Engineering Dispersive-Dissipative Modal Coupling in Hybrid Optical Microresonators.

Hybrid microresonators have served an intriguing platform for fundamental research and applied photonics. Here, we study the plasmonics-engineered coupling between degenerate optical whispering gallery modes, which can be tuned in a complex space featuring the dissipative strong, dispersive strong, and weak coupling regimes. Experimentally, the engineering of a single plasmonic resonance to a cavity mode family is examined in a waveguide-integrated high-Q microdisk, from which the complex coupling coefficients are extracted and agree well with theoretical predictions.

Submonolayer biolasers for ultrasensitive biomarker detection.

Biomarker detection is key to identifying health risks. However, designing sensitive and single-use biosensors for early diagnosis remains a major challenge. Here, we report submonolayer lasers on optical fibers as ultrasensitive and disposable biosensors.

Soliton Microcombs Multiplexing Using Intracavity-Stimulated Brillouin Lasers.

Solitons in microresonators have spurred intriguing nonlinear optical physics and photonic applications. Here, by combining Kerr and Brillouin nonlinearities in an over-modal microcavity, we demonstrate spatial multiplexing of soliton microcombs under a single external laser pumping operation. This demonstration offers an ideal scheme to realize highly coherent dual-comb sources in a compact, low-cost and energy-efficient manner, with uniquely low beating noise.

Phase-Transition Microcavity Laser.

Liquid-crystal microcavity lasers have attracted considerable attention because of their extraordinary tunability and sensitive response to external stimuli, and because they operate generally within a specific phase. Here, we demonstrate a liquid-crystal microcavity laser operated in the phase transition in which the reorientation of liquid-crystal molecules occurs from aligned to disordered states. A significant wavelength shift of the microlaser is observed, resulting from the dramatic changes in the refractive index of liquid-crystal microdroplets during the phase transition.

Trapping photons with optical black hole.

An optical black-hole cavity based on transformation optics enables Q-factor enhancement and strong field confinement, by eliminating the intrinsic radiation loss of the conventional whispering-gallery modes, holding potential for applications in energy harvesting and optoelectronics.

Nonreciprocal Frequency Conversion and Mode Routing in a Microresonator.

The transportation of photons and phonons typically obeys the principle of reciprocity. Breaking reciprocity of these bosonic excitations will enable the corresponding nonreciprocal devices, such as isolators and circulators. Here, we use two optical modes and two mechanical modes in a microresonator to form a four-mode plaquette via radiation pressure force.

Dissipative Acousto-optic Interactions in Optical Microcavities.

We propose and demonstrate experimentally the strong dissipative acousto-optic interaction between a suspended vibrating microfiber and a whispering-gallery microcavity. On the one hand, the dissipative response driven by an external stimulus of acoustic waves is found to be stronger than the dispersive response by 2 orders of magnitude. On the other hand, dead points emerge with the zero dissipative response at certain parameters, promising the potentials in physical sensing such as precise measurements of magnetic field and temperature.

Electron Microscopy Probing Electron-Photon Interactions in SiC Nanowires with Ultrawide Energy and Momentum Match.

Light-matter interactions are commonly probed by optical spectroscopy, which, however, has some fundamental limitations such as diffraction-limited spatial resolution, tiny momentum transfer, and noncontinuous excitation/detection. In this work, through the use of scanning transmission electron microscopy-electron energy loss spectroscopy (STEM-EELS) with ultrawide energy and momentum match and subnanometer spatial resolution, the longitudinal Fabry-Perot (FP) resonating modes and the transverse whispering-gallery modes (WGMs) in individual SiC nanowires are simultaneously excited and detected, which span from near-infrared (∼1.2 μm) to ultraviolet (∼0.

Vibrational Kerr Solitons in an Optomechanical Microresonator.

Kerr soliton microcombs in microresonators have been a prominent miniaturized coherent light source. Here, for the first time, we demonstrate the existence of Kerr solitons in an optomechanical microresonator, for which a nonlinear model is built by incorporating a single mechanical mode and multiple optical modes. Interestingly, an exotic vibrational Kerr soliton state is found, which is modulated by a self-sustained mechanical oscillation.

Regulated Photon Transport in Chaotic Microcavities by Tailoring Phase Space.

Manipulating light dynamics in optical microcavities has been made mainly either in real or momentum space. Here we report a phase-space tailoring scheme, simultaneously incorporating spatial and momentum dimensions, to enable deterministic and in situ regulation of photon transport in a chaotic microcavity. In the time domain, the chaotic photon transport to the leaky region can be suppressed, and the cavity resonant modes show stronger temporal confinement with quality factors being improved by more than 1 order of magnitude.

Calculation of Apparent Diffusion Coefficients in Prostate Cancer Using Deep Learning Algorithms: A Pilot Study.

Background: Apparent diffusion coefficients (ADCs) obtained with diffusion-weighted imaging (DWI) are highly valuable for the detection and staging of prostate cancer and for assessing the response to treatment. However, DWI suffers from significant anatomic distortions and susceptibility artifacts, resulting in reduced accuracy and reproducibility of the ADC calculations. The current methods for improving the DWI quality are heavily dependent on software, hardware, and additional scan time.

Operando monitoring transition dynamics of responsive polymer using optofluidic microcavities.

Optical microcavities have become an attractive platform for precision measurement with merits of ultrahigh sensitivity, miniature footprint and fast response. Despite the achievements of ultrasensitive detection, optical microcavities still face significant challenges in the measurement of biochemical and physical processes with complex dynamics, especially when multiple effects are present. Here we demonstrate operando monitoring of the transition dynamics of a phase-change material via a self-referencing optofluidic microcavity.

Synthesized soliton crystals.

Dissipative Kerr soliton (DKS) featuring broadband coherent frequency comb with compact size and low power consumption, provides an unparalleled tool for nonlinear physics investigation and precise measurement applications. However, the complex nonlinear dynamics generally leads to stochastic soliton formation process and makes it highly challenging to manipulate soliton number and temporal distribution in the microcavity. Here, synthesized and reconfigurable soliton crystals (SCs) are demonstrated by constructing a periodic intra-cavity potential field, which allows deterministic SCs synthesis with soliton numbers from 1 to 32 in a monolithic integrated microcavity.

Single-mode characteristic of a supermode microcavity Raman laser.

Microlasers in near-degenerate supermodes lay the cornerstone for studies of non-Hermitian physics, novel light sources, and advanced sensors. Recent experiments of the stimulated scattering in supermode microcavities reported beating phenomena, interpreted as dual-mode lasing, which, however, contradicts their single-mode nature due to the clamped pump field. Here, we investigate the supermode Raman laser in a whispering-gallery microcavity and demonstrate experimentally its single-mode lasing behavior with a side-mode suppression ratio (SMSR) up to 37 dB, despite the emergence of near-degenerate supermodes by the backscattering between counterpropagating waves.

1/f-noise-free optical sensing with an integrated heterodyne interferometer.

Optical evanescent sensors can non-invasively detect unlabeled nanoscale objects in real time with unprecedented sensitivity, enabling a variety of advances in fundamental physics and biological applications. However, the intrinsic low-frequency noise therein with an approximately 1/f-shaped spectral density imposes an ultimate detection limit for monitoring many paramount processes, such as antigen-antibody reactions, cell motions and DNA hybridizations. Here, we propose and demonstrate a 1/f-noise-free optical sensor through an up-converted detection system.

Laser particles with omnidirectional emission for cell tracking.

The ability to track individual cells in space over time is crucial to analyzing heterogeneous cell populations. Recently, microlaser particles have emerged as unique optical probes for massively multiplexed single-cell tagging. However, the microlaser far-field emission is inherently direction-dependent, which causes strong intensity fluctuations when the orientation of the particle varies randomly inside cells.

Layered localization in a chaotic optical cavity.

We propose and demonstrate the localization of resonant modes in a Limaçon optical microcavity with layered phase space involving both major and minor partial barriers. By regulating the openness of the cavity through the refractive index control, the minor partial barriers, which do not directly confine the long-lived resonant modes, are submerged successively into the leaky region. During the invalidation process of the minor partial barriers, it is found that the quality factor and the conjugate momentum of the resonant modes exhibit changes with the emergence of turning points.

Nonlinear Sensing with Whispering-Gallery Mode Microcavities: From Label-Free Detection to Spectral Fingerprinting.

Optical microresonators have attracted intense interests in highly sensitive molecular detection and optical precision measurement in the past decades. In particular, the combination of a high quality factor with a small mode volume significantly enhances the nonlinear light-matter interaction in whispering-gallery mode (WGM) microresonators, which greatly boost nonlinear optical sensing applications. Nonlinear WGM microsensors not only allow for label-free detection of molecules with an ultrahigh sensitivity but also support new functionalities in sensing such as the specific spectral fingerprinting of molecules with frequency conversion involved.