三机械薄膜腔光力系统相互作用的研究

本文主要研究了利用传输矩阵理论和共振透射条件详细地推导光腔中均匀放置三个机械薄膜构成的腔光力系统中系统本征模式随机械运动的色散关系.计算结果发现系统的光学本征模式由一组四个的本征能级构成,且不同的能级随不同的机械运动模式的变化曲线各不相同,进而导致不同光学模式与不同机械运动模式之间的耦合也不相同.此外,利用微扰理论求解了当机械运动振幅远小于腔模波长、机械振子处于平衡位置附近时,各种光学模式与不同机械振动模式间相互作用耦合强度的解析表达式.研究结果能够为理论和实验上研究多模腔光力系统提供一定的参考.

Optomechanical interaction with triple membranes

Cavity optomechanics becomes a promising field in quantum and nano technologies. Motivated by the optomechancial experiment with the membrane located in a high-finesse optical cavity and theoretical treatment on two membranes cavity optomechanics, we here study the optomechanical interaction of the system consisting of triple membranes within an optical cavity. The increase of membranes will increase the normal modes of the cavity and mechanical fields, and thus enrich the forms of optomechanical interaction. Firstly, we use the transfer matrix and resonance transmission methods to obtain the dispersion relation between the eigen-frequencies of the optical modes and the mechanical motions. Owing to the existence of triple mechanical membranes, the system possesses different forms of collective mechanical motion, and here we focus on the center-of-mass (COM) motion and relative motion of the equally placed membranes. The numerical solutions of the dispersion relation show that the optical eigenmodes are comprised of a group of closely spaced avoided-crossing quaternion of wave numbers, which arise from the transmission and reflection of the optical field at the membranes and the tunneling couplings between subcavity modes. Moreover, the change of each eigen wave number along each form of the mechanical motion is different, which implies the different forms of optomechanical coupling between eigenmodes and mechanical motions. Then, to achieve the explicit expressions of the optomechanical coupling, it is sufficient to use the perturbation method under the equilibrium condition of the system, where the amplitude of mechanical motion is much smaller than the optical wavelength. With using the implicit function differentiation theorem, the optomechanical coupling strengths between the four optical modes and the COM and relative mechanical motions are obtained respectively. We find that the strong quadratic optomechanical coupling between the optical modes and COM motion can be achieved, and the linear and quadratic couplings between the optical modes and relative motion can both be realized. By tuning the laser to pump different optical modes, we can choose either the linear or the quadratic coupling to the relative motion. Our method is universal to multi-membrane system, and the results may provide some references to theoretical and experimental investigations on the multi-membrane cavity optomechanics.