Physicists at the University of California, Santa Barbara (Santa Barbara, CA), have demonstrated an on-chip, polarization-switchable, single-photon source using the Stark effectthe shifting of spectral lines in the presence of an electric field. The device starts with a self-assembled quantum dot embedded in a high-quality, electrically gated, micropillar cavity. An elliptical aperture breaks the polarization degeneracy of the fundamental mode, creating two linearly polarized modes with slightly different energies 194 µeV apart.
The emission from the quantum dot is electrically tuned into resonance with two orthogonally polarized cavity modes, enabling switching of the dominant polarization modes, (horizontal and vertical). The polarization of the device was possible at a rate of up to 300 kHz, temporally limited only by the thermal conductivity of the device, and in principle could reach gigahertz frequencies by reducing the current, the contact resistance, and the parasitic capacitance. This type of single-photon source with a polarization switch could work as an excitation source for quantum systems or in classical optical networking systems. Contact Matt Rakher at [email protected].