Abstract-Spontaneous parametric down-conversion of photons at 660 nm to the terahertz and sub-terahertz frequency range

Björn Haase, Mirco Kutas, Felix Riexinger, Patricia Bickert, Andreas Keil, Daniel Molter, Michael Bortz, and Georg von Freymannark

Fig. 1 Phase-matching schemes. The periodic poling of the nonlinear crystal leads to a k-vector component kΛ, which can have two directions. This yields phase-matched terahertz generation in forward and backward direction. Pump (p), signal (s) and idler (THz) wave vectors have to be considered as non-collinear in down- (sd) and up-conversion (su).

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-27-5-7458

We report on spontaneous parametric down-conversion (SPDC) in periodically poled lithium niobate (PPLN) using 660 nm pump wavelength and the type 0 phase-matching condition to the terahertz and even sub-terahertz frequency range. Detection of the frequency-shifted signal photons is achieved by using highly efficient and narrowband volume Bragg gratings and an uncooled sCMOS camera. The acquired frequency-angular spectrum shows backward and forward generation of terahertz and sub-terahertz photons by SPDC, as well as up-conversion and higher order quasi phase-matching (QPM). The frequency-angular spectrum is theoretically calculated using a Monte-Carlo integration scheme showing a high agreement with the measurement. This work is one important step toward quantum sensing and imaging in the terahertz and sub-terahertz frequency range.

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