The study of transient bleaching effect of indirect bandgap semiconductors induced by femtosecond laser

On the basis of the development of the model of indirect bandgap semiconductors’ transient state spectral absorption coefficient, and ultrafast carrier dynamics, the theoretical model was established, which could well describe the transient bleaching effect of indirect bandgap semiconductors induced by femtosecond laser. Numerical simulation was carried out to investigate the characteristic of the transient bleaching effect. And the results indicate that femtosecond laser could instantaneously degrade the spectral absorption of indirect bandgap semiconductors. The recovery of spectral absorption coefficient is fast at beginning, but slows down after that. The transient bleaching effect induced by femtosecond laser with narrower pulse width is much intenser in the carrier thermal relaxation state, but much weaker in the carrier quasi-thermal equilibrium state.