Broadband Squeezed States in Two-Octave Single-Mode Multichannel Waveguide Systems

This study investigates the properties of broadband squeezed states in a two-octave system comprising single-mode nonlinear waveguides with second-order nonlinearity. By examining various input state configurations, the study investigates squeezing features across the first, second, and fourth harmonic generations using semi-analytically phase space representation. In the first octave, all channels exhibit stable squeezing at the fundamental frequency, particularly when initialized in coherent states. The second-octave channels show robust squeezing at the second harmonic, with the central channel demonstrating optimal performance. Higher harmonic frequencies reveal that higher initial states in the first octave amplify squeezing, emphasizing the cumulative effect of nonlinear interactions. These findings highlight the importance of input state configuration and coupling conditions in optimizing squeezing performance and may provide valuable insights for advancements in quantum optics applications.