Sputtered-glass optical waveguides

Research into low-loss optical-frequency planar waveguides has produced a technique for controlling the propagation characteristics during the sputter-deposition process. The basis of the technique is discussed, and some results are given.     

Low-loss Na-glass waveguides

A new method for the fabrication of low-loss Na-glass waveguides on SiO2has been found. The reglassification process has enabled us to reduce the scattering loss in the planar waveguide to less than 1 dB/cm and to obtain channel waveguide with 2 dB/cm attenuation by the lift-off method or by the direct laser writing method.     

Equivalent optical waveguides

We develop a comparison method which identifies a waveguide with properties that are well known and are very similar to the one under investigation. It has a very simple mathematical basis which allows a trivial derivation of the moment method for circular cross-sectional fibers includingW-fibers, and an extension to noncircular optical waveguides. We first use the scalar approximation, and then extend to the full vector theory which accounts for polarization. Our concern is with fundamental mode propagation constants and higher mode cutoffs.     

Hollow-core silica waveguides

Measurements have been made of the transmission at 10.6 μm of the HE11mode in hollow silica waveguides of 1.04 and 2 mm bore diameters in both straight and bent configurations. Transmission losses of the straight waveguides were found to be 1.91 and 0.69 dB/ m, respectively. The experimental results have been compared to the predictions of the theoretical treatments available. Experimental bend losses show a linear rather than square-law dependence on curvature for all but the smallest curvatures studied.     

Ultra-low-loss polymer waveguides

Single-mode perfluoropolymer waveguide structures exhibiting a polarization-independent ultra low loss of <0.05 dB/cm at 1310 nm and <0.07 dB/cm at 1550 nm with a /spl Delta/n of 1.6% have been fabricated for the first time. These new low-loss structures indicate relatively high-power-handling reliability at 1310 and 1550 nm. Based on this, a highly efficient arrayed-waveguide grating multi-demultiplexer with a crosstalk of 30/spl plusmn/2 dB and an insertion loss of 2.8/spl plusmn/0.3 dB is realized.     

Circular sectoral waveguides

Hollow cylindrical waveguides that have pie-shaped cross sections are described. The explicit equations for the field components of the TE (transverse electric) and TM (transverse magnetic) waves are given, and the modal patterns for a number of modes are plotted. The relation between the field distributions inside the circular and sectoral waveguides is discussed. It is shown that the electric and magnetic fields of the modes TE_1n and TM_1n display edge singularity when the sectoral angle is greater than π. Formulas convenient for the evaluation of Bessel functions of fractional order on a personal computer are given     

Sandwich-ribbon optical waveguides

The preparation of composite-glass-ribbon optical waveguides is described, of which the guiding layer is a thin rectangular filament of lead glass, supported by a soda-lime-glass substrate. Single-mode and multimode guides have been made, and their mode-transmission properties observed.     

Vertically integrated silicon-on-insulator waveguides

A SiO₂-Si-SiO₂-Si-SiO₂-Si structure produced by the separation by implantation of oxygen (SIMOX) process used for dual vertically integrated waveguiding in silicon at λ=1.3 μm is discussed. Independent waveguiding is observed when 2-μm-thick Si cores are separated by 0.36-μm-thick SiO₂ . Coupled waveguiding is found for an 0.12-μm intercore oxide thickness     

Field-realigned nematic-liquid-crystal optical waveguides

An external electric field exerts volume torque on the nematic liquid crystal due to the anisotropic molecular polarizability and tends to reorient the molecular axes. Phase-velocity tuning in these materials is thus possible. Eigenmodes of thin-film liquid-crystal waveguides are analyzed by a numerical method. A three-layer model of the waveguides is found to be in good agreement with the measured data, thus providing a simplified model for conceptual thinking as well as for computation.     

AlGaAs/GaAs-ARROW waveguides

The first demonstration of a passive vertical antiresonant reflecting optical waveguide (ARROW) realised in the AlGaAs/GaAs material system is reported. Losses of 2.6 dB/cm for the TE- and 3.5 dB/cm for the TM-ARROW modes were obtained at a wavelength of 0.83 mu m for samples with 4 mu m-wide ridges.<>     

Erbium-doped fluoride glass waveguides

When calling for compact green laser sources, the green upconversion emission of IR pumped erbium-doped fluoride glass waveguides opens up a technologically and economically superior alternative to complex and costly frequency doubling techniques. Therefore, fluoride glass planar waveguides were fabricated with thicknesses down to 29 μm and a scattering loss of 0.1?0.2 dB/cm.     

Diaphragms in evanescent waveguides

Three diaphragms are considered (capacitive, inductive and tuned window) on a storage-energy basis to determine whether there is any change in the behaviour of these in evanescent guides. It is found that all three are inductive when a guide is operated below the H10 cutoff.     

Graded-index planar dielectric waveguides

Properties of planar dielectric waveguides having a diffusion-induced index of refraction distribution are investigated. It is found that the spatial distribution of modes, group velocity, and mode spectrum of these guides differed qualitatively from the corresponding properties found in a slab waveguide. These results were experimentally verified by measuring the mode spectrum of a dielectric waveguide having an assumed complimentary error-function distribution of refractive index.     

Spinor formalism for waveguides

The authors first prove that there exists a close relationship between the spinor fields and the electromagnetic transverse fields TE, TM.Then the spinor formalism is applied to the waveguide theory and explicit formulae are given for waveguides with rectangular or circular cross section. An interesting feature of the spinor formalism is to require only two components.     

Mode-propagation in optical waveguides

The modal fields and propagation coefficients of a 4-region optical waveguide with diffused boundaries are determined using conventional perturbation theory.     

Photochromic waveguides and fibres

We have fabricated and tested channel guides and fibres made from photochromic glasses. The temporal response and the spectral response to UV radiation suggest that the fibres may be useful for monitoring processes involving UV irradiation.     

Beam-propagation in magnetooptic waveguides

The propagation of modes in magnetooptic waveguides distinguishes between the forward and the backward direction. This effect is applied to the realization of integrated optical isolators and circulators. The paper presents a finite-difference beam propagation simulation of such devices. Two different directions of the waveguide magnetization are considered. Finally, some consequences with respect to the practical realization of nonreciprocal integrated optical components are discussed     

Strip-loaded diffused optical waveguides

A strip-loaded diffused optical waveguide consists of a one-dimensional diffused guide with a narrow loading strip of dielectric deposited on the surface. Two-dimensional modes can exist in the diffused material, confined in depth by the diffusion and in width by the loading strip. The propagation constants of these two-dimensional modes are calculated. The requirements for the index of refraction and width of the loading strip are discussed along with the rate of decay of electric-field amplitude away from the strip. A numerical example typical of Ti-diffused LiNbO3is given.     

Measurement of the coupling efficiency between dielectric-loaded rectangular waveguides and dielectric-loaded trough waveguides

The measurement of the coupling efficiency between a dielectric-loaded rectangular waveguide and a dielectric-loaded trough waveguide is described, and the results are compared with theoretical estimates.