Photon correlation Fourier spectroscopy of a B center in hBN

TL;DR

This study uses photon correlation Fourier spectroscopy to analyze the coherence and spectral diffusion of B center emitters in hBN under non-resonant excitation, revealing linewidth broadening mechanisms and decoherence timescales.

Contribution

It provides the first detailed characterization of coherence properties and spectral diffusion of B centers in hBN under photoluminescence excitation.

Findings

Emission linewidth increases with laser power.

Spectral diffusion occurs on 10-100 microsecond timescales.

Linewidth at low power is twice the Fourier limit.

Abstract

The potential of solid-state quantum emitters for applications critically depends on several key figures of merit. One of the most important is the quantum coherence of the emitted single photons, which can be compromised by fast dephasing and spectral diffusion. In hexagonal boron nitride (hBN), blue-emitting color centers (or B centers) are seen as favorable in this regard, in the light of prior studies mainly based on resonant excitation. Yet, their coherence properties in the more accessible regime of non-resonant excitation (or photoluminescence) has not been extensively characterized. Here, we investigate the coherence and spectral diffusion of the photoluminescence from a B center in the continuous wave regime using photon correlation Fourier spectroscopy. We determine that the emission lineshape consists in a homogeneous contribution, whose linewidth increases with the laser power, and which is broadened by spectral diffusion at a timescale of 10 to 100 microseconds. At low power and short time, the emission line is only a factor ~2 above the Fourier limit, while at long times, the inhomogeneous linewidth increases up to more than a gigahertz. Our work deepens the understanding of decoherence processes of this preeminent family of quantum emitters in hBN.