Development of optical breakdown on the surfaces of semiconductors subjected to two laser beams of different frequencies

An experimental investigation was made of the characteristic features of optical breakdown on the surface of silicon and germanium subjected to laser pulses of wavelengths 1.06 and 10.6 μm with a short time delay between them. A theoretical analysis was made of the main experimental dependences. Reduction in the breakdown threshold at the wavelength of 10.6 μm was attributed to intraband absorption by free carriers, which appeared as a result of photoexcitation of a semiconductor with pulsed 1.06 μm radiation. A strong increase in the breakdown threshold occurred near a plasma resonance for the CO₂ laser radiation.