Two-mode difference-squeezing in CARS and CAHRS processes

In this manuscript, we studied two-mode difference-squeezing in coherent anti-Stokes Raman scattering (CARS) and coherent anti-Stokes hyper Raman scattering (CAHRS) processes. We established that for uncorrelated modes, the difference (higher-order) squeezing of the fundamental and Stokes fields can be turned into the normal squeezing of the anti-Stokes field. We showed that the second-order (amplitude-squared) squeezing and the fourth-order (amplitude fourth-power) squeezing of the fundamental (pump) mode are directly converted into the normal squeezing of the anti-Stokes mode in CARS and CAHRS processes, respectively. We investigated that the difference-squeezing responds nonlinearly to the number of pump photons and found it greater in the CAHRS process than in the CARS process. We established the concept of detection of difference-squeezing and normal squeezing in these processes. It is inferred that difference-squeezing exists only in certain domains of pump photons. We demonstrated that the multi-photon absorption approach is ideal for the generation of optimal squeezed light, which results in a larger reduction of noise in any optical system.