Quantum Nanophotonic Interface for Tin-Vacancy Centers in Thin-Film Diamond
The negatively charged tin-vacancy center in diamond (SnV$^-$) is an excellent solid state qubit with optically-addressable transitions and a long electron spin coherence time at elevated ($\sim1.7$ K). However, implementing scalable quantum nodes with high-fidelity optical readout of the electron spin state requires efficient photon emission and collection from the system. In this manuscript, we report a quantum photonic interface for SnV$^-$ centers based on one-dimensional photonic crystal cavities fabricated in diamond thin films. Furthermore, we provide a rigorous description of the spontaneous emission dynamics of our system, taking into account individual contributions from both the C and D transitions of the emitter. This allows for determination of Purcell factors per transition and, by extension, the C/D branching ratio SnV$^{-}$ zero phonon line. We observe quality factors up to $\sim$6000 across this sample, and measure up to a 12-fold lifetime reduction, which translates into a Purcell factor of $F_C=26.2\pm1.5$ for a targeted C transition. By considering the cavity mode polarization alignment with the C and D transition dipole moments, we validate the C/D branching ratio to be $η_{\text{BR}}=0.75\pm0.01$, in line with previous theoretical and experimental findings.