Deterministic Laser Writing of Spin Defects in Nanophotonic Cavities

TL;DR

This paper introduces a laser-writing technique for creating spin defects directly within nanophotonic cavities, enabling real-time defect characterization and improved control for quantum network applications.

Contribution

The authors demonstrate a novel in-situ laser-writing method for defect formation in nanophotonic cavities, eliminating the need for post-processing and enabling real-time defect-cavity coupling control.

Findings

Defects formed with laser-writing show properties similar to conventional methods.

Cavity-integrated defect spins are successfully demonstrated.

Excited-state lifetime decreases exponentially near cavity amorphization threshold.

Abstract

High-yield engineering and characterization of cavity-emitter coupling is an outstanding challenge in developing scalable quantum network nodes. Ex-situ defect formation processes prevent real-time defect-cavity characterization, and previous in-situ methods require further processing to improve emitter properties or are limited to bulk substrates. We demonstrate direct laser-writing of cavity-integrated spin defects using a nanosecond-pulsed above-bandgap laser. Photonic crystal cavities in 4H-silicon carbide serve as a nanoscope monitoring silicon monovacancy (V$_{Si}^-$) defect formation within the $100~\text{nm}^3$ cavity mode volume. We observe defect spin resonance, cavity-integrated photoluminescence and excited-state lifetimes consistent with conventional defect formation methods, without need for post-irradiation thermal annealing. We further find an exponential reduction in excited-state lifetime at fluences approaching the cavity amorphization threshold, and show single-shot local annealing of the intrinsic background defects at the V$_{Si}^-$ formation sites. This real-time in-situ method of localized defect formation, paired with demonstration of cavity-integrated defect spins, marks an important step in engineering cavity-emitter coupling for quantum networking.