Optical control of transmittance by photo-induced absorption effect in InGaN/GaN structures

Abstract

We have investigated the optical modulation properties of transmittance using the photo-induced absorption effect in 10 periods of In 0.10Ga0.90N/GaN (60nm/60nm) structures grown by metal-organic chemical vapor deposition. Transmittance was modulated by 22% at 398 nm under a continuous-wave laser pumping at 405 nm with an intensity of 1 W/cm2. We have also investigated the influences of He+ ion irradiation on optical modulation properties, such as magnitude, time response, and spatial resolution. The modulation of transmittance reduces at a high pump on/off frequency mainly due to the relatively slow recovery process. The ion-irradiated samples showed a faster recovery and this resulted in the enhancement of the cutoff frequency from 30 to 130kHz at 1 W/cm2. The irradiation process also improved the spatial resolution at the expense of the magnitude of transmittance modulation. However, the spatial resolution of the device is of the order of 100 μm; thus, substantial improvement is essential for two-dimensional optical device applications. © 2005 The Japan Society of Applied Physics.