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Thermal cross-talk reduction in IR thermo-electric photodetectors by lock-in method: 4D numerical simulations and experimental verification Host Publication: Finds and Results from the Swedish Cyprus Expedition: A Gender Perspective at the Medelhavsmuseet Authors: W. Vandermeiren, J. Stiens, C. De Tandt, G. Shkerdin, V. Kotov, G. Borghs, P. Muys and R. Vounckx Publisher: SPIE Publication Date: Mar. 2010 Number of Pages: 9 ISBN: 978-0-8194-7993-8
Abstract: Laser induced temperature distributions inside doped semiconductor materials are used to derive laser beam profiles by means of the thermo-electric Seebeck effect. Thermal diffusion will lead to a discrepancy between the optical intensity profile of the laser beam and the measured temperature distribution inside the semiconductor. An advanced numerical 4D finite element model describing the laser induced spatial temperature distribution in function of time in a layered GaAs based structure was developed in Comsol Multiphysics. Non-linearities as the temperature dependence of the absorption coefficient, the thermal conductivity and the Seebeck coefficient were taken into account. This model was used to investigate the optical chopper frequency dependence on the spatial thermal cross-talk level and the responsivity near the illuminated surface of the detector structure. It was shown that the frequency dependent cross-talk level can be reduced significantly by applying short chopping periods due to the dependence of the thermal diffusion length on the frequency. The thermal cross-talk is reduced to ᆩ dB and ᆺ.6 dB for the first and second neighboring pixel respectively for a lock-in frequency of 140 Hz. Experimental results of the spatial thermal cross-talk level and the responsivity were compared with simulations and satisfactory agreements between both were achieved. High power CO2 laser profile measurements obtained with our thermo-electric detector and a commercially available Primes detector were compared.
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