Buried planar optical waveguides made by a purely thermal back-diffusion K⁺-Na⁺ ion-exchange process have been demonstrated, for the first time, on soda-lime glass substrates. The potassium ion concentration profile was determined using a scanning electron microscope (SEM) technique which was then correlated to the numerical simulation of the ion-exchange fabrication process.

The thermal behaviour of wavelength demultiplexers, integrated on InGaAlAs epitaxially grown by MBE on InP, is reported. The overall performance is due to the superposition of two mechanisms: a pure thermooptic effect, which allows a tuning of the order of 1 A/°C, and an elastooptic effect, caused by induced stress, which can lead to much higher temperature sensitivity, up to 1 nm/°C or more.

A miniature fiber-optic Laser Doppler Velocimeter (LDV) is demonstrated which uses a proton-exchanged LiNb03 multi-function integrated optic circuit for signal processing. The system utilizes a high-power (7.5 mW out of the fiber pigtail) 0.8- micron laser diode with short coherence length (approximately 1 cm) as the source and coherence multiplexing techniques to provide a phase-insensitive fiber-optic probe for monitoring moving or vibrating parts. The fiber-optic LDV provides 55 dB signal-to-noise ratio for 3 kHz bandwidth, even when monitoring parts with poor optical surfaces (1 % reflectivity). Operation of the system is demonstrated by monitoring a mirror vibrating at 5.7 kHz with 36.8 nm peak-to-peak deviation. The optical components and all electronic circuitry except for the DC power supply is housed in a 11.5 x 10.5 x 4.2 cm package which weighs 0.6 kg. The entire system operates on a ± 15 V, 300 mA supply. The small size, light weight, low power requirements, and phase-insensitive fiber-optic probe make the fiber-optic LDV appealing for a number of industrial and medical applications.

Mode index measurements of optical slab waveguides fabricated by proton-exchange with pyrophos-phoric acid in z-cut LiNb03 have been made. The index profile is approximately a step with an index increase of .131 at T = 200°C. In addition to establishing formulae for the effective diffusion constant (De) and guide depth (d) for a given diffusion temperature and time, an investigation of the often neglected anisotropic nature of these wavercuides is presented.

Proton-exchanged waveguides fabricated using phosphoric acids have been investigated systematically and compared with guides made in benzoic acid. A novel electrooptic phase-modulator device using proton-exchanged waveguides is also described.

Optical studies of phase modulators, polarizers and directional couplers realized in X-cut LiTa0₃ fabricated by the proton-exchange method (PEM) are described. The ability to temperature adjust the coupling lengths of optical directional couplers is discussed in detail. The above guided-wave optical components can be integrated to perform certain optical signal processing functions such as extracting the rotation rate information in fiber-optic gyroscopes.

The material properties and their impact upon design and structure of planar and channel waveguides is presented. Comparison to other silver ion exchange techniques will be discussed.

During the last two decades, lithium niobate has been extensively studied for applications in integrated optical circuits. However, it is difficult to integrate lithium niobate optical devices with semiconductor electronic devices because of incompatibility of the materials. In recent years, semiconductor materials are emerging as the main contender in applications; these materials have the advantage that both the optical and electronic devices can be integrated. Further, the semiconductor technology has advanced rapidly allowing us to engineer device parameters very precisely. In semiconductor opto-electronic devices, i.e. bulk and quantum well structures, mainly electro-absorption has been used for amplitude modulation of light. The electro-refraction effect is most useful for devices employing phase modulation techniques but this effect cannot be effectively utilized in semiconductors since the strongest electro-refraction effect is near the absorption edge of the material. Recently, organic materials have been shown to have electro-optic coefficients of equal or larger than that of lithium niobate. There are major advantages of organic materials: (a) the organics can be deposited on semiconductor substrates and therefore both electronic and optical circuits can be integrated (b) in organic materials the electro-refraction can be effectively utilized to obtain both amplitude and phase modulation (c) the organic material composition can be adjusted to satisfy some device requirements. In this paper, a comparison of these material systems will be made in terms of device applications.

Interest in organic electro-optic materials for integrated optics has been increasing with the realisation of improved electro-optic co-efficients for these systems. Incorporation of active organic molecules as side groups on a polymer backbone seems to be the best method of achieving a poled polymer film with properties suitable for planar processing techniques. Channel Waveguide manufacture has been achieved on a number of substrate materials using such a polymer system with waveguide losses of less than 1 dB/cm. Active components have been fibre pigtailed and packaged with a Vpi of less than 10 volts. A review of the technologies for preparing such components will be given along with an assessment of the further applications and developments envisaged with these materials. Comparison will be made with currently available integrated optical components, critically assessing the state of the technology.

Polymeric optical waveguides for integrated optical devices are of current interest for their potential application in very high bandwidth opto-electronic systems. We report our progress in defining and characterising channel waveguides in polymers having large electro-optic coefficients. The waveguide patterns are formed as etched channels in a polymer cladding layer. Further layers deposited onto these channels form 2-dimensional waveguides with monomode characteristics at a wavelength of 1.3 microns. The mode size is controllable and may be optimised for fibre mode coupling to minimise the coupling loss. Electro-optic phase and amplitude modulation is demonstrated for slab and channel waveguides. We report values for the off-resonance electro-optic coefficient in poled polymer films somewhat higher than the largest value in lithium niobate. The implications of such device structures for applications in high performance multi-GHz amplitude modulators are discussed. In particular, the large values of n3r and the near equality of the optical and microwave refractive indices indicates that these polymers will have significant advantage over traditional inorganic materials for wide bandwidth integrated optical modulators.

Silica-based single-mode waveguides, fabricated on silicon substrates by a combination of flame hydrolysis deposition and reactive ion etching, have low propagation loss and low fiber coupling loss. High controllability in the silica-based waveguide fabrication leads to directional couplers with an accurate coupling ratio can be fabricated. Based on these advantageous features, we have successfully constructed a variety of guided-wave devices such as multi/demultiplexers for 1.3 and 1.55 μm wavelength, 2 x 8 couplers, ring resonators, and Mach-Zehnder interferometers which operate as optical switches or multi/demultiplexers with various channel spacings from 0.008 nm to 0.25 μm.

Lithium Niobate modulators have been available commercially from several vendors for a number of years, and have found their way into a very broad range of Research and Development1activities, some of which were discussed in an earlier article . However, with the possible exception of the fibre-optic gyro, it is probably safe to say that systems applications for this class of device are still relatively limited and their exposure beyond the domain of optical scientific research is increasing only slowly.

We suggest two Computer Aided Design algorithms, PAD and PAL, for the design of Ti:LiNb03 directional coupler based photonic switching architectures. PAD (Photonic Architecture Designer) generates higher order architectures by taking a lour order architecture as a rearrangeably nonblocking unit cell used as a building block. It then proceeds to test the generated netlist for nonblocking capability. PAL (Photonic Architecture Layout optimizer) takes a given architecture as input and finds the optimal layout with respect to coupled power between waveguides, substrate real estate utilization and number of crossovers. The directional coupler is taken as the unit cell and perturbed (translated/rotated) till the cost functions described above are satisfied. The inter-connecting waveguides are treated as semi-elastic structures which satisfy constraints like minimum intersection angle, interguide spacing and minimum radii for bends in integrated optic waveguides. Several practical constraints are imposed on the layout algorithm to ensure a realistic layout design.

In this paper, the conceptual scheme and design of a new configuration of hybrid integrated optical circuit for on-board data preprocessing are discussed. Single components and related fabrication techniques are analyzed. The proposed configuration shows high performance both of each integrated component, and of the whole circuit.

Integrated optical electrooptic modulators can play a crucial role in the sensing, control and processing of microwave and millimeter wave signals of phased array antenna systems. Integrated optical single side band modulators with narrowband resonant microwave electrode structures can serve as ideal microwave/optical transducers for antenna elements. The single side band modulation scheme allows the encoding of the microwave frequency and phase information onto an optical carrier shifted by the microwave frequency. This allows the use of coherent optical techniques for beam steering and signal processing of microwave signals used in phased array antenna systems.

Using the methods of x-ray double crystal diffraction (DCD) and x-ray DCD topograph as well as photolumincence (n), InGaAsP/InP single heterojunction interface ( SHI) lattice mismatch Influcence on LPE crystal quality is studied. The experimental results indicate that this kind lattice mismatch will lead to impurity condensing, dislocations and defects as well as nonradiation recombination centers increasing in LPE InGaAsP epitax layer and induce composition gradient in the direction of crystal growth.

Measurements are reported of the photovoltage decay across a selectively contacted GaAs doping superlattice as a function of time following cw and picosecond laser excitation. The photovoltage decay is measured under conditions where electrons and holes can recombine through an external circuit in parallel with internal recombination mechanisms. Measurements of the intensity dependence of the steady-state photovoltage are also reported.

Integrated optical wavelength demultiplexers fabricated by K-Na ion exchange on soda-lime glass, based on the two mode interference principle, are described. Channel isolation up to 26 dB is achieved as well as channel spacings between 70 and 220 nm, with guide insertion loss lower than 2 dB. Polarization-sensitive behaviour is observed, which can be exploited to produce polarizers; polarization ratios up to 126:1 have been obtained.

A GaAs/AlGaAs guided-wave optical ring resonator with a p-i-n diode/heterostructure has successfully been fabricated. A finesse of 3 and an extinction ratio of 5.9 dB have been measured.

A new on-wafer bidirectional nondestructive measurement method is demonstrated for measuring losses in three dimensional integrated optical waveguides. A thermally oxidized silicon wafer is used as substrate for silicon nitride multimode waveguides. The measurement is based on p-i-n photodetectors integrated near the waveguide. In order to eliminate the effect of different sensitivities of adjacent p-i-n detectors, the light is launched separately to both ends of the waveguide. The method can be applied to test structures in optoelectronic integrated circuits (OEIC's).

Low-loss waveguiding at X = 1.3 µm has been observed in a partially strained, 10-µm thick, single-crystal layer of Ge0,1Si0.9 grown by chemical vapor deposition on a high-resistivity (100) silicon substrate. The TM-mode propagation loss in the multimode planar guide was less than 1.9 dB/cm. Device applications of GeSi waveguides are discussed.

We discuss the numerical modeling of integrated optic devices with emphasis on three-dimensional electric field propagation techniques applicable to strongly guiding, longitudinally varying waveguides. We find that despite the inevitable tradeoff between numerical precision and speed, rapid paraxial methods such as the split-operator finite difference procedure are sufficiently accurate for typical rib waveguide problems. We also introduce and solve a new non-paraxial wave equation for electric field propagation. With this formalism we are able to verify explicitly the validity of our Fresnel eauation results.

A numerical model for field assisted ion-exchange in two dimensions is an essential tool in designing channel waveguide devices with improved performance. The model presented here includes for the first time in 2-D the effect of unequal mobilities and of thermal diffusion on the resulting concentration profile of exchanged ions. This allows the modelling of graded index structures.

In the theoretical modeling of the performance of optical directional couplers with nonuniform waveguide spacing, coupled-mode equations involving varying coupling coefficients are often solved numerically. We show that, when the waveguides are dissimilar, direct numerical integration of the equations may result in variation of the total power along the coupling direction. A modification of the numerical scheme is proposed to make the numerical calculation satisfy power conservation, as is required in modeling a realistic coupler with very low insertion loss.

The waveguide optical system represents a critical item in the implementation of integrated optical analog signal processors like correlators and spectrum analyzers. Here design and modeling criteria of different grating (Fresnel) lenses are described, together with some experimental results.

The design optimization and implementation results of a 3-branch optical switch, operating at 1.32 gm, in z-cut Ti:LiNb03, are presented. A theoretical model based on the Beam Propagation Method was used for the design optimization. Power extinction ratios of 15.9dB (P1/P2) and 20.1dB (P1/P3) were obtained experimentally at a voltage of 32V for side switching. Central switching of 16.1dB was achieved at 35V. Good agreement between the theoretical and experimental results was established.

Finite element solutions of the planar nonlinear optical waveguide are presented by incorporating a simple iteration scheme. Both film guided and surface guided modes are presented for symmetrical and nonsymmetrical structures. Bistability and hysteresis nature of the modes for these structures are also illustrated. This technique can be readily applied to a wide range of optical waveguide devices, including 2-D structures, with arbitrary nonlinearity and transverse index profile.

A novel method of glass-sealing optical fiber inside sleeves permits coupling the fiber to an optoelectric device light source, while providing hermeticity and optical-signal integrity. The glass-seal development overcomes limitations inherent in epoxy and metal-solder techniques.

Semiconductor optical amplifier packaging is described using a localized cooling soldering approach for attaching and aligning two separate single mode fibers. The alignment process is more critical for amplifiers than for lasers because fiber coupling loss directly reduces any gain achieved by the semiconductor. The localized cooling method permits use of the same solder at each fiber attachment point eliminating the need for a higher temperature step solder approach. The alignment efficiency or ability of the package to maintain an attached fiber positionally compared to an unattached aligned fiber appears equivalent to what is achievable with laser packages. A description of special issues and problems relevant to the packaging of amplifiers is also presented.

We report the alignment details for efficient direct coupling of a single-mode Nd fiber laser to a multimode, highly divergent laser diode pump source. A double-clad fiber structure with a rectangular shape and large NA (0.4) allows for efficient excitation of the single-mode core in a simple end-pumped configuration. Pump conversion efficiency of up to 25% is observed, with CW output power to 0.12 Watt in the case of a single laser diode pump.

Far-Field pattern of 1.3µm InGaAsP/InP DCC structure semiconductor laser is calculated by the strong coupling method. Experimental data agree with the theorticat results with the FAHP beam divergence 0 i < 300. Space coherence characteristic of 1.3pm InGaAsP/InP DCC structure semiconductor laser is good. The impeltent action of the 1st active layer and the selection mode action of the 2nd active layer F-P cavity are analyzed for DCC structure laser.

The damage due to ionizing radiation on titanium diffused lithium niobate waveguide devices is investigated. Several waveguide devices containing straights, bends, and directional couplers are irradiated with both gamma radiation and high energy electrons. Passive optical measurements as well as in-situ measurements are performed on the exposed waveguide devices. It was found that the waveguide devices were hard to gamma radiation at doses up to 3.8 x 10⁶ rads. Also the waveguide devices showed small permanent changes to high doses (3300 Mrads) of electron radiation.

Three materials commonly employed in opto-electronic intregrated circuits were evaluated for radiation-induced optical attenuation in the range 300 nm to 3000 nm. These include optically clear epoxy and crystalline lithium niobate after Co-60 exposure and crystalline tellurium dioxide after mixed gamma/fast-neutron exposure. In all these materials, however, induced loss was restricted to shorter wavelengths; attenuation induced at the telecommnications windows near 850, 1300 and 1550 nm was <0.1 dB/cm.

A short discussion of recently reported radiation induced responses of Ti:LiNbO₃ directional coupler waveguides and silica birefringent fibers is presented. Based on experimental data, a hypothesis is advanced wherein known photorefractive damage mechanisms in Ti:LiNbO3 guided wave devices may be enhanced by electron induced color centers. Nonequivalent transient absorption and recovery data for a proton irradiated single mode polarization preserving fiber is also presented. An explanation is offered to account for the transient absorption processes based on color center formation and nonequivalent alteration of the fiber birefringence.

An investigation of electro-optical mixing using a GaAs MESFET has been performed. Since the optical signal illuminates the exposed GaAs regions along the gate of the MESFET, fiber to MESFET coupling is analyzed. It is shown that because the MESFET gate region is not designed to be compatible with the fiber core geometry, only a small fraction of the photons available for illumination contribute to the electrical output of the MESFET. We have shown electro-optical mixing performance, achieved when the gate region is illuminated with an optical signal modulated at 400 MHz, and an electrical signal at 1 GHz is applied to the gate. The MESFET output measured on a spectrum analyzer shows upper and lower sideband frequencies at 1400 and 600 MHz respectively. The mixer circuit implemented, resulted in 69 dB LO to RF isolation and perfect LO to IF isolation. A conversion loss, which included fiberoptic link loss, of 48 dB was measured. Mixing with LO frequencies of up to 3.8 GHz were achieved.

This paper presents design, fabrication and testing of high speed laser diode transmitter and receiver modules capable of handling data rates of 1GB/s. The circuits have been fabricated using hybrid thick film process to incorporate high power densities,yield and reduced parasitics.Both transmitter and receiver operate at 1300nm wavelength, and can process ECL signals with a single 5V supply.Computer aided design and surface mount techniques have been employed for the development of these circuits, which have demonstrated excellent stability and reliable performance.

To implement a pressure transducer for avionic systems, the use of an integrated optic Mach-Zehnder interferometer in glass was considered. A previous study of planar waveguides and the experimental characterization of channel waveguides helped define the fabrication process and select the type of glass substrates to be used. Opto-mechanical stress analysis was used to predict the effect of pressure on waveguides. Phase sensitivity is found to be adjustable with variations in the loading configuration, waveguide path and mode polarization. The behavior of straight channel waveguides under stress was then verified experimentally. A near-zero-phase-imbalance interferometer operating at a wavelength of 810 nm was designed, fabricated and tested. Its intensity modulation response to pressure is stable with good contrast. But in order to directly access the phase modulation information, an imbalanced interferometer was designed for interconnection to a frequency-modulated laser source. Accurate pressure measurement, insensitive to spurious intensity fluctuations, could thus be performed.

A large number of single-polarization 2x2 lithium niobate switches have been fabricated for use in a bit serial optical computer. The switches come six to a package and have a single drive voltage of less than 5 volts, insertion loss less than 5 dB, and crosstalk less than -20 dB. At ten chips per 3-inch wafer, a lot of 6 wafers yields as many as 360 switches, making packaging and testing far more costly than chip fabrication. After one die per wafer passed acceptance testing, the rest of the dice were packaged in commercially-made Cu-alloy DTP's without further testing. Standard single-mode fibers were attached twelve at a time using Si-V-groove chips. Exercising our process by making chips in modest volume leads us to conclude that lithium niobate devices are made with a manufacturable process that can be tuned to provide a high yield of packaged devices at a cost comparable to other photonic products.

Three themes characterize many of the recent developments in lithium niobate-based integrated optics at Crystal Technology: integration of multiple components into optical guided wave circuits of increasing complexity; development of polarization-independent or polarization-controlling components; and packaging, pigtailing, and hybrid integration initiatives.

The use of subsequent MgO indiffusion to bury Ti indiffused waveguides in LiNbO₃ is shown to reduce the surface scatter contribution to waveguide propagation loss. Assessment of waveguide propagation loss foil- non-buried and buried waveguides at wavelengths 0.851μn, 1.06μm, 1.32tim and 1.52μm show a λ dependence for non-buried waveguides, indicating a surface scatter mechanism. Buried waveguide propagation loss exhibits no such dependence on wavelength, with a propagation loss of i0.25dB/cm over the wavelength range. Reduced excess loss of buried λ- junction waveguide structures, in Mach Zehnder intensity modulators, is demonstrated. This improvement is ascribed to increased light confinement and reduced scatter in the vicinity of the bifurcation region. Active performance of phase and intensity modulators, with non-buried and buried waveguides, indicate no significant change in required drive voltage. This is due to a choice of MgO conditions which lead to sufficient waveguide burial to reduce propagation loss, but to little change in Ti diffusion depth and hence optical/electrical field overlap characteristic.

High quality LiTa03 devices capable of operating at high optical power levels are reported. Optical powers of up to 70 mW caused no optical damage at 0.82 μm. The waveguides exhibited high polarization extinction (51 dB), low loss ( < 0.25 dB/cm), low fiber-to-waveguide coupling loss (0.5 dB per junction) at 0.82 μm, and maintained the same r33 coefficient as the bulk.

The development of integrated optical circuits has made use of three different material groups: glass, electro-optic crystals, such as LiNbO3, and semiconductors. The prominent properties of each material group are well known. Glass and LiNbO3 waveguides are cheap, easy to fabricate and have lower insertion loss than semiconductors. Moreover, LiNbO3 has high electro-optic coefficients allowing control of the phase, polarization and amplitude of the guided light. Semiconductors offer band-gap engineering and carrier doped layers allowing the fabrication of waveguides, detectors, sources and high-speed electronics.

We present the study on the magneto-optic waveguides developed in recent years with emphasis on the fabrication of channel waveguides and integrated-optic circuits in the rare-earth iron garnet films. Results on the measurements positively using the channel waveguides are shown.

The history, development status and future trends of integrated optics technology in Taiwan were summarized in this paper. Several groups including academic and industrial research manpower had engaged in the technology developments of integrated optics for seven years or more in Taiwan. So far, all the budgets were supported by government. The research contents include device simulation, device design, device fabrication and system integration on substrates of Si, GaAs (InP) and LiNb03 for electro-optics applications. The topics can be summarized as surface acoustic wave (SAW) devices, electro-optics switch and modulator, integrated optics pick-up devices, design packages of optical components, optical filter and delay line. The future trends contain the optical signal processing, wavelength filter, wavelength multiplexer / demultiplexer acousto-optics and electro-optics devices and subsystems, optical coupler and system integration technologies etc. All the approaches of each topic depends on the strategy of applications.

The collinear magnetostatic wave - optical wave interaction is considered. Emphasis is placed on the effect of magnetostatic and optical losses on the conversion efficiency between optical modes and on the interaction bandwidth. It is found that the introduction of an "effective interaction length" provides a straightforward refinement of existing theory applicable to situations with small total energy transfer between optical modes. A weak-coupling model for the interaction bandwidth in the presence of loss is also described. The utility of the model is tested by comparing experimentally obtained interaction bandwidths against theoretical predictions, at center frequencies between 0.5 and 12 GHz. Taking optical and magnetostatic wave losses into account in the theory results in a significant improvement over lossless coupled-mode theory. Some experimental techniques and applications with magnetostatic waves are illustrated.

We have developed a new technique for the interfacing of optical fibres to integrated optics which is based on flip-chip solder bonding. This approach eliminates the need for precise manipulation of the fibres during final assembly and produces a very stable interface which is suitable for the assembly of integrated optical circuits containing multiple optical fibre and electrical interfaces.

The present work describes the characterization of internally developed epoxy ridge optical waveguides which exhibit low propagation loss (0.3 dB/cm at 1.3 μm), high environmental stability (low sensitivity to moisture), have smooth walls (100 nm sidewall roughness), and high temperature stability (275°C). The techniques used to fabricate these waveguides are compatible with the planar processes used in the manufacture of high performance electronic packages.

This paper reviews the process of implantation induced multiquantum-well (MQW) mixing in GaAlAs/GaAs and GalnAs/InP MQW structures. The effects of varying the implanted ion dose and the annealing temperature and time on the properties of the mixed material are described. The application of the process to the fabrication of disorder delineated stripe optical waveguides in GaAlAs/GaAs MQW structures using silicon implantation is also discussed.

We demonstrate here the active mode locking of an external cavity comprising a brewster angled laser diode and a brewster angled rectangular core optic fibre to produce almost transform limited pulses of 9ps duration.

Analyses and experimental results of microwave semiconductor laser nonlinearity are presented. Various system applications employing the device nonlinear characteristics are discussed. For example, a high performance Ku-band fiber optic link with a system signal-to-noise ration (SNR) of better than 120 dB/Hz was demonstrated at an IF of 70 MHz. Also, the measured link SNR better than 100 dB/Hz was achieved at 26.5 GHz with frequency up-conversion.

For high bit rate and long distances numerical transmission systems, or for analog broad band applications, a stable single longitudinal mode operation of semiconductor laser diode is required. Distributed Feedback lasers (DFB) are very interesting for this type of system. However, the optical feedback, due to Rayleigh backscattering, and light reflected by the fiber and the coupling circuit can disturb the good operation of the diode 1. In order to overcome this problem and to limit the system penalty induced by the optical feedback, two ways are possible and complementary. First, optimize parameters of the laser diode structure 1, 2. A second way is to introduce an optical isolator inside the laser module.

We present the characteristics of Thalium-Zirconium and Natrium-Calcium glasses used for manufacturing of optical waveguides and fibers. The glasses have been melted and processed in several tens of different microsamples using originally developed sensitizing technology. Technological facilities have been presented. Ten samples of interferometric optical guided-wave temperature sensors have been constructed and their material and performance characteristics debated. The sensitivities of optical sensors of up to 300 rad/mK are accesible with this glass system. The thermally induced stress in the waveguides adds or substracts up to 10% of this sensitivity.

This paper reports a practical technique for making a high-performance semiconductor optical amplifier by combining tilted-cavity and a simple anti-reflective facet coating. Gains of up to 29 dB are reported at a gain ripple of 3 dB.