Use of acousto-optical resonant conditions in GaAs and InP for the creation of high-efficiency 2-GHz bandwidth Bragg cells

Abstract

We demonstrated in this work the possibility of application of the effect of resonant acousto- optical (AO) interaction for the creation of wide band and high efficiency Bragg cells on gigahertz frequencies. The main principle of this effect consists in heat there exists the optimum photon energy (very close to the band gap of semiconductor sample) where the optical absorption is still not big enough but the figure of merit already several times higher in comparison with one when the photon energy is fat from the band gap. We have shown theoretically that the optimization of multilayer thin film piezoelectric transducers allows to create AO Bragg cells (deflectors and modulators) working in resonant conditions and having very high diffraction efficiency (more than 10%) and very wide frequency band (up to 2 GHz). This optimization based on the use of the acoustical matching scheme-asynchronous transform, analogous to one in electrotechnics. Experimental devices represent the cells with crystal plates of GaAs and InP of (100) and (110) cut having the multilayer thin film transducer on the butt-end that has been matched with microstrip transmission line. Characteristics of created AO cells reach: 10% per 1 Watt of electrical power; 2 GHz frequency band with 8 MHz frequency resolution. The obtained experimental results show a good agreement with theoretical predictions.