In the present paper we review the state of the art of two complementary propagation techniques with applications for integrated optics device modeling: the Finite-Difference Time-Domain and the Beam Propagation Method. In both cases we focus on their main features such as the types of propagation schemes and the material effects that can be modeled. In addition, we also consider a 2D mode solver based on a complex root finding procedure - a representative mode solving technique that is of significant interest for design and modeling of leaky mode based devices. Each of the methods is illustrated with appropriate simulation examples of devices and waveguide structures being of current research interest: photonic band gap structures, waveguide gratings, ARROW waveguides etc. The selected examples show the power of the methods as well as the consistency and the complementarity of their results when applied together.

Dielectric resonators promise high functionality components for future optoelectronic integrated circuit applications. Accurate modeling of these components is a prerequisite to their successful deployment in innovative configurations. This paper will compare and contrast a wide variety of simulation techniques, developed by ourselves, that can be used for design. These encompass, (1) ful wave analytical integral equation methods which yield high accuracy and fast computation but are structure specific, (2) direct numerical simulation based upon high performance finite difference schemes which offer significant flexibility at the cost of computational overheads, (3) fast yet accurate semi- analytical approaches which can often provide sufficiently accurate result for the purposes of practical design at a fraction of the effort, in terms of both computational and pre-processing analysis as required by the former methods. The relative merits of the methods will be illustrated through their application to the design of practical components for a variety of systems. These will include examining the resonant frequencies, the quality factors and the field profiles of the lower order modes and the whispering gallery modes of dielectric resonators. Specific applications of interest are in the fields of filters, coupling elements and lasers.

In this paper system applications, geometry, physical effects and materials of optical switching devices are reviewed. Main system scenarios are presented and some key features such as size, loss, speed, scalability and granularity are highlighted. Two principal categories of optical switches are considered, i.e. guided-wave switches and free-space switches. In the first category some sub- classes have been identified according to their geometrical configuration, principle of operation and, then physical mechanism and materials. As for the geometry, the most frequently used configurations are briefly described together with their advantages and disadvantages. Different physical effects suitable to obtain the index change, which the switching function is based on, are also described with reference to the material substrates. Switches based on semiconductor optical amplifier gate are also analyzed. In the free-space category the main sub-classes are represented by the opto-mechanical devices and micro-opto-electro- mechanical systems switches. The last technology combines the free-space interconnecting with the integration capability on a single silica chip. The main advantages such as the ability to scaling up to large switch fabric and some issues such as packaging and reliability are analyzed. Finally, devices based on polarization change, acousto- optics interaction, total internal reflection and holography are illustrated.

The development of dense WDM-systems for growing data transmission rates requires optical components with well defined spectral properties for multiplexing and demultiple4xing, gain equalization, dispersion management, and routing. Among the various concepts for realizing WDM- devices those based on guided waves have achieved a high performance: Arrayed Waveguide Gratings (AWGs) for high channel counts fabricated with a silica-on-silicon technology and Fiber Bragg Gratings for their performance in gain equalization and dispersion compensation. They also are used in ADMs and multiple WDM-sources.

Diffused quantum wells (DFQW) optical devices have been widely investigated for use in optical electronics integrated circuits. In this paper, we report on the performance of five-period DFQW optical amplifiers and modulators. The result show that the QW amplifiers and modulators maintain at single guiding mode operation after the QW structure has been annealed. The running range of the operation l wavelength of QW optical amplifiers is 34 meV without a significant degradation in the modal gain peak by interdiffusing the QWs. The QW interdiffusion was accomplished by P⁺ ion implantation to the upper region of the top cladding layer of the multilayer structure and followed by rapid thermal annealing such that the implanted ions did not damage the QW structures. The I-V characteristics of the implanted QW are similar to that of the unimplanted. Concerning the TE electro-absorptive modulation, a large contrast ratio of 35dB can be obtained at (lambda) _op equals 1.55 micrometers under a small bias of -1.5V fora 500 micrometers long modulator. For TM mode, a slightly higher CR Of 37dB can be obtained at the operation wavelength although the reverse bias voltage is double.

In-line pairs of InGaAs quantum well waveguide photodiodes are used to function as sensitive wavelength monitors near the absorption band edge of the detector material. These devices displayed an average wavelength sensitivity of 3 pm over a useful operating range of 1535-1570 nm for optical input powers as low as 5 (mu) W. In this paper, we demonstrate the simultaneous monitoring of several wavelengths using an array of in-line detectors and a wavelength demultiplexer. Some methods to improve the performance of the device are examined. By tailoring the lengths of the waveguide sections or by the application of a reverse bias, the individual channels of the array can be optimized for a particular wavelength range. Using a fixed reference wavelength and the quantum confined Stark effect, an effective temperature compensation scheme is proposed. As a demonstration of the technique, a multiplexed Bragg gratin strain senor was constructed. The sensor contained four in- fiber Bragg gratings with a 6 nm center wavelength spacing. Using a broadband wavelength demultiplexer, the photodetector array is used to track the small wavelength shifts induced in the gratings that result from the application of strain. An average strain sensitivity of 6 (mu) (epsilon) was obtained for the four channels.

A novel TM-pass waveguide polarizer, the cladding of which consists of a periodic dielectric multilayer, has been theoretically investigated for the glass integrated optics. The periodic dielectric multilayer exhibits large optical anisotropy and the effective refractive index for the TE polarization becomes higher than that for the TM polarization. Therefore, the highly efficient TM-pass waveguide polarizer can be formed by using the periodic dielectric multilayer whose effective refractive indices satisfy the condition n_TE>n_c>n_TM, where n_c represents the refractive index of the core. As it is difficult to fabricate the thick periodic multilayer by using conventional film deposition systems, we also proposed to overlay the thin periodic dielectric multilayer by using conventional film deposition systems, we also proposed to overlay the thin periodic dielectric multilayer with the fully thick polymer layer, which can easy be formed by using a dipping method. It has been theoretically confirmed that the high extinction ratio is kept while the structural parameters, including the fill fraction for the periodic dielectric multilayer and the refractive index of the polymer layer, satisfy the polarizer condition. As the extinction ratio is high and the structural tolerance is not severe in comparison with other waveguide polarizers, the proposed waveguide polarizer would be useful for the glass integrated optics.

In the characterization of graded-index glass waveguides, use of the standard m-line method by several laboratories has produced increasing discrepancies in the refractive index profile with decreasing film depth. We have addressed this very critical problem by a direct near-surface (DNS) approach, where the polarimetric Abeles-Hacskaylo method was extended as an admittance-matching condition for inhomogeneous films. In this paper, we review the measurement procedures of the same Ag⁺-exchanged waveguides by the DNS approach and by the m-line method, whose result showed significant disagreement at the film-air interface. We search the underlying reasons for this disagreement and test them against non-optical measurements of the ion-concentration profile, to reach a better understanding of the near-surface region, as well as of the distinct probing range of the m-line and DNS techniques.

Ion exchanged devices have been extensively studied at LEMO for twenty years and this work has shown the numerous advantages of this low-cost efficient technology based on the exchange of some alkali ions of a glass substrate with the ones of a molten salt. In this paper, the basics of ion exchange technology is first presented, then the use of various ions couples is discussed in terms of waveguide characteristics and technological trade-offs. The second part of the article is focused on three different application fields of ion exchanged devices which each emphasis a precise advantage of this technology: sensors, astronomy and telecommunication. Concerning the sensors, a low cost integrated displacement sensor is shown, its accuracy is better than 20 nm at a distance of 5 m. In the case of astronomy, results on a two telescopes interferometer recombining head are presented. Because of the large spectral bandwidth of ion exchanged waveguides, fringe contrasts up to 80 percent were measured. As an example of a telecommunication device, narrow emission linewidth integrated DFB lasers realized on rare earth doped substrate are treated. Finally, a presentation is made on some possible evolutions of the ion exchange technology such as hybridization with polymers or ion exchange in thin films.

LiNbO-based optical modulators, used for external laser modulation in 10 Gbit systems, were tested at 40 degrees C 95 percent RH under 10 V, 3 V and 0V bias. Environmental conditions, typical of storage tests, were not too different from their operating level, while 10 V bias was roughly 3 times its standard value. Looking for possible leaking paths between the metal electrodes, the parasitic current I was monitored, with a failure criterion I < 1 mA. Within 2 weeks, some specimens under the highest stress reached the failure condition, and other devices, at the end of the test, showed a degradation of the Insertion Loss IL higher than 0.5 dB. Microscopical inspection showed a common feature, namely the occurrence of Au-rich paths, under the typical form of corrosion between the electrodes. Depending on the extension of those paths, a compete electrical bridge was formed, or simply local plating occurred of the inter- electrode surface, which locally affected the electrical properties of that surface. The observed figures are coherent with Au corrosion mechanisms, which has been relevant in environmental test of RF silicon devices many years ago.

Vapor-phase proton-exchange has been applied to lithium tantalate for the first time, as a waveguide fabrication technique. This technique provides alpha-phase waveguides without the need for annealing. A sealed ampoule set-up has been used employing pure benzoic acid as the vapor source. Various waveguides have been realized and optically characterized by means of standard m-lines spectroscopy. The profile shape is a step plus an exponential tail toward the substrate, as that found for vapor-phase proton-exchange waveguides in lithium niobate. The total depth of the refractive index profile increases with the exchange time, following a linear diffusion model. The ordinary index change has been determined by an interferometric method, giving values that confirmed the alpha-crystallographic phase of the fabricated waveguides. The propagation losses have been measured with a new method using an isosceles coupling prism and an out-coupling objective. The values found for the different modes of the various waveguides ranged from 0.5 to 0.8 dB/cm. An aging phenomenon in the fabricate waveguides has been observed during the first month after the exchange process. The extraordinary index change decreased of 5 percent, while the optical depth increased of 2 percent. Application of this technology to periodically poled substrates for QPM devices seems feasible.

New highly-ordered compositions of nanopolyacetylene (NPA) were recently synthesized. These compositions are highly stable and could be prepared in the form of solutions, films or fibers. Raman scattering in NPA exhibits high intensity of Stokes and anti-Stokes lines; long sequence of overtones and combination bands; extremely low intensity of fluorescence, and passband in the near-IR region. These properties of trans-NPA compositions suggest many important practical applications of this polymer as key photonic material for development of new types of Raman shifters.

The development of a whole family of near and mid-IR quasi- phase matched parametric frequency converters with periodically poled in Ti:(Er:)LiNbO₃ waveguides is reviewed. Due to high quality waveguides with very low losses and excellent homogeneity unprecedented conversion efficiencies have been achieved for second-harmonic generation, difference-frequency generation, optical parametric fluorescence and doubly as well as singly resonant optical parametric oscillation.

We investigate self-pumped phase conjugation (SPPC) generation process and its temporal instability, to demonstrate an all optical control of SPPC output. The optical configuration region at which stable SPPC output is obtainable by effective stimulated photorefractive backscattering-four wave mixing (SPB-FWM) process is limited. Therefore, with non-optimized optical configuration, cat conjugation occurs together with SPB-FWM and then SPPC output becomes temporally unstable. The same is the case with even when the optical configuration is fixed as SPB-FWM interaction length becomes longer. We discus the cause of temporal instability to propose the beam trajectory model when interaction length becomes longer. We discus the usage of temporal instability to propose the beam trajectory model when SPPC output is unstable, based on the experimental result using a new method inducing the control beam whose wavelength is different from the incident beam simultaneously. Moreover, using the method mentioned previously, we demonstrate an all optical control of SPPC output and the generation of temporally stable SPPC output with the optical configuration that SPPC output has been temporally unstable in the conventional methods. Extending the generation region of stable SPPC output will lead to the generation of SPPC from high power lasers in simple system. Moreover, it will also contribute to the realization of all optical image processing and computing, for example, multiple parallel image subtraction and addition.

We present an all-optical cryptographic device for security applications, based on the properties of soliton beams. It is able to codify a given bit stream of optical pulses, inverting at will their order, to make the stream not understandable. Its great advance is represented by its capability of encrypting in real time, without slowing the data flow that can be transmitted with its original velocity.

Second harmonic generation (SHG) in planar nonlinear waveguides is investigated under conditions for which the use of a linear grating fabricate don top of the waveguide reproduces a photonic band-gap structure. The fundamental mode of the guide, at the fundamental frequency, is tuned at the photonic band edge resonance thus experiencing a great confinement and enhancement of the electromagnetic field inside the structure. The linear grating alone is however not able to produce both field confinement and phase- matching of the SHG process. Phase-matching is obtained by an additional modulation of the non linear susceptibility (chi) ⁽²), as in the conventional quasi-phase-matching scheme. The conversion efficiency achieved using both linear and nonlinear gratings is orders of magnitude greater than that of a quasi-phase-matched device of the same length.

Efficient and thermally enhanced frequency upconversion of cw IR radiation at 1.064 micrometers into blue, red and near-IR light in integrated Tm³⁺/Yb³⁺-codoped phosphosilicate silica-on-silicon buried waveguides is reported. Thermally induced frequency upconversion enhancement is observed for the first time in a Tm³⁺/Yb³⁺-codoped system excited off-resonance at 1.064 micrometers . A sevenfold thermally induced upconversion efficiency enhancement was obtained when the waveguide's temperature was varied in the 20 degrees C-120 degrees C range. The thermal effect is believed to be associated with a temperature dependent effective absorption cross-section for the Yb³⁺-sensitizer, which depends upon the phonon occupation number in the host matrix.

We present the results of our systematic research into moderate temperature diffusion technologies of fabrication of optical waveguides in X- and Z-cuts of lithium niobate, i.e. annealed proton exchange (APE) and diffusion doping of erbium from melts containing erbium salts. Our experiments proved, that the X-cuts always contained much more incorporated dopants than the Z-cuts, indicating thus, that the incorporation mechanisms were not the simple ion- exchange ones. The 'layered pattern' of the X-cuts structure makes the vacant cleavage planes easily accessible for penetration of 'foreign' particles into the lithium niobate structure. That may explain much better readiness of the X- cuts to absorb in substantially higher rate the doping ions. The ion exchange diffusion mechanism in the X-cuts is then strongly accompanied by the interstitial diffusion of H⁺. To prove this hypotheses we studied the moderate- temperature diffusion into sapphire that is known to be extremely resistant to diffusion of foreign particles, but structure of that, D_3d⁶, is very similar to the structure of lithium niobate. The doping was achieved by immersing the substrate wafers into reaction melt containing small amounts of erbium nitrate. In the 'X-cuts' sapphire there was found as much as 0.15 at percent of erbium, that is the concentration of erbium one order of magnitude higher than in the other cuts. Thus the possibility of localized doping of Er³⁺ ions into the sapphire single crystal wafers is for the first time demonstrated.

Guided wave optical sensors have had a major impact upon measurement and instrumentation, and are composed of a considerable variety of both active and passive optoelectronic components. In their design and characterization, a wide range of photonic guided-wave devices may be modeled by using several rigorous numerical approaches based on the finite element method (FEM). A review on the applications of one such numerical approach, a combination of the FEM and the least squares boundary residual method is presented. Rigorous analysis a number of photonic devices, which may incorporates several butt- coupled uniform waveguide sections, such as optical modulators, switches, filters, polarizers, power splitters, optical bends, and Bragg gratings, is demonstrated in this paper, as a basis for current and future sensors systems.

Switching and amplifying characteristics of a newly developed 2D InGaAs Active Pixel Imager Array are presented. The sensor array is fabricated from InGaAs material epitaxially deposited on an InP substrate. It consists of an InGaAs photodiode connected to InP depletion-mode junction field effect transistors for low leakage, low power and fast control of circuit signal amplifying, buffering, selection and reset. This monolithically integrated active pixel sensor configuration eliminates the need for hybridization with a silicon multiplexer, and in addition, allows the sensor to be front illuminated, making it sensitive to visible as well as near IR signal radiation. Adapting the existing 1.55 micrometers fiber optical communication technology, this integration will be an ideal system of optoelectronic integration for dual band applications near room temperature, for use in atmospheric gas sensing in space and target identification on earth. In this paper, 4 by 4 test arrays will be described. The effectiveness of switching and amplifying circuits will be discussed in terms of circuit in preparation for 2D InGaAs active pixel sensor arrays for applications in multifunctional, transportable shipboard surveillance, night vision and emission spectroscopy.

A thick, bimodal segment of specific length and height between two single mode sections of a planar waveguide can serve as an integrated optical interferometer. It is realized by etching a wide strip form a guiding film. A vertically guided, laterally unguided beam of light is then made to traverse the strip perpendicularly. For a wide range of materials the structure can be dimensioned such that it shows the proper behavior of an interferometer: depending on the phase gain of the two modes in the thick region, the guided light interferes either almost completely destructively at the transition to the output segment, i.e. the power is radiated away into the substrate and cover regions, or constructively, i.e. most of the power passes the device. We believe that for certain applications structures of this kind can be a simple substitute for instruments like Mach-Zehnder interferometers or directional couplers. This is illustrated by two numerically simulated examples: A polarizer constructed from silicon based waveguides, which offers 30 dB polarization discrimination and 0.1 dB insertion loss with a total length of only 10 micrometers, and a proposal for an integrated magneto optic isolator experiment, where the freedom in the lateral direction can be exploited for a proper tuning of the device.

The design analysis and preliminary testing of a prototype AFOCL is described. The AFOCL is an active optical component composed of solid state lead lanthanum-modified zirconate titanate (PLZT) ferroelectric ceramic with patterned indium tin oxide (ITO) transparent surface electrodes that modulate the refractive index of the PLZT to function as an electro- optic lens. The AFOCL was developed to perform optical re- alignment and wavefront correction to enhance the performance of Ultra-Lightweight Structures and Space Observatories. The AFOCL would be an active optical component within a larger optical system. Information from a wavefront sensor would be processed to provide input to the AFOCL to drive the sense4d wavefront tot he desired shape and location. While offering variable and rapid focusing capability similar to liquid crystal based spatial light modulators, the AFOCL offers some potential advantages because it is a solid-stat, stationary, low-mass, rugged, and thin optical element that can produce wavefront quality comparable to the solid refractive lens it replaces. The AFOCL acts as a positive or negative lens by producing a parabolic phase-shift in the PLZT material through the application of a controlled voltage potential across the ITO electrodes. To demonstrate the technology, a 4 mm diameter lens was fabricated to produce 5-waves of optical power operating at 2.051 micrometers wavelength. Optical metrology was performed on the device to measure focal length, optical quality, and efficiency for a variety of test configurations. Preliminary data was analyzed and compared to idealized performance available from computer-based models of the AFOCL.

In this paper, a detailed design and simulation of a Mach- Zehnder-type interferometric lumped modulator is presented. From the curves of relative phase shift between the two modulator arms it is possible to derive information on a set of unknown voltages, when compared with a user-controlled reference voltage, for data classification and identification purposes.

The potential of integrated optical micro cavities (MC) for use in enhanced optical spectroscopy has been studied. The MC devices can sustain high morphological enhancement of optical field due to excitation of high-Q whispering gallery modes. The evanescent near field of the MC can be used to excite spectroscopic signal of molecules pout on top of the MC. Estimation shows that both local excitation field and emitted field can be increased y 2-3 orders of magnitude in the MC on resonance. In total, a gain of 4-8 orders of magnitude in the Raman/fluorescent signal of a molecule near the MC can be expected. In addition, the MC delivers a tunable and measurable enhancement, which is a real benefit in terms of enhanced optical microspectroscopy on-chip. High-Finesse integrated optics cylindrical micro cavities capable of significant field enhancement have been fabricated. Use of various waveguide/MC coupling schemes and design parameters allowed optimization of the devices for the largest intra-cavity power. The result for different micro cavities show prominent enhancement of intra-cavity field correlating with its mode spectrum. The characterization of MC and measurements performed demonstrate feasibility of the MC-based device for optical spectroscopy.

We demonstrate light propagation in a novel type of optical waveguide, which consisting of periodically arrayed dielectric particles. Advantages provided by this waveguide are that dynamic optical interconnection can be realized and that a multichannel waveguide is easily formed. To fabricate the system of periodic micro cavities, we used polystyrene- latex particles that have a uniform size of 15.6 micrometers . The second harmonic of a Nd:YVO₄ laser, the wavelength 532 nm, was introduced to the sample substrate in order to excite the fluorescence of Rhodamine 6G. Some discrete frequencies of fluorescence were selected to agree with the phase matching condition and produce a resonance mode in a microsphere. Part of the energy transferred to the adjacent spheres via evanescent light. Thus, some discrete frequencies of the fluorescence propagated through the microspheres. Since the particles are arrayed symmetrically, the resonance light can propagate in three different directions. The propagating direction can be controlled to regulate the location of a focused spot. In addition, if you illuminate the next microsphere, the excited light propagates in the next line of arrayed microspheres. The assembled microspheres can be taken as a multichannel waveguide.

Optical number representations (NRs) beyond the common binary radix-2 concept and based on multiple-valued logic (MVL) and redundant NRs (RNRs) are presently restricted to optical free-space techniques. The present paper is an attempt to apply these concepts to lightwave circuits (LWCs). Starting with planar waveguide (WG) devices, capable to provide logic, their extension to 3D and large coupler size is assumed. The attempt to RNR by Wgs is based on two tuning parameters (i) the geometry N >= 3 of the optical architectures and (ii) the degree of repetitive triangularization where (ii) determine the increase of the parallelism dependent on (i). This parallelism is applied for RNR and (i) and (ii) determine (1) the number of couplers (2) the number of additional interconnections and (3) the distribution of the additional interconnections at the couplers. The proposed concept includes the common binary radix-2 logic and the higher radix WG logic is by the organization of the cores of the couplers. The reason for establishing RNR by LWCs is its necessary for minor depth optical WG logic. The large sized couplers, arising y repetitive triangularization, are aimed to be implemented by fibers and the logic circuits by active fiber bundles but the goal of the ongoing work is the photonic integration of the architectures.

We have succeeded in making a compact holographic memory system, by using one-beam geometry, which eliminates the process to divide incident beam into objective and reference beam, and by using laser diode as the compact light source. Laser diode can be used since the one-beam geometry avoids the beam to be divided into tow and the power to be decreased. As the recording media, photorefractive crystal is used. The experimental results of recording and readout of some images are described, and the ability of the system is discuss.

In this paper we demonstrate for the first time to our knowledge that the LiNbO₃:Fe crystal has the dynamic behavior of transition from self-defocusing to self-focusing under certain experiment conditions. It represents that, after a period of illumination, the peak intensity transmission increases and the FWHM becomes narrower gradually. By comparing the experiment result under different conditions, we believe that his kind of transition exists universally in LiNbO₃:Fe crystal. We think that its mechanism is based on the following. At the beginning of illumination, due to the Gaussian distribution of the incident intensity, photorefractive effect forms a negative lens in illumination area, making the light beam widened and diverged. While when the change of the refractive index reaches saturation, the negative lens effect disappears. A double phase conjugate Fabry-Perot interference cavity is formed between the input plane and output plane of the crystal. The multiple-beam interference causes the output beam brighter and thinner.

We propose and demonstrate a new method to fabricate volume phase mask in LiNbO₃:Fe crystal by photorefractive effect, for the first time to our knowledge. First, we image an amplitude mask with corresponding intensity distribution at the incident face of a photorefractive LiNbO₃:Fe crystal. After an exposure of proper time, due to photorefractive effect, the distribution of refractive index in the crystal is changed. Therefore we get the volume phase mask we want. The influence of the anisotropy of photorefractive nonlinearity on volume phase mask can be overcome by controlling experimental conditions. We can see an intensity-modulation image in the image plane of the volume phase mask. The intensity distribution of the image of the volume phase mask is inverse from the one of input amplitude mask. It can be explained by waveguide theory. Volume phase mask can be used to get modulated amplitude pattern by modulating the phase of incident light. It has the advantage of low energy loss over amplitude mask and real-time. Our method is very simple. It can be used to fabricate many kinds of complex phase masks and phase components used in optical information processing and Integrated Optics.

The feasibility of an integrated optical memory is explored. This memory cell is based on the plasma wave modulator/switch, which has a horizontal layered structure. A transverse voltage maintains a bias for the structure and can be used for electrical write cycle. The cell content is then read by a propagating guided optical wave across the structure. It is also possible to apply full optical read/write/clear cycles as discussed. The read cycle can be either destructive or non-destructive, depending on the wavelength. A modification of this device may be considered as an opto-transistor, in which an optical signal controls the flow of another optical beam.

In this paper the possibility of using ferroelectric liquid crystals in active waveguide devices is explored through the analysis of an integrated electro-optic switch and a continuously tunable filter. The design and the analysis of tow electro-optical devices, based on a Bragg grating integrated in a glass waveguide having liquid crystal as cover, are presented. The integrated optics structure allows to change the reflectivity of the Bragg mirror by means of electro-optic effects of smectic liquid crystals. The integrated fast electro-optic switch is based on electro- optic properties of smectic C^* in the Surface Stabilized liquid crystal structure and on the selective properties of integrated Bragg grating. It presents the output directly in the frequency domain, overcoming the typical problems of intensity dependent devices, without requiring external electronic circuit. Moreover the possibility to realize a novel continuously tunable integrated filter, combining the linear electro-optic effect of smectic A^* and the selective property of Bragg grating, has been explored. The proposed filter is characterized by a narrow bandwidth, desired feature for WDM technique. The principal advantages of such device include fast tuning speed, wide tuning range, low power consumption and low cost.

A novel configuration for an optoelectronic integrated router based on a waveguide with a liquid crystal over- layer, working at the wavelength of 1.55 micron, is theoretically discussed for the first time. The device is based on the mode-mixing principle together with the electro-optic effect of a smectic A^* liquid crystal. The device is composed by a single mode input optical channel waveguide, a bimodal active region, with a liquid crystal over-layer as cover, and an output Y branch to separate the two output channels. The active region is designed to allow a (pi) shift between the two modes that it supports, by means the variation of the effective refractive index of guided modes due to molecular reorientation of liquid crystals indued by an electrical field. By doing so it is possible to steer light from one output channel to the other one. Exhaustive detail about the design both of the input waveguide and of the active region has been given together with the description of the optical behavior of our device. Numerical simulations have shown how this kind of router exhibits satisfactory performances.

A new methodology of the propagation loss coefficient measurement with an accuracy of at least 10^-3 cm^-1 is demonstrated using a single-pass transmission measurement method and beam coupling based on self-pumped conjugation process in BaTiO₃ single crystal. A new, high-precision optical 'bridge system' for routine measurement of planar waveguide propagation los coefficient is designed.

The Y-branch waveguide is one of the basic components of optical circuits in the network and computer devices. Considering the high-density integration of optical circuits, a wide angle Y-branch waveguide, which is a small waveguide, is highly desired. Authors had been prosed a new Y-branch waveguide with reflecting surface to achieve low- los and wide branch angel> Also we had shown the successful results of low-loss characteristics and the large tolerance to the fabrication error by numerical analyses. In this paper, we evaluate the loss characteristic and the stability of branching ratio of proposed Y-branch optical waveguide with reflecting surface from experimental results. The proposed model is fabricated by UV-curing method and PMMA resin because of its transparency and ease of fabrication. In these experiments, successful results, such as low-loss, wide-angle abilities and availability of variable branching ratio were obtained. In all experiment and numerical analyses, we assume that the multi-mode waveguide is used in optical circuits considering the optimum connections to the VCSEL.

Machining technology for LiNbO₃ (LN) wafer surface aiming a mass-production of broadband LN modulators is investigated. Although several manufacturers commercially supply 40G LN modulators, there are many difficulties in mass-production of such broadband LN modulators. For instance, in order to realize sufficiently broadened bandwidth performance, machining of LN wafer surfaces is necessary as demonstrated by ridge-waveguide modulators and devices using very-thin substrates. We focus the study on the machining technology of LN wafers applicable to mass- production based on micro-sandblast techniques. In order to demonstrate effectiveness of the micro-sandblast, 40G LN modulators designed to have a partially thinned substrate along RF-electrodes are experimentally fabricated.

The aims of our work is to project and to test a material and technological solution of a preparation of planar and channel optical waveguides in substrates made of special glasses using Li⁺ $ARLR Na⁺ ion exchange. This method should ensure to these waveguides wide parameter variability and low losses. We paid special attention to relations between technologic parameters and final waveguide properties.

We have studied fabrication and properties of copper ion- exchanged waveguides fabricated in various types of special soda-lime silicate glass as well as commercial optical glass substrates. The ion exchange was performed in melts containing either Cu^I or Cu^II at temperatures from 350 degrees C to 500 degrees C for times ranging from 5 minutes to 21 hrs. Optical properties of the fabricated waveguides were studied using mode spectroscopy and photoluminescence spectroscopy and composition of the waveguides was determined by SEM, RBS, EPR and ESCA. After the ion exchange the refractive index increased, according to fabrication conditions, up to (Delta) n equals +0.0693 and the guides supported up to 16 TE and TM modes. The Cu^I $ARLR Cu^II redox reaction during the fabrication depended strongly on the composition as well as the temperature of the reaction melts. In the Cu₂Cl₂ZnCl₂ melts the oxidation of Cu^I to Cu^II was strongly hampered, so that Cu^I prevailed in the waveguiding region. These samples exhibited the most intensive blue-green luminescence, in spite of those fabricated using the Cu^II-based reaction melts, where practically no blue-green luminescence was observed. ESCA measurement revealed an easy charge transfer between the both oxidation states of copper in the very surface regions of the samples.

The polyimide technology has bene used extensively for semiconductor industry, includes buffer coating, interlayer dielectric and passivation, Alpha ray shielding and protective/insulating films. The features of the polyimide material for the new generation of advanced semiconductor products must have excellent properties and high performances to meet various demands in the microelectronics application. The requirements include high resolution, low internal stress, process cost reduction, environment safety, excellent process stability and window in the future. Three kinds of heat-resistant base polymers had been widely applied on wafer-coating processing microelectronic device including polyamic acids, ring-closure type soluble polyimides with hydroxyl groups, and PBO precursors. In this work, we had evaluated positive-tone photosensitivity with aqueous developed polyimide consisting of previous base resins, and compared the difference of process conditions, cured-film properties, adhesion properties, etching recipes as one mask process and reliability test, etc.

The influence of sodium ions on rare-earth clustering formation was analyzed in xSiO₂-(1-x)P₂O₅-zNa₂O glass matrices observing variations in the erbium lifetime laser tradition at 1535 nm. The ER³⁺ equals 1.0M glasses have shown an optimal performance for sodium close to 0.5M. Using the fluorescence characteristics an enhancement of approximately 25 percent in the lifetime was observed. It was noticed that the Na⁺ ions have not contributed only to the clustering formation but also to the rare-earth concentrating, due to the augment in the non- bridging oxygen in the glass. The Judd-Ofelt analysis was applied to the glass system and softening due to the inclusion of sodium into the matrix was observed. All these results are in agreement with the molecular dynamics analysis reported for similar glass.

We have realized 1 cm long DFB lasers integrated on an Er- Yb-doped phosphate glass substrate with the use of Ion Exchange technology. The grating has been written in a photoresist layer with an interferometric exposure setup and transferred on the glass top surface with a Reactive Ion Etching. The lasers emit in a single longitudinal mode at 1.5418 micrometers with a pump power threshold of 27 mW, and a slope efficiency of 1.6 percent.

Superluminescent light sources can be used in many fields, such as fiber optics gyroscope, optical time domain reflector, wavelength division multiplexing system, in which superluminescent power is very important factor. In order to increase the power, we integrated the SLD and SOA monolithically. Meanwhile, the axis of integrated device was tilted with respect to the facet normal. High power 1.5 micrometers superluminescent light source has been fabricated by optimizing the structure of integrated device. More than 200mW was obtained at lower pumping level by cooperation of the two sections. The spectral FWHM is 26nm.

In this paper an experimental study of thermo-optical properties of polymer dispersed liquid crystals (PDLC), prepared by PIPS in bulk and in confined cylindrical geometry, is presented. The transmissivity of PDLC In bulk as a function of temperature proves the existence of temperature optical switching. We have also demonstrated the existence of optical bistability, which could be interesting in develop of logical optical devices as optical memory elements. A bistable al fiber optic sensors based on PDLC is also presented. In this device PDLC permits at the same time the optomechanical interconnection of tow fibers and the modulation of the light crossing the device. As the modulation can be controlled by external temperature, the device has been proved to be suitable for the realization of a heat flow sensor. Without any optimization of the device we have obtained an ON-OFF contrast of 8 dB and a response time comparable with other conventional device using nematic LCs. This sensor is compact, rugged and is cheap, because it does not require a complex fabrication and alignment technology. It presents the typical advantages of both the fiber optic sensor and the liquid crystal technology. We note that its main advantage is a small thermal capacity, which is comparable with electronic device as thermistors, and it represents a significant improvement for the sensor based on liquid crystals. Further theoretical studies are necessary in order to understand in depth it thermo-optical characteristics.

A silicon-based integrated optical pressure sensor using an intermodal interference between the fundamental TM-like and TE-like modes is described. The sensor consists of a micromachiend rectangular diaphragm and a straight polystyrene optical waveguide passing across the diaphragm. The use of the intermodal interference has the potential advantage of shortening the sensor length since it needs neither a Y-branch nor a 3-dB coupler. In the presence of the pressure difference on the diaphragm, the phase difference is yielded between the two guided modes by an anisotropic index change induced by the elasto-optic effect. The phase difference is finally transformed into a change in light intensity by an analyzing polarizer. We fabricated a sensor with a 1.2 mm by 10 mm by 20 micrometers diaphragm over which the waveguides were formed at 50 micrometers intervals. In the experiment, a linearly-polarized He-Ne laser beam at 633 nm was coupled to the two guided modes at equal intensity. The output intensity through a polarizer was sinusoidally changed at a period of 64 kPa, corresponding to a phase sensitivity of 98 mrad/lPa, for the waveguide nearest to the diaphragm edge. The measurement was carried out for other waveguide positions. The largest sensitivity was obtained for the waveguide nearest to the diaphragm edge as theoretically expected.

Zone plate is a type of important element widely used in modern optical instrumentation. In this paper we propose and realize a new method to fabricate phase zone pate in LiNbO₃:Fe crystal. After the photo-excitation, migration and retrap of free charges in LiNbO₃:Fe crystal, an axially symmetrical variation of refractive index is recorded in the crystal, an axially symmetrical variation of refractive index is recorded in the crystal. By this way, we get a phase zone plate. We can adjust the focal length of the phase zone plate by changing the imaging condition of the Fresnel zone plate, which will cause the variation of the radii of image of the zone plate in the crystal in our experiment, we use Fresnel zone plates we get can reach to as high as 21 percent. The phase zone plate can have long life-time after thermally fixed. Our method is very simple and can be widely used in optical information process and integrated optics.

In this paper, a new integrated programmable diffractive optical element is described, which i8s composed by stacking of the plasma wave optical modulator/switch structure. This structure has the possibility of high density integration by means of the state-of-the-art fabrication technologies. The device has the in-design capability to be either programmed electrically or optically. Both the optical and electrical programming require transverse Dc biases across the waveguide modulators. Programming time in both approaches could be as low as 10ps. As proposed in the paper, the device has numerous applications in different areas including decision making, pattern recognition, high density optical shortages, programmable gratings and holograms, and optical computing.

In recent years, the demand for the high efficiency diffractive optical element is booming for large capacity storage devices. Instead of conventional lithographic approach to fabricate molds, we have developed a new technology utilizing an electron beam writer in order to produce molds used for injection modeling high-accuracy diffractive optical elements. Although we have already developed a technology to produce plastic diffractive elements, with the new technology we can produce blazed and relief features, which are not achievable through the conventional approach. By introducing a mathematical expression to give exact dosage necessary for particular depth from 0.7 to 1.3 micron ad from 1.5 to 5.0 microns pitch, high-accuracy nano-3D features can be controlled within +/- 50 nm in pitch and +/- 35 nm in depth. This blazed structure was designed to achieve 41 percent identical 0th and first order and the result is 39.0 percent for 0th and 37.9 percent for first order at 780 nm.

An add/drop filter with a two-moded section is demonstrated using buried ion-exchanged waveguides and a photowritten Bragg grating. The device exhibits a 20 dB extinction ratio and a 3 dB bandwidth of 0.4 nm.

AsSeTe/AsSe chalcogenide glasses are photosensitive materials with large refractive index. These properties make these glasses suitable for the fabrication of photonic crystals, waveguide components and MOEMS. We present in this article fabrication of 3D photonic crystals, composed from AsSeTe and air, with sub-micron feature size. The method of fabrication is relatively simple and cheap using only vapor deposition and optical holographic lithography. The interferometric alignment allows to eliminate requirement for a mask aligner.