Single-cycle squeezing from chirped quasi-phase-matched optical parametric down-conversion

Parametric down-conversion of light (PDC) in a quasi-phase-matched (QPM) nonlinear crystal can be spectrally very broad when the spatial frequency of periodical poling is linearly chirped. The present day technology makes possible the fabrication of chirped QPM crystals phase-matched for PDC in all optical spectrum. In the low-gain regime this allows for generation of biphotons with the correlation time of the order of a single optical cycle. A natural next step is the study of the PDC light produced by such a crystal in the high-gain regime, where PDC is widely used as a source of squeezed states of light. Up to now only a classical treatment of this regime was undertaken. In the present work we demonstrate a possibility to generate single-cycle squeezing in a chirped QPM nonlinear crystal with squeezing spectrum covering almost all the optical octave.