Polarization-insensitive electroabsorptive modulation using interdiffused InGaAs(P)-InP quantum wells

Abstract

This is a theoretical study to demonstrate the use of interdiffusion in the realization of polarization insensitivity at the band-edge. Two InGaAs-InP quantum well as-grown structures have been investigated: one with lattice-matched condition and the other with small as-grown tensile strain (0.15%). The interdiffusion is considered to take place on the Group V (As and P) sublattice only. As a result, a tensile strain is produced which merges the heavy- and light-hole states in order to achieve polarization insensitivity. Criteria to develop polarization-insensitive quantum wells (QW's) using interdiffusion are presented here. When the two-phase interdiffusion mechanism is modeled, the results show that the well barrier interfaces of the QW maintain an abrupt profile while the well width remains constant after interdiffusion. The two interdiffused QW structures considered here can produce polarization insensitive electroabsorption at operation wavelengths around 1.55 μm. The one with lattice-matched condition is particularly attractive since it only requires an easy (high-yield) fabrication process with a simple postprocessing thermal annealing to achieve polarization insensitivity.