The prototype of He-Ne / He-Xe laser system for methane detection using differential absorption of radiation backscattered from topographic targets is described. Using radiation of the wavelengths 3.39 μm and 3.51 μm, the measurement of CH4 at the distance of 50 m was carried out. To increase the range and accuracy of measurement, the Cassegrain optics and lasers of higher power can be used. The lasers have four-channel construction structure and they are excited with RF current.
The prototype of the dual He-Ne/He-Xe laser system for gas detection using differential absorption of radiation backscattered from topographic targets is described. Both lasers were excited by dc discharge and for lengths of 80 cm we obtained the output power of about 10 mW. Using receiver optics with the diameter of 7 cm and thermocooled HgCdTe detector we can measure the presence of methane on the distance up to 50 m. The new solution is under construction. to increase the range of measurement, the Casseigrain optics with diameter of 25 cm is being prepared. Using the special construction of RF excited gas lasers with the output power of 40 mW, the measurement distance of 100 m is expected.
A new laser Doppler velocimeter employing a CO2 laser has been developed by using its photoacoustic effect. A change of the pressure of a laser discharge tube, induced by mixing of a returned wave with an originally existing wave inside the cavity, is employed to detect the Doppler frequency shift. We found that a Doppler frequency shift as much as 60 kHz was detected, and as well as a good linear relationship between the velocity and the Doppler frequency shift was obtained.
Four-channel structures in form of the second rank 2x2 matrix were investigated. For CO2 lasers we applied phase-locking techniques. He-Ne and He-Xe lasers were built as independent four-channels and optimized for their output power.
The paper describes the design, development and examination of a prototype dual He-Ne IHe-Xe laser system for gas detection using differential absorption of radiation backscattered from topographic targets. Both lasers were excited by RF discharge. For lengths of 50 cm we obtained the output power of about 10 mW. Using receiver optics with the diameter of 7 cm and thermocooled HgCdTe detector the presence of methane on the distance up to 50m. can be measured. The new solution is under construction. To increase the range of measurement Casseigrain optics with diameter of 30 cm is being prepared. Using the special construction of gas lasers with the output power of 30 mW, the measurement distance of 200 m is expected.
Two methods of frequency stabilization of RF excited CO2 lasers are presented. First of them is based on reference absorption peak in deuterized ammonia (NH2D) and assures high resulting short-term stability of laser. The second, simple and cheap method is based on optogalvanic effect in RF plasma.
This paper presents the theoretical and practical solutions of infrared, heterodyne detection systems applied in the pollution monitoring, methane detection, industry as well as laser spectroscopy. The utilization of stabilized laser diodes, coherent pumped solid state lasers as well as CO2 lasers with conversion of generation frequency covers the broad band of infrared region especially interesting for detection of different atmosphere pollutants or gas contaminants. Low cost heterodyne vibrometers, velocimeters or rangefinders can find wide industrial or metrological applications.
The new trends in the construction of advanced versions of carbon-dioxide lasers, based on unconventional shapes of discharge regions as well as special designs of laser resonators promise the construction of compact, efficient infrared laser sources with unitary power much higher than for conventional carbon-dioxide lasers. The paper present the idea of synchronization of output beams in the 'two-slab,' waveguide carbon-dioxide laser, doubling the output power of efficient 'monoslab' laser, but preserving the output beam quality.
The paper presents the parameters and the results of investigations of basic subassemblies of heterodyne detection systems of scattered radiation. Work on heterodyne radiation of infrared radiation, conducted in MUT from 1983, allowed us to develop several measurement systems, based on fundamental subassemblies developed in Poland. The sources of radiation are sealed-off carbon-dioxide lasers, frequency transformation is accomplished by means of acousto-optic modulators, the compression of pulses in dispersive lines, based on surface acoustic waves (SAW) is the heart of the detection systems.
KEYWORDS: Doppler effect, Sensors, Carbon dioxide lasers, Laser systems engineering, Heterodyning, Signal detection, Oscillators, Optoelectronics, Telescopes, Signal to noise ratio
The paper presents two carbon-dioxide laboratory laser systems that were designed for a large number of heterodyne detection experiments, as small signal detection, target range, and velocity measurements, Doppler shift examination, frequency difference measurement, etc. These systems were performed in cooperation with the Institute of Quantum Electronics from the Military University of Technology, Poland.
The detection of infrared radiation gathers greater and greater interest with the extension of its practical applications and improvement of the infrared detector performance and their price reduction. In particular it relates to middle infrared region (8 - 12 micrometers ), where powerful CO2 lasers as well as heterodyne detection of radiation can be utilized. The paper presents the development of direct detection and heterodyne detection systems as well as selected results of investigations of subassemblies and devices. The most interesting results are connected with the application of `multispectral' infrared detectors, reflective a-o modulator integrated with polarizer and Dember effect detectors.
The paper presents the construction and results of investigations of a new waveguide CO2 laser in which the synchronization of beams arising from four independent waveguide channels was realized. Thanks to that, the unitary output power of more than 1 W/cm of length, a value which is greater than that in conventional, sealed-off CO2 lasers, has been obtained. The development of transverse, rf discharge, has increased the efficiency and reliability of the laser head and has decreased the power supply dimensions.
This paper presents the description and verification of subassemblies as well as the evaluation of basic parameters of a heterodyne detection system performed in cooperation with the Institute of Quantum Electronics, Military University of Technology, Warsaw, Poland.
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