Laser induced damage studies in mercury cadmium telluride

We have investigated laser induced damage at laser wavelength in diamond paste polished (mirror finish) and carborundum polished Hg_0.8Cd_0.2Te (MCT) samples with increasing fluence as well as number of pulses. Evolution of damage morphology in two types of samples is quite different. In case of diamond paste polished samples, evolution of damage morphological features is consistent with Hg evaporation with transport of Cd/Te globules towards the periphery of the molten region. Cd/Te globules get accumulated with successive laser pulses at the periphery indicating an accumulation effect. Real time reflectivity (RTR) measurement has been done to understand melt pool dynamics. RTR measurements along with the thermal profile of the melt pool are in good agreement with thermal melting model of laser irradiated MCT samples. In case of carborundum polished samples, laser damage threshold is significantly reduced. Damage morphological features are significantly influenced by surface microstructural condition. From comparison of the morphological features in the two cases, it can be inferred that laser processing of MCT for device applications depends significantly on surface preparation conditions.