光学元件亚表面缺陷的全内反射显微检测

 光学元件亚表面缺陷的有效检测已成为高阈值抗激光损伤光学元件制造的迫切要求。基于全内反射照明原理开展了全内反射显微技术检测光学元件亚表面缺陷的实验研究。结果表明：全内反射显微技术可有效检测光学元件亚表面缺陷;入射光偏振态和入射角度会影响元件内界面下不同深度处驻波形式照明强度的分布,对于可见度发生明显改变的微小缺陷点能衡量出其一定的深度尺寸范围;利用显微镜精密调焦对界面下一定深度处缺陷成像,可知缺陷点的位置深度。     

Pigtailing the high-Q microsphere cavity: a simple fiber coupler for optical whispering-gallery modes

We demonstrate a simple method for efficient coupling of standard single-mode optical fibers to a high- Q optical microsphere cavity. Phase-matched excitation of whispering-gallery modes is provided by an angle-polished fiber tip in which the core-guided wave undergoes total internal reflection. In the experimental setup, which included a microsphere with both an input and an output coupler, the total fiber-to-fiber transmission at resonance reached 23% (total insertion loss, 6.3 dB), with loaded quality factor Q>/=3x10(7) and unloaded Q approximately 1.2x10(8) at 1550 nm. A simple pigtailing method for microspheres permits their wider use in fiber optics and photonics devices.     

Fiber laser using a microsphere resonator as a feedback element

We show that a glass microsphere resonator can be used as a wavelength-selective mirror in fiber lasers. Due to their high quality factor (Q approximately 10(8)), microsphere resonators possess a narrow reflection bandwidth. This feature enables construction of single-frequency fiber lasers even when the laser cavity is long. Nonlinear effects (such as stimulated Raman lasing) were also observed in our setup at relatively low pump powers.     

Using the atomic force microscope as a nanomechanical partner to support evanescent field imaging

Quantum Dot (QD)/microsphere structures supporting Whispering Gallery Modes (WGMs) are attached to Atomic Force Microscope (AFM) cantilevers for characterization of the evanescent field around the QD/microsphere and utilization of the evanescent field for sensing at the apical surface of live cells. Following laser excitation, QD emission couples to WGMs that circumnavigate the microsphere via total internal reflection at the internal surfaces of the microsphere. The resulting evanescent field is characterized utilizing the high spatial control of an AFM in approaching a dye monolayer on a test surface. The measured evanescent field extends approximately 50 nm from the microsphere surface, matching theoretical predictions. This system was then used to sense the accumulation of integrin and formation of focal adhesions at the apical surface of cells.     

Development of multi-wavelength microsphere fibre laser system for potential sensor applications

A multi-wavelength microsphere laser system, using a chirped fibre Bragg grating and a microsphere resonator as wavelength-selective elements and a high dopant erbium doped fibre as the gain material, has been successfully demonstrated. The multi-wavelength generation of the laser system arises from both the microsphere whispering gallery mode selection and from the additional Raman scattering inside the microsphere cavity when the erbium laser is operating at resonance with the whispering gallery modes. Through an appropriate design and fabrication of a microsphere and of a fibre taper, a selective multi-wavelength fibre laser has been realized when the pump power is above threshold required. The laser output lines created have shown much narrower linewidths than those from conventional fibre lasers and these characteristics are particularly suitable for the range of sensor applications envisaged in the work.     

固-固无限周期声子晶体中SH波全反射隧穿的谐振理论

利用边界条件推导出SH波在一维固-固声子晶体中的转移矩阵, 得出一维固-固无限周期声子晶体中SH波的色散关系. 通过建立一维固-固无限周期声子晶体的谐振腔模型并利 用共振条件得出SH波的全反射隧穿的波长公式. 利用波长公式研究了SH波全反射隧穿的波长变化规律, 其结果与色散法一致. 解释了一维固-固无限周期声子晶体中SH波的全反射隧穿效应产生的原因. 关键词： 声子晶体 SH波 全反射隧穿 谐振理论     

Optical microresonator based on hollow sphere with porous wall for chemical sensing

A porous-wall hollow glass microsphere (PW-HGM) was investigated as an optical resonator for chemical vapor sensing. A single mode optical fiber taper was used to interrogate the microresonator. Adsorption of chemical molecules into the nanosized pores induced a refractive index change of the thin wall and thus a shift in its resonance spectrum. The PW-HGM resonator had shown higher vapor detection sensitivity in comparison with a solid microsphere under similar test conditions.     

Evaluation of single virus detection through optical biosensor based on microsphere resonator

Shift of resonance frequency in microsphere optical resonator due to attachment of a desirable particle is obtained. Our 3-D finite element numerical method (FEM) simulations’ results show the path of light through microsphere and its variation due to attachment of particle. It is apparent that after attachment of particle to microsphere's surface, light is inclined to pass through the particle. Subsequently, the path of light becomes longer than previous. Because of this phenomenon, the resonance wavelength shifts to longer wavelengths. It is shown that microsphere optical resonator is a prominent biosensor for single virus detection since we applied characteristics of virus for particle in our simulations. Response of this biosensor depends on the characteristics of particle like its radius as we show in this article. Transmission spectrum of fiber which reveals a selected resonance frequency, have been studied in the frequency range of 106.3 to 107 THz under three different sizes of particles. The results show that the amount of frequency shift rises by enhancement of particle's size.     

Nonlinear response of a bistable ferromagnetic resonator to a microwave pulse

The reflection frequency response and bistability characteristic of a ferromagnetic resonator are studied experimentally and theoretically. The resonator is a 25-µm-thick rectangular yttrium-iron-garnet film with perpendicular magnetization. A technique to construct the bistability characteristic of the resonator from its measured response to a pulsed signal is suggested. It is demonstrated that the microwave bistability results from the intrinsic nonlinearity of ferromagnetic resonance. It is found that the bistability characteristic can adequately be described on the basis of a dispersive-bistability model.     

活细胞内的单分子荧光成像方法

文章介绍近年来新发展的几种重要的活细胞内单分子荧光成像方法,如转盘式共聚焦显微术、全内反射荧光显微术、荧光共振能量转移技术等。通过介绍它们的原理、特点和在活细胞内单分子行为研究中的应用实例,展示了这些新方法在生命科学领域广阔的应用前景。     

Dynamics of a Boundary Layer in Nonlinear Total Internal Reflection Inside a Laser Resonator

Computer simulation of the processes occurring in a thin layer of absorbing liquid adjoining a transparent dielectric with internal reflection from the interface is carried out for the case where the reflector is incorporated into the resonator of a solid-state laser. It is shown that the process of heating the liquid layer near the wall is essentially nonadiabatic. The sharp increase in the pressure of the liquid in the period of maximal heating leads to a situation where the temperatures of switching on and switching off of the total internal reflection at the interface become substantially different. The difference becomes smaller with decrease in the liquid-layer thickness due to a more efficient heat removal, which displays itself as a change in the character of single-pulse laser generation. Periodic emission of nanosecond pulses in the liquid layer in a quasistationary lasing regime is found, whose characteristic feature is stabilization of the liquid-layer temperature.     

Planar waveguide‐resonator: a new device for x‐ray optics

Systematic investigations of the width dependence on the x‐ray beam propagation mechanism for a narrow extended slit formed by two plane dielectric plates are presented. It is shown that the mechanism of a multiple consecutive total reflection for Cu Kα radiation dominates in a slit width range s ≥ 3 µm. At the same time the manner of Cu Kα radiation propagation for super‐narrow slits s ≤ 0.1 µm is very different from the multiple total reflection mechanism. The x‐ray beam intensity proves to be constant for all this range of magnitude. This gives grounds to expect that the super‐narrow slit area is characterized by a specific type of mechanism of x‐ray beam propagation: waveguide‐resonance. A simple model for the waveguide‐resonance propagation mechanism based on the formation of a uniform x‐ray standing wave interference field in the total space of a narrow extended slit was developed. The design of a new x‐ray optical device, namely a planar x‐ray waveguide‐resonator, is proposed based on the waveguide‐resonance mechanism. Some properties of the composite planar x‐ray waveguide‐resonator are discussed. It is shown that under specific conditions the composite waveguide can demonstrate a partial tunneling effect of the x‐ray beam. The main applications of the new technique are discussed. Copyright © 2004 John Wiley & Sons, Ltd.     

Optical bistability and modulation of light in a thin-film resonator based on total internal reflection

An approximate theoretical analysis is given of the bistable behavior of a simple resonator based on total internal reflection. It is assumed that the medium within the resonator is simultaneously absorbing and nonlinear. It is found that the amplitude bistability characteristics can be comparable to analogous characteristics for more complicated total-internal-reflection structures whose operation is based on tunnel excitation of waveguide modes. It is shown that strong phase bistability is possible in nonabsorbing total-internal-reflection resonators, and the possibility of using total-internal-reflection resonators as light modulators is discussed. Zh. Tekh. Fiz. 67, 38–42 (December 1997)     

Theory of gyrotropic ring resonators with counterpropagating modes coupling

The Faraday effect in ring resonators leads to the resonance splitting of clockwise and counter-clockwise propagating modes. In this work we investigate how this resonance splitting influences the ring resonator's behavior if both modes are coupled by a sidewall corrugation of the resonator. Coupled mode theory is used to evaluate the transmission and reflection characteristics of a ring resonator coupled to a waveguide. Based on these evaluations, we characterize a novel ring resonator switch. The resonance of the corrugated gyrotropic resonator coupled to a waveguide can be switched off by the application of the external magnetic field. In this case, the resonance is not shifted, as what typically occurs at small perturbations, but suppressed.     

Transformation of intensity fluctuations in nonlinear reflection of light

The transformation of intensity fluctuations accompanying the nonlinear resonance reflection of light from a glass-resonant gas interface is discussed. The illumination of the interface at angles close to the critical angle for total internal reflection is found to have certain advantages over orthogonal incidence. At the maximum of the strongest resonance, the reflected light intensity amounts to more than 50% of the incident light. In these conditions, a squeezing of the amplitude (photon) fluctuations is observed in the radiation generated by a semiconductor laser-nonlinear selective reflector system. A simple semiclassical theory adequately describes some important characteristics of this system: the shape of the reflection resonances, the strength of the saturation fields, and so on.     

A broadband asymmetric microwave metamaterial based on LC and standing-wave resonances

Three metamaterial samples were simulated, numerically analyzed, and fabricated with different resonator lengths on similar unit cells. According to the results in addition to conventional LC resonance of the resonator, standing wave resonance was also observed within the resonator-dielectric-grounded back wire waveguide. We observed that the orientation of the sides of this waveguide relative to the polarization of the incident electromagnetic wave has a direct effect on the resonant frequency. The best asymmetric shape of the resonator with the minimum reflection coefficient in a wide frequency range of about 5.5 GHz with only 3% of reflection was introduced. According to the results, metamaterial polarizers and optical filters can be produced based on the standing wave resonances.     

Effects of using a metal layer in total internal reflection fluorescence microscopy

This proceeding examines the characteristics of imaging through a metal-coated glass cover slip using total internal reflection fluorescence microscopy (TIRFM). Through back and front focal plane imaging of sub-diffraction-limited fluorescent beads, the experimental characteristics of the emission are compared with theoretical simulations. Furthermore, at the angle at which surface plasmon resonance occurs, we show that the anisotropic emission of the fluorescent beads collected through the metal layer results in a irregular point spread function that has a donut-like structure with multiple concentric rings. PACS 42.30.Va; 73.20.Mf     

全内反射荧光显微术

全内反射荧光显微技术是当今世界上最具前途的新型生物光学显微技术之一，可以用来实现对单个荧光分子的直接探测。它利用全内反射产生的隐失波照明样品，使照明区域限定在样品表面的一薄层范围内，因此具有其它光学成像技术无法比拟的高的信噪比和对比度。近上来，已被生物物理学家们广泛应用于单分子的荧光成像中。本文系统的介绍了全内反射荧光显微技术的原理。国内外的发展和现状及其在生物学上的应用，并对其未来做了展望。     

Propagation of waves and chaos in transmission line with strongly anharmonic dangling resonator

Delayed differential equation of motion with multiple lags is derived for an anharmonic stub resonator coupled to a monomode transmission line. Transmission and reflection coefficients are found analytically in the harmonic approximation. Nonlinear response of the system is analysed by an electric circuit obeying the same equations of motion. Enhanced second harmonic generation is found at the frequencies, which in the harmonic approximation correspond to the zeros of transmission. An aperiodic (chaotic) response is found mainly in the frequency range close to the resonance of the dangling resonator. Zeros of transmission and total transmissions are shown to be lifted by the anharmonicity nearly in the same frequency region. Higher harmonics are preferentially transmitted at the zero transmission points in the presence of anharmonicity. Received 14 March 2002 / Received in final form 25 November 2002 Published online 14 March 2003