Measuring intensity correlations of a THz quantum cascade laser around   its threshold at sub-cycle timescales
  The quantum nature of photonic systems is reflected in the photon statistics of the light they emit. Therefore, the development of quantum optics tools with single photon sensitivity and excellent temporal resolution is paramount to the development of exotic sources, and is particularly challenging in the THz range where photon energies approach kbT at T=300 K. Here, we report on the first room temperature measurement of field g1({\tau}) and intensity correlations g2({\tau}) in the THz range with sub-cycle temporal resolution (146 fs) over the bandwidth 0.3-3 THz, based on electro-optic sampling. With this system, we are able to measure the photon statistics at threshold of a THz Quantum Cascade Laser. 
Ileana Cristina Benea Chelmus, Christopher Bonzon, Curdin Maissen,   Giacomo Scalari, Mattias Beck, and Jerome Faist
physics.optics