Ion-exchanged Glass Waveguides Research Articles

Potassium and silver ion-exchanged dual-core glass waveguides with gratings

A two-step double ion-exchange process is employed to produce dual-core waveguides in glass. First, potassium ion exchange is carried out at 400 °C. Then, silver ion exchange is performed at 300 °C. The fabricated waveguides have low losses, large single-mode regions, and more symmetrical profiles than single ion-exchanged waveguides. Etched gratings are also made in dual-core waveguides. Very high efficiencies are demonstrated in these waveguides.

Waveguide polarizers with hydrogenated amorphous silicon claddings

We have fabricated TE- and TM-pass waveguide polarizers with polarization isolations of 42 and 35 dB, respectively. The devices were fabricated by the growth of hydrogenated amorphous silicon claddings on K(+)-Na(+) ionexchanged channel waveguides in glass. Cladding thicknesses were accurately tuned to permit optimum coupling of either a TE or a TM mode to the cladding. We have also demonstrated that a waveguide polarizer attenuation as high as 760 dB/cm can be measured by using a photothermal deflection technique.

Examination of two-step fabrication methods for single-mode fiber compatible ion-exchanged glass waveguides

A computer model was used to study important two-step ion-exchange processes for fabrication of singlemode optical waveguides with fiberlike mode field distributions. As a first process step, a field-assisted method was calculated to have a better controllability than a diffusion method. As a second process step, field-assisted burial was found to optimize the coupling loss to fiber to 0.05 dB, but losses lower than 0.2 dB were calculated also for less complex diffusion process steps. On the basis of modeling, a solid state fabrication process was proposed, and the near field distributions of fabricated waveguides were measured to confirm the model.

An evanescent fluorescence biosensor using ion-exchanged buried waveguides and the enhancement of peak fluorescence

The principle of an optical molecular sensor using ion-exchanged buried planar waveguides in glass has been demonstrated. We have shown both theoretically and experimentally that the intensity of the peak evanescent fluorescence can be increased by several orders of magnitude with the use of an index-matching material. The method of differential measurement has been used to improved the differentation between specific and non-specific binding. We used h-IgG (human immonoglobulin G) was the immobilized antibody on the surface of the waveguide and protein A-FITC (fluorescein isothiocyanate) as the fluorescently labelled antigen or anti-antibody to be detected, and have shown that a concentration of protein A as low as 24 n m can easily be detected.

Accurate analysis of ordinary and grating-assisted ion-exchanged glass waveguides

Finite difference and finite element methods, and the coupled mode theory are combined to study in detail the ion-exchanged glass channel waveguides. Ordinary and grating-assisted waveguides are analyzed. The effect of various device parameters on waveguide behavior is investigated. Design curves to make waveguides with required characteristics are provided.

A General Analytical Solution for the Concentration Profiles of Ion-Exchanged Planar Waveguides

ABSTRACTDuring the recent years, a great variety of ion-exchange processes, including one-step or two-step electric field assisted ion-exchange processes, have been developed to fabricate different kinds of passive planar glass waveguides, e.g., surface waveguides, which correspond to surface maximum concentration, or buried waveguides, which correspond to inside maximum concentration [1,2,3]. Theoretical calculation of ionic concentration distribution has been of interest since refractive index is generally a linear function of concentration. A general analytical solution to calculate both surface and buried concentration distributions from different ion-exchange processes, however, has not yet been presented. In addition, traditional ion-exchange has been carried out only with constant surface concentration boundary conditions. Little attention has been paid, either experimentally or theoretically, to ion-exchange processes with variable boundary conditions. In fact, the time-dependent surface concentration is experimentally observed for the ion-exchange of GRIN glass in molten salt bath [4]. Very recently, a novel one-step technique [5,6] involving electric field assisted ion-exchange of Na+ in glass by Ag+ from molten AgNO3 bath with decaying silver concentration has been developed to produce buried Ag+ concentration profiles in glass. As the accurate and reproducible processes are very important for fabricating ion-exchanged glass waveguides, theoretical modeling and analysis on the new process are needed.In this paper, the one-dimensional field-assisted linear diffusion equation has been analytically solved by Laplace transformation to theoretically calculate concentration profiles produced by field enhanced ion-exchange process with exponentially decaying surface concentration boundary conditions. The applications of the solution to a variety of ion-exchange processes with different boundary or processing conditions for optical waveguide fabrication have been discussed. The theoretical results prove that the solution is a general analytical solution which can be used to calculate either surface concentration profiles or buried concentration profiles.

Lateral optical coupling between integrated ion-exchanged waveguides in glass and a-Si-xGex:H photodetectors

Abstract We have integrated ion-exchanged optical waveguides in glass with laterally coupled, amorphous, thin-film photodetectors based on a-Si 1- x Ge x :H. The coupling mechanism between the photodetector and the single-mode waveguide is studied as a function of detector length and polarization of the optical mode. The measurements show a strong polarization-dependent coupling mechanism, thus providing a simple polarization sensor. In addition we have measured the detector response towards a random optical stream of bits.

Simulation of tapered transitions in ion-exchanged channel waveguides

Tapered transitions in the ion-exchanged glass waveguide are modeled to predict the index profile, propagation constant, and modal field along the taper. Results are in excellent agreement with the experimental data in Ag(+)-Na(+) exchanged tapers fabricated by a two-step process in BK7 glass.

Fracture mechanics determination of stress profiles in NaK ion-exchanged glass optical waveguides

Abstract A method based on fracture mechanics rather than on the measurement of the refractive index and birefringence profiles, which determines stress profiles in NaK ion-exchanged soda-lime glass waveguides is presented and discussed. With this technique the stress profile is obtained by measuring the surface stress field by Vickers indentations on waveguides which are progressively HF leached, and the profile is subsequently corrected by considering successive reductions in the thickness.

Potassium ion exchanged glass waveguide directional couplers at 06328 and 13 μm

We describe the fabrication and waveguiding characteristics of potassium ion exchanged single-mode glass couplers at 1.3 and 0.6328 microm.

Nonlinear-optical effects in ion-exchanged semiconductor-doped glass waveguides: erratum

Nonlinear-optical effects in ion-exchanged semiconductor-doped glass waveguides: erratum

Optical behavior of potassium ion-exchanged glass waveguides

Optical waveguides are fabricated by potassium ion-exchange in Fisher Premium and Corning 0211 glass substrates. Variation of the maximum index change and diffusion coefficient with the potassium ion concentration is determined. The propagation loss in the single-mode waveguides is measured. A loss of as low as 0.1 dB/cm is achieved for the waveguides manufactured in Corning 0211 glass. Nearly symmetrical mode profiles are obtained using the one-step diffusion process. The effect of stress on the waveguides is investigated. The implementation of a wavelength selective optical tap and combiner in glass is suggested.

Model for Ion-Exchanged Waveguides in Glass

An analytical model describing refractive index profiles in ion-exchanged glass waveguides is presented. Polarizability, volume, and stress-state changes are accounted for. Index distribution is given in terms of known or measurable physical parameters. Model predictions compare favorably with experimental results of field-assisted ion-exchanged waveguides fabricated in 7740 borosilicate glass. Experimental characterization of the index changes includes prism coupling, microprobe, and photoelastic measurements.

Ion-exchanged glass waveguides: a review

Passive glass waveguides made by ion-exchange technique are potential candidates for integrated optics (IO) applications. The authors review the advantages in the technology as applied to fabrication of useful single-mode structures. Progress in process, fabrication, modeling, and waveguide performance using different monovalent cation systems and glass compositions is described with emphasis on fiber-compatible single-mode structures prepared from molten baths. It is shown how a systematic study allows a correlation between the process parameters and the waveguide characteristics so desirable in assuring reproducible characteristics of the devices.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Effects of Potassium Concentration and Induced Stress on the Refractive Index Profile of K+-Na+Ion-exchanged Glass Waveguides

Abstract An extensive investigation into the optical properties of K+-Na+ ion-exchanged waveguides in soda-lime glass over a wide range of time and temperature is described. From accurate measurements of effective indices, refractive-index profiles and birefringence are obtained, and by use of microalytical techniques (RBS, EDX) ion concentration profiles are measured. Comparison of these profiles allows a quantitative separation of the compositional and the stress optical contributions to the overall change in refractive index; the time behaviour of stress thermal relaxation processes explains the evolution of the profile shape.

Investigation of Refractive-index Profiles of Ion-exchanged Planar Waveguides in Glass

Abstract New data concerning the refractive-index profiles in Ag/Na ion-exchanged waveguides are obtained using a parabolic-segment reconstruction method. The profiles can be described as second-order polynomials, but with a mean curvature b = 2·8 which is significantly greater than the originally suggested value 0·64. The profile so obtained agrees very well with the common diffusion equation for the silver ion concentration only if one assumes a simple linear relationship between the diffusion coefficient and the concentration. This fact necessitates changes in present ideas about the ion-exchange mechanism in sodalime glasses.

Precise control of phase constant of optical guided-wave devices by loading Langmuir-Blodgett films

A Langmuir-Blodgett film is used as a cover layer of single mode waveguide to precisely control the phase constant of the guided-mode. The change of phase constant caused by the cover layer is evaluated by measuring the retardation between the two arms of the ion-exchanged glass waveguide Mach-Zehnder interferometer, a part of which is loaded by Langmuir-Blodgett films. A monolayer of cadmium stearate has varied the phase constant on the order of 10/sup -6/. This method can be used to adjust the phase difference or shift to tune the performance of guided-wave devices such as directional couplers and modulators. >

Process optimization of buried Ag^+–Na^+ ion-exchanged waveguides: theory and experiment

We report optimization of the processing conditions for fabrication of single-mode Ag(+)-Na(+) ion-exchanged waveguides in a soda-lime glass. The surface-index change, the mobility and diffusion coefficient of Ag(+) have been measured at low melt concentrations and the results used for calculation of the index profile using a new simple numerical method for solving the diffusion equation in a two-step process where the index profile is buried by applying an electric field in the second step. The calculated profile is in agreement with that measured. This correlation allows solution of the Helmholtz equation for given process parameters. Single-mode waveguides with desired mode-field distribution have been designed and fabricated with optimized performance and fiber compatibility at 1.3 microm.

Relation between the ordinary and extraordinary index profiles of ion-exchanged glass waveguides

The relation between the ordinary and extraordinary index profiles of ion-exchanged glass waveguides is investigated on the basis of the stress-optic law and the Clausius-Mossotti relation. For K(+) exchange and Ag(+) exchange, the experimental results are consistent with our analysis. The values of the coefficient that relates the ordinary and extraordinary index profiles are presented.

Nonlinear-optical effects in ion-exchanged semiconductor-doped glass waveguides

We have measured nonlinear-optical effects in ion-exchanged channel waveguides fabricated in semiconductor-doped glass. The nonlinearity is manifested as optically induced saturable absorption displaying a resonant enhancement. The relaxation time of the nonlinearity was found to be tens of picoseconds. The relaxation time also exhibited wavelength dependence. Waveguide transmission and pulse-probe experiments using a picosecond mode-locked dye laser were used to carry out these measurements.