Characterization of single photon sources for radiometry applications at room temperature

TL;DR

This study characterizes single photon emitters at room temperature, analyzing photon number fluctuations and stability across different materials for radiometry, revealing material-dependent relaxation effects and demonstrating repeatable flux measurements.

Contribution

It provides a comparative analysis of photon stability in various single photon emitters and demonstrates reliable radiant flux measurements over a wide range at room temperature.

Findings

GaN defects show high photon stability due to faster relaxation times.

Vacancies in hBN produce higher photon rates but less stability.

Repeatable flux measurements achieved from femtowatts to picowatts.

Abstract

A single photon source with high repeatability and low uncertainties is the key element for few-photon metrology based on photon numbers. While low photon number fluctuations and high repeatability are important figures for qualification as a standard light source, these characteristics are limited in single photon emitters by some malicious phenomena like blinking or internal relaxations to varying degrees in different materials. This study seeks to characterize photon number fluctuations and repeatability for radiometry applications at room temperature. For generality in this study, we collected photon statistics data with various single photon emitters of $g^{(2)}(0) < 1$ at low excitation power and room temperature in three material platforms: silicon vacancy in diamond, defects in GaN, and vacancy in hBN. We found common factors related with the relaxation times of the internal states that indirectly affect photon number stability. We observed a high stability of photon number with defects in GaN due to faster relaxations compared with vacancies in hBN, which on the other hand produced high rates ($> 10^6$) of photons per second. Finally, we demonstrate repeatable radiant flux measurements of a bright hBN single photon emitter for a wide radiant flux range from a few tens of femtowatts to one picowatt.