In the recent years a large research effort is being carried out to develop new or advanced glasses and the corresponding processes with the goal of implementing optoelectronic devices. Here we try to provide a brief review of the major improvements and of the recent trends in this area. Special attention is paid to the perspectives of sol-gel glasses, which can be doped in a relatively easy way with a large variety of active materials and are thus able to exhibit different functions, including light amplification and lasing.

We have characterized proton-exchanged z-cut LiTaO₃ planar waveguides fabricated with pyrophosphoric acid. A step index profile was assumed. Following proton-exchange the waveguides were annealed at temperatures from 300 degree(s)C to 500 degree(s)C. Interestingly, the surface index n, increased instead of decreasing. The waveguide depth d, (Delta) n_s, and shape of the index profile were closely monitored throughout annealing, and the results are presented. The mechanism of the surface index increase with annealing is explained and the results support this theory.

Composite rare-earth-doped glass waveguides are studied. Their modal behavior is examined theoretically using a finite-difference method. Measured fluorescence spectrum is presented and a glass waveguide amplifier with more than 6 dB amplification at 1.557 micrometers wavelength is demonstrated.

A novel integrated optic filtering element exhibiting a comb filter response has been achieved based on the coupling between an ion exchange waveguide to individual higher order modes of a multimoded overlay film. A K⁺/Na⁺ exchanged guide is fabricated in BK7 optical quality glass and designed to be singled moded over the 1 micrometers to 1.6 micrometers operating range, a calcium fluoride buffer region is then deposited before a high index film of zinc sulphide is evaporated onto the structure. Several devices have been fabricated to investigate the effects of varying the thickness of the overlay and that of the buffer layer. The notch widths observed to date range from 8 nm to 50 nm with channel spacings ranging between 150 nm and 220 nm; these coupled wavelengths agree well with the theoretical predictions.

Nonsymmetrical integrated optical Mach-Zehnder interferometers are produced in glass by potassium ion exchange and by silver ion exchange with ionic masking. Two- and three-port nonsymmetrical Mach-Zehnder interferometer structures with path length difference ranging from 10.75 micrometers to 259.7 micrometers are studied.

A brief analysis of recent experimental data reported for radiation-induced responses in directional coupler waveguides is presented. The data are compared with the coupled mode theory for the case of non-synchronous coupling. This analysis is important in understanding undesirable radiation-induced responses in guided wave devices such as cross talk and optical signal attenuation. The radiation-induced responses are examined and shown to be attributal to the alteration of the waveguide propagation and coupling constants. The magnitude of the refractive index change experienced by a directional coupler, which is exposed to a transient electron exposure, is determined from electro-optic theory and found to be consistent with theoretical predictions.

We have measured the effects of electrons on LiNbO₃ proton exchange waveguides. We have measured the attenuation and polarization component cross talk out of situ. These measurements were made using the 3 MeV Lehigh University Van de Graaff Facility.

We have measured optical attenuation in LiNbO₃ and LiTaO₃ waveguides due to exposure to an approximately 3 ns pulse of approximately 400 KeV electrons. The LiNbO₃ operated at 810 nm and the LiTaO₃ at 1309 nm. Both waveguides were formed using the annealed proton exchange method. Transient attenuation and recovery was observed for a series of pulse doses. To the accuracy of the measurements, total recovery was observed within 1 sec after exposure for both waveguides. Results from these waveguides were compared to earlier measurements of a titanium-indiffused LiNbO₃ waveguide.

The radiation sensitivity of different integrated optic (IO) devices was compared under standardized test conditions. We investigated four relatively simple device types made by four different manufacturers. The waveguide materials were proton exchanged LiTaO₃, LiNbO₃:Ti, Tl-diffused glass, and Ag-diffused glass, respectively. In order to standardize the irradiation parameters we followed the 'Procedure for Measuring Radiation-Induced Attenuation in Optical Fibers and Optical Cables' proposed by the NATO NETG as close as possible. In detail we made pulsed irradiations with dose values of about 500 rad*, 10⁴ rad, and 10⁵ rad, as well as continuous irradiations at a ⁶⁰Co source with a dose rate of 1300 rad*/min up to a total dose of 10⁴ rad. Device temperatures were about 22 degree(s)C, -50 degree(s)C, and +80 degree(s)C.

In this paper, we review LiNbO₃-based devices and technologies from both materials and device processing techniques. However, all the relevant areas cannot possibly be covered; we limit the scope of the paper to electrooptic devices. Also, we mostly focus on our own activities at Sumitomo Metal Mining. First, materials-related issues such as the uniformity and consistency of the substrate crystal as assessed by the variability of directional coupler coupling length are summarized. The photorefractive damage resistance is also reviewed; the dependence on the substrate quality and input laser wavelength. Second, taking the case of the multi-function gyro chip, we review and discuss the use of both Ti-indiffused and proton- exchanged waveguides on a single chip.

We report on optically-activated phase modulator (OAM) and modulator array on GaAs- GaAlAs compound semiconductor channel waveguides. A channel waveguide device with an optical activation window of 5 micrometers in diameter was fabricated. Optical activation was produced by using a HeNe 632.8 nm wavelength as the free-carrier generator and a 1.3 micrometers laser as the signal carrier. Thirty-three percent modulation depth was observed and 10^-2 index modulation was experimentally confirmed on an OAM working in the phase modulation regime. OAMs working in both phase- and cutoff-modulation regimes were theoretically determined by considering the fluctuation of the waveguide confinement factor. 8.2 dB modulation depth was observed on an OAM working at the cutoff regime. Furthermore, the activation source is in the mW power region which significantly reduces the size and cost of all optical switching devices.

We propose a new type of planar optical circuits; the holographic circuit. The light is confined to its path by gratings along the path direction.

The power coupling expressions for any pair of end separated waveguides are derived in general form for TE modes. The expressions are shown to agree with the accepted mode coupling expressions when the separation approaches zero. Furthermore, the expressions are used to discuss a particular type of integrated-optic device which makes use of the electro- optic effect and end separated waveguides.

Optical interconnection networks for linking a large number of users require the use of particular switching elements. For the classical 2 X 2 switching elements, in order to maintain the control voltage as low as possible, the length of the element cannot be less than a few millimeters. For this reason, the total number of stages implementable on a single LiNbO₃ crystal must be contained and the number of users N cannot be above 8. In order to extend the network dimensions, a different network architecture must be chosen which requires a new type of (alpha) X (beta) switching element. Generally speaking, (alpha) equals 2ⁿ and (beta) equals 2^m with n does not equal m. In this paper we present a 4 X 4 switching element for which two different solutions are considered. The design criteria of these structures are presented and the insertion loss and crosstalk are evaluated.

An integrated optical waveguide isolator based on adiabatic polarization splitters in the silica- on-silicon technology and non-reciprocal elements are proposed and investigated with an accurate Finite Difference Beam Propagation Method. Improvements of noise figure of an erbium-doped fiber amplifier by using this type of isolator are calculated and discussed.

Silicon technology is a well known, controlled technology, which has the advantage that optical and electronic circuits as well as micromechanics can be integrated on the same substrate. This paper presents the design and the realization of an integrated optical pressure sensor. It includes a Mach-Zehnder interferometer, coupling structures of waveguide to fiber and optical detectors, which are integrated into the silicon substrate. As silicon is the detector material wavelengths below 1 micrometers are used. The fiber coupling structure is realized by means of plasma- or KOH-etching. Microoptical lenses with a focal length near 1.0 mm fabricated by Laser-CVD may reduce coupling losses. The interferometer consists of strip- loaded waveguides made of an SiO₂-SiON-SiO₂ sandwich deposited on the silicon substrate by an LPCVD- or PECVD-process. For pressure sensing a membrane beneath one of the interferometer paths is micromachined from the reverse side by a fast plasma etching process. The optical detection is accomplished by an endfire coupling structure consisting of an antireflectivity coated vertical silicon PIN-diode integrated in a 15 micrometers epilayer at a step in the substrate.

Some experimental aspects of the problem of efficient coupling between semiconductor waveguides and single-mode optical fibers are examined. Waveguides based on different InP/InGaAsP structures (single- and double-heterostructures, multi-quantum-well structures (MQW) with different degrees of dilution) have been fabricated, as well as modified single- mode fibers (i.e. with flat or lensed, straight or tapered ends). Coupling efficiency measurements between these structures have been performed, and the results are presented and discussed; the lowest coupling loss, about 0.5 dB, was obtained with a conveniently tapered fiber and a moderately diluted MQW structure (MD-MQW).

Various nonlinear optical phenomena can be observed in silica based glasses when subjected to short light pulses with high power densities. However silica based channel waveguides can easily suffer from optical damage at relatively low average powers, as it has already been observed in silica based optical fibers. In order to prevent catastrophic failure of these waveguides, it is important to correlate their glass composition and guiding properties to the optical power density at which such a failure occurs. We report experimental investigation on the optical damage threshold of P₂O₅-doped and GeO₂-P₂O₅-doped high- silica content channel waveguides, fabricated by flame hydrolysis deposition on Si substrate. Waveguides are subjected to high peak power pulses from a Q-switched Nd:YAG laser, operating at a wavelength of 1.064 micrometers . The influence of silica dopants on the damage threshold levels has been investigated by comparisons of experimental results on the two silica systems considered. The influence on the damage threshold level of other parameters, such as Q-switch frequency and exposure time, has also been investigated in order to assess the possibility of cumulative effects in the waveguides examined.

Sintering kinetics play an important role in determining the structural and optical properties of silica based planar waveguides fabricated by flame hydrolysis deposition. Despite the fabrication process being a modification of the vapor-phase axial deposition method for the fabrication of optical fiber preforms, the planar deposition suffers from critical restrictions in sintering temperature range and gradients imposed by the presence of the substrate. Moreover, the planar sintering process, evolving as it does on a substrate, behaves quite differently from the isotropic case of the fiber preform. This results in further problems such as the viscosity- slowed coalescence of the soot and the unreleased stress of the deposited layer after the consolidation process. These problems, which are absent in the fabrication of fiber preform, govern the reliability and repeatability of the planar fabrication process. Extensive literature exists dealing with the sintering of fiber preform fabricated by flame hydrolysis, but not with regard to the fabrication of planar waveguides. We report on the influence of the temperature range and gradient on the evolution of the sintering of P₂O₅-doped silica planar films and its consequences on the dopant incorporation. An optimum sintering process has been determined which guarantees bubble free, low loss waveguides, prevents the warping of the substrate and yields the desired refractive index by inhibiting the volatilization of the silica dopant.

A new reactor--namely Select from Watkins Johnson--which is capable to deposit thick films of doped and undoped silicon oxide by low temperature oxidation (T < 500 degree(s)C) from silane and oxygen, has been used to realize 6 micrometers thick silica waveguides which are three- modal at a wavelength of 1.15 micrometers with an attenuation loss better than 1.0 dB/cm on as deposited film.

Ionizing radiation total dose effects have been investigated for 199 MHz SAW resonators fabricated on air-swept and as grown (non-swept) 40 degree(s) Y-rotated quartz. Sensitivity to radiation is substrate material dependent, with pure substrates showing less radiation degradation in performance. An unexpected reduction in sensitivity was found for devices coated with a 400 angstroms layer of SiO_x.

A brief report on an ongoing study concerned with the responses of acousto-optic modulators (AOMs) and deflectors (AODs) exposed to linearly accelerated electrons, gamma rays, and X rays is presented. The diffracted spatial intensities of PbMoO₄, TeO₂, and InP devices were observed to undergo displacements and attenuation. Discussions of radiation- induced temperature gradients and color center formation believed to be responsible for these effects are included.

As spacecraft require lighter weight and higher speed communication systems, technologies such as fiber optics have come to the forefront. The space radiation environment, however, can be quite harsh in its effects on a fiber optic system. This paper presents the methodology behind testing integrated optoelectronic receivers and transmitters for single event upsets (SEUs). Two main causes of single event effects in the space environment are discussed, namely protons (trapped and solar flare) and galactic cosmic rays, as well as ground test facilities used to simulate the space environment. The prime emphasis presented herein is on the actual test requirements and system schemes needed for devices such as integrated optoelectronics. The definition of an SEU is unique to each fiber optic system application: a setup that is capable of detecting small signal 'glitches' may not be realistic when the interface circuitry utilizes an overlying system protocol or sampling scheme. Additionally, the expected system utilization rates may also affect the SEU rates. Actual test data and applications are discussed.

We report on the effects of electron irradiation at doses up to 44 MRad on planar waveguides fabricated from nonlinear optical polymers. The second-order optical nonlinearity was measured by second-harmonic generation before and after irradiation of two types of polymeric waveguides: one fabricated from a guest-host polymer and the other from a main- chain polymer. Mechanisms for observed effects are discussed.

We have developed a user friendly program to analyze the electromagnetic behavior of general integrated optics circuits with a two-dimensional Beam Propagation Method. As a graphical interface for the description of the circuit under analysis we used a file produced by the optical layout generator Sigraph-Optik (copyright by Siemens-Nixdorf), while we acquire all the parameters necessary for the simulation via pop-up menus or a command file. The electromagnetic analysis is at the moment performed with the Beam Propagation Method based on FFT but we are working to extend it to a Crank-Nicholson finite difference scheme with transparent boundary conditions to minimize the computational window. The program final output are color maps and data files containing the effective refractive index and the field amplitude and phase. It is then possible to carry out a post processing on such files to make three dimensional graphs that summarize the circuit performance, to extract two dimensional plots at particular circuit sections and to project the field on the local normal modes of the waveguides. Examples of the simulation capabilities are given.

Acousto-optic (AO) devices based on surface acoustic wave (SAW) propagation are widely studied for signal processing and optical computing systems. Among them, devices formed by a multilayer acoustic structure of III/V semiconductor materials are of particular interest because of the acoustic dispersion characteristics, which increase the number of design parameters to be used. In this paper, we present an accurate model of the acousto-optic interaction in III/V multilayer guiding structures having N layers of different materials, taking into account electro-mechanical and optical losses. By considering the full SAW field distribution, we calculate the overlapping integrals of diffracted modes in the grating region and compare the results in terms of diffraction efficiency with a well-known approximated design expression. A number of different cases have been analyzed, concerning proton exchanged and titanium indiffused lithium niobate waveguides and III/V semiconductor guiding structures, such as ZnO/AlGaAs/AlGaAs. The AO transducer behavior is defined in terms of diffraction efficiency as a function of the acoustic frequency and geometric parameters. The typical behavior of Bragg-regime diffraction in acoustooptic cells on LiNbO₃ and GaAs planar waveguides has been confirmed, when both +1 diffraction order and higher orders are produced by the acoustooptic grating as output guided modes. Interesting diffraction properties have been derived as a function of waveguide structure, transducer acoustic power, grating length and applied acoustic frequency.

Software tools for design of passive integrated optical components based on ion-exchanged glass waveguides have been developed. All design programs have been implemented on personal computers. A general simulation program for ion exchange processes is used for optimization of waveguide fabrication. The optical propagation in the calculated channel waveguide profiles is modelled with various methods. A user-friendly user's interface has been included in this modelling software. On the basis of the calculated propagation properties, performance of channel waveguide circuits can be modelled and thus devices for different applications may be designed. From the design parameters, the lithography mask pattern to be used is generated for a commercial CAD program for final mask design. Examples of designed and manufactured guided-wave devices are described. These include 1- to-n splitters and asymmetric Mach-Zehnder interferometers for wavelength division multiplexing.

The integrated optics waveguide devices should have low coupling losses with optical fibers. We present a procedure for determining the ion-exchange process parameters for fabrication of such low loss waveguides in glass and discuss the single mode waveguide fabrication by the inverse ion-exchange.

In this paper we study the quantum-theoretical description of second-harmonic generation (SHG) in optical waveguides. The interaction operator of three waveguide modes, by means of which the equations for spatially slowly varying annihilation and creation operators of the field strength amplitudes can be determined, is obtained by using the mode fields in the waveguides. The equations for spatially slowly varying annihilation and creation operators of the field are derived. We seek approximate solutions of the operator equations, and obtain the conversion efficiency of SHG.

Several results of investigations of leaky optical wave (LOW) excitation in LiNbO₃ planar waveguides at the nonaxial light propagation and of their acoustooptical interaction with surface acoustic waves (SAW) in such waveguides are presented. In experiments, leaky waves were excited by the total internal reflection of an ordinary polarized laser beam from the waveguide surface. The LOW excitation efficiency dependence and distortions of the reflected beam intensity distribution on the light propagation direction were investigated, the novel geometry of radiated ordinary mode conversion into the extraordinary one due to the diffraction of leaky waves on SAW was observed, and LiNbO₃ acoustooptical modulators using LOW were realized. Effects of holographic grating photorefractive recording in LiNbO₃ waveguides also were studied.

Recent progress in guided-wave lasers and quasi-phase-matched (QPM) second harmonic generation (SHG) devices fabricated in lithium niobate and lithium tantalate will be reviewed. Significant new results from research carried out by us will also be presented. Relevant aspects of the proton exchange waveguide formation process will be examined. Because of the major limitations encountered so far with lithium niobate and tantalate, alternative materials with potentially superior properties should be considered and these are touched on at the end of the paper.

Double-ion exchange technique in glass can produce partial buried optical waveguides. This paper proposes an analytical index profile by erfc-like function to model such waveguides according to the diffusion theory. By employing WKB technique, the characteristics of the waveguides are also investigated.

Fabrication of single-mode glass waveguide devices by ion exchange with ionic masking are studied. In channel waveguides, low losses (0.1 dB/cm) at 1.3 micrometers wavelength are measured. As a device example a nonsymmetric Mach-Zehnder interferometer at 1.55 micrometers wavelength region is demonstrated. A Y-branch wavelength multiplexer, in which 'tapered ionic masking' is utilized, is also described. Design of a 0.98 micrometers /1.55 micrometers wavelength multiplexer is presented.

A miniature integrated optical Michelson interferometer in glass based on a 3 X 3 directional coupler for high precision displacement measuring is presented. The planar waveguide structure can be used simultaneously for beam splitting and generation of phase shifted interference signals. The latter are necessary for decoding the direction of motion and for interpolation procedures to increase resolution and accuracy. The basic process for fabricating the waveguides in the integrated optical chip is a double thermal ion exchange of silver and sodium in special glass BGG31. It allows to produce buried waveguides with low loss and modefield dimensions adjusted to standard silica fibers.

An integrated optical ring resonator employing a novel four-port nonsymmetric Mach-Zehnder interferometer as an input/output coupler is proposed and demonstrated. The interferometer based on two hybrid optical couplers is essentially a 0.98 micrometers /1.55 micrometers wavelength multiplexer in connection with the ring resonator. The device is designed by using the effective indices of the guided modes in a silver ion-exchanged waveguide and is fabricated in glass substrate by double-ion-exchange process. The input/output coupler for the ring resonator is characterized using a continuous light source as well as lasers at (lambda) equals 1.06 micrometers , (lambda) equals 1.3 micrometers and (lambda) equals 1.523 micrometers . The finesses of 5 for the ring resonant is measured at (lambda) equals 1.523 micrometers . It is employed to estimate the propagation losses in the ring waveguide as 0.17 dB/cm. Potential applications of the device are discussed.

Features of integrated optical modulators that are important for their use in analog link applications are summarized. The Mach-Zehnder interferometric modulator fabricated on a lithium niobate substrate is treated in detail.

Silica-on-silicon waveguiding components are of great importance in the construction of an all optical signal processing network. By using arsenosilicate glass (ASG) waveguides a tight optical confinement can be achieved thus allowing a high device packing density. This paper examines differences in waveguide curvature and reflow conditions then illustrates how they affect the device loss.

Two polymer-glass-waveguide all-optical switches are proposed. One consists of an X-branch channel glass waveguide with a strip of nonlinear polymer on the center top of two-mode region (double width). It is based upon the power-dependent two-mode interference principle. Another is composed of an asymmetric Y-branch glass waveguide with a strip of nonlinear polymer on top of one branch. It is an adiabatic type all-optical switch. Theoretical analyses show that, by properly choosing device structure parameters, low crosstalk or even complete switchings are possible with low optical power.

We describe a laser-writing technique for fabricating polymeric optical waveguides by photo- crosslinking acrylate monomer materials. We report loss measurements as low as 0.01 dB/cm in straight laser-written photopolymer waveguides and describe changes in waveguide losses at temperatures up to 250 degree(s)C. Loss measurements are also summarized for 90 degree(s) bends and laser-written 8 X 8 star couplers.

A twelve-channel single-mode wavelength division demultiplexer operating at 830, 840, 850, 860, 870, 880, 890, 900, 910, 920, 930 and 940 nm with diffraction angle varying from 10 degree(s) to 65 degree(s) and using a graded index (GRIN) polymer waveguide is reported for the first time on a semi-insulating GaAs substrate. Diffraction efficiency up to 55% was measured. The wavelength spreading of the Ti:Al₂O₃ laser (approximately 4 nm, 3 dB bandwidth) causes an average crosstalk figure of -20.5 dB. The beam width of the diffracted signal as a function of the input beam width, the grating interaction length, and the diffraction angle are considered.

N X N Multistage Interconnection Networks are generally constituted by arrays of 2 X 2 switches linked together by some types of 'shuffle networks'. The number of stages necessary to obtain all the possible input-output links, is proportional to log₂N. This number limits the dimensions of optical networks implemented on LiNbO₃ crystals, because the length of the electrooptic switching elements cannot be reduced under a few millimeters. In order to link a number of users more than 8, a different architecture must be used. It is composed of (alpha) X (beta) switching elements with (alpha) equals 2^(nu ) and (beta) equals 2^(mu ) with (mu) does not equal (nu) . This reduces the overall network length by lowering the number of stages, even if the transversal dimension is slightly increased. In the paper the architecture of such a shuffle network is presented and its performance, in terms of networks power loss and crosstalk, is evaluated.

Single-mode stripe optical waveguides in poled organic thin films have been fabricated by excimer laser photoablation using wavelengths at 248 nm and 193 nm. The process uses a quartz proximity photomask as a stencil to the collimated laser light. The process also requires relatively low light densities (approximately 20 mJ/cm²) allowing large areas to be processed with currently available excimer lasers. This one-step process allows the definition of intricate structures without altering film alignment properties necessary to utilize the inherent electro-optic effect. Possible distortion of waveguide structures caused by diffraction elements (such as in waveguide Y-junctions) is examined. Active devices exhibit electro-optic coefficients similar to equivalent planar waveguide devices.

An elliptical-core (e-core), two-mode fiber optic micro-device for in-line modulating and switching has been studied. The polished surface is so close to the core of the fiber that the differential propagation constant between the LP₀₁ and LP₁₁ even modes is strongly dependent on the refractive index of the deposited oil. The power from a single lobe and the total power are separately received by two detectors. In experiments, the dependence of the differential phase shift between the two modes on the refractive index of the deposited material was observed. The switching characteristics of the structure so fabricated, switching between the two lobes were also demonstrated. Further, different coupling characteristics of the two modes propagating the fiber into the deposited layer, which functions as a planar waveguide, have been observed.

Optical attenuators for proton-exchanged and annealed waveguides in LiNbO₃ are modeled by the matrix effective refractive index (MERI) method. It is shown theoretically and experimentally that an attenuation of 1.6 dB/mm can be expected for a titanium-gold metallic overlay. The theory indicates that this attenuation can be increased to nearly 4.5 dB/mm by placing a titanium dioxide layer between the waveguide surface and the metallization.

We demonstrate active surface-emitting sum-frequency generators based on monolithic integration of InGaAs/GaAs single quantum well lasers and multilayer Al_xGa_1-xAs nonlinear waveguides. As broad area lasers with uncoated facets, threshold current densities as low as 87.5 A/cm² have been obtained for a cavity length of 3.3 mm at 300 K. A differential internal quantum efficiency of 71% and a waveguide loss of 3.2 cm^-1 have been measured from the room temperature light-current (L-I) characteristics. With an active/passive segmented cavity operating at 0.984 micrometers , coherent sum-frequency light at 0.51 micrometers was radiated from the etched-off passive segment surface when coupling 1.06 micrometers light into the cavity as the TM guided wave to interact with the TE SQW laser mode. The measured conversion efficiency in terms of the nonlinear cross section A^nl is about 2 X 10^-7 W^-1 which agrees well with the calculated value. Potential applications of the integrated devices are briefly addressed.

In this report we propose single beam holographic scheme for formation of focusing grating, designed for different purposes, on the waveguide surface. The main idea is to substitute the traditional flat mirror with one of nonplane surface. Different surfaces correspond to two cases involved. (1) Plane wave propagating in the waveguide is coupled out into the air and focused into a spot. Appropriate relations for geometric parameters of the sphere have been developed. Experimental verification has shown that diffraction-limited focusing spot can be achieved for grating length to focal length ratio l/f < 0.1. (2) External incident plane wave is coupled in and focused by the grating inside the waveguide. It is shown that aberration-free grating can be formed using a conical surface as the mirror. Simple formulas for geometric parameters are also presented. Focusing of an He-Ne laser beam ((lambda) equals 1.15 micrometers ) in a waveguide plane is demonstrated.

An effective method of coupling optical signal from single mode fiber to thin film waveguide applicable to integrated optical (IO) devices is shown. The technique uses a coupling waveguide of garnet material. The matching of propagation constants between thin film and garnet material is achieved by controlling the thickness of the thin film waveguide. Mismatching of propagation constants due to variation of film thickness along the propagation length and its refractive index variation are considered in the analysis of coupled power. Polymer, co-polymer and polymerized solgel solution are used for the IO waveguide devices. Different structures of thin films are shown. Conditions for improving the optical power coupling efficiency will also be discussed.

A novel microstrip resonator structure for use with integrated Y-branch optical modulators fabricated in Ti:LiNbO₃ is proposed. The legs of the structure are intended to act as the electrodes of the modulator, with light being directed into each of the output waveguides of the Y-branch on alternate half-cycles of the standing wave excited in the resonator; forming an optical commutator switch. Such resonators having Al₂O₃ substrates were designed, fabricated, and tested. Measurements on one such resonator, operating at 7.12 GHz and having an unloaded quality factor of 123, indicating that 50 V should develop across the ends of its legs for 35 mW dissipated power; the corresponding values, from the model used to design the resonator, were 179, 50 V,and 24 mW, respectively. Using the model it is shown that a similar resonator fabricated on LiNbO₃ should be able to develop about 50 V for 100 mW dissipated power at 15 GHz.

In this paper we present the theoretical investigation and design of a guided-wave optical processor suitable for beam forming of a linear phased array antenna and based on a planar structure involving two acousto-optic transducers (AOT) having contra-directional surface acoustic wave (SAW) propagation. By applying two different periodic microwave signals to the transducers, the phase content of the output field distribution in the transverse direction with respect to the propagation one is a linear function of the applied frequency difference and can be used to drive a photodiode array connected to the phased array antenna by a RF circuit. The performance of the circuit has been also defined with respect to the resulting beam forming and to the radiation pattern characteristics of the driven microwave array. In this study, acousto-optic interaction on a lithium niobate planar-waveguide has been considered.

Artificial dielectric materials are dielectrics in which other dielectrics or conductors are embedded to achieve different, effective dielectric properties. In the experiment, transmission lines embedded with suspended GaAs crystallites were used. The effective dielectric constant was changing upon illuminating the strip-line with light.

High-frequency modulators have been used to record very fast analog voltage pulses in the Nuclear Test Program at LLNL. A system consisting of 810 nm laser diode carrier sources, 7 GHz H-branched, balanced bridge modulators (YBBM), a kilometer of single-mode optical fiber and a streak camera recorder has been successfully fielded. The total system -3 db bandwidth is 4 GHz with a slow roll-off allowing the recoverable data capabilities of the system to approach 10 GHz. This system has provided us with a diagnostic tool that allows us to resolve high-frequency structure in our signals which has been calculated but never measured because of limitations in the resolution of previous measuring systems. A description of the system will be given with particular emphasis given to the YBBM modulator characteristics and performance. Fast pulse data recorded by the system will be shown and an indication of the accuracy with which the pulse can be reproduced will be provided. We expect this system to be a valuable tool that will be used regularly to study the physics of materials at extremely high temperatures and densities. Plans for upgrading the system to have a -3 db bandwidth of 7 - 8 GHz will also be discussed.

A characterization of diluted silver ion-exchanged waveguides in glass substrates was carried out for three different wavelengths, (lambda) equals 0.6328 micrometers , 1.152 micrometers , and 1.523 (mu) , by using an improved WKB method which correctly calculates the phase shift at the diffused boundary, hence eliminating calculation errors in the theoretical dispersion curves mostly in single mode regions and near other mode cutoffs. The results show a significant improvement in the agreement between the theoretical WKB dispersion curves and the measured mode indices.

Optical phase drifts of guided waves in LiNbO₃ waveguides can be caused by two different physical effects: light-induced refractive index changes (photorefractive effect) and so-called DC drift effects. Both phenomena have been investigated experimentally by a special interferometric technique on simple channel waveguides with very high accuracy. Light- induced refractive index changes were measured at 633 nm wavelength and in the 800 nm region. These index changes in annealed proton exchanged (APE) waveguides are about one order of magnitude smaller compared to titanium indiffused (TI). This can be explained by an increased photoconductivity of the APE material. DC drift effects in APE waveguides, however, are quite large and cannot be reduced in the same way as for TI waveguides. This is due to an ionic charge transport process. MgO doping of the waveguide substrates leads to a considerable reduction of both the photorefractive effect and the DC drifts of APE waveguides. The influence of both drift effects on the stability of a three-beam interferometric displacement sensor was demonstrated.

We describe the design, fabrication, and testing of a silicon waferboard dual-detector module used in an integrated optical heterodyne balanced receiver. This 'Silicon Waferboard' approach, as its name implies, substitutes a silicon substrate incorporating precision micromachined structures in lieu of conventional printed circuit boards and has been used for both optical transmitter and receiver fabrication. Our dual-detector receiver substrate incorporates orientation-dependent etched v-grooves for fiber placement in addition to metal/insulator/metal (MIM) bypass capacitors and high-speed photodetectors. Preliminary measurements indicated a receiver bandwidth potential of 14 GHz. The performance of the dual-detector receiver module as well as its individual components will be described.

The performance of high-speed lithium niobate modulators and switches make them attractive for high bit-rate communication systems. Significant process has been made to improve the speed and lower the drive voltage of these devices using both broad-band and narrow-band velocity matching techniques. Here I describe our results toward realizing broad-band, low- voltage, adjustable chirp modulators. These modulators are intended to replace directly modulated laser diodes in the transmitters of dispersion limited optically amplified systems. Also, presented is our work on high-speed switches for use as multiplexers and demultiplexers in optical-time-division multiplexed systems. These techniques are important because they offer the potential of very high bit-rate (> 10 Giga-bit-per-second) transmission systems utilizing relatively low bandwidth electronic components.

A new process is proposed to attach optical fibers to channel waveguides. Fibers are self aligned with the waveguides. The process results in permanent and rugged fiber pigtailed integrated optical components and facilitates their low-cost production.

In this paper, we report on fabrication process of ordinary and rare-earth-doped aluminum phosphate sol-gel films and their physical and optical properties. The gel films are transparent, hard and of good optical quality as glass. High doping of rare-earths (Nd³⁺, Er³⁺ and Yb³⁺) are realized in films with this technique. This type of doped films offer potential benefits for applications in the field of active integrated optics devices for optical telecommunication systems.

A new structure for integrated optics lasers and amplifiers in glass by sol-gel and ion exchange techniques is proposed. Due to unavailability of commercial rare-earth-doped glasses optimized for both lasing and ion exchange, we cover ion-exchanged glass waveguides by a rare-earth-doped aluminum phosphate layer, made by sol-gel method. As an example, an Er- doped waveguide amplifier is optimized theoretically.

We optimize experimentally the double ion-exchange process parameters to achieve a designed phase modulation for a wavefront passing through a computer-generated waveguide hologram. We also demonstrate a gradient-thickness waveguide hologram (kinoform) for 1/8 beam splitting.