Computational modeling of diffused channel waveguides using adomain integral equation

A domain integral equation is proposed for the computational modeling of diffused channel waveguides. In the modeling the propagation properties and the field distributions of the lower order guided modes are computed. The method is used to design the channel waveguides that are realized by an ion-exchange process in glass substrates. In particular, the method is applied to the design of ion-exchanged waveguides with low fiber/chip coupling losses. The aim is to realize modal distributions in the channel waveguides that closely match the rotationally symmetric field distributions of the HE₁₁ fiber mode. Some technological aspects of the realization of such ion-exchange waveguides are indicated, and various numerical results relevant to the design process are presented     

Numerical modeling of second harmonic generation in opticalwaveguides using the finite element method

A numerical study of second harmonic generation (SHG) in optical waveguides is presented using the finite element method (FEM) and the Crank-Nicholson split-step procedure. Results are given for a Cherenkov radiation scheme in both planar and channel waveguides. Also presented are results obtained on frequency doubling for guided modes in both planar and channel waveguides, using the quasi-phase-matching scheme     

Cerenkov-type second-harmonic generation in KNbO3channel waveguides

Cerenkov-type second-harmonic generation using KNbO₃ channel waveguides produced by MeV He⁺-ion implantation is presented from the viewpoint of device design. We derive the Cerenkov phase-matching condition for multimode waveguides and utilize Cerenkov-angle analysis as a tool for contact-free measurement of the effective indexes of guided modes of ion-implanted KNbO₃ channel waveguides at a wavelength of 860 nm. The measured mode indexes are in full agreement with calculations based on the effective-index method and the refractive index-depth profiles of ion-implanted KNbO₃ waveguides. The efficiency of Cerenkov-type second-harmonic generation is modeled using analytical approximations of the field distributions of the fundamental and the Cerenkov-radiation modes in embedded-channel waveguides. The acceptance width for Cerenkov-type frequency doubling in these ion-implanted waveguides is about one order of magnitude wider than for noncritical phase-matched second-harmonic generation in bulk KNbO₃ crystals. Based on the theoretical simulations, guidelines for optimum device design are given, and the possibility to increase the ultimate conversion efficiency to about 30% W^-1 cm^-1 through lateral-resonance enhancement of the second-harmonic field in KNbO₃ channel waveguides is demonstrated     

A comprehensive analysis of multilayer channel waveguides

Using a simple approach based on the scalar finite element method, propagation characteristics of multilayer channel waveguides are calculated. The effective index, modal field, confinement factor, far-field intensity pattern, and radiation angle of the far-field pattern (full width at half maximum intensity) for multilayer channel waveguides formed with multiple quantum well (MQW) materials and with the MQW materials replaced by a single homogeneous material with the root mean square value of the refractive indexes are compared. Numerical results confirm that the root-mean-square-value approximation, which has been widely used for planar MQW (two-dimensional) waveguides, is useful also for MQW channel (three-dimensional) waveguides with a large number of layers     

Measurement of the birefringence of UV-written channel silicawaveguides by magnetooptic polarization-mode coupling

We report the measurement of the birefringence in integrated-optical waveguides using magnetooptical coupling between the two principal polarizations of the fundamental mode. We demonstrate this measurement technique for directly ultraviolet (UV)-written channel waveguides in silica on-silicon and silica-on-silica. The dependence of the waveguide birefringence on the UV-writing power and UV polarization is investigated. The results are compared with the birefringence of etched waveguides in comparable material systems. An analytical formula for the form birefringence in buried channel waveguides is developed, and measured data are compared with theoretical results     

Cherenkov second-harmonic generation in multilayer waveguidestructures

A model is presented that calculates the features of Cerenkov second-harmonic generation (SHG) in planar dielectric waveguides with an arbitrary index profile. These waveguides are represented by a stack of homogeneous layers of biaxially birefringent media. The model describes type I SHG in channel waveguides within a few approximations, such as the assumption of a quasi-slab channel geometry. Furthermore, this study comprises results of previous step-index models given in the literature, as a particular case of a one-layer structure. These results are in close agreement with measurements of the SHG efficiency in Rb-exchanged erfc waveguides in KTP materials, and in proton-exchanged step waveguides in LiNbO₃ as functions of the pump wavelength     

Optical channel waveguides in silicon diffused from GeSi alloy

A technique for fabricating low-loss and polarisation-independent channel waveguides in silicon is reported. The waveguides are obtained by Ge-indiffusion using either a GeSi alloy or a system of alternating Ge and Si layers. Typical fabrication parameters for single-mode waveguides are given.<>     

A variational finite-difference method for analyzing channel waveguides with arbitrary index profiles

A variational, finite-difference method for computing the normalized propagation constants and the normalized field profiles of channel waveguides with arbitrary index profiles as well as aspect ratios is presented. Mode dispersion curves and the field profiles of the fundamental mode of channel waveguides having profiles of practical interest are included.     

Low loss channel waveguides in polymers

The primary routes for creating polymeric channel waveguides are reviewed. Processes, materials, waveguide performance, and applications recently reported in the literature are covered. Emphasis is on an internal diffusion approach under development at Du Pont which has not been widely reported. The intent is to provide a perspective on the flexibility and versatility for fabricating polymer channel waveguides for practical integrated optic applications     

Mode Converters for Coupling to High Aspect Ratio Silicon-on-Insulator Channel Waveguides

The design, simulation, and experimental performance of mode converters for coupling from single-mode silicon-on-insulator ridge waveguides to high aspect ratio channel waveguides are described. The converters consist of a two-level adiabatic taper structure. The final channel waveguide is 1.5 mum high by 0.8 mum wide. Simulations predict that for total coupler lengths longer than 20 mum, the coupling loss from the fundamental ridge mode to the slit mode is better than -0.2 dB. The couplers and waveguides were fabricated using a two-step self-aligned process. The measured coupling loss for fabricated mode converters is -0.4 dB     

光波导结构对其极化电光效应的影响

本文采用热极化技术在掺锗玻璃条形光波导中诱导出非线性光学效应,并通过变化光波导结构改变极化内电场的大小,研究热极化条件对诱导出的电光效应的影响。研究发现在最佳极化时间内,加入薄SiON层的光波导结构经极化后电光效应积累快,相同极化条件下诱导出的电光系数比原有的条形光波导增大约22%,同时极化光波导还存在一个较低的极化阈值电压。实验结果表明加入光波导结构中的薄SiON层可在一定程度上改变极化光波导内的电荷分布,实现强化其内部电场增大光波导内的非线性光学效应或电光效应的目的。     

Integrated optical beam splitters formed in glass channel waveguides having variable weighting as determined by mask dimensions

Variable-weight beam splitters integrated into glass channel optical waveguides have been fabricated and successfully operated. Variable weighting is achieved by varying mask dimensions. Beam splitting is achieved by introducing notched reflectors of variable size into glass channel waveguides which are formed in shallow grooves having trapezoidal cross sections on silicon substrates. Preferential etching is used to fabricate these grooves and notches. A novel lift-off method incorporating a photoresist, glass, and aluminum sandwich structure is introduced to define glass channel waveguides having smooth edges within the grooves. The extent of the beam splitting notch as determined by scanning electron microscope observation is shown to correspond directly with measured beam splitting ratios for four different ratios. An insertion loss of 0.34 dB is measured for one of the samples.     

Coupled GaAs multiple-quantum-well channel waveguides includingquadratic electrooptic effect

Two coupled channel waveguides using GaAs multiple quantum wells are investigated using an improved coupled-mode theory for anisotropic waveguides and the effective index method. The quadratic electrooptic effect in the multiquantum-well structures is taken into consideration. It is shown that only a moderate electric field for multiquantum-well waveguides is necessary to achieve the optical power switching compared with that required for a bulk GaAs waveguide     

光波导用氟化物玻璃薄膜

系统回顾了光波导用氟化物玻璃薄膜的研究历史,总结了其制备方法与研究现状,重点介绍了氟化物玻璃薄膜在无源光波导和有源光波导上的应用,并对其前景进行了展望.     

Thermal properties of channel optical waveguides based on sol–gel materials

Temperature characteristics of various channel waveguides fabricated using the sol–gel technology are analyzed. It is shown that the limitation of transverse sizes of waveguides leads to significant variations in the temperature characteristics due to field concentration in the sol–gel material of the waveguide, which depends on the type of the channel waveguide and its parameters (geometrical sizes and refractive index of the sol–gel material). Recommendations on the selection of the type of waveguide and its parameters for specific applications in multiplexers, switches, optical cavities, etc. are presented.     

Sol-gel glass waveguide and grating on silicon

This paper reports on the fabrication and characterization of hybrid organic-inorganic glass sol-gel slab and channel waveguides by ultraviolet light imprinting in thin films deposited by a one-step dip-coating process. The adjustment of chemical composition of the materials provides precise selection of refractive index from 1.48 to 1.52 at the wavelength of 632.8 mn. The refractive index of the waveguides at 1.55 μm is similar to that of optical fiber, thus reducing the reflection loss between the two to less than 0.01 dB. The effect of ultraviolet light exposure and heat treatment on waveguide refractive index is studied. Fabrication parameters to produce ridge waveguides are optimized to achieve very smooth side walls. Propagation losses in these waveguides are ~0.1 dB/cm. Single mode buried waveguides, at 1.55 μm wavelength, with circular mode profile are demonstrated     

Single-mode transmission selective integrated-optical polarisers in LiNbO3

Novel low-loss integrated-optical polarisers and analysers are reported for single-mode operation in LiNbO3 waveguides. The operation is based on the polarisation-selective transmission of short proton-exchanged waveguide channels filling discontinuities in Ti-diffused channel waveguides. Extinction ratios exceeding 32 dB are experimentally demonstrated with 0.8 dB excess loss.     

Experimental measurements and theoretical comparisons on the mode size of single-mode Ti∶LiNbO3 optical channel waveguides

The modal characteristics of Ti∶LiNbO₃ optical channel waveguides depend on its fabrication parameters and were determined empirically. The operating wavelength was 1.55μm. Studies and measurements on the mode size of single-mode Ti∶LiNbO₃ optical channel waveguides were made for various fabrication parameters. The two-dimensional mode profiles were studied. The Gaussian and Hermite-Gaussian distributions, which were used to calculate the mode sizes, were good approximations for the lateral and vertical intensity distributions of the channel waveguides respectively. Our experimental results were close to those available from literature.     

Arrayed-waveguide grating with branched outputs for simultaneousmultichannel monitoring purposes

We propose an arrayed-waveguide grating (AWG) that has branched output waveguides for simultaneous multichannel monitoring purposes. The transmittances of two adjacent branched output waveguides are slightly different from each other. Thus, we can obtain crossover wavelengths, where the transmittances of adjacent output waveguides are the same with much smaller insertion losses than those of conventional AWGs. As a result, the proposed device can accurately monitor wavelength-division-multiplexed channel wavelengths in the presence of the amplified-spontaneous-emission noise     

Crosstalk characteristics of lens-like Ti-LiNbO3 intersecting channel waveguides

Crosstalk characteristics of intersecting channel waveguides are presented. Full diffusion times of various Ti film thicknesses are measured first. The concentration distributions in Ti-LiNbO3 crosschannel waveguides are then calculated and compared with the measured distribution. The lens-like medium is the crossover region of crosstalk between ?n and 2?n crosschannel waveguide.