Acoustic Purcell effect induced by quasibound state in the continuum

We study theoretically and experimentally the acoustic Purcell effect induced by quasi-bound states in the continuum(quasiBICs).A theoretical framework describing the acoustic Purcell effect of a resonant system is developed based on the system’s radiative and dissipative factors,which reveals the critical emission condition for achieving optimum Purcell factors.We show that the quasiBICs contribute to highly confined acoustic field and bring about greatly enhanced acoustic emission,leading to strong Purcell effect.Our concept is demonstrated via two coupled resonators supporting a Friedrich-Wintgen quasiBIC,and the theoretical results are validated by the experiments observing emission enhancement of the sound source by nearly two orders of magnitude.Our work bridges the gap between the acoustic Purcell effect and acoustic BICs essential for enhanced wave-matter interaction and acoustic emission,which may contribute to the research of high-intensity sound sources,high-quality-factor acoustic devices and nonlinear acoustics.

Purcell effect of GaAs quantum dots by photonic crystal microcavities

We fabricate photonic crystal slab microcavities embedded with GaAs quantum dots by electron beam lithography and droplet epitaxy. The Purcell effect of exciton emission of the quantum dots is confirmed by the micro photoluminescence measurement. The resonance wavelengths, widths, and polarization are consistent with numerical simulation results.

Silicon cuboid nanoantenna with simultaneous large Purcell factor for electric dipole,magnetic dipole and electric quadrupole emission

The Purcell effect is commonly used to increase the spontaneous emission rate by modifying the local environment of a light emitter.Here,we propose a silicon dielectric cuboid nanoantenna for simultaneously enhancing electric dipole(ED),magnetic dipole(MD)and electric quadrupole(EQ)emission.We study the scattering cross section,polarization charge distribution,and electromagnetic field distribution for electromagnetic plane wave illuminating the silicon dielectric cuboid nanoantenna,from which we have identified simultaneous existence of ED,MD and EQ resonance modes in this nanoantenna.We have calculated the Purcell factor of ED,MD and EQ emitters with different moment orientations as a function of radiation wavelength by placing these point radiation source within the nanoantenna,respectively.We find that the resonances wavelengths of the Purcell factor spectrum are matching with the resonance modes in the nanoan-tenna.Moreover,the maximum Purcell factor of these ED,MD and EQ emitters is 18,150 and 118 respectively,occur-ring at the resonance wavelength of 475,750,and 562 nm,respectively,all within the visible range.The polarization charge distribution features allow us to clarify the excitation and radiation of these resonance modes as the physical ori-gin of large Purcell factor simultaneously occurring in this silicon cuboid nanoantenna.Our theoretical results might help to deeply explore and design the dielectric nanoantenna as an ideal candidate to enhance ED,MD and EQ emission simultaneously with very small loss in the visible range,which is superior than the more popular scheme of plasmonic nanoantenna.

Photoluminescence control by hyperbolic metamaterials and metasurfaces:a review

Photolu min esce nee in clud ing fluoresce nee plays a great role in a wide variety of applicati ons from biomedical sensing and imag ing to optoelectr on ics.Therefore,the enhan ceme nt and con trol of photolu min esce nee has imme nse impact on both fun dame ntal scie ntific research and aforeme nti oned applicati ons.Among various nano phot tonic schemes and nanostructures to enhance the photoluminescence,we focus on a certain type of nanostructures,hyperbolic metamaterials(HMMs).HMMs are highly ani sotropic metamaterials,which produce intense localized electric fields.Therefore,HMMs n aturally boost photolu min esce nee from dye molecules,qua ntum dots,n itroge n-vaca ncy cen ters in diam on ds,perovskites and tra nsiti on metal dichalcoge nides.We provide an overview of various con figuratio ns of HMMs,i nclud ing metal-dielectric multilayers,trenches,metallic nanowires,and cavity structures fabricated with the use of noble metals,transparent conductive oxides,and refractory metals as plasmonic elements.We also discuss lasing action realized with HMMs.

Magnetic and electric Purcell enhancement in a hybrid metal-dielectric nanostructure

Hybrid metal-dielectric structures combine the advantages of both metal and dielectric materials,enabling high-confined but low-loss magnetic and electric resonances through deliberate arrangements.However,their potential for enhancing magnetic emission has yet to be fully explored.Here,we study the magnetic and electric Purcell enhancement supported by a hybrid structure composed of a dielectric nanoring and a silver nanorod.This structure enables low Ohmic loss and highlyconfined field under the mode hybridization of magnetic resonances on a nanoring and electric resonances on a nanorod in the optical communication band.Thus,the 60-fold magnetic Purcell enhancement and 45-fold electric Purcell enhancement can be achieved.Over 90%of the radiation can be transmitted to the far field.For the sufficiently large Purcell enhancement,the position of emitter has a tolerance of several tens of nanometers,which brings convenience to experimental fabrications.Moreover,an array formed by this hybrid nanostructure can further enhance the magnetic Purcell factors.The system provides a feasible option to selectively excite magnetic and electric emission in integrated photonic circuits.It may also facilitate brighter magnetic emission sources and light-emitting metasurfaces with a more straightforward design.

基于CsPbBr_(3)纳米片的低阈值上转换等离子体激光器

上转换激光器为新一代高度集成的非线性光电应用提供了一个强大的平台,解决了现代光子集成电路不断发展对小型化、低损耗和高质量非线性光源的诉求.然而,对于具有反斯托克斯过程的上转换激光器,减小尺寸和阈值是其不可避免的巨大挑战.本文报道了一种基于CsPbBr_(3)纳米片的室温上转换等离子体纳米激光器,该激光器在较宽的尺寸范围内表现出显著的阈值降低,同时依旧保持着较高的品质因子.更激动人心的是,本文成功制造了厚度低至70 nm的小型化上转换等离子体激光器,突破光学衍射极限到深亚波长范围.同时,本文利用仿真模拟描述了双光子激发光场的分布情况,揭示了等离子体辅助激光发射并降低阈值的过程.此外,SiO_(2)绝缘层厚度依赖实验证明了双光子激发光约束强度和珀塞尔效应的可调谐特性,这为实现等离子体器件性能的有效调控提供了有效方案.本文展示了高效和低阈值的上转换等离子体纳米激光器,为片上非线性光源的发展奠定了夯实的基础.

Spontaneous emission rate enhancement of nano-structured silicon by surface plasmon polariton

Surface plasmon polariton （SPP） is an attractive candidate to improve internal quantum efficiency （QE） of spontaneous emission （SE） from nano-structured silicon （Si） including nano-porous silicon （NP-Si） and silicon nanocrystal （Si-NC）. Since the SPP resonant frequency of common metals, e.g., gold （Au）, silver （Ag）, copper （Cu）, and aluminum （A1）, is too high, the SPP resonance has to be engineered to match the luminescence from nano- structured Si. For this purpose, we have proposed and demonstrated three approaches including metal-rich Au（1-a）-SiO2（a） cermet SPP waveguide （WG）, com- pound layer structure WG and metallic grating. In this paper, those approaches are reviewed and discussed. According to the calculated results, such three methods could effectively enhance SE rate from NP-Si or Si-NCs and show potential in developing high efficiency Si based light sources with electric pump.