Study on heterodyne detection efficiency of partially coherent beams with different polarization state combinations in atmospheric turbulence

Abstract

Expressions for the heterodyne detection efficiency of the partially coherent electromagnetic Gaussian–Schell model (EGSM) in atmospheric turbulence were derived. In this study, the signal and local oscillator beams were configured in five different polarization states: linear (LP), left/right-handed circular (LHCP/RHCP), and left/right-handed elliptical (LHEP/RHEP). The results show that as the spatial coherence length increases, the detection efficiency rises rapidly before gradually saturating. A dynamic “critical spatial coherence length” exists, which varies with propagation distance. Furthermore, the detection efficiency decreases with increasing zenith angle, turbulence intensity, and detector aperture. The influence of inner turbulence scale is significant, while that of the outer turbulence scale is negligible. Finally, the partially coherent heterodyne detection experimental system we constructed revealed that, although polarization matching is most efficient under perfectly matched conditions, the relative attenuation of circular and elliptical polarization is relatively small under turbulent conditions.