Quantum squeezing in coupled waveguide networks with quadratic and qubic nonlinearity

This study demonstrates that coupled waveguide networks with quadratic and cubic nonlinearity mediated by a linear waveguide allow for the generation, enhancement and transmission of squeezed light on a single-mode and multi-mode basis. The time evolution of the density matrix could be mapped to the corresponding Fokker–Planck equation of a classical quasiprobability distribution using the positive P representation of the phase space. Using the Langevin stochastic equation, we examine the scenarios where the system functions at varied evanescent coupling profiles, coupled modes interaction, competing nonlinear response and ultimately when the second harmonic generation and self-action Kerr interaction are present or absent. We analyze the behavior of squeezing and how the evolution is affected by the presence of coupled nonlinearity. We show that the interplay of linear and nonlinear effects in coherently driven coupled waveguide networks has the potential to be a valuable source of squeezed light.