共查询到20条相似文献,搜索用时 15 毫秒
1.
Venkata Ramanaiah Dantham Prem Ballabh Bisht Pramod Singh Dobal 《Journal of Raman spectroscopy : JRS》2011,42(6):1373-1378
Raman spectra and fluorescence of BaTiO3 and silica microspheres of different sizes have been studied. The observed whispering gallery modes (WGMs) have been assigned using theoretical simulations based on the Lorenz–Mie theory. The WGMs are found to have selective enhancements in the Raman spectra. The variations in the Raman spectra with the radial position of the excitation spot and excitation wavelength have been correlated with the morphology‐dependent internal field distributions of the microspheres. The effect of a thin dye coating on the fluorescence and Raman spectra was studied, and a coating thickness of ∼200 nm was estimated from the theoretical simulation of experimentally observed data based on the Aden and Kerker theory. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
2.
Analytic approach to dielectric optical bent slab waveguides 总被引:1,自引:0,他引:1
K. R. Hiremath M. Hammer R. Stoffer L. Prkna J. Čtyroký 《Optical and Quantum Electronics》2005,37(1-3):37-61
A rigorous classical analytic frequency domain model of confined optical wave propagation along 2D bent slab waveguides and curved dielectric interfaces is investigated, based on a piecewise ansatz for bend mode profiles in terms of Bessel and Hankel functions. This approach provides a clear picture of the behaviour of bend modes, concerning their decay for large radial arguments or effects of varying bend radius. Fast and accurate routines are required to evaluate Bessel functions with large complex orders and large arguments. Our implementation enabled detailed studies of bent waveguide properties, including higher order bend modes and whispering gallery modes, their interference patterns, and issues related to bend mode normalization and orthogonality properties. 相似文献
3.
以熔融淬冷法自制了Tm~(3+)掺杂Ge-Ga-S硫系玻璃,并以此为基质材料,用漂浮粉料熔融法制备了直径分布为50—200μm的高品质因数(Q10~4)的有源硫系玻璃微球谐振腔.在显微镜下优选出一颗表面质量好、球形度较高、直径为72.84μm的微球,与氢氧焰扫描拉锥法制备的一根腰锥直径为1.93μm的石英光纤锥进行近场耦合.根据基质材料的吸收光谱特性,选用808 nm的半导体激光器作为抽运源.实验测得光纤锥倏逝波场激发出了掺Tm~(3+)硫系玻璃微球在1460 nm附近的荧光回廊模式,其典型共振峰间隔为4.39 nm.实验测得的荧光回廊模式与米氏散射理论计算结果符合度较高(最大误差仅为0.047%),验证了本文提出的掺Tm~(3+)硫系微球制备及耦合工艺的可行性. 相似文献
4.
Christian Caville 《Fiber and Integrated Optics》2013,32(4):263-279
In pigtailed optoelectronic modules, a major source of optical coupling loss due to thermal or mechanical deformations of the assemblies is the stress exerted on the fiber in the package between its holding points. The stresses exerted on the fiber, the resulting strains on the holding points, and the risk of fiber fracture are examined using analytical models on the deformations undergone by the fiber. Optimization of fabrication assembly technology with regard to the risks of fiber fracture and optical coupling losses represents a tradeoff between these two risks. 相似文献
5.
《Laser \u0026amp; Photonics Reviews》2017,11(2)
This work takes inspiration from chemistry where the spectral characteristics of the molecules are determined by hybridization of electronic states evolving from the individual atomic orbitals. Based on analogy between quantum mechanics and the classical electrodynamics, we sorted dielectric microspheres with almost identical positions of their whispering gallery mode (WGM) resonances. Using these microspheres as classical photonic atoms, we assembled them in a wide range of structures including linear chains and planar photonic molecules. We studied WGM hybridization effects in such structures using side coupling by tapered microfibers as well as finite difference time domain modeling. We demonstrated that the patterns of WGM spectral splitting are representative of the symmetry, number of constituting atoms and topology of the photonic molecules which in principle can be viewed as “spectral signatures” of various molecules. We also show new ways of controlling WGM coupling constants in such molecules. Excellent agreement was found between measured transmission spectra and spectral signatures of photonic molecules predicted by simulation.
6.
Whispering gallery modes in intrinsic TiO2 microspheres coupling to the defect‐related photoluminescence after visible excitation 下载免费PDF全文
Defect‐caused visible photoluminescence after visible excitation in anatase TiO2 microresonators couples to whispering gallery modes (WGMs). Spherical anatase TiO2 of a radius between 1.5 µm and 4 µm have been prepared by a sol–gel technique based on hydrolysis of titanium tetrabutoxide. The observation of WGMs in intrinsic anatase TiO2 without additional dopant offers new perspectives for the localisation of light at TiO2 surfaces for the design of photocatalysts.
7.
8.
The notion that Stimulated Brillouin Scattering (SBS) is primarily defined by bulk material properties has been overturned by recent work on nanoscale waveguides. It is now understood that boundary forces of radiation pressure and electrostriction appearing in such highly confined waveguides can make a significant contribution to the Brillouin gain. Here, this concept is extended to show that gain enhancement does not require nanoscale or subwavelength features, but generally appears where optical and acoustic fields are simultaneously confined near a free surface or material interface. This situation routinely occurs in whispering gallery resonators (WGRs), making gain enhancements much more accessible than previously thought. To illustrate this concept, the first full‐vectorial analytic model for SBS in WGRs is developed, including optical boundary forces, and the SBS gain in common silica WGR geometries is computationally evaluated. These results predict that gains 104 times greater than the predictions of scalar theory may appear in WGRs even in the 100 μm size range. Further, trapezoidal cross‐section microdisks can exhibit very large SBS gains approaching 102 m−1W−1. With resonant amplification included, extreme gains on the order of 1012 m−1W−1 may be realized, which is 108 times greater than the highest predicted gains in linear waveguide systems.
9.
Motoki Asano Yuki Takeuchi Weijian Chen ahin Kaya
zdemir Rikizo Ikuta Nobuyuki Imoto Lan Yang Takashi Yamamoto 《Laser \u0026amp; Photonics Reviews》2016,10(4):603-611
In this work, we report optomechanical coupling, resolved sidebands and phonon lasing in a solid‐core microbottle resonator fabricated on a single mode optical fiber. Mechanical modes with quality factors (Qm) as high as 1.57 × 104 and 1.45 × 104 were observed, respectively, at the mechanical frequencies and . The maximum Hz is close to the theoretical lower bound of 6 × 1012 Hz needed to overcome thermal decoherence for resolved‐sideband cooling of mechanical motion at room temperature, suggesting microbottle resonators as a possible platform for this endeavor. In addition to optomechanical effects, scatter‐induced mode splitting and ringing phenomena, which are typical for high‐quality optical resonances, were also observed in a microbottle resonator.
10.
通过CO2激光器熔融不同直径的熔锥光纤以得到相应直径的石英玻璃微球,利用此微球和熔锥光纤,构造了球微腔耦合系统。实验中利用光腰直径为3.1μm的熔锥光纤与直径为143.1μm的石英玻璃微球进行耦合,通过最大分辨力为1pm的可调谐半导体激光器对该耦合系统进行光谱扫描,发现石英玻璃微球的吸收光谱中出现分立的结构共振峰。利用光学微球腔理论讨论了石英玻璃微球吸收光谱中的结构共振,并用米氏散射理论公式对一阶TE模共振峰的位置以及它们的间隔进行了计算,共振峰位置实验结果与理论结果的误差仅为0.03%,表明实验与计算结果相符。 相似文献
11.
Due to the broad scattering spectral profiles, localized surface plasmon resonances (LSPRs) of Pd nanoparticles have low resolution and limited sensitivity for hydrogen detection. In this work, we use a simple light‐irradiation method to demonstrate that free‐space light can be efficiently coupled into and from the microfiber whispering‐gallery modes (WGMs) by the Pd nanoantennas. The nanoantenna–microfiber cavity system provides strong intermodal coupling between LSPRs and WGMs, and induces significant modulation of the scattering spectra. A measured full width at half‐maximum of 3.2 nm at 622.7 nm is obtained, which is the narrowest in Pd nanoparticle‐based LSPR structures reported up to now. The ultranarrow resonances offer enhanced sensitivity to hydrogen gas detection with a figure of merit reaching ∼2.22. Other advantages of the Pd nanoantenna–microfiber cavity system including independence of precise alignment of excitation light, large tunability of the resonant wavelengths, easy and low‐cost fabrication of the system, have also been demonstrated.
12.
Antireflection coatings based on dielectric nanosphere arrays are discussed in application to photovoltaic materials including silicon and gallium arsenide. Macro‐ and nanoscale characterizations and finite‐difference time‐domain calculations are performed, and demonstrate the enhanced optoelectronic properties. A significant absorptivity enhancement is achieved due to the collective resonant coupling of excited whispering gallery‐like modes and thin‐film interference effects. The resonant coupling is masked in macroscale measurements by the size variation of nanospheres, but it is clearly seen through imaging photocurrent at the nanoscale with near‐field scanning photocurrent microscopy. The resonant coupling can be effectively tuned by the material, configuration, or size of nanospheres. Hybrid coatings combining nanospheres of different materials yield the highest efficiency gain of more than 30%. The impact of manufacturing defects, such as double layer formation, is also evaluated. While the performance degrades, the antireflection coating still offers marked improvement in comparison with bare cells. 相似文献
13.
Coupled-resonator-induced transparency in two microspheres as the element of angular velocity sensing 下载免费PDF全文
We proposed a two-coupled microsphere resonator structure as the element of angular velocity sensing under the Sagnac effect.We analyzed the theoretical model of the two coupled microspheres,and derived the coupled-resonatorinduced transparency(CRIT) transfer function,the effective phase shift,and the group delay.Experiments were also carried out to demonstrate the CRIT phenomenon in the two-coupled microsphere resonator structure.We calculated that the group index of the two-coupled sphere reaches n_g = 180.46,while the input light at a wavelength of 1550 nm. 相似文献
14.
15.
采用粉料漂浮高温熔融法自制Nd3+掺杂硫系玻璃微球,研究了腔量子电动力学增强效应对稀土掺杂硫系玻璃微球荧光光谱的影响。把直径90.53μm的硫系玻璃微球与锥腰直径1.02μm的石英光纤锥耦合,将808nm抽运激光导入微球,荧光光谱存在分立的共振峰。根据米氏散射理论公式,计算得到TE偏振态下基模的三个共振峰位置,确定了这三个共振峰的模式序数。增强因子η≈1122,这表明微球荧光自发辐射速率增强幅度为1122倍。在基模条件下对原增强因子公式进行近似化简,并利用近似公式进行估算得到η≈1167,误差为4%。 相似文献
16.
本文提出利用染料掺杂液晶填充PI光控取向膜毛细管获得可调谐激光.采用532 nm YAG倍频脉冲激光器抽运,实验及理论研究了有聚酰亚胺(PI)取向膜和无PI取向膜毛细管的激光发射特性,对比分析了两种情形的激光产生阈值以及随温度变化的特性.结果表明:经PI光控取向处理的染料掺杂胆甾相液晶毛细管的激光发射模式具有分布反馈模式和回音壁模式,同时,激光产生阈值为4.5 m J·mm~(-2);发现当温度升高时,发射光谱发生"蓝移",中心波长调谐范围为5.9 nm,温度升高到43℃时,形成质量非常好的回音壁模式,其自由光谱范围为1.05 nm.经PI光控取向处理的染料掺杂向列相液晶激光发射模式为随机激光,并且较无PI取向时激光发射峰减少. 相似文献
17.
18.
To deal with the radiation from an axially symmetric pillbox resonator embedded in LiNbO3 substrate, an eigenvalue equation is derived from the expression of the finite-element beam propagation method in a cylindrical coordinate system. By solving the eigenvalue equation iteratively, the field distributions and the angular phase constants of the pillbox resonator are evaluated. The iterative scheme of solving the eigenvalue equation is an extension of our previous direct solution method which was described for a lossless case. The results obtained by this method are compared with those obtained analytically, and excellent agreement is found. 相似文献
19.
20.
Kenzo Yamaguchi Masamitsu Fujii Tadanobu Niimi Masanobu Haraguchi Toshihiro Okamoto Masuo Fukui 《Optical Review》2006,13(4):292-296
A micrometer-sized nonlinear optical resonator constituted of a silica microsphere coated with J-aggregates has been fabricated
by the sol-gel process. We determined the scattering light spectrum and discuss the application of the observed effect for
the realization of an optical switching element. Optical evaluation of the sphere has been performed in the attenuated-total-reflection
(ATR) configuration. We excited a whispering gallery mode and measured the nonlinear ATR signal dependence on excitation intensity.
The experimental result agrees very well with the simulation results obtained using the Mie theory and the finite-difference
time-domain method taking into account optical Kerr nonlinearity. The permittivity of the film of J-aggregates was measured
by ATR method at several wavelengths and the value at the desired wavelength was determined by extrapolation using the Lorentz
function. 相似文献