Steady-State Switching and Dispersion/Absorption Spectroscopy of Multistate Atoms Inside an Optical Ring Cavity

This thesis mainly focuses on the experimental investigations of electromagnetically induced transparency (EIT) related phenomena in various systems involving multilevel atoms inside an optical ring cavity. Semiclassical methods, e.g. density-matrix equations, are used through out this thesis to simulate the experimental results. First, the cavity transmission spectrum can be significantly modified when multilevel atoms are placed inside an optical ring cavity. Such coupled atom-cavity systems are well explained by the intracavity dispersion/absorption properties. Specifically, three-level lambda-type, four-level N-type and double-lambda-type atoms inside an optical ring cavity are investigated by examining their cavity transmission spectra. Second, optical multistability (OM) has been demonstrated with EIT atoms inside an optical ring cavity. Such OM has been utilized to realize a controllable optical multistate switch, which can be modeled as a triple-well system. Third, self-Kerr nonlinearities of multilevel atoms are measured in an optical ring cavity by scanning the cavity length. Fourth, bright Stokes and anti-Stokes fields are generated simultaneously in a doubly-resonant atomic optical parametric oscillator (AOPO). In addition, vacuum-induced absorption and noise correlations are studied in the AOPO system. Last, a theoretical model is proposed to realize parity-time (PT) symmetry in a four-level N-type atomic system by spatially modifying the complex refractive index in free space. Moreover, the experimental progress is made to observe discrete diffraction pattern in an optically induced lattice by interfering with plane waves in a coherent atomic medium

Synchronous control of dual-channel all-optical multi-state switching

We have experimentally observed optical multistabilities (OMs) simultaneously on both the signal and generated Stokes fields in an optical ring cavity with a coherently-prepared multilevel atomic medium. The two observed OMs, which are governed by different physical processes, are coupled via the multilevel atomic medium and exhibit similar threshold behaviors. By modulating the cavity input (signal) field with positive or negative pulses, dual-channel all-optical multi-state switching has been realized and synchronously controlled, which can be useful for increasing communication and computation capacities

Anomalous Thermodynamic Cost of Clock Synchronization

Clock synchronization is critically important in positioning, navigation and timing systems. While its performance has been intensively studied in a wide range of disciplines, much less is known for the fundamental thermodynamics of clock synchronization, what limits the precision and how to optimize the energy cost for clock synchronization. Here, we report the first experimental investigation of two stochastic clocks synchronization, unveiling the thermodynamic relation between the entropy cost and clock synchronization in an open cavity optomechanical system. Two autonomous clocks are synchronized spontaneously by engineering the controllable photon-mediated dissipative optomechanical coupling and the disparate decay rates of hybrid modes. The measured dependence of the degree of synchronization on entropy cost exhibits an unexpected non-monotonic characteristic, indicating that the perfect clock synchronization does not cost the maximum entropy and there exists an optimum. The investigation of transient dynamics of clock synchronization exposes a trade-off between energy and time consumption. Our results reveal the fundamental relation between clock synchronization and thermodynamics, and have a great potential for precision measurements, distributed quantum networks, and biological science