Theoretical and experimental investigation of external-stress effect on quantum-well-based semiconductor interferometer performance

We investigate characteristic fluctuations in multi-quantum well (MQW)-based waveguides whose absorption spectrum experimentally changes as a ∼5 nm blue shift when dielectric passivation layers are employed. We theoretically show that the blue shift corresponds to a ∼0.03% compressive strain in the MQW resulting in a group refractive index change (Δn_g) of ∼−0.01. The estimated Δn_g agrees with an experimentally obtained free spectral range of transmittance of an asymmetric Mach-Zehnder interferometer composed of the MQW structure. The results indicate that our theoretical estimation is an efficient way to evaluate the MQW-based waveguide performance with an external stress. (author)