Single photon detectors are a crucial tools in many quantum technology implementations and observational techniques at the lowest light levels, like fluorescence observations in biological samples. A high temporal resolution is important in many of these applications, and affects the statements one can infer from any optical observation made with such detctors. The temporal response of single-photon detectors is usually obtained by measuring their impulse response to short-pulsed laser sources.  In this work, we present an alternative approach using time-correlated photon pairs generated in spontaneous parametric down-conversion (SPDC) which allows, in principle, to access a wider wavelength range by a simpler technique in comparison with femtosecond laser usage. We demonstrate this by comparing a few common single photon detectors at a number of relevant wavelengths.

Optics Express reaches out to the wide audience that uses these single photon detectors, and therefore looked like an adequate platform for this work.