Yan-Lei Zhang

Experimental realization of optomechanically induced non-reciprocity

Non-magnetic non-reciprocal transparency and amplification is experimentally achieved by optomechanics using a whispering-gallery microresonator. The idea may lead to integrated all-optical isolators or non-reciprocal phase shifters.

Brillouin-scattering-induced transparency and non-reciprocal light storage.

Stimulated Brillouin scattering is a fundamental interaction between light and travelling acoustic waves and arises primarily from electrostriction and photoelastic effects, with an interaction strength several orders of magnitude greater than that of other relevant non-linear optical processes. Here we report an experimental demonstration of Brillouin-scattering-induced transparency in a high-quality whispering-gallery-mode optical microresonantor. The triply resonant Stimulated Brillouin scattering process underlying the Brillouin-scattering-induced transparency greatly enhances the light–acoustic interaction, enabling the storage of light as a coherent, circulating acoustic wave with a lifetime up to 10 μs. Furthermore, because of the phase-matching requirement, a circulating acoustic wave can only couple to light with a given propagation direction, leading to non-reciprocal light storage and retrieval. These unique features establish a new avenue towards integrated all-optical switching with low-power consumption, optical isolators and circulators.

Detuning Enhanced Cavity Spin Squeezing

The unconditionally squeezing of the collective spin of an atomic ensemble in a laser driven optical cavity (I. D. Leroux, M. H. Schleier-Smith, and V. Vuletic, Phys. Rev. Lett 104, 073602 (2010)) is studied and analyzed theoretically. Surprisingly, we find that the largely detuned driving laser can improve the scaling of cavity squeezing from

Integrated optical circulator by stimulated Brillouin scattering induced non-reciprocal phase shift

S^{-2/5}

Reconfigurable optomechanical circulator and directional amplifier

to

Optomechanical devices based on traveling-wave microresonators

S^{-2/3}

Phonon-induced spin squeezing based on geometric phase

, where S is the total atomic spin. Moreover, we also demonstrate that the experimental imperfection of photon scattering into free space can be efficiently suppressed by detuning.

Long-distance synchronization of unidirectionally cascaded optomechanical systems.

We propose a new approach to realize all-optical circulator based on stimulated Brillouin scattering in an integrated microresonator. Stimulated Brillouin scattering is a basic interaction between photon and traveling acoustic wave resulted from electrostriction and photoelastic effects. Due to the phase-matching requirement, the circulating acoustic wave can only couple to probe light which propagating along or opposite to the pump laser direction, thus exhibits a non-reciprocal phase shift. Combined with Mach-Zehnder interferometer, the optical circulator can be realized. Though the bandwidth is relatively small because of the narrow-band nature of microresonator, this magnetic-free all-optical integrated circulator may be applied for future on-chip photonic information processing.

Two-axis spin squeezing of two-component Bose-Einstein condensates via continuous driving

Non-reciprocal devices, which allow non-reciprocal signal routing, serve as fundamental elements in photonic and microwave circuits and are crucial in both classical and quantum information processing. The radiation-pressure-induced coupling between light and mechanical motion in travelling-wave resonators has been exploited to break the Lorentz reciprocity, enabling non-reciprocal devices without magnetic materials. Here, we experimentally demonstrate a reconfigurable non-reciprocal device with alternative functions as either a circulator or a directional amplifier via optomechanically induced coherent photon–phonon conversion or gain. The demonstrated device exhibits considerable flexibility and offers exciting opportunities for combining reconfigurability, non-reciprocity and active properties in single photonic devices, which can also be generalized to microwave and acoustic circuits.Upconversion nanoparticles, which convert lower-energy light into higher-energy light, have many potential applications including sensing and imaging. Here, Wen et al. review recent advances that have addressed concentration quenching and enabled increasingly bright nanoparticles, opening up their full potential.

Phase-controlled phonon laser

We theoretically study the unique applications of optomechanics based on traveling-wave microresonators, where the optomechanical coupling of degenerate modes (clockwise and counterclockwise) can be enhanced selectively by optically pumping in different propagation directions. We show that the unique features of degenerate optical modes can be applied for the entangled photon generation. Specifically, the coherent coupling between the degenerate optical modes and two acoustic modes is also studied, in which the relative phase of the optomechanical couplings plays a key role in the optical nonreciprocal conversion. In addition, we have studied another mechanical vibration based on the Brillouin scattering in the microresonators. The parity-time symmetry of acoustic modes can be observed in the slightly deformed microresonators because of the interaction of forward and backward stimulated Brillouin scattering in the triple-resonance system. The degenerate modes are in the decoherence-free subspace, which is robust against environmental noises. Based on parameters realized in recent experiments, these optomechanical devices should be readily achievable.