Sub-2 Kelvin characterization of nitrogen-vacancy centers in silicon carbide nanopillars

TL;DR

This paper demonstrates sub-2 Kelvin characterization of nitrogen-vacancy centers in silicon carbide nanopillars, achieving enhanced photon collection and detailed emitter lifetime measurements at cryogenic temperatures.

Contribution

It introduces the ICECAP system integrating superconducting detectors for cryogenic NV center analysis, revealing improved emission collection and orientation-dependent properties.

Findings

No significant linewidth broadening at sub-2 K

Up to 14-fold increase in photon collection efficiency

Cryogenic emitter lifetimes of 2.2 ns and 2.8 ns for different orientations

Abstract

The development of efficient quantum communication technologies depends on the innovation in multiple layers of its implementation, a challenge we address from the fundamental properties of the physical system at the nano-scale to the instrumentation level at the macro-scale. We select a promising near infrared quantum emitter, the nitrogen-vacancy (NV) center in 4H-SiC, and integrate it, at an ensemble level, with nanopillar structures that enhance photon collection efficiency into an objective lens. Moreover, changes in collection efficiency in pillars compared to bulk can serve as indicators of color center orientation in the lattice. To characterize NV center properties at the unprecedented sub-2 Kelvin temperatures, we incorporate compatible superconducting nanowire single photon detectors inside the chamber of an optical cryostat and create the ICECAP, the Integrated Cryogenic system for Emission, Collection And Photon-detection. ICECAP measurements show no significant linewidth broadening of NV ensemble emission and up to 14-fold enhancement in collected emission. With additional filtering, we measure emitter lifetimes of NV centers in a basal ($hk$) and an axial ($kk$) orientation unveiling their cryogenic values of 2.2 ns and 2.8 ns.