Generation of two-color polarization-entangled optical beams with a self-phase-locked two-crystal optical parametric oscillator

Abstract

A device to generate polarization-entangled light in the continuous-variable regime is introduced. It consists of an optical parametric oscillator with two type-II phase-matched nonlinear crystals orthogonally oriented, associated with birefringent elements for adjustable linear coupling. We give in this paper a theoretical study of its classical and quantum properties. It is shown that two optical beams with adjustable frequencies and well-defined polarization can be emitted. The Stokes parameters of the two beams are entangled. The principal advantage of this setup is the possibility to directly generate polarization-entangled light without the need of mixing four modes on beamsplitters as required in current experimental setups. This device opens up different directions for the study of light-matter interfaces and a generation of multimode nonclassical light and higher dimensional phase space.