Characterization of whispering gallery mode slow light in microspheres

A slow-light system composed by a microsphere resonator and a section of bitapered fiber is characterized theoretically in this article. Theoretical analysis and numerical simulation on the input and output characteristics and the transmittivity of the microsphere resonator were carried out. The directional coupling theory was used to analyze the input/output characteristics of single microsphere resonator and parameters in the overcoupling state, including the relationships between the effective phase shift, transmittivity, effective time delay, light velocity, and the speed of light. The coupling coefficient distance was studied by theoretical analysis and numerical simulation. The theoretical analysis and simulation optimization of the slow-light gyroscope were carried out to obtain the optimized radius of microsphere resonator and distance between microsphere resonator and bitapered fiber. Through theoretical investigation and mathematical simulation, transmission characteristics and time delay mathematical expressions of the microsphere resonator were obtained. Theoretical analysis and simulation of the fiber optic gyroscope sensitivity showed that slow-light improved the accuracy of the interferometric fiber optic gyroscope.     

基于微球腔的回音壁模式激光的最小尺寸研究

回音壁模式(WGM)光学微球腔,因具有传播模式稳定闭合、光能量密度极高、结构简单、易于制备等特点,在微球激光的应用上受到广泛关注.不同物理尺寸的微球腔对应的模式特征也大不相同,这一特性被应用于光学传感器、非线性光学等领域.通过二维时域有限差分法(2D-FDTD)对二氧化硅微球进行理论模拟,分析了球腔在不同模式下的电场分...     

Mapping and manipulating whispering gallery modes of a microsphere resonator with a near-field probe

We report high spatial resolution mapping of high-Q whispering gallery modes in microsphere resonators with a near-field probe. We present experimental results on the effect of Q-factor degradation when the probe interacts with the evanescent field and discuss future applications of our experimental set-up for realization of novel nanolasers and nano light-emitting-diodes.     

Optical switching due to whispering gallery modes in dielectric microspheres coated by a Kerr material

We numerically evaluated the optical responses of a nonlinear microsphere put on prisms, i.e. in prism‐coupling geometry where the incident light excites the WGM through near‐field coupling. As numerical calculations, we employed the finite‐difference time‐domain method taking into account Kerr nonlinearity. The sphere was coated by a Kerr material with 160 nm thick. The third‐order nonlinear susceptibility of the Kerr material χ⁽³⁾ was assumed to be 7 × 10^?14[m² V^?2]. The diameter of the sphere was assumed to be 1 µm. The numerical results have shown that the control and/or the signal lights can induce the optical switching‐like variation in the reflectance. Such a nonlinear response of the sphere has been interpreted by the variation in the dielectric constant of the sphere due to a Kerr nonlinearity.     

Rigorous simulation of nonlinear optomechanical coupling in micro- and nano-structured resonant cavities

A numerical method aimed to predict the optomechanical dynamics in micro- and nano-structured resonant cavities is introduced here. The rigorousness of it is ensured by exploiting the harmonic version of the transformation optics (TO) technique and by considering all the energy-transduction contributions of electrostriction, radiation pressure, photoelasticity and moving boundaries. Since our full-wave approach implements a multi-modal analysis and also considers material losses, from both a mechanical and an optical point of view, a considerable step further has been made in respect to the standard optomechanical perturbative theory. The efficiency and the versatility of the strategy are tested by analysing the optomechanical behaviour of a corrugated Si-based nanobeam and comparing numerical results to experimental ones from the literature.     

基于TDLAS的烟气中CO浓度混合取样式在线监测

燃煤锅炉烟气中不完全燃烧产物CO是燃烧效率监测的重要依据,其存在浓度高、波动剧烈、分布不均匀等特点,采用TDLAS技术中波长调制光谱结合稀释法对烟气中CO浓度进行了混合取样式在线监测。首先基于谐波理论推导出4次谐波与1次谐波免标法测量公式,其次对CO激光器频率调制和光强调制的相位差及电流调谐系数进行了标定,并采用标准气体结合直接吸收法对赫里奥特池光程进行了测量,然后在此基础上对浓度与谐波比值曲线进行了数值计算和实验验证。最后将该装置应用于燃煤电厂,将省煤器出口烟道分为6个区域,各区域安装一个稀释取样探头,在稀释取样过程由于降低了烟气露点无需做除水处理,6路经过稀释后的烟气混合后进入赫里奥特池后实现免标定高精度测量。该监测装置实现了连续稳定运行,运行中使用Testo350便携式分析仪与现场测量数据进行了对比,二者测量结果一致,误差小于1×10~(-6)。