Wavelength selective detection using excitonic resonances in GaAs/AlGaAs P-I-(MQW)-N structures

Abstract

The quantum confined Stark effect causes a strong wavelength and voltage dependence of photocurrent near excitonic resonances which is used to study the wavelength selectivity of p-i(MQW)-n photodiode. For a parallel input of optical bits each coming at a different wavelength, the selectivity is considered good if the state of a [lambda]i wavelength bit can be detected regardless of the [lambda]j (j [not equal to] i) state of the bits. Photocurrent is found to have very good selectivity if [lambda]j bits are all zero, i.e. the optical information is serial. However, we find that differential photocurrent ([Delta] Iph/[Delta]V) provides a good selectivity for random states of [lambda]j bits (i.e. parallel input). Four channel selectivity is demonstrated at 200K. Specially designed quantum well structures can greatly improve this selectivity.