Incoherent Light and Second-order correlation

Hui Chen, Tao Peng, Sanjit Karmakar +2 more

We wish to report a recent experimental observation of anticorrelation from first-order and second-order incoherent thermal fields in the joint photodetection of two independent photodetectors. In the view of classical theory, the nontrivial second-order correlation of thermal light is caused by the statistical correlation of intensity fluctuations, which can be observed only from first-order coherent thermal radiations. What is the physical cause of this observed anticorrelation, then?

Bjarne Vestergaard, Klaus Mølmer

Carlos R. Fernández‐Pousa, Juan P. Torres

The second-order correlation function of incoherent light, which is usually measured in the time domain, can be alternatively measured in the frequency domain. Here, we use an all-optical technique in a highly nonlinear fiber for measuring the full spectrum of the fluctuations of the photocurrent (rf spectrum) generated by broadband radiation with different spectral coherence properties. Our experiments reveal that the rf spectrum of a light signal depends strongly on its spectral coherence properties. From a practical perspective, this ultrafast technique constitutes an alternative for measuring the intensity correlations of spectrally incoherent radiation.

Jan Peřina

Jan Peřina

Vladislav Yu. Shishkov, E. S. Andrianov, Alexander Pukhov +1 more

It is known that spontaneous Raman scattering is accompanied by the appearance of nonclassical cross correlations of photons at Stokes and anti-Stokes frequencies. Such correlations occur due to the internal nonlinear interaction between electronic and nuclear vibration degrees of freedom. Since the properties of a given media are unchangeable, the possibilities for controlling the cross correlations are limited. This, in turn, restricts the possible applications of the correlated light obtained during the spontaneous Raman scattering. In this work, we investigate the influence of statistical properties of an incident light on the cross correlations of Stokes and anti-Stokes light. We show that the incoherence of the incident light results not only in the incoherence of the scattered light but also in the enhancement of the interbeam coherence at different frequencies. We demonstrate that the cross correlations of Stokes and anti-Stokes light intensities are enhanced when the incident light with high second-order autocorrelation function is applied. Our results pave the way to control correlated light obtained in the process of spontaneous Raman scattering.