Spectral response of vibrational polaritons in an optomechanical cavity.

Vibrational strong coupling provides a convenient way to modify the energy of molecular vibrations and to explore the control of chemical reactivity. In this work, we theoretically report the various vibrational anharmonicities that modulate the dynamics of optomechanically coupled W(CO)6-cavity. The optomechanical free-space cavity consists of movable photonic crystal membrane, which creates photonic bound states to interact with the molecular vibration. This coupled system is used for realizing strong optomechanical dispersive or dissipative type coupling, which provides a platform to explore the new regimes of optomechanical interaction. The addition of different strong coupling and mechanical (nuclear) anharmonicities to the optical cavity establishes a modified splitting dynamics in the absorption spectrum and shows that the ground-state bleach of coupled W(CO)6-cavity has a broad, multisigned spectral response. This work demonstrates the possibility of systematic and predictive modification of the multimode spectroscopy of optomechanical W(CO)6-cavity polariton system.

Polariton multistability in a nonlinear optomechanical cavity.

We theoretically study the polariton multistability in a solid state based optomechanical resonator embedded with a quantum well and aχ(2)second order nonlinear medium. The excitonic transition inside the quantum well is strongly coupled to the optical cavity mode. The polariton formed due to the mixing of cavity photons and exciton states are coupled to the mechanical mode which gives rise to the bistable behavior. A transition from bistability to tristability occurs in the presence of a strongχ(2)nonlinearity. Switching between bistability and tristability can also be controlled using exciton-cavity and optomechanical coupling making the system highly tunable. Tristability appears at low input power making it a suitable candidate for polaritonic devices which requires low input power.

Measuring finite-range phase coherence in an optical lattice using Talbot interferometry.

One of the important goals of present research is to control and manipulate coherence in a broad variety of systems, such as semiconductor spintronics, biological photosynthetic systems, superconducting qubits and complex atomic networks. Over the past decades, interferometry of atoms and molecules has proven to be a powerful tool to explore coherence. Here we demonstrate a near-field interferometer based on the Talbot effect, which allows us to measure finite-range phase coherence of ultracold atoms in an optical lattice. We apply this interferometer to study the build-up of phase coherence after a quantum quench of a Bose-Einstein condensate residing in a one-dimensional optical lattice. Our technique of measuring finite-range phase coherence is generic, easy to adopt and can be applied in practically all lattice experiments without further modifications.