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Journal articles on the topic 'Acoustic Optical Tunable Filter (AOTF)'

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Published: 4 June 2021

Last updated: 1 February 2022

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1

Hueber, Dennis M., Christopher L. Stevenson, and Tuan Vo-Dinh. "Fast Scanning Synchronous Luminescence Spectrometer Based on Acousto-Optic Tunable Filters." Applied Spectroscopy 49, no. 11 (November 1995): 1624–31. http://dx.doi.org/10.1366/0003702953965830.

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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.

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2

PRASAD, NARASIMHA S. "DEEP-UV BASED ACOUSTO-OPTIC TUNABLE FILTER FOR SPECTRAL SENSING APPLICATIONS." International Journal of High Speed Electronics and Systems 17, no. 04 (December 2007): 857–66. http://dx.doi.org/10.1142/s012915640700503x.

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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 ∼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.

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3

Moreau, Frédérick, Sandrine M. Moreau, Dennis M. Hueber, and Tuan Vo-Dinh. "Fiber-Optic Remote Multisensor System Based on an Acousto-Optic Tunable Filter (AOTF)." Applied Spectroscopy 50, no. 10 (October 1996): 1295–300. http://dx.doi.org/10.1366/0003702963904917.

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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.

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4

Turner, John F., and Patrick J. Treado. "Near-Infrared Acousto-Optic Tunable Filter Hadamard Transform Spectroscopy." Applied Spectroscopy 50, no. 2 (February 1996): 277–84. http://dx.doi.org/10.1366/0003702963906609.

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The acousto-optic tunable filter (AOTF) is a digitally accessible, compact, solid-state spectrometer that is well suited to high-frequency optical switching and wavelength selection. With injection of a combination of radio-frequency signals into its transducer, the AOTF acts as an electronically controllable, multiplexing spectrometer. The multiplexing AOTF in this study is employed in two distinct fashions. The first of these utilizes the multiplexing AOTF as a matched filter whose intended spectral profile (i.e., bandpass and band symmetry) is controlled almost at will, providing unprecedented flexibility and high throughput. Second, the multiplexing AOTF is employed for the first time as a Hadamard transform spectrometer. In operation, the integrated intensity on the detector measures combinations of the diffracted wavelengths. The light encodement is performed without the use of physical masks and is governed by HT mathematics, which allow efficient recovery of the optical spectrum. Appreciable signal-to-noise enhancement is demonstrated with the HT AOTF spectrometer.

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5

Batshev, Vladislav, Alexander Machikhin, Grigoriy Martynov, Vitold Pozhar, Sergey Boritko, Milana Sharikova, Vladimir Lomonov, and Alexander Vinogradov. "Polarizer-Free AOTF-Based SWIR Hyperspectral Imaging for Biomedical Applications." Sensors 20, no. 16 (August 8, 2020): 4439. http://dx.doi.org/10.3390/s20164439.

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Optical biomedical imaging in short wave infrared (SWIR) range within 0.9–1.7 μm is a rapidly developing technique. For this reason, there is an increasing interest in cost-effective and robust hardware for hyperspectral imaging data acquisition in this range. Tunable-filter-based solutions are of particular interest as they provide image processing flexibility and effectiveness in terms of collected data volume. Acousto-optical tunable filters (AOTFs) provide a unique set of features necessary for high-quality SWIR hyperspectral imaging. In this paper, we discuss a polarizer-free configuration of an imaging AOTF that provides a compact and easy-to-integrate design of the whole imager. We have carried out image quality analysis of this system, assembled it and validated its efficiency through multiple experiments. The developed system can be helpful in many hyperspectral applications including biomedical analyses.

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6

Treado, Patrick J., Ira W. Levin, and E. Neil Lewis. "Indium Antimonide (InSb) Focal Plane Array (FPA) Detection for Near-Infrared Imaging Microscopy." Applied Spectroscopy 48, no. 5 (May 1994): 607–15. http://dx.doi.org/10.1366/0003702944924899.

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Near-infrared spectroscopy is a sensitive, noninvasive method for chemical analyses, and its integration with imaging technologies represents a potent tool for the study of a wide range of materials. In this communication the use of an indium antimonide (InSb) multichannel imaging detector for near-infrared absorption spectroscopic microscopy is described. In particular, a 128 × 128 pixel InSb staring array camera has been combined with a refractive optical microscope and an acousto-optic tunable filter (AOTF) to display chemically discriminative, spatially resolved, vibrational spectroscopic images of biological and polymeric systems. AOTFs are computer-controlled bandpass filters that provide high speed, random wavelength access, wide spectral coverage, and high spectral resolution. Although AOTFs inherently have a wide range of spectroscopic applications, we apply this technology to NIR absorption microscopy between 1 and 2.5 μm. The spectral interval is well matched to the optical characteristics of both the NIR refractive microscope and the AOTF, thereby providing near-diffraction-limited performance with a practical spatial resolution of 1 to 2 μm. Design principles of this novel instrumentation and representative applications of the technique are presented for various model systems.

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7

Han, Xiaofang, Yue Hu, Jiwei Li, Pengfa Chang, Feng Gao, Xiao Dong, Fang Bo, Wending Zhang, Guoquan Zhang, and Jingjun Xu. "All-Fiber Frequency Shifter Based on an Acousto-Optic Tunable Filter Cascaded with a Tapered Fiber-Coupled Microcavity." Crystals 11, no. 5 (May 1, 2021): 497. http://dx.doi.org/10.3390/cryst11050497.

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An all-fiber acousto-optic frequency shifter (AOFS) based on an acousto-optic tunable filter (AOTF) cascaded with a packaged tapered fiber (TF)-coupled microsphere was proposed and demonstrated in both theory and experiment. The configuration has the advantages of easy alignment, robustness, compact size, and low cost, which will improve its further application, such as in the optical heterodyne detection technique (OHDT).

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Sabóia, Karlo David Alves, Alex Sander Barros Queiroz, Francisco Tiago Lima, Cícero Saraiva Sobrinho, Jose Wally Mendonça Menezes, and Antonio Sergio Bezerra Sombra. "Optical Bistability in an Acousto-Optic Tunable Filter (AOTF) Operating with Short Optical Pulses." Journal of Electromagnetic Analysis and Applications 04, no. 03 (2012): 112–17. http://dx.doi.org/10.4236/jemaa.2012.43015.

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Sabóia, K. D. A., A. C. Ferreira, C. S. Sobrinho, W. B. Fraga, J. W. M. Menezes, M. L. Lyra, and A. S. B. Sombra. "Optical cryptography under PPM-PAM modulation based in short optical pulses in an acoustic-optic tunable filter (AOTF)." Optical and Quantum Electronics 41, no. 14-15 (December 2009): 963–80. http://dx.doi.org/10.1007/s11082-010-9409-8.

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10

Sobrinho, C. S., A. F. G. F. Filho, J. C. Sales, A. F. M. Neto, E. F. De Almeida, and A. S. B. Sombra. "Acousto-Optic Tunable Filter (AOTF) Revisited: Ultrashort Optical Pulses Crosstalk Studies on the Lossy Filter." Fiber and Integrated Optics 25, no. 3 (July 2006): 195–211. http://dx.doi.org/10.1080/01468030600569834.

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11

GUPTA, NEELAM. "HYPERSPECTRAL AND POLARIZATION IMAGING WITH DOUBLE-TRANSDUCER AOTFS FOR WIDER SPECTRAL COVERAGE." International Journal of High Speed Electronics and Systems 17, no. 04 (December 2007): 845–55. http://dx.doi.org/10.1142/s0129156407005028.

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We have developed a number of programmable hyperspectral imagers operating from the ultraviolet to the longwave infrared using an acousto-optic tunable filter (AOTF) in conjunction with a suitable camera. Each of these AOTFs is fabricated with a single transducer to operate over only one octave in wavelength. Recently, we have developed two separate tellurium dioxide ( TeO 2) noncollinear AOTF cells that operate over two octave range. Each cell has an aperture of 1.5 × 1.5 cm 2 with a field-of-view of 4.2°, and two thin-plate lithium niobate transducers are bonded on it. The tuning range of the first cell is 0.43–2.1 μm , and 0.69–4.0 μm for the second cell. We have used each of these cells to carry out spectral imaging experiments with CCD, InGaAs , and InSb cameras to cover the spectral region from the visible to the midwave infrared. We image the two orthogonally polarized diffracted beams to get spectropolarimetric information from the scene, as well as a broadband image by using one of the undiffracted beams. In this paper, we discuss the two AOTF cells, the imaging experiments, and present the results obtained.

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Machikhin, Alexander, Vitold Pozhar, and Vladislav Batshev. "Double-AOTF-based aberration-free spectral imaging endoscopic system for biomedical applications." Journal of Innovative Optical Health Sciences 08, no. 03 (May 2015): 1541009. http://dx.doi.org/10.1142/s1793545815410096.

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The problem of in vivo photoluminescence diagnostics of the tissues accessible by endoscopes is discussed. The spectral imaging module attachable to conventional rigid and flexible medical endoscopes is developed and described. It is based on a double acousto-optical tunable filter (AOTF) and a specialized optical coupling system. The module provides wide field of view (FOV), absence of image distortions, random spectral access, fast spectral image acquisition at any wavelength in the visible range and accurate measurement of reflectance spectrum in each pixel of the image. Images of typical biomedical samples are presented and discussed. Their spectra are compared to the reference data.

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13

Sato, Hidetoshi, Norihito Saito, Kazuyuki Akagawa, Satoshi Wada, and Hideo Tashiro. "Electronically Tunable-Laser Light Sources for near Infrared Spectroscopy." Journal of Near Infrared Spectroscopy 11, no. 4 (August 2003): 295–308. http://dx.doi.org/10.1255/jnirs.375.

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This review paper focuses primarily on the recent progress in the development of electronically-tuned solid-state lasers and their application in near infrared (NIR) absorption and Raman spectroscopies. It also discusses the expansion of the tunable range and the generation of ultrashort pulses. Electronic control of laser wavelengths using an acousto-optical tunable filter (AOTF) was developed to provide rapid, accurate and random access to numerous wavelengths offering a programmable monochromatic energy under computer control. In contrast to tunable diode lasers that are for specific gaseous spectroscopic analysis, this type of stable, widely-tunable lasers is suited for the measurement of both liquid and solid samples, including biological materials, materials that have broad and overlapping features over a wide spectral range. In addition, some preliminary applications are presented, together with the present status of other tunable light sources applicable for NIR spectroscopy.

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14

da Silva, M. G., R. S. de Oliveira, and A. S. B. Sombra. "Ultra-short pulse propagation in a lossy acousto-optic tunable filter (AOTF)." Microwave and Optical Technology Letters 28, no. 5 (2001): 346–50. http://dx.doi.org/10.1002/1098-2760(20010305)28:5<346::aid-mop1037>3.0.co;2-o.

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15

Skinner, H. Trey, Thomas F. Cooney, S. K. Sharma, and S. M. Angel. "Remote Raman Microimaging Using an AOTF and a Spatially Coherent Microfiber Optical Probe." Applied Spectroscopy 50, no. 8 (August 1996): 1007–14. http://dx.doi.org/10.1366/0003702963905330.

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A fiber-optic Raman microimaging probe is described that is suitable for acquiring high-spatial-resolution Raman images in sampling situations with no clear line of sight. A high-power near-infrared diode laser combined with an acousto-optic tunable filter and a spatially coherent optical fiber bundle allow fluorescence-free Raman images of remotely located samples to be acquired at distances up to several meters. The feasibility of this technique is demonstrated with Raman images of (1) a pellet containing a mixture of a highly scattering sample, bis-methylstyrylbenzene (BMSB), KCl, and graphite, and (2) a partially graphitized diamond. These images clearly show phase boundaries over an area of approximately 0.1 mm2 with ∼4-μm resolution.

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STOPA, PETER J., JOLANTA I. SOOS, RONALD G. ROSEMEIER, SUDHIR B. TRIVEDI, and SUSAN W. KUTCHER. "DEVELOPMENT OF MINIATURE ACOUSTO OPTIC TUNABLE FILTER (AOTF) SPECTROMETER FOR DETECTION OF TOXIC INDUSTRIAL CHEMICALS (TICS)." International Journal of High Speed Electronics and Systems 17, no. 04 (December 2007): 867–76. http://dx.doi.org/10.1142/s0129156407005041.

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This paper describes a remotely operable miniature spectrometer for the detection of Toxic Industrial Chemicals (TIC) using Near Infra-Red (NIR) spectroscopy. The spectrometer discussed here is compact, rugged and capable of operating on either as a handheld unit or on robotic platforms. The packaged unit consists of two modules: an optical head unit and an electronics unit. The optical head contains an infra-red light source, an Acousto-Optical Tunable Filter (AOTF) spectrometer, and associated electronics. The other module is contains the associated electronics assembly and cables connecting it with the optical head. This unit has fiber optic and free space detection capabilities and can be operated using 24 V battery power packs. We have developed a method to detect unknown chemical threat using measured signatures of known chemicals and chemometric techniques. At this time the system can detect chemicals in solid and liquid forms. We are currently optimizing the system for detection of chemicals in gaseous/vapor forms.

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Wakayama, Toshitaka, Toru Yoshizawa, and Yukitoshi Otani. "Spectroscopic Birefringence Mapping by Channeled Spectrum." Applied Mechanics and Materials 70 (August 2011): 452–57. http://dx.doi.org/10.4028/www.scientific.net/amm.70.452.

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Birefringence mapping of objects has attracted great interest in the fields of material technology and biomedical science. This paper describes spectroscopic birefringence mapping using a channeled spectrum. To perform spectroscopic birefringence mapping using a microscope, an acousto-optical tunable filter (AOTF) was employed as a spectrometer. The AOTF can select a specific wavelength from a white light source. The optical arrangement consists of a white light source, the AOTF, a polarizer, two retarders with high-order retardance, two objective lenses, an analyzer, and a CCD camera. The polarizer and the first retarder can modulate the polarization state and they function as polarizing optics, while the second retarder and the analyzer can analyze the polarization state and they function as analyzing optics. A sample is inserted between the polarizing and analyzing optics. Images obtained at a specific wavelength generate 128 data points at visible wavelengths. A channeled spectrum (i.e., the intensity distribution) can be generated from the images obtained. A Fourier spectrum can be obtained by the fast Fourier transform (FFT) method. The birefringence properties of the sample can be derived by calculating the inverse FFT. We used this technique to measure the polarization properties of a nematic liquid crystal droplet.

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SOBRINHO, C. S., M. V. N. DE OLIVEIRA, M. G. DA SILVA, J. L. S. LIMA, E. F. DE ALMEIDA, and A. S. B. SOMBRA. "Numerical Analysis of the Crosstalk on an Integrated Acousto-Optic Tunable Filter (AOTF) for Network Applications." Fiber and Integrated Optics 23, no. 5 (January 2004): 345–63. http://dx.doi.org/10.1080/01468030490489509.

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19

Jiang, Changhui, Yuwei Chen, Haohao Wu, Wei Li, Hui Zhou, Yuming Bo, Hui Shao, Shaojin Song, Eetu Puttonen, and Juha Hyyppä. "Study of a High Spectral Resolution Hyperspectral LiDAR in Vegetation Red Edge Parameters Extraction." Remote Sensing 11, no. 17 (August 26, 2019): 2007. http://dx.doi.org/10.3390/rs11172007.

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Non-contact and active vegetation or plant parameters extraction using hyperspectral information is a prospective research direction among the remote sensing community. Hyperspectral LiDAR (HSL) is an instrument capable of acquiring spectral and spatial information actively, which could mitigate the environmental illumination influence on the spectral information collection. However, HSL usually has limited spectral resolution and coverage, which is vital for vegetation parameter extraction. In this paper, to broaden the HSL spectral range and increase the spectral resolution, an Acousto-optical Tunable Filter based Hyperspectral LiDAR (AOTF-HSL) with 10 nm spectral resolution, consecutively covering from 500–1000 nm, was designed. The AOTF-HSL was employed and evaluated for vegetation parameters extraction. “Red Edge” parameters of four different plants with green and yellow leaves were extracted in the lab experiments for evaluating the HSL vegetation parameter extraction capacity. The experiments were composed of two parts. Firstly, the first-order derivative of the spectral reflectance was employed to extract the “Red Edge” position (REP), “Red Edge” slope (RES) and “Red Edge” area (REA) of these green and yellow leaves. The results were compared with the referenced value from a standard SVC© HR-1024 spectrometer for validation. Green leaf parameter differences between HSL and SVC results were minor, which supported that notion the HSL was practical for extracting the employed parameter as an active method. Secondly, another two different REP extraction methods, Linear Four-point Interpolation technology (LFPIT) and Linear Extrapolation technology (LET), were utilized for further evaluation of using the AOTF-HSL spectral profile to determine the REP value. The differences between the plant green leaves’ REP results extracted using the three methods were all below 10%, and the some of them were below 1%, which further demonstrated that the spectral data collected from HSL with this spectral range and resolution settings was applicable for “Red Edge” parameters extraction.

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Eilert, A. J., J. A. Sweat, and D. L. Wetzel. "Parabolic Concentration of Diffusely Transmitted near Infrared Radiation in an Acousto-Optic Tunable Filter Spectrometer." Journal of Near Infrared Spectroscopy 8, no. 4 (October 2000): 239–50. http://dx.doi.org/10.1255/jnirs.284.

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The research model near infrared (NIR) spectrometer described in this paper, worthy of quantitative use and suited for industrial applications, is the result of stepwise refinement of the acousto-optic tunable filter (AOTF)-based monochromator and other optical components. A sensitive and rapid response extended-range indium gallium arsenide (InGaAs) detector (covering the 1100–2500 nm range) was selected to match the high speed of acousto-optic TFS electronic wavelength switching. Excellent quantitative performance has been demonstrated in comparison with commercial grating monochromator and Fourier transform (FT)-NIR instruments for multi-component liquids, films, pumped fluids and even supercritical fluids. Software-controlled wavelength switching, data acquisition and programmed or interactive time averaging at each wavelength demonstrated analytically-enhanced performance. Throughput is not limited by slits, and exposure of the sample to white light, as with a diode array or an FT instrument, is avoided. Although focusing optics between sample and detector were found to work well for concentrating radiation on a small surface area InGaAs detector, detector size limited performance in the case of optically difficult samples because of the low solid angle of collection. Use of an experimental non-focusing multistage parabolic concentrator immediately after the sample vessel and before the 1 mm2 detector was found to offer an advantage for highly scattering specimens. Although the reflection optics of the locally fabricated concentrator directed a lower intensity of light transmitted by clear specimens than from the standard lens arrangement, successful analysis was extended to include highly scattering samples. The percentage of incident radiation attenuated via scatter was reduced, and for scatter beyond a point, the absolute intensity of radiation falling on the detector was greater, even though the absolute maximum of non-scattered intensity was less, thus establishing proof of principle. We anticipate that further improvement could be attained for highly scattering samples with a commercial optics manufacturer's version of the homemade concentrator.

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Qin Xiage, 秦侠格, 姬忠鹏 Ji Zhongpeng, 徐映宇 Xu Yingyu, and 舒. 嵘. Shu Rong. "High-precision measurement method and device on diffraction efficiency of Acousto-Optic Tunable Filter based on double-optical-path and cross-references." Infrared and Laser Engineering 46, no. 4 (2017): 417001. http://dx.doi.org/10.3788/irla201746.0417001.

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22

Dekemper, Emmanuel, Jurgen Vanhamel, Bert Van Opstal, and Didier Fussen. "The AOTF-based NO<sub>2</sub> camera." Atmospheric Measurement Techniques 9, no. 12 (December 15, 2016): 6025–34. http://dx.doi.org/10.5194/amt-9-6025-2016.

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Abstract. The abundance of NO2 in the boundary layer relates to air quality and pollution source monitoring. Observing the spatiotemporal distribution of NO2 above well-delimited (flue gas stacks, volcanoes, ships) or more extended sources (cities) allows for applications such as monitoring emission fluxes or studying the plume dynamic chemistry and its transport. So far, most attempts to map the NO2 field from the ground have been made with visible-light scanning grating spectrometers. Benefiting from a high retrieval accuracy, they only achieve a relatively low spatiotemporal resolution that hampers the detection of dynamic features. We present a new type of passive remote sensing instrument aiming at the measurement of the 2-D distributions of NO2 slant column densities (SCDs) with a high spatiotemporal resolution. The measurement principle has strong similarities with the popular filter-based SO2 camera as it relies on spectral images taken at wavelengths where the molecule absorption cross section is different. Contrary to the SO2 camera, the spectral selection is performed by an acousto-optical tunable filter (AOTF) capable of resolving the target molecule's spectral features. The NO2 camera capabilities are demonstrated by imaging the NO2 abundance in the plume of a coal-fired power plant. During this experiment, the 2-D distribution of the NO2 SCD was retrieved with a temporal resolution of 3 min and a spatial sampling of 50 cm (over a 250 × 250 m2 area). The detection limit was close to 5 × 1016 molecules cm−2, with a maximum detected SCD of 4 × 1017 molecules cm−2. Illustrating the added value of the NO2 camera measurements, the data reveal the dynamics of the NO to NO2 conversion in the early plume with an unprecedent resolution: from its release in the air, and for 100 m upwards, the observed NO2 plume concentration increased at a rate of 0.75–1.25 g s−1. In joint campaigns with SO2 cameras, the NO2 camera could also help in removing the bias introduced by the NO2 interference with the SO2 spectrum.

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Elash, B. J., A. E. Bourassa, P. R. Loewen, N. D. Lloyd, and D. A. Degenstein. "The Aerosol Limb Imager: acousto-optic imaging of limb-scattered sunlight for stratospheric aerosol profiling." Atmospheric Measurement Techniques 9, no. 3 (March 24, 2016): 1261–77. http://dx.doi.org/10.5194/amt-9-1261-2016.

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Abstract. 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.

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Elash, B. J., A. E. Bourassa, P. R. Loewen, N. D. Lloyd, and D. A. Degenstein. "The Aerosol Limb Imager: acousto-optic imaging of limb scattered sunlight for stratospheric aerosol profiling." Atmospheric Measurement Techniques Discussions 8, no. 12 (December 17, 2015): 13285–330. http://dx.doi.org/10.5194/amtd-8-13285-2015.

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Abstract. 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.

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25

Batshev, Vladislav, Alexander Machikhin, Alexey Gorevoy, Grigoriy Martynov, Demid Khokhlov, Sergey Boritko, Vitold Pozhar, and Vladimir Lomonov. "Spectral Imaging Experiments with Various Optical Schemes Based on the Same AOTF." Materials 14, no. 11 (May 31, 2021): 2984. http://dx.doi.org/10.3390/ma14112984.

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Spectral image filtration by means of acousto-optical tunable filters (AOTFs) has multiple applications. For its implementation, a few different optical schemes are in use. They differ in image quality, number of coupling components, dimensions and alignment complexity. To choose the optical system of AOTF-based spectral imager properly, many factors have to be considered. Though various schemes of acousto-optic (AO) filtration have been tested and discussed, their comparative analysis has not been reported up to now. In this study, we assembled the four most popular schemes (confocal, collimating, tandem and double-path) using the same AO cells and experimentally compared their main features. Depending on the application, each scheme may be the basis of compact cost-effective spectral imaging devices.

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Chen, Yuwei, Wei Li, Juha Hyyppä, Ning Wang, Changhui Jiang, Fanrong Meng, Lingli Tang, Eetu Puttonen, and Chuanrong Li. "A 10-nm Spectral Resolution Hyperspectral LiDAR System Based on an Acousto-Optic Tunable Filter." Sensors 19, no. 7 (April 4, 2019): 1620. http://dx.doi.org/10.3390/s19071620.

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Hyperspectral LiDAR (HSL) technology can obtain spectral and ranging information from targets by processing the recorded waveforms and measuring the time of flight (ToF). With the development of the supercontinuum laser (SCL), it is technically easier to develop an active hyperspectral LiDAR system that can simultaneously collect both spatial information and extensive spectral information from targets. Compared with traditional LiDAR technology, which can only obtain range and intensity information at the selected spectral wavelengths, HSL detection technology has demonstrated its potential and adaptability for various quantitative applications from its spectrally resolved waveforms. However, with most previous HSLs, the collected spectral information is discrete, and such information might be insufficient and restrict the further applicability of the HSLs. In this paper, a tunable HSL technology using an acousto-optic tunable filter (AOTF) as a spectroscopic device was proposed, designed, and tested to address this issue. Both the general range precision and the accuracy of the spectral measurement were evaluated. By tuning the spectroscopic device in the time dimension, the proposed AOTF-HSL could achieve backscattered echo with continuous coverage of the full spectrum of 500–1000 nm, which had the unique characteristics of a continuous spectrum in the visible and near infrared (VNIR) regions with 10 nm spectral resolution. Yellow and green leaves from four plants (aloe, dracaena, balata, and radermachera) were measured using the AOTF-HSL to assess its feasibility in agriculture application. The spectral profiles measured by a standard spectrometer (SVC© HR-1024) were used as a reference for evaluating the measurements of the AOTF-HSL. The difference between the spectral measurements collected from active and passive instruments was minor. The comparison results show that the AOTF-based consecutive and high spectral resolution HSL was effective for this application.

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Zhao, Huijie, Zefu Xu, Hongzhi Jiang, and Guorui Jia. "SWIR AOTF Imaging Spectrometer Based on Single-pixel Imaging." Sensors 19, no. 2 (January 18, 2019): 390. http://dx.doi.org/10.3390/s19020390.

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An acousto-optic tunable filter (AOTF) is a new type of mono-wavelength generator, and an AOTF imaging spectrometer can obtain spectral images of interest. However, due to the limitation of AOTF aperture and acceptance angle, the light passing through the AOTF imaging spectrometer is weak, especially in the short-wave infrared (SWIR) region. In weak light conditions, the noise of a non-deep cooling mercury cadmium telluride (MCT) detector is high compared to the camera response. Thus, effective spectral images cannot be obtained. In this study, the single-pixel imaging (SPI) technique was applied to the AOTF imaging spectrometer, which can obtain spectral images due to the short-focus lens that collects light into a small area. In our experiment, we proved that the irradiance of a short-focus system is much higher than that of a long-focus system in relation to the AOTF imaging spectrometer. Then, an SPI experimental setup was built to obtain spectral images in which traditional systems cannot obtain. This work provides an efficient way to detect spectral images from 1000 to 2200 nm.

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Jackel, J. L., M. S. Goodman, J. E. Baran, W. J. Tomlinson, G. K. Chang, M. Z. Iqbal, G. H. Song, et al. "Acousto-optic tunable filters (AOTFs) for multiwavelength optical cross-connects: crosstalk considerations." Journal of Lightwave Technology 14, no. 6 (June 1996): 1056–66. http://dx.doi.org/10.1109/50.511607.

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Volz, Pierre, Robert Brodwolf, Christian Zoschke, Rainer Haag, Monika Schäfer-Korting, and Ulrike Alexiev. "White-Light Supercontinuum Laser-Based Multiple Wavelength Excitation for TCSPC-FLIM of Cutaneous Nanocarrier Uptake." Zeitschrift für Physikalische Chemie 232, no. 5-6 (May 24, 2018): 671–88. http://dx.doi.org/10.1515/zpch-2017-1050.

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AbstractWe report here on a custom-built time-correlated single photon-counting (TCSPC)-based fluorescence lifetime imaging microscopy (FLIM) setup with a continuously tunable white-light supercontinuum laser combined with acousto-optical tunable filters (AOTF) as an excitation source for simultaneous excitation of multiple spectrally separated fluorophores. We characterized the wavelength dependence of the white-light supercontinuum laser pulse properties and demonstrated the performance of the FLIM setup, aiming to show the experimental setup in depth together with a biomedical application. We herein summarize the physical-technical parameters as well as our approach to map the skin uptake of nanocarriers using FLIM with a resolution compared to spectroscopy. As an example, we focus on the penetration study of indocarbocyanine-labeled dendritic core-multishell nanocarriers (CMS-ICC) into reconstructed human epidermis. Unique fluorescence lifetime signatures of indocarbocyanine-labeled nanocarriers indicate nanocarrier-tissue interactions within reconstructed human epidermis, bringing FLIM close to spectroscopic analysis.

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Morris, Hannah R., Clifford C. Hoyt, and Patrick J. Treado. "Imaging Spectrometers for Fluorescence and Raman Microscopy: Acousto-Optic and Liquid Crystal Tunable Filters." Applied Spectroscopy 48, no. 7 (July 1994): 857–66. http://dx.doi.org/10.1366/0003702944029820.

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Acousto-optic tunable filters (AOTF) and liquid crystal tunable filters (LCTF) are evaluated for their suitability as fluorescence microscopy imaging spectrometers. AOTFs are solid-state birefringent crystals that provide an electronically tunable spectral notch passband in response to an applied acoustic field. LCTFs also provide a notch passband that can be controlled by incorporating liquid crystal waveplate retarders within a Lyot birefringent filter. In this paper, spectroscopic performance and imaging quality are contrasted by evaluation of model systems. Studies include transmission imaging of standard resolution targets, multispectral fluorescence emission imaging of tagged polystyrene microspheres, and immunofluorescence imaging of neurotransmitters within rat-brainstem thin sections. In addition, the first use of LCTFs for Raman microscopy is demonstrated. Raman microscopy is a noninvasive spectral imaging technique that can provide chemically significant image contrast complementary to fluorescence microscopy without the use of stains or tags.

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Zhang Rui, 张. 瑞., 解琨阳 Xie Kunyang, 景. 宁. Jing Ning, 王志斌 Wang Zhibin, 陈媛媛 Chen Yuanyuan, 李克武 Li Kewu, and 乔. 亚. Qiao Ya. "Technology of hyperspectral full polarization imaging based on superachromatic 1/4 wave plate and acousto-optic tunable filter." Infrared and Laser Engineering 48, no. 8 (2019): 814004. http://dx.doi.org/10.3788/irla201948.0814004.

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Chu, Raymond R., and Wilson T. C. Wong. "Miniaturized external cavity laser (ECL) implemented with acoustic optical tunable filter." Journal of the Acoustical Society of America 119, no. 2 (2006): 682. http://dx.doi.org/10.1121/1.2174407.

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Amarasinghe, Priyanthi M., Joo-Soo Kim, Sudhir Trivedi, Feng Jin, Jolanta Soos, Mark Diestler, Syed B. Qadri, Janet l. Jensen, James Jensen, and Neelam Gupta. "Mercurous Bromide (Hg2Br2) Acousto-Optic Tunable Filters (AOTFs) for the Long Wavelength Infrared (LWIR) Region." Journal of Electronic Materials 50, no. 10 (July 27, 2021): 5774–79. http://dx.doi.org/10.1007/s11664-021-09127-9.

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Chu, Raymond R., and Qing Jiang. "Miniature, narrow band, non-collinear acoustic optical tunable filter for telecom applications." Journal of the Acoustical Society of America 117, no. 5 (2005): 2683. http://dx.doi.org/10.1121/1.1932321.

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Dias Ribeiro, Lívia Paulia, Mariana Guilherme Pereira, Jarbas José Rodrigues Rohwedder, and Celio Pasquini. "Development and preliminary evaluation of a spectrophotopolarimeter based on acoustic-optical tunable filter." Measurement Science and Technology 24, no. 6 (May 14, 2013): 065902. http://dx.doi.org/10.1088/0957-0233/24/6/065902.

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Park, Hyun Chul, and Kwang Jo Lee. "Twisted optical-fiber-based acousto-optic tunable filter controlled by the flexural acoustic polarization." Journal of the Korean Physical Society 67, no. 3 (August 2015): 472–85. http://dx.doi.org/10.3938/jkps.67.472.

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Lee, Kwang Jo, In-Kag Hwang, Hyun Chul Park, and Byoung Yoon Kim. "Polarization-Independent All-Fiber Acousto-Optic Tunable Filter Using Torsional Acoustic Wave." IEEE Photonics Technology Letters 22, no. 8 (April 2010): 523–25. http://dx.doi.org/10.1109/lpt.2010.2041920.

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Shao, Hui, Yuwei Chen, Wei Li, Changhui Jiang, Haohao Wu, Jie Chen, Banglong Pan, and Juha Hyyppä. "An Investigation of Spectral Band Selection for Hyperspectral LiDAR Technique." Electronics 9, no. 1 (January 13, 2020): 148. http://dx.doi.org/10.3390/electronics9010148.

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Hyperspectral LiDAR (HSL) has been widely discussed in recent years, which attracts increasing attention of the researchers in the field of electronic information technology. With the application of supercontinuum laser source, it is now possible to develop an HSL system, which can collect spectral and spatial information of targets simultaneously. Meanwhile, eye-safety and miniature HSL device with multiple spectral bands are given more priorities in on-site applications. In this paper, we tempt to investigate how to select spectral bands with a selection method. The proposed method consists of three steps: first, the variances among the classes based on hyperspectral feature parameters, termed inter-class variances, are calculated; second, the channels are sorted based on corresponding variances in descending order, and those with the two highest values are adopted as the initial input of classification; finally, the channels are selected successively from the rest of the sorted sequence until the classification accuracy reaches 100%. To test the performance of the proposed method, we collect 91/71-channel hyperspectral measurements of four different categories of materials with 5 nm spectral resolution using an acousto-optic tunable filter (AOTF) based HSL. Experimental results demonstrate that the proposed method could achieve higher classification accuracy than a random band selection method with different classifiers (naïve Bayes (NB) and support vector machine (SVM)) regardless of classification feature parameters (echo maximum and reflectance). To reach 100% accuracy, it demands 8–9 channels on average by echo maximum and 4–5 channels on average by reflectance based on NB classifier; these figures are 3–4 by echo maximum and 2–3 by reflectance with SVM classifier. The proposed method can complete classification task much faster than the random selection method. We further confirm the specific channels for the classification of different materials, and find that the optimal channels vary with different materials. The experimental results prove that the optimal band selection of HSL system for classification is reliable.

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Zhang, Hao, Bo Liu, Wei Lin, Hongguang Dong, and Lihui Liu. "Acoustic dispersion measurement for a single-mode-fiber-based acoustooptic tunable filter excited by flexural acoustic wave." Microwave and Optical Technology Letters 54, no. 5 (March 13, 2012): 1281–85. http://dx.doi.org/10.1002/mop.26790.

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Zaitsev, Alexei K., and Viktor V. Kludzin. "Subcollinear acousto-optic tunable filter based on the medium with a strong acoustic anisotropy." Optics Communications 219, no. 1-6 (April 2003): 277–83. http://dx.doi.org/10.1016/s0030-4018(03)01293-8.

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Zhang, Hao, Minghui Qiu, Shouxin Kang, Bo Liu, and Yinping Miao. "A tunable interferometric optical bandpass filter based on flexural acoustic wave modulation in a SMF-MOF hybrid configuration with fiber offset splicing output." Microwave and Optical Technology Letters 57, no. 1 (November 18, 2014): 31–35. http://dx.doi.org/10.1002/mop.28765.

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Binh, Le Nguyen. "Acousto-optic tunable wavelength and selective packet filter by simultaneously launching of acousto-optic waves of different frequency for TE–TM mode conversion in diffused optical and acoustic waveguides." Optical Engineering 48, no. 5 (May 1, 2009): 054603. http://dx.doi.org/10.1117/1.3138775.

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Vanhamel, Jurgen, Emmanuel Dekemper, Sophie Berkenbosch, and Roland Clairquin. "Novel acousto-optical tunable filter (AOTF) based spectropolarimeter for the characterization of auroral emission." Instrumentation Science & Technology, September 2, 2020, 1–13. http://dx.doi.org/10.1080/10739149.2020.1814809.

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Silva, M. G. da, C. S. Sobrinho, R. S. de Oliveira, and A. S. B. Sombra. "Analysis of Ultrashort Pulse Switching in an Acousto-optic Tunable Filter (AOTF) with Loss." Journal of Optical Communications 22, no. 6 (January 1, 2001). http://dx.doi.org/10.1515/joc.2001.22.6.228.

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