We propose an optical nanofiber cavity to enhance spontaneous emission of a single quantum emitter over a broad wavelength range, and tunability in resonance wavelength ~60 nm is achieved by varying diameter range ~150 nm.
We propose a geometry-driven strategy for achieving tunable single-photon coupling in an optical nanofiber cavity (ONFC), where the resonance wavelength is controlled by tailoring the optical nanofiber (ONF) diameter and the grating pitch. By adjusting these structural parameters, the cavity response can be systematically tuned without modifying the material platform or by using any external control schemes. There is a wide spectral resonance wavelength variation of 60, 106, and 70 nm that can be achieved by varying the ONF diameter in the range of 150 nm, the grating pitch of 60 nm, and the elongation of 400 µm, respectively. The integration of a quantum emitter (QE) within the cavity region retains the geometry-dependent tunability of the system. This enables controlled spectral alignment between the QE emission wavelength and the cavity resonance. For a typical QE placed on the ONFC operating around 640 nm, it facilitates a strong spontaneous emission enhancement with a Purcell factor of ∼20 and a coupling efficiency of ∼94% into the ONF-guided mode. The scattering-limited cavity performance yields a quality factor, finesse, and one-pass power loss of 2930, 104, and 2.9%. Owing to its geometry-controlled design, the proposed device can be readily adapted to different QE wavelengths through appropriate structural optimization, offering a compact and fiber-integrated platform for quantum information and communication applications.
We present a novel approach to enhance the spontaneous emission rate of single quantum emitters in an optical nanofiber-based cavity by introducing a narrow air-filled groove into the cavity. Our results show that the Purcell factor for single quantum emitters inside the groove of the nanofiber-based cavity can be at least six times greater than for such an emitter on the fiber surface when using an optimized cavity mode and groove width. Moreover, the coupling efficiency of single quantum emitters into the guided mode of this nanofiber-based cavity can reach up to ∼80% with only 35 cavity-grating periods. This new system has the potential to act as an all-fiber platform to realize efficient coupling of photons from single emitters into an optical fiber for quantum information applications.