The importance of LiNbO₃ proton exchanged (PE) waveguides in integrated optics is well consolidated. In such waveguides, only extraordinary modes are supported, since the ordinary refractive index is decreased by proton exchange. However, the knowledge of the ordinary refractive index profile is of great importance, being related to the crystallographic phase of the exchanged layer. This work provides a wavelength dispersion curve for both ordinary and extraordinary index changes of PE-LiNbO₃ waveguides. The dispersion curve of the ordinary index change was obtained by means of a non-conventional method, developed in our laboratory, based on radiation modes, that of the extraordinary index change by standard m-lines spectroscopy. A multimode PE waveguide was designed and fabricated specifically to obtain a very accurate determination of the index changes up to the 1.55μm spectral range. The waveguide was realized on a Z-cut LiNbO3 substrate, by a 26h proton-exchange at 247°C in benzoic acid diluted with 1% lithium benzoate, resulting in a depth of 2.75μm. The measurement of both index changes was performed at wavelengths ranging from the visible to the near infrared and the corresponding Sellmeier curves were obtained. It is worth noting that the two index changes exhibit a significantly different behaviour.

Direct near-surface (DNS) and m-line techniques for the measurement of surface refractive index of ion-exchanged waveguides are compared. Measurements are also compared to direct investigation of ion concentration profiles by energy dispersion spectroscopy (EDS). Good agreement is obtained for the Ag⁺, K⁺, and Ag⁺+K⁺ exchanged samples, but not for the K⁺+Ag⁺ sample. The index profile approximately follows in a linear proportion the concentration profile after a single Ag⁺-exchange, while this is not observed for all other samples involving K⁺-exchange. These results on ion-exchange and refractive-index profiles are discussed, towards a comprehensive and accurate characterization of graded-index waveguides.

Key optical elements for space qualification plans of photonic devices are overviewed. Device parameters and qualifying procedures were discussed to assure the reliability of newly developed photonic devices needed for potential usage in space environments. The goal is to gradually establish enough data to develop a space qualification guideline for devices using empirical and numerical models to assess reliability including the lifetime degradation of devices for long-term space applications. Optical, electrical and mechanical device requirements of newly integrated photonic devices (diode lasers and detector arrays) were presented. Monolithically integrated active pixel InGaAs detector arrays were compared, as examples, with those hybridized with CMOS silicon multiplexers in terms of their performances and reliability. Adapting the existing fiber optical (1.55 μm) communication technology, this integration will be an ideal optoelectronic system for dual band (0.5-2.5 μm, Visible/IR) applications near room temperature for use in geological material research and in atmospheric gas sensing in space. For target identification on earth, however, there are concerns about the effectiveness of the device quality, reliability, and prevention of device failure in preparation for multifunctional, transportable shipboard surveillance, night vision, and emission spectroscopy in air and on Mars terrestrial applications.

We numerically demonstrate that the classical thin film computation method (Abeles Computation Method) may be used to obtain reflectance or transmittance of integrated optics filters with a good approximation. Radiative losses are simulated by absorption losses. Results agree well with Film Mode Matching computed optical properties and the computation time can be divided by a factor of 10⁴. Synthesis of integrated Bragg reflectors, narrow band pass filters, high pass filters is presented. Integrated optics filters with non-periodic structures such as gain flattening filters can be easily designed using the Abeles Computation Method. Thus, classical thin film synthesis softwares are useful to design integrated components with arbitrary guided mode spectral reflectance or transmittance. This leads to prospects of new integrated optics functionalities of a great importance such as broadband dispersion compensation for WDM systems or high - order dispersion compensation with non linearly chirped integrated Bragg reflectors.

Hybrid glass parts composed of dissimilar glass sections are an attractive route to integrate multiple functions onto a single substrate and offer the potential to fabricate advanced laser sources, amplifiers, lossless splitters and other photonic devices such as Fabry-Perot etalons. We review the most promising bonding technologies, placing particular emphasis on techniques that do not require the use of high processing temperatures. In particular, we discuss in detail a recently developed low temperature bonding technology that relies on inorganic adhesives. Characterization of interfacial joints prepared with this inorganic technology indicate low insertion loss, high mechanical strength and chemical resistance to attack during the conventional lithographic and ion exchange steps employed to fabricate waveguide structures.

Lithographic patterning of organic-inorganic hybrid materials processed by the use of sol-gel technology allows for the generation of waveguide structures at low temperatures onto polymer or ceramic substrates. In addition, sol-gel technology provides the possibility to process precision structures, such as, grooves and cavities, which are applicable for the passive alignment of photonic devices. This provides the possibility for the realization of mass-producible photonic circuits onto large-area substrates. At the moment, the most potential applications are systems based on then use of multimode waveguide structures. Actually, when utilizing sol-gel technology, the challenge is how to process homogenous, low-loss and high-aspect-ratio structures. In addition, when aiming to highly mass-producible multimode modules, the key issue is the alignment of photonic devices preferably by the use of passive precision structures. In the future, when the systems need to be more complicated, the modeling of systems requires sophisticated 3D modeling tools. In this paper, the processing of multimode structures with sol-gel technologies is described, and the characterization results of prototype devices are reported. In addition, molding and cofiring technologies potentially applicable for the hybrid integration of photonic modules are reviewed. Finally, the future research aims for the commercialization of photonic modules based on the use of sol-gel technologies are envisioned.

Sharp bends in low index contrast waveguides using tapered air trenches are proposed. To minimize cladding-trench junction loss, cladding tapers are designed to provide adiabatic mode shaping between low and high index contrast regions. Drastic reduction in effective bend radius is predicted. We present 2D FDTD/EIM simulations of bends in representative silica index contrasts. Substrate loss in air trenches of finite depth is investigated, and the required trench depth, given an acceptable substrate loss, is calculated. Fabrication steps are described.

Optical component coupling using self-written waveguides is one of the promising methods to improve the existing alignment control difficulties in optical component coupling. Using conventional UV curable resin as a waveguide material, waveguide spontaneously forms by UV light exposure from an edge of an optical fiber. When UV light is exposed from two faced optical fiber edges, self-written waveguide forms between them and connect the two optical fibers with decreasing its coupling loss between them. The effectiveness of this unique method is systematically studied on multi-mode fiber coupling; single mode fiber coupling can also be attained. The observed coupling loss after waveguide formation is significantly lower than that before the waveguide formation. Coupling of multi-mode fibers with not only gap but also some offset was also studied; the input light is actually bending and guiding along the formed self-written waveguide between two multi-mode fibers. Using this easy, quick and convenient coupling method, severe alignment control would not be required in a optical component coupling procedure and significant cost reduction could be expected.

During the last decade, there has been rapid progress in the development of integrated optical circuits, incorporating thin optical waveguides, for the Visible and Near IR (NIR) spectral ranges. In this work we extended the same concept to the Mid-IR (MIR) spectral range 3-30 microns. Towards this goal we developed diffused and strip buried planar waveguides based on silver halide crystals. Diffused planar waveguides were created by diffusion of Br^- ions into crystalline substrates, forming silver chloro-bromide (AgClBr) layers of higher refractive indices and different thickness of 65μm to 600μm. Strip buried planar waveguides were constructed from press-flattened silver chloro-bromide (AgClBr) fibers with different thickness, which were buried into an almost pure substrate. All the waveguides were in a thickness range of 60μm to 170μm. Using CO₂ laser we found that the transmission losses at 10.6mm were about 4 to 12dB/cm for the buried waveguides and about 4 to 16dB/cm for the diffused waveguides. We also formed and characterized curved waveguides on AgCl substrate. By using the planar waveguides as sensing elements for infrared evanescent wave spectroscopy, we were able to detect 1% of glucose or 1% of alcohol in water. In conclusion, we demonstrate the feasibility of using AgClBr waveguides as integrated optical elements in the MIR.

The future of telecom system design relies heavily on combining many optical devices into multifunctional modules with superior performance, lower cost, and smaller overall package size. The AWG module developments discussed here will afford comprehensive benefits to advanced optical networks. Current AWG development efforts focus on lowering insertion loss, reducing crosstalk, increasing channel bandwidth, decreasing channel spacing, managing dispersion, decreasing package size, and incorporating intelligent electronics. Better matching of the waveguide geometry and index of the integrated circuit to the optical fiber reduces the coupling loss. Other design optimizations to the waveguide bend radius and waveguide pitch at the slab can decrease circuit loss. High quality processing reduces the inhomogenieties that cause phase errors in AWGs and thus increase channel crosstalk. Optical design modifications in AWG waveguide tapers at the slab can change the passband shape and increase the channel bandwidth. Dispersion can be managed by better controlling the dispersion slope allowing for compensation. Innovations for temperature control circuitry and novel packaging designs and materials allow for smaller modules and reduced power consumption.

Arrayed Waveguide Gratings (AWGs) are key components in current and future optical network realizations. In order to prevent the need of accurate wavelength control the transfer function of the AWG should ideally have a rectangular shape. Several techniques have been proposed in order to flatten the Gaussian-like transfer function of the conventional AWG. In this paper we propose a new technique is based on the modification of the arrayed waveguide lengths and their positions on the Free Propagation Regions. The above technique is similar to the deterministic tapering technique used in the design of antenna arrays, since the spatial transfer function of the latter has the same characteristics as the spectral transfer function of an AWG. Therefore, problem is reduced to that of matching the integral of a sinc function with a discrete step function and the optimal waveguide lengths are obtained by solving a set of equations numerically. The performance of this technique (in terms of transfer function flatness, sidelobe level and insertion losses compared to a conventional AWG) depends on the values given to several initial design parameters related to the AWG geometry. The results obtained show that it is feasible to fabricate AWGs with rectangular transfer function with proper adjustment of certain structural parameters.

With the increase of optical communications bit rate, the interest for broad-band integrated optic Wavelength Demultiplexers Multiplexers (WDM) devices is growing. Their applications include, for example, the fiber communications on a single fiber by adding the transmission capacity of both optical telecommunication windows at the wavelengths 1.31μm and 1.55μm. They also achieve to combine pump and signal wavelengths in rare earth doped integrated optical amplifiers and lasers. A promising technology to realize those devices is ion-exchange on glass which allows the integration of different functions in a glass substrate with efficient results and an excellent compatibility with fiber systems. In this paper, an original design of a broad-band duplexer is presented. The principle of the device is first explained. Then numerical and experimental results confirming good performances are shown. Instead of using phase-matched coupling as it is usually done, we propose a structure based on distributed coupling. This particularity entails a low sensitivity to technological parameters and a broad-band behavior. As a validation, a test device has been realized by ion-exchange on glass.

Photonic space switches are useful elements in optical fibre communication links. This paper describes the design of 2Nx2N photonic switches based on the generalized Mach-Zehnder interferometer. Although these switches are limited in dimension, they have the desirable attributes of low loss, good loss uniformity, small size, robustness and ease of fabrication and integration.

In our work we have fabricated Bragg grating structures in silicon-on-insulator (SOI) waveguides. SOI waveguides enable integration of both passive and active functions, e.g. thermal, electrical or micromechanical tuning and optical receiving with the gratings. As silicon is a high refractive index material the first order grating period at 1550 nm wavelength is short, only 225 nm, and this period must be precisely controlled. Moreover, the grating must be spatially coherent over its entire length. All this introduces a great challenge for the fabrication techniques used to pattern the grating. Our approach to process gratings in SOI waveguides is based on direct e-beam writing and silicon etching with inductively coupled plasma (ICP). We show results on high aspect ratio Bragg gratings integrated with SOI waveguides with large core size.

Ferroelectric materials, e.g. lithium niobate (LN), are widely used for the realization of second-order nonlinear (SON) optical devices, including electro-optic (EO) modulators and switches, frequency converters and all-optical switches based on cascading effects. Glass is a centrosymmetric material and does not show any macroscopic SON properties. However, by appropriate poling techniques significant SON values can be induced, e.g. in silica and silica fibres/waveguides. In fact efficient EO modulation, quasi-phase-matched second-harmonic conversion efficiencies exceeding 20% and parametric fluorescence have been demonstrated in poled silica fibres. Compared to ferroelectric waveguides, poled silica fibres/waveguides, despite having a lower SON, offer longer interaction length for the same bandwidth (due to a lower dispersion), higher damage intensity threshold, lower loss and refractive index, thus keeping high values for the EO and frequency conversion efficiency figure of merits. We will review recent progress on those SON materials, highlighting their advantages and disadvantages.

Refractive index changes have been induced inside bulk fused silica by using femtosecond (fs) laser pulses tightly focused inside the material. Waveguides have been fabricated inside the glass by scanning the glass with respect to the focal point of the laser beam. The refractive index change is estimated to be ~ 10^-4. Other more complex three-dimensional structures have also been fabricated (curved waveguides, splitters, and interferometers). We also report on fluorescence spectroscopy of the fs-modified fused silica using a confocal microscopy setup. Using a 488 nm excitation source, a fluorescence at 630 nm is observed from the modified glass, which is attributed to the presence of non-bridging oxygen hole center (NBOHC) defects created by the fs pulses. The fluorescence decays with prolonged exposure to the 488 nm light, indicating that the defects are being photobleached by the excitation light.

Tin-doped silica glass has been recently investigated as photosensitive optical material for optoelectronic device applications. The mechanisms responsible for the material photosensitivity and the optical activity induced by Sn doping are presented. Studies performed on perform slides and on sol-gel bulk samples show that the refractive index change can be ascribed to structural rearrangements induced by photochemical reactions. Photoluminescence measurements indicate that tin atoms are embedded in Sn-substituted Si sites of the silica network. The modified structure shows extremely high stability, and gratings written in fibers exhibit a negligible erasure in 30 minutes below 600 °C. At high UV radiation fluences the refractive index modulation saturates and does not exhibit any decrease. Optical measurements and electron paramagnetic resonance data show that different processes contribute to the refractive index change. The comparison between samples with and without optical absorption at the UV laser wavelength shows that the presence and the consequent laser-induced bleaching of the 5 eV absorption band due to oxygen deficient centers does not appear crucial for photosensitivity. In fact a refractive index change is also observed in samples without detectable absorption at this energy.

We have fabricated silica-based waveguide Bragg grating devices and have investigated temperature sensitivity of the Bragg wavelengths. Temperature sensitivity of Bragg wavelength is caused by temperature dependence of effective refractive index and thermal expansion. We examined boron-codoped germanosilicate glasses as waveguide materials in order to decrease a temperature sensitivity of refractive index. The boron-codoped germanosilicate films were fabricated by a plasma enhanced chemical vapor deposition. We adopted Si, silica, and crystallized glass as substrates in order to control the thermal expansion of the waveguides. Bragg grating with 0.53 μm period was formed by irradiation with a KrF excimer laser light through a phase mask. The Bragg wavelength shift of 9.7pm/°C was obtained in the B-Ge-SiO₂ core waveguide on a silica substrate, while the Bragg wavelength shift was 11pm/°C in the with Ge-SiO₂ core waveguide on a Si substrate, which was a conventional-type waveguide Bragg grating device. The Bragg wavelength shift was reduced to 7.8pm/°C by using B-Ge-SiO₂ core and a crystallized glass substrate with zero thermal expansion coefficient, which was 2/3 of the value of the conventional waveguide Bragg grating device.

The energetic 7.9-eV photons of the F₂ laser directly access bandgap states in germanosilicate glasses to provide a strong and direct channel for inducing refractive index changes in optical fibers and planar waveguides. In this paper, we review our F₂-laser photosensitivity studies with an aim to assess prospects for shaping useful photonics structures directly inside the germanosilicate waveguides. We describe strong photosensitivity responses in standard telecommunication fibers and planar optical waveguides without the need for hydrogen loading, and compare with responses provided by traditional ultraviolet lasers. Because of the strong 157-nm absorption in the germanium-doped guiding layers, large non-uniform changes to refractive index are noted that offer opportunities for trimming phase errors and correcting waveguide birefringence in planar optical circuits. With hydrogen soaking, modest 157-nm pre-irradiation was found to 'lock-in' a permanent photosensitivity enhancement in the germanosilicate guiding core, permitting the formation of strong (40-dB) and stable fiber Bragg gratings with 248-nm KrF laser light. The 157-nm 'lock-in' mechanism is associated with Si-OH and Ge-OH defect formation and permanently enhances the ultraviolet photosensitivity response by several orders of magnitude above that for an untreated fiber without the aging related disadvantages of conventional hydrogen soaking. The unique opportunities for F₂-laser photosensitivity applications in shaping and trimming photonic components will be outlined in this presentation.

Second order optical nonlinearities were induced in commercial phosphate glasses (Schott, IOG-1) by the thermal poling technique. The induced χ⁽²⁾ was measured via second harmonic generation using a fundamental beam from a 1064 nm mode-locked Nd:YAG laser. The nonlinear regions were characterized using the Maker-Fringe technique, in which the second harmonic signals were observed as a function of incident angle of the fundamental beam. The results show that the χ⁽²⁾ profile has contributions from two distinct regions: a near-anodic surface region and a bulk. We have modeled the induced profile to fit our experimental results. The dependence of the induced nonlinearity on applied poling fields, temperatures and poling time is discussed.

An all-optical cryptographic device for security applications, based on the properties of soliton beams, is presented. It is able to codify a given bit stream of optical pulses, changing their phase and their amplitude as a function of one or more encryption serial keys that merge with the data stream, generating an incomprehensible stream. 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.

We numerically investigate nonlinear pulse propagation in finite, 1-d photonic crystals, and highlight novel properties that may help pave the way to a new class of high-efficiency nano-devices. We show that phase matching conditions for multiple wavelength generation and interactions can be achieved by judiciously combining material's index dispersions and geometrical features. We also show that enhanced nonlinear interactions can occur with efficiencies three orders of magnitude larger with respect to bulk materials having the same lengths and nonlinearity. Finally, we suggest potential applications as miniaturized second and third harmonic generators, nonlinear mirrors, parametric amplifiers, and optical switchers.

Thanks to progresses in photolithography techniques optical materials can now be structured to a scale of a few tens of a nanometer. This has opened a wide field of new applications. When concerned with a scale of some tens of a micron down to a few microns, microlens and integrated optic components can be made. When the material is structured with a scale in the order of the wavelength of light, different filtering functions can be made. This concerns Bragg mirrors or more generally Photonic Crystals. A structuration in a scale small in front of the wavelength is also of a great interest. In this case the material does not diffract the light anymore an dit behaves like a homogeneous one. The calculated transmittance of a laser mirror is used to determine the effective index of the single layer equivalent to the multilayer stack. The artificial anisotropy of thin films structured with a one-dimension sub wavelength grating made by holography is measured. The limitation of the first order homogenization theory is given for two different grating steps. Polarizing coatings or polarization rotators are designed to work in normal incidence by inserting anisotropic films in simple multilayer structures.

The transmission spectra of photonic crystal add-drop filters created in the microwave region are measured. The photonic crystal is a two dimensional square lattice of dielectric rods. The add-drop filters consist of two waveguides formed by removing rods along a line and a cavity lying between the two waveguides. The cavity is formed by removing rods or by replacing them with smaller diameter rods. Depending on the cavity geometry, certain wavelengths can be dropped from one waveguide and added to the other waveguide via resonant coupling through the cavity. A systematic study of the add-drop characteristics is performed as the cavity region is modified. Theoretical results, obtained from finite difference time domain calculations, are in good agreement with measurements.

Nowadays, optical telecommunication systems require an increasing bit-rate. For this reason Dense Wavelength Division Multiplexing (DWDM) systems are currently under development. They need optical sources with a narrow and stable emission spectrum in the C band which should also integrate several emission wavelengths. Glass waveguide lasers enable both the sharp linewidth of optical fiber lasers and the integration possibilities of semiconductor lasers. In this paper, the realization of ion-exchanged waveguide DFB lasers on glass substrates is presented. Phosphate Er-Yb-codoped glass integrated lasers are first investigated for different doping concentrations. The characteristics of these lasers are then compared : each one have low threshold and exhibit single mode output power of several milliwatt for 100 mW launched pump power. The effect of a passivation layer is then studied. Its modelling and experiment shows that the emitted power can be increased by reducing pump scattering losses. Thanks to the use of silver ion exchange technology, a high index increase is obtained which induces an important variation of the waveguide's effective index with its width. Thus, the emission of 15 channels roughly placed on the 100 GHz ITU grid is demonstrated.

Quantum wire lasers and modulators offer superior performance over their quantum well counterparts. This paper presents simulation of an integrated InGaAs-InP quantum wire laser-modulator structure operating at 1.55 μm. In the case of quantum wire lasers, we have computed the optical gain as a function of current density for wires having widths ranging between 60-100 Å. For example, the threshold current density of as low as 61 A/cm² is computed for a wire with a width of 80 Å. In case of quantum wire modulators, we compute the changes in the absorption coefficient and index of refraction due to an external electric field ranging between 0-120kV/cm. For example, the percentage of absorption changes (Δα/α) between 30kV/cm and 60kV/cm applied electric field is about 450% for a 80 Å quantum wire. The changes in electro-absorption or electro-refraction can be maximized by choosing optimum combination of wire dimensions, operating wavelength and electric field to obtain lasing and modulation.

An adjustable extremely short external cavity (ESEC; cavity length 0...50 microns) can be used to tune the wavelength of an edge emitting Fabry-Perot semiconductor laser up to two percents. This means about 30 nm tuning range for the 1550-nm lasers and about 15 nm tuning range for the 800-nm lasers. In addition to the use in WDM and other tunable laser applications, this phenomenon can be directly used in realizing wavelength tuning sensitive near field sensors. In this paper, we discuss the ESEC laser tuning mechanism by using various numerical models and experimentation. We show simulations and experimental results for two different wavelength tuning schemes: a single mirror tuning, and tuning by using a micromachined Fabry Perot interferometer. In addition, we discuss and show results on wavelength tuning enhanced readout in near field optical data storage, and on near field surface profilometry via laser wavelength tuning.

In order to observe smaller stellar objects, interferometric techniques are used. We propose a new recombiner for three telescopes realised by ion-exchanged on glass (K⁺/Na⁺) using a self-imaging multimode waveguide. The first part of this work consists of a theoretical study. We demonstrate that such a component is feasible even if the guided modes are weakly confined. To achieve this goal, we use three different modelling methods: Finite Difference Beam Propagation Method, Guided Modes Analysis and Radiated Modes Analysis. Each of these methods gives different information and permits to design a recombiner fulfilling the astronomical exigencies. The emphasis is put on excess losses, spatial filtering and polarization dependency. After this demonstration, results obtained with a first component used as a power splitter are presented. We conclude by presenting the remaining work.

In this article, the feasibility of a programmable integrated optical grating based on the control of interface charges, and therefore, conductivity of interfaces is explored. This structure is essentially an array waveguide, in which each waveguide has an independent control on its interface conductivity. As we have shown, the effective index of each waveguide is controllable independently, and therefore and relative output phase differences among the waveguides and be programmed. A phase-array-antenna-like analysis enables one to compute the output far field pattern.

The beam propagation method (BPM) is one of the most popular approaches in modeling electromagnetic field propagation. The conventional BPM is established on scalar Helmholtz equation using paraxial approximation. There are limits in the analysis of the vector properties of electromagnetic field and wide-angle propagation. This paper presents the techniques of removing these limits. A full-vectorial BPM bases on finite-difference technique is described from vector wave equations, called finite-difference vectorial beam propagation method (FD-VBPM). The main disadvantage of FD-VBPM is the calculation inefficiency, especially in three dimensional modeling. To obtain two dimensional equivalent structures, a precise optimization approach is adopted. Propagation constant and field of fundamental mode best match those of the original waveguide. The method has very high accuracy. The decoupled semi-vectorial BPM is also derived. The full-vectorial method is extended to wide-angle BPM removing paraxial limit. The method bases on Pade approximant. Simulations are made on rib waveguide.

Periodic structures play an important role in integrated optics. The main purpose of this paper is to study electromagnetic radiation propagating in a one-dimensional periodic dielectric waveguide; or equivalently, in a simple multilayer waveguide. Since periodic dielectrics are photonic crystals, it is beneficial to study their symmetry and periodicity first: inversion, translation, rotation, mirror reflection and time-reversal symmetries; dispersion relations and their behavior of band-pass filters. These principles help us in understanding the propagation of light modes in a periodic layered medium. This simple system exhibits interesting phenomena: photonic band-gaps, localized modes at defects, surface states and omnidirectional reflection, that appear in many optical components, such as diffraction gratings, distributed-feedback lasers, optical waveguides and optical filters. When the periodic dielectric medium is bounded, it becomes a waveguide and light modes that propagate within become guided bodes. Some general and fundamental properties of dielectric waveguide modes are briefly described. Then, by treating the periodic dielectric waveguide as a dielectric perturbed waveguide, propagation of electromagnetic radiation within may be described using the method of variation of constants approach, which formulates the coupled-mode theory. For significant mode coupling, the Bragg reflection type is studied. Finally, more complicated multilayer waveguide structures are briefly mentioned.

Waveguide polarizers with a high extinction ratio can be formed for integrated optics by using artificial birefringent media, including periodic dielectric multilayers, porous dielectric media, and columnar microstructure films. In the waveguide polarizers, the artificial birefringent media is directly loaded onto the core as outer cladding. As the effective refractive index of the periodic dielectric multilayers for the TE polarization is higher than that for the TM polarization, a TM-pass waveguide polarizer can be realized by using the periodic multiplayer designed so that the effective refractive indices for the TE and TM polarizations become higher and lower than that of the core, respectively. On the other hand, the porous dielectric media and columnar microstructure are useful for a TE-pass waveguide polarizer. In this paper, we describe the design and theoretical characteristics of the TE-pass waveguide polarizers using porous alumina layers. The designed TE-pass waveguide polarizers have the extinction ratio of 24 dB, the insertion loss less than 0.01dB, and the device length of 10 mm. In addition, the refractive index of host dielectric for the porous media is investigated for the design of more efficient waveguide polarizers.

We have proposed the optical deflector using arrayed waveguides that have different refractive index fabricated by MOVPE selective area growth. By placing the asymmetric width of SiO₂ mask pattern on both sides of the arrayed waveguide, the thickness of each waveguide in the array has changed gradually. And the phase change in each arrayed waveguide results the deflection of the light. In this device, we have numerically calculated and fabricated the 1xN multi-mode interference (MMI) star coupler using GaInAs/InP MQW structure to input the light equally for each arrayed waveguide. From the numerical calculation, we obtain 0.42dB fluctuation of the output light power in each waveguide in the 1x16 MMI waveguide. In the experiment, we fabricated the 1x16 MMI waveguide using GaInAs/InP MQW structure, and 0.88dB fluctuation of the output light was obtained for the 1.56μm wavelength input light. And further, we have numerically calculated the wavelength demultiplexing and switching performance in this device. We have obtained the wavelength dependence of output power in 8 arrayed waveguides that have 1.0% refractive index difference in both sides of the arrayed waveguide. From this analysis, we can exchange the output ports of each wavelength by controlling the refractive index in the arrayed waveguide.

Model describing pulse propagation along piecewise regular long-haul fiber optic transmission line with unordered structure is proposed. Model is based on decision of waveguide integral transmission parameter as equivalent refractive index. Thus it is able to pass to one-dimensional problem of pulse propagation along optical waveguide. Mentioned problem solution is obtained by methods of wavelet analysis. Wavelet functions are based on Laguerre polynomials. General approach to de-termination of integral parameter applied to waveguides of different types is represented. Calculation algorithm, realizing proposed model, is described. Calculation results for particular examples are represented.

Simulation models of multimode fiber excitation are considered. Methods of calculation of optical emission dispersion pa-rameters in multimode fibers are described. We propose a method of calculation of optical pulse dispersion that makes possible to predict a bandwidth of multimode fibers under singlemode stimulation. A calculation algorithm, based on proposed method, is described. Results for particular examples are represented.

Miniature spectrometers are widely researched now, for their advantages such as compact size, stability and low cost promise a vast application field of spectral systems. The device for dispersion and imaging plays a key role in miniaturization of spectrometers because it is the most important part. In this paper, a kind of novel device based on volume holography is presented, which is intended for miniature and integrated spectrometer. The principles and design method of this device are far different from those of conventional gratings used in spectrometers. By the volume holographic multiplexing technology, the device is completed with several volume gratings recorded in it. Due to the Bragg wavelength selectivity of volume holography, every grating in the device works for just one designed wavelength and does not interfere with each other. So to some extents, the design can be considered as a combination of several detached gratings and the dispersion angle of every designed wavelength could be freely determined by design requirements. In order to record volume gratings that work at different wavelengths at just one recording wavelength, single-wavelength Bragg angle-compensating recording method is used. A device working at eight discrete wavelengths is designed and an optical setup is fabricated to implement it. A Fe:LiNbO₃ crystal is employed as the recording material. Experiments for verifying the device are done and it is found that the device is available.

In this paper, the coupling coefficient between two adjacent waveguides with conducting interfaces is calculated analytically. It is shown that the presence of interface charges, their density being controlled via a transverse voltage, leads to the control of the coupling. TO derive the coupling coefficient, the basic Coupled Mode Theory (CMT) with paraxial approximation is improved to include the effect of conducting interfaces. The analysis is performed independently for TE and TM polarizations. Several direct applications of this effect such as multiplexer, coupler and Mach/Zhender modulator/switch and programmable grating are introduced

The optical fiber, which offers a large bandwidth (about five TeraHertz per telecommunication window), can be fully used only if the techniques of multiple access are sufficiently effective. Our technology based on an organic-inorganic material offers a solution for the realization of the coupling and the decoupling of transmitted channels: in addition to the multiplexer with division by wavelength (WDM) based on multimode interference couplers, we present here a system of multiple access with division by code (CDMA) using multimode interference couplers as well.

1.%μm DFB LD butt-joint integrated with vertical tapered spotsize converter was fabricated by LP-MOVPE. The vertical far field angle (FWHM) was decreased from 34° to 10°, the threshold currents was as low at 19.8mA, the output power was 9.6mw at 100mA without HR coating and the SMSR was 35.8dB. The 1-dBm misalignment tolerance was 3.2μm, while the counterpart of the device without SSC was 2.2μm

The scalability to mass production and low cost are two driving forces towards multimode waveguide technologies. Organic-inorganic hybrid materials realized by sol-gel technology are promising choices for the fabrication of integrated optical circuits. This paper describes fabrication and characterization of the photo-patternable materials that are based on the sol-gel technology. The materials can be processed directly, using UV lithographic processing. Tailored polymeric materials are achieved, avoiding the use of the previously developed pre-hydrolyzed zirconium sol-gel precursors, which exhibit a lack of environmental stability. Films, which behave as a negative tone photoresist under UV-exposure, are fabricated by the spin-coating method on various substrates. The procedure shows the possibility for tailoring the refractive index and birefringence of the materials by varying the composition concentrations of the hybrid polymer system. Refractive indices vary from 1.4770 to 1.4950. The synthesized material also exhibits the possibility for birefringence optimization depending on the composition concentrations. The direct lithography process was demonstrated on various substrate materials (i.e., silicon wafer, glass, quartz, as well as flexible plastics, LTCC and semiconductor materials). The film waveguides are characterized by using of prism coupling technique at various wavelengths. The morphology of the optical structures is measured with a white-light interferometer.

Miniaturization of waveguide circuits is inherently connected with the implementation of highly confined waveguides as one prerequisite for the building of sharp bends and optical microring circuits. Integrated optical ring resonators are promising candidates for compact optical filters and wavelength (de)multiplexers. Their realization in active semiconductor material opens the potential to verify "lossless" filter devices as well as novel laser components with outstanding performance. Since ring resonators do not require facets or gratings for optical feedback they are particularly suited for monolithic integration. Design and technology for device fabrication are summarized. Recent results on transmission and emission mode characteristics of fabricated passive ring resonators as well as gain-included "all-active" resonators in the transmission and emission mode are presented.