A simple technique for measuring the spatial correlation of photon pairs for complete interference in the Michelson interferometer

Abstract

In this research, a simple technique for measuring the spatial correlation or angular correlation of photon pairs was developed. The system consisted of two aluminium rails which had the same pivot at the position of a nonlinear crystal. The rails were manually moved to find the position of the correlated photon pairs. At this position, the photon pairs were collected by the collimators attached at the end of the rails. The pairs were produced by type I spontaneous parametric down-conversion process using a 405 nm diode laser and a BBO crystal. The crystal was specifically cut for emitting the photon pairs at an angle of 3° with respect to the direction of the pump laser. These pairing photons were correlated and interfered in the Michelson interferometer, then, the correlated photons were demonstrated. It was found that the visibilities in the case of perfect alignment, near perfect alignment and misalignment were V = 1.0000 ± 0.0004, 0.869 ± 0.002, 0.591 ± 0.002 and 0.168 ± 0.002, respectively.