Highly Polarized InGaAsP/InP-Air-Gap Elliptical Micropillar Cavity for Single Photon Source at 1.55 µm Communication Band

Elliptical micropillar cavity owns two orthogonally linearly polarized modes that split from the polarized degenerate fundamental mode of the circular micropillar cavity. The quantum dot embedded in such cavity can emit polarized single photon by coupling one polarized mode. However, if the emitted linewidth covers both modes, the polarization purity of the single photons may not be guaranteed. Here we present a novel elliptical micropillar cavity that may get rid of the disturbance of the other polarized cavity mode. The proposed microcavity is based on the InP-air-gap structure, which is able to solve the problem of low reflectivity in InP-based material systems. This unique cavity allows us to manipulate both quality factors and mode wavelengths of the linearly polarized cavity modes by regulating the InP-air-gap layers, and achieve high polarization characteristics and quality factor at 1.55 $\mu$m communication band with low eccentricity.