Reflective vertical cavity semiconductor saturable absorber for functional operations with thermal limitations and saturable index change

Abstract

A numerical simulation on absorptive bi-stability and resonance wavelength shift is carried out in a vertical-cavity semiconductor saturable absorber consisting of a Fabry–Perot cavity embedded with quantum-wells (QWs) material with due consideration of its nonlinear index change and thermal effects. Necessary equations are derived and discussions are made for optimization of cavity parameters required for all-optical logic operations. For InGaAs/InP quantum wells, the resonant wavelength is blue-shifted by 4 nm and red-shifted by 16 nm for input intensities of 0.15 I S and 2.2 I S , respectively where I S represents the saturation intensity. Faithful NAND operation with extinction over 85% is possible for a signal intensity change (Δ I in ) of 0.5I S in a sample with saturated nonlinear index ( n 2S ) of 0.0012, unit small-signal absorption ( α 0 d) and non-saturable absorption ( α ns d) of 0.025. Whereas, the NOR operation is obtained with extinction over 80% for Δ I in = 1.0I S in a sample with n 2S = 0.0012 , α 0 d = 1.0 and α ns d = 0.0375 , respectively.