Early studies of LiNb0₃ indicated a great potential for a variety of uses based on the ferroelectric, piezo electric, electrooptic, and related properties, all dependent on the availability of single domain material. The actual steps which led to the first preparation of such crystals and the subsequent understanding of poling in this unique material are described.

The relative merits of LiNb0₃ and III-V semiconductors are compared for use in integrated optics. It is shown that their different material properties and fabrication characteristics affect their device performance. Device design must be optimized for the particular material used.

Gallium arsenide has been the premier semiconductor over the past 20 years as the host lattice for injection laser action, while GaAs itself and its III-V relatives in the GaAsP and AlGaAs ternary systems and the GaInAsP quaternary system have played important roles in the development of both sources (laser and LED) and detectors. Integrated optics carries this further in seeking to use the GaAs (or related semiconductor host) as the medium for optical waveguides, couplers, reflectors, etc.; with all functions including sources and detectors fabricated within a single chip. The materials requirements for this more complete utilization of the semiconductor set the priorities for the topics discussed in this paper. These include the physical characteristics of the zincblende lattice in which GaAs and its fellow III-V semiconductors crystallize; a lattice which is cubic, but is anisotropic in some significant respects. Several aspects of the optical and electronic properties are noted, the latter in regard to the active driving devices (such as FETs) which one wishes to incorporate into the same monolithic chip. Crystal growth methods for GaAs are briefly reviewed, drawing attention to the differences between the requirements for an int-egrated optoelectronic application and those (less stringent) for purely electronic microwave or digital applications.

The wide compositional variability of the LiNb03 phase in terms of Li/Nb ratio and oxygen content can be used to optimize the processing of optoelectronic devices. Interactions of these two types of nonstoichiometry can lead to unforeseen consequences, however. As an example, it is shown that reduction drives LiNb0₃ toward the Li20-rich phase boundary, and experimental observation suggests that this can result in phase separation and loss of transparency.

Single crystal fibers of four refractory oxide materials (Aℓ20₃ , Cr:AZ₂0₃ , Nd:YAG and LiNb03) have been grown by a miniature pedestal growth technique. The growth apparatus employs novel electronic control, mechanical and optical systems enabling growth of high optical quality fibers. All four materials exhibit similar growth characteristics and yield fibers of comparable quality. Measured optical waveguide losses at 632.8 nm for a 5 cm long 170 μm diameter CrℓAZ₂0₃ fiber were 0.04 dB/cm.

The knowledge of the Ti:LiNb03 waveguide formation mechanism is required to understand the factors influencing the waveguide optical characteristics, performances, quality and reliability. Despite the increasing importance of the Ti:LiNbO3 waveguides in the development of hybrid integrated optical devices, the Ti indiffusion process is not still completely understood. This paper reports the results of a study on the different compounds which form during the process which leads to the Ti diffusion in LiNbO3 and on the effect of Lle presence of water vapours on their growth kinetics. Ti indiffusion process on Z- and Y- cut substrates and in different (dry and wet) atmospheres was investigated by many microanalytical techniques. Some correlations between the structural and optical characteristics of the waveguides are also reported.

We describe fabrication conditions which produce proton exchanged waveguides with long and short term index stability. We present also the surface index change and effective diffusion coefficients associated with exchange in melts of varying concentration, from pure benzoic acid to mixtures containing up to 4 Mole % lithium benzoate. Infrared absorption measurements supporting our explanation for the causes of index instability are presented.

This paper reports on the relationship between materials analysis studies and optical characterisation of proton-exchanged lithium niobate waveguides. Close agreement in predicted waveguide depths is found on Z-cut LiNb0₃ substrates, while a consistent discrepancy is found on X-cut LiNb0₃ substrates.

Single-mode, planar and channel waveguides were fabricated in fused silica substrates by sequential, high-energy (100 keV and 300 keV) nitrogen ion implantations. The planar waveguides were characterized by measurements of waveguide loss and guided-mode effective refractive indices. It was found that a post-implantation annealing treatment reduced the waveguide loss to a value as low as (0.1±0.1)dB/cm. Chemical characterization of the implanted and annealed surfaces, carried out by means of Auger electron spectroscopy, showed that nitrogen was incorporated into the silica glass as a result of the N+ implantations. Channel waveguides were also fabricated (using photolithographically-generated implantation masks in thin gold films) and evaluated in terms of their mode refractive indices.

A simple technique for the fabrication of integrated optical circuits on a GaAs substrate employing LPE epitaxial layer growth of AℓGaAs and GaAs and subsequent wet chemical etching to define the circuit structure is described. Several useful structures employing lasers, waveguides and detectors are discussed along with performance specifications that we have achieved in our laboratory. Finally, the correlation of waveguide loss to epitaxial layer uniformity is described.

Integrated optical circuits operating at wavelengths from 1 to 12 microns and fabricated monolithically on a GaAs substrate would have a tremendous impact on signal processing systems. These circuits would afford the ultimate merger of the VLSI electronics and integrated GaAs optoelectronics, as well as the monolithic integration of microwave electronic devices such as Gunn diodes and Schottky gate FET's with GaAs optical components.1 Such GaAs components include planar and channel waveguides, parallel channel directional couplers, electro-optic (EO) modulators and switches, laser diodes, acousto-optic modulators, and detectors.2 This paper focuses upon the design and fabrication by proton implantation of the necessary fundamental guided wave components in GaAs for operation at λo = 1.3, 3.4, and 10.6 μm wavelengths. The objective is to produce waveguide designs with less than 3 dB/cm optical propagation loss at each wavelength of interest. Specific range-energy curves for proton implantation in GaAs to produce the desired waveguide characteristics have also been developed.

A process has been investigated for the fabrication of overlapping charge transfer electrode structures in charge-coupled devices on gallium arsenide with ion implanted active channels. The electrode metal was aluminum and the interelectrode isolation medium was anodically formed aluminum oxide. A CCD with ion implanted active channel is desirable since this form is most compatible with standard GaAs integrated circuit fabrication and the latter usually forms an important component of a monolithic CCD imager. For good dynamic range the channel noise must be kept to a minimum. Hence, for this purpose a computer model has been developed for simulating charge transfer through an implanted channel to aid in the design of the transfer electrode structure and the channel profile.

Interferometric lasers having composite cavity structures are studied for longitudinal mode stability and wavelength tunability. Interference between cavity fields results in a wavelength-dependent loss providing a built-in mechanism for longitudinal mode selectivity. Experimental results on a selected number of uniformly and separately pumped interferometric lasers are reviewed and analyzed.

Use of optical waverides formed in lithium niobate single crystals is contemplated in a wide variety of promising modulation, switching, computation, and signal processing components. One factor, however, may stand in the way of this development: the degree to which the waveguides are susceptible to laser-induced performance degradations known as optical damage.

Two competing methods of optical waveguide formation in LiNb03 are the indiffusion of Ti and the exchange of Li with protons in an acidic solution. Numerous reports, both pro and con, have been made concerning waveguides fabricated using these two methods. In this paper, we would like to compare guided-wave Mach-Zehnder interferometric modulators fabricated using both of these methods. We will discuss the fabrication and testing of these devices including measurements of Vff, the voltage required to drive the modulator from its maximum output to its minimum output, the electrode capacitance, optical damageability, and waveguide bend and branch losses.

High power optical performances of Ti-indiffused and ion-exchanged waveguides were investigated and discussed. It was experimentally confirmed that Ti-indiffused waveguide suffered a serious optical damage at the output power density less than 0.1 mW/mm at A = 0.6328 pm. For x-propagating guided waves in y-cut crystal, the throughput decay time, by which we could characterize the dependences of optical damage, was revealed to be inversely propor-tional to square of initial guided power, P2, for TE modes, and to P3 for TM modes, and also confirmed to increase with an exponential function of wavelength λ. No optical damage was found for z-propagating guided waves. Proton-exchanged waveguides exhibited to have a good damage resistance. Their surface acoustic wave(SAW) performances, however, were found to be degraded; an IDT's insertion loss of 45 dB was measured, which was much larger than 13 - 14 dB available for Ti-indiffused waveguides. According to the experimental results of infrared absorption spectra, we speculate that the deterioration of SAW performances is attributed to the formation of a HNbO₃ phase. A preliminary study using electron spin resonance(ESR) at 77 K provided us a good evidence of the close relation between impurities such as iron and free electrons in the crystal under UV light irradiation.

Experimental results on the photorefractive effect in Ti-indiffused LiNbO₃, directional couplers at GaAs and He-Ne wavelengths are presented. The photorefractive effect has been observed as drift in the switching state of this device at GaAs wavelengths (0.81 μm and 0.85 μm) for intensities (powers) as low as 32 W/cm² (3.2 μW). Analysts of this effect indicates refractive index changes as large as 2 x 10^-4 are occurring at λ = 0.63 μm. In addition, an analytical model of the mode profiles of Ti-indiffused LiNbO₃ channel wave-guides for calculating the coupling characteristics of diffused directional couplers is presented.