perot interferometer employing two Bragg reflectors separated by an adjustable air gap, which can be thermally controlled. The Bragg reflectors contain alternating layers of high and low porosities. These layers were created by electrochemical etching of p+ type silicon wafers by varying the applied current during etching process. Micro bimorph actuators are designed to control the movement of the top DBR mirror, which changes the cavity thickness. By varying the applied current, the proposed filter can tune the transmitted wavelength of the optical signal. Various geometrical shapes and sizes ranging from 100μm to 1mm of the active filtering region have been realized for specific applications. The MOEMS technology-based device fabrication is fully compatible with the existing IC mass fabrication processes, and can be integrated with a variety of active and passive optical components to realize inter-chip or intra-chip communication at the system level at a relatively low cost.

  18. 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.

  19. Acousto-optic spectrum analyzer for plasma diagnostics

    SciTech Connect

    Irby, J.H.; Beals, D.

    1987-08-01

    An acousto-optic rf spectrometer (AOS) has been designed and constructed for use on the CONSTANCE B and TARA mirror experiments at MIT. The AOS is an analog preprocessor of data that can come from a variety of sources, including rf probes and microwave/laser scattering experiments. The output of the AOS is the Fourier transform amplitude of the input in a parallel format suitable for computer acquisition. The spectrometer, having a bandwidth of 500 MHz and a resolution of 1 MHz, together with its receiver, is capable of looking at fluctuations anywhere in the frequency range of a few MHz up to 4 GHz. Power levels of a few nanowatts can be detected. Complete 500-MHz-wide spectra can be processed and acquired at the rate of 1 every 10 ..mu..s. The optical components, receiver, and data-acquisition interface will be discussed, and initial data taken on the CONSTANCE B experiment will be shown.

  20. 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.

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

    PubMed

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

    2015-11-01

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

  2. Microlens optical fiber Fabry-Pérot tunable filter

    NASA Astrophysics Data System (ADS)

    Tang, Caijie; Jiang, Yi

    2009-11-01

    An optical fiber Fabry-Pérot tunable filter is constructed by fixing two microlensed mirror-coated fibers to the opposite ends of a piezoelectric transducer. A tunable filter with a free spectral range of 70 nm, a finesse of 175, an insertion loss of 1.05 dB, and a tuning frequency exceeding 1 kHz has been experimentally demonstrated. The filter is easy to construct at a low cost, and it is anticipated that it will be used in fiber-optic sensing systems, spectrometers, and tunable optical fiber lasers.

  3. Influence of acoustic anisotropy in paratellurite on quasicollinear acousto-optic interaction.

    PubMed

    Mantsevich, S N; Balakshy, V I; Molchanov, V Ya; Yushkov, K B

    2015-12-01

    The influence of paratellurite acoustic anisotropy on the quasicollinear acousto-optic diffraction characteristics was examined. In the presented case the quasicollinear geometry of acousto-optic diffraction is realized with the use of acoustic beam reflection from one of the crystal surfaces. The simulations were based on the solution of acoustic beams propagation problem for anisotropic media previously presented in Balakshy and Mantsevich (2012). It is shown that media inhomogeneity affects the distribution of the acoustic energy in the ultrasound beam and the shape of wave fronts. The acoustic beam structure influences the characteristics of quasicollinear acousto-optic diffraction causing transformation of acousto-optic device transmission function shape and reducing the diffraction efficiency. PMID:26118495

  4. 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.

  5. 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.

  6. Precision laser spectroscopy using acousto-optic modulators

    SciTech Connect

    Van Wijngaarden, W.A.

    1996-12-31

    This paper reports on a new spectroscopic method that uses a frequency-modulated laser to excite an atomic beam. It has an especially promising future given the rapid technological advances in developing new relatively inexpensive acousto-optic and electro-optic modulators. Most significantly, this new method is free of various systematic effects that have limited the accuracy of past experiments. This chapter is organized as follows. Section II briefly reviews some of the advances made in optical spectroscopy during the last few decades. Principally, it discusses the use of Fabry-Perot etalons in conjunction with laser atomic beam spectroscopy. Interferometers have been extensively employed by numerous groups to determine many different kinds of frequency shifts. Section III describes three possible experimental arrangements using optically modulated laser beams to make frequency measurements. The advantages and limitations of these approaches are illustrated in Section IV by three specific examples of experiments that determined isotope shifts and hyperfine structure. Section V discusses some precision Stark shift measurements for optical transitions. It concludes with a summary of polarizability data having uncertainties of less than 0.5%. Sections IV and V also compare the results obtained using a variety of competing spectroscopic techniques. Finally, Section VI gives concluding remarks. 96 refs., 15 figs., 6 tabs.

  7. Electro-optic and acousto-optic laser beam scanners

    NASA Astrophysics Data System (ADS)

    Heberle, Johannes; Bechtold, Peter; Strauß, Johannes; Schmidt, Michael

    2016-03-01

    Electro-optical deflectors (EOD) and acousto-optical deflectors (AOD) are based on deflection of laser light within a solid state medium. As they do not contain any moving parts, they yield advantages compared to mechanical scanners which are conventionally used for laser beam deflection. Even for arbitrary scan paths high feed rates can be achieved. In this work the principles of operation and characteristic properties of EOD and AOD are presented. Additionally, a comparison to mirror based mechanical deflectors regarding deflection angles, speed and accuracy is made in terms of resolvable spots and the rate of resolvable spots. Especially, the latter one is up to one order of magnitude higher for EOD and AOD systems compared to conventional systems. Further characteristic properties such as response time, damage threshold, efficiency and beam distortions are discussed. Solid state laser beam deflectors are usually characterized by small deflection angles but high angular deflection velocities. As mechanical deflectors exhibit opposite properties an arrangement of a mechanical scanner combined with a solid state deflector provides a solution with the benefits of both systems. As ultrashort pulsed lasers with average power above 100 W and repetition rates in the MHz range have been available for several years this approach can be applied to fully exploit their capabilities. Thereby, pulse overlap can be reduced and by this means heat affected zones are prevented to provide proper processing results.

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

  9. Tunable rubidium excited state Voigt atomic optical filter.

    PubMed

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

    2016-03-21

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

  10. The nonreciprocal effect under low- and high-frequency collinear acousto-optic interactions

    NASA Astrophysics Data System (ADS)

    Dyakonov, E. A.; Voloshinov, V. B.; Nikitin, P. A.

    2012-12-01

    The nonreciprocal effect under collinear acousto-optic interaction in the low- and high-frequency regimes is studied theoretically. The magnitudes of nonreciprocity determined from the ultrasonic frequency and from the wavelength of light are shown to be quantitatively identical. An expression that governs the magnitude of the nonreciprocity and that is valid for both low- and high-frequency regimes of the collinear acousto-optic interaction is obtained. The shape and width of the frequency characteristic of the collinear acousto-optic interaction calculated in the low diffraction efficiency approximation are shown to be the same in the low- and high-frequency regimes. The dependence of the frequency bandwidth of the collinear acousto-optic interaction on the ultrasonic-wave attenuation and diffraction efficiency is obtained. The magnitude of the nonreciprocal effect in some of the crystals used in acousto-optics is estimated numerically. The nonreciprocity of the collinear interaction is shown to be substantially stronger in the high-frequency regime relative to the low-frequency regime. Sapphire is proved to be an optimal material for experimental realization of the nonreciprocal effect in the high-frequency regime.

  11. A liquid crystal tunable polarization filters for polarization imaging

    NASA Astrophysics Data System (ADS)

    Gu, Dong-Feng; Winker, Bruce; Wen, Bing; Mansell, John; Zachery, Karen; Taber, Donald; Chang, Tallis; Choi, Sung; Ma, Jian; Wang, Xiaomin; Sage, Keith

    2008-08-01

    We report a new familiy of polarimetric imaging cameras based on tunable liquid crystal components. Our camera designs use a dual frequency liquid crystal tunable filter that rotates the polarization of incoming light, in front of a single linear polarizer. The unique features of this approach include fast switching speed, high transmission throughput, no mechanical moving parts, broad bandwidth, high contrast ratio, wide viewing angle, and compact/monolithic architecture. This paper discusses these tunable liquid crystal polarimetric imaging camera architectures (time division, amplitude division), the benefits of our design, the analysis of laboratory and field data, and the applicability of polarization signatures in imaging.

  12. Analysis the processing algorithm for the frequency measurement variance of the acousto-optic spectrum analyzer

    NASA Astrophysics Data System (ADS)

    He, Qi-rui; Gan, Lu; Zhou, Ying; Gao, Chun-ming; Zhang, Xi-ren

    2015-08-01

    When the acousto-optic device worked on the Bragg model, the non-liner affected the diffraction beam. There were some errors between the diffraction beam deflection peak position and the input signal's frequency, which reduced the frequency measure accuracy of the acousto-optic spectrum analyzer. Under the existing optical experimental platform, we eliminated the CCD background noise by reducing the threshold firstly, and then we processed the data by four methods, the peak value method, the Gaussian fitting method, the squared cancroids method and the Hilbert transform method. The least frequency measure variance is 31.8 KHz2, the data processed by the Gaussian fitting method. It provides theoretical support for reducing the frequency measurement variance of acousto-optic spectrum analyzer.

  13. Acousto-optic fiber interferometer based on concatenated flexural wave modulation

    NASA Astrophysics Data System (ADS)

    Kang, Shouxin; Zhang, Hao; Liu, Bo; Zhang, Ning; Miao, Yinping

    2015-07-01

    An acousto-optic fiber interferometer has been proposed and experimentally demonstrated by employing two MgF2 sandwiches to implement concatenated flexural acoustic wave modulation onto single-mode optical fibers. The transmission spectrum of the acoustic grating pair has been experimentally investigated. Experimental results indicate that interferometric spectral fringes possess a frequency sensitivity as large as -499.0 nm/MHz due to the Mach-Zehnder interference. Moreover, the applied radio frequency signal voltage for flexural wave generation has a great impact on the transmission spectral properties. The work presented would be of importance for the understanding of the acousto-optic interaction mechanism in concatenated acoustic fiber gratings and is helpful for the design of related acousto-optic fiber devices.

  14. Transformation of phase dislocations under acousto-optic interaction of optical and acoustical Bessel beams

    NASA Astrophysics Data System (ADS)

    Belyi, V. N.; Khilo, P. A.; Kazak, N. S.; Khilo, N. A.

    2016-07-01

    The generation of wavefront phase dislocations of vortex Bessel light beams under acousto-optic (AO) diffraction in uniaxial crystals has been investigated. For the first time the process of AO interaction is studied with participation of Bessel acoustic beams instead of plane waves. A mathematical description of AO interaction is provided, which supposes the satisfaction of two types of phase-matching condition. The acousto-optic processes of transferring optical singularities onto the wavefront of BLBs are investigated and the generation of high-order optical vortices is considered at the interaction of optical and acoustical Bessel beams. The change of Bessel function order or phase dislocation order is explained as a result of the spin–orbital interaction under acousto-optic diffraction of vortex Bessel beams.

  15. 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)

  16. Influence of acoustic anisotropy of paratellurite crystal on the double acousto-optic Bragg light scattering

    NASA Astrophysics Data System (ADS)

    Zakharov, A. V.; Voloshinov, V. B.

    2016-09-01

    Influence of acoustic anisotropy on acousto-optic interaction in optically and acoustically anisotropic media is theoretically and experimentally studied. A specific type of acousto-optic diffraction is analyzed with allowance for the phase-matching conditions for two diffraction maxima. Analytical expressions for the phase-mismatch parameters versus the angle between the phase and group velocities of acoustic wave are derived. Light intensity in the diffraction peaks is numerically calculated, and experimental data on the diffraction in the paratellurite crystal at an acoustic walk-off angle of 54° are presented.

  17. Integrated acousto-optic mode locking device for a mode locked laser system

    SciTech Connect

    Myslinski, P.

    1988-04-05

    An integrated acousto-optic mode locker is described comprising: a laser medium having first and second ends and a longitudinal axis; an excitation source for producing a population inversion in the medium; an acoustic-optic modulator mounted along the longitudinal axis of the laser medium and placed in close proximity to a first end of the laser medium; an output mirror mounted close to a second end to the laser medium and constituting together with the acoustic-optic modulator an optical resonator having an optical axis and an optical path of length L; means for controlling and maintaining the temperature of the acousto-optic modulator.

  18. 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.

  19. Matrix/vector multiplication by use of a two-dimensional multichannel acousto-optic device

    NASA Astrophysics Data System (ADS)

    He, Shiya; Zhao, Qida; Yu, Kuanxin; Liu, Wei; Liu, Deguo; Shu, Xuesui

    1998-08-01

    The method to perform matrix/vector multiplication using the acousto-optic (AO) processor has been studded in some earlier publications. This processing architecture provides high speed and high accuracy calculation. However, in the system, two AO devices must be used. For this reason, the optical couple between the two devices has to be adjusted carefully. It will cause the inconvenience and unsteadiness. A novel two- dimensional multichannel acousto-optic device is presented in this paper. By use of this kind of device, the trouble which the earlier architecture suffered from is got rid of and the experiment system is simplified.

  20. 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.

  1. All-fiber widely tunable thulium laser

    NASA Astrophysics Data System (ADS)

    Stevens, G.; Legg, T.

    2016-03-01

    We present results from an all-fibre thulium laser system that can be tuned to any wavelength between 1710 - 2110 nm, without using any moving mechanical parts. An Acousto-Optic Tunable Filter (AOTF) is used as the tuning element, which allows for the wavelength to be tuned in ~ 20 μs. Core-pumped and cladding pumped thulium fibres are used to enable lasing action across the wavelength range. We use in-house fabricated fused fibre couplers and combiners that have a flattened coupling response with wavelength to allow for the system to be built in an all fibre design. These couplers have a coupling response that only varies by +/- 10% over the 400 nm operating range. The laser can output powers between 1-5 mW over 1710 - 2110 nm and has a linewidth of <0.2 nm. An Acousto-optic modulator is used as a switch on the output of the laser to switch the signal between core-pumped and cladding-pumped amplifier stages. This allows for the output signals to be amplified to ~1W levels.

  2. 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

  3. The Brazilian Tunable Filter Imager for the SOAR Telescope

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  4. Two-cascade acousto-optic dispersive delay line for ultrashort laser pulses

    SciTech Connect

    Molchanov, V Ya; Chizhikov, S I; Yushkov, K B

    2011-08-31

    An optical dispersive delay line for controlling the spectral composition and phase of ultrashort laser pulses is considered. To control independently the spectral amplitude and spectral phase of pulses, it is proposed to use the cascade arrangement of two acousto-optic cells with different control signals. (letters)

  5. 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.

  6. Influence of Acoustic Field Structure on Polarization Characteristics of Acousto-optic Interaction in Crystals

    NASA Astrophysics Data System (ADS)

    Muromets, A. V.; Trushin, A. S.

    Influence of acoustic field structure on polarization characteristics of acousto-optic interaction is investigated. It is shown that inhomogeneity of acoustic field and mechanism of ultrasound excitation causes changes in values of acousto-optic figure of merit for ordinary and extraordinary light beams in comparison with theoretic values. The theoretic values were derived under assumption that acoustic wave is homogeneous. Experimental analysis was carried out in acousto-optic cell based on lithium niobate crystal where the acoustic wave propagates at the angle 13 degrees to Z axis of the crystal. We used three different methods of ultrasound generation in the crystal: by means of external piezotransducer, by interdigital transducer and by two sets of electrodes placed on top of the crystal surface. In the latter case, the first pair of the electrodes was directed along X crystal axis, while the second pair of the electrodes was directed orthogonally to X crystal axis and the direction of ultrasound. Obtained values for diffraction efficiencies for ordinary and extraordinary polarized optical beams were qualitatively different which may be caused by spatial inhomogeneity of the generated acoustic waves in the crystal. Structure of acoustic field generated by these sets of electrodes was examined by laser probing. We performed the analysis of the acoustic field intensity using acousto-optic method. A relation of diffraction efficiencies for ordinary and extraordinary light waves was measured during each iteration of the laser probing.

  7. Integrated optic a.d. convertor based on bulk acousto-optic interaction

    NASA Astrophysics Data System (ADS)

    Gottlieb, M.; Brandt, G. B.

    1980-05-01

    A method is described using integrated optics to perform high data rate a.d. conversion. The approach uses the bulk acousto-optic interaction in optical waveguides, with a segmented transducer array to deflect light in response to an analogue signal applied to phase-shifting elements at the transducer.

  8. Acousto-optic modulator as an electronically selectable unidirectional device in a ring laser

    SciTech Connect

    Roy, R.; Schulz, P.A.; Walther, A.

    1987-09-01

    An acousto-optic modulator causes undirectional operation of dye and Ti:sapphire ring lasers. The modulator has a low insertion loss in the cavity and can be used to switch the direction of the beam electronically. The ring laser performance is characterized, and experiments to probe the origin of the unidirectional operation are described.

  9. 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.

  10. Tunable bandpass filter with variable selectivity

    NASA Technical Reports Server (NTRS)

    Kerwin, W. J.; Shaffer, C. V.

    1969-01-01

    Basic active RC networks constructed from stages that realize second-order transfer functions using two integrators offer excellent stability. Modifications of the basic network produce a highly stable bandpass filter having separate controls that independently adjust center frequency, Q, and center frequency gain.

  11. NEMS-based MIM plasmonics tunable filter

    NASA Astrophysics Data System (ADS)

    Khirallah, Kareem; Swillam, Mohamed A.

    2016-03-01

    Designing a miniaturized and efficient optical filter which can be actively tuned is a modern engineering challenge. This paper propose a design of a device with a nano scale size for active tuning the resonance frequency of a metal-insulator-metal plasmonics optical filter. The design is based on controlling the relative position between two stubs in metal-Insulator-metal plasmonics waveguide using NEMS technology. The mechanical design parameter is chosen carefully to be compatible with modern fabrication technology and a reasonable fabrication process of the device is proposed. The analysis of the mechanical and optical design is done and shows a promising performance. For the chosen mechanical design parameters, the optical resonance wavelength can be tuned from 1.45μm to 1.65μm using 7VDC actuation voltage.

  12. 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.

  13. 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.

  14. 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.

  15. Tunable filter using ferroelectric-dielectric periodic multilayer.

    PubMed

    D'souza, Nirmala Maria; Mathew, Vincent

    2015-03-20

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

  16. 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.

  17. Tunable high-q superconducting notch filter

    DOEpatents

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

    1979-11-29

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

  18. 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

  19. Tandem-pulsed acousto-optics: an analytical framework of modulated high-contrast speckle patterns.

    PubMed

    Resink, S G; Steenbergen, W

    2015-06-01

    Recently we presented acousto-optic (AO) probing of scattering media using addition or subtraction of speckle patterns due to tandem nanosecond pulses. Here we present a theoretical framework for ideal (polarized, noise-free) speckle patterns with unity contrast that links ultrasound-induced optical phase modulation, the fraction of light that is tagged by ultrasound, speckle contrast, mean square difference of speckle patterns and the contrast of the summation of speckle patterns acquired at different ultrasound phases. We derive the important relations from basic assumptions and definitions, and then validate them with simulations. For ultrasound-generated phase modulation angles below 0.7 rad (assuming uniform modulation), we are now able to relate speckle pattern statistics to the acousto-optic phase modulation. Hence our theory allows quantifying speckle observations in terms of ultrasonically tagged fractions of light for near-unity-contrast speckle patterns.

  20. Breakdown of the linear acousto-optic interaction regime in phoxonic cavities.

    PubMed

    Almpanis, Evangelos; Papanikolaou, Nikolaos; Stefanou, Nikolaos

    2014-12-29

    The limits of validity of the linear photoelastic model are investigated in a one-dimensional dual photonic-phononic cavity, formed by alternating layers of a chalcogenide glass and a polymer homogeneous and isotropic material, which supports both optical and acoustic resonant modes localized in the same region. It is shown that the linear-response regime breaks down when either the acoustic excitation increases or the first-order acousto-optic interaction coupling element vanishes by symmetry, giving rise to the manifestation of multiphonon absorption and emission processes by a photon. Our results provide a consistent interpretation of different aspects of the underlying physics relating to nonlinear acousto-optic interactions that can occur in such cavities. PMID:25607131

  1. 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.

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

    PubMed

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

    2012-11-01

    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. PMID:23206109

  3. Mode conversion based on the acousto-optical interaction in photonic-phononic waveguide

    NASA Astrophysics Data System (ADS)

    Chen, Guodong; Zhang, Ruiwen; Xiong, Huang; Xie, Heng; Gao, Ya; Feng, Danqi; Sun, Junqiang

    2015-02-01

    We present a scheme for on-chip optical mode conversion in a hybrid photonic-phononic waveguide. Both propagating optical and acoustic wave can be tightly confined in the hybrid waveguide, and the acoustooptical interaction can be enhanced to realize optical mode conversion within a chip-scale size. The theoretical model of the acousto-optic interaction is established to explain the mode conversion. The numerical simulation results indicate that the high efficient mode conversion can be achieved by adjusting the intensity of the acoustic wave. We also show that the mode conversion bandwidth can be dramatically broadened to 13 THz by adjusting the frequency of the acoustic wave to match phase condition of the acousto-optic interaction. This mode converter on-chip is promising in order to increase the capacity of silicon data busses for on-chip optical interconnections.

  4. 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.

  5. Fast spatial beam shaping by acousto-optic diffraction for 3D non-linear microscopy.

    PubMed

    Akemann, Walther; Léger, Jean-François; Ventalon, Cathie; Mathieu, Benjamin; Dieudonné, Stéphane; Bourdieu, Laurent

    2015-11-01

    Acousto-optic deflection (AOD) devices offer unprecedented fast control of the entire spatial structure of light beams, most notably their phase. AOD light modulation of ultra-short laser pulses, however, is not straightforward to implement because of intrinsic chromatic dispersion and non-stationarity of acousto-optic diffraction. While schemes exist to compensate chromatic dispersion, non-stationarity remains an obstacle. In this work we demonstrate an efficient AOD light modulator for stable phase modulation using time-locked generation of frequency-modulated acoustic waves at the full repetition rate of a high power laser pulse amplifier of 80 kHz. We establish the non-local relationship between the optical phase and the generating acoustic frequency function and verify the system for temporal stability, phase accuracy and generation of non-linear two-dimensional phase functions. PMID:26561090

  6. Measurement of isotope shifts and hyperfine splittings of ytterbium by means of acousto-optic modulation

    SciTech Connect

    van Wijngaarden, W.A.; Li, J.

    1994-11-01

    The isotope and hyperfine shifts for the Yb {sup 1}{ital S}{sub 0}(6{ital s}{sup 2}){r_arrow}{sup 3}{ital P}{sub 1}(6{ital s}6{ital p}) transition were determined with an acousto-optic modulator used to frequency shift part of a laser beam. The frequency-shifted and -unshifted laser beams were superimposed and excited an atomic beam. The laser was scanned across the transition while fluorescence produced by the radiative decay of the excited state was detected by a photomultiplier. Each isotope generated two peaks in the spectrum separated by the acousto-optic shift, which permitted the frequency to be calibrated. This relatively simple method yields results that agree well with the most accurate existing data, which were obtained by measurement of frequency shifts with a Fabry--Perot etalon whose length was stabilized with a helium--neon laser locked to an iodine line.

  7. Tandem-pulsed acousto-optics: an analytical framework of modulated high-contrast speckle patterns.

    PubMed

    Resink, S G; Steenbergen, W

    2015-06-01

    Recently we presented acousto-optic (AO) probing of scattering media using addition or subtraction of speckle patterns due to tandem nanosecond pulses. Here we present a theoretical framework for ideal (polarized, noise-free) speckle patterns with unity contrast that links ultrasound-induced optical phase modulation, the fraction of light that is tagged by ultrasound, speckle contrast, mean square difference of speckle patterns and the contrast of the summation of speckle patterns acquired at different ultrasound phases. We derive the important relations from basic assumptions and definitions, and then validate them with simulations. For ultrasound-generated phase modulation angles below 0.7 rad (assuming uniform modulation), we are now able to relate speckle pattern statistics to the acousto-optic phase modulation. Hence our theory allows quantifying speckle observations in terms of ultrasonically tagged fractions of light for near-unity-contrast speckle patterns. PMID:25985079

  8. Comparison of real-time acousto-optic SAR (synthetic aperture radar) processor architectures

    SciTech Connect

    Stalker, K.T.; Dickey, F.M.; Molley, P.A.

    1987-08-01

    A comparison of real-time acousto-optic processors for synthetic aperture radar (SAR) image formation has been performed. These processors take advantage of the high processing speed and large time bandwidth product of acousto-optic devices (AOD's) in combination with the multichannel correlation capability of charge coupled devices (CCD) to form the SAR image in real time. They offer significant size, weight and power consumption advantages compared to conventional optical or digital processors. Architectures utilizing both spatial carriers and subtraction schemes for elimininating the unwanted bias terms have been analyzed. Also, multichannel architectures for complex (quadrature) processing have been addressed. In addition to imaging performance, the impact of these approaches on system complexity, real-time processing speed and required component capabilities are discussed. Results from both our analysis and the experimental implementation of a selected group of these architectures are presented. 8 refs., 5 figs., 1 tab.

  9. Independent acousto-optic separation of the two wavelengths of a polychromatic light beam

    NASA Astrophysics Data System (ADS)

    Kastelik, J. C.; Gazalet, Marc G.; Haine, F.; Pommeray, Michel

    1997-02-01

    A special configuration based on two successive acousto- optic interactions in uniaxial crystals with two noncollinear acoustic waves is presented. It leads to two angularly split wavelengths from a multiline laser beam with independent acousto-optic efficiencies. General expressions of the angular deviation and the spectral bandwidth are derived. Since the application concerns the restitution of colored images, a novel combination of wavelengths using the blue primary at 458 nm is investigated for trichromatic color matching. Numerical computations have been drawn for paratellurite. A practical separator using the slow shear wave in paratellurite is designed, and experimental results for the independent separation of 514- and 458-nm wavelengths of an Ar laser are reported.

  10. Fast spatial beam shaping by acousto-optic diffraction for 3D non-linear microscopy.

    PubMed

    Akemann, Walther; Léger, Jean-François; Ventalon, Cathie; Mathieu, Benjamin; Dieudonné, Stéphane; Bourdieu, Laurent

    2015-11-01

    Acousto-optic deflection (AOD) devices offer unprecedented fast control of the entire spatial structure of light beams, most notably their phase. AOD light modulation of ultra-short laser pulses, however, is not straightforward to implement because of intrinsic chromatic dispersion and non-stationarity of acousto-optic diffraction. While schemes exist to compensate chromatic dispersion, non-stationarity remains an obstacle. In this work we demonstrate an efficient AOD light modulator for stable phase modulation using time-locked generation of frequency-modulated acoustic waves at the full repetition rate of a high power laser pulse amplifier of 80 kHz. We establish the non-local relationship between the optical phase and the generating acoustic frequency function and verify the system for temporal stability, phase accuracy and generation of non-linear two-dimensional phase functions.

  11. Wave-theory analysis of acousto-optic Bragg diffraction image formation.

    PubMed

    Mehrl, D J; Liu, Z C; Korpel, A

    1993-09-10

    We analyze anastigmatic Bragg diffraction imaging by use of an efficient numerical method that makes use of a plane-wave spectrum formalism applicable to weak acousto-optic diffraction involving threedimensional light and sound fields. Results from this wave-theory analysis are compared with previous results derived on the basis of ray theory, and are shown to be in good agreement, thus corroborating the validity of both techniques.

  12. Effect of group velocity mismatch on acousto-optic interaction of ultrashort laser pulses

    SciTech Connect

    Yushkov, K B; Molchanov, V Ya

    2011-12-31

    Equations describing acousto-optic diffraction of ultrashort laser pulses in an anisotropic medium are derived, taking into account the group velocity mismatch of optical eigenmodes. It is shown that the solution of the modified coupled-mode equations taking into account the group delay is characterised by an increase in the pulse duration, a decrease in diffraction efficiency, a change in the shape of the wave packet envelope, as well as by an increase in the width of the transmission function.

  13. System for linear control and stabilization of laser radiation power by an acousto-optic modulator

    SciTech Connect

    Poleshchuk, A.G.; Khimich, A.K.

    1980-09-01

    This paper presents the results of the development and testing of an acousto-optic modulator control system and describes the operating principle of its circuit. The range of linear light flux power control is greater by a factor of 1000, the relative error is less than 1%, the operating frequency bandwidth is 0--250 kHz, and the decrease in the amplitude of the laser power fluctuations is a factor of 100.

  14. An acousto-optic image correlator with a throughput rate of 1000 templates per second

    SciTech Connect

    Molley, P.A.

    1990-03-28

    A two dimensional image correlator based on acousto-optic (AO) and charge-coupled devices (CCDs) is described that can be built with existing technology to provide 1000 frames per second operation. In recent years, architectures have been developed that perform the two dimensional correlation utilizing one dimensional input devices. The input scene is loaded into the acousto-optic device (AOD) one line at time. This line is then correlated against all of the rows of a reference template introduced into the optical system using a one dimensional array of LEDs or laser diodes. However, it generally takes a much greater time to load the AO cell than it does to process the information. this latency time severely limits the maximum throughput rate of the processor. This paper introduces a new acousto-optic correlator implementation that overcomes this bottleneck so that processing can occur close to 100% of the time. A grayscale image correlator is proposed that can be built using present technology that can realistically achieve throughput rates on the order of 10{sup 12} operations per second. This translates to over 1000 correlations per second for input scenes with dimensions of 512 {times} 512 pixels and reference templates of size 64 {times} 64 pixels. 10 refs., 4 figs.

  15. 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.

  16. 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.

  17. Tunable band-pass plasmonic waveguide filters with nanodisk resonators.

    PubMed

    Lu, Hua; Liu, Xueming; Mao, Dong; Wang, Leiran; Gong, Yongkang

    2010-08-16

    A novel and simple plasmonic filter based on metal-insulator-metal plasmonic waveguides with a nanodisk resonator is proposed and investigated numerically. By the resonant theory of disk-shaped nanocavity, we find that the resonance wavelengths can be easily manipulated by adjusting the radius and refractive index of the nanocavity, which is in good agreement with the results obtained by finite-difference time-domain (FDTD) simulations. In addition, the bandwidths of resonance spectra are tunable by changing the coupling distance between the nanocavity and waveguides. This result achieved by FDTD simulations can be accurately analyzed by temporal coupled mode theory. Our filters have important potential applications in high-density plasmonic integration circuits.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. Fourier transform acousto-optic imaging with a custom-designed CMOS smart-pixels array.

    PubMed

    Barjean, Kinia; Contreras, Kevin; Laudereau, Jean-Baptiste; Tinet, Éric; Ettori, Dominique; Ramaz, François; Tualle, Jean-Michel

    2015-03-01

    We report acousto-optic imaging (AOI) into a scattering medium using a Fourier Transform (FT) analysis to achieve axial resolution. The measurement system was implemented using a CMOS smart-pixels sensor dedicated to the real-time analysis of speckle patterns. This first proof-of-principle of FT-AOI demonstrates some of its potential advantages, with a signal-to-noise ratio comparable to the one obtained without axial resolution, and with an acquisition rate compatible with a use on living biological tissue.

  3. Multiplication of the frequency shift of optical radiation by means of cascade acousto-optic interaction

    SciTech Connect

    Kotov, V M

    2000-04-30

    A method for increasing the frequency shift of optical radiation by means of cascade acousto-optic diffraction of light is proposed and studied. The method is based on special features of anisotropic diffraction in an anisotropic medium and optical properties of gyrotropic media. Five-cascade diffraction of radiation from a He - Ne laser ({lambda}=0.633 {mu}m) in a TeO{sub 2} single crystal with an efficiency of 8% was obtained experimentally. (laser applications and other topics in quantum electronics)

  4. 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.

  5. High-frequency acousto-optic mode locker for picosecond pulse generation

    SciTech Connect

    Keller, U.; Li, K.D.; Khuri-Yakub, P.T.; Bloom, D. ); Gerstenberger, D.C.; Weingarten, K.J. )

    1990-01-01

    We modeled, designed, and built a 500-MHz acousto-optic mode locker with a diffraction efficiency of 28% per 1 W drive power. The transducer is zinc oxide sputtered onto a sapphire substrate. A new figure of merit is defined for the mode-locker design, which indicates that sapphire is a good substrate material. Pulse widths of less than 10 psec with an average power of 150 mW were achieved from a 500-MHz pulse-rate, diode-pumped, cw mode-locked Nd:YLF laser using a pump power of 700 mW.

  6. Anisotropic acousto-optic interaction in tellurium crystal with acoustic walk-off.

    PubMed

    Balakshy, Vladimir; Voloshin, Andrey

    2016-06-10

    The influence of the acoustic beam energy walk-off on characteristics of anisotropic Bragg diffraction of light is studied theoretically by the example of a tellurium single crystal. Calculations for wide ranges of Bragg angles and ultrasound frequencies are produced on the basis of an original solution of the acousto-optic (AO) interaction problem, which takes into consideration the acoustic walk-off. It is established that the walk-off can substantially change the region of AO interaction, resulting in narrowing or broadening of the frequency characteristic depending on the crystal cut, acoustic frequency, incident light polarization, and walk-off angle sign. PMID:27409010

  7. 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

  8. Monolithic Fabry-Perot Wavelength Tunable Filter with Electrothermal Actuation

    NASA Astrophysics Data System (ADS)

    Kim, Chang Kyu; Lee, Myung Lae; Jun, Chi-Hoon; Choi, Chang Auck

    2005-02-01

    We report on a micromachined monolithic Fabry-Perot wavelength tunable filter with a thick moving structure operated by an electrothermal actuation. The monolithic structure simplifies the fabrication process and the electrothermal actuation mechanism reduces the required operation voltage. For the wet etching of the AlGaAs sacrificial layer, an HCl-based solution rather than a HF-based one was used because it results in a larger selectivity between the AlxGa1-xAs layers and less damage to the suspended structure. The wavelength tuning range of the 7.64-μm-thick structure was 47 nm for the power consumption of 5 mW, which results in the high tuning efficiency of ˜9.9 nm/mW. The wide tuning range of 81.2 nm for the 5.2-μm-thick structure, that is not possible with an electrostatic actuation mechanism due to the occurrence of breakdown, is achieved at the driving voltage below 5.7 V. Due to the simplicity of fabrication and the ease of integration, this structure is advantageous for use in wavelength tunable light sources and photodetectors.

  9. 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.

  10. 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.

  11. 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

  12. Optically tunable acoustic wave band-pass filter

    SciTech Connect

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

    2014-12-15

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

  13. Optically tunable acoustic wave band-pass filter

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  14. Analysis and design of tunable fiber Fabry-Perot filter

    NASA Astrophysics Data System (ADS)

    Qi, Haibing; Yu, Yonglin

    2008-12-01

    The effective reflectivity of planar tunable filter fiber Fabry-Perot (TF-FFP) caused by coupling losses would led to the change of tuning range and the full width half maximum (FWHM) in the process of gap distance tuning. The general transfer function expression of FFP is developed by Gaussian beams model and coupling losses. A method that is by appropriate unsymmetrical reflectivity of fiber end can increase the tuning range and reduce the FWHM is proposed, the obtained parameters may be useful for the analysis and design of other TF-FFP. At last the initial gap position and reflectivities of both ends of TF-FFP are designed theoretically for C-band and C+L-band respectively.

  15. Tunable semiconductor laser at 1025-1095 nm range for OCT applications with an extended imaging depth

    NASA Astrophysics Data System (ADS)

    Shramenko, Mikhail V.; Chamorovskiy, Alexander; Lyu, Hong-Chou; Lobintsov, Andrei A.; Karnowski, Karol; Yakubovich, Sergei D.; Wojtkowski, Maciej

    2015-03-01

    Tunable semiconductor laser for 1025-1095 nm spectral range is developed based on the InGaAs semiconductor optical amplifier and a narrow band-pass acousto-optic tunable filter in a fiber ring cavity. Mode-hop-free sweeping with tuning speeds of up to 104 nm/s was demonstrated. Instantaneous linewidth is in the range of 0.06-0.15 nm, side-mode suppression is up to 50 dB and polarization extinction ratio exceeds 18 dB. Optical power in output single mode fiber reaches 20 mW. The laser was used in OCT system for imaging a contact lens immersed in a 0.5% intra-lipid solution. The cross-section image provided the imaging depth of more than 5mm.

  16. 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.

  17. Laser communication system with acousto-optic tracking and modulation: experimental study

    NASA Astrophysics Data System (ADS)

    Nikulin, Vladimir V.; Sofka, Jozef

    2009-12-01

    Laser communication systems are highly preferred for broadband applications. This technology uses higher regions of the spectrum, and offers unsurpassed throughput, information security, reduced weight and size of the components, and power savings. Unfortunately, small beam divergence requires precise positioning, which becomes very critical at high data rates. Complex motion patterns of the communicating platforms, vibrations, and atmospheric effects cause significant signal losses due to the pointing errors, beam wander, and other higher order effects. Mitigation of those effects is achieved by fast tracking, which can be successfully combined with signal modulation. In this work, we focus on the application of acousto-optic technology and its effect on communication performance. We present experimental results for a laser communication link affected by pointing distortions. These distortions are generated to emulate specific operation environments with particular spectral characteristics. The acousto-optic technology is used to build an agile tracking system combined with signal modulation in the same device to assure maximum signal reception, in spite of the harsh operational conditions. The received communication signal is recorded and statistically analyzed to calculate the bit error rates. This work presents synthesis of a tracking system and experimental results characterizing the communication performance under uncompensated pointing disturbance and with tracking.

  18. Research on FBG-based longitudinal-acousto-optic modulator with Fourier mode coupling method.

    PubMed

    Li, Zhuoxuan; Pei, Li; Liu, Chao; Ning, Tigang; Yu, Shaowei

    2012-10-20

    Fourier mode coupling model was first applied to achieve the spectra property of a fiber Bragg grating (FBG)-based longitudinal-acousto-optic modulator. Compared with traditional analysis algorithms, such as the transfer matrix method, the Fourier mode coupling model could improve the computing efficiency up to 100 times with a guarantee of accuracy. In this paper, based on the theoretical analysis of this model, the spectra characteristics of the modulator in different frequencies and acoustically induced strains were numerically simulated. In the experiment, a uniform FBG was modulated by acoustic wave (AW) at 12 different frequencies. In particular, the modulator responses at 563 and 885.5 KHz with three different lead zirconate titanate (PZT) loads applied were plotted for illustration, and the linear fitting of experimental data demonstrated a good match with the simulation result. The acoustic excitation of the longitudinal wave is obtained using a conic silica horn attached to the surface of a shear-mode PZT plate paralleled to the fiber axis. This way of generating longitudinal AW with a transversal PZT may shed light on the optimal structural design for the FBG-based longitudinal-acousto-optic modulator.

  19. 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. PMID:22559541

  20. Dynamic wavefront shaping with an acousto-optic lens for laser scanning microscopy.

    PubMed

    Konstantinou, George; Kirkby, Paul A; Evans, Geoffrey J; Naga Srinivas Nadella, K M; Griffiths, Victoria A; Mitchell, John E; Angus Silver, R

    2016-03-21

    Acousto-optic deflectors (AODs) arranged in series and driven with linearly chirped frequencies can rapidly focus and tilt optical wavefronts, enabling high-speed 3D random access microscopy. Non-linearly chirped acoustic drive frequencies can also be used to shape the optical wavefront allowing a range of higher-order aberrations to be generated. However, to date, wavefront shaping with AODs has been achieved by using single laser pulses for strobed illumination to 'freeze' the moving acoustic wavefront, limiting voxel acquisition rates. Here we show that dynamic wavefront shaping can be achieved by applying non-linear drive frequencies to a pair of AODs with counter-propagating acoustic waves, which comprise a cylindrical acousto-optic lens (AOL). Using a cylindrical AOL we demonstrate high-speed continuous axial line scanning and the first experimental AOL-based correction of a cylindrical lens aberration at 30 kHz, accurate to 1/35th of a wave at 800 nm. Furthermore, we develop a model to show how spherical aberration, which is the major aberration in AOL-based remote-focusing systems, can be partially or fully corrected with AOLs consisting of four or six AODs, respectively. PMID:27136821

  1. Dynamic two-dimensional refractive index modulation for high performance acousto-optic deflector.

    PubMed

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

    2015-12-28

    The performance of an acousto-optic deflector is studied for two-dimensional refractive index that varies as periodic and sinc functions in the transverse and longitudinal directions, respectively, with respect to the direction of light propagation. Phased array piezoelectric transducers can be operated at different phase shifts to produce a two-dimensionally inhomogeneous domain of phase grating in the acousto-optic media. Also this domain can be steered at different angles by selecting the phase shift appropriately. This mechanism of dynamically tilting the refractive index-modulated domain enables adjusting the incident angle of light on the phase grating plane without moving the light source. So the Bragg angle of incidence can be always achieved at any acoustic frequency, and consequently, the deflector can operate under the Bragg diffraction condition at the optimum diffraction efficiency. Analytic solutions are obtained for the Bragg diffraction of plane waves based on the second order coupled mode theory, and the diffraction efficiency is found to be unity for optimal index modulations at certain acoustic parameters. PMID:26832030

  2. Laser heterodyne method of shift measurement using acousto-optic interaction

    SciTech Connect

    Teleshevskii, V.I.

    1985-04-01

    Heterodyne methods of optical-field detection using acousto-optic interaction (AOI) have gained use in optical and acoustical holography, optical interferometry and interference microscopy, and ultrasonics. These methods detect the amplitude and phase at each point of the optical field at a given carrier frequency and, in conjunction with scanning, recover the wave fronts scattered by an object. This paper examines another heterodyne method of acoustooptic conversion of light-wave phase shift in which AOI is accomplished at the output of the interference system. The described method allows a differential scheme for conversion of light-wave phase shifts which increases stability and doubles sensitivity. This is a two-channel system and has an electrical reference signal that is formed by acousto-optic conversion in transillumination of the point of the acoustic grating as the measuring signal. The proposed method has provided a basis for designing and putting into serial production laser meters with displacement ranges of up to 10 m and up to 30 m and with discreteness to 0.01 micrometers.

  3. A high dynamic range acousto-optic image correlator for real-time pattern recognition

    SciTech Connect

    Molley, P.A.; Stalker, K.T.

    1988-01-01

    The architecture and experimental results for an incoherent acousto-optic image correlator suitable for real-time applications are presented. In the basic architecture, each time a line of the raster scanned input image is fed into the acousto-optic device (AOD), all rows of a digitally stored reference image are read into the system using an array of light emitting diodes (LED's). Thus, the required two-dimensional correltaion is performed as a series of multi-channel 1-D time-integrations in x (performed in the AOD) combined with a multi-channel correlation in y (perpendicular to the AOD axis) using a modified CCD. The LED array and detector modifications which markedly increase the dynamic range are discussed as well as correlator design. Further, a novel memory for storing the reference object is described for rapidly changing templates. Experimental results indicate the architecture is useful for applications in the areas of character recognition and target identification. 8 refs., 8 figs.

  4. Ultrafast random-access scanning in two-photon microscopy using acousto-optic deflectors.

    PubMed

    Salomé, R; Kremer, Y; Dieudonné, S; Léger, J-F; Krichevsky, O; Wyart, C; Chatenay, D; Bourdieu, L

    2006-06-30

    Two-photon scanning microscopy (TPSM) is a powerful tool for imaging deep inside living tissues with sub-cellular resolution. The temporal resolution of TPSM is however strongly limited by the galvanometric mirrors used to steer the laser beam. Fast physiological events can therefore only be followed by scanning repeatedly a single line within the field of view. Because acousto-optic deflectors (AODs) are non-mechanical devices, they allow access at any point within the field of view on a microsecond time scale and are therefore excellent candidates to improve the temporal resolution of TPSM. However, the use of AOD-based scanners with femtosecond pulses raises several technical difficulties. In this paper, we describe an all-digital TPSM setup based on two crossed AODs. It includes in particular an acousto-optic modulator (AOM) placed at 45 degrees with respect to the AODs to pre-compensate for the large spatial distortions of femtosecond pulses occurring in the AODs, in order to optimize the spatial resolution and the fluorescence excitation. Our setup allows recording from freely selectable point-of-interest at high speed (1kHz). By maximizing the time spent on points of interest, random-access TPSM (RA-TPSM) constitutes a promising method for multiunit recordings with millisecond resolution in biological tissues.

  5. Spectral radiance source based on supercontinuum laser and wavelength tunable bandpass filter: the spectrally tunable absolute irradiance and radiance source.

    PubMed

    Levick, Andrew P; Greenwell, Claire L; Ireland, Jane; Woolliams, Emma R; Goodman, Teresa M; Bialek, Agnieszka; Fox, Nigel P

    2014-06-01

    A new spectrally tunable source for calibration of radiometric detectors in radiance, irradiance, or power mode has been developed and characterized. It is termed the spectrally tunable absolute irradiance and radiance source (STAIRS). It consists of a supercontinuum laser, wavelength tunable bandpass filter, power stabilization feedback control scheme, and output coupling optics. It has the advantages of relative portability and a collimated beam (low étendue), and is an alternative to conventional sources such as tungsten lamps, blackbodies, or tunable lasers. The supercontinuum laser is a commercial Fianium SC400-6-02, which has a wavelength range between 400 and 2500 nm and a total power of 6 W. The wavelength tunable bandpass filter, a PhotonEtc laser line tunable filter (LLTF), is tunable between 400 and 1000 nm and has a bandwidth of 1 or 2 nm depending on the wavelength selected. The collimated laser beam from the LLTF filter is converted to an appropriate spatial and angular distribution for the application considered (i.e., for radiance, irradiance, or power mode calibration of a radiometric sensor) with the output coupling optics, for example, an integrating sphere, and the spectral radiance/irradiance/power of the source is measured using a calibration optical sensor. A power stabilization feedback control scheme has been incorporated that stabilizes the source to better than 0.01% for averaging times longer than 100 s. The out-of-band transmission of the LLTF filter is estimated to be < -65 dB (0.00003%), and is sufficiently low for many end-user applications, for example the spectral radiance calibration of earth observation imaging radiometers and the stray light characterization of array spectrometers (the end-user optical sensor). We have made initial measurements of two end-user instruments with the STAIRS source, an array spectrometer and ocean color radiometer.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  7. 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.

  8. The Plane Wave Spectrum in Acousto-Optic Imaging of Ultrasonic Fields.

    NASA Astrophysics Data System (ADS)

    Mehrl, David Joseph

    This thesis takes an in-depth look at two major areas of acousto-optics: Bragg diffraction imaging and Schlieren imaging. Both of these methods relate to the imaging of ultrasonic sound fields. The latter method is particularly relevant as it forms the basis for many practical signal processing schemes. A review of the angular plane wave spectrum concept is followed by an outline of a three-dimensional acousto -optic interaction formalism. This formalism forms the basis for the wave-theory analyses of Bragg diffraction and Schlieren imaging which are undertaken in later chapters. A ray tracing method, applicable to acousto-optic scattering, is also developed and justified on the basis of eikonal theory. Bragg diffraction imaging is analyzed by means of both ray tracing and wave theory methods, and the results are shown to be in mutual agreement. Also discussed are the development and results of a computer program which generates three-dimensional ray tracings that depict various Bragg diffraction imaging configurations. Experimental results are presented that support our theoretical findings. Schlieren imaging is analyzed in chapter 4. The classical Raman-Nath model (and its limitations) is first discussed. We then proceed to analyze Schlieren imaging by means of wave theory. We find that the Schlieren image of a monophonic sound field possesses an extremely large depth of focus (i.e. it is almost diffraction free). We proceed to show that the Raman-Nath interpretation can be extended to high frequency (Bragg) regimes, provided certain constraints are met. Finally, we examine wideband Schlieren imaging using optical heterodyning, which is of great practical importance in signal processing schemes. Several key results are obtained. We first present an illustrative example of a Schlieren signal processing scheme employing optical heterodyning. Although this scheme is not new per se, we present experimental results of a working experiment in which we correlate a pulse

  9. 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. PMID:24663932

  10. Acousto-optic method used to control water pollution by miscible liquids

    NASA Astrophysics Data System (ADS)

    Ferria, Kouider; Griani, Lazhar; Laouar, Naamane

    2012-05-01

    An acousto-optic (A.O.) method has been developed for controlling the quality of water mixed by miscible liquids like acetone or ethanol… The liquid mixture is filled in a rectangular glass cell, which is placed orthogonally to the incident collimated beam of light. This cell consists of a piezoelectric transducer for generating ultrasonic waves. The collimated light while passing through this cell undergoes a diffraction phenomenon. The diffracted dots are collected by a converging photographic objective and displayed in its back focal plane. The location of the diffracted dots and their intensity are sensitive to any variation of the interaction medium. This result leads to decide about the quality of the water.

  11. Acousto-optic interaction in biconical tapered fibers: shaping of the stopbands

    NASA Astrophysics Data System (ADS)

    Ramírez-Meléndez, Gustavo; Bello-Jiménez, Miguel Ángel; Cuadrado-Laborde, Christian; Díez, Antonio; Cruz, José Luis; Rodríguez-Cobos, Amparo; Balderas-Navarro, Raúl; Andrés Bou, Miguel Vicente

    2016-03-01

    The effect of a gradual reduction of the fiber diameter on the acousto-optic (AO) interaction is reported. The experimental and theoretical study of the intermodal coupling induced by a flexural acoustic wave in a biconical tapered fiber shows that it is possible to shape the transmission spectrum, for example, substantially broadening the bandwidth of the resonant couplings. The geometry of the taper transitions can be regarded as an extra degree of freedom to design the AO devices. Optical bandwidths above 45 nm are reported in a tapered fiber with a gradual reduction of the fiber down to 70 μm diameter. The effect of including long taper transition is also reported in a double-tapered structure. A flat attenuation response is reported with 3-dB stopband bandwidth of 34 nm.

  12. Q-switched fiber laser based on an acousto-optic modulator with injection seeding technique.

    PubMed

    Li, Wencai; Liu, Haowei; Zhang, Ji; Long, Hu; Feng, Sujuan; Mao, Qinghe

    2016-06-10

    The operation mechanism and the pulse property of an actively Q-switched erbium-doped fiber laser based on an acousto-optic modulator (AOM) switch with the injection seeding technique are investigated. Our results show that the Q-switched pulses can be locked to oscillate near a fixed frequency higher than that of the seed laser, though the frequency-shift effect of the AOM impedes stable cavity mode oscillations. The operation mechanism of such Q-switch fiber lasers can be explained by the mutual locking-in among the shifted frequency components originated from the injected coherence seed with the help of the gain dynamics of the Q-switch cavity. Moreover, narrow-linewidth Q-switched pulses with different repetition rates can be obtained with different cavity lengths for incredibly stable output pulses without any use of cavity-stabilized techniques. PMID:27409015

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Acousto-optically generated potential energy landscapes: potential mapping using colloids under flow.

    PubMed

    Juniper, Michael P N; Besseling, Rut; Aarts, Dirk G A L; Dullens, Roel P A

    2012-12-17

    Optical potential energy landscapes created using acousto-optical deflectors are characterized via solvent-driven colloidal particles. The full potential energy of both single optical traps and complex landscapes composed of multiple overlapping traps are determined using a simple force balance argument. The potential of a single trap is shown to be well described by a Gaussian trap with stiffness found to be consistent with those obtained by a thermal equilibrium method. We also obtain directly the depth of the well, which (as with stiffness) varies with laser power. Finally, various complex systems ranging from double-well potentials to random landscapes are generated from individually controlled optical traps. Predictions of these landscapes as a sum of single Gaussian wells are shown to be a good description of experimental results, offering the potential for fully controlled design of optical landscapes, constructed from single optical traps.

  18. 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.

  19. Acousto-optic coupling in phoxonic crystal nanobeam cavities with plasmonic behavior.

    PubMed

    Hsu, Jin-Chen; Lu, Tsung-Yi; Lin, Tzy-Rong

    2015-10-01

    Acousto-optic (AO) coupling in a two-layer GaAs/Ag heterogeneous phoxonic crystal nanobeam cavity with plasmonic behavior is studied numerically. Because of the Ag metal layer, the cavity structure hybridizes photons and surface plasmons, squeezing the optical energy into small regions near the GaAs/Ag interface; the phononic cavity modes can be simultaneously tailored to highly match the photonic cavity modes at reduced regions in the cavity. Consequently, AO coupling is enhanced at near-infrared wavelengths. Boosting of the interface effect by the acoustic displacement field mainly contributes to the AO coupling enhancement. The simultaneous small photonic mode volume and high spatial matching of photonic and phononic cavity modes enhance the photonic resonance wavelength shift by one order of magnitude. This study enables applications of strong AO or photon-phonon interaction in subwavelength nano-structures. PMID:26480095

  20. Laser diode cavity ring-down spectroscopy using acousto-optic modulator stabilization

    SciTech Connect

    Paldus, B.A.; Harris, J.S. Jr.; Martin, J.; Xie, J.; Zare, R.N.

    1997-10-01

    By using an acousto-optic modulator, we have stabilized a free-running continuous wave (CW) laser diode in the presence of strong reflections from a high finesse Fabry{endash}Perot resonator. The laser diode linewidth can be stabilized from several MHz, for high resolution spectroscopy of species at low pressures, to several hundred MHz, for lower resolution spectroscopy of species at atmospheric pressures. We demonstrated CW cavity ring-down spectroscopy of water vapor at both 1 atm and 5 Torr. We achieved ring-down repetition rates of 10{endash}50 kHz, and a noise level of 2{times}10{sup {minus}8} cm{sup {minus}1}. {copyright} {ital 1997 American Institute of Physics.}

  1. Calibrating bead displacements in optical tweezers using acousto-optic deflectors

    SciTech Connect

    Vermeulen, Karen C.; Mameren, Joost van; Stienen, Ger J.M.; Peterman, Erwin J.G.; Wuite, Gijs J.L.; Schmidt, Christoph F.

    2006-01-15

    Displacements of optically trapped particles are often recorded using back-focal-plane interferometry. In order to calibrate the detector signals to displacements of the trapped object, several approaches are available. One often relies either on scanning a fixed bead across the waist of the laser beam or on analyzing the power spectrum of movements of the trapped bead. Here, we introduce an alternative method to perform this calibration. The method consists of very rapidly scanning the laser beam across the solvent-immersed, trapped bead using acousto-optic deflectors while recording the detector signals. It does not require any knowledge of solvent viscosity and bead diameter, and works in all types of samples, viscous or viscoelastic. Moreover, it is performed with the same bead as that used in the actual experiment. This represents marked advantages over established methods.

  2. Compensation of spatial dispersion of an acousto-optic deflector with a special Keplerian telescope.

    PubMed

    Hu, Qinglei; Zhou, Zhenqiao; Lv, Xiaohua; Zeng, Shaoqun

    2016-01-15

    Compensation of spatial dispersion caused by the acousto-optic deflector (AOD) when using a femtosecond laser is difficult across the whole scanning range of the system, and this is a significant impediment to its use. In conventional methods, the dispersion of the AOD was compensated only when it was at a particular position, while at other positions, the quality of the light beam was reduced. We developed a novel method for compensating the spatial dispersion within the entire scanning range using a special Keplerian telescope. Our experimental results show that the residual dispersion of the AOD is compensated sufficiently, and the focal spots of the laser reach the diffraction limit within a 40-MHz ultrasound bandwidth. PMID:26766675

  3. Automatic target recognition and tracking using an acousto-optic image correlator

    SciTech Connect

    Molley, P.A.; Kast, B.A. )

    1992-05-01

    This paper discusses a hybrid electro-optic image processor, developed for automatic target recognition and tracking using an acousto-optic correlator and digital electronics. The optical system performs the computationally intensive correlation operation on the large 2-D input scenes. The electronics provide the decision-making capability and also perform part of the postprocessing needed for increasing the peak-to-clutter ratio in cluttered scenes. The system is able to analyze each correlation plane and apply a real-time template selection algorithm to accommodate scale or rotation changes of the target. A demonstration of the current system capabilities is presented using a terrain board with several different types of stationary and moving model vehicles.

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

    PubMed

    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

  5. Optical heterodyne micro-vibration measurement based on all-fiber acousto-optic frequency shifter.

    PubMed

    Zhang, Wending; Gao, Wei; Huang, Ligang; Mao, Dong; Jiang, Biqiang; Gao, Feng; Yang, Dexing; Zhang, Guoquan; Xu, Jingjun; Zhao, Jianlin

    2015-06-29

    An all-fiber optical heterodyne detection configuration was proposed based on an all-fiber acousto-optic structure, which acted as both frequency shifter and coupler at the same time. The vibration waveform within a frequency range between 1 Hz to 200 kHz of a piezoelectric mirror was measured using this optical heterodyne detection system. The minimal measurable vibration amplitude and resolution are around 6 pm and 1 pm in the region of tens to hundreds of kilohertz, respectively. The configuration has advantages of compact size, high accuracy and non-contact measurement. Moreover, it is of a dynamically adjustable signal-to-noise ratio to adapt different surface with different reflections in the measurement, which will improve the usage efficiency of the light power. PMID:26191765

  6. Emission spectroscopy of laser ablation plasma with time gating by acousto-optic modulator

    SciTech Connect

    Sakka, Tetsuo; Irie, Kyohei; Fukami, Kazuhiro; Ogata, Yukio H.

    2011-02-15

    The capability of acousto-optic modulator (AOM) to perform time-gated measurements for laser ablation plasma spectroscopy has been examined. Especially, we focused on the capability of the ''AOM gating'' to exclude the continuum and extremely broadened spectra usually observed immediately after the laser ablation. Final goal of the use of the AOM is to achieve considerable downsizing of the system for in situ and on-site analyses. In the present paper, it is shown that narrow and clear spectral lines can be obtained with the AOM gating even if the target is submerged in water. Also, application of this technique to the targets in air is demonstrated. It has been revealed that the AOM gating is fast enough to exclude the continuum and broadened lines, while effectively acquiring sufficiently narrow atomic lines lasting slightly longer than the continuum.

  7. Influence of acoustic energy walk-off on acousto-optic diffraction characteristics.

    PubMed

    Balakshy, Vladimir I; Voloshin, Andrey S; Molchanov, Vladimir Ya

    2015-05-01

    Influence of acoustic beam energy walk-off on characteristics of Bragg diffraction of light is studied theoretically and experimentally by the example of a paratellurite single crystal. Two cases of isotropic and anisotropic light scattering are examined. Angular and frequency characteristics of acousto-optic interaction are calculated in wide ranges of Bragg angles and ultrasound frequencies by means of modified Raman-Nath equations. It is shown that the walk-off can substantially change the width of angular and frequency ranges, resulting in their narrowing or broadening subject to position of the operating point in the Bragg angle frequency characteristic. Coefficients of broadening are introduced for characterization of this effect. It is established that frequency dependences of the broadening coefficients are similar to the Bragg angle frequency characteristics. Experimental verification of the calculations is carried out with a paratellurite cell of 10.5° crystal cut. PMID:25708348

  8. 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.

  9. 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.

  10. 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. PMID:25967617

  11. Compensation of spatial dispersion of an acousto-optic deflector with a special Keplerian telescope.

    PubMed

    Hu, Qinglei; Zhou, Zhenqiao; Lv, Xiaohua; Zeng, Shaoqun

    2016-01-15

    Compensation of spatial dispersion caused by the acousto-optic deflector (AOD) when using a femtosecond laser is difficult across the whole scanning range of the system, and this is a significant impediment to its use. In conventional methods, the dispersion of the AOD was compensated only when it was at a particular position, while at other positions, the quality of the light beam was reduced. We developed a novel method for compensating the spatial dispersion within the entire scanning range using a special Keplerian telescope. Our experimental results show that the residual dispersion of the AOD is compensated sufficiently, and the focal spots of the laser reach the diffraction limit within a 40-MHz ultrasound bandwidth.

  12. Tunable laser diode system for noninvasive blood glucose measurements.

    PubMed

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

    2005-12-01

    Optical sensing of glucose would allow more frequent monitoring and tighter glucose control for people with diabetes. The key to a successful optical noninvasive 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 low 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 microm wavelength range. The system is based on a 2.3 microm 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 present laser system and avenues for extending the tuning range beyond 400 nm. PMID:16390586

  13. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  15. 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.

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

    PubMed

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

    2014-03-15

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

  17. 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.

  18. 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.

  19. Acousto-optic Bragg diffraction in paratellurite by the sidelobes of the spatial radiation spectrum of an acoustic transducer

    NASA Astrophysics Data System (ADS)

    Kotov, V. M.

    2016-09-01

    Acousto-optic Bragg diffraction in paratellurite is investigated within the two first diffraction orders for the case of diffraction by the sidelobes of the spatial radiation spectrum of an acoustic transducer. One of the diffraction orders is due to anisotropic diffraction, and the other, to isotropic diffraction. Such a diffraction regime is achieved when the diffraction plane is inclined toward the optical axis of the crystal. For light with a wavelength of 0.63 × 10-4 cm diffracted by a "slow" sound wave with a frequency of 26 MHz, the effect manifests itself when the angle between the acousto-optic diffraction plane and the optical axis of paratellurite is ~3°. The effect is experimentally verified. The diffraction efficiency is 20% for each of the diffraction orders for a microwave signal of 8 V at the transducer.

  20. Compact acousto-optic modulator operatingin the purely Raman - Nath diffraction regime as a phase modulator in FM spectroscopy

    SciTech Connect

    Baryshev, Vyacheslav N; Epikhin, V M

    2010-08-03

    We report fabrication of a new acousto-optic modulator (AOM-RN) operating purely in the Raman - Nath diffraction regime. This device can be used as an external phase modulator in frequency-modulation (FM) optical heterodyne spectroscopy for fast and broadband frequency control of diode lasers. The AOM-RN design is significantly simplified, and its dimensions are minimised due to a decrease (by almost an order of magnitude in comparison with the existing AOMs) in the acousto-optic interaction length and the absence of impedance matching circuit. The FM spectroscopy based on AOM-RN makes it possible to analyse both absorption and dispersion properties of optical resonances under study; this possibility is shown by the example of saturated-absorption resonances in cesium vapour. The possibility of detecting coherent population trapping resonances using FM spectroscopy with AOM-RN as an external phase modulator is experimentally demonstrated.

  1. Lamb wave acousto-optic modulator in ZnO/MgO multiple quantum wells and comparison with classical modulator.

    PubMed

    Gryba, T; Lefebvre, J-E; Elmaimouni, L; Ratolojanahary, F E

    2015-10-10

    An analysis of a ZnO/MgO multiple quantum well (MQW) acousto-optic modulator with Lamb waves is performed. With the MQW thickness in the range of 0.2 times the Lamb wavelength, the only observed Lamb modes are the lowest-order symmetric S0 and antisymmetric A0 modes. These modes induce strain and electric field components which influence the absorption coefficient of the modulator by the associated variation of the excitonic energies of MQW. The optical absorption coefficient spectra of the modulator as a function of the Lamb waves' power is presented. The Lamb-wave-based modulator gives a better absorption coefficient than the Rayleigh-wave-based one. An analysis of a classical acousto-optic modulator is also performed for comparison of performance. PMID:26479819

  2. All-fiber 10 MHz acousto-optic modulator of a fiber Bragg grating at 1060 nm wavelength.

    PubMed

    Silva, Ricardo E; Tiess, Tobias; Becker, Martin; Eschrich, Tina; Rothhardt, Manfred; Jäger, Matthias; Pohl, Alexandre A P; Bartelt, Hartmut

    2015-10-01

    Acousto-optic modulation of a 1 cm fiber Bragg grating at 10.9 MHz frequency and 1065 nm wavelength is demonstrated for the first time. A special modulator design is employed to acoustically induce a dynamic radial long period grating which couples power of the fundamental mode to the higher-order modes supported by the Bragg grating. A modulated reflection band with a depth of 16 dB and 320 pm bandwidth has been achieved. The results indicate a higher modulation frequency compared to previous studies using flexural acoustic waves. In addition, the reduction of the grating length and the modulator size points to compact and faster acousto-optic modulators. PMID:26480112

  3. Modeling of in vivo acousto-optic two-photon imaging of the retina in the human eye.

    PubMed

    Kusnyerik, Akos; Rozsa, Balazs; Veress, Mate; Szabo, Arnold; Nemeth, Janos; Maak, Pal

    2015-09-01

    Our aim is to establish a novel combined acousto-optical method for in vivo imaging of the human retina with the two-photon microscope. In this paper we present modeling results based on eye model samples constructed with parameters measured on patients. We used effectively the potential of the electronic compensation offered by the acousto-optic lenses to avoid the use of adaptive optical correction. Simulation predicted lateral resolution between 1.6 µm and 3 µm on the retina. This technology allows the visualization of single cells and promises real time measuring of neural activity in individual neurons, neural segments and cell assemblies with 30-100 µs temporal and subcellular spatial resolution. PMID:26368444

  4. Anisotropy of the acousto-optic figure of merit for LiNbO₃ crystals: isotropic diffraction.

    PubMed

    Mys, Oksana; Kostyrko, Myroslav; Krupych, Oleh; Vlokh, Rostyslav

    2015-09-20

    We have developed an approach for analyzing the anisotropy of the acousto-optic figure of merit (AOFM) for lithium niobate crystals in the case of isotropic acousto-optic (AO) diffraction. The working relations for the effective elasto-optic coefficients and the AOFM have been derived. We have found that, under the conditions of isotropic AO diffraction, the maximum AOFM value for LiNbO3 is equal to 11.62×10(-15)  s(3)/kg. This is peculiar for the geometry of AO interaction of the shear acoustic wave propagating in the Y-Z plane (the velocity 3994 m/s) with the optical wave polarized in the same plane. We have demonstrated that the maximum AOFM values are achieved mainly due to the essential anisotropy and high values of the elasto-optic coefficient of LiNbO3. PMID:26406522

  5. Analysis of acousto-optic interaction based on forward stimulated Brillouin scattering in hybrid phononic-photonic waveguides.

    PubMed

    Zhang, Ruiwen; Chen, Guodong; Sun, Junqiang

    2016-06-13

    We present the generation of forward stimulated Brillouin scattering (FSBS) in hybrid phononic-photonic waveguides. To confine the optical and acoustic waves simultaneously, a hybrid waveguide is designed by embedding the silicon line defect in the silicon nitride phononic crystal slab. By taking into account three kinds hybrid waveguide, the appropriate structural parameters are obtained to enhance the acousto-optic interaction. We fabricate the honeycomb hybrid waveguide with a CMOS compatible technology. The forward Brillouin frequency shift is measured up to 2.425 GHz and the acoustic Q-factor of the corresponding acoustic mode is 1100. The influences of pump power, acoustic loss, nonlinear optical loss and lattice constant on the acousto-optic interaction in FSBS are analyzed and discussed. The proposed approach has important potential applications in on-chip all-optical signal processing. PMID:27410324

  6. A spatio-temporally compensated acousto-optic scanner for two-photon microscopy providing large field of view.

    PubMed

    Kremer, Y; Léger, J-F; Lapole, R; Honnorat, N; Candela, Y; Dieudonné, S; Bourdieu, L

    2008-07-01

    Acousto-optic deflectors (AOD) are promising ultrafast scanners for non-linear microscopy. Their use has been limited until now by their small scanning range and by the spatial and temporal dispersions of the laser beam going through the deflectors. We show that the use of AOD of large aperture (13mm) compared to standard deflectors allows accessing much larger field of view while minimizing spatio-temporal distortions. An acousto-optic modulator (AOM) placed at distance of the AOD is used to compensate spatial and temporal dispersions. Fine tuning of the AOM-AOD setup using a frequency-resolved optical gating (GRENOUILLE) allows elimination of pulse front tilt whereas spatial chirp is minimized thanks to the large aperture AOD.

  7. 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.

  8. Dynamic high-speed spatial manipulation of cold atoms using acousto-optic and spatial light modulation.

    PubMed

    Fatemi, F K; Bashkansky, M; Dutton, Z

    2007-03-19

    We demonstrate an experimental technique for high-resolution, high-speed spatial manipulation of atom clouds. By combining holographically engineered laser beams from a spatial light modulator with off-axis shear mode acousto-optic deflectors, we manipulate 1 x 3 arrays of cold atoms with individual site addressability. Additionally, we demonstrate smooth 2-dimensional motion of atomic ensembles, and the ability to guide multiple atomic ensembles independently.

  9. Simultaneous multiple-depths en-face optical coherence tomography using multiple signal excitation of acousto-optic deflectors.

    PubMed

    Zurauskas, Mantas; Rogers, John; Podoleanu, Adrian Gh

    2013-01-28

    We present a novel low-coherence interferometer configuration, equipped with acousto-optic deflectors that can be used to simultaneously acquire up to eight time domain optical coherence tomography en-face images. The capabilities of the configuration are evaluated in terms of depth resolution, signal to noise ratio and crosstalk. Then the configuration is employed to demonstrate simultaneous en-face optical coherence tomography imaging at five different depths in a specimen of armadillidium vulgare. PMID:23389175

  10. Design of an acousto-optic goniometric specimens mount. Report No. 2 on modeling of acoustic microscopes

    SciTech Connect

    Evans, G.E.; Rice, D.L.; Schwartz, M.

    1985-05-01

    The proposed project is to design, build, and test an acousto-optic goniometric specimen mount. It will be used in a related experiment, evaluating reflection of sound from the surfaces of various specimens. The desired specimen mount is one which will utilize as much of the existing testing apparatus as possible. The mount must provide a means of scanning the sound beam with a laser.

  11. Optimum cavity length and absolute cavity detuning in acousto-optically mode-locked argon-ion lasers

    NASA Astrophysics Data System (ADS)

    Ruddock, I. S.; Illingworth, R.

    1987-09-01

    Acousto-optic mode-locking in an argon-ion laser was investigated in detail. Measurement of the discharge current is shown to be an accurate means of locating the optimum cavity length which depends strongly on level of excitation. The absolute cavity mismatch between the optimum length and that corresponding to c/4 vRF was determined by direct measurement and by using a cw dye laser as an active interferometer.

  12. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  14. Resonant acousto-optics in the terahertz range: TO-phonon polaritons driven by an ultrasonic wave

    NASA Astrophysics Data System (ADS)

    Muljarov, E. A.; Poolman, R. H.; Ivanov, A. L.

    2011-03-01

    The resonant acousto-optic effect is studied both analytically and numerically in the terahertz range where the transverse-optical (TO) phonons play the role of a mediator which strongly couples the ultrasound and light fields. A propagating acoustic wave interacts with the TO phonons via anharmonic channels and opens band gaps in the TO-phonon polariton energy dispersion that results in pronounced Bragg scattering and reflection of the incoming light. The separation in frequency of different Bragg replicas, which is at the heart of acousto-optics, allows us to study the resonant acousto-optic effect in the most simple and efficient geometry of collinear propagation of electromagnetic and ultrasonic waves. The acoustically induced energy gaps, Bragg reflection spectra, and the spatial distribution of the electric field and polarization are calculated for CuCl parameters, in a wide range of frequencies and intensities of the pumping acoustic wave. Our results show drastic changes in terahertz spectra of semiconductor crystals that open the way for efficient and accessible manipulation of their infrared properties by tuning the parameters of the acoustic wave.

  15. Monitoring the Oxygen Dynamics of Brain Tissue In Vivo by Fast Acousto-Optic Scanning Microscopy: A Proposed Instrument.

    PubMed

    Zhou, Zhenqiao; Chen, Dayu; Huang, Zhiqiang; Wang, Shaofang; Zeng, Shaoqun

    2016-01-01

    The function of the brain neural circuit is highly dependent on oxygen supply. Imaging the precise oxygen distribution and dynamics are critical for understanding the relationship between neuronal activity and oxygen dynamics of the nearby capillaries. Here, we develop fast acousto-optic scanning two-photon microscopy. Combined with oxygen probes, such as PtP-C343, we can monitor oxygen dynamics at the submicron level by this real-time microscopy. In this fast acousto-optic scanning microscopy, an acousto-optic deflector (AOD), an inertia-less scanner, is used to scan the femtosecond laser. A cylindrical lens is used to compensate the 'cylindrical lens effect' of AOD and a prism is used to compensate the chromatic dispersion of AOD. An electro-optical modulator (EOM) and a sCMOS camera are gated to measure the phosphorescence lifetime. With a 40× water objective lens, this set-up can image a 100 μm × 100 μm field of view at a speed of 20 frames per second and a 25 μm × 8 μm field of view at a speed of 500 frames per second. This real-time two-photon microscopy is expected to be a good tool for observing and recording the precise rapid oxygen dynamics in the cerebral cortex, which will facilitate studies of oxygen metabolism in neurosciences. PMID:27526168

  16. High-sensitivity mid-infrared heterodyne spectrometer with a tunable diode laser as a local oscillator.

    PubMed

    Schmülling, F; Klumb, B; Harter, M; Schieder, R; Vowinkel, B; Winnewisser, G

    1998-08-20

    A new mid-IR heterodyne spectrometer, which is intended to be applied for atmospheric and astrophysical studies, is presented. The spectrometer uses a frequency-stabilized tunable diode laser as a local oscillator. Owing to the low output power of available single-mode diode lasers, a newly developed confocal-ring resonator, the diplexer, is used to superimpose the source signal efficiently with that of the local oscillator. Additionally, the diplexer serves as an optical filter that establishes controlled optical feedback between the laser diode and the detector, which allows stable laser operation with linewidths of the order of 1 MHz. The heterodyne signal from the HgCdTe detector is analyzed by means of a 1.4-GHz acousto-optical spectrometer. With this setup we find system temperatures as low as 4400 K (double sideband), that is, approximately a factor of 6 of the quantum limit.

  17. 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.

  18. Post-flight test results of acousto-optic modulator devices subjected to space exposure

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

    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 modulewas 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 space environment for more than one and a half year 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 devices. Post-flight measurements indicate that these two devices did not undergo any significant performance degradation.

  19. Performance of a laser communication system with acousto-optic tracking: an experimental study

    NASA Astrophysics Data System (ADS)

    Nikulin, V.; Khandekar, R.; Sofka, J.

    2006-02-01

    Laser communication systems hold great promise for broadband applications. This technology uses much higher-than-RF region of the spectrum and allows concentration of the signal within a very small spatial angle, thus offering unsurpassed throughput, information security, reduced weight and size of the components and power savings. Unfortunately, these intrinsic advantages do not come without a price: small beam divergence requires precise positioning, which becomes very critical at high bit rates. Complex motion patterns of the communicating platforms, resident vibrations, and atmospheric effects are known to cause significant signal losses through the mechanisms of the pointing errors, beam wander and other higher-order effects. Mitigation of those effects is achieved through the multiple means of fast tracking and wavefront control. In this paper we focus on the application of a beam steering technology and its effect on the communication performance of the system. We present the results of an experimental study of a laser communication link subjected to pointing distortions. These distortions are generated by a special disturbance element in the optical setup, which recreates specific operation environments with particular spectral characteristics. The acousto-optic technology is used to build an agile tracking system to assure the maximum signal reception in spite of the harsh operational conditions. The received communication signal is recorded and statistically analyzed to calculate the bit-error-rates. This paper presents the synthesis of a tracking system and the experimental results characterizing the communication performance under uncompensated pointing disturbance and with tracking.

  20. 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.

  1. Deflection of a monochromatic THz beam by acousto-optic methods

    SciTech Connect

    Voloshinov, V B; Nikitin, P A; Gerasimov, V V; Choporova, Yu Yu; Knyazev, B A

    2013-12-31

    The possibility of controlled deflection of an electromagnetic THz beam of a free-electron laser by acousto-optic (AO) methods has been demonstrated for the first time. The material of the AO deflector was chosen to be single-crystal germanium, which has a fairly large refractive index (n = 4.0) and a relatively low absorption coefficient for electromagnetic waves. The absorption coefficient α in germanium is 0.75 ± 0.02 cm{sup -1} at a wavelength λ = 140 μm. The diffracted beam intensity is shown to be maximum at an effective AO interaction length l = 1/α. A diffraction efficiency of 0.05% at a travelling acoustic wave power of 1.0 W is experimentally obtained. It is established that a change in the ultrasonic frequency from 25 to 39 MHz leads to variation in the external Bragg angle in the range from 19.5° to 27.5°. At a fixed Bragg angle θ{sub B} = 22.4° the frequency band of diffraction is 4.2 ± 0.1 MHz and the angular range of laser beam scanning reaches 2.5° ± 0.5°. The results obtained indicate that AO interaction can be used for controlled deflection of electromagnetic THz beams. (terahertz radiation)

  2. Investigation of acousto-optic properties of tellurium-based glasses for infrared applications

    NASA Astrophysics Data System (ADS)

    Voloshinov, V. B.; Gupta, N.; Kulakova, L. A.; Khorkin, V. S.; Melekh, B. T.; Knyazev, G. A.

    2016-02-01

    We examined the physical properties of infrared optical glasses composed of tellurium, germanium, selenium, sulfur and silicon. In particular, we measured optical, acoustic and photoelastic parameters of the following alloy compounds: germanium-selenium-tellurium (Ge-Se-Te), germanium-selenium-sulfur-tellurium (Ge-Se-S-Te), germanium-silicon-tellurium (Ge-Si-Te) and silicon-tellurium (Si-Te). Like single-crystal tellurium, the glasses demonstrate good acousto-optic (AO) diffraction efficiency and have reasonable optical transparency in a wide spectral region covering wavelengths from 1.5 to 20 μm. The optical, acoustic and photoelastic properties of the tellurium-based compounds were measured using infrared lamp sources of radiation as well as He-Ne and CO2 lasers. In this paper, we report on the optical, acoustic and photoelastic parameters of a selection of these compounds and discuss the advantages and disadvantages of using these glasses for AO device applications. We also present the measured characteristics of an AO cell fabricated in a Si20Te80 glass material which exhibited high optical uniformity and long-term chemical stability.

  3. 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.

  4. Acousto-optic pulse picking scheme with carrier-frequency-to-pulse-repetition-rate synchronization.

    PubMed

    de Vries, Oliver; Saule, Tobias; Plötner, Marco; Lücking, Fabian; Eidam, Tino; Hoffmann, Armin; Klenke, Arno; Hädrich, Steffen; Limpert, Jens; Holzberger, Simon; Schreiber, Thomas; Eberhardt, Ramona; Pupeza, Ioachim; Tünnermann, Andreas

    2015-07-27

    We introduce and experimentally validate a pulse picking technique based on a travelling-wave-type acousto-optic modulator (AOM) having the AOM carrier frequency synchronized to the repetition rate of the original pulse train. As a consequence, the phase noise characteristic of the original pulse train is largely preserved, rendering this technique suitable for applications requiring carrier-envelope phase stabilization. In a proof-of-principle experiment, the 1030-nm spectral part of an 74-MHz, carrier-envelope phase stable Ti:sapphire oscillator is amplified and reduced in pulse repetition frequency by a factor of two, maintaining an unprecedentedly low carrier-envelope phase noise spectral density of below 68 mrad. Furthermore, a comparative analysis reveals that the pulse-picking-induced additional amplitude noise is minimized, when the AOM is operated under synchronicity. The proposed scheme is particularly suitable when the down-picked repetition rate is still in the multi-MHz-range, where Pockels cells cannot be applied due to piezoelectric ringing. PMID:26367616

  5. Wave packet interferometry and quantum state reconstruction by acousto-optic phase modulation

    SciTech Connect

    Tekavec, Patrick F.; Dyke, Thomas R.; Marcus, Andrew H.

    2006-11-21

    Studies of wave packet dynamics often involve phase-selective measurements of coherent optical signals generated from sequences of ultrashort laser pulses. In wave packet interferometry (WPI), the separation between the temporal envelopes of the pulses must be precisely monitored or maintained. Here we introduce a new (and easy to implement) experimental scheme for phase-selective measurements that combines acousto-optic phase modulation with ultrashort laser excitation to produce an intensity-modulated fluorescence signal. Synchronous detection, with respect to an appropriately constructed reference, allows the signal to be simultaneously measured at two phases differing by 90 deg. Our method effectively decouples the relative temporal phase from the pulse envelopes of a collinear train of optical pulse pairs. We thus achieve a robust and high signal-to-noise scheme for WPI applications, such as quantum state reconstruction and electronic spectroscopy. The validity of the method is demonstrated, and state reconstruction is performed, on a model quantum system - atomic Rb vapor. Moreover, we show that our measurements recover the correct separation between the absorptive and dispersive contributions to the system susceptibility.

  6. Interferometric surface-wave acousto-optic time-integrating correlators

    NASA Technical Reports Server (NTRS)

    Berg, N. J.; Abramovitz, I. J.; Casseday, M. W.

    1981-01-01

    A structure for a coherent-interferometric acousto-optic (AO) time-integrating correlator was implemented by using a single surface acoustic wave (SAW) device with tilted transducers to reduce intermodulation terms. The SAW device was fabricated on Y-Z LiNbO3 with a center frequency of 175 MHz, a bandwidth of 60 MHz, and a time aperture of about 10 micros. The density of the photodetector array, with a potential of 120 MHz. Typical integration times are 30 to 40 ms, providing processing gains in excess of 10 to the 6th power. Such a device is useful in providing fast synchronization of communication links and in demodulating to base band and simultaneously acting as a synchronization lock monitor for moderate data rates. Where processing may be limited by Doppler shifts, a two dimensional architecture was implemented to allow full processing gain. Two one-dimensional, SAW AO time-integrating correlators and a two dimensional correlator are evaluated.

  7. Precise Spatiotemporal Control of Optogenetic Activation Using an Acousto-Optic Device

    PubMed Central

    Guo, Yanmeng; Song, Peipei; Zhang, Xiaohui; Zeng, Shaoqun; Wang, Zuoren

    2011-01-01

    Light activation and inactivation of neurons by optogenetic techniques has emerged as an important tool for studying neural circuit function. To achieve a high resolution, new methods are being developed to selectively manipulate the activity of individual neurons. Here, we report that the combination of an acousto-optic device (AOD) and single-photon laser was used to achieve rapid and precise spatiotemporal control of light stimulation at multiple points in a neural circuit with millisecond time resolution. The performance of this system in activating ChIEF expressed on HEK 293 cells as well as cultured neurons was first evaluated, and the laser stimulation patterns were optimized. Next, the spatiotemporally selective manipulation of multiple neurons was achieved in a precise manner. Finally, we demonstrated the versatility of this high-resolution method in dissecting neural circuits both in the mouse cortical slice and the Drosophila brain in vivo. Taken together, our results show that the combination of AOD-assisted laser stimulation and optogenetic tools provides a flexible solution for manipulating neuronal activity at high efficiency and with high temporal precision. PMID:22174813

  8. Fluorescence micro-optical sectioning tomography using acousto-optical deflector-based confocal scheme

    PubMed Central

    Qi, Xiaoli; Yang, Tao; Li, Longhui; Wang, Jiancun; Zeng, Shaoqun; Lv, Xiaohua

    2015-01-01

    Abstract. Fluorescent labeling has opened up the possibility of clarifying the complex distribution and circuit wiring of specific neural circuits for particular functions. To acquire the brain-wide fluorescently labeled neural wiring, we have previously developed the fluorescence micro-optical sectioning tomography imaging system. This employs simultaneous mechanical sectioning and confocal imaging of the slices, and is capable of acquiring the image dataset of a centimeter-sized whole-mouse brain at a voxel resolution of 1  μm. We analyze the key optical considerations for the use of an acousto-optical deflector (AOD) scanner-based confocal detection scheme in this system. As a result, the influence of confocal detection, the imaging site during sectioning, and AOD fast scan mode on signal-to-background noise ratio are described. It is shown that mechanical sectioning to separate the slice and optical sectioning by confocal detection should be combined to maximize background suppression in simultaneous fast scan imaging while sectioning system setup. PMID:26793740

  9. 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.

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

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

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

    PubMed

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

    2011-12-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  13. 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.

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

    PubMed

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

    2016-02-23

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

  15. 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.

  16. 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

  17. 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.

  18. 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.

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

    PubMed Central

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

    2016-01-01

    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. PMID:26368449

  20. 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

    2015-09-01

    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. PMID:26368449

  1. 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.

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

    PubMed

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

    2013-07-21

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

  3. Feasibility study of complex wavefield retrieval in off-axis acoustic holography employing an acousto-optic sensor

    PubMed Central

    Rodríguez, Guillermo López; Weber, Joshua; Sandhu, Jaswinder Singh; Anastasio, Mark A.

    2011-01-01

    We propose and experimentally demonstrate a new method for complex-valued wavefield retrieval in off-axis acoustic holography. The method involves use of an intensity-sensitive acousto-optic (AO) sensor, optimized for use at 3.3 MHz, to record the acoustic hologram and a computational method for reconstruction of the object wavefield. The proposed method may circumvent limitations of conventional implementations of acoustic holography and may facilitate the development of acoustic-holography-based biomedical imaging methods. PMID:21669451

  4. Quantum entanglement with acousto-optic modulators: Two-photon beats and Bell experiments with moving beam splitters

    SciTech Connect

    Stefanov, Andre; Zbinden, Hugo; Gisin, Nicolas; Suarez, Antoine

    2003-04-01

    We present an experiment testing quantum correlations with frequency shifted photons. We test Bell inequality with two-photon interferometry where we replace the beam splitters with acousto-optic modulators, which are equivalent to moving beam splitters. We measure the two-photon beats induced by the frequency shifts, and we propose a cryptographic scheme in relation. Finally, setting the experiment in a relativistic configuration, we demonstrate that the quantum correlations are not only independent of the distance but also of the time ordering between the two single-photon measurements.

  5. Phase-sensitive detection of optical resonances by using an acousto-optic modulator in the Raman - Nath diffraction mode

    SciTech Connect

    Baryshev, V N; Domnin, Yu S; Kopylov, L N

    2007-11-30

    A new method for frequency control of an external cavity diode laser without direct modulation of the injection current is proposed. The Pound - Drever optical heterodyne technique or the method of frequency control by frequency-modulated sidebands, in which an acousto-optic modulator operating in the Raman - Nath diffraction mode is used as an external phase modulator, can be employed to obtain error signals upon automatic frequency locking of the diode laser to the saturated absorption resonances within the D{sub 2} line of cesium atoms or to the optical cavity resonances. (control of laser radiation parameters)

  6. 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.

  7. Narrowband tunable filter based on velocity-selective optical pumping in an atomic vapor.

    PubMed

    Cerè, Alessandro; Parigi, Valentina; Abad, Marta; Wolfgramm, Florian; Predojević, Ana; Mitchell, Morgan W

    2009-04-01

    We demonstrate a tunable narrowband filter based on optical-pumping-induced circular dichroism in rubidium vapor. The filter achieves a peak transmission of 14.6%, a linewidth of 80 MHz, and an out-of-band extinction of >or=35 dB. The transmission peak can be tuned within the range of the Doppler linewidth of the D1 line of atomic rubidium at 795 nm. While other atomic filters work at frequencies far from absorption, the presented technique provides light resonant with atomic media, useful for atom-photon interaction experiments. The technique could readily be extended to other alkali atoms.

  8. A tunable universal terahertz filter using artificial dielectrics based on parallel-plate waveguides

    NASA Astrophysics Data System (ADS)

    Mendis, Rajind; Nag, Abhishek; Chen, Frank; Mittleman, Daniel M.

    2010-09-01

    Using parallel-plate waveguides (PPWGs) that mimic artificial dielectrics, we demonstrate a universal filter that provides low-pass, high-pass, band-pass, and band-stop (or notch) filtering functionalities in the terahertz (THz) frequency regime. The device essentially consists of two PPWGs in a complementary geometry. The filtering functionality is achieved by positioning an appropriate amplitude mask in the path of the spatially chirped THz beam between the two waveguides. By varying the position of the mask, we experimentally and theoretically demonstrate continuous tunability of the respective 3 dB cutoff frequencies within the frequency range from about 0.3 to 0.7 THz.

  9. 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.

  10. 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.

  11. 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.

  12. Fluctuations of optical phase of diffracted light for Raman-Nath diffraction in acousto-optic effect

    NASA Astrophysics Data System (ADS)

    Cun-Cheng, Weng; Zhang, Xiao-Man

    2015-01-01

    The Raman-Nath diffraction in acousto-optic effect was studied theoretically and experimentally in the paper. Up to now, each order of diffracted light in Raman-Nath diffraction was still considered simply to be just frequency-shifted and to be a plane wave. However, we find that the phase and frequency shifts occur simultaneously and individually in Raman-Nath diffraction. The findings demonstrate that, in addition to the frequency shift, the optical phase of each order of diffracted light is also shifted by the sound wave and fluctuates with the sound wave and is related to the location in the acoustic field from which the diffracted light originates. As a result, the wavefront of each order of diffracted light is modulated to fluctuate spatially and temporally with the sound wave. Obviously, these findings are significant for applications of Raman-Nath diffraction in acousto-optic effect because the optical phase plays an important role in optical coherence technology. Project supported by the National Natural Science Foundation of China (Grant No. 61178089) and the Science and Technology Program of the Educational Office of Fujian Province of China (Grant Nos. JB12012 and JB13003).

  13. Competitive effects in a YAG:Nd/sup 3 +/ ring laser with acousto-optic mode locking

    SciTech Connect

    Goncharova, I.F.; Kornienko, L.S.; Kravtsov, N.V.; Nanii, O.E.; Shelaev, A.N.

    1981-06-01

    An experimental study was made of the competitive interactions of opposite light waves in a YAG:Nd/sup 3 +/ ring laser with acousto-optic mode locking. These effects were investigated with the laser at rest and rotating. A study was made of the dependence of suppression of one of the opposite waves on the detuning of the modulation frequency from the intermode value, on the difference between the resonator frequencies due to rotation, and on the position and orientation of the acousto-optic modulator. It was found that the competition between the opposite waves in the case of forced mode locking could be weaker or stronger than in the case of free oscillations. Moreover, in the case of a solid-state ring laser with a homogeneously broadened luminescence line of the active substance one could realize bidirectional or unidirectional mode locking. Different forms of modulation of the intensities of the opposite waves were possible under forced mode-locking conditions when the ultrasonic frequency was scanned.

  14. Information encryption and retrieval in mid-RF range using acousto-optic chaos

    NASA Astrophysics Data System (ADS)

    Chatterjee, Monish R.; Kundur, Abhinay

    2012-06-01

    In recent work, low-frequency AC signal encryption, decryption and retrieval using system-parameter based keys at the receiver stage of an acousto-optic (A-O) Bragg cell under first-order feedback have been demonstrated [1,2]. The corresponding nonlinear dynamics have also been investigated using the Lyapunov exponent and the so-called bifurcation maps [3]. The results were essentially restricted to A-O chaos around 10 KHz, and (baseband) signal bandwidths in the 1-4 KHz range. The results have generally been satisfactory, and parameter tolerances (prior to severe signal distortion at the output) in the +/-5% - +/-10% range have been obtained. Periodic AC waveforms, and a short audio clip have been examined in this series of investigations. Obviously, a main drawback in the above series of simulations has been the low and impractical signal bandwidths used. The effort to increase the bandwidth involves designing a feedback system with much higher chaos frequency that would then be amenable to higher BW information. In this paper, we re-visit the problem for the case where the feedback delay time is reduced considerably, and the system parameters in the transmitter adjusted in order to drive the system with a DC driver bias into chaos. Reducing the feedback time delay to less than 1 μs, an average chaos frequency of about 10 MHz was achieved after a few trials. For the AC application, a chaos region was chosen that would allow a large enough dynamic range for the width of the available passband. Based on these dynamic choices, periodic AC signals with 1 MHz (fundamental) bandwidth were used for the RF bias driver (along with a DC bias). A triangular wave and a rectangular pulse train were chosen as examples. Results for these cases are presented here, along with comments on the system performance, and the possibility of including (static) images for signal encryption. Overall, the results are encouraging, and affirm the possibility of using A-O chaos for securely

  15. Wavelength tunable integrated add-drop filter with 10.6 nm bandwidth adjustability.

    PubMed

    Boroojerdi, M T; Ménard, M; Kirk, A G

    2016-09-19

    We present the design and characterization of a silicon-on-insulator based bandwidth and wavelength-tunable add-drop filter. The tunability of the device is achieved by independently controlling the central wavelength of two cascaded contra-directional grating assisted couplers. The device was fabricated using e-beam lithography and the tuning is demonstrated using the thermo-optic effect, which was obtained with metal heaters fabricated by a lift-off process. It is experimentally demonstrated that within the wavelength range of 1555 nm to 1573 nm the transmission bandwidth of the device can be tuned from 1.1 nm to 11.7 nm. Moreover, more than 4 nm of central wavelength tuning is demonstrated. The tunability of the central wavelength is limited by the breakdown current of the metal heaters. PMID:27661939

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  17. 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

  18. Voltage tunable multiple quantum well distributed feedback filter with an electron beam written Schottky grating

    NASA Astrophysics Data System (ADS)

    Zia, O.; Bhattacharya, P. K.; Singh, J.; Brock, T.

    1994-08-01

    A novel optoelectronic filter voltage-tunable characteristics has been developed and implemented in a multiquantum well waveguide device. By virtue of the quantum-confined Stark effect, the refractive index in quantum wells at the periphery of a guiding region can be given a periodicity in the guiding direction by application of a bias on an electron-beam patterned Schottky grating atop the guide. If the period of the Schottky grating and associated index profile satisfies the Bragg condition, as in a resonant distributed feedback structure, band-reject filtering results. Aftering the bias on the Schottky grating changes the refractive index in the wells, thereby providing tunability of the wavelength at which Bragg diffraction occurs.

  19. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

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

    PubMed

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

    2013-02-11

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

  2. 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.

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

    PubMed

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

    2016-07-15

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

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

    PubMed

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

    2016-07-15

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

  5. Silicon-based on-chip electrically tunable sidewall Bragg grating Fabry-Perot filter.

    PubMed

    Zhang, Weifeng; Ehteshami, Nasrin; Liu, Weilin; Yao, Jianping

    2015-07-01

    We report the design, fabrication, and testing of a silicon-based on-chip electrically tunable sidewall Bragg grating Fabry-Perot filter. Spectral measurement shows that the filter has a narrow notch in reflection of approximately 46 pm, a Q-factor of 33,500, and an extinction ratio of 16.4 dB. DC measurement shows that the average central wavelength shift rates with forward and reverse bias are -1.15  nm/V and 4.2  pm/V, respectively. Due to strong light confinement in the Fabry-Perot cavity, the electro-optic frequency response shows that the filter has a 3-dB modulation bandwidth of ∼5.6  GHz. The performance of using the filter to perform modulation of a 3.5  Gb/s2(7)-1 nonreturn-to-zero pseudorandom binary sequence is evaluated.

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

    SciTech Connect

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

    1997-01-01

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

  7. Solving the speckle decorrelation challenge in acousto-optic sensing using tandem nanosecond pulses within the ultrasound period.

    PubMed

    Resink, Steffen; Hondebrink, Erwin; Steenbergen, Wiendelt

    2014-11-15

    We present a novel acousto-optic (AO) method, based on a nanosecond laser system, which will enable us to obtain AO signals in liquid turbid media. By diverting part of the light in a delay line, we inject tandem pulses with 27 ns separation. The change of the speckle pattern, caused by the ultrasound phase shift, reduces the speckle contrast of the integrated speckle pattern captured in a single camera frame. With these tandem pulses, we were able to perform AO on a 2 cm liquid turbid medium in transmission mode. We show the raw signal and a spatial AO scan of a homogenous water-intralipid sample. This approach is potentially capable of AO probing in vivo, since the acquisition time (of approximately 40 ns) is four orders of magnitude less than the typical time scales of speckle decorrelation found in vivo. The method may eventually enable us to obtain fluence compensated photoacoustic signals generated by the same laser. PMID:25490500

  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. Tandem pulsed acousto-optics: obtaining the tagged light fraction from modulated non-ideal speckle patterns.

    PubMed

    Resink, S G; Steenbergen, W

    2016-01-21

    Recently we presented novel methods for acousto-optic (AO) imaging of biological tissues, taking (1) the mean square difference of speckle patterns (subtraction method) or (2) the contrast of the summation of speckle patterns (summation method) acquired from nanosecond pulses of coherent light, fired at different ultrasound phases. In this study we relate the two methods both analytically and experimentally. We experimentally show that these two methods are nearly identical provided that the maximum achievable speckle contrast is determined correctly. We show with simulations that after correction the outcome is independent of experimental detection parameters. This makes the AO methods in this study reliable, allowing quantifying speckle observations in terms of the ultrasonically tagged fractions of light. The use of tandem nanosecond pulses in one burst of ultrasound overcomes the challenge of tissue dynamics. PMID:26682957

  10. Two-frequency acousto-optic modulator driver to improve the beam pointing stability during intensity ramps

    SciTech Connect

    Froehlich, B.; Lahaye, T.; Kaltenhaeuser, B.; Kuebler, H.; Mueller, S.; Koch, T.; Fattori, M.; Pfau, T.

    2007-04-15

    We report on a scheme to improve the pointing stability of the first order beam diffracted by an acousto-optic modulator (AOM). Due to thermal effects inside the crystal, the angular position of the beam can change by as much as 1 mrad when the radio-frequency power in the AOM is reduced to decrease the first order beam intensity. This is done, for example, to perform forced evaporative cooling in ultracold atom experiments using far-off-resonant optical traps. We solve this problem by driving the AOM with two radio frequencies f{sub 1} and f{sub 2}. The power of f{sub 2} is adjusted relative to the power of f{sub 1} to keep the total power constant. Using this, the beam displacement is decreased by a factor of 20. The method is simple to implement in existing experimental setups, without any modification of the optics.

  11. 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

  12. 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.

  13. Anisotropy of acousto-optic figure of merit for LiNbO3 crystals: anisotropic diffraction.

    PubMed

    Mys, Oksana; Kostyrko, Myroslav; Vlokh, Rostyslav

    2016-03-20

    We have developed a method for the analysis of anisotropy of an acousto-optic figure of merit (AOFM), which is valid for the case of anisotropic diffraction in the trigonal crystals of the point symmetries 3m, 32, and 3¯m. The method is verified via the example of LiNbO3 crystals. The relations for the effective elasto-optic coefficients and the AOFM are obtained for the three types of acousto-optic (AO) interactions peculiar for the anisotropic AO diffraction: the interaction of a so-called type VII with a quasi-longitudinal acoustic wave and the interactions of types VIII and IX with two quasi-transverse acoustic waves. The AO diffraction geometries providing maximal AOFM values have been determined for each of the mentioned interaction types. We have found that the maximum AOFM proper for LiNbO3 is equal to 15.9×10-15  s3/kg. This value is achieved at the type IX of AO interactions in the interaction plane rotated by 60.0 deg around the principal X axis with respect to the principal X-Z plane. The type VIII of AO interactions is characterized by a comparable AOFM (15.1×10-15  s3/kg), which is realized in the Y-Z interaction plane. A close comparison of our results with the available experimental data demonstrates their fairly good agreement. PMID:27140586

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

    PubMed

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

    2014-10-20

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    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.

  16. 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

  17. Tunable ultra-wide band-stop filter based on single-stub plasmonic-waveguide system

    NASA Astrophysics Data System (ADS)

    Chen, Zhiquan; Li, Hongjian; Li, Boxun; He, Zhihui; Xu, Hui; Zheng, Mingfei; Zhao, Mingzhuo

    2016-10-01

    A nanoscale plasmonic filter based on a single-stub coupled metal-dielectric-metal waveguide system is investigated theoretically and numerically. A tunable wide band-stop can be achieved by loading a metal bar into the stub. The band-stop originates from the direct coupling between the resonance modes. The bandwidth and the center wavelength of the band-stop can be tuned by changing the parameters of the metal bar. Compared with previously reported filters, the plasmonic system has the advantages of easy fabrication and compactness. Our results indicate that the proposed system has potential to be utilized in integrated optical circuits and tunable filters.

  18. 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.

  19. Optoelectronic switch and continuously tunable filter based on a liquid crystal waveguide

    NASA Astrophysics Data System (ADS)

    Sirleto, Luigi; Coppola, Giuseppe; D'Agata, Antonella; Breglio, Giovanni; Cutolo, Antonello

    2001-05-01

    In this paper the possibility of using ferroelectric liquid crystals in active waveguide devices is explored through the analysis of an integrated electro-optic switch and a continuously tunable filter. The design and the analysis of tow electro-optical devices, based on a Bragg grating integrated in a glass waveguide having liquid crystal as cover, are presented. The integrated optics structure allows to change the reflectivity of the Bragg mirror by means of electro-optic effects of smectic liquid crystals. The integrated fast electro-optic switch is based on electro- optic properties of smectic C* in the Surface Stabilized liquid crystal structure and on the selective properties of integrated Bragg grating. It presents the output directly in the frequency domain, overcoming the typical problems of intensity dependent devices, without requiring external electronic circuit. Moreover the possibility to realize a novel continuously tunable integrated filter, combining the linear electro-optic effect of smectic A* and the selective property of Bragg grating, has been explored. The proposed filter is characterized by a narrow bandwidth, desired feature for WDM technique. The principal advantages of such device include fast tuning speed, wide tuning range, low power consumption and low cost.

  20. 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.

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

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

  2. Theoretical study on a tunable directional coupler filter based optical bistable device and its possible applications

    NASA Astrophysics Data System (ADS)

    Podoleanu, Adrian G.; Sala, Anca-Liliana; Ionescu, Liviu G.

    1994-04-01

    We theoretically analyze the behavior of a hybrid optical bistable device that uses a tunable directional coupler filter as a modulator. The device is shown to have a great potential for applications in optical computing and optical communications. The output intensity dependencies on different input parameters are plotted and their basic features are exploited in imaging applications such as optical logical gates and other optical circuits. The spectral dependence of the pulse response of the bistable device is emphasized, suggesting the design of a very sensitive wavelength sensor.

  3. Tunable wideband bandstop acoustic filter based on two-dimensional multiphysical phenomena periodic systems

    NASA Astrophysics Data System (ADS)

    Romero-García, V.; Sánchez-Pérez, J. V.; Garcia-Raffi, L. M.

    2011-07-01

    The physical properties of a periodic distribution of absorbent resonators is used in this work to design a tunable wideband bandstop acoustic filter. Analytical and numerical simulations as well as experimental validations show that the control of the resonances and the absorption of the scatterers along with their periodic arrangement in air introduce high technological possibilities to control noise. Sound manipulation is perhaps the most obvious application of the structures presented in this work. We apply this methodology to develop a device as an alternative to the conventional acoustic barriers with several properties from the acoustical point of view but also with additional esthetic and constructive characteristics.

  4. 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.

  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. PMID:24013358

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

    PubMed

    Kadota, Michio; Tanaka, Shuji

    2015-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  10. 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.

  11. 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.

  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. PMID:26479821

  13. Design of distributed FBG vibration measuring system based on Fabry-Perot tunable filter

    NASA Astrophysics Data System (ADS)

    Zhang, Cheng; Miao, Changyun; Li, Hongqiang; Gao, Hua; Gan, Jingmeng

    2011-11-01

    A distributed optical fiber grating wavelength interrogator based on fiber Fabry Perot tunable filter(FFP-TF) was proposed, which could measure dynamic strain or vibration of multi-sensing fiber gratings in one optical fiber by time division way. The wavelength demodulated mathematical model was built, the formulas of system output voltage and sensitivity were deduced and the method of finding static operating point was determined. The wavelength drifting characteristic of FFP-TF was discussed when the center wavelength of FFP-TF was set on the static operating point. A wavelength locking method was proposed by introducing a high-frequency driving voltage signal. A demodulated system was established based on Labview and its demodulated wavelength dynamic range is 290pm in theory. In experiment, by digital filtering applied to the system output data, 100Hz and 250Hz vibration signals were measured. The experiment results proved the feasibility of the demodulated method.

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

    PubMed

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

    2016-03-21

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

  15. 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.

  16. Wavelength and bandwidth-tunable silicon comb filter based on Sagnac loop mirrors with Mach-Zehnder interferometer couplers.

    PubMed

    Jiang, Xinhong; Wu, Jiayang; Yang, Yuxing; Pan, Ting; Mao, Junming; Liu, Boyu; Liu, Ruili; Zhang, Yong; Qiu, Ciyuan; Tremblay, Christine; Su, Yikai

    2016-02-01

    We propose and experimentally demonstrate a wavelength and bandwidth-tunable comb filter based on silicon Sagnac loop mirrors (SLMs) with Mach-Zehnder interferometer (MZI) couplers. By thermally tuning the MZI couplers in common and differential modes, the phase shift and reflectivity of the SLMs can be changed, respectively, leading to tunable wavelength and bandwidth of the comb filter. The fabricated comb filter has 93 comb lines in the wavelength range from 1535 nm to 1565 nm spaced by ~0.322 nm. The central wavelength can be red-shifted by ~0.462 nm with a tuning efficiency of ~0.019 nm/mW. A continuously tunable bandwidth from 5.88 GHz to 24.89 GHz is also achieved with a differential heating power ranging from 0.00 mW to 0.53 mW.

  17. Ultra-high tunable liquid crystal-plasmonic photonic crystal fiber polarization filter.

    PubMed

    Hameed, Mohamed Farhat O; Heikal, A M; Younis, B M; Abdelrazzak, Maher; Obayya, S S A

    2015-03-23

    A novel ultra-high tunable photonic crystal fiber (PCF) polarization filter is proposed and analyzed using finite element method. The suggested design has a central hole infiltrated with a nematic liquid crystal (NLC) that offers high tunability with temperature and external electric field. Moreover, the PCF is selectively filled with metal wires into cladding air holes. Results show that the resonance losses and wavelengths are different in x and y polarized directions depending on the rotation angle φ of the NLC. The reported filter of compact device length 0.5 mm can achieve 600 dB / cm resonance losses at φ = 90° for x-polarized mode at communication wavelength of 1300 mm with low losses of 0.00751 dB / cm for y-polarized mode. However, resonance losses of 157.71 dB / cm at φ = 0° can be achieved for y-polarized mode at the same wavelength with low losses of 0.092 dB / cm for x-polarized mode.

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

    NASA Astrophysics Data System (ADS)

    Malinen, Jouko; Saari, Heikki; Kemeny, Gabor; Shi, Zhenqi; Anderson, Carl

    2010-04-01

    This paper reports instrument characterization measurements, which were recently arranged to provide comparative information on different hyperspectral chemical imaging systems. Three different instruments were studied covering both tunable filter and push-broom techniques: The first instrument MatrixNIRTM is based on a LCTF tunable filter and InGaAs camera and covers wavelengths from 1000 to 1700 nm. The second one SisuCHEMATM is based on push-broom technology and MCT camera operating from 1000 to 2500 nm. The third system is an instrument prototype from VTT Technical Research Centre of Finland exploiting high speed Fabry-Perot interferometer and MCT camera, currently calibrated from 1260 to 2500 nm. The characterization procedure was designed to study instrumental noise, signal-to-noise ratio, linearity and spectral as well as spatial resolution. Finally, a pharmaceutical tablet sample was measured with each instrument to demonstrate speed of measurement in a typical application. In spite of differences in wavelength ranges and camera technologies used, the results provide interesting information on relative instrumental advantages and disadvantages, which may be useful for selecting appropriate instrumentation for defined applications. Further, an additional aim of this study is to compare the high speed Fabry-Perot imaging technology under development against the established chemical imaging techniques available on the market today.

  19. 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.

  20. 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.

  1. Improved time-resolved acousto-optic technique for optical fiber analysis of axial non-uniformities by using edge interrogation.

    PubMed

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

    2015-03-23

    The time-resolved acousto-optic technique demonstrated recently to be a very useful method for the analysis of fiber axial non-uniformities, able to detect variations of fiber diameter in the nanometric scale with a spatial resolution of few cm. An edge interrogation approach is proposed to improve further the performance of this technique. The detection of subnanometer fiber diameter changes or sub-ppm changes of the core refractive index is demonstrated.

  2. Latching operation in a tunable wavelength filter using Si sampled grating waveguide with ferroelectric liquid crystal cladding.

    PubMed

    Nakatsuhara, Katsumi; Kato, Akifumi; Hayama, Yoshiki

    2014-04-21

    A tunable wavelength filter fabricated with a latching function is proposed. The proposed tunable wavelength filter consists of a silicon sampled grating waveguide and ferro-electric liquid crystal (FLC) cladding. The sampled grating waveguide in a silicon-on-insulator (SOI) wafer achieved narrower stop bands than that with the conventional uniform grating structure. Enhanced wavelength shift was also obtained due to the increased effect in FLC by using a thinner silicon core. Bistable switching operation with the fabricated device, which was latching without state-sustaining power, was successfully demonstrated. Its switching and latching characteristics are also reported. PMID:24787847

  3. 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.

  4. 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

  5. Spectra analysis of nonuniform FBG-based acousto-optic modulator by using Fourier mode coupling theory.

    PubMed

    Liu, Chao; Pei, Li; Li, Zhuoxuan; Ning, Tigang; Yu, Shaowei; Kang, Zexin

    2013-05-10

    Fourier mode coupling theory was first employed in the spectral analysis of several nonuniform fiber Bragg grating (FBG)-based acousto-optic modulators (NU-FBG-AOMs) with the effects of Gaussian-apodization (GA), phase shift (PS), and linear chirp (LC). Because of the accuracy and simplicity of the algorithm applied in this model, the modulation performances of these modulators can be acquired effectively and efficiently. Based on the model, the reflected spectra of these modulators were simulated under various acoustic frequencies and acoustically induced strains. The simulation results of the GA-FBG-AOM and PS-FBG-AOM showed that the wavelength spacing between the primary reflection peak and the secondary reflection peak is proportional to the acoustic frequency, and the reflectivity of reflection peaks depends on the acoustically induced strains. But for the LC-FBG-AOM, the wavelength spacing between the neighboring reflection peaks increased linearly and inversely with the acoustic frequency, and the extinction ratio of each peak relates to the acoustically induced strain. These numerical analysis results, which were effectively used in the designs and fabrications of these NU-FBG-AOMs, can broaden the AOM-based application scope and shed light on the performance optimization of optical wavelength-division multiplex system.

  6. Acousto-optic effect compensation for optical determination of the normal velocity distribution associated with acoustic transducer radiation.

    PubMed

    Foote, Kenneth G; Theobald, Peter D

    2015-09-01

    The acousto-optic effect, in which an acoustic wave causes variations in the optical index of refraction, imposes a fundamental limitation on the determination of the normal velocity, or normal displacement, distribution on the surface of an acoustic transducer or optically reflecting pellicle by a scanning heterodyne, or homodyne, laser interferometer. A general method of compensation is developed for a pulsed harmonic pressure field, transmitted by an acoustic transducer, in which the laser beam can transit the transducer nearfield. By representing the pressure field by the Rayleigh integral, the basic equation for the unknown normal velocity on the surface of the transducer or pellicle is transformed into a Fredholm equation of the second kind. A numerical solution is immediate when the scanned points on the surface correspond to those of the surface area discretization. Compensation is also made for oblique angles of incidence by the scanning laser beam. The present compensation method neglects edge waves, or those due to boundary diffraction, as well as effects due to baffles, if present. By allowing measurement in the nearfield of the radiating transducer, the method can enable quantification of edge-wave and baffle effects on transducer radiation. A verification experiment has been designed. PMID:26428801

  7. 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.

  8. Tunable multiwavelength erbium-doped fiber laser based on nonlinear optical loop mirror and birefringence fiber filter

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    A tunable multiwavelength erbium-doped fiber laser (MWEDFL) based on nonlinear optical loop mirror (NOLM) and tunable birefringence fiber filter (BFF) is proposed and demonstrated. By combination of intensity-dependent loss modulation induced by NOLM and pump power adjustment, the proposed laser can achieve independent control over the number of lasing lines, without affecting other important characteristics such as channel spacing and peak location. In addition, the laser allows wavelength tuning with both the peak location and the spectral range of lasing lines controllable. Specifically, the peak location of lasing lines can be controlled to scan the whole spectral range between adjacent channels of comb filter by adjusting the BFF. Moreover, the spectral range of lasing lines can be controlled by adjusting NOLM. This tunable MWEDFL may be useful for fiber-optic communication and fiber-optic sensing.

  9. 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.

  10. A wavelength-tunable fiber laser based on a twin-core fiber comb filter

    NASA Astrophysics Data System (ADS)

    Zou, Hui; Lou, Shuqin; Yin, Guolu

    2013-02-01

    A wavelength-tunable fiber laser based on a twin-core fiber (TCF) comb filter is proposed and demonstrated. The TCF comb filter is fabricated by splicing a 0.85 m long TCF between two standard single mode fibers (SMFs) and with exhibits a good linear strain characteristic with a sensitivity of 1.23 pm/μɛ. The wavelength of the laser can be linearly tuned from 1558.04 nm to 1553.62 nm by applying an axial strain to the TCF comb filter. The optical signal-to-noise ratio (OSNR) of the fiber laser reaches 45 dB. The 3 dB bandwidth is 0.02 nm. The fluctuation of the laser peak in the output power and the wavelength is less than 0.5 dB and within 0.05 nm, respectively. The fiber laser has the advantages of having a simple structure and stable operation under room temperature.

  11. White balance in a color imaging device with electrically tunable color filters

    NASA Astrophysics Data System (ADS)

    Langfelder, G.; Zaraga, F.; Longoni, A.

    2009-08-01

    A new method for White Balance, which compensates for changes in the illuminant spectrum by changing accordingly the native chromatic reference system, is presented. A set of base color filters is selected in the sensor, accordingly to the scene illuminant, in order to keep the chromatic components of a white object independent from the illuminant. On the contrary, conventional white balance methods do not change the native color space, but change the chromatic coordinates in order to adjust the white vector direction in the same space. The development in the last ten years of CMOS color sensors for digital imaging whose color reconstruction principle is based on the absorption properties of Silicon, rather than on the presence of color filters, makes the new method applicable in a straightforward manner. An implementation of this method with the Transverse Field Detector, a color pixel with electrically tunable spectral responses is discussed. The experimental results show that this method is effective for scene illuminants ranging from the standard D75 to the standard A (i.e. for scene correlated color temperature from 7500 K to 2850 K). The color reconstruction error specific for each set of electrically selected filters, measured in a perceptive color space after the subsequent color correction, doesn't change significantly in the tested tuning interval.

  12. 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

    2012-11-01

    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.

  13. Intercomparison of tunable diode laser and gas filter correlation measurements of ambient carbon monoxide

    NASA Astrophysics Data System (ADS)

    Fried, Alan; Henry, Bruce; Parrish, David D.; Carpenter, James R.; Buhr, Martin P.

    An intercomparison that involved a standards intercomparison, interferant spiking tests and simultaneous ambient measurements was carried out between two CO measurement systems: a tunable diode laser absorption spectrometer (TDLAS) and a gas filter correlation, non-dispersive infrared absorption instrument (GFC). Both the TDLAS and the GFC techniques responded to CO. No major interferences were found for the TDLAS system; tested species included H 2O, O 3 and OCS. The GFC instrument exhibited no interference from H 2O or O 3, but only a relatively high upper limit could be placed on the O 3 interference. For CO measurements in ambient air at levels from 100 to 1500 ppbv, the results from the two instruments agreed within their combined uncertainties. On average the GFC technique was 6% higher than the TDLAS system, and there was no systematic, constant offset. The precision of the GFC instrument was about 10%, and the precision of the TDLAS system was better than 4%.

  14. Correlated color temperature tunable white LED with a dynamic color filter.

    PubMed

    Chen, Haiwei; Zhu, Ruidong; Lee, Yun-Han; Wu, Shin-Tson

    2016-03-21

    We proposed a new device structure to dynamically tune the correlated color temperature (CCT) of a white light-emitting-diode (WLED). The key component is a dynamic color filter, consisting of a liquid crystal (LC) cell sandwiched between two cholesteric LC films whose Bragg reflection band covers the blue wavelength of the WLED. When a voltage is applied to the LC cell, the transmittance of blue light is changed, while the longer wavelength part remains unaffected, resulting in a tunable CCT. Validated by experiment, our design exhibits several advantages, such as reasonably wide tuning range (6916K to 3253K), low operation voltage (~3.2 V), simple device configuration, and low cost. It is a strong contender for next generation smart lighting. PMID:27136890

  15. Tunable bandpass microwave photonic filter with ultrahigh stopband attenuation and skirt selectivity.

    PubMed

    Jiang, Fan; Yu, Yuan; Tang, Haitao; Xu, Lu; Zhang, Xinliang

    2016-08-01

    we propose and demonstrate a bandpass microwave photonic filter (MPF) with ultrahigh stopband attenuation and skirt selectivity based on a simple signal cancellation technique. By injecting two phase modulated signals located on opposite sides of two resonant gain peaks of a Fabry-Pérot semiconductor optical amplifier (FP-SOA), two microwave frequency responses can be generated by the two input signals, respectively. The two frequency responses will add together within the passband but cancel each other out within the stopband, thus generating a MPF with simultaneous ultrahigh stopband attenuation and skirt selectivity. In the experiment the obtained MPF exhibits single passband in the range from 0 to 18 GHz and is tunable from 4 to 16 GHz by adjusting the laser wavelengths. During the tuning process the maximum stopband attenuation is 76.3 dB and the minimum 30-dB to 3-dB bandwidth shape factor is 3.5. PMID:27505828

  16. Cognitive fiber Bragg grating sensors system based on fiber Fabry-Perot tunable filter technology

    NASA Astrophysics Data System (ADS)

    Zhang, Hongtao; Wang, Pengfei; Zou, Jilin; Xie, Jing; Cui, Hong-Liang

    2011-05-01

    The wavelength demodulation based on a Fiber Fabry-Pérot Tunable Filter (FFP-TF) is a common method for multiplexing Fiber Bragg Grating (FBG) sensors. But this method cannot be used to detect high frequency signals due to the limitation by the highest scanning rate that the FFP-TF can achieve. To overcome this disadvantage, in this paper we present a scheme of cognitive sensors network based on FFP-TF technology. By perceiving the sensing environment, system can automatically switch into monitoring signals in two modes to obtain better measurement results: multi measurement points, low frequency (<1 KHz) signal, and few measurement points but high frequency (~50 KHz) signals. This cognitive sensors network can be realized in current technology and satisfy current most industrial requirements.

  17. Wavelength readout system constructed of fiber Fabry-Perot tunable filter and virtual instrument

    NASA Astrophysics Data System (ADS)

    Lü, Chengang; Zhang, Ruifeng; Cheng, Pengfei; Li, Kejia; Wu, Xing; Ge, Chunfeng

    2010-08-01

    The wavelength readout system reported in this paper is chiefly constructed of fiber Fabry-Perot tunable filter (FFP-TF), data acquisition card and a virtual instrument with programmable NI Labview. By combining the dynamic scanning of FFP-TF in C waveband (1520nm-1570nm) with 50nm free spectral range (FSR) and 4000 standard finesse value, the wavelength of a tested laser diode (LD) could be detected accurately, while the spectrum is displayed on line with the help of a virtual instrument to make the spectroscopy quick analysis possible. Furthermore, the scheme can also be applied for wavelength interrogation in fiber Bragg grating (FBG) sensing system. Considering the practibility and economical efficiency of such a system, it will be of great significance to adopt such a wavelength readout system in fiber sensors used for construction, mining, aerospace,etc.

  18. Rapid spontaneous Raman light sheet microscopy using cw-lasers and tunable filters

    PubMed Central

    Rocha-Mendoza, Israel; Licea-Rodriguez, Jacob; Marro, Mónica; Olarte, Omar E.; Plata-Sanchez, Marcos; Loza-Alvarez, Pablo

    2015-01-01

    We perform rapid spontaneous Raman 2D imaging in light-sheet microscopy using continuous wave lasers and interferometric tunable filters. By angularly tuning the filter, the cut-on/off edge transitions are scanned along the excited Stokes wavelengths. This allows obtaining cumulative intensity profiles of the scanned vibrational bands, which are recorded on image stacks; resembling a spectral version of the knife-edge technique to measure intensity profiles. A further differentiation of the stack retrieves the Raman spectra at each pixel of the image which inherits the 3D resolution of the host light sheet system. We demonstrate this technique using solvent solutions and composites of polystyrene beads and lipid droplets immersed in agar and by imaging the C–H (2800-3100cm−1) region in a C. elegans worm. The image acquisition time results in 4 orders of magnitude faster than confocal point scanning Raman systems, allowing the possibility of performing fast spontaneous Raman·3D-imaging on biological samples. PMID:26417514

  19. Tunable microwave bandpass filter integrated power divider based on the high anisotropy electro-optic nematic liquid crystal.

    PubMed

    Liu, Yupeng; Liu, Yang; Li, Haiyan; Jiang, Di; Cao, Weiping; Chen, Hui; Xia, Lei; Xu, Ruimin

    2016-07-01

    A novel, compact microwave tunable bandpass filter integrated power divider, based on the high anisotropy electro-optic nematic liquid crystal, is proposed in this letter. Liquid crystal, as the electro-optic material, is placed between top inverted microstrip line and the metal plate. The proposed structure can realize continuous tunable bandpass response and miniaturization. The proposed design concept is validated by the good performance of simulation results and experimental results. The electro-optic material has shown great potential for microwave application. PMID:27475583

  20. Tunable microwave bandpass filter integrated power divider based on the high anisotropy electro-optic nematic liquid crystal.

    PubMed

    Liu, Yupeng; Liu, Yang; Li, Haiyan; Jiang, Di; Cao, Weiping; Chen, Hui; Xia, Lei; Xu, Ruimin

    2016-07-01

    A novel, compact microwave tunable bandpass filter integrated power divider, based on the high anisotropy electro-optic nematic liquid crystal, is proposed in this letter. Liquid crystal, as the electro-optic material, is placed between top inverted microstrip line and the metal plate. The proposed structure can realize continuous tunable bandpass response and miniaturization. The proposed design concept is validated by the good performance of simulation results and experimental results. The electro-optic material has shown great potential for microwave application.

  1. Microwave photonic filter with reconfigurable and tunable bandpass response using integrated optical signal processor based on microring resonator

    NASA Astrophysics Data System (ADS)

    Zhang, Zan; Huang, Beiju; Zhang, Zanyun; Cheng, Chuantong; Chen, Hongda

    2013-12-01

    A bandpass microwave photonic filter based on an integrated optical signal processor is proposed and demonstrated by numerical simulation. The optical signal processor consisting of double-bus-coupled and series-cascaded silicon microrings (MRs) is used to produce two bandpass responses to process optical carrier signal and sideband signal separately. Because of the tunability of MRs, variable -3 dB bandwidth and tunable operating frequency are achieved. The -3 dB bandwidth and operating frequency can be tuned from 1.5 to 12 GHz and from 15 to 34 GHz, respectively. The loss impact, tuning method, and fabrication error tolerance are also discussed.

  2. 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.

  3. Characterization of the non-collinear acousto-optical cell based on calomel (Hg2Cl2) crystal and operating within the two-phonon light scattering

    NASA Astrophysics Data System (ADS)

    Shcherbakov, Alexandre S.; Arellanes, Adan O.

    2016-03-01

    Performances of any system for data processing based on acousto-optical technique are mainly determined by parameters of the acousto-optical cell (AOC) exploited within the schematic arrangement. Here, basic properties of the AOC, involved into a novel processor for precise optical spectrum analysis dedicated to modern astrophysical applications, are considered. Because potential applications of this processor will be focused on investigations in extra-galactic astronomy as well as studies of extra-solar planets, an advanced regime of the non-collinear two-phonon light scattering has been elaborated for spectrum analysis with significantly improved spectral resolution. Under similar uprated requirements, the AOC, based on that specific regime in the calomel (Hg2Cl2) crystal, had been chosen, and its parameters were analyzed theoretically and verified experimentally. Then, the adequate approach to estimating the frequency/spectral bandwidth and spectral resolution had been developed. The bandwidth was calculated and experimentally realized with the additionally involved tilt angle of light incidence, allowing variations for acoustic frequencies. The resolution was characterized taking into account its doubling peculiar to the nonlinear two-phonon mechanism of light scattering. Proof-of-principle experiments were performed with the calomel AOC of 52 mm optical aperture, providing ~94% efficiency in the transmitted light due to the slow-shear acoustic mode of finite amplitude (the acoustic power density ~150 mW/mm2) with the velocity of 0.347×105 cm/s at the radio-wave acoustic frequency ~71 MHz. As a result, we have obtained the spectral resolution <0.235 Å within the spectral bandwidth <290 Å that looks as the best one can mention at the moment in acousto-optics.

  4. 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.

  5. The simulation & improved design of tunable channel drop filter using hexagonal photonic crystal ring resonator

    NASA Astrophysics Data System (ADS)

    Chhipa, Mayur Kumar

    2014-10-01

    In this paper, we have proposed a new design of tunable two dimensional (2D) photonic crystal (PhC) channel drop filter (CDF) using ring resonators. The increasing interest in photonic integrated circuits (PIC's) and the increasing use of all-optical fiber networks as backbones for global communication systems have been based in large part on the extremely wide optical transmission bandwidth provided by dielectric materials. Based on the analysis we present novel photonic crystal channel drop filters. Simulations demonstrate that these filters exhibit ideal transfer characteristics. Channel dropping filters (CDF's) that access one channel of a wavelength division multiplexed (WDM) signal while leaving other channels undisturbed are essential components of PIC's and optical communication systems. In this paper we have investigated such parameters which have an effect on resonant wavelength in this Channel Drop Filter, such as dielectric constant of inner, coupling, adjacent and whole rods of the structure. The dimensions of these structures are taken as 20a×19a and the area of the proposed structure is about 125.6μm2; therefore this structure can be used in the future photonic integrated circuits. While using this design the dropping efficiency at the resonance of single ring are 100%. The spectrum of the power transmission is obtained with finite difference time domain (FDTD) method. FDTD method is the most famous method for PhC analysis. In this paper the dielectric rods have a dielectric constant of 10.65, so the refractive index is 3.26 and radius r=0.213a is located in air, where a is a lattice constant. In this we have used five scatter rods for obtaining more coupling efficiency; radius of scatter rods is set to 0.215a. The proposed structure is simulated with OptiFDTD.v.8.0 software, the different dielectric constant of rods equal to ɛr-0.4, ɛr and ɛr+0.4 at wavelength of 1570 nm.

  6. 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.

  7. 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.

  8. 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.

  9. Characterization of the optical sub-system in an advanced prototype of a new acousto-optical spectrometer for the Mexican Large Millimeter Telescope

    NASA Astrophysics Data System (ADS)

    Shcherbakov, Alexandre S.; Sanchez Lucero, Daniel; Laskin, Alexander

    2011-09-01

    A few optically matched by each other sub-systems related to an advanced prototype of acousto-optical spectrometer for radio-astronomy are analyzed jointly. Rather precise control over the incident light polarization should be assured in the scheme together with a required expanding of the incident light beam. Moreover, the needed light-beam apodization, suppressing side lobes within registration of each individual resolvable spot and increasing the dynamic range of spectrometer, has to be taken into account as well. The current stage of analysis related to afore-mentioned problems as well as the results of trial experiments are presented.

  10. 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.

  11. Precise modulation of laser radiation by an acousto-optic modulator for stabilisation of the Nd : YAG laser on optical resonances in molecular iodine

    NASA Astrophysics Data System (ADS)

    Denisov, V. I.; Ignatovich, S. M.; Kvashnin, N. L.; Skvortsov, M. N.; Farnosov, S. A.

    2016-05-01

    A system of precise frequency modulation of laser radiation by an acousto-optic modulator, which makes it possible to stabilise the radiation power and simultaneously suppress the residual amplitude modulation to a level of 10-8 of the total laser power at the third harmonic of modulation frequency (~500 Hz), is presented. The use of this system for the Nd : YAG/I2 optical frequency standard and application of digital signal synthesis and processing methods provided a level of frequency standard instability as small as ~10-15 for ~6 × 104 s.

  12. Dual-wavelength erbium-doped fiber laser with tunable wavelength spacing using a twin core fiber-based filter

    NASA Astrophysics Data System (ADS)

    Yin, Guolu; Lou, Shuqin; Wang, Xin; Han, Bolin

    2014-05-01

    A dual-wavelength erbium-doped fiber laser with tunable wavelength spacing was proposed and experimentally demonstrated by using a twin core fiber (TCF)-based filter. Benefiting from the polarization dependence of the TCF-based filter, the laser operated in dual-wavelength oscillation with two orthogonal polarization states. By adjusting the polarization controller, the wavelength spacing was tuned from 0.1 nm to 1.2 nm without shifting the centre position of the two wavelengths. By stretching the TCF, the two wavelengths were simultaneously tuned with fixed wavelength spacing. Such a dual-wavelength fiber laser could find applications in optical fiber sensors and microwave photonics generation.

  13. 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.

  14. Morphogen-defined patterning of Escherichia coli enabled by an externally tunable band-pass filter

    PubMed Central

    Sohka, Takayuki; Heins, Richard A; Ostermeier, Marc

    2009-01-01

    Background Gradients of morphogens pattern cell fate – a phenomenon that is especially important during development. A simple model system for studying how morphogens pattern cell behavior would overcome difficulties inherent in the study of natural morphogens in vivo. A synthetic biology approach to building such a system is attractive. Results Using an externally-tunable band-pass filter paradigm, we engineered Escherichia coli cells to function as a model system for the study of how multiple morphogens can pattern cell behavior. We demonstrate how our system exhibits behavior such as morphogen crosstalk and how the cells' growth and fluorescence can be patterned in a number of complex patterns. We extend our cell patterning from 2D cultures on the surface of plates to 3D cultures in soft agarose medium. Conclusion Our system offers a convenient, well-defined model system for fundamental studies on how multiple morphogen gradients can affect cell fate and lead to pattern formation. Our design principles could be applied to eukaryotic cells to develop other models systems for studying development or for enabling the patterning of cells for applications such as tissue engineering and biomaterials. PMID:19586541

  15. 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.

  16. A liquid-crystal-tunable-filter-based multispectral imaging system for prediction of apple fruit firmness

    NASA Astrophysics Data System (ADS)

    Peng, Yankun; Lu, Renfu

    2004-11-01

    Firmness of apple fruit is an important quality attribute, which varies greatly in the same lot of fruit due to such factors as climatic condition, cultural practice, harvest time or maturity level, and postharvest handling and storage. This research developed a compact multispectral imaging system with a low cost digital camera and a liquid crystal tunable filter (LCTF), and proposed a modified Lorentzian distribution (MLD) function to describe scattering profiles acquired from Red Delicious apples. The LCTF, which allows for the rapid, vibration-less selection of any wavelength in the visible/near-infrared range, was used to find optimal wavelengths over the spectral region between 650 nm and 1,000 nm for predicting apple fruit firmness. Radial scattering profiles were described accurately by the MLD function with four profile parameters for wavelengths between 650 nm and 1000 nm at an interval of 10 nm. Multi-linear regression (MLR) and cross-validation were performed on relating MLD parameters to fruit firmness. The prediction model gave good firmness predictions with the correlation coefficient (r) of 0.82 and the standard error of validation (SEV) of 6.64 N, which were considerably better than those obtained with visible/near-infrared spectroscopy.

  17. 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.

  18. 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.

  19. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

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

  1. Tunable Fabry-Perot filter in cobalt doped fiber formed by optically heated fiber Bragg gratings pair

    NASA Astrophysics Data System (ADS)

    Li, Ying; Zhou, Bin; Zhang, Liang; He, Sailing

    2015-06-01

    In this paper, a tunable fiber Fabry-Perot (F-P) filter by all-optical heating is proposed. Two high reflective fiber Bragg gratings (FBG) fabricated in cobalt doped single mode fiber form the F-P cavity. The cobalt-doped fiber used here is an active fiber, and it transforms optical power from a control laser into heat effectively due to the nonradiative processes. The generated heat raises the refraction index of the fiber and enlarges the F-P cavity's length, realizing the all-optical tuning characteristics. By adjusting the power of the control laser, the resonant wavelength of our proposed fiber F-P filter can be high precisely controlled. The cavity length of the filter is carefully designed to make sure the longitude mode spacing is comparable to the grating bandwidth, making it single mode operating.

  2. 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.

  3. Electrically tunable color filter based on a polarization-tailored nano-photonic dichroic resonator featuring an asymmetric subwavelength grating.

    PubMed

    Park, Chang-Hyun; Yoon, Yeo-Taek; Shrestha, Vivek Raj; Park, Chul-Soon; Lee, Sang-Shin; Kim, Eun-Soo

    2013-11-18

    We have demonstrated a highly efficient electrically tunable color filter, which provides precise control of color output, taking advantage of a nano-photonic polarization-tailored dichroic resonator combined with a liquid-crystal based polarization rotator. The visible dichroic resonator based on the guided mode resonance, which incorporates a planar dielectric waveguide in Si3N4 integrated with an asymmetric two-dimensional subwavelength Al grating with unequal pitches along its principal axes, exhibited polarization specific transmission featuring high efficiency up to 75%. The proposed tunable color filters were constructed by combining three types of dichroic resonators, each of which deals with a mixture of two primary colors (i.e. blue/green, blue/red, and green/red) with a polarization rotator exploiting a twisted nematic liquid crystal cell. The output colors could be dynamically and seamlessly customized across the blend of the two corresponding primary colors, by altering the polarization via the voltage applied to the polarization rotator. For the blue/red filter, the center wavelength was particularly adjusted from 460 to 610 nm with an applied voltage variation of 2 V, leading to a tuning range of up to 150 nm. And the spectral tuning was readily confirmed via color mapping. The proposed devices may permit the tuning span to be readily extended by tailoring the grating pitches. PMID:24514390

  4. Spectral Analysis of Airborne Effluents from Nuclear Facilities and Design of AOTF Spectroradiometer

    SciTech Connect

    Villa, E.; Suhre, D.R.; Taylor, L.H.

    1995-03-22

    This report summarizes the spectral analysis and design of an acousto optic tunable filter (AOTF) imaging spectroradiometer for the project SR003. This system will use passive open-path infrared absorption to detect the presence of various source gases.

  5. Pulsed 456 nm deep-blue light generation by acousto-optical Q-switching and intracavity frequency doubling of Nd:GdVO4

    NASA Astrophysics Data System (ADS)

    Gao, J.; Yu, X.; Chen, F.; Li, X. D.; Yan, R. P.; Zhang, Z.; Yu, J. H.; Wang, Y. Z.

    2008-08-01

    We present what is, to the best of our knowledge, the first pulsed deep-blue laser at 456 nm by acousto-optical Q-switching and intracavity frequency doubling of a diode-end-pumped Nd:GdVO4 laser on the 4F3/2 → 4I9/2 transition at 912 nm. When the incident pump power is 36 W, the maximum single pulse energy of 44.1 μJ, pulse duration of 140 ns and peak power of 315 W are achieved at 10 kHz; the maximum average power of 770 mW, pulse duration of 200 ns and peak power of 193 W are obtained at 20 kHz. The fluctuation of the blue output power is less than 2.4% within the given 20 min at the maximum blue output power.

  6. Acousto-optic Q-switched self-frequency-doubling Er:Yb:YAl3(BO3)4 laser at 800 nm.

    PubMed

    Chen, Yujin; Lin, Yanfu; Gong, Xinghong; Huang, Jianhua; Luo, Zundu; Huang, Yidong

    2012-05-01

    Actively Q-switched self-frequency-doubling laser at 800 nm was first reported in an Er:Yb:YAl3(BO3)4 crystal by using an acousto-optical modulator. At incident pump power of 16 W and pulse repetition frequency of 1 kHz, 1600 nm fundamental pulse laser with energy of 130 μJ and width of 170 ns, and self-frequency-doubling 800 nm pulse laser with energy of 20 μJ and width of 96 ns were respectively achieved in a hemispherical resonator end-pumped by a 970 nm laser diode. Pulse characteristics of fundamental and self-frequency-doubling lasers at different pulse repetition frequencies were also investigated.

  7. Acousto-optical interaction of surface acoustic and optical waves in a two-dimensional phoxonic crystal hetero-structure cavity.

    PubMed

    Ma, Tian-Xue; Zou, Kui; Wang, Yue-Sheng; Zhang, Chuanzeng; Su, Xiao-Xing

    2014-11-17

    Phoxonic crystal is a promising material for manipulating sound and light simultaneously. In this paper, we theoretically demonstrate the propagation of acoustic and optical waves along the truncated surface of a two-dimensional square-latticed phoxonic crystal. Further, a phoxonic crystal hetero-structure cavity is proposed, which can simultaneously confine surface acoustic and optical waves. The interface motion and photoelastic effects are taken into account in the acousto-optical coupling. The results show obvious shifts in eigenfrequencies of the photonic cavity modes induced by different phononic cavity modes. The symmetry of the phononic cavity modes plays a more important role in the single-phonon exchange process than in the case of the multi-phonon exchange. Under the same deformation, the frequency shift of the photonic transverse electric mode is larger than that of the transverse magnetic mode. PMID:25402086

  8. Application of independent component analysis method in real-time spectral analysis of gaseous mixtures for acousto-optical spectrometers based on differential optical absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Fadeyev, A. V.; Pozhar, V. E.

    2012-10-01

    It is discussed the reliability problem of time-optimized method for remote optical spectral analysis of gas-polluted ambient air. The method based on differential optical absorption spectroscopy (DOAS) enables fragmentary spectrum registration (FSR) and is suitable for random-spectral-access (RSA) optical spectrometers like acousto-optical (AO) ones. Here, it is proposed the algorithm based on statistical method of independent component analysis (ICA) for estimation of a correctness of absorption spectral lines selection for FSR-method. Implementations of ICA method for RSA-based real-time adaptive systems are considered. Numerical simulations are presented with use of real spectra detected by the trace gas monitoring system GAOS based on AO spectrometer.

  9. Synchronization of two passively mode-locked erbium-doped fiber lasers by an acousto-optic modulator and grating scheme

    SciTech Connect

    Jiang, M.; Sha, W.; Rahman, L.; Barnett, B.C.; Andersen, J.K.; Islam, M.N.; Reddy, K.V.

    1996-06-01

    We synchronize two passively mode-locked erbium-doped fiber lasers by adjusting only the cavity length to correct both the repetition rate and the phase. The interlaser jitter is less than 6ps (1.3times the pulse width) and is extracted from the cross correlation of the two lasers. The lock can be maintained for extended periods of time. These results are obtained by use of a novel acousto-optic-modulator{endash}grating scheme, which provides an equivalent of 300 {mu}m in cavity length tuning with a bandwidth of 10 kHz. These parameters are 30 times the length and 10 times the bandwidth of a typical piezoelectric transducer. {copyright} {ital 1996 Optical Society of America.}

  10. Acousto-optic Q-switching laser performance of Yb:GdCa(4)O(BO(3))(3)crystal.

    PubMed

    Chen, Xiaowen; Xu, Honghao; Guo, Yunfeng; Han, Wenjuan; Yu, Haohai; Zhang, Huaijin; Liu, Junhai

    2015-08-20

    We report on the active Q-switching laser performance of Yb:GdCa4O(BO3)3 crystal, demonstrated by employing an acousto-optic Q-switch in a compact plano-concave resonator. Stable repetitively Q-switched operation is achieved with pulse repetition rates varying from 30 to 0.2 kHz, producing an average output power of 10.2 W at 1027.5 nm at 30 kHz of repetition rate, with an optical-to-optical efficiency of 30%. The maximum pulse energy generated at the lowest repetition rate of 0.2 kHz is 4.75 mJ, with a pulse width being 11 ns, gives rise to a peak power that amounts to 432 kW. PMID:26368745

  11. Acousto-optical interaction of surface acoustic and optical waves in a two-dimensional phoxonic crystal hetero-structure cavity.

    PubMed

    Ma, Tian-Xue; Zou, Kui; Wang, Yue-Sheng; Zhang, Chuanzeng; Su, Xiao-Xing

    2014-11-17

    Phoxonic crystal is a promising material for manipulating sound and light simultaneously. In this paper, we theoretically demonstrate the propagation of acoustic and optical waves along the truncated surface of a two-dimensional square-latticed phoxonic crystal. Further, a phoxonic crystal hetero-structure cavity is proposed, which can simultaneously confine surface acoustic and optical waves. The interface motion and photoelastic effects are taken into account in the acousto-optical coupling. The results show obvious shifts in eigenfrequencies of the photonic cavity modes induced by different phononic cavity modes. The symmetry of the phononic cavity modes plays a more important role in the single-phonon exchange process than in the case of the multi-phonon exchange. Under the same deformation, the frequency shift of the photonic transverse electric mode is larger than that of the transverse magnetic mode.

  12. Study of radiation-induced effects in photonic devices: Acousto-optic modulators and deflectors. Final report, 15 August 1991--15 August 1997

    SciTech Connect

    Taylor, E.W.; Sanchez, A.D.; Winter, J.E.; McKinney, S.J.; Paxton, A.H.

    1998-01-01

    In a preliminary report acousto-optic devices (AODs) were exposed to flash x-ray, linearly accelerated electrons, and gamma ray irradiations to determine their sensitivity to radiation and applicability to space and enhanced radiation environments. This final report is a continuation and finalization of those initial studies and details the findings of a comprehensive investigation of radiation induced effects in lead molybdate (PbMoO{sub 4}), gallium phosphide (GaP) , indium phosphide (InP), tellurium dioxide (TeO{sub 2}), and lithium niobate (LiNbO{sub 3}) acousto-optic Bragg cell deflectors and modulators. Gamma ray, X-ray, electrons, proton and neutron irradiations were conducted to bound, delineate and differentiate radiation induced changes to operational AO Bragg Cells. The majority of the irradiations were performed in situ, wherein the Bragg cells were fully operational during the radiation exposures. Using this approach, instantaneous changes to Bragg cell parameters such as spatial intensities, deflection angles, bandwidth, material absorption, diffraction efficiency and polarization states were determined. A majority of the radiation induced effects observed were determined to evolve from the heating associated with the interaction of radiation with matter, thus resulting in observable thermo-optic effects. The effects of heating in AO Bragg crystals were investigated and confirmed using three independent approaches: traditional broad area source irradiations, ion microbeam irradiations, and irradiation by a CO{sub 2} laser. It was concluded that AO Bragg deflectors and modulators are quite insensitive to the long term low dose radiation environments that would be encountered in the natural space environment. However, under pulsed high dose (or high fluence) irradiations, Bragg cell transient responses could result in disruption of normal operations.

  13. 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.

  14. Monitoring synaptic and neuronal activity in 3D with synthetic and genetic indicators using a compact acousto-optic lens two-photon microscope☆

    PubMed Central

    Fernández-Alfonso, Tomás; Nadella, K.M. Naga Srinivas; Iacaruso, M. Florencia; Pichler, Bruno; Roš, Hana; Kirkby, Paul A.; Silver, R. Angus

    2014-01-01

    Background Two-photon microscopy is widely used to study brain function, but conventional microscopes are too slow to capture the timing of neuronal signalling and imaging is restricted to one plane. Recent development of acousto-optic-deflector-based random access functional imaging has improved the temporal resolution, but the utility of these technologies for mapping 3D synaptic activity patterns and their performance at the excitation wavelengths required to image genetically encoded indicators have not been investigated. New method Here, we have used a compact acousto-optic lens (AOL) two-photon microscope to make high speed [Ca2+] measurements from spines and dendrites distributed in 3D with different excitation wavelengths (800–920 nm). Results We show simultaneous monitoring of activity from many synaptic inputs distributed over the 3D arborisation of a neuronal dendrite using both synthetic as well as genetically encoded indicators. We confirm the utility of AOL-based imaging for fast in vivo recordings by measuring, simultaneously, visually evoked responses in 100 neurons distributed over a 150 μm focal depth range. Moreover, we explore ways to improve the measurement of timing of neuronal activation by choosing specific regions within the cell soma. Comparison with existing methods These results establish that AOL-based 3D random access two-photon microscopy has a wider range of neuroscience applications than previously shown. Conclusions Our findings show that the compact AOL microscope design has the speed, spatial resolution, sensitivity and wavelength flexibility to measure 3D patterns of synaptic and neuronal activity on individual trials. PMID:24200507

  15. Versatile Tunable Current-Mode Universal Biquadratic Filter Using MO-DVCCs and MOSFET-Based Electronic Resistors

    PubMed Central

    2014-01-01

    This paper presents a versatile tunable current-mode universal biquadratic filter with four-input and three-output employing only two multioutput differential voltage current conveyors (MO-DVCCs), two grounded capacitors, and a well-known method for replacement of three grounded resistors by MOSFET-based electronic resistors. The proposed configuration exhibits high-output impedance which is important for easy cascading in the current-mode operations. The proposed circuit can be used as either a two-input three-output circuit or a three-input single-output circuit. In the operation of two-input three-output circuit, the bandpass, highpass, and bandreject filtering responses can be realized simultaneously while the allpass filtering response can be easily obtained by connecting appropriated output current directly without using additional stages. In the operation of three-input single-output circuit, all five generic filtering functions can be easily realized by selecting different three-input current signals. The filter permits orthogonal controllability of the quality factor and resonance angular frequency, and no inverting-type input current signals are imposed. All the passive and active sensitivities are low. Postlayout simulations were carried out to verify the functionality of the design. PMID:24982963

  16. Power-ratio tunable dual-wavelength laser using linearly variable Fabry-Perot filter as output coupler.

    PubMed

    Wang, Xiaozhong; Wang, Zhongfa; Bu, Yikun; Chen, Lujian; Cai, Guoxiong; Huang, Wencai; Cai, Zhiping; Chen, Nan

    2016-02-01

    For a linearly variable Fabry-Perot filter, the peak transmission wavelengths change linearly with the transverse position shift of the substrate. Such a Fabry-Perot filter is designed and fabricated and used as an output coupler of a c-cut Nd:YVO4 laser experimentally in this paper to obtain a 1062 and 1083 nm dual-wavelength laser. The peak transmission wavelengths are gradually shifted from 1040.8 to 1070.8 nm. The peak transmission wavelength of the Fabry-Perot filter used as the output coupler for the dual-wavelength laser is 1068 nm and resides between 1062 and 1083 nm, which makes the transmissions of the desired dual wavelengths change in opposite slopes with the transverse shift of the filter. Consequently, powers of the two wavelengths change in opposite directions. A branch power, oppositely tunable 1062 and 1083 nm dual-wavelength laser is successfully demonstrated. Design principles of the linear variable Fabry-Perot filter used as an output coupler are discussed. Advantages of the method are summarized.

  17. Electronically tunable voltage-mode universal filter with single-input five-output using simple OTAs

    NASA Astrophysics Data System (ADS)

    Kumngern, Montree; Suwanjan, Peerawut; Dejhan, Kobchai

    2013-08-01

    This article presents a new electronically tunable voltage-mode universal biquadratic filter with single-input five-output using simple operational transconductance amplifiers (OTAs) and grounded capacitors. The proposed configuration provides low-pass, band-pass, high-pass, band-stop and all-pass voltage responses at a high-impedance input terminal that enables easy cascading in voltage-mode. The natural frequency and the quality factor can be set orthogonally by adjusting the circuit components. The natural frequency can also be controlled electronically by adjusting the bias currents of the OTAs. For realising all the five standard filtering functions, no critical-matching conditions are imposed and all the incremental parameter sensitivities are low. Experimental and simulation results that confirm the theoretical predictions are given.

  18. 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

  19. 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.

  20. 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.

  1. Design of tunable transmission filter using one-dimensional defective photonic crystal structure containing electro-optic material

    NASA Astrophysics Data System (ADS)

    Bandyopadhyay, Rajorshi; Chakraborty, Rajib

    2015-11-01

    A narrowband tunable transmission filter suitable for wavelength division multiplexing is designed. The basic structure is a one-dimensional Fabry-Perot structure formed by layers of dielectric magnesium fluoride and electro-optic lithium niobate, which act as low and high refractive index material layers, respectively. A narrowband phase shifted transmission peak occurs within the stopband of the reflectance spectra of the structure by introducing the defect of a low-index material at a suitable position in the structure. The bandwidth of the peak depends on the number of bilayers and also on the operating wavelength. The phase shift of the transmission peak is linearly related to the wavelength under consideration. By adjusting the defect layer width, this shift of the transmission peak from the operating wavelength can be avoided. The device dimensions are so chosen that such a structure can be fabricated and used with presently available technology. A linear transmission peak tunability of 4 nm/10 V is achieved for this device by varying the refractive index of the electro-optic lithium niobate layer with externally applied voltage along its z axis. All the simulations have been carried out using the finite difference time domain method in a MATLAB® environment.

  2. Novel type of tunable infrared filters based on the Al 2O 3 particles - Liquid crystal system

    NASA Astrophysics Data System (ADS)

    Ibragimov, Tahir D.; Bayramov, Gazanfar M.

    2012-01-01

    The optical transmission of small aluminum oxide particles in liquid crystal 4-methoxybenzylidene-4'-butylaniline (MBBA) and dual-frequency liquid crystal mixture consisting of 4-n-pentyl-4'-cyanobiphenyl (5CB), 4-hexyloxyphenyl ester 4'-hexyloxy-3-nitrobenzoic acid (C2), 4-n-pentanoyloxy-benzoic acid-4'-hexyloxyphenyl ester (H 22) was studied. It was established that there was a transmission band which was shifted on application of a voltage and depended on temperature. At using the dual-frequency liquid crystal as a matrix, a transmission band maximum switched at changing of the frequency. The experimental results are explained by the optical homogeneity of the system in a narrow wavenumber interval when the refractive indices of the particle material and the matrix are close, and also by re-orientation of the liquid crystal molecules when a voltage is applied. The obtained results can be used in constructing of tunable filters and compact monochromators.

  3. 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.

  4. Laser-induced fluorescence imaging of plants using a liquid crystal tunable filter and charge coupled device imaging camera

    NASA Astrophysics Data System (ADS)

    Saito, Yasunori; Matsubara, Tomohiro; Koga, Tomoya; Kobayashi, Fumitoshi; Kawahara, Takuya D.; Nomura, Akio

    2005-10-01

    We developed a laser-induced fluorescence imaging system for plant monitoring use, with which it was possible to make an image at any wavelength between 430 and 750nm. The excitation source for the fluorescence was a cw ultraviolet laser diode with 398nm, and the detector was an image-intensified charge coupled device. A liquid crystal tunable filter was used as the fluorescence wavelength selection device. All of the system performance including the wavelength tuning was electrically controlled, so that it could be operated with no mechanical vibration noise. The fluorescence images of a coffee tree leaf obtained at 440, 530, 685, and 740nm clearly showed a distribution pattern of the fluorescence intensity over the leaf. The pattern reflected the different physiological statuses of the plant. Advantages of the imaging system were experimentally discussed on a point of detection of inhomogeneous physiological activities over a plant leaf.

  5. Wavelength modulation spectroscopy at 1530.32 nm for measurements of acetylene based on Fabry-Perot tunable filter

    NASA Astrophysics Data System (ADS)

    Yun-Long, Li; Bing-Chu, Yang; Xue-Mei, Xu

    2016-02-01

    Sensitive detection of acetylene (C2H2) is performed by absorption spectroscopy and wavelength modulation spectroscopy (WMS) based on Fiber Fabry-Perot tunable filter (FFP-TF) at 1530.32 nm. After being calibrated by Fiber Bragg Grating (FBG), FFP-TF is frequency-multiplexed and modulated at 20 Hz and 2.5 kHz respectively to achieve wavelength modulation. The linearity with 0.9907 fitting coefficient is obtained by measuring different concentrations in a 100 ppmv-400 ppmv range. Furthermore, the stability of the system is analyzed by detecting 50 ppmv and 100 ppmv standard gases for 2 h under room temperature and ambient pressure conditions respectively. The precision of 11 ppmv is achieved by calculating the standard deviation. Therefore, the measuring system of C2H2 detection can be applied in practical applications. Project supported by the National Natural Science Foundation of China (Grant Nos. 61172047 and 61071025).

  6. Infrared hyperspectral tunable filter imaging spectrometer for remote leak detection, chemical speciation, and stack/vent analysis applications

    NASA Astrophysics Data System (ADS)

    Hinnrichs, Michele

    2002-02-01

    With support from the Department of Energy, the State of California and the Gas Technology Institute, Pacific Advanced Technology is developing a small field portable infrared imaging spectrometer (Sherlock) based on the advances in hyperspectral tunable filter technology, that will be applied to the detection of fugitive gas leaks. This imaging spectrometer uses the Image Multi-spectral Sensing (IMSS) diffractive optic tunable filter invented by Pacific Advanced Technology . The Sherlock has an embedded digital signal processor for real time detection of the gas leak while surrounded by severe background noise. The infrared sensor engine is a 256 x 320 midwave cooled focal plane array which spans the spectral range from 3 to 5 microns, ideal for most hydrocarbon leaks. The technology is by no means limited to this spectral region, and can just as easily work in the longwave infrared from 8 to 12 microns for chemical detection applications. This paper will present the design of the Sherlock camera as well as processed data collected at a gas processing plant and an instrumented kiln at LSU using the prototype camera. The processed data shows that the IMSS imaging spectrometer, using an all passive approach, has the sensitivity to detect methane gas leaks at short range with a flow rate as low as 0.01 scfm2. In addition, the IMSS imaging spectrometer can measure hot gas plumes at longer ranges. As will be shown in this paper the IMSS can detect and image warm species gas additives of methane and propane in the Kiln exhaust stack. The methane injected gas with a concentration of 72 ppm and the propane with a concentration of 49 ppm (as seen by the IMSS sensor) at a range of 60 meters. The atmospheric path was a stressing environment, being hot and humid, for any imaging infrared spectrometer.

  7. Electrically tunable infrared filter based on the liquid crystal Fabry-Perot structure for spectral imaging detection.

    PubMed

    Zhang, Huaidong; Muhammmad, Afzal; Luo, Jun; Tong, Qing; Lei, Yu; Zhang, Xinyu; Sang, Hongshi; Xie, Changsheng

    2014-09-01

    An electrically tunable infrared (IR) filter based on the liquid crystal (LC) Fabry-Perot (FP) key structure, which works in the wavelength range from 5.5 to 12 μm, is designed and fabricated successfully. Both planar reflective mirrors with a very high reflectivity of ∼95%, which are shaped by depositing a layer of aluminum (Al) film over one side of a double-sided polished zinc selenide wafer, are coupled into a dual-mirror FP cavity. The LC materials are filled into the FP cavity with a thickness of ∼7.5  μm for constructing the LC-FP filter, which is a typical type of sandwich architecture. The top and bottom mirrors of the FP cavity are further coated by an alignment layer with a thickness of ∼100  nm over Al film. The formed alignment layer is rubbed strongly to shape relatively deep V-grooves to anchor LC molecules effectively. Common optical tests show some particular properties; for instance, the existing three transmission peaks in the measured wavelength range, the minimum full width at half-maximum being ∼120  nm, and the maximum adjustment extent of the imaging wavelength being ∼500  nm through applying the voltage driving signal with a root mean square (RMS) value ranging from 0 to ∼19.8  V. The experiment results are consistent with the simulation, according to our model setup. The spectral images obtained in the long-wavelength IR range, through the LC-FP device driven by the voltage signal with a different RMS value, demonstrates the prospect of the realization of smart spectral imaging and further integrating the LC-FP filter with IR focal plane arrays. The developed LC-FP filters show some advantages, such as electrically tunable imaging wavelength, very high structural and photoelectronic response stability, small size and low power consumption, and a very high filling factor of more than 95% compared with common MEMS-FP spectral imaging approaches. PMID:25321356

  8. High Power Continuous-Wave and Acousto-Optic Q-Switched Nd:GdVO4 Laser Operated at 912 nm

    NASA Astrophysics Data System (ADS)

    Gao, Jing; Yu, Xin; Chen, Fei; Li, Xu-Dong; Zhang, Zhen; Yu, Jun-Hua; Wang, Yue-Zhu

    2008-01-01

    We present a high power and efficient operation of the 4F3/2 → 4I9/2 transition in Nd:GdVO4 at 912nm. In the cw mode, the maximum output power of 8.6 W is achieved when the incident pump power is 40.3 W, leading to a slope efficiency of 33.3% and an optical-optical efficiency of 21.3%. To the best of our knowledge, this is the highest cw laser power at 912 nm obtained with the conventional Nd:GdVO4 crystal. Pulsed operation of 912 nm laser has also been realized by inserting a small acousto-optic (A-O) Q-Switch inside the resonator. As a result, the minimal pulse width of 20 ns and the average laser power 1.43 W at the repetition rate of 10 kHz are obtained, corresponding to 7.1 kW peak power. We believe that this is the highest laser peak power at 912nm. Furthermore, duration of 65ns has also been acquired when the repetition rate is 100kHz.

  9. 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.

  10. 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. PMID:26906364

  11. Efficient diode-pumped acousto-optic Q-switched Er:Yb:GdAl(3)(BO(3))(4) pulse laser at 1522  nm.

    PubMed

    Chen, Y J; Lin, Y F; Huang, J H; Gong, X H; Luo, Z D; Huang, Y D

    2015-11-01

    End-pumped by a continuous-wave 976 nm diode laser, efficient 1522 nm laser operation was demonstrated in an Er:Yb:GdAl(3)(BO(3))(4) crystal when a sapphire crystal was used as a heat diffuser. A continuous-wave 1522 nm laser with a maximum output power of 750 mW and slope efficiency of 36% was realized at an absorbed pump power of 4.1 W. The pulse performances of an acousto-optic Q-switched laser with various repetition frequencies were investigated in detail. In a repetition frequency range of 1-10 kHz, 1522 nm pulse lasers with a slope efficiency of about 10%, peak output power at the kilowatt level, and width of about 50 ns were first obtained in an Er:Yb:GdAl(3)(BO(3))(4) crystal pumped by a continuous-wave diode laser. The results indicate that the crystal is a promising gain medium for an actively Q-switched 1.5 μm laser.

  12. Optimization of doubly Q-switched lasers with both an acousto-optic modulator and a GaAs saturable absorber

    SciTech Connect

    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-pumpedNd3+: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.

  13. 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.

  14. Efficient diode-pumped acousto-optic Q-switched Er:Yb:GdAl(3)(BO(3))(4) pulse laser at 1522  nm.

    PubMed

    Chen, Y J; Lin, Y F; Huang, J H; Gong, X H; Luo, Z D; Huang, Y D

    2015-11-01

    End-pumped by a continuous-wave 976 nm diode laser, efficient 1522 nm laser operation was demonstrated in an Er:Yb:GdAl(3)(BO(3))(4) crystal when a sapphire crystal was used as a heat diffuser. A continuous-wave 1522 nm laser with a maximum output power of 750 mW and slope efficiency of 36% was realized at an absorbed pump power of 4.1 W. The pulse performances of an acousto-optic Q-switched laser with various repetition frequencies were investigated in detail. In a repetition frequency range of 1-10 kHz, 1522 nm pulse lasers with a slope efficiency of about 10%, peak output power at the kilowatt level, and width of about 50 ns were first obtained in an Er:Yb:GdAl(3)(BO(3))(4) crystal pumped by a continuous-wave diode laser. The results indicate that the crystal is a promising gain medium for an actively Q-switched 1.5 μm laser. PMID:26512485

  15. Optimization of peak power of doubly Q-switched lasers with both an acousto-optic modulator and a Cr4+-doped saturable absorber

    SciTech Connect

    Li Dechun; Zhao Shengzhi; Li Guiqiu; Yang Kejian

    2006-08-01

    A doubly Q-switched laser can obtain a shorter pulse with a stable repetition rate and high pulse peak power, which has been experimentally proved. By taking into account the Gaussian spatial distributions of the intracavity photon density and the initial population-inversion density as well as the influence of the acousto-optic (AO) Q switch, we introduce the coupled rate equations for a doubly Q-switched laser with both an AO modulator and a Cr4+-doped saturable absorber. These coupled rate equations are solved numerically. The key parameters of an optimally coupled doubly Q-switched laser are determined based on maximizing the peak power, which include the optimal normalized coupling parameter, the optimal normalized saturable absorber parameters, and the normalized parameters of the AO Q switch. The optimal normalized peak power, the corresponding normalized energy, and the normalized pulse width are also given, and a group of general curves are generated for the first time to our knowledge. The curves can give us a good understanding of the dependence of the optimal key parameters on the parameters of the gain medium, the saturable absorber, the AO Q switch, the resonator, and the spatial distributions of the intracavity photon density. The optimal calculations for a diode-pumped Nd3+:YVO4 laser with both an AO modulator and a Cr4+:YAG saturable absorber are presented to demonstrate the use of the curves and the related formulas.

  16. Employing dual-saturable-absorber-based filter for stable and tunable erbium-doped fiber ring laser in single-frequency

    NASA Astrophysics Data System (ADS)

    Yeh, C.-H.; Chow, C.-W.; Chen, K.-H.; Chen, J.-H.

    2011-05-01

    In this demonstration, a stable and wavelength-tunable erbium-doped fiber (EDF) ring laser using dual-saturable-absorber-based (DSAB) filter inside loop cavity is proposed and experimentally investigated. The proposed DSAB filter not only can filter the side-mode in single-frequency output, but also can obtain the flattened output power spectrum within 1 dB variation in the effectively range of 1529 to 1563 nm. In addition, the output stabilities of wavelength and power are also measured experimentally and discussed.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Fast wavelength-tunable picosecond pulses from a passively mode-locked Er fiber laser using a galvanometer-driven intracavity filter.

    PubMed

    Ozeki, Yasuyuki; Tashiro, Daigo

    2015-06-15

    We experimentally investigate fast wavelength-tuning characteristics of a polarization-maintaining Er fiber laser, which is mode-locked with a semiconductor saturable absorber mirror. Wavelength tuning was accomplished with an intracavity filter incorporating a galvanometer mirror and a diffraction grating. Within the tunability of 30 nm, we achieved a wavelength-tuning speed of <5 ms. We also show that the variation of repetition rates can be suppressed to <200 Hz by simply shifting the position of the grating. The presented scheme for generating wavelength-tunable pulses will be potentially useful for coherent Raman spectral imaging. PMID:26193501

  2. Tunable filter and optical buffer based on dual plasmonic ring resonators

    NASA Astrophysics Data System (ADS)

    Li, Boxun; Li, Hongjian; Zeng, Lili; Zhan, Shiping; Cao, Guangtao; He, Zhihui; Yang, Hui

    2015-02-01

    We demonstrate the realization of on chip plasmon-induced transparency using dual ring resonators coupling to metal-dielectric-metal bus waveguide. The theoretical results agree well with the finite-difference time-domain simulative ones. Moreover, by adjusting the radius, width, as well as the coupling distance can efficiently operate the wavelengths and bandwidths of our filter. In theory, we propose a feasible method to improve the trade-off between transmission and quality factor. Finally, the ultra-compact structure possesses slow light effect and manifests a low group velocity, which provides a guideline to control the light and has potential application in optical filter and optical buffer.

  3. 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.

  4. 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.

  5. Fluid-controlled tunable infrared filtering in hollow plasmonic nanofin cavities.

    PubMed

    Ho, Ya-Lun; Abasaki, Minoru; Yin, Shichen; Liu, Xin; Delaunay, Jean-Jacques

    2016-10-21

    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. PMID:27623320

  6. Bandwidth-tunable narrowband rectangular optical filter based on stimulated Brillouin scattering in optical fiber.

    PubMed

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

    2014-09-22

    We propose a rectangular optical filter based on stimulated Brillouin scattering (SBS) in optical fiber with bandwidth tuning from 50 MHz to 4 GHz at less than 15-MHz resolution. The rectangular shape of the filter is precisely achieved utilizing digital feedback control of the comb-like pump spectral lines. The passband ripple is suppressed to ~1 dB by mitigating the nonlinearity influences of the comb-like pump lines generated in electrical and optical components and fibers. Moreover a fiber with a single Brillouin peak is employed to further reduce the in-band ripple and the out-of-band SBS gain at the same time. Finally, we analyze the noise performance of the filter at different bandwidth cases and demonstrate the system performance of the proposed filter with 2.1-GHz bandwidth and 19-dB gain by amplifying a 2-GHz orthogonal frequency-division-multiplexing (OFDM) signal with quadrature-phase-shift-keying (QPSK) and 16-quadrature-amplitude-modulation (16-QAM) on each subscriber.

  7. A strain-tunable nanoimprint lithography for linear variable photonic crystal filters.

    PubMed

    Liu, Longju; Khan, Haris A; Li, Jingjing; Hillier, Andrew C; Lu, Meng

    2016-07-22

    This paper presents the fabrication methodology of a linear variable photonic crystal (PC) filter with narrowband reflection that varies over a broad spectral range along the length of the filter. The key component of the linear variable PC filter is a polymer surface-relief grating whose period changes linearly as a function of its position on the filter. The grating is fabricated using a nanoreplica molding process with a wedge-shaped elastomer mold. The top surface of the mold carries the grating pattern and the wedge is formed by a shallow angle between the top and bottom surfaces of the mold. During the replica molding process, a uniaxial force is applied to stretch the mold, resulting in a nearly linearly varying grating period. The period of the grating is determined using the magnitude of the force and the local thickness of the mold. The grating period of the fabricated device spans a range of 421.8-463.3 nm over a distance of 20 mm. A high refractive index dielectric film is deposited on the graded-period grating to act as the waveguide layer of the PC device. The resonance reflection feature of the device varies linearly in a range of 680.2-737.0 nm over the length of the grating. PMID:27276512

  8. A strain-tunable nanoimprint lithography for linear variable photonic crystal filters

    NASA Astrophysics Data System (ADS)

    Liu, Longju; Khan, Haris A.; Li, Jingjing; Hillier, Andrew C.; Lu, Meng

    2016-07-01

    This paper presents the fabrication methodology of a linear variable photonic crystal (PC) filter with narrowband reflection that varies over a broad spectral range along the length of the filter. The key component of the linear variable PC filter is a polymer surface-relief grating whose period changes linearly as a function of its position on the filter. The grating is fabricated using a nanoreplica molding process with a wedge-shaped elastomer mold. The top surface of the mold carries the grating pattern and the wedge is formed by a shallow angle between the top and bottom surfaces of the mold. During the replica molding process, a uniaxial force is applied to stretch the mold, resulting in a nearly linearly varying grating period. The period of the grating is determined using the magnitude of the force and the local thickness of the mold. The grating period of the fabricated device spans a range of 421.8-463.3 nm over a distance of 20 mm. A high refractive index dielectric film is deposited on the graded-period grating to act as the waveguide layer of the PC device. The resonance reflection feature of the device varies linearly in a range of 680.2-737.0 nm over the length of the grating.

  9. Fluid-controlled tunable infrared filtering in hollow plasmonic nanofin cavities.

    PubMed

    Ho, Ya-Lun; Abasaki, Minoru; Yin, Shichen; Liu, Xin; Delaunay, Jean-Jacques

    2016-10-21

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-01-01

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

  11. 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.

  12. Interface and post-processing requirements to insert an acousto-optic range-Doppler processor into an advanced radar digital signal processor

    NASA Astrophysics Data System (ADS)

    Durrett, Rodney A.; Dean, R.; McCarthy, Daniel F.; Viveiros, Edward A.; Caraway, Willie

    1995-06-01

    The interfacing and post-processing requirements for the development and insertion of an acousto-optic (AO), range-Doppler processor will be described. This system has been configured to operate as an integral part of the signal processing chain of an advanced spread- spectrum radar developed by the US Army Missile Command (MICOM). This MICOM radar transmits a continuous repeated, biphase-coded waveform and processes a block of received data to detect and track targets i range and Doppler in the presence of severe ground clutter. Multiple code rates are processed to extend the range window through application of residue number techniques. Range and Doppler processing are achieved in the AO processor using an additive triple-product processor architecture that coherently detects the range-Doppler information on a high-speed, custom 3D CCD detector array developed by the Army Research Laboratory. We present the interfaces to the radar and the post-processing of the data produced by the AO range-Doppler processor into the format required by the MICOM signal processor. The interfaces comprise the extraction of digital in-phase and quadrature data, the condition of this data for the AO range-Doppler processor, and the insertion of the post- processed optical data into the radar signal processor. Timing and latency issues are critical to real-time operation (creating range-Doppler images at approximately 1600 Hz frames rates) within the MICOM radar. The post-processing section cover optical processor architecture/post-processing tradeoffs, focusing on requirements, algorithms, and hardware implementation.

  13. 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

  14. 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.

  15. Ultra-compact, broadband tunable optical bandstop filters based on a multimode one-dimensional photonic crystal waveguide.

    PubMed

    Huang, Qingzhong; Jie, Kun; Liu, Qiang; Huang, Ying; Wang, Yi; Xia, Jinsong

    2016-09-01

    In this paper, ultra-compact, broadband tunable optical bandstop filters (OBSFs) based on a multimode one-dimensional photonic crystal waveguide (PhCW) are proposed and systematically investigated. For the wavelengths in the mini-stopband, the input mode is coupled to a contra-propagating higher order mode by the PhCW and then radiates in a taper, resulting in a stopband at the output with low backreflection at the input. Three-dimensional finite-difference time-domain method is employed to study the OBSFs. The influence of main structural parameters is analyzed, and the design is optimized to reduce the back-reflection and band sidelobes. Using localized heating, we can shift the stopband and tune the bandwidth continuously by cascading the proposed structures. Due to the strong grating strength, our device provides a more compact footprint (40 μm × 1 μm) and much broader stopband (bandwidth of up to 84 nm), compared to the counterparts based on microrings, long-period waveguide gratings, and multimode two-dimensional PhCWs. PMID:27607658

  16. 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.

  17. 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.

  18. An optimized strain demodulation method for PZT driven fiber Fabry-Perot tunable filter

    NASA Astrophysics Data System (ADS)

    Sheng, Wenjuan; Peng, G. D.; Liu, Yang; Yang, Ning

    2015-08-01

    An optimized strain-demodulation-method based on piezo-electrical transducer (PZT) driven fiber Fabry-Perot (FFP) filter is proposed and experimentally demonstrated. Using a parallel processing mode to drive the PZT continuously, the hysteresis effect is eliminated, and the system demodulation rate is increased. Furthermore, an AC-DC compensation method is developed to address the intrinsic nonlinear relationship between the displacement and voltage of PZT. The experimental results show that the actual demodulation rate is improved from 15 Hz to 30 Hz, the random error of the strain measurement is decreased by 95%, and the deviation between the test values after compensation and the theoretical values is less than 1 pm/με.

  19. 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

  20. Wavelength tunable Q-switch laser in visible region with Pr3+-doped fluoride-glass fiber pumped by GaN diode laser

    NASA Astrophysics Data System (ADS)

    Kojou, Junichiro; Watanabe, Yojiro; Agrawal, Priyanka; Kamimura, Toshihiro; Kannari, Fumihiko

    2013-03-01

    We demonstrate pulse laser operation of a 4-cm-long Pr3+-doped fluoride-glass fiber laser pumped by InGaN laser diodes (444 nm) using an acousto-optic modulator. We obtained maximum laser peak power of 105.6 W (2.1 μJ/pulse) with a pulse width of 20 ns at an 8.3-kHz repetition rate for a 607-nm wavelength. Employing a prism tuning cavity, we obtained wavelength tunable Q-switch pulse laser oscillation in the visible region (488-491, 520-526, 601-624, 631-644 nm).

  1. Analog optical processing and computing; Proceedings of the Meeting, Cambridge, MA, October 25, 26, 1984

    SciTech Connect

    Caulfield, H.J.

    1985-01-01

    Developments in optical signal processing are discussed, taking into account acousto-optic processors for passive surveillance, innovative and compact architectures for real-time two-dimensional correlation, scale-invariant Wigner distribution and ambiguity functions, an acousto-optic convolver for digital pulses, holography and four-wave mixing to see through the skin, the phase-conjugate of a Fourier hologram using four-wave mixing in BSO crystal, and a tunable, variable bandwidth, acousto-optic filter. Subjects related to pattern recognition are also explored, giving attention to optimal linear discriminant functions, orientation variability in generalized matched filters, an adaptive acousto-optic processor, an optical implementation of the synthetic discrimination function, and optimality considerations in modified matched spatial filters. A hybrid digital/integrated optical processor for on-line classification is considered along with white-light optical signal processing with a programmable magneto-optic device, and Lloyd's mirror as an optical processor.

  2. Tunable multi-wavelength erbium-doped fiber laser by cascading a standard Mach-Zehnder interferometer and a twin-core fiber-based filter

    NASA Astrophysics Data System (ADS)

    Yin, Guolu; Lou, Shuqin; Wang, Xin; Han, Bolin

    2013-12-01

    A tunable multi-wavelength erbium-doped fiber laser (MEDFL) based on a nonlinear optical loop mirror (NOLM) was proposed and experimentally demonstrated by cascading a standard Mach-Zehnder interferometer (MZI) and a twin-core fiber (TCF)-based filter. Due to the ‘blue shift’ of the transmission band of the TCF-based filter when the TCF was bent, a tunable lasing waveband was realized by moving the transmission band of the TCF-based filter to cover different channels provided by the standard MZI. Experimental results showed that the lasing waveband can be linearly tuned over a range of 24 nm from 1542 to 1566 nm with a channel spacing of 0.4 nm, a maximum lasing line amount of 19, and an optical signal to noise ratio (OSNR) of 39 dB. The stability of the laser spectra was verified with a wavelength drift of 0.04 nm and a power fluctuation of ±0.3 dB.

  3. 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.

  4. A novel tunable filter featuring defect mode of the TE wave from one-dimensional photonic crystals doped by magnetized plasma

    SciTech Connect

    Kong Xiangkun; Liu Shaobin; Li Chunzao; Zhang Haifeng

    2010-10-15

    A novel tunable filter featuring the defect mode of the TE wave from one-dimensional photonic crystals doped by magnetized plasma is presented. The photonic crystals are composed by SiO{sub 2} and air with one defect layer made by magnetized plasma. By the transfer matrix method and Bloch's theorem, we find out that the frequency of the defect mode can be modulated by plasma density or external magnetic field. Without changing the structure of the photonic crystal, the defect mode can be modulated in a larger frequency range, especially when the left-hand polarized electromagnetic wave is utilized.

  5. 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.

  6. 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.

  7. 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.

  8. Modulation frequency characteristics of the Q-switched envelope in a doubly Q-switched and mode-locked laser with acousto-optic modulator and Cr4+:YAG saturable absorber

    NASA Astrophysics Data System (ADS)

    Qiao, Junpeng; Zhao, Jia; Li, Yufei; Zhao, Shengzhi; Li, Guiqiu; Li, Dechun; Qiao, Wenchao; Chu, Hongwei

    2015-11-01

    The modulation frequency characteristics of the Q-switched envelope in a doubly Q-switched and mode-locked Nd:GGG laser with an acousto-optic modulator (AOM) and Cr4+:YAG saturable absorber are given. At a fixed incident pump power, the repetition rates of the Q-switched envelope and the related laser characteristics versus the modulation frequency of AOM for different small signal transmissions of Cr4+:YAG saturable absorbers have been measured. The experimental results show that the repetition rates of the Q-switched envelope, the average output power, the average peak power, and the pulse widths of the Q-switched envelopes are subharmonics of the modulation frequency at a fixed incident pump power. Furthermore, the mechanism for these behaviors is discussed.

  9. 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.

  10. 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. PMID:24977602

  11. Ultrawide continuously tunable 1.55-μm vertical-air-cavity filters and VCSELs based on micromachined electrostatic actuation

    NASA Astrophysics Data System (ADS)

    Hillmer, Hartmut; Daleiden, Juergen; Prott, Cornelia; Roemer, Friedhard; Tarraf, Amer; Irmer, Soeren; Rangelov, Ventzeslav; Schueler, S.; Strassner, Martin

    2002-06-01

    We study 1.55micrometers filter and VCSEL devices capable of wide and continuous tuning based on a single control parameter. Ultra-high reflective DBR mirrors are realized with a low number of DBR periods using high refractive index contrast: (I) (Delta) n=2.17 for InP/airgap DBR's (3.5 periods) and (II) (Delta) n=0.5 for Si3N4/SiO2 DBR's (12 periods) with a polymer sacrificial layer to implement the air-cavity. Corresponding fabrication technologies are presented in detail. In both cases spectral tuning (>100nm, theoretically) is obtained by micomachined actuation of the included air-cavity. Large stopband widths and very large tuning efficiencies are obtained by model calculations. For VCSEL's a trade-off between lasing efficiency and tuning efficiency is obtained. Experimental results show very good optical properties: high mirror reflectance and clear single-line filter transmission. The first tunable dielectric filter based on polymer sacrificial layers is presented: (Delta) (lambda) /(Delta) U= -7nm/V at 1mA. The potential of the airgap concept: the filter transmission or the laser emission wavelength can be continuously tuned over more than 100nm, thus, the whole spectral gain profile can be addressed by a single control parameter.

  12. 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.

  13. Tunable and switchable dual-wavelength erbium-doped fiber laser based on in-line tapered fiber filters

    NASA Astrophysics Data System (ADS)

    Tong, Zheng-rong; Yang, He; Cao, Ye

    2016-07-01

    A tunable and switchable dual-wavelength erbium-doped fiber laser (EDFL) based on all-fiber single-mode tapered fiber structure has been demonstrated. By adjusting the variable optical attenuator (VOA), the laser can be switched between the single-wavelength mode and the dual-wavelength mode. When the temperature applied on the tapered fiber structure varies, the pass-band varies and the wavelength of the output laser shifts correspondingly. When the temperature changes from 30 °C to 180 °C, the central wavelength of the EDFL generated by branch A shifts from 1 550.7 nm to 1 560.3 nm, while that of branch B shifts from 1 530.8 nm to 1 540.4 nm, indicating the wavelength interval is tunable. These advantages enable this laser to be a potential candidate for high-capacity wavelength division multiplexing systems and mechanical sensors.

  14. Flat-top bandpass microwave photonic filter with tunable bandwidth and center frequency based on a Fabry-Pérot semiconductor optical amplifier.

    PubMed

    Jiang, Fan; Yu, Yuan; Cao, Tong; Tang, Haitao; Dong, Jianji; Zhang, Xinliang

    2016-07-15

    We propose a flat-top bandpass microwave photonic filter (MPF) with flexible tunability of the bandwidth and center frequency based on optical nonlinearities in a Fabry-Pérot semiconductor optical amplifier (FP-SOA). Phase-inverted modulation induced by cross-gain modulation (XGM) and optical spectral broadening induced by self-phase modulation (SPM) are exploited to achieve flat-top and bandwidth tuning, respectively. Wideband and continuous tuning of the center frequency is achieved by altering the bias current of the FP-SOA. Experimental results demonstrate a flat-top single-passband MPF with its center frequency tunable from 6.0 to 18.3 GHz by adjusting the bias current from 54.05 to 107.85 mA. The 3-dB bandwidth of the passband when centered at 10.0 GHz is shown to be variable from 680 to 1.43 GHz, by increasing the injected optical power from -1 to +5  dBm. During the bandwidth tuning, the amplitude ripple within the passband is maintained at less than ±0.5  dB. Excellent main to secondary sidelobe ratio exceeding 45 dB is achieved when the MPF is centered at 18.3 GHz.

  15. Flat-top bandpass microwave photonic filter with tunable bandwidth and center frequency based on a Fabry-Pérot semiconductor optical amplifier.

    PubMed

    Jiang, Fan; Yu, Yuan; Cao, Tong; Tang, Haitao; Dong, Jianji; Zhang, Xinliang

    2016-07-15

    We propose a flat-top bandpass microwave photonic filter (MPF) with flexible tunability of the bandwidth and center frequency based on optical nonlinearities in a Fabry-Pérot semiconductor optical amplifier (FP-SOA). Phase-inverted modulation induced by cross-gain modulation (XGM) and optical spectral broadening induced by self-phase modulation (SPM) are exploited to achieve flat-top and bandwidth tuning, respectively. Wideband and continuous tuning of the center frequency is achieved by altering the bias current of the FP-SOA. Experimental results demonstrate a flat-top single-passband MPF with its center frequency tunable from 6.0 to 18.3 GHz by adjusting the bias current from 54.05 to 107.85 mA. The 3-dB bandwidth of the passband when centered at 10.0 GHz is shown to be variable from 680 to 1.43 GHz, by increasing the injected optical power from -1 to +5  dBm. During the bandwidth tuning, the amplitude ripple within the passband is maintained at less than ±0.5  dB. Excellent main to secondary sidelobe ratio exceeding 45 dB is achieved when the MPF is centered at 18.3 GHz. PMID:27420520

  16. Ultra-narrow angle-tunable Fabry-Perot bandpass interference filter for use as tuning element in infrared lasers

    NASA Astrophysics Data System (ADS)

    Kischkat, Jan; Peters, Sven; Semtsiv, Mykhaylo P.; Wegner, Tristan; Elagin, Mikaela; Monastyrskyi, Grygorii; Flores, Yuri; Kurlov, Sergii; Masselink, W. Ted

    2014-11-01

    We have developed a bandpass infrared interference filter with sufficiently narrow bandwidth to be potentially suitable for tuning a self-stabilizing external-cavity quantum-cascade laser (ECQCL) in single-mode operation and describe the process parameters for fabrication of such filters with central wavelengths in the 3-12 μm range. The filter has a passband width of 6 nm or 0.14% with peak transmission of 55% and a central wavelength of approximately 4.0 μm. It can be tuned through over 4% by tilting with respect to the incident beam and offers orders of magnitude larger angular dispersion than diffraction gratings. We compare filters with single-cavity and coupled-cavity Fabry-Perot designs.

  17. 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

  18. 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.

  19. Diode-pumped acousto-optical Q-switched 912 nm Nd:GdVO4 laser and extra-cavity frequency-doubling of 456 nm deep-blue light emission

    NASA Astrophysics Data System (ADS)

    Chen, F.; Yu, X.; Zhang, K.; He, Y.; Zheng, C. B.; Wang, C. R.; Guo, J.

    2015-05-01

    In this paper, a diode-pumped acousto-optical (A-O) Q-switched 912 nm Nd:GdVO4 laser and pulsed 456 nm deep-blue light emission by extra-cavity frequency-doubling are demonstrated. To compensate the serious thermal-lensing effect in laser crystal, a compact unstable resonator is used. At an incident pump power of 49.5 W, a maximum average output power of 2.3 W 912 nm laser is obtained at 10 kHz, corresponding to an optical conversion efficiency of 4.6% and a slope efficiency of 9.2%. Minimum pulse width of 20 ns and maximum peak power of 10.5 kW 912 nm laser are achieved at a pump power of 45.3 W. Using a BiBO crystal as the frequency-doubler, maximum average output power of 623 mW 456 nm deep-blue light is obtained at 10 kHz, with a pulse width of 21.3 ns and a peak power of 2.3 kW. Moreover, stable operating repetition rate of 912 nm laser and 456 nm deep-blue light is up to 100 kHz.

  20. 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. PMID:24085093