Optimised multiple quantum well phase modulator

Reports 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 degrees /Vmm at the optimum bias of 6 V, giving a phase change in a 385 mu m-long device of 63 degrees 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.