Acousto-optical Spectrometer Research Articles

Selection and Justification of Optimal Spectral Wavelengths for Control of Methane Emission from an Advanced Nanosatellite

The choice and justification of optimal wavelengths of spectral radiance density registration for the task of monitoring methane emissions in the atmosphere from the orbit of an artificial satellite by a passive optical sensor in the spectral region near 1.65 μm have been performed. Mathematical modelling of the spectra recorded by the optical sensor for tropical and subarctic atmospheric models of the Earth’s atmosphere, different widths of the spectral function of the acousto-optic spectrometer, and different solar zenith angle were performed. It is assumed that methane emissions in the Earth’s atmosphere will be monitored from a promising nanosatellite (weighing less than 6 kg) using an acousto-optic spectrometer, which uses two narrow (0.1 nm and 0.5 nm) wavelengths of radiation registration to implement a differential method of absorption spectroscopy based on acousto-optic filtering. A criterion for selecting optimal wavelengths for monitoring the integral methane content in the atmosphere from the orbit of the artificial satellite is proposed. The values of the central wavelengths of optimal wavelengths for recording the energy brightness of scattered radiation for the width of the spectral function of the acousto-optic spectrometer in range (0.0, 0.1, 0.2 and 0.5) nm have been obtained. It is shown that the choice of the optimal pair of wavelengths is determined by the width of the spectral function of the sensor, depends insignificantly on the model of the Earth’s atmosphere (tropical or subarctic model) and does not depend on the solar zenith angle in range (0–80) angular degree.

Использование модуляционной акустооптической спектрометрии для определения местоположения спектральных особенностей в перекрывающихся спектрах

The spectrometer is not able to accurately determine the spectral position of the smaller maximum if it is located against the background of a powerful broad peak. The solution of the problem is known it is enough to differentiate the existing dependence, and the position of the smaller peak is determined with sufficient accuracy. Based on a quasi-collinear acousto-optic (AO) cell, a prototype spectrometer was created, which makes it possible to record both the spectrum of the optical signal and its derivative in real time. In the course of the work, a more detailed research of the work of the created model was carried out: the value of the phase shift was changed programmatically from zero to 360°, and the spatial modulation period - from zero to the length of the AO cell L. A neon lamp and all the data presented were used as a radiation source, were obtained for the same emission line. The maximum signal for the derivative corresponds to the phase values of 90° and 270°. In another series of experiments, the work of the model was investigated with a change in the modulation period (the phase shift is fixed, ψ=π/2). The maximum signal for the derivative corresponds to the values of the modulation period duration equal to L/2, half the length of the acousto-optic cell. The graphs of the results of "physical" and "mathematical" differentiation do not coincide. We assume that the differences are related to the shape of the instrumental function of the acousto-optical spectrometer. However, at the tops of the spectral peaks, in the regions of intersection of derivatives with a zero line, the results coincide, which makes it possible to use acousto-optic differentiation to reveal the "fine structure" of optical spectra, and in real time. Thus, as a result of the work carried out: a method was proposed for the precise determination of the position of spectral maxima in complex overlapping spectra in real time; an instrumental implementation of the proposed method was created, and it was shown that for the visible range (532 nm) the accuracy of determining the spectral position of the maxima is 0.2 nm.

Minimizing aberrations of a near-infrared acousto-optic video spectrometer by optimizing the tunable filter parameters

Minimization of the aberration distortions of a near-infrared image spectrometer is addressed in this study. A model of an acousto-optical video spectrometer has been developed that provides a fairly high quality of spectral images over the 0.9–1.7 µm range. Aberration distortions are minimized through ZEMAX software, using a semi-automated (interactive) procedure to optimize the geometric parameters of an acousto-optic paratellurite cell with the selected parameters of other optical elements of the system. The prototype developed here is characterized by the absence of distortion and lateral chromatic aberration, with diffraction-limited spatial resolution of 30 µm in the image plane within the entire field of view. The resulting spectral images confirm the calculation and simulation results.

Electronic Amplifier for Modern Acousto-Optical Spectrometers

The paper presents an analysis of electronic amplifiers for modern acousto-optical spectrometers, based on two-crystal sequential diffraction of incident radiation by acoustic waves propagating in each acousto-optical (AO) cell. Such a diffraction scheme has a higher spectral resolution, retaining all the other advantages of traditional AO spectrometers. A description of the functional block diagram of a two-crystal AO spectrometer is given, and the necessary requirements for electronic units are indicated. The results of joint use of the signal power amplification device and a previously developed wideband frequency synthesizer for exciting sound waves in AO cells are presented; output amplitudes of amplified signals are obtained.

Minimization of near-infrared acousto-optic video spectrometer aberrations by optimizing tunable filter parameters

Minimization of near-infrared acousto-optic video spectrometer aberrations by optimizing tunable filter parameters

An imaging spectroradiometry system for measuring spatial temperature distributions in microscopic objects

An imaging-spectrometry method for measuring the spatial distributions of the temperature of microscopic objects with nonuniform spectral-emissivity distributions over their surfaces is described. An acousto-optic imaging spectrometer that allows measurements of the temperature distributions in the range of 500–5000 K with an error of ~1% and a spatial resolution of 500 × 500 elements over the surfaces of objects with dimensions of at most 5 mm was developed and manufactured. The efficiency of the instrument was demonstrated experimentally in measurements of the spatial distribution of the temperature of a laserheated tungsten plate.

Wideband spectrum analysis of ultra-high frequency radio-wave signals due to advanced one-phonon non-collinear anomalous light scattering.

We present a principally new acousto-optical cell providing an advanced wideband spectrum analysis of ultra-high frequency radio-wave signals. For the first time, we apply a recently developed approach with the tilt angle to a one-phonon non-collinear anomalous light scattering. In contrast to earlier cases, now one can exploit a regime with the fixed optical wavelength for processing a great number of acoustic frequencies simultaneously in the linear regime. The chosen rutile-crystal combines a moderate acoustic velocity with low acoustic attenuation and allows us wide-band data processing within GHz-frequency acoustic waves. We have created and experimentally tested a 6-cm aperture rutile-made acousto-optical cell providing the central frequency 2.0 GHz, frequency bandwidth ∼0.52 GHz with the frequency resolution about 68.3 kHz, and ∼7620 resolvable spots. A similar cell permits designing an advanced ultra-high-frequency arm within a recently developed multi-band radio-wave acousto-optical spectrometer for astrophysical studies. This spectrometer is intended to operate with a few parallel optical arms for processing the multi-frequency data flows within astrophysical observations. Keeping all the instrument's advantages of the previous schematic arrangement, now one can create the highest-frequency arm using the developed rutile-based acousto-optical cell. It permits optimizing the performances inherent in that arm via regulation of both the central frequency and the frequency bandwidth for spectrum analysis.

Spatial and spectral calibration of an acousto-optical spectrometer

The problem of determining the optical spectra at separate points of images that are recorded with an endoscopic acousto-optical spectrometer is considered. The factors that cause distortions in images and spectra are investigated. Algorithms for calibration of this type of instruments and digital data correction for the sequential elimination of distortions of various types are developed. In a model experiment, it is shown that the proposed algorithm provides a quite high quality of determining spectra at arbitrary points of the field of vision.

Effect of feedback loop on the resolution of acousto-optic spectrometer

An acousto-optic spectrometer based on a collinear acousto-optic cell with feedback loop has been theoretically and experimentally investigated. It is shown that the introduction of optoelectronic feedback affects to a great extent the characteristics of collinear acousto-optic interaction and makes it possible to increase significantly the accuracy of determining the wavelength of incident optical signal.

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

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

Spectrometers Based on Acousto-Optical Filters

A family of acousto-optical spectrometers for different applications is presented. The spectrometers are classified by type, characteristics, and function. Features in the design and application of these spectrometers and measurement systems based on the spectrometers are discussed.

Методы обработки и анализа спектров, регистрируемых акустооптическими спектрометрами

Методы обработки и анализа спектров, регистрируемых акустооптическими спектрометрами

АКУСТООПТИЧЕСКИЕ АНАЛИЗАТОРЫ СПЕКТРАЛЬНОГО СОСТАВА ИЗЛУЧЕНИЯ ОПТИЧЕСКОГО И РАДИОТЕХНИЧЕСКОГО ДИАПАЗОНОВ НА ОСНОВЕ БРЭГГОВСКИХ РЕЗОНАНСОВ ВЫСШИХ ПОРЯДКОВ

The results of studies of characteristics of acousto-optics spectrum analyzers of radiation in the optical and radio ranges based on the use of Bragg resonances of the first and second orders are showed. The characteristics of acoustooptics devices using the first and second diffraction orders are showed to depend differently on the parameters of acoustooptics interaction because the selection of optical and radio signals is based on different principles of acousto-optics interaction. Key words: acousto-optics , spectral analysis of optical and radio signals Manuscript submitted 10.02.2014 Radio phys. radio astron. 2014, 19(2): 186-192 REFERENCES 1. GOLOSOVSKY, O. A. and RAZDOBUDKO, V. V., 2011. Acoustooptic spectro-analyzers: current state and prospects. Progresses of modern radio electronics. no. 12, pp. 43–56 (in Russian). 2. SIEBERTZ, O., SCHIEDER, R., GAL, C., OLBRICH, M., and HARTOGH, P. Acousto-optical spectrometers for THz heterodyne instruments [online] Available from: http://researchgate.net/publication/237754888_Acoustooptical_spectrometer_for_THz_heterodyne_instruments 3. HILLMAN, J. J., CLENAR,D. A., KUEHN, D. M., CHANOVER, N. J.,and BLASS, W. E. Compact Imaging Spectrometers using Acousto-Optic Tunable Filters [online] Available from: http://www.stsci.edu/stsci/meetings/space_detectors/pdf/hillman.pdf 4. ZILBERMAN , G. Ye., SIDOROV, I. N., KUPCHENKO, L. F., 1982. To the theory of light diffraction by ultrasound. Radio engineering and electronics . vol. 27, no. 2, pp. 241–247 (in Russian). 5. KUPCHENKO, L. F., PLAKHOV, Y. M., EFIMOVA, O. V., LOBYREV, V. B., CHERKASHINA, E. L., SHEVCHENKO , A. V., 1999. Diffraction Efficiency of Second Order Bragg Diffraction at Interaction of Light with Ultrasound under Double Bragg's Angle. Radio Phys. Radio Astron . vol.4, no. 4, pp. 342-348 (in Russian).

Chang’E-3 scientific payloads and its checkout results

The scientific objectives of ChangE-3 mission were to: examine the texture, mineralogy, and structure of the local lunar terrain; determine the distribution and composition of minerals, rocks, and soils surrounding the landing sites; image the Earths plasmasphere and operate an ultraviolet astronomy camera on the moon. Four kinds of scientific instruments are chosen as the payloads for ChangE-3 lander, which include topography camera, lunar optical telescope, extreme ultraviolet imager and landing camera so on. And other four kinds of scientific instruments are chosen as the payloads for lunar rover, which include panoramic cameras, lunar radar, IR acousto-optic spectrometer, X-ray spectrometer and so on. This paper mainly introduces scientific exploration mission, the scientific payloads design and construction. The checkout results are also described in detail.

Developing an Advanced Prototype of the Acousto-Optical Radio-Wave Spectrometer for Studying Star Formation in the Milky Way

The designed practically prototype of an advanced acousto-optical radio-wave spectrometer is presented in a view of its application to investigating the Milky Way star formation problems. The potential areas for observations of the cold interstellar medium, wherein such a spectrometer can be exploited successfully at different approximations, are: 1) comparison of the Milky Way case with extragalactic ones at scale of the complete galactic disk; 2) global studies of the Galactic spiral arms; and 3) characterization of specific regions like molecular clouds or star clusters. These aspects allow us to suggest that similar instrument will be really useful. The developed prototype of spectrometer is able to realize multi-channel wideband parallel spectrum analysis of very-high-frequency radio-wave signals with an improved resolution power exceeding 103. It includes the 1D-acousto-optic wide-aperture cell as the input device for real-time scale data processing. Here, the current state of developing this acousto-optical spectrometer in frames of the astrophysical instrumentation is briefly discussed, and the data obtained experimentally with a tellurium dioxide crystalline acousto-optical cell are presented. Then, we describe a new technique for more precise spectrum analysis within an algorithm of the collinear wave heterodyning. It implies a two-stage integrated processing, namely, the wave heterodyning of a signal in an acoustically square-law nonlinear medium and then the optical processing in the same solid-state cell. Technical advantage of this approach lies in providing a direct multi-channel parallel processing of ultra-high-frequency radio-wave signals with the resolution power exceeding 104. This algorithm can be realized on a basis of exploiting a large-aperture effective acousto-optical cell, which operates in the Bragg regime and performs the ultra-high-frequency co-directional collinear acoustic wave heterodyning. The general concept and basic conclusions here are confirmed by proof-of-principle experiments with the specially designed cell of a new type based on a lead molybdate crystal.

Алгоритм измерения гладких спектров с помощью акустооптических спектрометров

Алгоритм измерения гладких спектров с помощью акустооптических спектрометров

Acousto-optic video spectrometer module for medical endoscopic studies

This paper describes a prototype of an acousto-optic video spectrometer module that can be linked with rigid lens-type and flexible optical-fiber medical endoscopes. Examples are given of the resulting spectral images, demonstrating the main quality of the developed layout—minimization of spatiospectral distortions. This allows the device to be used in problems of photoluminescence diagnosis in medical applications to rapidly obtain both spectral images and undistorted complete spectra of any point of an image of an internal organ. The possibilities and prospects of this approach are analyzed.

In-Orbit Measurement of the AOS (Acousto-Optical Spectrometer) Response Using Frequency Comb Signals

The in-orbit response characteristic of the AOS (Acousto-Optical Spectrometer) was estimated from spectral profiles taken by using a frequency comb generator, which was originally used for frequency axis calibration. Frequency comb signals taken under various environmental conditions in orbit were consolidated to deduce the response profile of the spectrometer. The fluctuation bandwidth calculated from the deduced spectral response compared well with that derived from the noise characteristic of the spectrometer.

Glow discharge imaging spectroscopy with a novel acousto-optical imaging spectrometer

A novel Acousto-Optical imaging Spectrometer (AOS) was developed with unique features that make it attractive for different applications and fundamental investigations in atomic spectroscopy. Spatial resolution of the AOS is approximately 125 μm. Spectral resolution varies from 0.05 nm to 0.3 nm (full width at half maximum, FWHM) between 250 nm and 800 nm, respectively. Time resolution is 5 ns. Thus, the constructed AOS provides enough spatial, spectral and time resolution for applications in glow discharge imaging spectroscopy. Fast switching between different spectral lines within 200 μs can be used e.g. to investigate the evolution of different spectral lines quasi-simultaneously.

TheHerschel-Heterodyne Instrument for the Far-Infrared (HIFI)

Aims. This paper describes the Heterodyne Instrument for the Far-Infrared (HIFI) that was launched onboard ESA's Herschel Space Observatory in May 2009. Methods. The instrument is a set of 7 heterodyne receivers that are electronically tuneable, covering 480-1250 GHz with SIS mixers and the 1410-1910 GHz range with hot electron bolometer (HEB) mixers. The local oscillator (LO) subsystem comprises a Ka-band synthesizer followed by 14 chains of frequency multipliers and 2 chains for each frequency band. A pair of auto-correlators and a pair of acousto-optical spectrometers process the two IF signals from the dual-polarization, single-pixel front-ends to provide instantaneous frequency coverage of 2 × 4 GHz, with a set of resolutions (125 kHz to 1 MHz) that are better than 0.1 km s-1. Results. After a successful qualification and a pre-launch TB/TV test program, the flight instrument is now in-orbit and completed successfully the commissioning and performance verification phase. The in-orbit performance of the receivers matches the pre-launch sensitivities. We also report on the in-orbit performance of the receivers and some first results of HIFI's operations.