Electrostatically Tunable Hexagonal Boron Nitride Single Photon Emitters Integrated in Silicon Nitride Waveguide for Scalable Quantum Photonic Devices

Color centers in hexagonal boron nitride (hBN) are a promising platform for solid state single photon sources due to their brightness, purity and stability at room temperature. Further, tunability, homogenous broadening and indistinguishability have all been demonstrated for hBN color centers, representing important steps towards sources that can be effectively used in integrated quantum photonic devices. hBN can host multiple single photon emitter defects at a range of wavelengths. One defect that can be reliably reproduced with bright and stable emission has a peak emission around 580 nm, an accessible wavelength for many photonic technologies in the visible spectrum. Here we present a method for forming the 580 nm hBN emitters and integrating them into hybrid photonic devices. First, we take our initial substrate and deposit silicon nitride across the entire surface. Then, we exfoliate hBN flakes on top of the Si₃N₄ and anneal the stack to form color centers. Next, we characterize these emitters, taking note of their spatial registration and polarization angle, allowing us to design and etch Si₃N₄ waveguides underneath them with the optimal propagation direction of for dipole-mode coupling. The host hBN can be used as an initial ‘nanowaveguide’ to collect the emission directly from the single photon emitter dipole. Then, the hBN nanowaveguide can be adiabatically tapered such that the mode contained in the hBN is smoothly transformed into the Si₃N₄ alone. Full-wave simulations project up to 30% coupling in a single direction into the hBN nanowaveguide (60% when collected from both propagation directions). The hBN-based mode can then be adiabatically coupled into the Si₃N₄ fundamental mode with up to 90% coupling in simulation. We will present experimentally collected efficiencies for the single photon coupling to hBN and Si₃N₄ modes and evaluate the photon purity post-waveguide integration. Next, by fabricating and gating in-plane electrostatic contacts along the waveguide at the emitter position, we take advantage of the Stark tuning effect in these dipole-based emitters to reversibly tune the emission wavelength. This is a critical step to ensure that emitted single photons can be coupled to resonant structures through tuning, which has not been explored for waveguide integrated hBN emitters. Finally, we aim to show the evanescent coupling of these waveguide integrated single photons to resonant structures including racetrack resonators, which creates a pathway for the single photons to be leveraged for more complex on-chip quantum photonic operations.