Bright Purcell Enhanced Single-Photon Source in the Telecom O-Band Based on a Quantum Dot in a Circular Bragg Grating

The combination of semiconductor quantum dots with photonic cavities is a promising way to realize nonclassical light sources with state-of-the-art performances regarding brightness, indistinguishability, and repetition rate. Here we demonstrate the coupling of InGaAs/GaAs QDs emitting in the telecom O-band to a circular Bragg grating cavity. We demonstrate a broadband geometric extraction efficiency enhancement by investigating two emission lines under above-band excitation, inside and detuned from the cavity mode, respectively. In the first case, a Purcell enhancement of 4 is attained. For the latter case, an end-to-end brightness of 1.4% with a brightness at the first lens of 23% is achieved. Using p-shell pumping, a combination of high count rate with pure single-photon emission (g (2) (0) = 0.01 in saturation) is achieved. Finally, a good single-photon purity (g (2) (0) = 0.13) together with a high detector count rate of 191 kcps is demonstrated for a temperature of up to 77 K.