The time-dependent optical reflectivity of HgCdTe detector at 0.63μm has been measured during irradiating by a 1.06-μm Q-switched Nd:YAG laser of 50-ns duration. The reflectivity was observed to increase abruptly to a value and to remain at that value for a period of time, which ranged from several nanoseconds to several hundreds of nanoseconds, depending on the irradiating pulse intensity. The duration of the “flat-top” portion of the reflectivity waveform represents the total time that the surface is melting. Subsequently, the reflectivity dropped abruptly to a value less than the initial one. The difference shows that the damage takes place in the incidence point. By measuring the time-resolved reflectivity and simulating physical structures of PbS and HgCdTe detector, whose dynamic mathematical model was created. By solving the equations of energy transport and thermal diffusion, the temperature rises of PbS and HgCdTe detector irradiated by pulse laser beam were studied, the relationship of power and temperature rises were discussed and the numerical solutions of dynamic temperature field were obtained. The experimental result of the reflectivity of HgCdTe detector was compared with calculated result. The results show finite element analysis is effective in solving the temperature field.
The samples of semiconductor’s surface temperature increased abruptly, when illuminated by laser pulse. The sample’s surface melted and remained liquid phase for a few hundreds ns. That caused reflectivity enhancement of the sample surface. In this article, numerical calculation was carried out on HgCdTe and PbS. And a 1mm-thick HgCdTe was used as the sample in the experiments. In the experiments, the sample was illuminated by laser pulse of 60ns duration from a Q-switched Nd:YAG laser. A beam from He-Ne laser was used as the monitor beam to illustrated the reflectivity changes of the sample. The results of the experiments were the conclusive evidences of our numerical calculation of the dynamic behavior in the sample.