Bullseye cavities for large optical enhancement from ultraviolet to near-infrared wavelengths

Abstract Optical cavities that provide radiative enhancement and efficient photon collection across a broad spectrum are essential for classical and quantum photonic applications. Many platforms to date have been restricted to the near-infrared (NIR) to telecom spectrum with limited cavity enhancement in the ultraviolet (UV) to NIR wavelength range. Here, we develop a silicon nitride ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:msub> <mml:mi>Si</mml:mi> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mi mathvariant="normal">N</mml:mi> <mml:mrow> <mml:mn>4</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:mrow> </mml:math> ) bullseye cavity platform optimized for maximal optical enhancement at UV and NIR wavelengths. By utilizing a distributed Bragg reflector designed to satisfy the first- and second-order Bragg conditions, the cavity contains guided modes at NIR and UV wavelengths, respectively. We employ finite-difference time-domain simulations to explore the full device parameter space in which our structure can be optimized for off-chip collection efficiencies exceeding 90% or Purcell factors greater than 50. Additionally, we use these two metrics to perform a global optimization where we can achieve simulated optical enhancements greater than 30 for resonances around 425 nm and 835 nm, the highest values reported to date of any optical cavity designs operating below the telecom O-band. We provide an experimental demonstration that includes a CMOS-compatible fabrication process and reflectometry measurements to characterize the cavity resonances. This platform provides a foundation for strong cavity enhancement and efficient off-chip extraction of a wide range of single-photon emitters spanning UV and NIR wavelengths.