Regrowth-free AlGaInAs MQW polarization controller integrated with sidewall grating DFB laser

TL;DR

This paper presents an integrated AlGaInAs quantum well source with polarization control capabilities, combining a polarization mode converter, differential phase shifter, and sidewall grating DFB laser in a monolithic device.

Contribution

It introduces a novel monolithic integration of polarization control components with a DFB laser using a single epitaxial step and two dry etching steps, achieving high efficiency and polarization rotation.

Findings

98% TE to TM polarization conversion efficiency at 1555 nm

60-degree polarization rotation on the Poincaré sphere

Wide range of polarization control with low bias voltage

Abstract

We report an AlGaInAs multiple quantum well integrated source of polarization controlled light consisting of a polarization mode converter PMC, differential phase shifter(DPS), and a side wall grating distributed-feedback DFB laser. We demonstrate an asymmetrical stepped-height ridge waveguide PMC to realize TE to TM polarization conversion and a symmetrical straight waveguide DPS to enable polarization rotation from approximately counterclockwise circular polarization to linear polarization. Based on the identical epitaxial layer scheme, all of the PMC, DPS, and DFB laser can be integrated monolithically using only a single step of metalorganic vapor phase epitaxy and two steps of III V material dry etching. For the DFB-PMC device, a high TE to TM polarization conversion efficiency 98% over a wide range of DFB injection currents is reported at 1555 nm wavelength. For the DFB-PMC-DPS device, a 60 degree rotation of the Stokes vector was obtained on the Poincar\'e sphere with a range of bias voltage from 0 V to -4.0 V at IDFB is 170 mA.