The implantation of He+ into LiNb03 for the modification of the refractive index and the use of this technique for the fabrication of optical waveguides are reviewed in this paper. The effects of the various fabrication process parameters on the properties of the optical waveguides are also discussed.

This paper presents an experimental investigation on the characteristics and the capabilities of optical densitometry as a low cost, easy and non destructive technique to measure Ti film thickness. Optical density yields a sensitivity and a resolution equal or better than 3 Å and can be absolutely calibrated for the total metal content at given deposition conditions.

An integrated optic device is described which acts as the optical analog of a voltage regulator or, more precisely, a tunable voltage source. This device is suitable for stabilizing a fluctuating optical intensity or for providing a tunable power source with immunity to input power variations. An incoming optical signal is beamsplit by a tunable directional coupler (the control element), the output channel of which is further sampled by an additional coupler (the monitor element) and the intensity is compared to a reference level. The resulting error signal, suitably amplified, serves to adjust the first coupler, driving the output intensity to the reference level in a negative feedback loop. The design and performance of a device fabricated in Ti-indiffused lithium niobate is discussed.

We have established the polarization dependence of the power penalty in a direct detection optical fiber communications system using an integrated lithium niobate traveling-wave intensity modulator at 1.3 microns.

The first silicon-on-sapphire optical waveguides have been demonstrated. Waveguiding at λ=1.3 microns has been observed in silicon films 0.95 and 1.5 microns thick and in raised strip structures 1.5 microns thick.

Mode properties of four-layer planar optical waveguides consisting of a waveguiding layer bounded above by free space and formed on a silicon dioxide isolation cladding layer which in turn is formed on a thick silicon substrate are considered. Perturbation approaches are shown to be accurate except near mode cutoff where a numerical solution of the four-layer equations is required. Numerical calculations of waveguide attenuation due to substrate coupling for thermally-nitrided silicon dioxide waveguides are presented for a variety of layer thicknesses, layer material compositions, and wavelengths. Comparison with experimental data is included.

Crystalline silicon (c-Si) exhibits two electro-optical effects that are suitable for device-application in guided-wave modulators and switches. The effects are electrorefraction and free-carrier dispersion. The dispersion is controlled by electrical injection or electrical depletion of charge carriers. The magnitude of these effects has been calculated in this paper. The results for c-Si are compared to those for GaAs and InP. Low-loss guided-wave electro-optical phase modulation structures in c-Si are proposed here.

This paper reviews the results of recent experiments that examine sub-bandgap optical emission from impurity-doped crystalline silicon.

The paper presents a solution for the design problem of planar optical waveguides with refractive-index profiles that support N TE modes with prescribed propagation constants. The N-soliton solution of the Korteweg de Vries equation is used to obtain a formula which determines an N-parameter family of functions describing the refractive-index profiles each of which has the desired property. An analytical form of the solution of the problem is ob-tained in terms of hyperbolic functions. Formulae for the choice of N arbitrary constants which produces the symmetric refractive-index profile are given. The exact modal solutions for derived refractive-index distributions are given in terms of hyperbolic functions. The cases of N=1,2,3 and the hyperbolic-secant profile are discussed in detail.

The experimentally determined bandwidth of the interaction of laser light with magnetostatic waves (MSWs) has been limited, until recently, to about 30 MHz. This limitation is caused by the pronounced dispersiveness of the MSW. We report an approach employing an inhomogeneous bias magnetic field which has yielded a significant improvement in the bandwidth of Bragg diffraction of an optical guided wave from magneto-static forward volume waves (MSFVWs). In the experiment, a bandwidth of about 350 MHz was observed.

Channel waveguides produced parallel to the z-axis in x as well as y-cut LiNbO₃ by Ti indiffusion are found to display severe optical damage in the form of coupling between TE and TM modes for power levels in the range of 1-100 microwatts at wavelengths of .633 and .488 microns. Previously, this orientation was thought to display little or no damage. The effect is manifest by both a steady state power dependent transfer of as much as 30% optical energy between orthogonally polarized modes as well as a transient regenerative switching between these modes seen only in x-cut samples subjected to continuous optical throughput at the above power levels for a period of 8-24 hours. A model of the observations is proposed based on photorefractive perturbations

Focusing and deflection of light propagating in planar optical waveguides are caused by the suitable change of the effective refractive /modal/ index of the light - guiding film. The usual technique for obtaining the modal index variation in thin dielectric guides con-sists in change of thickness of the film /overlayer deposition/ or of its bulk refractive index. Referring to the latter method - the ion exchange is commonly applied. In this paper we show that the thermally induced change of the bulk refractive index in glass can be utilized for constructing the light focusing elements of planar optics. We report some preliminary theoretical and experimental results in obtaining the thermally induced planar SELFOC and Luneburg type lenses for light propagating in planar glass waveguide.

Coupled mode theory for power orthogonal modes is briefly reviewed. When the modes are not power orthogonal, modifications are necessary in the evaluation of the coupling coeffi cients and in the interpretation of power delivered to the output of a coupler, as pointed out by Hardy and Streiferl. In practical terms, these modifications lead to the presence of crosstalk in optical switches that may impair their operation. Two realizations of an optical switch are investigated and the amount of crosstalk as predicted by the "refined" coupled-mode theory is determined.

Computer simulations indicate that polarization independent coupling can be achieved in both prism-and grating-loaded optical waveguide consisting of dielectric multilayers supported by a metal plate. It is shown that a double-layer dielectric structure supported by a metal plate can be designed to achieve the phase matching between TE and TM guided waves. At optical frequencies, a metal, such as silver, behaves like a plasma medium with a negative dielectric constant, and a simple metal-dielectric interface can support a surface plasmon mode. The mutual effects of the guided modes and the plasmon mode are examined in detail. Furthermore, both prism and grating are considered for use in conjunction with the waveguide structure to provide the coupling mechanism, which is explained on the basis of leaky-wave phenomenon. The composite waveguide structure, including either a prism or a grating, is analyzed as a rigorous boundary-value problem. The propagation constant, including both phase and attenuation constants, is obtained as the real and imaginary parts of a complex eigenvalue of the waveguide. It is shown that the phase and attenuation constants of TE and TM modes can both be matched. Thus, high-efficiency polarization-independent couplers can indeed be designed.

The throughput of data and signal processors is being pushed to ever increasing limits. One of the problems which must be addressed when designing processors to operate at high speeds is the extreme difficulty of transmitting data at gigabit/sec rates. Conventional electrical interconnect and switching technology is rapidly becoming a critical issue in the realization of systems using high-speed silicon and GaAs-based technologies. The performance of electrical interconnects is adversely affected by increases in capacitance and reflections due to impedance mismatches. One solution may be the use of optical inter-connects to transmit the data. In an attempt to develop high-speed optical interconnect systems, research programs have been started to integrate optoelectronic devices on a common substrate with high-speed GaAs electronics. A few MSI-level GaAs circuits have been demonstrated with clock rates above 1 GHz. It is possible to integrate optical emitters and optical receivers on the IC to perform the input/output functions required to interface the optics with high-speed processors. In this paper, AlGaAs/GaAs integrated optoelectronic devices are examined from the standpoint of what is needed to fabricate the devices and what performance can be expected for optical interconnects.

An inexpensive IBM based laser writing system for making masks suitable for integrated optic applications is presented. The high degree of computer control makes this technique easy to use and relatively fast. The system can write lines, circles, arcs and shaded areas generating non-conventional designs and can be interfaced with various C A D programs.

Ti in-diffused LiNb0₃ crystals were examined using EMPA and SIMS with a liquid metal ion probe. The switching region of the waveguide consisted of two 5 pm channels of sputter deposited Ti with a 5 pm gap. We found that after in-diffusing the Ti at -1050°C, the Z-cut crystal had a sharper Ti distribution profile when compared to a Y-cut crystal. This is consistent with previous studies showing that the bulk diffusion coefficient for Z-cut crystals is greater than that for Y-cut crystals. However, the maximum lateral extent of the Ti was similar in both cases. It was shown that under optimum conditions, the electron microprobe analysis volume was approximately 3 pm. This is much less than the measured values for the Ti FWHM and maximum lateral extents, which were on the order of 20 and 60 pm, respectively. Using a relatively new SIMS technique employing a Ga liquid metal ion gun (LMIG-SIMS), it was possible to image the surface Ti distribution and obtain SIMS line scans of the individual channels. There was excellent agreement in the shapes of the Ti distributions observed between the two techniques. Considerable overlap of the two Ti channels was evident in the switching region. The Y-cut crystal had essen-tially a single Ti profile, while two partially resolved peaks were observed for the Z-cut crystal.

The basic principles of Transmission Electron Microscopy are outlined and examples of microstructures observed in LiNbO₃, waveguides reported. Defects present in the waveguides may have significant effects on their waveguiding ability. Various speculative arguments are suggested for the influence of these defects on the waveguide.

The optical crosstalk observed in Ti:LiNb0₃ directional coupler switches can be accounted for by non-uniformities in the concentration profile of the Ti-diffused waveguides. I report on the results of recent measurements and calculations to identify the source of these Ti concentration fluctuations.

Bistable optical devices have been suggested for a number of applications (switching, optical memory, binary logic, discrimination, amplifications, clipping, limiting and pulse shaping) in optical signal processing and communication system. Recently, several integrated optical bistable devices have been made available. Most of them have performed by using LiNb0₃ as electrooptical waveguide modulator. A review of integrated bistable devices based on waveguide optical modulators is presented under this paper.

A nonlinear directional coupler, consisting of a GaAs-based Multiple Quantum Well structure sandwiched between two slab waveguides, is analysed.

An optical oscillator has been designed, constructed, and operated by using a HeNe laser and acousto-optic modulator in conjunction with two opposed fiber optic feedback circuits. Depending on round-trip feedback time, a low frequency ( 1Hz) sinusoidal oscillator or a high frequency (100KHz) square wave (,..%,1 us rise time) is obtained.

The main aim of this digest is to present the problem of TO-OF interfacing and vice-versa, from a few parti-cularly chosen sides. These are: materials and technologies met in both fields, functional components and devices, and full operative systems. We present here a variety of solutions for TO-OF interfaces and draw some gene-ral conclusions connected to their future development. The digest contains also a report on our own contributions in this field.

An optical fiber communication system can be used much more efficiently with the addition of wavelength-division multiplexing (WDM). which effectively provides multiple transmission lines over a single fiber using different wavelengths of optical energy. An integrated optic WDM system which utilizes a wavelength-dependent angularly dispersive diffraction grating is designed from fundamental equations. Such a device has many advantages over competing WDM systems.

Fiber devices using polarization-maintaining fibers called PANDA fibers are presented. They are polarization-maintaining couplers and polarization-splitting couplers, optical isolators and optical circulators, and multi/demultiplexers designed for 1.3 μm wavelength. Crosstalk of -32 dB and excess loss of 0.03 dB for the polarization-maintaining coupler, and polarization-splitting ratio of 17 dB and excess loss of 0.5 dB for the polarization-splitting coupler have been fabricated by a fusion-elongation method. A fiber polarizer with the extinction ratio of more than 40 dB has been presented by using the difference of bending loss between the orthogonal modes in the PANDA fibers. Multi/demultiplexer with narrow band-pass of 1.4 nm utilizing combination of PANDA fiber polarization dispersion and the polarization-splitting coupler has been realized. An optical isolator consisting of fiber polarizers and a spherical YIG with a lens function and an optical circulator consisting of polarizing-splitting couplers and spherical YIGs have been achieved.

Double tap ring resonators fabricated by silver ion-exchange in glass yielded a finesse of 55 and an extraction efficiency of 55%. These numbers imply a propogation loss of 0.86 dB/cm and that as much as 10% of the energy in the input tap appears at the output tap after filtering through the ring resonator. We also measured the back scatter in the ring resonators and found it to be only 1% of the forward propogating intensity. This back scattered light can result in destabilization of the laser diode.

The employment of high speed fiber-optic distribution networks for large, complex millimeter wave systems, such as large aperture phased array antennas with active transmit/receive (T/R) modules, presents a formidable challenge. Experimental results of a fiber-optic link synchronizing a millimeter wave IMPATT oscillator of an active T/R module is discussed. In addition, a novel fiber-optic time delay element suitable for beam control and signal processing is introduced. The experimental results are incorporated into a system model and examined in terms of phased array applications. Further research directions in integrated and fiber optics, leading to the ultimate realization of an optically controlled phased array antenna, are discussed.

The extinction ratio of integrated optical stripe waveguide polarizers fabricated with silicon monoxide/aluminum overlays has been measured. Values in excess of 50 dB were recorded. The effect on fiber waveguide misalignment has been determined for a range of waveguide polarizer widths and the effect of waveguide width on extinction ratio investigated. For a given polarizer system, an optimum waveguide width is found to exist.

An illustrative, device systems level desirability optimization analysis has been performed for a number of important electrooptic materials that are candidate for use in high-speed guided-wave optical devices. Ferroelectric materials with high and low transition temperatures, cubic crystals, organic crystals, and alloy semiconductors have been considered. The bulk guided-wave phase modulator has been taken as the initial screening device. Performance measures such as electrical power supply constraints and the device's maximum operating speed have been analyzed as a function of system variables that include material properties and electrode architectures. Desirability analysis has been presented as a composite mathematical function that describes two or more independent performance measures in terms of all relevant system variables. This function has been displayed graphically to identify those sets of system variables that jointly optimize the performance measures of greatest interest. The initial screening analysis has ignored propagation loss and less-than-ideal overlap between electrical and optical fields. Potassium niobate, barium titanate, and lithium niobate have been found to be among the more desirable electrooptic materials. The use of dielectric buffer layers, several thousand Angstroms in thickness, has been found necessary to isolate the modulator electrodes from high dielectric constant, high electrooptic strength materials such as potassium niobate. Buffer layers, however, have been found to be generally unnecessary when using the lower permitivity and lower electrooptic strength materials such as lithium niobate.

We describe a number of promising applications which make use of the favorable electro-optic properties of BaTiO₃.

Single mode channel and planar waveguides have been formed in strontium barium niobate Sr_0.6 Ba_0.4Nb₂0₆ (SBN:60) by sulfur indiffusion.1 The vapor diffusion is performed in a sealed ampule and is followed by oxidation in an open tube. Present channel waveguide losses are high: approximately 15-20 dB/cm for the TM mode and 27-32 dB/cm for the TE mode in Z-cut substrates. After poling of the substrate, electro-optic modulation was observed. The effective electro-optic coefficient was determined experimentally as 3.3 ± 0.2 x 10^-10 m/V (over the frequency range 100 Hz-1 MHz) which is about 15 times greater than for the commonly used integrated optical materials, LiNbO₃ and LiTaO₃. Diffusions were conducted with the S35 radio-isotope in order to determine the sulfur distribution within the SBN. The atomic sulfur concentration was estimated to be approximately 4 x 10¹⁷ cm^-3 in the region from the surface to a 2.5 tim depth and there was still a significant concentration (approximately an order of magnitude smaller) at depths of > 20 μm.

The path that an emerging technology takes in becoming a commercial reality is discussed. Questions that must be answered are raised and two such questions relating to material quality and device design are discussed in depth.

Measurements on a variety of doped (magnesium and/or iron) and undoped lithium niobate crystals in the oxidized state demonstrate an Arrhenius dependence of electrical conductivity on reciprocal temperature between 460 and 590 degrees K. All of the crystals, regardless of doping, had roughly the same conductivity and activation energy (1.23 ev.) in this temperature range, implying that all of the crystals have about the same free carrier concentration and mobility. Based on these data a model is presented in which the enhanced photoconductivity of magnesium doped lithium niobate is attributed to a greatly increased free photoelectron lifetime, due to a correspondingly reduced trapping cross-section of Fe³⁺ for electrons. The smaller cross-section is due to a changed site for Fe³⁺ in magnesium doped crystals. Evidence for the new site is provided by ESR data. Photoconductivity measurements show that the trapping cross-section of Fe³⁺ for electrons in lithium niobate agrees satisfactorily with the value calculated from a simple theoretical model.

The design, fabrication, and testing of a high speed traveling wave directional coupler modulator for a guide wavelength of 810 nm is described. Application to high speed diagnostic systems is discussed.

Reports of organic materials with second-order nonlinear optical properties are reviewed.

The applicability of glassy polymer systems to integrated optics is discussed, including their manufacturability, integrability with sources, detectors, and drive electronics, and their optical and dielectric properties. A model nonlinear optical glassy polymer system was fabricated and evaluated. Its nonlinear optical properties compare favorably with those of other materials. Future optimization of nonlinear optical properties, along with the integrability, and high optical and dielectric quality of glassy polymers make this material class a promising one for use in integrated optics.

What follows is the edited transcript of a series of open discussions held Tuesday afternoon (4:20 - 6:00 PM) and Wednesday (10:30 AM - 12:00 PM and 5:10 PM -6:30 PM), January 21-22, 1986. Four separate discussions were held: 1. Open Discussion on Electrooptic Ferroelectrics Chairs: Doyle P. Skinner (Battelle) and Richard Becker (Crystal Technology, Inc.) 2. Open Discussion on III-V Semiconductors Chairs: Lynn D. Hutcheson (Honeywell, Inc.) and Robert L. Holman (Battelle) 3. Organic and Polymeric Electrooptics Chair: Gerald R. Meridith (E. I. DuPont de Nemours) 4. Wrap-Up Discussion on Status and Difficultiesin Practical Applications Chairs: Robert L. Holman (Battelle), S. Sriram (Allied-Amphenol) and Richard Becker (Crystal Technology, Inc.)