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Abstract
An investigation is reported of the effects of a Kerr-down conversion nonlinear crystal inside an intrinsically nonlinear optomechanical cavity on the dynamics of the oscillating mirror, the intensity and the squeezing spectra of the transmitted field. We show that in comparison with a bare optomechanical cavity, the combination of the cavity energy shift due to the weak Kerr nonlinearity and increase in the intracavity photon number due to the nonlinear gain medium can increase the normal mode splitting in the displacement spectrum of the oscillating mirror. Our study demonstrates that at high temperatures, when the thermal fluctuations in the system are important, the optomechanical and nonlinearity-induced resonances are distinguishable in the output field spectrum. However, at low temperatures, the presence of both nonlinearities enhances the amplitude of the mechanical-mode contribution to the spectrum and leads to the occurrence of normal-mode splitting in the transmitted field spectrum even for low values of the input power. Also, at low temperatures, the Kerr-down conversion nonlinearity increases the radiation pressure contribution to the degree of squeezing of the transmitted field more than that of a bare optomechanical cavity or a nonlinear cavity (in the absence of optomechanical coupling). Furthermore, we find that for the blue-detuned laser the Kerr nonlinearity extends the domain of the stability of the system and leads to the normal-mode splitting of the movable mirror and noise reduction in the range of frequencies in which a bare cavity is not stable.
Acknowledgements
The authors would like to express their gratitude to the referee, whose valuable comments have improved the paper. They are also grateful to the office of Graduate Studies of the University of Isfahan for its support.