Аннотация:An experimental investigation was made of the dependence of the efficiency eta of self-diffraction of picosecond (approximately 20 ps) light pulses on their frequency offset OMEGA in ultrathin (6-30 nm) narrow-gap PbTe semiconductor films. The dependences eta(OMEGA) exhibit complex two-photon electron resonances with positions that change radically with the film thickness. The results are interpreted as a manifestation of the quantum size (quantum well) effect in the course of transitions from the light-hole to the heavy-hole band.An experimental investigation was made of the dependence of the efficiency η of self-diffraction of picosecond (~20 ps) light pulses on their frequency offset Ω in ultrathin (6—30 nm) narrow-gap PbTe semiconductor films. The dependences η(Ω) exhibit complex two-photon electron resonances with positions that change radically with the film thickness. The results are interpreted as a manifestation of the quantum size effect in the course of transitions from the light-hole to the heavy-hole band.