Tailoring the down conversion emission profile via direct imaging with a camera

TL;DR

This paper demonstrates how direct imaging with a CMOS camera can analyze and optimize the emission profile of downconverted photons, revealing how crystal thickness affects photon pair rates in different geometries.

Contribution

It introduces a method using direct camera imaging to analyze downconversion emission profiles and understand the effects of crystal thickness on photon pair rates.

Findings

Photon pair rate increases linearly with crystal thickness.

Photon pairs collected to a single mode fiber scale quadratically with crystal length.

Camera imaging simplifies phase-matching alignment processes.

Abstract

We present the analysis of emission profile of downconverted photons from a critically phase-matched nonlinear crystal. This is done via direct imaging of down converted photons by a CMOS camera. The effects of nonlinear crystal thickness in collinear and non-collinear geometries on the down converted photon pair rate is directly observed and the experimental results show that the photon pair rate increases linearly with the crystal thickness. However, the rate of the photon pairs collected to a single mode fiber goes quadratically with the crystal length because of the cylindrical asymmetries in the optical path and the exit angle around the pump mode within the nonlinear crystal. The use of cameras for real-time and direct imaging of down conversion emission profile significantly simplifies the phase-matching alignments and the collecting the entangled photons.