Nonlinear optical properties of conduction electrons in semiconductors

An analysis is made of the influence of a strong electromagnetic wave of frequency Ω₁ on the intraband absorption of a weak wave of frequency Ω₂≠Ω₁ by the conduction electrons. The absorption coefficient is calculated for the quantum case when the frequencies Ω₁ and Ω₂ are high compared with the average electron energy. The presence of a strong wave increases the absorption of the weak wave if the conduction electrons are scattered by acoustic phonons and it reduces this absorption if the electrons are scattered by impurities.