  We demonstrate a single-photon sensitive spectrometer in the visible range,
which allows us to perform time-resolved and multi-photon spectral correlation
measurements. It is based on a monochromator composed of two gratings,
collimation optics and an array of single photon avalanche diodes. The time
resolution can reach $110$ ps and the spectral resolution is $2$ nm/pixel,
limited by the design of the monochromator. This technique can easily be
combined with commercial monochromators, and can be useful for joint spectrum
measurements of two photons emitted in the process of parametric down
conversion, as well as time-resolved spectrum measurements in optical coherence
tomography or medical physics applications.
