Acoustooptic power spectrum analyser experimental researches have been made in' demonstrate ,that it's stable function heavy depends from thennal stabilisation as light source, so Brag cell one. Possible way for rough estimation thermal drift ixifluense upon the resolution of spectrum analyser and it's temporal stable is under consideration bellow.
INTRODUCTIONObservations have been made upon spectrum analyser with semiconductor laser behaviour , demonstrate, that stochastic thermal and current fluctuations oflaser's frequency radiation are appeared in accidental drift and jumps of detected light distribution across photodetector's array (in the average that jumps occur about one till three times per minute). If there are used photodetector arrays with time integration, than these effects bring out decreasing of spectrum analyser's resolution during some time. In addition one should permanently check frequencies channels correspondence to the fixed photodetectors of array to calibrate analyser. Other critical factor of analyser function is thermal deviation of Brag cell's chip. Observations demonstrate, that temperature increasing above one degree offers to spectrum analyser frequency shift upon about 1 MHz. This effect was widely investigated in literature. But there were not paid a lot of attention to the considerations of "thin temporal structure" of stochastic thermal fluctuations offers in slow temporal deformations and floating of analyser's frequencies net. But to design spectrum analysers with high resolution and exact frequencies estimation possibilities one should take into account to pointed above effects.An aim of this report is to propose the ways of numerical estimations for spectrum analyser stability, that can be applied for it's design.
Spectral interference resulting from the tendency of infrared windows to act as low-finesse etalons is evaluated for various infrared materials. The effect's temperature dependence and implications to CO 2 concentration measurements is demonstrated by modelling the etalon's influence on the CO 2 ν 3 absorption band. It is shown that semiconductor and zinc chalcogenide windows exhibit a very strong temperature sensitivity, with lower refractive index windows, such as fluorides, having a lesser but still significant sensitivity which can lead to spurious results. Elimination of any spectral distortion or changes in concentration due to etalon effects requires the windows to be wedged with a minimum angle of approximately 1.0-0.7 mrad depending on the window material.
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