Quantum statistics and dynamics of nonlinear couplers with nonlinear exchange

TL;DR

This paper investigates the quantum statistical and dynamical behavior of nonlinear optical couplers with nonlinear exchange, focusing on nonclassical light generation, squeezing, and correlations, depending on initial states and coupling strengths.

Contribution

It introduces a detailed analysis of nonlinear couplers with nonlinear exchange, highlighting their ability to generate squeezed and nonclassical light from various initial states.

Findings

Fock state input can produce squeezed vacuum states.

Thermal input leads to generation of squeezed thermal light.

Coupler parameters control nonclassical light properties.

Abstract

In this paper we derive the quantum statistical and dynamical properties of nonlinear optical couplers composed of two nonlinear waveguides operating by the second subharmonic generation, which are coupled linearly through evanescent waves and nonlinearly through nondegenerate optical parametric interaction. Main attention is paid to generation and transmission of nonclassical light, based on a discussion of squeezing phenomenon, normalized second-order correlation function, and quasiprobability distribution functions. Initially coherent, number and thermal states of optical beams are considered. In particular, results are discussed in dependence on the strength of the nonlinear coupling relatively to the linear coupling. We show that if the Fock state $|1>$ enters the first waveguide and the vacuum state $|0>$ enters the second waveguide, the coupler can serve as a generator of squeezed vacuum state governed by the coupler parameters. Further, if thermal fields enter initially the waveguides the coupler plays similar role as a microwave Josephson-junction parametric amplifier to generate squeezed thermal light.