Near-infrared single-photon spectroscopy of a whispering gallery mode   resonator using energy-resolving transition edge sensors
  We demonstrate a method to perform spectroscopy of near-infrared single photons without the need of dispersive elements. This method is based on a photon energy resolving transition edge sensor and is applied for the characterization of widely wavelength tunable narrow-band single photons emitted from a crystalline whispering gallery mode resonator. We measure the emission wavelength of the generated signal and idler photons with an uncertainty of up to 2 nm. 
Michael F\"ortsch, Thomas Gerrits, Martin J. Stevens, Dmitry   Strekalov, Gerhard Schunk, Josef U. F\"urst, Ulrich Vogl, Flo...
quant-ph physics.optics