Design and Optimization of 1.55 μm AlGaInAs MQW Polarization Mode Controllers

Abstract

A 1.55 μm AlGaInAs multi-quantum-well (MQW) ridge waveguide polarization mode controller (PMC) is proposed. The design is based on an asymmetric half-ridge waveguide structure in which the ridge is shallow etched on one side and has a deeply etched mesa structure on the other side. The Finite-Element Method (FEM) was used to simulate the PMC and optimize its structural parameters comprehensively. Furthermore, the fabrication tolerances were also investigated in detail. The optimized PMC has a polarization conversion efficiency (PCE) of around 92.5% with a half-beat length of 1250 μm. When the PMC length was fixed at 1250 μm, to achieve a PCE derivation less than 8%, the tolerances for the ridge waveguide width and shallow etch height were 1.60 μm to 1.65 μm and 2.13 μm to 2.18 μm, respectively. In order to reduce interband gap absorption loss, the quantum well intermixing (QWI) technique was used in the model to realize a blueshift (200 nm) in the PMC. QWI is a simple, flexible, and low-cost technique for fabricating a PMC integrated with a laser diode and reduces parasitic reflections, which would otherwise degrade the overall performance. QWI also eliminates MQW material anisotropy and alleviates the birefringence effect without the need for regrowth, achieving nearly uniform properties as a bulk material.

Monolithically Integrated AlGaInAs MQW Polarization Mode Converter Using a Stepped Height Ridge Waveguide

“…However, to integrate MQW-based components such as efficient lasers with bulk PMCs, relatively complicated buttjoint PIC techniques involving re-growth are usually used. To simplify the fabrication processes, we have proposed monolithically integrating an InP-AlGaInAs MQW-based sidewall grating distributed-feedback (DFB) laser with an asymmetric half-ridge waveguide PMC [12]. The design used a standard MQW laser structure, with quantum well intermixing (QWI) being used to enlarge the bandgap of the PMC section, reducing the absorption loss, and removing the birefringence associated with the MQW waveguide core.…”