Study of SPDC spectra to reveal temperature dependences for optical-terahertz biphotonsстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 12 августа 2020 г.
Аннотация:Frequency-angular distributions of optical signals generated via spontaneous parametric down-conversion with the Stokes idler frequency shifts 0.2-5 THz are studied simultaneously with the same distributions in the anti-Stokes range while the nonlinear Mg:LiNbO3 crystal is cooled from 300K to 4.2K. The temperature dependencies of the angular distributions at fixed idler frequencies are analyzed using a theoretical Klyshko-Kirchhoff approach with account of thermal field fluctuations and inherent crystal absorption at terahertz frequencies. Although all the measurements are performed in the optical range, we demonstrate how such analysis enables to predict the temperature behavior of the total number of SPDC-generated idler photons in the terahertz range, the temperature variation of the optical - terahertz biphoton function, and to study contributions of classical thermal and pure quantum field fluctuations to parameters of biphotons. It is shown that the temperature-induced growth of the numbers of signal and idler photons and their non-normalized correlation function is provided by overwhelming increase of classical fluctuations, while the pure quantum contributions to these parameters are not so sensitive to the crystal temperature.