Nonlinear spectroscopy of narrow-gap Pr—Ba—Cu—O semiconductor films with the aid of biharmonic pumping

Abstract

The dependences of the efficiency η of self-diffraction of picosecond pulses on their frequency detuning Ω were determined for Pr—Ba—Cu—O semiconductor films. These dependences were similar to those already reported (for Ni and Y—Ba—Cu—O in the resistive phase) and had a central peak (η ~ 10-7 for ≤ 10 cm-1) and wide wings (η ~ 10-9 for ≥ 10 cm-1) with a jagged profile because of phonon resonances. An analysis was made of the causes of this similarity, of the asymmetry of η(Ω) relative to the sign of η, and of specific temperature effects. Although the position of a combination electron resonance (interband transition edge) of Pr—Ba—Cu—O was within the range of variation of η, its identification was complicated by the presence of nearby (on the scale of Ω) phonon modes.