CPM Seminar

Ultrafast all-optical switching and optical nonlinearity in GaAs, InGaAs and InP

Hiroyuki Bando

Department of Nanomaterial Science
Chiba University

Optical semiconductor devices with ultrafast response less than 1ps have been studied for ultrafast optical communication systems. All-optical switching devices of semiconductors based on optical nonlinearity are promising devices of those devices. The all-optical switching devices control pulses of signal light with control light without using electronic circuits. The saturable absorption in many material systems has been investigated for the all-optical switching devices. To reduce the recovery time from the absorption saturation state to the normal state, some methods such as low-temperature-growth (LT), impurity doping and so on are needed on preparing the samples. We have investigated the saturable absorption properties of temporal response and wavelength dependence by fs-lasers in LT-GaAs/AlAs multiple quantum wells (MQWs) and LT-InGaAs/InAlAs strained MQWs grown by molecular beam epitaxy (MBE) method. Two-photon absorption (TPA) is also an attractive nonlinear optical process for the ultrafast optical devices since it is an instantaneous process without need of photo-carrier accumulation. We have demonstrated extremely fast switching action in InP and InGaAs in wide range of wavelength by fs-lasers. In addition to the temporal response, the polarization dependence is important for device applications. We have investigated the anisotropy in TPA effect with linear-polarization beams in detail, and determined complete optical parameters, third-order nonlinear susceptibility tensor elements, for wavelength-degenerated TPA in InP.