Cornelius Nawrath

Several emission features mark semiconductor quantum dots as promising non‐classical light sources for prospective quantum implementations. For long‐distance transmission and Si‐based on‐chip processing, the possibility to match the telecom C‐band is decisive, while source brightness and high single‐photon purity are key features in virtually any quantum implementation. An InAs/InGaAs/GaAs quantum dot emitting in the telecom C‐band coupled to a circular Bragg grating is presented here. This cavity structure stands out due to its high broadband collection efficiency and high attainable Purcell factors. Here, simultaneously high brightness with a fiber‐coupled single‐photon count rate of 13.9 MHz for an excitation repetition rate of 228 MHz (first‐lens single‐photon collection efficiency ≈17% for NA = 0.6), while maintaining a low multi‐photon contribution of is demonstrated. Moreover, the compatibility with temperatures of up to 40 K attainable with compact cryo coolers, further underlines the suitability for out‐of‐the‐lab implementations.