Dual-stimuli responsive photonic barcodes based on perovskite quantum dots encapsulated in whispering-gallery-mode microspheres

Micro/nanoscale photonic barcodes hold great potential for broad applications in items tracking,mul-tiplexed bioassays and anti-counterfeiting.The ever-increasing demand in advanced anti-counterfeiting applications calls for micro/nanoscale barcodes with accurate recognition,large encoding capacity and high security level.Here,we proposed a strategy to construct the dual-stimuli responsive photonic barcodes based on the perovskite quantum dots(PQDs)doped polymer whispering-gallery-mode(WGM)microcavities via swelling-deswelling method.Benefiting from the well-defined spherical microcavities,the photoluminescence(PL)spectra of as-prepared composites exhibit a series of sharp peaks characteristics resulting from the effective WGM modulation,which constitutes the fingerprint of a specific resonator and thus allows a definition of photonic barcodes.On this basis,we achieved responsive photonic barcodes based on the volatile polar-solvent-controlled luminescence in the mi-crospheres benefitting from the space-confined microcavities and the ionic feature of the PQDs.More-over,the light-controlled photonic barcodes have further been acquired through reversibly regulating the inactivation and activation of the energy transfer(ET)process between the PQDs and photochromic dyes.The well-established protocols of PQDs@WGM enable the development of distinct responsive barcodes with multi-responsive features,which will pave an avenue to new types of flexible WGM-based components for optical data recording and security labels.

2D-material-integrated whispering-gallery-mode microcavity

Optical microcavities, which support whispering gallery modes, have attracted tremendous attention in both fundamental research and potential applications. The emerging of two-dimensional materials offers a feasible solution to improve the performance of traditional microcavity-based optical devices. Besides, the integration of two-dimensional materials with microcavities will benefit the research of heterogeneous materials on novel devices in photonics and optoelectronics, which is dominated by the strongly enhanced light–matter interaction.This review focuses on the research of heterogeneous two-dimensional-material whispering-gallery-mode microcavities, opening a myriad of lab-on-chip applications, such as optomechanics, quantum photonics, comb generation, and low-threshold microlasing.

Experimental observation of Fano-like resonance in a whispering-gallery-mode microresonator in aqueous environment

We report on the transmission spectra of a sausage-like microresonator(SLM)in aqueous environment,where a fiber taper is used as a light coupler.The transmission spectra show an interesting dependence on the coupling position between the SLM and the fiber taper.When the SLM is moved along the fiber taper,the line shape can evolve periodically among symmetric dips,asymmetric Fano-like resonance line shapes,and symmetric peaks.A coupled-mode theory with feedback is developed to explain the observation.The observation of Fano-like resonance in aqueous environment holds great potential in biochemical sensing.

Linearly polarised three-colour lasing emission from an evanescent wave pumped and gain coupled fibre laser

A novel Whispering-Gallery-Mode （WGM） fibre laser, emitting linearly polarised three-colour light, is demonstrated by pumping and gain coupling with evanescent waves. The pump light is longitudinally coupled into a bare optical fibre immersed in a dye solution of lower refractive index. The dye molecules around the bare fibre are excited by the evanescent waves of pump light when they propagate along the fibre in a total internal reflection. When the pump beam within the fibre is a meridian beam, the WGM lasing emission from the fibre laser is a linearly polarised transverse electric wave, while it is a mixed wave of the linearly polarised transverse electric and magnetic waves if the pump beam is a skew beam within the fibre. Because the excited molecules are located within the evanescent field of WGM, a good spatial overlap between the dye gain and the evanescent field leads to a high pumping efficiency and a longer gain distance along the fibre. Once the bare fibre is inserted into three glass capillaries filled with Rhodamine 6G, 610 and 640 dye solutions, respectively, WGM laser oscillations at the wavelengths of 567-575, 605-614 and 656-666 nm occur simultaneously, and a linearly polarised three-colour lasing emission is achieved in a single optical fibre.

STUDY OF CROSSED FIELD GYROTRON OPERATING ON WHISPERING-GALLERY MODE

A linear and nonlinear analysis of crossed-field gyrotron operating on whispering-gallery mode TEm11 is presented. The detailed discussions are given for the starting oscillationcondition, the effect of the internal conductor in coaxial cavity on the cut-off frequency of modeand the spacing between adjacent modes as well as the effect of the applied voltage on thecyclotron frequency of electron, the starting oscillation beam power and the electron efficiency.It is shown that the efficiency of 41% can be attained for m=2. A comparison of these resultswith those in cylindrical cavity is made. The analyses are helpful for the engineering design.

聚苯乙烯微粒光子晶体的反常透过特性

在实验上发现了 3μm聚苯乙烯 (PS)小球光子晶体在 35 0nm至 90 0nm波长上的透过率的周期扰动 .根据透过率曲线的周期扰动的峰谷值判断 ,这种周期性透过率特性是基于PS小球的whispering gallery mode(WGM)共振 ,而不是源于米氏散射或布拉格衍射 .实验表明 ,周期性排列小球在非带隙区域对光的传输同样有一定的影响 .

Plasmon enhancement for Vernier coupled single-mode lasing from ZnO/Pt hybrid microcavities

It is essential to develop a single mode operation and improve the performance of lasing in order to ensure practical applicability of microlasers and nanolasers. In this paper, two hexagonal microteeth with varied nanoscaled air-gaps of a ZnO microcomb are used to construct coupled whispering-gallery cavities. This is done to achieve a stable single mode lasing based on Vernier effect without requiring any complicated or sophisticated manipulation to achieve positioning with nanoscale precision. Optical gain and the corresponding ultraviolet lasing performance were improved greatly through coupling with localized surface plasmons of Pt nanoparticles. The ZnO/Pt hybrid microcavities achieved a seven-fold enhancement of intensity of single mode lasing with higher side- mode suppression ratio and lower threshold. The mechanism that led to this enhancement has been described in detail.

Whispering-gallery mode hexagonal micro-/nanocavity lasers [Invited]

Whispering-gallery-mode(WGM) hexagonal optical micro-/nanocavities can be utilized as high-quality(Q) resonators for realizing compact-size low-threshold lasers. In this paper, the progress in WGM hexagonal micro-/nanocavity lasers is reviewed comprehensively. High-Q WGMs in hexagonal cavities are divided into two kinds of resonances propagating along hexagonal and triangular periodic orbits, with distinct mode characteristics according to theoretical analyses and numerical simulations;however, WGMs in a wavelength-scale nanocavity cannot be well described by the ray model. Hexagonal micro-/nanocavity lasers can be constructed by both bottom-up and top-down processes, leading to a diversity of these lasers. The ZnO-or nitride-based semiconductor material generally has a wurtzite crystal structure and typically presents a natural hexagonal cross section. Bottom-up growth guarantees smooth surface faceting and hence reduces the scattering loss effectively.Laser emissions have been successfully demonstrated in hexagonal micro-/nanocavities synthesized with various materials and structures. Furthermore, slight deformation can be easily introduced and precisely controlled in top-down fabrication, which allows lasing-mode manipulation. WGM lasing with excellent singletransverse-mode property was realized in waveguide-coupled ideal and deformed hexagonal microcavity lasers.

Conformal optical black hole for cavity

Whispering-gallery-mode(WGM)cavity is important for exploring physics of strong light-matter interaction.Yet it suffers from the notorious radiation loss universally due to the light tunneling effect through the curved boundary.In this work,we propose and demonstrate an optical black hole(OBH)cavity based on transformation optics.The radiation loss of all WGMs in the ideal OBH cavity is completely inhibited by an infinite wide potential barrier.Besides,the WGM field in the OBH cladding is revealed to follow 1/r decay rule based on conformal mapping,which is fundamentally different from the conventional Hankel-function distributions in a homogeneous cavity.Experimentally,a truncated OBH cavity is achieved based on the effective medium theory,and both the Q-factor enhancement and tightly confined WGM fields are measured in the microwave spectra which agree well with the theoretical results.The circular OBH cavity is further applied to the arbitrary-shaped cavities including single-core and multi-core structures with high-Q factor via the conformal mapping.The OBH cavity design strategy can be generalized to resonant modes of various wave systems,such as acoustic and elastic waves,and finds applications in energy harvesting and optoelectronics.