High-contrast/low-voltage normally on InGaAs/AlGaAs asymmetric Fabry-Perot modulator

An asymmetric Fabry-Perot cavity modulator is proposed with a 50-period In/sub 0.15/Ga/sub 0.85/As/Al/sub 0.30/Ga/sub 0.70/As strained-layer superlattice active layer. The back Bragg reflector consists of 25 periods of GaAs/AlAs layers while for the front reflector of the device the natural reflection of the air-semiconductor interface was used. Spectral measurements as a function of the applied reverse voltages showed a change in reflectivity from 33% for 0 V reverse bias to 5% for 7 V, at a wavelength of 969 nm. This gives a maximum contrast ratio of 8.3 dB and an insertion loss of 4.9 dB. For higher voltages applied across the device, the reflectivity increases again.>