Abstract
The traceability of measurements of the parameters characterizing single-photon sources, such as photon flux and optical power, paves the way towards their reliable comparison and quantitative evaluation. In this paper, we present an absolute measurement of the optical power of a single-photon source based on an InGaAs quantum dot under pulsed excitation with a calibrated single-photon avalanche diode (SPAD) detector. For this purpose, a single excitonic line of the quantum dot emission with a bandwidth below 0.1 nm was spectrally filtered by using two tilted interference filters. Since high count rates are essential for many metrological applications, we optimized the setup efficiency by combining high overall transmission of the optical components with a geometrical enhancement of the extraction efficiency of a single quantum dot by a monolithic microlens to reach photon fluxes up to photons per second at the SPADs. A relative calibration of two SPAD detectors with a relative standard uncertainty of 0.7% was carried out and verified by the standard calibration method using an attenuated laser. Finally, an Allan deviation analysis was performed giving an optimal averaging time of 92 s for the photon flux.
Highlights
We present an absolute measurement of the optical power of a single-photon source based on an InGaAs quantum dot under pulsed excitation with a calibrated single-photon avalanche diode (SPAD) detector
Since high count rates are essential for many metrological applications, we optimized the setup efficiency by combining high overall transmission of the optical components with a geometrical enhancement of the extraction efficiency of a single quantum dot by a monolithic microlens to reach photon fluxes up to 3.7 · 105 photons per second at the SPADs
The identity principle guarantees universality and reproducibility of the observed quantum phenomena, whereas the existence of discrete energy states opens the possibility of reaching high resolution in energy [2]
Summary
The first direct detection efficiency calibration of a SPAD detector at a specific wavelength was achieved by using a single organic dye molecule as a light source with a tunable optical radiant flux in the range from 36.5 fW to 334 fW, measured with an analog reference low-noise detector, and a g(2)(0)value below 0.1 [13]. The exciton recombination lines of InGaAs QDs under non-resonant excitation have typical linewidths of less than 100 μeV [15, 16] (corresponding to 70 pm at 930 nm) and even reach the Fourier transform limited homogenous linewidth under resonant excitation [17], and fulfill the condition of nearly monochromatic radiation Their mechanical robustness and conformity with other semiconductor devices, enabling on-chip operation, give them an important advantage over molecule- and nanoparticle-based sources. InGaAs QDs are an important platform for the field of quantum key distribution [18] and allow for the generation of polarization-entangled photons via the biexciton-exciton radiative cascade [19]
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