Efficient InGaAsP MQW-based polarization controller without active-passive integration

Abstract

Carrier-injection-based efficient polarization controller with a strained InGaAsP multiple-quantum-well (MQW) layer is demonstrated on a regrowth-free InP platform. We employ a straight-line device configuration by cascading an asymmetric polarization rotator (PR) to provide a fixed polarization conversion and a polarization-dependent phase shifter (PD-PS) to enable tunable polarization rotation. Based on a novel design concept, both the PR and PD-PS sections are integrated monolithically without active-passive integration. Using the fabricated device, we experimentally demonstrate efficient polarization conversion over the entire Poincaré sphere with a total current of less than 40 mA. With the capability of monolithically integrating other InP-based active components, the demonstrated scheme should be attractive for various applications, such-as low-cost coherent communication, microwave photonics, and quantum key distribution.

Design and Optimization of 1.55 μm AlGaInAs MQW Polarization Mode Controllers

“…Previous researches on MQW-based PMCs have mostly focused on fabricating sources of polarization tunable light, and such sources require the PMC to be integrated with a polarization-dependent phase shifter (PD-PS) [6]. In addition, most reports have used relatively complicated butt-joint integration techniques [16].…”

“…The purpose of these polarization tunable sources is to convert pure TE-or TM-polarized light into an arbitrarily chosen state of polarization, and the PMC is required to have a 50% TE-to-TM polarization conversion efficiency [15]. In addition to the birefringence arising from the waveguide geometry, the birefringence of the MQW also affects the polarization conversion in the PMC [6], with the MQW birefringence having the opposite sign to that arising from the asymmetric waveguide. The effect of MQW birefringence is therefore to increase L π .…”

“…In order to integrate bulk material PMCs with LDs based on MQW structures, researchers have to use relatively complicated butt-joint PIC techniques involving regrowth. Although an InGaAsP MQW PMC using a particular design (a 400 nm thick 1.25 Q layer underneath the MQW structure) has been reported [6], its maximum polarization conversion efficiency (PCE) was not stated. Compared with bulk-material PMCs, the inherent birefringence of MQW PMCs needs to be taken into account [6], which disturbs the optimal rotation of state of polarization (SOP) on the Poincaré sphere, and this is the most challenging aspect of an MQW-based PMC design.…”

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

“…sources, detectors, and other components in photonic integrated circuits (PICs). An increasing number of devices including polarization-dependent phase shifters (PD-PSs) [2], [3] and laser diodes (LDs) [4] use multiple-quantum-well (MQW) structures as the active region; it is, therefore, desirable to design PMCs compatible with MQW structures. For a polarization tunable source, the integration of the monolithic PMCs waveguides with LDs requires a good transverse mode-match.…”

“…For a polarization tunable source, the integration of the monolithic PMCs waveguides with LDs requires a good transverse mode-match. A PMC based on a particular MQW structure design has been reported that can convert TE-or TM-polarized light into an arbitrarily chosen state of polarization (SOP) [2] albeit with only a 50% TE to TM polarization conversion efficiency (PCE) [3]. The crucial issue for MQW PMCs is the inherent birefringence of the MQW, which disturbs the optimal rotation of the SOP on the Poincaré sphere.…”