Transparency and tunable slow and fast light in a nonlinear optomechanical cavity

Controllable four-wave mixing in an atom–optical cavity coupling system with a second-order nonlinear crystal

The four-wave mixing (FWM) effect has been systematically studied in an atom–optical cavity coupling system with a second-order nonlinear crystal (SOC), which is formed by coupling an optical cavity with a two-level atom and a SOC. In this research, it is found that the FWM effect largely depends on the SOC, because the SOC can promote a two-photon absorption process. Therefore, a tunable FWM signal can be obtained in this coupling system by controlling the SOC. Moreover, the results also show that the cavity decay rate plays an important role in controlling the FWM signal. By optimizing the cavity decay rate and the SOC, a strong FWM signal can be generated. In addition, by adjusting the cavity–pump detuning, conversion between a single-peak FWM signal and two-peak FWM signal can be easily realized.

Enhanced nonlinear characteristics with the assistance of a [Formula: see text]-symmetric trimer system

We study the parity-time (PT) symmetry characteristics and the applications to nonlinear optics in an optical trimer system consisting of two indirectly coupled standing-mode micro-cavities and a two-level quantum emitter (QE) placed at the intersection of two cavities. We find this trimer system can exhibit analogical phenomena as those in typical [Formula: see text]-symmetric dimer systems composed of a passive cavity directly coupled to an active cavity. This system, whose [Formula: see text] symmetry is demonstrated by our analytic results, can be transformed between the [Formula: see text]-symmetric phase and the [Formula: see text]-broken phase by adjusting relevant system parameters. Then, with this system, we observe both the linear and nonlinear parts of the transmission field become remarkably enhanced and can further reach peak values around the [Formula: see text] breaking point. In addition, we show the negative correlation between the gain degree of the linear (nonlinear) transmission part and decay rate of the QE. This trimer proposal is feasible for experiments and may provide a promising platform for [Formula: see text]-symmetric optics of low-light levels. Moreover, novel phenomena arising from the QE-cavity-coupling induced nonlinearity gain could be explored to fabricate photonic devices and controllable nonlinear optical media for quantum information process and communication of photons.