Compact chirped fiber Bragg gratings for single-photon generation from quantum dots

To realize a scalable source of frequency-multiplexed single photons, it is important to have an ensemble of quantum emitters that can be collectively excited with high efficiency. Semiconductor quantum dots hold great potential here, due to their excellent photophysical properties. The most efficient scheme to excite a quantum dot ensemble employs chirped laser pulses, relying on the so-called adiabatic rapid passage, is due to its robustness against spectral and intensity fluctuations. Yet, the existing methods to generate chirped laser pulses coupled to a quantum emitter are bulky, lossy, less flexible, and mechanically unstable, which severely hampers the prospects of a practical quantum dot device. Here, we present a compact, robust, and high-efficiency alternative for chirped pulse excitation of solid-state quantum emitters. Our simple plug-and-play module consists of chirped fiber Bragg gratings (CFBGs) that provide high dispersion, tailored to ~ 800 nm with a ~ 5 nm bandwidth that accommodates the quantum dot spectral variability. To characterize and benchmark the performance of our method, we demonstrate the chirped excitation of a GaAs/AlGaAs quantum dot that shows excellent agreement with theoretical simulations and establish high-fidelity single-photon generation. Our method can be tailored for a wide spectral range and dispersion requirements and is a significant milestone toward realizing a direct fiber-coupled, plug-and-play quantum dot photon source.