Pump photons present in a non-linear process as a witnesses of non-classicality of a system

We have studied non-classical effects, i.e. higher order photon antibunching (HOA) and higher order sub-Poissonian photon number statistics (HOSPS) in various non-linear optical processes like second harmonic generation, fourth harmonic generation, coherent anti-Stokes Raman scattering (CARS) and coherent anti-Stokes hyper-Raman scattering (CAHRS) using short time interaction techniques. The non-classical effects directly depend on number of photons prior to interaction with non-linear medium has already been studied but we have found that non-linear processes involving equal number of pump photons have same higher order photo antibunching (HOA) and higher order sub-Poissonian photon number statistics (HOSPS) independent of the non-linear process involved.