Optical Absorption for Acoustic Flux in Semiconductive CdS Single Crystal

抄録

The optical modulation by acoustoelectric domain has been observed in semiconductive CdS single crystal at room temperature. The nature and mechanism for this optical modulation are discussed, as compared with the Franz-Keldysh effect by the high electric field. The electric field in the domain observed here is saturated by 5 kV/cm, while the optical modulation signals rise linearly. There is little shift of the edge, calculated from the experimental and theoretical results of the Franz-Keldysh effect at the saturation field. Furthermore, the optical modulation signals are clearly visible for several nanoseconds after the applied voltage is removed. Therefore, the optical modulation is not caused by the high electric field but is associated with the intense acoustic flux in the domain. Using the optical modulation technique, the acoustic flux reflected at the anode end is observed even for the application of the voltage. The propagation velocity of acoustic domain, where the voltage is applied perpendicular to c axis of the crystal, varies from 1.75×10⁵ cm/sec to 1.70×10⁵ cm/sec, according as the applied field is increased up to 2110 V/cm.