An improved TeO2 and Te infrared acoustooptic tuneable spectrometer has been analysed, using infrared fibres, a high speed frequency synthesiser and optimised algorithms. A comparison is made with the next best AOTF infrared materials, Tl3AsSe3, HgCl2 and PbBr2. A design study of the TeO2 and Te AO imaging spectrometer is also presented, operating in the two thermal bands, 1-5micrometers and 6-12micrometers , using an interchangeable fore-optics and a multiplexed electronically scanned infrared array cooled at 77 degrees K. Some initial experimental results indicate that these systems can perform well, an increase in the dynamic range in the 8-12 micrometers and is obtained compared to the 3-5*m band. It can be very useful in chemical process control, medical diagnostics, aerospace and earth remote sensing. Based on recent imaging spectrometer development, a design study of the TeO2 AO imaging spectrometer in the 0.4-1 micrometers band, for simultaneous spectroscopy at every pixel, is presented, using a CCD camera and fast data processing technology.
Two kinds of practical efficient acoustooptically phase-matched noncollinear second harmonic generation (SHG) interactions are predicted in Tellurium for the incident optical wave at 10.6µm .They are produced by two anisotropic acoustooptic. (AO)interactions in which the normal to the AO interaction plane is offset of 10° with respect to the optical (Z)a.xis . For X-propagating slow shear acoustic wave, a high AO figure of merit is predicted, presenting a low optic absorption in Tellurium. The first SHG wave is interpreted as being due to mixing of the incident optical ave and the acoustooptically scattered wave. The other SHG is observed due to mixing of the two acoustooptically scattered waves. It is shovm from absolute SHG calculations and corresponding SHG measurements previously reported in Te, that the nonlinear optical coefficient which governs these high efficiency SHG interactions is d = 65x10-11m/V . 11 Tbe corresponding SHG efficiencies of these anisotropic diffraction geometries are about x6 and x 5 times respectively larger than the previously reported AO phase-matched noncollinear SHG in Te, for the same input and acoustic power. A comparison is made with the next best ex<2 materials like the cbalcogenide compounds (Tl.3Asse3), proustite (AgGaSe3); Gallium .Arsenic (GaAs) and CdGeAs2.
KEYWORDS: Space telescopes, Telescopes, Point spread functions, Signal to noise ratio, Astronomical telescopes, Optical fiber cables, Image resolution, Photons, Reconstruction algorithms, Hubble Space Telescope
This paper compares and discusses the attempts to overcome the "seeing" resolution limit imposed by spherical aberration for the Hubble Space Telescope and by Atmospheric turbulences f the case of ground -based telescopes - From recently reposed experimental data it is shown that wavefront reconstruction algorithms are capable of restoring nearly fully the Hubble’s spherical aberration of the primary mirror.
Also from previously reported results of ground-based telescopes which utilize the powerful spectral imaging technique at high and low light levels, we compare for different object magnitudes the two types of telescope resolutions "seeing" resolution, SNR and point source resolution.
In this paper an infrared single element two-dimensional acoustooptic processor using a crystal of tellurium will be described, that can process to return echos of each pulse to form the image of the terrain illuminated by the SAR in real-time. This highly compact processor is designed to maintain a range and azimuth resolution of 2 m, will operate with an acoustic bandwith of 200 MHz for an acoustic drive-power of only 1 watt at the optic wavelength of 5 μm and will reach a dynamic range of the order of 40dB determined by the Hg Cd Te CCD array. This processor will control range and azimuth sidelobes below 40 dB, in a minimum detector integration time of 200 ms to resolve a 5 Hz Doppler frequency.
National attention has focused on the critical problem of detecting and avoiding windshear since the crash on August 2, 1985, of a Lockheed L-1011 at Dallas/Fort Worth International Airport. As part of The NASA/FAA National Integrated Windshear Program, we have defined a measurable windshear hazard index that can be remotely sensed from an aircraft, to give the pilot information about the wind conditions he will experience at some later time if he continues along the present flight path. Our technology analysis and end-to-end performance simulation, which measured signal-to-noise ratios and resulting wind velocity errors for competing coherent lidar systems, showed that a Ho:YAG lidar at a wavelength of 2.1 μm and a CO2 lidar at 10.6 m can give the pilot information about the line-of-sight component of a windshear threat in a region extending from his present position to 2 to 4 km in front of the aircraft. This constitutes a warning time of 20 to 40 s, even under conditions of moderately heavy precipitation. Using these results, a Coherent Lidar Airborne Shear Sensor (CLASS), using a Q-switched CO2 laser at 10.6 μm, is being designed and developed for flight evaluation in early 1992. The edge technique is a powerful new method for the measurement of small frequency shifts which allows high accuracy measurement of atmospheric winds (0.2 to 1 m/sec) with high vertical resolution (10 meters) using currently available technology.
Mode concentration and propagation constants in Te thin film structures are readily obtained from a transverse
resonant method without explicit knowledge of the dispersion relationship from Maxwell's equations. Losses involved,
best method of coupling a light beam into a Te thin-film waveguide, non linear Te-X-junctions, bends co and contradirectional
coupling, second order harmonic generation (SHG) in a Te Waveguide structure, are briefly discussed.
Finally the measured optimized detection characteristics of Te/Si thin film device and the proposed theory of the
detection mechanism yield to consider Te thin-films as a potenthlly improved room temperature pulsed C02 laser
detector.
We present here a comparison between the calculated propagation parameters,
the power threshold, the root mean square (RMS) output pulse width and pulse shape
for 10.6 itm laser propagation through hollow circular metallic waveguides and infrared
(IR) optical fibers.
Initially reported experimental results indicate that hollow metallic waveguides
exhibit 1O times smaller loss than optical fibers at 10.6 rn and this is in good agreement
with the calculated results.
On the other hand, compared to common communication fibers at 1.5rn, hollow
waveguides have an attenuation coefficient 10 210L1 larger and therefore are not
suitable for infrared communications.
KEYWORDS: Tellurium, Spectrum analysis, Signal detection, Acousto-optics, Sensors, Crystals, Carbon dioxide lasers, Adaptive optics, Infrared radiation, Signal to noise ratio
The results of a theoretical and simulated study of an infrared two dimensional time integrating
spectrum analyser using a crystal of tellurium with infrared photorecievers time integration are
presented.
Spectrum analysis of the modulated input infrared laser radiation has been carried out with a very
efficient single element two dimensional acoustooptic (2DAO) tellurium deflector. A simulated
multifrequency spectrum analysis of radio signals has been performed. The frequency resolution can be
scaled to cover a few hertz to tens of kilohertz. A minimum detectable input radio signal power at least
two orders of magnitude higher, using Te as well as a wide banwidth can be obtained compared to
other AO spectrum analysers which operate at lower wavelengths and utilize other materials than Te.
Our previously reported experimental data is in good agreement with some of the simulated tests.
Two kinds of efficient acousto-optically phase-matched non collinear optical SHG are predicted in
Te for the incident optical wave at lO,6p in.
The first one is calculated with the shear acoustic wave propagating along the X localized by
the three Euler angles cp=° , 0=1 500, 1600 , 4 450, and is interpreted as being due to mixing of the
incident optical wave and the acousto-optically scattered wave. The other SHG is observed with the
same slow acoustic shear wave and is due to the mixing ot the two acousto-optically scattered optical
waves.
It is shown from absolute SHG calculations and corresponding SF10 measurements previously
reported in Te, that the non linear optical coefficient which governs these high efficiency SHG
interactions is d1 2 = 920 x 10- '2mfV
The corresponding SHG efficiencies are two orders of magnitude larger than the previously
reported phase-matched non-collinear SHG in Te for the same input optic power and acoustic
conditions.
Another highly efficient SHG configuration in Te is discussed as well as the possible application
of these techniques to a parametric oscillator and to a fast infrared two dimensional optical inverter
array.
We present here a comparison between the calculated propagation parameters,
the power threshold, the root mean square (RMS) output pulse width and pulse shape
for 10.6 itm laser propagation through hollow circular metallic waveguides and infrared
(JR) optical fibers.
Initially reported experimental results indicate that hollow metallic waveguides
exhibit 10 times smaller loss than optical fibers at 10.6 sn and this is in good agreement
with the calculated results.
On the other hand, compared to common communication fibers at 1.5m, hollow
waveguides have an attenuation coefficient 10 210Lf larger and therefore are not
suitable for infrared communications.
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