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Photon loss is one of the key challenges to overcome in complex photonic quantum applications. Photon collection efficiencies directly impact the amount of resources required for measurement‐based quantum computation and communication networks. Promising resources include solid‐state quantum light sources. However, efficiently coupling light from a single quantum emitter to a guided mode remains demanding. In this work, photon losses are eliminated by maximizing coupling efficiencies in an emitter‐to‐fiber interface. A waveguide‐integrated 'Sawfish' photonic crystal cavity is developed and finite element (FEM) simulations are employed to demonstrate that such an emitter‐to‐fiber interface transfers, with 97.4 % efficiency, the zero‐phonon line (ZPL) emission of a negatively‐charged tin vacancy center in diamond (SnV−) adiabatically to a single‐mode fiber. A surrogate model trained by machine learning provides quantitative estimates of sensitivities to fabrication tolerances. The corrugation‐based Sawfish design proves robust under state‐of‐the‐art nanofabrication parameters, maintaining an emitter‐to‐fiber coupling efficiency of 88.6 %. Applying the Sawfish cavity to a recent one‐way quantum repeater protocol substantiates its potential in reducing resource requirements in quantum communication. [ABSTRACT FROM AUTHOR]

Color centers in diamonds are quantum systems with optically active spin-states that show long coherence times and are, therefore, a promising candidate for the development of efficient spin–photon interfaces. However, only a small portion of the emitted photons is generated by the coherent optical transition of the zero-phonon line (ZPL), which limits the overall performance of the system. Embedding these emitters in photonic crystal cavities improves the coupling to the ZPL photons and increases their emission rate. Here, we demonstrate the fabrication process of "Sawfish" cavities, a design recently proposed that has the experimentally realistic potential to simultaneously provide a high waveguide coupling efficiency and significantly enhance the emission rate. The presented process allows for the fabrication of fully suspended devices with a total length of 20.5 μm and feature sizes as small as 40 nm. The optical characterization shows fundamental mode resonances that follow the behavior expected from the corresponding design parameters and quality (Q) factors as high as (3800 ± 1200). Finally, we investigate the effects of nanofabrication on the devices and show that, despite a noticeable erosion of the fine features, the measured cavity resonances deviate by only 0.8 (1.2)% from the values estimated by simple inspection via scanning electron microscopy. This proves that the Sawfish design is robust against fabrication imperfections, which makes it an attractive choice for the development of quantum photonic networks. [ABSTRACT FROM AUTHOR]

We demonstrate the fabrication of photonic crystal nanobeam cavities with rectangular cross section into bulk diamond. In simulation, these cavities have an unloaded quality (Q) factor of over 1×106. Measured cavity resonances show fundamental modes with spectrometer-limited Q factors ⩾14 × 103 within 1 nm of the nitrogen vacancy centers zero phonon line at 637 nm. We find high cavity yield across the full diamond chip with deterministic resonance trends across the fabricated parameter sweeps. [ABSTRACT FROM AUTHOR]

We demonstrate an infrared spectrometer based on waveguide-coupled nanocavity filters in a planar photonic crystal structure. The input light is coupled into the waveguide, from which spectral components are dropped into the cavities and radiated off-chip for detection on a commercial InGaAs camera. The spectrometer has a footprint of only 60 µm by 8 µm. The spectral resolution is about 1 nm in the operation bandwidth of 1522-1545 nm. By substituting the membrane material and structure parameters, this design can be easily extended into the visible regime and developed for a variety of highly efficient, miniature photonic applications. [ABSTRACT FROM AUTHOR]