Influence Of Nonlinear Processes On Optical Transmission In Whispering Gallery Mode Resonators

Nonlinear optical effects are fundamental methods to generate,manipulate,convert and couple light at different frequencies.The interaction between light and matters can be obviously promoted by the whispering gallery mode microresonator(WGMM),which make it an ideal platform for studying nonlinear optics.Recent studies have shown that the aluminum nitride(AIN)whispering gallery mode microresonators can contain both second-order(?²)and third-order(?³)nonlinearities due to its non-centrosymmetric property,whereas the ?²are secondorder nonlinear susceptibilities of the medium and ?³are third-order nonlinear susceptibilities of the medium.The AIN WGMMs can provide a good condition for fabricating nonlinear optical devices with high stability and high power on substrates.In previous studies,the pump-light non-depletion approximation method is mainly adopted,wherein the coupling between pump light and signal light is not taken into account,and it is usually used to study nonlinear optical manipulation and frequency conversion of the WGMMs in the low power range.However,when the system is in the strong power region,the conversion between pump light and signal light in the WGMMs must be considered.In this work,we study optical manipulation and conversion in the high-power regime,and thus the intrinsic coupling between the pump light and the signal light,i.e.,pump depletion,needs to be included.In the high-power regime with pump depletion,the resonant transmission intensities of ?²nonlinearity can be manipulated from 0 to nonzero by adjusting the intensities of the signal light,and thus it behaves as an intensity-dependent all-optical switch.Although the resonant conversion efficiencies from four-wave mixing of ?³nonlinearity are generally suppressed by power-dependent frequency shifts resulted from self-phase and crossphase modulations in the high pump regime,conversion efficiencies can be amplified by tuning frequency detunings of signal and pump lights.Optical transmission intensities and conversion efficiencies between signal light and idle light can also be enhanced by utilizing interplaying between ?²and ?³nonlinearities in the high pump regime.At the same time,dissipations in the waveguide-cavity system will destroy the interference between the incident signal light and the cavity light,and thus the transmission intensity of the signal light will be decreased with the increase of the propagation distance.Previous researches have indicated that under ?³nonlinear condition,the signal light can be amplified by the parametric amplification originated from four wave mixing(FWM),but this scheme requires watt pump light.In this paper,we further study this problem by using cascaded second-order and third-order(?²-?²??³)processes to manipulate the transmission of signal light in the WGMMs.The results show that the transmission intensity of signal light can be significantly increased with only milliwatt pump light by the cascaded second-order and third-order(?²-?²??³)nonlinearities,thus avoiding the loss of information loaded on the signal photon in the transmission process.