Frequency conversion of optical signals in p-i-n photodiodes

A planar InGaAsP/InGaAs/InGaAsP p-i-n photodiode has been fabricated and used for frequency conversion of two optical signals. Nonlinear properties of the photodiode have been investigated. It is shown that photodiode responsivity R(V) dependence on bias voltage can be characterized by a parameter of the nonlinearity A, which is equal to R(V)middotR'(V) and the maximal conversion efficiency is achieved at the bias voltage where the parameter A has the maximal value