MEMS-Based Tuning of InGaAs/GaAs Quantum Dot-VCSOA

The wavelength tuning mechanism for quantum dot vertical cavity semiconductor optical amplifiers (QD-VCSOAs) is investigated theoretically. It is shown that the narrow optical gain bandwidth of QD-VCSOA cannot be extended considerably by reduction of the mirror reflectivity. Gain spectra of the MEMS tunable QD-VCSOA is calculated by including the effect of bias voltage on the air-gap thickness, effective mirror reflectivity, gain enhancement factor, and resonance wavelength of the cavity. The MEMS tuning scheme is evaluated for a semiconductor-coupled cavity design and operation in reflection mode under electrical pumping. The standing wave profile in the cavity is calculated by transmission matrix method to consider possible displacement of the standing wave peaks from each QD stack due to changes in the resonance wavelength of the cavity. It is found that such a system enables the cavity-limited gain spectra to be dynamically swept over a range effectively extending the usable gain bandwidth of the amplifier.