LiNb03 crystals have been grown from various melt compositions and with a Mg0 doping up to 9 mol%. For the first time the Li:Nb ratio was estimated by chemical analysis of the Li content in the grown crystals. Doping with Mg0 leads to a decrease of the Li20 content with higher Mg0 content. The Curie temperature was measured for doped and undoped crystals.

Integrated optoelectronic devices are key components in fiber optic communication, sensor, and network systems (1,2,3). Integrated optoelectronic waveguide devices have been fabricated in a variety of substrates such as glass, silicon, compound semiconductors, and electro optic crystals. Compound semiconductors have shown promise in the fabrication of laser diodes and detectors and possibly even monolithic integration of optoelectronic components. Materials such as glass and silicon have the potential to yield low cost and low performance multimode coupler and interconnect devices. The electro optic property of LiNb03 makes it attractive for applications in optical switching and modulation in single mode optical fiber communication and sensor systems. Numerous research papers have been written in the last fifteen years outlining the performance of LiNb03 based devices. Typical devices are a)phase modulator, b)amplitude modulator, c)switch. These devices depend on the electro optic effect in which the application of an external field changes the refractive index in the crystal and thereby modulates the phase of the guided beam in the waveguide. There are manufacturing problems to be solved before these devices can become a commercial reality. The manufacturing technology for these devices utilizes microfabrication methods developed for silicon integrated circuits and as a result has the potential to yield low manufacturing costs due to the economy of mass producing these devices in a 3 inch wafer.

A detailed experimental study has been made of the transmission of Ti:LiNb03 waveguide bends formed from circular arc sections. The effects of varying modal confinement and bend radius in compact areas have been identified.

Tolerances in the process technology of planar electrooptical wave guide device on LiNbO3 are described with emphasis on pattern generation for switching modules of higher complexity.

This presentation gives new results on single-mode planar and stripe waveguides on both lithium tantalate and lithium niobate formed by proton-exchange. The largest Δneff obtained on lithium tantalate are 0.0174 on x-cut and 0.0033 on z-cut respectively. Results on in-plane scattering, insertion loss and of microanalysis will be reported.

In this paper the variation of the modal propagation constant and attenuation of He+ implanted optical waveguides in LiNbO3 are presented and shown to be due to the variation of confinement and scattering of the propagating modes.

Cs4-ion-exchange in glass is compared with the commonly used K+-, Ag+- and T1+-ion-exchange in glass in the process of waveguide fabrication. It will be shown that the Cs4-ion-exchange in the special substrate glass BGG21 represents an alternative method. As in the case of Ag+ AND T14 it is possible to fabricate buried waveguides by a double ion-exchange. The field-assisted ion-exchange is preferred due to the low CO+-ion mobility.

Ion exchange experiments with both commercially available and special newly developed glasses have been performed in order to fabricate passive multimode waveguide components for optical fiber communication. Using the photolithographic process strip waveguides and y-branches have been formed. The refractive index profiles have been measured by a modified refracted near-field (RNF) method.

The losses of curved waveguide structures have been analyzed with respect to optimal S-bend design. Directional couplers consisting of curved waveguides fabricated by ion-exchange in glass have been investigated. A theoretical model for the coupling ratio with good agreement to the experimental results has been derived.

The coupling ratio of asymmetric monomode ring coupler fabricated by a field assisted potassium ion-exchange in BK7 glass is investigated experimentally. The behaviour of the coupler is simulated by means of the Beam Propagation Method. The experimental results are fitted by an approximating formula.

Two-dimensional refractive-index profiles of Ag+-Na+-ion-exchanged single-mode channel waveguides in glass for use in the 1200 nm-1600 nm wavelength region are determined from reflectivity measurements scanning their polished endface. Measurements of propagation constants, near fields and far fields at different wavelengths are used to control and improve the results.

Waveguiding devices, like modulators and switches, realized with InGaAsP lattice matched to InP are discussed. Basic phenomena, such as optical absorption, electro- and elasto-optic effect as well as the impact of free carriers on absorption and refractive index, are considered and described in their use with actually realized devices. Whereas the optical absorption seems not to be a main obstacle, the relatively large length of the devices will restrict their employment to the most essential functions.

The extending use of single-mode fibers has stimulated research on guided-wave optical devices. Since most of basic components have been demonstrated in III-V semiconductors, an increasing effort is now devoted towards monolithic integration. Recent progress in the propagation loss of waveguides and in laser to waveguide coupling are significant steps in this way.

The vapor phase epitaxy has been used to realize a number of new GaAs and InP waveguide structures. Among them, the inverted rib structure has been used in order to fabricate GaAs homojunction phase modulators. The structures have been analyzed with two-dimensional numerical methods, allowing for an accurate modelling and optimization of the device. The potentialities of similar heterojunction phase modulators for both the GaAs and InP systems are discussed.

Guided wave structures with directional changes will undoubtedly be required for integrated optical circuits. Reflections off an etched vertical wall are used to provide promising low loss bends.

The generation of phase-shifted gratings in InP for DFB lasers by holographic double exposure is described. The method is also suited for maskless laser activated etching. An estimation of the DFB laser threshold as compared to the ideal phase-shifted grating with constant amplitude is given.

We describe the planar technology used on silicon substrate to achieve two special devices : a folded optical spectrum analyser featuring 500 MHz bandwith and a Michelson interferometer used as a vibration sensor.

Planar optical waveguides were fabricated on glass and fused silica substrates using soluble polyimides. With "as dried" samples total loss values of 0.3 dB/cm were obtained. Evaporation of solvents can be done without affecting the loss values significantly. The influence of curing procedures on the optical properties of the polymer films is discussed. For the low temperature region (< 100°C) a method of producing refractive index patterns within the polymer film via UV lithography is introduced. Finally planar polyimide light-guides on a ceramic substrate with silicone as a cladding layer were demonstrated, with loss values < 1.3 dB/cm.

A new structure using strip-loaded waveguides is proposed for TIR switches with PLZT thin films. The TIR switches realized high-speed intensity modulation of LD light (0.83 μm) at 2 GHz. The modulation bandwidth of the lumped-constant electrodes and the traveling-wave electrodes was 7.1 GHz and more than 26.5 GHz, respectively. The modulation bandwidth is estimated to be more than 100 GHz.

A simple model to describe the propagation of light through a nematic liquid crystal cell is introduced. Experimental measurements are presented of the intensity (arbitrary units) of the light transmitted through a twisted nematic cell mounted between crossed or parallel polaroids as a function of the voltage amplitude (0-10 V pk-pk) of the square wave signal (1 KHz) used to activate the cell.

Planar lightguides have been fabricated from mixtures of the polymer PMMA with benzoin type photoinitiators. Using conventional UV-photolithography 2 dimensional refractive index patterns were recorded in the polymer films. Thickness and refractive index of the organic lightguides were determined by m-line spectroscopy. The achieved refractive index changes increased with increasing photoinitiator concentrations. For high concentrations (< 70 %) the film refractive index could be increased via UV exposure by Δn = 0.03. Thermal treatment at below 100°C caused the out diffusion of the unexposed photoinitiator and completion of the photochemically induced reaction in the exposed parts of the film. Thus refractive index patterns (Δn < 0.05) could be developed and fixed.

The design and fabrication of IO-switching matrices, polarization independent modulators and star couplers for application in a local optical communication network is presented.

The general solutions of partial differential equations contain arbitrary functions equivalent to an infinite set of constants. For boundary problems in which the boundary does not coincide with curves or surfaces of a coordinate system in which the partial differential equation is separable into ordinary differential equations, these constants may be used to satisfy the given physical boundary condition on arbitrary given boundary curves and interfaces. Thus it is possible to calculate wave propagation and eigenfrequencies of straight and bent glass fibers and wave-guides of various cross sections like Cassinian curves etc.

Co-directional coupling between modes with different velocities can be used to realise an optical filter. This paper shows that a spatially-variant coupling can be designed such that the frequency response has desirable characteristics, for example good sidelobe suppression. The method exploits the fact that the impulse response has finite duration.

Phase-matching methods for improving the bandwidth of travelling-wave optical modulators are compared with the aid of an accurate model, the validity of which is confirmed by experiment.

An analysis is given of phase reversal electrode structures used for phase matching in travelling-wave integrated optic phase modulators. Both modulus and argument of the phase shift are obtained; both are required for applications involving broadband excitation. Periodic and non-periodic, lossy structures are treated and the advantage of non-periodic structures for wide band operation is demonstrated. Optimum structure arrangements and upper bounds to phase shift and figure of merit are derived.

Electrooptic devices on LiNb03 are modelled including buffer layers in terms of technological parameters and are analysed by BPM simulations. Calculated switching characteristics for switches in LiNbO3 are presented, and they are compared with experimental results.

The operational principles of passive and active LiNb03 waveguide crossings are outlined. The radiation losses and crosstalk in large-angle passive waveguide crossings are calculated using the beam-propagation method. A detailed electrode analysis of an electrooptic X-switch is presented and compared with that of a directional coupler switch.Prospective applications of waveguide crossings are listed. As an example, the parameters of an integrated 4x4 switching array with 16 X-switches are presented.

The operating principles and performance of waveguide Mach-Zehnder frequency translators suitable for use in coherent optical fibre systems are described. The performance of a coherent optical fibre system transmitting analogue colour video signals and employing a Mach-Zehnder electro-optic waveguide device as a double sideband suppressed carrier frequency modulator is reported. It is shown that the receiver sensitivity of such a system may be as much as 21 dB greater than that for an equivalent direct detection system. The use of electro-optic frequency translators in coherent optical networks to assemble a frequency multiplex of wideband signals is described. Particular attention is given to the linearity of devices, in systems employing up to four channels, and it is shown that unwanted products can be suppressed to 30 dB below the signal level. The use of this type of device as a frequency control element in optical multichannel networks is also considered.

A traveling-wave Ti-indiffused LiNb03 guided-wave Mach-Zehnder interferometric modulator has been fabricated and characterized at λ= 1.3 μm. With a ±4.25-V drive signal an extinction ratio of 23 dB is achieved. The measured small-signal 3-dB bandwidth of 8.6 GHz is limited by attenuation and dispersion of the coplanar stripline. The fiber-waveguide-fiber insertion loss is 5.3 dB (Fresnel losses excluded).

Theoretical calculations of the modulation depth of the modes in integrated optic devices are reported and are applied to the design of a polarisation-insensitive modulator with a novel electrode arrangement. This achieves a high degree of polarisation insensitivity without requiring large modulation voltages or unrealistic alignment tolerances.

Research and fabrication of integrated optical (I0) multimode components in LiNbO3 is a subject of increasing interest. However, their operational possibilities and parameters are rather limited due to the multimode nature of the guided light. We are concentrating on some key elements that use stripe waveguides in LiNbO3 with one mode in depth and several lateral modes. Basic configurations, operational principles and recent results are presented, as well as some potential applications.

Surface acoustic wave (SAW) Bragg-modulators as frequency shifters are attractive for applications in sensors, since they yield high optical and electrical bandwidth. The Bragg-modulator consists of tapered monomode waveguides and the SAW field in between. A Gaussian beam yields a suppression of unwanted frequencies greater than 60 dB below shifted frequency, however, more realistic field distributions yield suppressions of about 20...30 dB.

Materials and growth processes for magneto-optic garnet film wavequides are described. The realization and characterization of single-mode waveguide structures is explained, and experimental methods for the investigation of the non-reciprocal mode conversion are discussed. Applications for waveguide isolators are briefly mentioned.

Integrated Optic Parametric oscillators in TIPE resonating structures are analyzed as regards the pump threshold power minimization. The amount of proton exchange has been chosen to satisfy phase-matching condition and the Ti:LiNbO3 waveguide parameters used for optimization. A comparison between TIPE and Ti structures will be discussed.

Use of periodic modulation of lithium niobate waveguide properties to achieve phase-matching for second harmonic generation has been investigated both theoretically and experimentally. The mathematical description has been reduced to the same form of differential equations as for the unperturbed case, but with a modified coupling coefficient. A compact expression for the conversion efficiency has been derived for the case when simultaneous modulation of both the linear and nonlinear properties are taken into account. For the case of modulation of only the linear properties, second harmonic light has been obtained experimentally.

The optical parametric fluorescence was observed for the first time in a guided wave structure. In contrast to bulk optics three processes occur: signal and idler photons belong both to guided modes or both to radia-ting substrate modes or one to a guided mode and the other to substrate modes. These processes were investigated experimentally in Ti:LiNb03-channel waveguides. Using a cw-argon laser (λ = 514 nm) or a pulsed dye laser (580 nm < λ < 615 nm) as pump source, the fluorescence was studied as function of the pump wavelength, the pump power, the waveguide temperature and of spatial filtering.

There is an increasing interest in the fabrication of optical parametric devices, pumped by semiconductor laser diodes, for both generation and amplification of tunable coherent radiation. This can be achieved by using waveguiding structures as they permit high optical intensities with modest powers, long interaction lengths and phase-matching using modal dispersion. There have been reports on efficient three wave mixing processes in LiNbO3 waveguides but these require rather high power (>1W). The pump power required can be reduced by either increasing the interaction length or using materials with larger non-linearities. However, to date the maximum phase-matched interaction length has been limited to about 2cm4 in LiNbO3 waveguides due to non-uniformity of the waveguide.

Computer aided measurement systems for the determination of nearfield intensity profiles, insertion loss, waveguide attenuation by Fabry-Perot resonance and refractive index profiles by effective indices have been developed. The repeatability and accuracy of the measurements have been analyzed.

An image processing system using a TV camera with an infrared sensitive (0.35 < λ < 2.0 μm) vidicon was de-veloped to measure two-dimensional intensity distributions of optical modes in dielectric waveguides. Ti:LiNb03 channel guides were studied as an example. Their modes were investigated as function of fabrication parameters, channel width, polarization and wavelength. The measured intensity distributions were numerically compared with calculated results using the finite element method.

Details of index profile measurement of slab waveguides by transverse interferometry using video image processing of the interference fringe pattern are discussed. Resolution limits, data processing and sample preparation are described. Some examples of ion exchanged glass waveguides are given.

An experimental investigation is presented on the conditions affecting the measurement of waveguide loss by detection of scattered radiation. Several factors have been taken into account, including: numerical aperture, magnification, defocusing and spatial resolution of the optical collection system; presence of spurious background; direction of collection and shape of the scattering lobe; mode-selective measurements. Measurements have been made at visible and near-IR wavelengths on planar and stripe waveguides, single- and multi-moded, and results on the best measurement conditions are reported.

We have proposed a novel technique to measure loss and facet reflectivity of semiconductor waveguides using Fabry-Perot resonance characterization. In order to obtain stable visibility of the optical transmittance, this technique has for the first time adopted a unique electro-optic effect instead of temperature-dependent Fabry-Perot resonance method. As a result, very accurate measurement has been realized as compared with those of currently available other measurement technique. Also we discussed the relation between spectral characteristics of incident light sources and waveguide parameters, and verified the conditions of this measurement to meet tight requirements of the waveguides.

Single tap ring resonators fabricated by silver ion-exchange in glass yielded finesse of 55 with an efficiency of 33%. Ring structures generated by ruby-lith show a decrease in propogation loss of 2.5 dB/cm compared to e-beam generated masks.

This paper proposes and demonstrates a new type of pressure sensor, using a metal-clad ion-exchanged glass waveguide with a liquid buffer layer. The thickness of the buffer layer is variable with pressure, which results in light intensity modulation of guided modes. In the tested waveguide pressure sensor in which water is used as the buffer layer, 80-% decrease of the output light intensity has been obtained with respect to an applied pressure of approximately 300 torr.

In recent years Hg1-xCdxTe with high concentrations of mercury has commonly been used in infrared detectors. In this paper it is shown that the same type of material, but with low concentration of mercury, can be used to form low-loss waveguides at 10.6 μm. After discussing what properties semiconductors in general must exhibit to yield infrared waveguides at 10.6 μm, we describe the use of high band gap HgCdTe structures manufactured by isothermal evaporation diffusion process (E.D.R.I.). These waveguides are formed on cadmium telluride substrates and characterized by classical guided optics methods. They exhibit very low attenuation (< 0.5 dB/cm) and they can carry high power densities.

In this paper we describe a low drive voltage phase modulator for the 10,6 microns wavelength. We present also the experimental results that have been obtained with such a component and the related theoretical model. The wave-guiding basic structure is realized by the vapour phase epitaxy of a slightly N doped GaAs layer on a heavily N doped (100) substrate of the same material. An ohmic contact under the substrate and a planar Schottky electrode on the weakly doped medium permit the application of an electric field in the guiding region via a reverse polarization of the device. The experimental results we present show that the phase modulation we have mesured on the TE0 mode of the guide for different applied voltages proceeds from two effects. The first one is of course electrooptical and is due to the electric field which only exists in the depletion region lying under the Schottky electrode. The second one, which is not negligible because of the long working wavelength, comes from the refractive index increase due to the free electron density lowering in that depletion region. In the particular case of our experiments this last phenomenon leads to a drive voltage decrease : 80 volts for a phase-shift of π on the TE0 mode for a 16 mm long interaction instead of 100 volts without this depletion effect. The proposed theoretical model which takes into account these two contributions is in a good agreement with the experimental results and give the real possibility to predict the performances of such a device. In addition to these results related to the active aspect, we present a low loss wave-guiding planar configuration using a strongly N doped InP substrate where losses below 1 dB/cm on the TEO mode have been measured at the 10,6 microns wavelength.