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[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

We review the field of cavity optomechanics, which explores the interaction between electromagnetic radiation and nano- or micromechanical motion This review covers the basics of optical cavities and mechanical resonators, their mutual optomechanical interaction mediated by the radiation pressure force, the large variety of experimental systems which exhibit this interaction, optical measurements of mechanical motion, dynamical backaction amplification and cooling, nonlinear dynamics, multimode optomechanics, and proposals for future cavity quantum optomechanics experiments In addition, we describe the perspectives for fundamental quantum physics and for possible applications of optomechanical devices

Cavity Optomechanics

It is now shown that coupled optical microcavities bear all the hallmarks of parity–time symmetry; that is, the system’s dynamics are unchanged by both time-reversal and mirror transformations. The resonant nature of microcavities results in unusual effects not seen in previous photonic analogues of parity–time-symmetric systems: for example, light travelling in one direction is resonantly enhanced but there are no resonance peaks going the other way.

Parity–time-symmetric whispering-gallery microcavities

In recent years, notions drawn from non-Hermitian physics and parity–time (PT) symmetry have attracted considerable attention. In particular, the realization that the interplay between gain and loss can lead to entirely new and unexpected features has initiated an intense research effort to explore non-Hermitian systems both theoretically and experimentally. Here we review recent progress in this emerging field, and provide an outlook to future directions and developments. This Review Article outlines the exploration of the interplay between parity–time symmetry and non-Hermitian physics in optics, plasmonics and optomechanics.

Non-Hermitian physics and PT symmetry

Non-Hermitian systems have attracted considerable attention for their broad impacts on various physical platforms and peculiar applications. In non-Hermitian systems, both eigenvalues and eigenstates simultaneously coalesce at exceptional points (EPs). As one of the remarkable features of EPs, the field chirality is commonly considered perfect, which is utilized as an intriguing feature to control wave propagation and regarded as a criterion of EP. However, in this work, we discover an imperfect chirality of eigenmodes at the EPs in an optical whispering gallery mode (WGM) microcavity perturbed by two strong nanoscatterers. This counterintuitive phenomenon originates from a strong frequency-dependence of the scattering between the counterpropagating waves at an “effective scatterer”, which could be explained by a first-principle-based model considering a dynamic multiple-scattering process of the azimuthally propagating modes. We find that the generally imperfect chirality at the EP tends to be globally perfect with the decrease of the scattering effect induced by the nanoscatterers. Furthermore, the chirality also becomes locally perfect with the decrease of the relative azimuthal angle between the two strong nanoscatterers. This work provides a new understanding of the general properties of chirality at EPs. It will benefit the potential applications enabled by the chirality features of non-Hermitian systems at EPs. Exceptional points (EPs) [1,2] are spectral degeneracies The Supplemental Material provides some details for the dependence of the scattering coefficients on the location, refractive index and size of the nanoscatterer, additional logic and numerical test on the validity of the model, some additional explanation of the conditional perfect chirality at exceptional points (EPs), evolution of reflection coefficients as functions of the relative azimuthal angle  between the two nanoholes, and additional results of the electric-field intensities at the EPs for different  .

Imperfect chirality at exceptional points in optical whispering-gallery microcavities

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Publisher Correction: Optomechanical dissipative solitons

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Author Correction: Optomechanically-induced transparency in parity-time-symmetric microresonators

We theoretically and experimentally demonstrate that thermal effect in ultra-high-Q silica toroidal microresonators can be compensated by applying a layer of polydimethylsiloxane (PDMS). The observed Q factor is 1.5×106 for coating thickness of 0.52 µm.

Compensation of thermal effect in high-Q toroidal microresonators by PDMS coating

Whispering Gallery Mode (WGM) microresonators are a powerful class of optical devices in which light is confined within a small volume. These devices offer the advantages of high sensitivity, affordable cost of fabrication, and ease of integration with conventional electronic systems. In particular, microbubble resonators are a unique type of WGM devices in which the optical and fluidic elements are combined into a single component. We have developed a packaged, silica microbubble resonator device for field applications using 3-D printed substrates. These devices offer Qfactors at high as 106.

Lan Yang

Papers

Imperfect chirality at exceptional points in optical whispering-gallery microcavities

Publisher Correction: Optomechanical dissipative solitons

Author Correction: Optomechanically-induced transparency in parity-time-symmetric microresonators

Compensation of thermal effect in high-Q toroidal microresonators by PDMS coating

Packaged microbubble resonators as a robust field sensing device