In order to study deeply damage mechanism of HgCdTe crystal irradiated by multi-pulsed CO2 laser and obtain the
characteristics of surface morphological and chemical composition changes. Firstly, Irradiation effect experiment is
conducted on the Hg0.826Cd0.174Te crystal by pulsed CO2 laser, which has a pulse width of 200ns and repetition frequency
ranges from 1 Hz to 100 kHz. Then morphological and chemical composition changes of Hg0.826Cd0.174Te crystal is
measured by field emission scanning electron microscope (FESEM) and damage threshold is obtained by morphology
method. Finally, the impact of laser power density on morphological and chemical composition changes is analyzed. The
research results show that: damage threshold of Hg0.826Cd0.174Te crystal which is irradiated by multi-pulsed CO2 laser is
950 W/cm2. The crystal surface melting phenomenon is very obvious, the obvious crack which is caused by thermal
stress is not found in the surface, and a large number of bulges and pits are taken shape in the laser ablation zone.
Chemical composition changes of the crystal are obvious, and a lot of O element is found in the laser ablation zone. With
the increase of laser irradiation power, the content of Hg element decrease rapidly, the content of Cd, Te and O element
raise by degrees, and chemical composition changes of the crystal are more and more obvious. When the irradiation
power density is 1.8kW/cm2, the surface becomes smooth in the ablation zone due to the impact of laser impulse force,
and the content of the chemical compositions is that Hg accounts for 0.23%, Cd accounts for 21.38%, Te accounts for
26.27%, and O accounts for 52.12%. The conclusions of the study have a reference value for the Hg0.826Cd0.174Tecrystal
in the application of making infrared detector and pulsed CO2 laser in the aspect of laser processing.