We present a review of our work on the micro/nano-scale design, fabrication and integration of optical waveguide arrays and devices for applications in a newly-conceived optical module system that we call "optical printed circuit board" (O-PCBs) and VLSI micro/nano-photonic integrated circuit. The O-PCBs consist of planar circuits and arrays of waveguides and devices of various dimensions and characteristics to perform the functions of transporting, switching, routing and distributing optical signals on flat modular boards. The VLSI micro/nano-photonic integrated circuits perform similar functions on a chip scale. O-PCBs consist of planar circuits and arrays of waveguides and devices of various dimensions and characteristics to perform the functions of transporting, switching, routing and distributing optical signals on flat modular boards. Fundamentally it contrasts with the electrical printed circuit board (E-PCB), which is designed to perform transporting, processing and distributing electrical signals. We have assembled O-PCBs using optical waveguide arrays and circuits made of polymer materials and have examined information handling performances when they are interconnected with the micro-laser arrays, detector arrays and optoelectronic devices. For VLSI nano-scale photonic inte-gration and applications, we designed power splitters and waveguide filters using photonic band-gap crystals and plasmonic waveguide structures. We discuss scientific issues and technological issues concerning the minia-turization, interconnection, and integration of micro/nano-photonic devices and circuits and discuss potential utilities of O-PCBs and VLSI micro/nano-photonics for applications in computers, telecommunication systems, transportation systems, and bio-sensing microsystems.

Photonic Crystals (PCs) are a promising technology for the realization of high-density optical integrated circuits. Photonic Crystal-based couplers have been proposed as a compact means of achieving Wavelength Multiplexing and Demultiplexing. However, the performance of such devices can be limited by fabrication imperfections such as rod size non-uniformities. In this paper, Coupled Mode Theory (CMT) is applied in order to study the implication of the variation of the size of the rods. CMT can provide a useful insight in the effect of size variations, and unlike other numerical methods such as the Finite Difference Time Domain (FDTD), it does not require excessive computational time. Using CMT, the relation between the size non-uniformities and the coupler's insertion loss and extinction ratio is analyzed. It is shown even a small size variation of the order of 2%-3% can degrade the performance of the device.

Embedding of optoelectrical, optical, and electrical functionalities into low-cost products like product packages and printed matter can be used to increase their information content. For these purposes, components like displays, photodetectors, light sources, solar cells, battery elements, diffractive optical elements, lightguides, electrical conductors, resistors, transistors, switching elements etc. and their integration to functional modules are required. Also the need of rapid and reliable di-agnostic systems for wellness and healthcare applications is apparent. Today the time from sampling to result can take hours or even several days. In future the target is to analyze the sample within a few minutes for further action. Additionally, the price of the components for low-end products and disposable sensors has to be in cent scale or preferably below that. Therefore, new, cost-effective, and volume scale capable manufacturing techniques are required. Recent developments of liquid-phase processable electrical and optical polymeric, inorganic, and hybrid material inks together with biocompatible materials have made it possible to fabricate functional components by conventional roll-to-roll techniques such as gravure printing on flexible paper and plastic like substrates. In this paper, we show our current achievements in the field of roll-to-roll fabricated electronics, optoelec-tronics and biosensors. With examples of light guiding structures, organic light emitting diodes, biocompatible materials etc., we demonstrate the huge potential of roll to roll fabrication as a low cost mass production technology for future low end electronic products.

Polymeric optical waveguides and devices are becoming attractive for communication systems, sensors, and signal processing. Different polymers have different characteristics, and affect the fabrication processes and performances of the fabricated polymer devices. Optical waveguide amplifiers have been fabricated using erbium and ytterbium rare earth ions codopants in epoxy novalak resin. The absorption spectrum shows that the presence of Yb³⁺ ions enhances the absorption efficiency of Er³⁺ ions, and Er³⁺ luminescence at a wavelength of ~1.54μm was observed. Er³⁺-Yb³⁺ codoped polymeric channel waveguides were fabricated using electron beam direct writing and UV direct printing. With an input signal power of <-18dBm, an optical gain of 13dB at a wavelength of 1.533μm was measured in an 18mm long multimode channel waveguide.

Photonic on CMOS represents the combination of CMOS technology with integrated optics components. It can bring either a new functionality to the electronic circuit or the driving and the amplifying means to the optical components. In the first case, as global interconnections are expected to face severe limitations in the future, optical interconnects could be an alternative to electrical ones. An integration scheme for an optical signal distribution compatible with a Back End Of the Line microelectronic process is presented. Fabrication of the waveguides on top of Integrated Circuits is followed by the molecular bonding of InP dies, needed to perform the optoelectronic components (sources and detectors). Using PECVD silicon nitride or amorphous silicon coupled to PECVD silicon oxide, optical layers and basic components necessary for an optical distribution were developed. Waveguides with low losses (L<2.5dB@1.3μm with Si₃N₄, L<17dB/cm @1.55μm for a:Si as long as compact 90° microbends and MultiMode Interferometer Beamsplitters were achieved. The molecular bonding of InP dies on CMOS wafers was studied for the integration of active components. The InP wafers are sawed to form mm² square dies and are composed of the epitaxial active layers and especially with a sacrificial, etch-stop layer (InGaAs). Molecular bonding of the dies was performed at room temperature and the thickness of the SiO2 bonding layers ranges up to 1μm. After annealing, the dies can support dicing or other mechanical actions with no degradation of the optical properties.

We present a pluggable micro-optical component fabricated with Deep Lithography with Protons, incorporating a micro-mirror for the out-of-plane coupling of light to or from polymer multimode waveguides integrated on a printed circuit board (PCB). This millimeter-sized mass-reproducible component can then be readily inserted into laser ablated cavities. The roughness of the optical surfaces of the component is measured using a non-contact optical profiler, showing a local average RMS roughness around 30nm. Non-sequential ray-tracing simulations are performed to predict the optical performance of the component, showing coupling efficiencies up to 78% and a rigorous study on misalignment tolerances is performed. These results are then experimentally verified using piezo-motorized positioning equipment with submicron accuracy. As a first step, we characterize the component in a multimode fiber-to-fiber coupling scheme, showing coupling efficiencies up to 56%. As a second testbed, we use multimode waveguides patterned by UV-exposure in Truemode™ polymer, incorporating excimer laser ablated cavities. The size and depth of the cavities can be easily adapted on the design of the coupling structure, whereas alignment marks can be defined in the same processing step. Due to the multimode character of the waveguides, the total internal reflection condition is not always fully satisfied. Therefore, we investigate the application of a metal reflection coating on the micro-mirrors to improve the coupling efficiency. The fabricated coupling components are suitable for low-cost mass production since the compatibility of our prototyping technology with standard replication techniques, such as hot embossing and injection molding, has been shown before.

We study light amplification and laser emission in polymer gain media containing a near-infrared emitting dye, 2-(6-(4-dimethylaminophenyl)-2,4-neopentylene-1,3,5-hexatrienyl)-3-methyl-benzothiazolium perchlorat, with a view to the development of polymer amplifiers and lasers operating in the 800-nm region of the spectrum. Nanosecond gain spectroscopy is carried out by use of amplified spontaneous emission. Multimoded poly(1-vinyl-2-pyrrolidone)-base planar waveguides, 50 μm in thickness, doped with 0.5 wt% dye show a moderate net small-signal gain coefficient of 2.6±0.3 cm^-1 (11.3±1.3 dB/cm) at 820 nm for the pump fluence of 115 μJ/cm² (23.1 kW/cm²). Moreover, we have fabricated polymer microring cavities 200 μm in diameter with the same material composition. The moderate optical gain in the material allows laser emission to occur at around 840 nm under transverse nanosecond photoexcitation at 532 nm. The threshold for lasing is found to be 311 μJ/cm² (62.2 kW/cm²).

Photonics previously has been used in the all-analog and all-digital domain for processing of Radio Frequency (RF) Signals. This paper highlights recent work by the Riza group on a new hybrid analog-digital approach to RF signal processing and controls. Specifically, novels works will be described in the design of RF processing components such as fiberoptic attenuator, fiber-optic programmable delay lines, and optical transversal filters.

Wavelength selective Bragg grating filters in form of periodic modulation of the refractive index along the waveguide can be laser-imprinted in fibers and planar lightwave circuits (PLC)s utilizing UV photosensitivity of the Ge-doped silica core material. Such gratings have a potential to be extensively used in dense wavelength division multiplexing (DWDM) systems in many optical components including add/drop multiplexers. As a bit rates in DWDM systems continuously increase, these components must have low group delay dispersion as well as steep filter characteristics. In this paper we present fabrication technology and optical characteristics of PLC Bragg gratings and grating assisted Add/Drop multiplexers (ADM)s developed for 40 Gbps DWDM systems. Mach-Zehnder interferometer (MZI)-based ADM structures were fabricated with silica-on-silicon planar technology using Plasma Enhanced Chemical Vapor Deposition and subsequent Reactive Ion Etching. The MZI consisted of two 3dB couplers and two identical Bragg gratings UV-imprinted in both arms of the interferometer. For imprinting of gratings in (PLC)s a computer controlled interferometer with special configuration was designed and fabricated. The interferometer allows writing gratings with periods corresponding to any wavelength within C-band. Gratings as short as 4 mm can give over 30 dB suppression of the reflected channel. If needed, group delay compensation can be introduced by programmable phase perturbation during grating writing. The fabricated ADMs have been tested and shown 0.4 nm flat top transmission bandwidth measured in the Drop port. Clear eye openings at 40 Gbps have been obtained, when tested with SHF 5005A multiplexer and Agilent 86100B digital sampling oscilloscope.

Silicon micromachining benefits from the small scale and the facility of integration with electronic circuits and sensors resulting in production of miniaturized and smart microsystems with moving parts. The dimensional scale of MEMS/MOEMS devices is immediately compatible with the size of Integrated Optics, and is appropriate to control or manipulate optical radiations. This technology is suitable to fabricate precision-defined optical components and offers easy alignment procedures of optical parts. This paper examines the contribution of micromachined structures in the specific context of optical microsensors.

An optically switchable microphotonic splitter with a low insertion loss and a low driving voltage is developed using carrier injection in a silicon-germanium material for optical communication systems and networks at a wavelength of 1.55 um. The device structure has been improved based on a symmetrical traditional Y-shaped configuration by using two widened carrier injection regions. The device has a threshold voltage of 1.0 V and a corresponding threshold current of 85 mA on one of the two output waveguide arms. The calculated driving current density is 5.7 kA/cm² and the calculated power consumption is 85 mW at the 85 mA of threshold current. The measured insertion loss and the crosstalk are 5.2 dB and -9.6 dB, respectively, at driving voltage over 2 V.

On the foundation of joint experience acquired by several research centres there was defined the roadmap to the desired single technological platform for fabrication of a specific class of photonic integrated circuits, which are controlled by mechanical means. In the paper the challenges of fabrication of such photonic circuits are discussed. The main arguments in favour of the Silicon-on-Insulator materials system as the basis for the platform are presented. Options for the mechanics-to-optics arrangement, materials and processes are described and illustrated with the current achievements from the authors' labs. In the roadmap the preference is given to the vertical arrangement in which, the mechanical part is stacked above the waveguiding layer. A flexible trimming routine is designed to complement the process flow if the technologies developed cannot provide the required reproducibility.

Recent development trends in InP-based optoelectronic devices are illustrated by means of selected examples. These include lasers for uncooled operation and direct modulation at 10 Gbit/s, complex-coupled lasers, which exhibit particularly low sensitivity to back reflections as well as monolithic mode-locked semiconductor lasers as ps-pulse sources for OTDM applications. Furthermore, a Mach-Zehnder interferometer modulator for high bit rate applications (40 Gbit/s and beyond) is described, and finally, photoreceivers and ultra high-speed waveguide-integrated photodiodes with > 100 GHz bandwidth are presented, which are key component for high bit rate systems, advanced modulation format transmission links, and for high speed measurement equipment as well.

Planar Photonic Circuits can perform many useful functions in optical communications systems, such as wavelength division multilplexing (WDM), optical channel add/drop, fibre/waveguide coupling, and amplifier gain equalization. They perform these functions by the interaction of the device structure with the light inside them. There are very effective and proven numerical methods available for modelling this interaction, such as the Beam Propagation Method (BPM), the Finite Difference Time Domain (FDTD) method, and coupled mode theory (CMT). However, these methods work on a microscopic level (typically the smallest distance is about 0.1 microns), but photonic circuits, on the other hand, can occupy an entire wafer (scale: 10 cm). The analysis must span 5 or more orders of magnitude in the change in scale. The successful analysis needs to combine the basic microscopic techniques with an approach at a more abstract, or system, level. It is interesting that software designed for the analysis of optical communication systems can be applied to planar photonic circuits. This paper shows an example of a practical photonic circuit, a lattice filter, that cannot be analysed by BPM alone. It will be demonstrated that when used with a system level analysis, the whole device can be simulated.

Multimode interference (MMI) laser diode devices have been developed for a large number of optoelectronic applications. Frequency domain methods have been widely used to simulate the behavior of this class of device at fixed operating wavelengths. However time domain models are becoming more popular in photonic simulations as they are able to more accurately model the nonlinear optical gain media such as that present in the saturable absorber section used in the MMI laser diode. A detailed understanding of the electrodynamic behavior of this kind of device is most easily accessed using a time domain method. Therefore we have developed a time domain simulator: employing a full band (FB) time-domain beam propagation method (TD-BPM) for modeling laser devices. By making physically consistent approximations, the proposed method can obtain accurate results for the broadband electromagnetic response with a much larger time step size than those required by other conventional numerical techniques. In order to approximate saturable gain media used in laser device, we have extended the FB-TDBPM algorithm to include frequency-dependent saturable gain by using a Z transform technique. In this paper we will present this approach and its application to the time domain modeling of laser devices.

A polarization ray tracing algorithm which calculates intensities of rays propagating in uniaxial birefringent media is presented. Calculations in this algorithm are performed on vectors in the global coordinate system, obviating the need for frequent conversions between global and local coordinate systems. For the first time, to the best of author's knowledge, a full ray tracing analysis of a Wollaston prism is presented as a calculation example.

The results of studying quasi-stationary optical pulses in single-mode semiconductor laser waveguides, being periodically domained in a direction of passing the waves, are presented. Steady states of the issuing optical pulses occur due to reshaping the incoming optical pulses via the passive mode-locking process in traveling-wave regime. The relations between the pulse parameters and the waveguides' properties are chosen in such a way that the mode-locking process is incoherent in behavior that leads to the phase decay of the incoming pulses. The analysis demonstrates that both the sequences of pulses and bright or dark optical solitons can be supported by such waveguide structures with a quasi-linear gain and a fast-relaxing saturable absorption. Reaching the steady state in pulse parameters is described in terms of the diffusive instability.

In the last years much effort has been taken to arrive at optical integrated circuits with high complexity and advanced functionality. For this aim high index contrast structures are employed that allow for a large number of functional elements within a given chip area: VLSI photonics. It is shown that optical microresonators can be considered as promising basic building blocks for filtering, amplification, modulation, switching and sensing. Active functions can be obtained by monolithic integration or a hybrid approach using materials with thermo-, electro- and opto-optic properties and materials with optical gain. Examples are mainly taken from work at MESA⁺.

Nanophotonics promise a dramatic scale reduction compared to contemporary photonic components. This allows the integration of many functions onto a chip. Silicon-on-insulator (SOI) is an ideal material for nanophotonics. It consists of a thin layer of silicon on top of an oxide buffer. In combination with high-resolution lithography, one can define a high refractive index contrast both in horizontally and vertically, resulting in a tight confinement of light. Moreover, SOI can be processed with industrial tools now used for silicon microelectronics. There are two candidates for nanophotonic waveguides. Photonic wires are basically conventional waveguides with reduced dimensions and a high refractive index contrast. These waveguides with submicron dimensions can have bend radii of only a few micrometres. The alternative is to use photonic crystals, which confine light by the photonic band gap effect. Introducing defects in a photonic crystal creates waveguides and other functional components. To make nanophotonics commercially viably, mass-manufacturing technology is needed. While e-beam lithography delivers the required accuracy for nanophotonic structures, it is too slow. We have used deep-UV lithography, used for advanced CMOS fabrication, to make nanophotonic waveguides. The fabrication quality is very good, which translates to low propagation losses. E.g. a 500nm (single-mode) photonic wire has a propagation loss of only 0.24dB/mm. Using these low-loss waveguides, we have implemented a variety of nanophotonic components, including ring resonators and arrayed waveguide gratings.

Polymeric optical waveguide components offer attractive properties for applications in optical telecom and datacom systems. These are high speed for electro-optic modulators, low power dissipation for thermo-optic (digital) switches and low-cost for all active and passive components. We report on active and passive components realized by utilizing polymer-specific attractive techniques such as planarizing spincoating, low-temperature reflowing and direct photodefinition. Examples are multimode photodefined passive polymeric waveguides for optical interconnect applications; photodefined monomode polymeric waveguides loaded with rare-earth doped nanoparticles for planar waveguide amplifiers and with non-linear chromophores for electro-optic modulators. We will show that polymer waveguide technology allows vertical stacking of electro-optic microringresonators with their port waveguides to realize high-speed modulators. By reflowing the reactive-ion-etched microring we could reduce the scattering by wall roughness considerably. Thermo-optic polymeric microringresonators combine the high thermo-optic coefficient and low thermal conductivity of polymers with the small size of the microring. It will be shown that this yields a broad wavelength tuning range at low power dissipation.

Basic steps involved in the fabrication of integrated optical elements will be presented. Emphasis will be put on the development steps required to establish an Integrated Optical Technology based on silicon, which includes from the definition of the waveguide structure to the fabrication and characterization procedures. Aspects such as the numerical simulation of the components, the design of the optical element suitable as sensor, the analysis of the light input coupling methods, and the process parameters fitting according to the required materials will be highlighted in this paper. Finally, two examples will be presented, show its applicability of the developed technological steps. An "optode," or optical absorption sensor, suitable for the measurement of chemical concentration of a given ion in solution, due to modulation of the complex part of the refractive index (RI), and a biosensor based on the coupling efficiency of an optical waveguide cantilever.

Fundamental technologies of GaAs-based two-dimensional photonic crystals (2DPCs) and an application to ultra-small photonic integrated devices/circuits including future ultra-fast all-optical signal processing devices are reviewed. The review is focusing on the precise nano-fabrication of air-hole lattices and resultant excellent 2DPC waveguide characteristics. Demonstrated results include low propagation loss, high transmittance spectra with large out-of band attenuation in a near infrared region, wavelength-selective directional coupler operation, successful experimental simulation on an optical interference in intentionally designed asymetric MZ waveguide pattern and large nonlinear phase-shift appearance at low excited energy. Application of these results to an ultra-small and ulta-fast symmetric Mach-Zehnder type all-optical switch resulted in the measured switching window width of 15 ps and switching energy of 100 fJ at a 1.3-μm wavelength.

The authors present a successful design, realisation and characterisation of single-mode TE₀₀-TM₀₀ rib optical waveguides composed of SU-8/SOG polymers subjected (or not) to an apt fluorine-plasma treatment. Such techniques based on radiofrequency fluorine plasma treatment (CF₄) proved to strongly modify the properties regarding optical losses due to propagation (selectivity on the polarisation modes, and so on). After realisation of sundry single mode optical waveguides (straight, S-bends, Y-junctions, Mach-Zehnder (MZ) interferometers), the linear absorption coefficient of energy α^TE-TM of such rib waveguides have been measured for both optical modes TE₀₀ and TM₀₀ on Si/SiO₂/SU-8 structures that yield optical losses of 1.36 dB/cm and 2.01 dB/cm respectively. Optical losses ascribed to Si/SiO₂/SOG/SU-8 microstructures have been evaluated to 2.33 dB/cm and 2.95 dB/cm for both polarisations. Concerning the fluorine plasma treatment on SU-8 polymer waveguides, the optical losses regarding Si/SiO₂/Fluorinated SU-8 microstructures have been evaluated to 1.25 dB/cm for TE₀₀ polarisation, having then been reduced by 0.11 dB/cm, compared to propagation in pure SU-8. Moreover, such a specific plasma treatment leads to a substantial selectivity on optical polarisation states regarding the TM₀₀ optical mode which has been advantageously used. Thereby, integrated optical polarizers have been achieved on fluorinated SU-8. Hence, as a crucial step for designing polymer components devoted to microsensors applications, the SU-8 (fluorinated or not) polymer appears as a promising candidate for integrated optics with low optical losses.

The characterization and optimization of a quad beam all-polymer optical accelerometer is presented in this paper. The working principle is based in the intensity modulation, due to the misalignment between three waveguides when acceleration is applied. Analytical, mechanical and optical simulations predict a high sensitivity of the proposed devices. Optimization of both the seismic mass/mechanical beams joint and the sacrificial layer are also presented. Experimental results shows an optical sensitivity of at least 15.8 dB/g, with an asymmetrical behavior attributable to a small misalignment between the waveguides when no acceleration is applied.

Solid state single photon detectors are getting more and more attention in various areas of applied physics: optical sensors, communication, quantum key distribution, optical ranging and Lidar, time resolved spectroscopy, opaque media imaging and ballistic photon identification. Avalanche photodiodes specifically designed for single photon counting semiconductor avalanche structures have been developed on the basis of various materials: Si, Ge, GaP, GaAsP and InGaAs/InGaAsP at the Czech Technical University in Prague during the last 20 years. They have been tailored for numerous applications. Recently, there is a strong demand for the photon counting detector in a form of an array; even small arrays 10x1 or 3x3 are of great importance for users. Although the photon counting array can be manufactured, there exists a serious limitation for its performance: the optical cross-talk between individual detecting cells. This cross-talk is caused by the optical emission of the avalanche photon counting structure which accompanies the photon detection process. We have studied in detail the optical emission of the avalanche photon counting structure in the silicon shallow junction type photodiode. The timing properties, radiation pattern and spectral distribution of the emitted light have been measured for various detection structures and their different operating conditions. The ultimate limit for the cross-talk has been determined and the methods for its limitation have been proposed.

Amorphous chalcogenide films can play a motivating role in the development of integrated planar optical circuits and their components. The aim of the present investigation was to optimize deposition conditions of pure and Tm³⁺ or Er³⁺ doped sulphide films by PLD and rf magnetron sputtering system. The study of their compositional, morphological and structural characteristics was realized by MEB-EDS, atomic force, RBS, X-ray diffraction and Raman spectroscopy analyses. Some optical properties (transmittance, index of refraction, optical band gap, etc) of prepared chalcogenide films and the propagation modes measured at 633 nm, 1304 nm and 1540 nm by means of the m-lines prism-coupling configuration were investigated. The whole results point out hopeful perspectives strengthened by the clear observation of the photo-luminescence of erbium and thulium within doped sulphide films.

Electro-optic Mach-Zehnder interferometric (MZI) modulators have been fabricated by proton exchange in LiTaO₃. Electro-optic efficiency of these modulators has been found to be depending on phase composition of H_xLi_1-xTaO₃ waveguide in full accordance with the data of Raman scattering spectroscopy on microscopic contributions in electro-optic effect for the different H_xLi_1-xTaO₃ phases. These spectroscopy data were used to found an appropriate phase composition and, thus, optimize MZI modulators. The experimental samples of MZI modulator fabricated at the optimal technological conditions exhibit the improved electro-optical efficiency with far superior photorefractive resistance compared to the LiNbO₃ waveguides and modulators.

Multimode interference devices based on silicon hollow waveguides have been designed, simulated, fabricated and characterized. Adequate confinement of light into a hollow waveguide and minimization of the propagation losses require a roughness of the structure below the working wavelength. This assures to have mirror behavior at the facets that optimize the Fresnel reflections. In order to achieve this low roughness and a perfectly vertical walls, to obtain a rectangular shape, an optimization of the fabrication process, especially deep reactive ion etching process, has been made. The numerical and experimental anti-symmetrical behavior for symmetrical and anti-symmetrical out waveguides in anti-symmetrical multimode interference devices is in accordance with the theory of multimode interference effects. The excellent behavior and properties of these devices shows the silicon hollow waveguides excellent for the design of integrated optical devices.

Report presents the analysis and comparison of the efficiency different forward error correction methods for optical telecommunications (that include coding gain and redundancy ratio).

An optical power splitter and a spot-size converter in silicon-based photonic crystals have been proposed and demonstrated. The optical power splitter is an extension of conventional 1x2 photonic crystal power splitter to 1x3 and 1x5 scales while the spot-size converter is formed by removing several rows of dielectric rods in different amount from the photonic crystals. The device functionality and performance have been numerically investigated and simulated by finite-difference time-domain method.

The Lau effect refers to interference phenomenon involving double-grating system illuminated by an extended white light source and it has received wide attention. Until now, the Lau effect has been studied regarding double-grating system immersed in homogenous media. A generalization of Lau effect to the case of a GRIN medium is considered. We present an explanation based on the coherence theory. We begin the analysis by describing, in general terms, the propagation of the second-order field correlations in GRIN media, via the cross-spectral density function. This provides the basics for discussing the evolution of the intensity distribution and the cross-spectral density function of the field incident on the second grating. The particular case of a selfoc GRIN medium and two sinusoidal gratings is analyzed.

Most approaches to perform switching and tuning in photonic integrated circuits (PICs) are based on modulation of effective refractive index of a waveguide or a resonant structure and use a variety of means by which the desired perturbation of index is to be achieved. Limitations to these methods, which obstacle achievement of the desired results, are discussed. It is shown that the promising alternative, at least for applications, for which speed is not a critical issue, can be to control light by means of nano/micromechanic actuation. The general idea is presented and the applicability of mechanical actuation to very-large-scale integration (VLSI) photonics is assessed. Particular concepts of switching and tuning are described.

The bacteriorhodopsin film in gelatin matrixes which are used as sensitive elements of integrated optic and fibre-optic sensors of various vapor and gases components will not be able to carry out the chemical control of aqueous solutions. In the given paper the results of technological development of obtaining the bacteriorhodopsin (bR) films in a sol-gel matrix are represented. The films are obtained in a broad thickness range (from 0.5 to 20 microns) with various bR concentrations and photosensitize additives. The optimal technological conditions of obtaining of uniform films with given optical parameters are defined. The surface morphology and cross section of the obtained films was studied using an AFM and SEM. The films have a reasonable surface roughness (~ 100 nm) and a uniform distribution of the purple membrane fragments in the nanostructured sol-gel glass matrix along the films surface and thickness. The transmission spectrums have the characteristic for bR the absorption band, the value of which depends on bR concentration and technological features of the films deposition. The investigated photosensitive properties of the obtained films and influence on them of chemical components of aqueous solutions, allow recommending the thin bR films in sol-gel matrixes for creation of planar waveguides in the role of components of the chemical sensors of liquid solutions.

The paper presents an idea of a reconfigurable optical add-drop multiplexer (ROADM) based on micro/nanomechanically switched micro-ring resonators. Main issues related to the design and fabrication of mechanically controlled ROADM are discussed.

We report on the cost effective fabrication of 45° micromirror couplers within single-mode polymer waveguides for achieving fully embedded board-level optoelectronic interconnections. Compatibility with existing board manufacturing technology is achieved by making use of polymers with high thermal stability. The sol-gel polymers behave as negative photo resist and waveguides are patterned by UV exposure. Micromirrors are fabricated using excimer laser ablation, a very flexible technology that is particularly well suited for structuring of polymers because of their excellent UV-absorption properties and highly non-thermal ablation behavior. A coupling structure based on total internal reflection (TIR) is enhanced by developing a process for embedding a metal coated 45° mirror in the optical layers. The mirrors are selectively metallized using a lift-off process. Filling up the angled via without the presence of air bubbles and providing a flat surface above the mirror is only possible by enhancing the cladding deposition process with ultrasound agitation. Surface roughness of both the mirrors and the upper cladding surface above the mirrors is investigated using a non-contact optical profiler. Initial loss measurements at 1.3 μm show a propagation loss of 0.62 dB/cm and an excess mirror loss of 1.55 dB. During most recent experiments mirror roughness has been reduced from 160 nm to 20 nm, which will seriously reduce the mirror loss.

A qualitative comparison is made between laser direct writing and laser ablation as enabling technologies for the structuring of multimode waveguides (50x50μm²) and 45° micro-mirrors into an optical layer. A small demonstrator is fabricated that allows us to couple light vertically from a transmitter into an optical layer and from the optical layer to a receiver. The optical layer, a multifunctional acrylate-based photo-polymer, is applied on an FR4-substrate. Multimode waveguides, that carry signals in the plane of the optical layer, are fabricated by means of laser direct writing, a technology that is available at HWU. The 45° micro-mirrors, that provide out-of-plane coupling, are ablated with the laser ablation set-up available at UGent. This set-up contains a KrF-excimer laser (248nm) that can be tilted, which eases the definition of angled facets. Surface roughness measurements are performed on both the optical layer and the micro-mirrors with a non-contact optical profiler. Loss measurements are performed on both the waveguides and the micro-mirrors.

Efficient and thermally stable volume holographic gratings in glassy polymeric material based on PMMA and phenanthrenequinone have been recorded. Photosensitive layers were prepared by casting the liquid solution of ingredients on a substrate and drying to a solid state followed by a separation of the polymeric film. This technique was applied to create a possibility to write highly slanted gratings between prisms and to stick them to lightguides with glue. High diffractive efficiencies and moderate angle selectivity of the gratings were reached due to a high concentration of phenanthrenequinone (up to 4 mol.%) making it possible to use the photosensitive layers of lower thicknesses (60 - 150 μm) for the recording of the efficient holographic gratings. The exposing is followed by thermal amplification of the grating due to diffusion of unreacted phenanthrenequinone molecules and fixation by an incoherent optical illumination. The processes of generation, amplification and fixation are discussed for holographic gratings. The holographic gratings were written with an Ar-laser (wavelength 514,5 nm). The grating amplification was realized by heating up of the sample to 50-85°C.

Microring resonators will be one of the most important components of the next generation of optical communications. In this work, we have analyzed from theoretical perspective a new proposed microring resonator structure based on the wafer-bonding technique which implies the vertical coupling between the passive bus waveguide and the active ring resonator. We have investigated the possibility to obtain the monomode operation of the active ring waveguide for certain ring radius values by the selective attenuations of the higher order modes and the obtaining of the desired coupling efficiency by varying the technological parameters like the layers thickness, etching depth, bus waveguide width and the offset (misalignment between the ring and the bus waveguide). Depending on the fabrication method, the misalignment between the ring resonator and the bus waveguide may vary within a significant range. Therefore, we considered a much wider bus waveguide in the coupling region in order to minimise the effects of misalignment.

Efficient optical modulators and switches are the key elements of the future all-optical fiber networks. Aside from numerous advantages, the integrated optical devices suffer from excessive longitudinal dimensions. The dimensions may be significantly reduced with help of periodic structures, such as Bragg gratings, arrayed waveguides or multilayer structures. In this paper we describe methods of analysis and example of analytical results of a photonic switch with properties modified by the application of periodic change of effective refractive index. The switch is composed of a strip-waveguide directional coupler and a transversal Bragg grating.

The use of the holographic lithography method for sub-nano pattering of photoresist layer deposited on bare sapphire substrate as well as on GaN grown by metaloorganic vapour phase epitaxy on Al₂O₃ is reported. Positive photoresist Shipley SPR700 was first diluted with photoresist thinner and then spin-coated on prepared substrates to obtain layers of final thickness of 227nm. Thin photoresist layer was exposed in the holographic setup with wavelength of 355nm to produce the surface relief grating. After development SEM observations reveled well-defined valleys and ridges of diffraction grating in SPR700 deposited on gallium nitride layer whereas the whole structure on sapphire was strongly affected by the speckles created by reflection from the unpolished back surface of the sapphire substrate. Latter, we confirmed with transmission spectroscopy, that even small amount of light transmitted through the substrate, which is back reflected by the unpolished back-surface of sapphire, canstrongly disturb nano-sized features in photoresist.

An optical sensor of ammonia gas, based on the surface plasmon resonance (SPR) method has been investigated. The surface plasmon resonance (SPR) is very sensitive, and so is the optical technique used in chemical sensing. The angle of incident of light at which a resonant effect is observed, as well as the dip of a resonant are very sensitive to variations of the optical parameters of the medium on a surface-active plasmon metal layer. The sensing structures were made as follows. Gold layers were coated by means of vacuum evaporation on a substrate, 1 mm thick, made of a BK7 glass slide. The thickness of Au was about 48 nm. An active sensor layer of WO₃ was deposited by thermal evaporation on the gold film while a Nafion"R" film was coated by means of the spin-coating method. The sensing structures were coupled on immersion oil with a prism coupler. A change of the intensity of light of the plasmon dip was observed when chemical active films (WO₃ or Nafion"R") were exposed to varying concentrations of NH₃. Optical ammonia gas sensors display a very fast response time and a fast regeneration time at room temperature.

This paper presents an analysis of the magnetic field influence on a planar differential interferometer that uses a magneto-sensitive ferronematic layer. Due to a magnetic field interaction a nematic matrix changes its orientation in a TM mode polarization plane. In consequence, a propagation constant changes only for a TM mode, and a phase difference between TE and TM modes is changed under magnetic field influence. An influence of the optical and geometric parameters of the presented structure on the phase difference of propagating modes is presented.

The paper deals with theoretical analysis of new optical fiber structures of D-type which may be applied in optical fiber sensors of electric current. This analysis is based on the following points: light propagation analysis and elastooptic effect induced by magnetostriction effect in optical fiber structures. The main point presents theoretical analysis of magnetic field influence on light propagation. D-type fibers have been designed, produced and tested. The results of measurements of the magneto-optical effect and the distribution of mode fields in such optical fibers have been presented.

The present work suggests a new method of direct measurements of the difference propagation constants Δβ of orthogonal modes (mode beat) of the same order in planar waveguides. The work also presents a method of determining the difference of propagation constants (mode beat) for different refractive indices of the cover. The developed method is particularly adaptable when the difference of propagation constants along the direction of propagation are changed.

Flat light guides are modern solution enabling production of luminaries characterised by large area and low height. The amount of the luminous flux, which might penetrate the side-lit flat light waveguide with a predefined thickness depends on the light source's luminance. Special fluorescent lamps equipped with an internal reflector layer were designed for this kind of illumination systems. Such lamps are typically characterised by small aperture along the spine of the lamp. The aperture technology boosts the luminance value within the lamp's aperture to levels even 4 to 5 times higher than the average luminance of a standard fluorescent lamp. The presented article contains a detailed analysis of the impact of the aperture angle size on the coupling efficiency. It was also shown that application of a mini aperture fluorescent lamp influences changes in the luminous intensity curves of prismatic elements, which are most commonly used to direct the luminous flux.

In recent years, there has been an increasing interest in the design and development of optical waveguides for computer backplanes and intra-card communications. The transition from high speed copper interconnects to optical links is driven by those applications which can most benefit from a greatly increased bandwidth-distance product; this includes rack mounted blade servers, data communication switches and routers, high end enterprise servers, and supercomputers. Typically the candidate applications require hundreds of optical links, each operating at 10 Gigabit per second or higher, for aggregate bandwidths on the order of multi-terabits per second across distances of one to ten meters across a backplane. In this paper, we review some recent developments in polymer-based optical interconnect for these applications. In particular, we report experimental results for arrays of multi-mode acrylate polymer waveguides, fabricated either on the surface of a printed circuit board or embedded within a multi-layer board. Transmission speeds up to 12.5 Gigabit per second have been demonstrated on a single link, with optical attenuation as low as 0.04 dB/cm. Packaging considerations for vertical cavity laser and photodiode arrays will be discussed, including tolerances for passive alignment between waveguides and active components. Finally, we review several recently issued patents for optical backplane connector concepts and their potential applications within the next 3 years.