Polarization control of quantum dot single-photon sources via a dipole-dependent Purcell effect

We study single photon emission from excitons confined in single InAs quantum dots in elliptical pillar microcavities, demonstrating a polarization dependence of the Purcell effect. The enhancement of the radiative decay rate and emission intensity differs for the two components of the exciton doublet, suggesting each exciton state corresponds to a well-defined dipole direction in the sample plane. This allows the linear polarization of the single photon source to be selected between orthogonal directions by tuning the exciton emission energy between different polarization modes of the cavity.

Figure 1

Polarized $\mu \mathrm{PL}$ from pillar A. (a) An exciton doublet, on resonance with the $x$ polarized cavity mode, has different intensities for the $x$- and $y$-polarized emission. The solid (dashed) arrow marks the positions of the $x\left(y\right)$ polarized cavity mode. Inset: high excitation density $\mu \mathrm{PL}$ showing the $x$- (solid line) and $y$- (dashed line) polarized cavity modes. (b) Time-resolved measurements for the $x$- (solid line) and $y$- (dashed line) polarized exciton states.

Figure 2

Typical histogram of the second-order correlation of an exciton on resonance with the higher wavelength cavity mode at $5\mathrm{K}$.

Figure 3

Temperature-dependent $\mu \mathrm{PL}$ from pillar B, the $x$- (solid line) and $y$-polarized (dashed line) exciton states are on resonance with (a) the $y$-polarized cavity mode (dashed arrow) at $5\mathrm{K}$ and (b) the $x$-polarized cavity mode (solid arrow) at $31\mathrm{K}$.

Figure 4

(a) Temperature-dependent lifetimes of the $x$ (solid line) and $y$ (dashed line) exciton spin states in pillar B. (b) Spontaneous emission rate enhancement compared to an off-resonance dot.