Quantum Optical Effects In Cavity Optomechanical Systems

In the past several decades, the coupling between optical and mechanical degrees of freedom has been subjected to increasing investigation. Cavity optomechanical system composed of a driven high-frequency optical cavity and a high-Q, low frequency mechanical resonator has also attracted a lot of attention from both technical and scientific communities in physics. Meanwhile, slow and fast light, third order nonlinear effect and such optical effects have many potential applications in the areas of quantum communication, all-optical switch, information transmission and so on. In this thesis, we study the quantum optical properties of a typical cavity optomechanical system. By solving the Heisenberg equation of motion, we derived the first order and the third order susceptibility of the system.(1) We analyze the absorption spectrum, and demonstrate the existence of Normal-Mode-Splitting (NMS) effect. Noticing that the distance between splitting peaks is in direct proportion to the coupling rate of the optical cavity and the mechanical resonator, we propose a precise way to measure the coupling strength based on radiation pressure induced NMS. Simultaneously the vibrational frequency of the mechanical mode can also be detected easily in the reflected probe spectrum.(2) Next, we turn our attention to the dispersion property of the cavity optomechanical system. Considering that the dispersion curve is very steep when NMS occurs, we calculate the group velocity of the signal light. The results show that a fast or slow light process occurs under different values of cavity-pump detuning. At the same time, due to the NMS effect, the signal light can pass through the cavity with little absorption. Thus, it is possible to control the group velocity via an cavity optomechanical system. (3) Further, we study the Kerr nonlinear effect of the system. From the analytical expression of third order susceptibility, we find that the Kerr coefficient is related to the power of pump field: when the pump field turns off, no Kerr effect is generated; when the pump field turns on, the Kerr coefficient increases with the increase of the power of pump field, and it becomes saturate quickly. Based on this property, an all-optical Kerr switch can be realized in the cavity optomechanical system.(4) Finally, we calculate the group velocity of signal light again by using density matrix. The results show that the group velocity is related to the number of photons inside the cavity, and meanwhile the number of photons is related to the power of pump field. Hence, we demonstrate that it is possible to control the group velocity of light pulses via an cavity optomechanical system again.In last chapter, the main contents and conclusion of my dissertation have been summarized. Since the structure of such systems is not complicated, many laboratories have already successfully fabricated the cavity optomechanical system. We believe our results are valuable for further researches.