Optimised multiple quantum well phase modulator

Publisher Website
Google Scholar
Abstract
The quantum confined Stark effect (QCSE) in GaAs/AlGaAs multiple quantum well structures has been shown by several authors to cause large changes of refractive index1.2 and absorption coefficient3.4 near the band edge which are potentially of use for phase modulation applications. Hence in a phase modulator there is necessarily a trade-off between the magnitude of the phase modulation, highest near the exaton features, and that of the amplitude modulation. In this letter we report a pin phase modulator that has been optimised for maximum phase change relative to the contrast (ratio of transmission in the ‘on’ state to that in the ‘off’ state), within certain constraints: the maximum tolerable contrast and the maximum zero bias absorption loss were chosen to be 2 and 50%, respectively. The parameters optimised were the operating wavelength, the number of quantum wells in the active layer and the position of that layer, the operating bias, the device length and the background doping in the intrinsic region. The optimised device was measured to have a phase modulation figure of merit of 27°/V mm at the optimum bias of 6 V, giving a phase change in a 385 μm-long device of 63 at this bias. The corresponding contrast was approximately 1.4. Photocurrent measurements show that the zero bias absorption loss is also within the 50% limit.

This publication has 0 references indexed in Scilit: