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A Molecule-Based Single-Photon Source Applied in Quantum Radiometry


Single‐photon sources (SPSs) based on quantum emitters hold promise in quantum radiometry as metrology standard for photon fluxes at the low light level. Ideally this requires control over the photon flux in a wide dynamic range, sub‐Poissonian photon statistics, and narrow‐band emission spectrum. In this work, a monochromatic SPS based on an organic dye molecule is presented, whose photon flux is traceably measured to be adjustable between 144 000 and 1320 000 photons per second at a wavelength of (785.6 ± 0.1) nm, corresponding to an optical radiant flux between 36.5 and 334 fW. The high purity of the single‐photon stream is verified, with a second‐order autocorrelation function at zero time delay below 0.1 throughout the whole range. Such molecule‐based SPS is hence used for the calibration of a single‐photon avalanche detector against a low‐noise analog photodiode traceable to the primary standard for optical radiant flux (i.e., the cryogenic radiometer). Due to the narrow bandwidth of the source, corrections to the detector efficiency arising from the spectral power distribution are negligible. With this major advantage, the developed device may finally realize a low‐photon‐flux standard source for quantum radiometry.


Metrological characterization of the molecule emission: a) Fluorescence spectrum, inset: fluorescence spectrum when filters are set to select a 2 nm wide spectral window around the molecule 00‐ZPL (785.6 nm in this case). b) Photon flux detected with the SPAD as a function of the laser pump power. c) Normalized histogram of the inter‐photon arrival times for maximum photon flux operation (30 µW pump power). d) Zoom on the histogram in (c) around zero time delay, representing g(2)(t): the anti‐bunching behavior shows the high purity of the single‐photon stream. The red lines are a fit to the data with the expression shown in (c), while best estimation of the fit parameters is reported in (d).


Dr. P. Lombardi, Dr. C. Toninelli Istituto Nazionale di Ottica (CNR-INO) via N. Carrara 1, Sesto Fiorentino 50019, Florence, Italy E-mail: toninelli@lens.unifi.it
M. Trapuzzano Università degli Studi di Firenze via G. Sansone 1, Sesto Fiorentino 50019, Florence, Italy
M. Colautti LENS, Università degli Studi di Firenze via N. Carrara 1, Sesto Fiorentino 50019, Florence, Italy
Dr. G. Margheri Istituto dei Sistemi Complessi (CNR-ISC) via Madonna del Piano 10, Sesto Fiorentino 50019, Florence, Italy
Dr. M. López, Dr. S. Kück Physikalisch-Technische Bundesanstalt (PTB) Bundesallee 100, 38116 Braunschweig, Germany
Dr. I. P. Degiovanni Istituto Nazionale di Ricerca Metrologica (INRiM) Strada delle Caccie 91, 10135 Torino, Italy