圆柱形光声池结构及环境因素对声学本征频率的影响

以典型的圆柱形光声池为研究对象,建立光声池声学仿真有限元模型,并在此基础上,研究了光声池中谐振腔、缓冲腔、进出气孔结构参数以及温度、湿度因素对其声学本征频率的影响规律.研究结果表明:圆柱形光声池的进、出口孔对其声学本征频率影响极不敏感,设计计算中可以忽略不计,谐振腔的长度影响最为敏感,其次为谐振腔的直径.此外缓冲腔的长度与直径对其亦有一定影响,因而在准确计算时需要加以考虑.温度与湿度对光声池声学本征频率的影响均呈现正线性增长规律,温度的影响随着谐振腔长度的增大而减小,湿度的影响随着温度的升高而增大,仅计算光声池的声学本征频率时,湿度的影响在室温环境下且湿度变动较小的条件下可以忽略.     

Bioanalytical chemistry of cytokines – A review

Cytokines are bioactive proteins produced by many different cells of the immune system. Due to their role in different inflammatory disease states and maintaining homeostasis, there is enormous clinical interest in the quantitation of cytokines. The typical standard methods for quantitation of cytokines are immunoassay-based techniques including enzyme-linked immusorbent assays (ELISA) and bead-based immunoassays read by either standard or modified flow cytometers. A review of recent developments in analytical methods for measurements of cytokine proteins is provided. This review briefly covers cytokine biology and the analysis challenges associated with measurement of these biomarker proteins for understanding both health and disease. New techniques applied to immunoassay-based assays are presented along with the uses of aptamers, electrochemistry, mass spectrometry, optical resonator-based methods. Methods used for elucidating the release of cytokines from single cells as well as in vivo collection methods are described.     

Enhanced light‐vapor interactions and all optical switching in a chip scale micro‐ring resonator coupled with atomic vapor

The coupling of atomic and photonic resonances serves as an important tool for enhancing light‐matter interactions and enables the observation of multitude of fascinating and fundamental phenomena. Here, by exploiting the platform of atomic‐cladding wave guides, the resonant coupling of rubidium vapor and an atomic cladding micro ring resonator is experimentally demonstrated. Specifically, cavity‐atom coupling in the form of Fano resonances having a distinct dependency on the relative frequency detuning between the photonic and the atomic resonances is observed. Moreover, significant enhancement of the efficiency of all optical switching in the V‐type pump‐probe scheme is demonstrated. The coupled system of micro‐ring resonator and atomic vapor is a promising building block for a variety of light vapor experiments, as it offers a very small footprint, high degree of integration and extremely strong confinement of light and vapor. As such it may be used for important applications, such as all optical switching, dispersion engineering (e.g. slow and fast light) and metrology, as well as for the observation of important effects such as strong coupling, and Purcell enhancement.

     

超材料谐振子间的电耦合谐振理论与实验研究

通过将两个金属开口环谐振器口对口地放置, 实现了超材料谐振子间的电耦合谐振. 对电耦合谐振的微波等效电路进行了理论分析和数值计算, 结果表明耦合后的超材料谐振子能产生两个谐振频率, 其中一个随耦合强度的增加逐渐向低频方向移动, 而另一个固定在单谐振子的谐振频率处不变. 微波透射谱的实验测试和电磁仿真结果表明, 两个谐振峰随耦合强度的增加分别向低频和高频方向移动. 分析表明: 低频谐振峰的位置主要是由超材料谐振子间的电耦合强度决定的; 高频谐振偏离单谐振子的谐振频率主要是由不可避免的磁耦合引起的, 而且在耦合间距越小时磁耦合影响越大. 提出的基于超材料谐振子间的电磁耦合实现的双频谐振及其可调性极大地增加了超材料的设计与应用空间.     

Dynamics problems of micro/nano channel resonators for detection and characterization

微纳通道机械谐振器在液体环境中具有超高的谐振频率、品质因子和灵敏度,常用于液体环境中的高精度检测与表征,在生物、医药、化工等领域有着广阔的应用前景.微纳通道机械谐振器的检测与表征功能高度依赖其动力学特性,而此类器件是由谐振结构、内部流体、被检测物和外部激励等多因素组成的耦合系统,涉及的动力学问题较为复杂,已成为谐振器件研究中的前沿热点和瓶颈问题.本文综述了微纳通道机械谐振器的研究进展,总结了谐振器件实现高精度检测与表征功能时的动力学设计原理,详细讨论了谐振器件的稳定性、频响特性、能量耗散、频率波动等动态特性,阐明了不同动力学问题的物理机制及其对谐振器性能的影响规律,可为深入厘清微纳通道机械谐振器的动力学设计问题,提高器件动态性能提供理论参考和技术支撑,对超高频、超高灵敏度谐振器的设计、制造及应用发展具有重要意义.     

Spectral engineering of coupled open‐access microcavities

Open‐access microcavities are emerging as a new approach to confine and engineer light at mode volumes down to the λ³ regime. They offer direct access to a highly confined electromagnetic field while maintaining tunability of the system and flexibility for coupling to a range of matter systems. This article presents a study of coupled cavities, for which the substrates are produced using Focused Ion Beam milling. Based on experimental and theoretical investigation the engineering of the coupling between two microcavities with radius of curvature of 6 m is demonstrated. Details are provided by studying the evolution of spectral, spatial and polarisation properties through the transition from isolated to coupled cavities. Normal mode splittings up to 20 meV are observed for total mode volumes around . This work is of importance for future development of lab‐on‐a‐chip sensors and photonic open‐access devices ranging from polariton systems to quantum simulators.

     

半波长超导共面波导谐振腔传输及温度特性研究

超导共面波导谐振腔主要包括四分之一波长型和半波长型.本文对半波长超导共面波导谐振腔使用并联RLC电路进行等效分析,使用sonnet软件进行仿真其传输特性,通过电子束蒸发和激光直写等工艺制备出样品,在低温超导状态下使用矢量网络分析仪对其传输特性进行测量,以及通过持续降温方式研究其传输特性受温度的影响.实验表明:测得的谐振频率和外部品质因数与设计值吻合;谐振频率受动态电感的影响随温度降低而升高;外部品质因数随温度降低而保持基本不变;内部品质因先受导体损耗的影响随温度降低而急剧升高,当温度降低至一定温度后内部品质因数受介电损耗的影响随温度降低而保持基本不变;总品质因数在温度较高时主要来自于导体损耗,在温度较低时主要来自于介电损耗和外部品质因数,随温度的变化趋势和内部品质因数一致.     

Tens of GHz Tantalum pentoxide‐based micro‐ring all‐optical modulator for Si photonics

A tantalum pentoxide‐based (Ta₂O₅‐based) micro‐ring all‐optical modulator was fabricated. The refractive index inside the micro‐ring cavity was modified using the Kerr effect by injecting a pumped pulse. The transmittance of the ring resonator was controlled to achieve all‐optical modulation at the wavelength of the injected probe. When 12 GHz pulses with a peak power of 1.2 W were coupled in the ring cavity, the transmission spectrum of the Ta₂O₅ resonator was red‐shifted by 0.04 nm because of the Kerr effect. The relationship between the modulation depth and gap of the Ta₂O₅ directional coupler is discussed. An optimized gap of 1100 nm was obtained, and a maximum buildup factor of 11.7 with 84% modulation depth was achieved. The nonlinear refractive index of Ta₂O₅ at 1.55 μm was estimated as 3.4 × 10^?14 cm²/W based on the Kerr effect, which is almost an order of magnitude higher than that of Si₃N₄. All results indicate that Ta₂O₅ has potential for use in nonlinear waveguide applications with modulation speeds as high as tens of GHz.

     

QCM based sensor for detecting volumetric properties of liquids

We introduce a microacoustic sensor, which combines the quartz crystal microbalance, a liquid-filled cavity and an intermediate artificial layer with effective acoustic properties. Each of the three components fulfils a specific task. The quartz vibrates in its thickness shear mode and acts as source and detector of shear waves, which penetrate the intermediate artificial layer and excite a resonance in the liquid-filled cavity. Both the piezoelectric transducer and the liquid-filled cavity are high-Q resonators with well-adjusted resonance frequencies very close to each other. The intermediate artificial layer couples the two resonators in a distinct manner via control of the propagation of acoustic waves between the quartz crystal and the liquid-filled cavity layer. The origin of the sensor signal is a change of the resonance frequency of the liquid-filled cavity caused by variations of acoustic properties of the liquid analyte inside the cavity, first of all speed of sound. This resonance appears as second resonance peak in the admittance spectrum of the quartz crystal.     

Pseudo-spectral time-domain simulation of the transmission and the group delay of photonic devices

The pseudo-spectral time-domain (PSTD) method is applied to the simulation of photonic structures. We study transmission and group delay properties of dielectric and dispersive devices. An auxiliary differential equation technique is used to model the dispersive behavior of metallic features. Comparisons with the finite-difference time-domain method show the superiority of the PSTD method in particular when extracting phase information from a photonic device. The validity of the algorithm is demonstrated by investigating a ring resonator, Bragg gratings and metallic nano-particle arrangements.