A variety of hybrid surface acoustic waves (SAW)-based integrated acousto-optic (AO) Bragg cell device modules including power and interferometric RF spectrum analyzers, space switches, tunable filters, frequency shifters and modulators, analog algebraic processors, programmable correlators, and other multichannel device modules have been realized previously in common LiNbO₃ substrate up to 1.0 X 3.7 cm² in maximum size. The prospects for realization of their counterparts in monolithic integrated format in a common substrate of InGaAsP material system are significantly enhanced recently. In the meantime, the magnetooptic (MO) Bragg interactions between guided optical waves and magnetostatic waves in yttrium iron garnet- gadolinium gallium garnet substrates have resulted in miniaturized MO Bragg cell modulators in analogy with the guided-wave AO Bragg cell modulators. Recently, the performance of such MO Bragg cell modulators has been significantly improved and the modulators have been integrated with ion-milled waveguide lenses to realize hybrid integrated MO device modules. Such MO modulators have been utilized to demonstrate a number of novel applications. In this paper, a review of some of the most recent advances in integrated AO and MO device modules and applications together with some unpublished new results are presented.

It is shown that nonlinear phenomena in quadratic media can be exploited in ultrafast, high-contrast all-optical switching. Two examples of transistor-like action, namely an all-optical switch based on the parametric down-conversion and a device exploiting vectorial cascading are considered in details. Influence of various control parameter including the effect of pulse walk-off on the performance of the envisaged schemes is discussed.

We present a new coupler device consisting of two stacked directional couplers (4 X 4-coupler as doubly stacked directional couplers). Coupling occurs in both, horizontal and vertical direction. The structure was fabricated by UV- patterning of a stack of spin-coated polymethylmethacrylate layers. It serves as a basic element to study the accuracy requirements for 3D waveguide patterning.

Optical signal regeneration is required for implementing transparent optical telecommunication networks. Critical nonlinear optical processing functions which must be improved for full 3R signal regeneration are optical clock recovery and clocked decision. A novel device type is presented, which can be used for both clock recovery and for decision unit. It is a laser, which is modulated by controlling the reflectivity of the laser mirrors. The concept of dispersive mirror modulation and the function of the developed multi-section laser are described. The required basic functions for signal processing are verified in experiments. This includes generation of optical data patterns by mirror modulation, optical control of mirrors at 5 Gb/s and demonstration of digital bistable switching characteristics. Self-pulsations are stimulated and optical oscillators with tunable frequency are realized. The devices are applied for all-optical clock recovery of 10 Gb/s data streams in a system environment. Clock recovery, decision, and optical amplifier all have a very similar device structure and operate with AR coated facets. Integrated photonic signal processing circuits can be built up with these elements.

In this paper we describe a new kind of all fiber polarization rotator based on the Faraday effect. Dynamic rotation of 20 degree(s) are achieved with bandwidth higher than 60 kHz. The effects of bending-induced linear birefringence are explicitly taken into account for the design of the sensing coil and the optimization of the device. With this configuration we have been able to design an electrically driven polarization scrambler working to a fixed frequency of 5 kHz suitable for the reduction of Polarization Hole Burning in Erbium-Doped Fiber-Amplifiers in long haul fiber links.

In this paper a rigorous numerical scheme has been presented for the analysis of a practical multimode interference-based device. The numerical results have been compared with published experimental results to show the validity of the numerical schemes presented. The vector finite element method has been employed to calculate the propagation constants and the least squares boundary residual method has been employed to calculate the excited modal coefficients at the discontinuity interfaces. The power transfer curve is shown for a 3 dB coupler and a 1 X 4 way power splitter is also investigated. The excess loss relating to the power splitter has been shown to be reasonably small around the design length. Finally a 2D multimode interference-based power splitter has been studied, and results reported.

It is known that the ion-exchange process in glass is described by a non linear diffusion equation whose solutions represent the index profile of the waveguide formed. The diffusion equation depends on the relative mismatch of the incoming and original ion mobilities, characterized by the parameter (alpha) . If they are equal, the diffusion equation becomes linear, and its solutions are normally used as an approximation for non-linear processes. Nevertheless, empirical solutions often provide a better modelization, but they must be found in each particular case of diffusion. In this work, we develop a perturbative method for solving the non linear equation, thus approximated analytical solutions can be obtained up to intermediate (alpha) -values ((alpha) equals 0.5). We have applied it to a simple surface thermal waveguide. By another hand, a proper dependent variable change is performed in the diffusion equation, and then the perturbative method is applied. It provides a solution much more exact that can be used with great accuracy up to (alpha) equals 0.8, which is a situation where Gaussian functions are normally used as empirical solutions. The method can be applied to more complex situations as buried waveguides, field-assisted processes and so on.

Non linear ion-exchange at surface and post-annealing processes are presented in a combined form to fabricate waveguide elements. Variational approaches are used to determine both the index profiles achieved and their waveguiding characteristics. Relationships between optical and fabrication parameters are derived. Their usefulness to both fabrication and designing of waveguide elements is shown.

A device that is capable of addressing an input pulse through different exits is presented. The controlling parameter is constituted by the intensity of the input beam. The scheme is based on an interesting property of a soliton in a waveguide with transverse gaussian refractive index profile.

Silica-on-silicon is one of the best materials structures currently considered for production of integrated optical devices, in particular for telecommunication and signal processing applications. Deposition of silica films can be advantageously attained by the sol-gel technique, which permits both a great flexibility in the refractive index definition and the possibility of doping with rare earth ions. In this work, we designed and modeled an integrated optical duplexer, intended as a component of a fully- integrated erbium-doped optical amplifier, operating in the third telecommunication window. The guiding structures are of the strip-loaded type, to be realized by the sol-gel technique onto a buffered silicon substrate. Design optimization and modeling was carried out by a software package which was developed on purpose in MATLAB environment, mainly based on the Effective Index Method. Here we report a general design procedure for the above said component, which takes into account industrial production requirements as well as device's performance.

New processes are developed to produce surface, ridge and buried sol-gel glass waveguides by photo-inscription using a ultraviolet light source. The fabricated waveguides demonstrate very low propagation losses (approximately 0.1 dB/cm). Several integrated optical devices such as cascaded Y-branch power splitters, directional couplers, Mach-Zehnder interferometer wavelength division multiplexers have also been produced.

A simple, effective and low cost laser writing lithographic system is presented. This system with a simple optical design and interferometric control of the alignment is able to produce smallest optical features as 1 micrometers wide with high quality edges to produce prototypes of integrated optical elements by ion exchange in research laboratories. Results of several kinds of mask that can be generated for this systems as well as some of the integrated elements produced are shown.

Birefringence as high as 10^-2 + 10^-3 in ion-exchanged planar waveguides has been measured by using a double Lloyd's interferometer. Birefringence seems to be produced by the distribution of the mechanical stresses induced during the fabrication process. A new point-by-point calculation to fit the experimental data is proposed which can give new information about the ion-diffusion process and the stress distribution.

Lateral ion-exchange, arising in the fabrication of waveguide elements by masking techniques, is modelized. The effective index method is used in order to analyze the effects on the light transmission when the side diffusion creates an effective graded index transition. Preliminary results are presented by using both a wave and geometrical approaches in the paraxial region. They show that the lateral ion-exchange modifies the paraxial parameters and it must be taken into account when the system's aberrations are corrected.

Silica-on-silicon waveguides have been fabricated doping core layer with phosphorus and germanium. Plasma Enhanced Chemical Vapor Deposition has been used to grow all layers starting from liquid metalorganic compounds. Co-doping assures chemical (Ge) and geometrical (P) homogeneity with optical fibers and allows to propagation losses of 1 dB/cm (not reflowed samples). Low cost, high realization rate and process compatibility with other microelectronic components make this technology very attractive for industrial production.

For integrated optical amplifiers to be efficient, losses must be minimized. An important source of losses comes from the coupling, and it is due to the modal mismatch between the amplifying channel waveguide and the connected fibers. In order to assess the coupling losses of our Er⁺- doped-glass strip-loaded waveguides, we observed the mode shapes by near-field imaging and compared them with the results of numerical simulations performed by using a 3D Beam Propagation Method. Important information about the critical parameters of the fabrication process have been obtained.

The coupled mode approach, together with the finite element method, and a combination of the least squares boundary residual and the finite element method approaches are used to obtain important design parameters to characterize directional coupler-based devices. Results are presented showing the power transfer ratio between such coupled waveguides and their application to characterize optical modulators and filters.

Glass integrated optics represents a viable approach to the development of cheap and robust passive components for communication, signal processing and sensing systems. Ion- exchange, in turn, is one of the most widespread technologies for the fabrication of optical waveguides in glass substrates. The choice of the substrate glass may affect critically the performance of waveguides and devices; thus, the results of an extensive characterization of ion- exchanged waveguides fabricated in a number of cheap, common commercial glass slides are reported here, with the aim of assessing the glass quality and therefore providing indications on the most effective substrate for components fabrication.

We report on the development and applications of integrated nonlinear interferometers including both Sagnac and Mach- Zehnder configurations for optical time division multiplexing systems. Details on principle of operation, device design and fabrication are provided. Moreover, by using such interferometers, all-optical demultiplexing and add/drop multiplexing of high speed data signals with bit- rates up to 40 Gb/s and 20 Gb/s, respectively, is demonstrated.

The problem of propagation of guided light in hybrid integrated planar waveguides is afforded in terms of Local Normal Modes. The approach is then generalized taking into account reflected modes arising when index discontinuity between adjacent guiding steps is significant. This is crucial for liquid crystal based waveguide devices. Transmission features in homogeneous as well as inhomogeneous and anisotropic waveguides have been considered in numerical computations. One of the worked examples can well explain previously reported experimental results.

Second harmonic (SH) generation in optical waveguides is widely studied for its many applications. In order to obtain efficient non-linear phenomena in waveguides, it is very important that the optico-physical characteristics of the fabricated waveguides are exactly those foreseen in the project. This because in practical applications operation wavelength and temperature can rarely be adjusted to achieve phase-matching conditions. The present work describes a model that, one fixed the operation conditions, finds the optico-physical characteristics of Ti:LiNbO₃ planar waveguides necessary to obtain SH generation and relates them to the fabrication parameters. Phase-matching conditions between the two interacting guided modes (fundamental and SH) are achieved by exploiting the material birefringence. The investigation is performed at a fundamental wavelength of 1.064 micrometers and at room temperature on Y-cut, X-propagation waveguides. The waveguides, fabricated according to our design, were then characterized at different wavelengths. Experimental tests of SH generation confirmed the goodness of the model proposed.

We show that dispersion compensation over 70 km of a standard optical fiber at 20 Gbit/s can be achieved by using a strip waveguide configuration which consists of two dissimilar guides and is only a few centimeters long. Moreover, any required amount of third-order dispersion can also be compensated for.