Acoustically induced optical second harmonic generation in InAs

Abstract

Acoustically induced optical second harmonic generation (AIOSHG) was investigated in single and polycrystalline InAs. With increasing acoustic power, the AIOSHG for fundamental CO laser light (λ = 7.1 µm) increases and achieves its maximum value at acoustic power density of about 1.72 W cm–2. The values of the AIOSHG were substantially higher for the polycrystalline InAs than for inorganic photo-refractive and ferroelectrics materials. With decreasing temperature, the AIOSHG signal strongly increases below 50 K, which correlates with the occurrence of condensation of low-frequency anharmonic ‘soft’ phonon modes. The AIOSHG maxima were observed at acoustical frequencies ranged between 7–11 kHz. Comparing the obtained results with the acoustically induced IR spectra at low temperature, one can conclude that the observed effect is associated with acoustically-induced electron–phonon anharmonicity.