Highly efficient single photon sources based on fiber-coupled quantum dot photonic crystal cavities

Abstract

An efficient single photon source is indispensable for quantum information such as quantum communications and quantum computers. Single photon sources using single trapped atom or ion have been developed early, but their efficiency was not enough to use in practical. Here, we propose a new type of a single photon source comprised with GaAs quantum dot photonic crystal waveguides and a highly curved tapered fiber. It is very efficient to directly couple quantum dots embed in semiconductor material with high refractive index to the tapered fiber. However, the integration of them in a cryostat at low temperature is not trivial. To resolve this problem, a cryostat is remodeled and equipped with nano-stages for moving of photonic crystals and the tapered fiber. Photoluminescence of various photonic crystal cavities was measured with the integrated system in the remodeled cryostat through the tapered fiber. Also, we can collect single photons through the fiber from quantum dot photonic crystal waveguide, as the fiber contacts to the waveguide. To confirm single photon nature of collected signal, the second correlation was measured with Hanbury Brown-Twiss setup. $g^{(2)}(0)$ value is 0.15, and it shows truly single photon streams. Based on measured transmission of all optics and detection efficiency, coupling efficiency to the fiber is estimated up to 26%, which is much enhanced value compared with others.