Theoretical expression for change of extraordinary refractive index in annealed proton exchanged LiNbO3 optical waveguides

A general expression for the change in extraordinary refractive index of the annealed proton exchanged LiNbO₃ waveguide has been deduced. The expression deduced explains the experimental results of decrease in change of extraordinary refractive index with annealing. The effect of annealing time has also been incorporated following Cao's model (Cao, Ramaswamy, Srivastava, J. Lightwave Technol. 10 (1992) 1302–1313). The concentration profile of protons in the annealed waveguide has been deduced theoretically, which is consistent with the previous results. The spontaneous polarization has been considered as the central mechanism for change in extraordinary refractive index due to proton exchange with annealing.     

A full-wave three-dimensional analysis of open dielectric waveguides and periodic structures using an equivalent network model

An accurate fully vectorial wave analysis to calculate the propagation characteristics and field distribution of open dielectric waveguides and optical integrated circuits is presented. Based on the periodic repetition concept and using an equivalent network model, a method to analyze wave propagation in these guides is developed, which is able to take the simultaneous presence of mixed polarizations into account. Compared with conventional approaches like mode matching as well as with other numerical methods, the presented three-dimensional (3D) method shows individual advantages like accuracy, simplicity, and numerical efficiency. To show both validity and usefulness of this approach, some fundamental structures are investigated and the obtained numerical results are presented.     

渐变折射率光波导转折点外指数衰减场的推导

证明了渐变折射率光源导转折点外的模场呈简单的指数衰减形式,指数衰减系数可用一恒定的等效折射率定义。     

Analytical approximation solutions for 3-D optical waveguides: Review

The rectangular dielectric waveguide is the most commonly used structure in integrated optics, especially in semi-conductor diode lasers. Demands for new applications such as high-speed data backplanes in integrated electronics, waveguide filters, optical multiplexers and optical switches are driving technology toward better materials and processing techniques for planar waveguide structures. The infinite slab and circular waveguides that we know are not practical for use on a substrate because the slab waveguide has no lateral confinement and the circular fiber is not compatible with the planar processing technology being used to make planar structures. The rectangular waveguide is the natural structure. In this review, we have discussed several analytical methods for analyzing the mode structure of rectangular structures, beginning with a wave analysis based on the pioneering work of Marcatili. We study three basic techniques with examples to compare their performance levels. These are the analytical approach developed by Marcatili, the perturbation techniques, which improve on the analytical solutions and the effective index method with examples. T Srinivas received the B.Sc. (Hon.) degree from Nehru Science College, Hydrabad and M.E. (Int.) and Ph.D. dgrees from the Indian Institute of Science, Bangalore, India. He was a Postdoctoral Research Fellow at Toyohashi University of Technology, Japan from 1992 to 1996. He is currently an Associate Professor with the Department of Electrical Communication Engineering, Indian Institute of Science. His areas of interests are optical communication networks, integrated optics, micro-opto-electrical-mechanical systems (MOEMS) and fiberoptic sensors     

光子晶体波导定向耦合型1×3光分束器

将五光子晶体单模波导平行、邻近放置构成定向耦合器,依据自映像原理,数值分析了输入光场对称入射时,该系统中光的传播行为.基于此结构,设计了1×3光分束器,其器件长度可短至14.26μm.仅仅通过对称地改变耦合区中两个介质柱的有效折射率,使光场在横向发生重新分布,便可实现输出能量的均分或自由分配.通过非对称地改变耦合区中的一个介质柱,可实现3个输出端的输出能量的自由分配.该光分束器具有微小尺寸和各输出端输出能量的比例可自由调制的特点,在未来集成光回路中具有广泛的应用价值.     

An Approximate Theoretical Model of Surface Plasmon Resonance Optical Waveguide and Fibre-optic Sensors

Optical surface plasmon resonance (SPR) excitation can be theoretically depicted and discussed using Fresnel’s equations. However, Fresnel’s equations cannot explicitly give expressions to reflect the characteristics of SPR systems, especially in SPR optical waveguide and fibre-optic sensors. In this paper a mathematical model based on the approximation proposed by Kretschmann in bulk optics is presented to describe the characteristics of SPR optical waveguide and fibre-optic sensors. The results show that the model keeps high accuracy when used in the area close to the minimum reflection, at which the resonance condition is achieved. This model can be used to analytically estimate the performance of SPR optical waveguide sensors, and SPR fibre-optic sensors in meridional rays approximation.     

Emanation thermal analysis study of a sol-gel precursor for silica-titania waveguides

Emanation Thermal Analysis (ETA) was demonstrated as a tool for the characterization of microstructure changes of a sol-gel precursor for silica-titania layers deposited on the glass plate to be used as planar waveguides. Temperature ranges of 280-330 and 380-500°C, respectively, in which the densification of the layers took place, were determined by ETA under in situ conditions of the sample heating. Results of thermogravimetry were compared with the ETA data. This revised version was published online in August 2006 with corrections to the Cover Date.     

Rapid Prototyping of Low‐Loss IR Chalcogenide‐Glass Waveguides by Controlled Remelting

A method for fabricating infrared‐transmitting waveguides that yields low optical losses and strong confinement of light is presented. The method minimises the number of fabrication steps by exploiting the photosensitivity of arsenic trisulfide glass, using it both as a photoresist and as a waveguiding material. Controlled annealing/remelting of the waveguides minimises scattering due to fluctuations in refractive index at the interface between the waveguide and the surrounding medium, allowing low losses to be realised. Bends and Y‐splitter structures have been realised, as well as the longest As₂S₃ serpentine planar waveguides yet reported.     

Optical sensing in microfluidic lab-on-a-chip by femtosecond-laser-written waveguides

We use direct femtosecond laser writing to integrate optical waveguides into a commercial fused silica capillary electrophoresis chip. High-quality waveguides crossing the microfluidic channels are fabricated and used to optically address, with high spatial selectivity, their content. Fluorescence from the optically excited volume is efficiently collected at a 90° angle by a high numerical aperture fiber, resulting in a highly compact and portable device. To test the platform we performed electrophoresis and detection of a 23-mer oligonucleotide plug. Our approach is quite powerful because it allows the integration of photonic functionalities, by simple post-processing, into commercial LOCs fabricated with standard techniques. Figure Femtosecond laser written waveguides can selectively excite fluorescence in a microfluidic channel of a commercial lab-on-a-chip. A compact scheme for on-chip detection by laser induced fluorescence is applied to capillary electrophoresis of a 23-mer Cy3-labeled oligonucleotide