Abstract

Quantum-size effect (QSE) is intensively studied by optical spectroscopy where frequencies of one-photon electron resonances are usually determined.¹ Therefore, investigating structures based on narrow-band semiconductors, it is necessary to operate in far infrared range. To avoid this problem it is possible to investigate such structures by biharmonic pumping (BP) based on two-photon excitation. Recently, in Y-Ba-Cu-O study, we have observed two-photon resonance related to the superconducting gap.³ In BP, the sample is excited by waves with different frequencies ω_1,2 and wave vectors k_1,2. Due to self-diffraction, new wave with ω₃ = 2ω₁−ω₂ and k₃ = 2k₁ − k₂ is generated. In the vicinity of two-photon transitions, self-diffraction efficiency η demonstrates resonant dependence on beat frequency Ω = ω₁ – ω₂. We supposed that resonances related to two-photon transitions between subbands renormalized (due to QSE) may appear on this dependence.

© 1994 IEEE