Absorption Properties In The Optomechanical Chain

A typical optomechanical system(OMS)is composed of a fixed mirror and a movable end mirror,in which the optical mode and the mechanical mode can be coupled by the radiation pressure.The OMS has attracted much attention due to the abundant physics,such as the optomechanically induced transparency(OMIT),optomechanically induced absorption(OMIA)and optical squeezing,etc.In this thesis,we investigate the absorption properties of an OMS chain,including OMIT,OMIA,and the slow or fast light propagation effects,using the package ompy written by ourselves.At first,we develop the package ompy to calculate the absorption properties of the OMS chain,due to its computational complexity.Ompy employ python combined with fortran,where python is used to deal with the symbolic derivation,and fortran for the numerical calculation.Starting with the standard OMS Hamiltonian and commutation relation,ompy can be used to calculate the absorption properties of OMS,employing the linearization technique for the Heisenberg-Langevin equation.We study the influence of the structure of the optomechanical chain on OMIT and OMIA in an OMS comprised of multiple cavities,in which there is only one quadratically coupled optomechnical cavity.Firstly,the effects of the position of OMS is investigated by considering a chain consisted of six cavities,where the probe field is located at the first cavity.The absorption spectra show OMIT when the OMS located at odd position,while OMIA for the even position.This phenomenon is found to be sustained in a chain with fifteen cavities.Secondly,we consider the situation where the length of the chain is changeable.The all calculated results show that the distance between the probe field and the optomechanical cavity determines whether OMIT or OMIA can be induced by the optomechanical interaction.Based on the discussion of OMIT and OMIA of the OMS chain,we study the slow or fast light propagation near the resonance point.When the length of the chain is fixed,the transmission light can be slowed down by the OMS located at the odd position,while speeded up by the OMS on the even position.Next,the situation where the length of the chain is variable is considered.When the first cavity is probed,the transmission light can be slowed down by optomechanical interaction of the first cavity and speeded up by that of the second cavity.In summary,the absorption properties of the OMS chain with arbitrary length can be investigated by ompy.These properties should be of much importance for quantum information process based on the OMS chain,both theoretically and practically.