GaAs/AlAs Multilayer Cavity with InAs Quantum Dots Embedded in Strain-Relaxed Barriers for Planar-Type Optical Kerr Gate Switches

Abstract

A GaAs/AlAs multilayer cavity containing self-assembled InAs quantum dots (QDs) embedded in strain-relaxed In0.35Ga0.65As barriers has been studied for planar-type optical Kerr gate switches. The multilayer cavity structure with smooth GaAs/AlAs interfaces was successfully grown on a (001) GaAs substrate by molecular beam epitaxy despite the lattice strain relaxation induced in the half-wavelength (λ/2) cavity layer. Time-resolved optical measurements at the cavity mode (λ= 1.46 µm) were performed by a pump–probe method at room temperature. Although only two layers of the InAs QDs were inserted into the λ/2 cavity layer, a large transmission change caused by the absorption saturation in the resonant QDs was clearly observed. The temporal profile was dominated by a fast (∼16 ps) decay component, which comes from carrier relaxation into the nonradiative centers arising from the lattice strain relaxation. We have also shown that an ultrafast response time (<1 ps) of the strongly enhanced optical Kerr signal is determined by the photon lifetime in the multilayer cavity.