We theoretically investigate a second-order optomechanically induced transparency process of a cigar-shaped dual-species Bose–Einstein condensate with nonlinear collisions trapped inside an optomechanical cavity. We find that atomic collisions provide linear couplings, which facilitate the mechanical mixing of the dual-species Bose–Einstein condensate. We derive analytical expressions of the output transmission intensity of the probe field and the dimensionless amplitude of the second-order sideband. The numerical results show that the transmission intensity and the dimensionless amplitude of the second-order sideband can be controlled by the control field intensities, the effective detuning, and the effective coupling strength of the Bogoliubov mode of the dual-species Bose–Einstein condensate and optical mode. Furthermore, the interspecies and intraspecies interactions are also used to control the transmission intensity and the dimensionless amplitude of the second-order sideband.
We study the response of parity-time (PT)-symmetric optomechanical systems with tunable gain and loss to the weak probe field in the presence of a strong control field and a coherent phonon pump. We show that the probe transmission can exceed unity at low control power due to the optical gain of the cavity and it can be further enhanced or suppressed by tuning the amplitude and phase of the phonon pump. Furthermore, the phase dispersion of the transmitted probe field is modified by controlling the applied fields, which allows one to tune the group delay of the probe field. Based on this optomechianical system, we can realize a tunable switch between slow and fast light effect by adjusting the gain-to-loss ratio, power of the control field as well as the amplitude and phase of the phonon pump. Our work provides a platform to control the light propagation in a more flexible way.
We propose and analyze an effective scheme to enhance the optical higher-order sideband generation in a three-cavity array with local parity-time (
PT) symmetry. In this three-cavity configuration, a single cavity containing a quantum dot (QD) is coupled to an assisted
PT-symmetric combination of two cavities. Beyond the weak-excitation approximation, we derive the analytic formulas used to determine the nonlinear coefficient of the optical second-order sideband (OSS) by employing the perturbation technique. Using experimentally achievable parameters, we identify the conditions under which the assisted
PT-symmetric double-cavity system allows us to modify the transmission of the probe field and improve the efficiency of OSS generation beyond what is achievable in a loss-only QD-cavity system. We examine the influence of the
PT phase transition from unbroken- to broken-
PT regimes on the OSS generation. It is found that the efficiency of optical second-order sideband generation can be significantly enhanced when the assisted double-cavity system is in
PT-symmetric phase, extremely in the vicinity of the transition point. The present results illustrate the potential to utilize
PT-symmetric physical systems for enhancing optical higher-order sidebands and controlling optical frequency combs, as well as to guide the design of experimental implementation.