Toward the Realization of Single-Photon Sources for Radiometry Applications at Room Temperature

Single-photon sources based on single emitters, such as 2-D materials and impurities in diamond, are of great interest for many application fields, including quantum communication, quantum metrology, and quantum sensing. In photometry and radiometry, a single-photon source, having the ability to emit only one photon in a well-defined time and frequency domain, represents a promising candidate to realize a photon number-based primary standard for quantum radiometry. At the Korea Research Institute of Standards and Science (KRISS), we have realized three kinds of single-photon sources based on various single emitters at room temperature: silicon vacancy (SiV) in diamond, defects in gallium nitride (GaN), and vacancy in hexagonal boron nitride (hBN). We found common factors related to the relaxation times of the internal states that indirectly affect the photon number stability. We observed a high photon number stability in the GaN emitter due to faster relaxation times compared with the hBN emitter, which, on the other hand, produced high rates of photons per second (>10 ⁶ ). Moreover, 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.