Design of InGaAsP phase modulator with asymmetrically coupled quantum wells for efficient polarization modulation

Monolithically integrated high-speed polarization modulators are finding emerging applications in the fields of optical communication, quantum key distribution, and radio-frequency photonics. Here, we design an efficient polarization modulator with InGaAsP asymmetrically coupled quantum wells (ACQWs) on InP. By using two quantum wells separated by a thin barrier layer, the behaviors of the heavy holes and the light holes can be controlled independently under an external bias. As a result, we can induce an anomalous quantum-confined Stark effect, having a strong polarization dependence. With an optimized ACQW design, we numerically demonstrate a large polarization-dependent refractive index modulation of 7.1 x 10(-3)at an applied field of 1.8 V mu m(-1). Using a 1 mm long device, we estimate that 2 pi rotation of the Stokes vector can be achieved with negligible absorption at a driving voltage of only 0.75 V.