Spectrally-resolved higher-order photon statistics of spontaneous parametric down-conversion

The photon statistics of spontaneous parametric down-conversion (SPDC) exhibit dependencies on wavelength, pump power, and coincidence time. Notably, the average photon numbers were found to asymmetrically increase with increasing pump power around the degenerate wavelength of emission. We employ a four-detector Hanbury Brown and Twiss interferometer to study the photon statistics of the signal beam. Coupling the detection scheme to a spectrometer enabled the dynamic probing of different bandwidths within the broadband emission. Spectrally resolving the photon statistics revealed that shorter wavelengths increased nonlinearly with pump power, while longer wavelengths showed more linear behavior, indicating a wavelength-dependent efficiency in the generation of the SPDC. The detection and characterization of complex light sources has wide ranging applications in the fields of quantum metrology, quantum communications, and quantum computing, more specifically, a system that is sensitive to wavelength and photon number distribution.