Precise Characterization of a Waveguide Fiber Interface in Silicon Carbide

Abstract

Spin-active optical emitters in silicon carbide are excellent candidates toward the development of scalable quantum technologies. However, efficient photon collection is challenged by undirected emission patterns from optical dipoles, as well as low total internal reflection angles due to the high refractive index of silicon carbide. Based on recent advances with emitters in silicon carbide waveguides, we now demonstrate a comprehensive study of nanophotonic waveguide-to-fiber interfaces in silicon carbide. We find that across a large range of fabrication parameters, our experimental collection efficiencies remain above 90%. Further, by integrating silicon vacancy color centers into these waveguides, we demonstrate an overall photon count rate of 181 kilo-counts per second, which is an order of magnitude higher compared to standard setups. We also quantify the shift of the ground state spin states due to strain fields, which can be introduced by waveguide fabrication techniques. Finally, we show coherent electron spin manipulation with waveguide-integrated emitters with state-of-the-art coherence times of T 2 ∼ 42 μs. The robustness of our methods is very promising for quantum networks based on multiple orchestrated emitters.

Fluorescence Enhancement of Single V2 Centers in a 4H-SiC Cavity Antenna

“…Figure (c) and 2­(d) shows the results of these measurements on an exemplary V2 center in our structure. We find an ODMR contrast of 2.5 ± 0.4%, which is a typical value for the V2 center at room temperature ,,, and an antibunching of g (2) (τ = τ 0 ) = 0.38 ± 0.01, significantly below 0.5 at zero time delay, without background correction, confirming that we are investigating a single V2-center. We note that the typically observed single ODMR peak for the V2-center without an applied magnetic field is split by 11 MHz into two peaks in our case.…”

“…This enables implementing various photonic structures that improve the rate of collected photons from emitters through their geometry, e.g. solid-immersion lenses (SIL), , nanopillars, and waveguides. , It also allows for the fabrication of more complex structures, such as photonic crystal cavities , or disk resonators, , that can further boost the photon rate through Purcell enhancement. While nanophotonic cavities offer the highest enhancement among the above-mentioned structures, they rely on complicated fabrication processes, tight restrictions on the emitter placement, and complex methods to keep the emitter on resonance with the structure.…”