Variation in damage thresholds of Si photodiodes with laser pulse duration

The damage thresholds of Si PIN photodiodes irradiated by 800nm fs laser with pulse duration of 60fs have been measured. The damage thresholds of Si photodiodes irradiated by laser pulse of different duration from 1s to 60fs are present and discussed. Experimental data indicates that damage fluence increases approximately but not strictly with square root of pulse duration for pulses longer than 10ns. The output signal analysis shows the damage was caused mainly by thermal effect. However the damage threshold to 60fs laser is 0.1J/cm2, which deviates apparently from what general temperature distribution model predicted．