This paper presents a collective review of our original work on the micro/nano-scale design, fabrication and integration of optical waveguide arrays and devices for what we call generic and application-specific "optical printed circuit boards" (O-PCBs) and VLSI photonic integrated circuits (VLSI-PICs). O-PCBs and VLSI-PICs, both generic or application specific, consist of planar circuits and arrays of polymer waveguides and devices of various dimensions and characteristics to perform the functions of transporting, switching, routing and distributing optical signals on flat modular boards. We fabricate optical wires out of polymer, silica, or silicon materials. Generic O-PCBs and VLSIPICs consist of an optical layer carrying basic forms of optical wires and devices and an electrical layer carrying arrays of electrical wires and devices. Application-specific O-PCBs and VLSI-PICs carry optical layers that are composed of varied forms of optical wires and devices tailored to perform specific functions. For generic structures of O-PCBs and VLSI-PICs, we present theoretical calculations leading to basic design rules for the miniaturization of the waveguide devices and for the maximization of the integration densities of the waveguides and devices to be placed on the board or chips. For application specific O-PCBs we present several examples, including O-PCB and modules for inter-chip optical interconnection for computer systems, an all-optical wavelength splitting triplexer module for subscriber telecommunication systems, MMIs, and a grating module for sensor systems. For VLSI-PICs we present examples of photonic crystal directional couplers, MMIs, power splitters, wavelength splitters, triplexers, and plasmonic directional couplers.

Optical transmission technologies such as Dense-Wavelength Division Multiplexing (DWDM) have emerged in recent years to meet the demand for higher bandwidths and data rates. In order to implement such technologies, accurate determination of channel wavelengths is required. The Fabry-Perot Interferometer (FPI) offers the ability to resolve wavelengths with a 2-5 pm precision in resolution. We present here a novel Generic Lightwave Integrated Chip (GLIC) founded on the FPI. The device has been realised on a Planar Lightwave Circuit (PLC) in SiO₂ on Silicon as a means to achieve the desired rapid wavelength monitoring with high resolution. In this paper, the simulation and characterisation of the device is reported and the advantages of this technology are revealed. The theory is founded on employing the concept of quadrature between 2 phase-shifted signals provided by 2 similar Fabry-Perot cavities to determine the wavelength in question with a sub-microsecond response time. The compact features of the device make it an ideal candidate for application in future silica based PLC DWDM networks. By its generic nature, the device is also an attractive choice for applications in optical sensing and biophotonics.

This paper reports about the design, fabrication and experimental passive compact building blocks (μbend of 2 μm radius, Y junction and Multi Mode Interference (MMI) splitter of 2 μm wide and 4.2 μm long) in a amorphous hydrogenated silicon (a-Si:H) based strip waveguide. The cross section of the waveguide is about 0.5 μm wide and 0.2 μm high.

Optical and electron confinement are utilized to tailor the optical characteristics of active materials and photonic devices. A technique to incorporate semiconductor quantum dots into planar glass waveguides with low propagation loss is demonstrated. The waveguides are fabricated by potassium-sodium and silver-sodium ion exchange processes in glasses that contain PbS quantum dots with radii of a few nanometers. The unique optical properties of the quantum dots are preserved throughout the waveguide fabrication process. We also demonstrate novel compact fiber lasers based on active, highly doped fibers with photonic crystal cladding. The flexibility provided by microstructuring the fiber enables improved fiber laser performance and several Watts of laser output are generated from few centimeters of active fiber.

We investigate the deep-UV-induced refractive index modification of alicyclic methacrylate copolymers for realizing integrated optical circuits for the development of cheap, disposable integrated optical sensors for chemical and biological monitoring. These novel copolymers obtain higher glass transition temperature (Tg), refractive index and lower water absorption than conventional poly(methylmethacrylate) (PMMA). At the same time, the adhesion of living mammalian cells on the UV exposed polymer surface was investigated for the application for biosensor.

We propose in this report an integrated optical phase modulator based on liquid crystals. It consists of an array of embedded channel polymer (ORMOCERTM) waveguides with liquid crystals serving as an active component for phase shifting. The various steps followed for the fabrication of the waveguides along with SEM and AFM scan results are presented. The pre-orientation of the liquid crystal molecules by mechanically rubbing ORMOCLAD coated layer is also shown. Finally, the results of a preliminary experiment performed to ensure the phase modulation from the modulator array geometry are presented.

The interaction of surface acoustic waves (SAWs) and light is spatially restricted to a region close to the surface approximately given by the acoustical wavelength. Therefore optical waveguides very close to the surface are required for high-frequency i.e. short-wavelength acoustic waves. In contrast to existing collinear integrated acoustooptical devices we are aiming at the regime where the optical and acoustical wavelengths are comparable. The periodically modulated refractive index caused by the SAWs may serve as a tunable and switchable optical add/drop comparable to fiber Bragg gratings, though not static. Another aspect of this regime is the phonon energy, which is non-negligible compared to the energy of the photons. So a significant energy shift i.e. wavelength conversion caused by scattering processes can be exploited. Existing integrated optical waveguides based on silica, SOI, lithiumniobate or III-V semiconductors are not suitable for a realization of such components, due to small piezoelectric coefficients or weak optical confinement. In contrast, heterostructures made of II-VI compounds are promising candidates for the proposed applications. Using Beam Propagation simulations we developed an optimized ridge waveguide structure based on a CdSe/CdS heterostructure, grown by molecular beam epitaxy. The waveguide is defined by wet-chemical etching using a standard photoresist mask. The mode field dimensions are about 1 μm x 2 μm, which requires fiber coupling using lensed fibers. We present measured coupling and propagation losses and discuss the integration with acoustical waveguides.

Novel materials, micro-, nano-scale photonic devices, and 'photonic systems on a chip' have become important focuses for global photonics research and development. This interest is driven by the rapidly growing demand for broader bandwidth in optical communication networks, and higher connection density in the interconnection area, as well as a wider range of application areas in, for example, health care, environment monitoring and security. Taken together, chalcogenide, heavy metal fluoride and fluorotellurite glasses offer transmission from ultraviolet to mid-infrared, high optical non-linearity and the ability to include active dopants, offering the potential for developing optical components with a wide range of functionality. Moreover, using single-mode large cross-section glass-based waveguides as an optical integration platform is an elegant solution for the monolithic integration of optical components, in which the glass-based structures act both as waveguides and as an optical bench for integration. We have previously developed a array of techniques for making photonic integrated circuits and devices based on novel glasses. One is fibre-on-glass (FOG), in which the fibres can be doped with different active dopants and pressed onto a glass substrate with a different composition using low-temperature thermal bonding under mechanical compression. Another is hot-embossing, in which a silicon mould is placed on top of a glass sample, and hot-embossing is carried out by applying heat and pressure. In this paper the development of a fabrication technique that combines the FOG and hot-embossing procedures to good advantage is described. Simulation and experimental results are presented.

A variational approach with an arbitrary ansatz is used to derive the governing equations for the characteristic parameters of dispersion-managed solitons. The Gaussian pulses are considered as a particular case. The possibility of soliton propagation when the average dispersion is zero or normal is examined. Both polarization preserving fibers and birefringent fibers are considered.

A structure based on the free-carrier-induced electrorefractive effect in Si/SiGe modulation-doped quantum wells, placed in the intrinsic region of a PIN diode has been proposed. Effective index variation produced by carrier depletion under a reverse bias leads to a phase modulation of a guided wave. The measured variation of the effective index is typically 2.10-4 for a 0V to 6V variation of the reverse bias voltage. This study is focused on the integration of modulation doped SiGe/Si quantum-well optical modulator in SOI submicron rib waveguides with optical losses lower than 0.4dB/cm. The influence of the geometrical parameters, of layer doping and of the metallic contacts has been determined through numerical simulations and optimized modulation structures are defined. The obtained factor of merit L_χV_χ is then of 1.26 V.cm which can be favorably compared with the best published results obtained with other optimized modulators.

We show that by incorporating a filter that removes unwanted stray light, high performance multimode interference couplers with uniformity in splitting ratios of better than 0.03 dB can be designed and fabricated in silicon-on-insulator waveguide technology, allowing the fabrication of very high extinction ratio switches and modulators.

A characterisation technique for packaged Er/Yb-codoped waveguides based on the analysis of laser transient behaviour is studied. A ring laser configuration was used and measurements on the evolution of laser output power during transient regime were carried out. An approximate analytical method was developed for the analysis of this behaviour. A good agreement is obtained for the relevant damped oscillation parameters. The use of this technique for active waveguides characterisation is discussed.

Optical ring/racetrack resonators have the sufficient flexibility to realise many functions in a single device, from filters/multiplexers, to modulators, to switches. The use of Silicon-On-Insulator (SOI) material, coupled with Ultra Large Scale Integration (ULSI) processing techniques, may allow the cost of these devices to become economically advantageous over current components. This paper describes our recent work in developing polarisation independent ring resonators, and subsequent, work on increasing the limited free spectral range and full width half maximum of the resonance. There are two key components that comprise a polarisation-independent racetrack resonator: a polarisation-independent rib waveguide and a polarisation-independent directional coupler. Polarisation independence is achieved in the waveguides when the geometrical design ensures that both polarisation modes propagate with the same effective index. We report on such devices together with polarisation independent couplers, which are achieved by allowing different inter multiples of the coupling length for the TE and the TM modes. By combining these components, the resulting device is a polarisation independent ring resonators. These devices have been thermally modulated by means of a modulated visible laser and alternatively via small heaters fabricated on the waveguides. We have also modelled ring resonator modulators via carrier injection and depletion. Subsequently we have improved the device characteristics by employing smaller bend radii to increase the free spectral range by a factor of 5, and by cascading racetracks to improve the full width half maxima of the resonance by almost 40%. Experimental results are reported for most of the above characteristics. We will further investigate the opportunities for increasing the FSR whilst retaining polarisation independence, the possibility of retaining polarisation independence whilst utilising the properties of the ring resonator to form improved modulators.

Silicon microspheres coupled to optical fibers have been used for optical channel dropping in the near-IR. The observed morphology dependent resonances had quality factors of 100000. These optical resonances provide the necessary narrow linewidths, that are needed for high resolution optical filtering applications in the near-IR. In addition to filtering, detection, and switching applications of this photonic system is studied in the near-IR as well as far-IR. The silicon microsphere shows promise as a building block for silicon photonics in the near-IR as well as, mid-IR, and far-IR.

We present a transfer matrix analysis of a 2-D filter to study its frequency response functions. The (M × N) array consists of N independent columns of micro-ring resonators side-coupled to two channel bus waveguides, with equal spacing between columns and each column consisting of M coupled resonators. We show that the bandgap of the 2-D structure is a superposition of the non-overlapping bandgap of the two 1-D arrays. This non-overlapping property can be used to realize the "near-ideal" filter with flat and sharp passband, negligible sidelobes in the stop bands, and linear phase response over 80% of the passband. The existence of defect mode in linear and lossless ring resonator arrays is also demonstrated. The defect can be introduced by removing one ring or by making one ring bigger or smaller. Defect states within the photonic bandgaps behave like either donor or acceptor modes similar to other photonic crystals. The results based on transfer matrix model shows reasonable agreement with finite difference time domain (FDTD) simulations.

Integrated optics demand waveguides on Si platforms with different funtionalities and thus thin film technologies become essential tools for its development. Incorporating rare-earth ions or metal nanoparticales in dielectric hosts are respectively of interest for producing active media for gain devices or non-linear optical media with a high potential for all-optical switching. In this work, pulsed laser deposition is used to produce these materials with "dopant" distributions controlled within the nanometre scale embedded in a deilectric host. Examples will be given in which the control of this distribution is essential for achieving optimised optical transmission, propagation losses or photoluminescence lifetime. These examples are additionally used to show that controlling the separation between "dopants" becomes a useful tool to provide new insights in the understanding of interaction mechanisms.

We report on an experimental study of waveguide lasers in Er/Yb-codoped phosphate glass. The waveguides serving as laser cavities were fabricated by electric field assisted silver-film ion exchange technology. Threshold power, slope efficiency, and output power were measured from these lasers and compared to previously reported data. We also report on waveguide DBR-lasers using photowritten gratings in a hybrid glass.

Low frequency Raman scattering on the acoustic vibrational modes of nanoparticles has been used for determining the size of dielectric, semiconductor and metal nanoparticles embedded in glass. This contribution reports on application of low-frequency Raman scattering on acoustical vibrational modes of nanoparticles. The theoretical background as well as the experimental results of free non-interacting nanoparticles as well as glass containing different nanoparticles for optoelectronics will be presented. The approach is based on a 1/ν dependence of the Raman light of the vibration coupling coefficient and on the fact that each nanocrystallite of diameter D vibrates with its eigenfrequency ν~1/D. The Raman scattering spectra are analyzed using confined acoustical vibrations model. The model-calculation considered homogeneous broadening of the confined acoustical modes due to interaction of the particles with matrix and inhomogeneous broadening due to the contribution of the Raman scattering from the particles of different sizes. The low frequency Raman spectra of different nanoparticles (nc-TiO₂, nc-SnO₂, nc-CdS_xSe_1-x, and nc-Si) prepared by Physical Vapour Deposition, thermal quenching and thereafter annealing of glass and sol-gel techniques was used for determination of particles size distribution and results were compared to TEM. The Raman spectroscopy technique has proved to be a simple and fast method that has favorable statistical characteristics due to the macroscopic probe volume and makes in situ measurements possible.

Er³⁺/Yb3^+-codoped 95.8 SiO₂-4.2 HfO₂ planar waveguide was fabricated by the rf-sputtering technique. The sample was doped with 0.2 mol% Er and 0.2 mol% Yb. The thickness and the refractive indices of the waveguide were measured by an m-line apparatus operating at 543.5, 632.8, 1319 and 1542 nm. The losses, for the TE₀ mode, were evaluated at 632.8, 1319 and 1542 nm. The structural properties were investigated with energy dispersive spectroscopy and Raman spectroscopy. The waveguide had a single-mode at 1.3 and 1.5 μm and an attenuation coefficient of 0.2 dB/cm at 1.5 μm was obtained. The emission of ⁴I13/2->⁴I15/2 of Er³⁺ ion transition with a 42 nm bandwidth was observed upon excitation in the TE₀ mode at 980 and 514.5 nm. The ⁴I_13/2 level decay curves presented a single-exponential profile, with a lifetime of 4.6 ms. Back energy transfer from Er³⁺ to Yb³⁺ was demonstrated by measurement of Yb³⁺ emission upon Er³⁺ excitation at 514.5 nm. Photoluminescence excitation spectroscopy was used to obtain information about the effective excitation efficiency of Er³⁺ ions by co-doping with Yb³⁺ ions. Channel waveguides in rib configuration were obtained by etching the active film by a wet etching process. Scanning Electron Microscopy was used to analyze the morphology of the waveguides.

Since the discovery of optical fibers, the possibility to develop optically confined structures has opened new possibilities for making novel optical components. Rare earth-activated confined structures thus offer interesting solutions for this end. A growing activity in this field is aimed at the development of optical amplifiers in planar form based on rare-earthactivated glasses to provide devices such as lossless splitters, which can find applications in the metropolitan and local area networks. A further development to enhance the spectroscopic properties is achieved by rare-earth co-activated nanocomposite materials, also in planar format. The aim of this paper is to give a review concerning the advances in glass-based photonic systems, where light confinement or the presence of nanostructured hosts for the rare-earth induces an enhancement and a control of the optical and/or spectroscopic properties.

Using a femtosecond laser source waveguide, Bragg grating and waveguide-Bragg grating (WBG) structures have been written in fused silica and undoped phosphate glasses. The WBG devices are written using a slit focusing geometry and point-by-point grating inscription method. They demonstrate Bragg reflectivities at the design wavelength (1550 nm) and have been used as a new method for estimating the minimum refractive index change induced during the waveguide writing process.

Erbium-doped silicon-rich dielectrics are expected to lead to compact and scalable cost-effective optical amplifiers due to the high sensing of Er via nano-silicon. Different silicates glasses, namely: Aluminum-silicates, soda-lime glasses and fused silica codoped with Si and Er were used in order to explore the mechanism of energy transfer from Si nanoclusters (Si nc) to Er. Si excess of 5 and 15 at.% and different Er doses, so that the resulting Er peak concentration could vary from 2x10¹⁹ up to 6x10²⁰ cm^-3, were introduced in the wafers by ion implantation technique. Thermal treatments in a rapid thermal process were carried out before and after Er implantation in order to precipitate Si nc, and to find the accurate temperature to obtain the best Er emission around 1540 nm. Very intense emission, comparing to structures only doped with Er, has been detected in all co-implanted glasses. By time resolved photoluminescence experiments we measured lifetimes of the exited state of Er³⁺ ions ranging from 2.5 to 12 ms and an effective excitation cross-section about 1x10^-17 - 6 x10^-17 cm² (depending on the Er dose and Si excess). This is orders of magnitude higher than the Er direct absorption cross-section (about 10-21 cm2). By quantifying Er emission we found only 10% of the total Er concentration was effectively excited through Si nc.

Article reports low loss (better than 0.09dB/cm) germano-silicate planar devices, operating at 1550nm wavelength, with optical combiner/splitters exhibiting greater splitting uniformity (~ 0.08dB) based on multimode interferences with index contrast ~ 0.7%. Excess loss of the device was improved by 0.41dB by designing output access waveguides with two S-bends operating in the Whispering-Gallery-Mode regime (WGM). The total S-bend loss was improved by inserting a straight waveguide between two cured sections, instead of two oppositely curved sections as in the conventional S-bends. This is expected to reduce transition loss about four times the transition loss between two oppositely curved sections. Optimised offsets, between waveguides of different radii, and widening of curved sections resulted in low excess loss while preserving device compactness. The separation of the output access waveguides was limited to just 250μm, for pigtailing/butt-coupling of SMF fibres, to ensure device compactness for future high-density packaging. Silica and doped-silica on silicon films were formed at low temperature, <350°C, with high deposition rates, greater than 1600 Angstroms/min, using plasma enhanced chemical vapour deposition (PECVD) technology that suits for mass production. Fabricated lightwave circuits were characterised with special care in order to avoid ambiguities that would arise from power fluctuation in the launching laser source during measurements.

A temperature sensor immune to electromagnetic noise is designed and fabricated. The sensor key element is a periodically poled lithium niobate (PPLN) substrate. PPLN allows a direct and efficient frequency conversion of lightwave through the quasi-phase matching (QPM) of the pump radiation propagating at the fundamental and second harmonic wavelengths. For these devices, the efficiency of second harmonic generation (SHG) depends on the QPM condition, and it strongly changes with respect to the wavelength and the temperature. The effect of temperature variation on the SHG in periodically poled lithium niobate annealed proton exchange (APE) channel waveguides (WG) is theoretically modeled via a home-made computer code and experimentally validated via a suitable measurement set-up. A lot of simulations have been performed to test the temperature sensor feasibility and to identify its optimal configuration. Another sensor configuration made by two waveguides with suitable gratings of inverted ferroelectric domains is designed and refined, too. For an optimised PPLN-WG device, which could be fabricated through electric field poling and annealed proton exchange or titanium diffusion, a sensitivity S≡0.03μW/°C for the temperature range equal to 100 °C is demonstrated by using an input power at a fundamental wavelength equal to 40 mW. Similar evaluations and measurements, performed on bulk substrates, allowed us to design a layout of a sensor particularly suited for rugged in-field applications.

Wavelength conversion with high contrast ratio and low OSNR penalty has been achieved by using a resonant vertical-cavity all-optical switch based on saturable absorption in multiple-quantum-wells. The device was grown by MBE on InP substrate. It comprised a 19.5 pairs n⁺-Ga_0.47In_0.53As/InP bottom DBR, 28 Ga_0.47In_0.53As QWs, and a 50% reflective top dielectric mirror. We carried out conversion experiments between a wavelength-tunable modulated pump signal and a CW beam with a wavelength matching the Fabry-Perot resonance of the switch. Using a 622 Mb/s modulated pump with an average power of only 6-dBm we have demonstrated a 15 dB extinction ratio for the converted signal. The wavelength conversion process exhibited a weak dependence on the pump signal wavelength; we have achieved wavelength conversion in a range of 20 nm. BER/OSNR measurements on the wavelength converted data signal indicated a maximum OSNR penalty (at a BER=10^-9) of about 2.5 dB, with respect to the input pump data, over the entire conversion range. Error free operation was observed up to 2 Gb/s when device performance degraded due to its long absorption recovery time. However, with further optimization, the device recovery time could be reduced to the picosecond range, extending its application to much higher date rates.

High energy helium beam has been utilized to pattern silicon prior to electrochemical etching in hydrofluoric acid. Photoluminescence (PL) studies carried out on medium resistivity silicon showed that the PL wavelength of the irradiated regions is continuously red-shifted by up to 150 nm with increasing dose. On the lower resistivity silicon, the intensity is shown to increase by more than twenty times with dose. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) have been used to determine the surface morphology of the irradiated structure. This technique is potentially important for producing an integrated silicon based optoelectronic device.

In recent years there has been a growing interest in using Silicon on Insulator (SOI) as a platform for integrated planar optical circuits, this is mainly due to the high quality yield volume processes demonstrated by the CMOS manufacturing industry and recent MEMS technology progress. In this work we present monolithic integration of Silicon and SiON planar lightwave circuits on a single SOI chip processed in a CMOS fabrication environment. The demonstration of a processing scheme that yields low loss waveguides for both silicon and SiON as well as efficient transition of light between the two materials is the goal of this present work. The patterning of waveguides in both silicon and SiON regions is done in a self aligned process using one lithography mask and two separate dry etch steps each highly selective to one of the two materials. The effect of a high temperature anneal on the IR absorption of SiON related N-H bond was measured using FTIR and waveguide optical loss. Up to 98% reduction in absorption is demonstrated which allows acceptable loss across the C-band. We have achieved low propagation loss, single mode, and rib waveguides for both Silicon and SiON core regions as well as low loss silicon-SiON waveguides junction. The silicon-SiON junction loss has been measured to be 0.9+/-0.1dB, only 0.3dB greater than the theoretical value determined by Fresnel's facet reflection.

A novel approach to three-dimensionally (3-D) integrate nanophotonic and electronic devices in silicon is described. The method is based on the SIMOX (Separation by Implantation of OXygen) process, to realize three-dimensionally (3-D) integrated devices in a monolithic fashion. In this approach, photonic and electronic devices are realized on vertically stacked layers of silicon, separated from each other by a dielectric layer of silicon dioxide formed through the process of oxygen implantation. Opto-electronic integration is demonstrated by realizing photonic circuits in a subterranean silicon layer and Metal-Oxide-Semiconductor (MOS) transistors on a surface layer of silicon. Optical and electronic functionalities are thus separated into two different layers of silicon, paving the way towards dense three-dimensional opto-electronic integration. This has the significant advantage that photonic devices do not consume any of the expensive silicon real estate required for CMOS circuitry. The versatility of the technique of SIMOX 3-D sculpting in obtaining complex optical circuitry is also demonstrated by synthesizing a cascaded microdisk structure that may be utilized to tailor the passband characteristics of optical filters.

In this paper we measure the efficiency of photon pair production from parametric downconversion at the photon counting level, generated in a laboratory prototype of PPLN waveguide at 1572 nm. The aim is to enhance the brightness of an heralded single photon source and to improve compactness for quantum communication applications, namely quantum key distribution. We observed a maximum of the conversion efficiency corresponding to 7.9 10⁶ photon pairs/s for a pump power of 28 μW. This value is compared with the measured pairs production in a classical experiment of difference frequency generation, realized with the same sample by analogue classical detection. We highlight the advantages of using the waveguide versus a bulk PPLN for such applications and we foresee further possible improvements by adopting waveguide in a single photon level experimental setup.

We propose a device based on self-induced phase shifting to create a non-linear optical transfer function with a single optical access. The device is designed around the Nonlinear-Optical Loop Mirror (NOLM) principle. The device is a loop formed by four SOAs with a splitter/recombiner at one of the junctions for optical access. The device also includes a mirror inside one of the SOAs such that part of the light is transmitted around the loop and part is reflected. The dimensions of formed loop are kept below 4mm (1mm/SOA) to the requirement for integration. It is assumed the loop is based on a standard ridge waveguide design with InGaAsP/InGaAs quantum wells yielding a refractive index of 3.88. Also, the width of the waveguide is kept constant at 2μm to ensure single-moded operation. We present simulations results obtained with VPITransmissionMakerTM from VPIPhotonics. The software allows the simulation of optical modules such as Lasers, SOAs, Bragg Grating. The SOA and Laser modules exploit on the Transmission Line Laser Model (TLLM) model for solving the standard laser rate equations. For the Multi-Quantum Wells (MQW) SOAs, another set of equations are used to model the effects of carriers entering and exiting the quantum wells. The model is used to explore the tunability of the design and manufacturing parameters for optimal performance of the non-linear optical loop mirror. Design parameters include the size of the loop, drive current of each SOA, position and reflectivity of the mirror, number and size of the quantum wells and separate confinement height. To provide an efficient way of comparing different values for a given parameter, three figures of merits are chosen. The first one is the input dynamic range of the device in its current configuration, which corresponds to the area of the transfer function where the input signal will experience regeneration. The second parameter is the peak to trough ratio corresponding to the maximum possible output swing i.e. the maximum point of the transfer function less its corresponding minima. The final parameter named the regeneration slope is the division of the peak to trough ration by the input dynamic range. The particularity of this loop is the mirror etched into one of the active waveguides to create self-induced phase shifts leading to non-linear transfer functions with a single optical input. Optimisation is explored for various design parameters that would need to be decided prior to manufacturing such a device. It is believed that such optimisation can provide a way to create all-optical signal processing devices created for a single application.

We present the first investigation of bright screening soliton formation in Erbium doped lithium niobate grown by the Czochrlaski technique (0.7% mol.). We analyse the formation of two-dimensional spatial soliton and study its long term stability. Measurements of photovoltaic current show that presence of erbium in the lattice cause an increase of the current density. Both dynamic of soliton formation and photovoltaic measurements indicates a lower N_A content in erbium doped samples compared to undoped samples.

We investigate the significance of secondary effects caused by free carrier accumulation and subsequent heating on the nonlinear behaviour of ultrasmall Silicon-On-Insulator ring resonators. All-optical bistability based on thermal dispersion was experimentally obtained for an input power of only 0.28mW. At higher powers, pulsating behaviour was observed which is problematic for the stability of thermal memory and switching operations. Using free carrier dispersion, we also demonstrate all-optical wavelength conversion with a pulse length of 10 ns, indicating that bitrates of 0.1 Gb/s are feasible. Also here, the presence of unstable pulsations was observed, leading to significant errors in the converted data pattern.

The spectral properties of a single-mode active microring resonator are investigated in the frame of the extended transfer matrix formalism. Spontaneous emission, looked upon as the driving source of the radiation, is described in a semi-classical way in the spectral domain. The internal and emitted fields are filtered into the resonance modes of the whole structure; the spectral density of power is described by the generalized transfer function, which contains all essential mechanisms at work in a laser oscillator: gain, losses and sources. The active zone is saturated through Amplified Spontaneous Emission, integrated over its whole spectral range. Continuously valid across threshold, the method enables one to derive in a simple way the main steady-state properties of the laser oscillation, with the pumping rate as the only external parameter. In this approach, the optical properties of the active medium (the gain, the source and the refractive index) are supposed to be uniquely determined by the steady-state value of the carrier density, obtained within the framework of the rate equation formalism and assumed uniform along the active zone.

This work analyzes a new efficient numerical algorithm for evaluating the time-domain electromagnetic (EM) field and the filtering behaviour of periodic waveguides, by reducing the number of equations to solve. The scalar Helmholtz-equation is utilized in order to determine the electric and magnetic Hertzian-potentials that represent the EM field. The principle of the method is demonstrated by a simple 2D application to a multilayer dielectric stack at optical frequencies.

This work presents two types of optical receivers with large-diameter photodiodes. Both are optoelectronic integrated circuits (OEICs) realized in 0.6μm BiCMOS Si technology integrating PIN photodiode, transimpedance amplifier (TIA) and output circuit on chip. The two circuits are an optocoupler with a photodiode diameter of 780μm and a rise- and falltime of 5ns and 4.9ns respectively at 850nm light and a plastic optical fiber (POF) receiver with a photodiode diameter of 500μm and upper -3dB cut-off frequencies of 165MHz at 660nm light and 148MHz at 850nm light. The measured rise- and falltime of the POF receiver was 1.78ns and 2.45ns at 660nm light and 1.94ns and 2.5ns at 850ns, respectively. The presented results combine the advantage of easier handling of large-diameter photodiode receivers and high performance.

Polarization conversion phenomenon in a semiconductor electrooptic polarization converter is reported by use of finite element method. The effects of various device parameters and the modulating voltage on the polarization of the TE and TM modes have been thoroughly investigated.

We propose a polymeric variable optical attenuator based on long range surface plasmon polaritons (LRSPPs) along a thin metal stripe embedded in polymers. The device is operated by controlling radiation loss of the LRSPP mode resulting from the temperature gradient of the polymer cladding caused by a heater. For guiding LRSPPs and efficient coupling of single mode fibers, gold stripes with 20-nm thickness, 4-μm width and 1-cm length are utilized. To obtain long physical lifetime, the heater is formed on the top of the polymer cladding with a 200-nm Au film which is about ten times thicker than the thin metal waveguide. The fabricated device is characterized at a wavelength of 1.55 μm, exhibiting high attenuation of less than 30 dB with the operating power of 100 mW. The fiber-to-fiber total insertion loss of 6.1 dB is achieved when using single mode fibers.

Polymers are attractive to realize integrated circuits specially because they are very simple to process and are promising for low cost devices. Moreover, beside low cost technology, the large possible range of refractive index, could lead to large scale of integration, lowering the fabrication costs. In some cases, it could be an alternative solution to semiconductor or inorganic dielectric technologies. With usual UV photolithography technology, this work shows that it is possible to perform small guides in order to provide relatively high circuit densification. The refractive index contrast, between optical core and cladding, can be as high as 0.07 instead of 0.02 for the higher contrast in silica Ge doped waveguides. Recently, this contrast has been increased to 0.11 at the wavelength of 1550nm. These materials make possible the patterning of guides having radius of curvature smaller than 200μm. Such curvatures open the way to functions based on microrings that potentially lead to compact wavelength multiplexers. With the view to control the fabrication of polymer waveguides, some features of the process are reported here. For example, shortcomings such as unsuitable film worm aspects are described and solutions are given with requirements assigned to rough materials. Mechanical and thermal properties of polymers have to be adjusted to withstand integrated circuit processing. This paper also presents results concerning the realization of integrated passive microring resonators with this technology.

We report on the design and experimental results of monolithically integrated optoelectronic devices containing distributed feedback (DFB) laser, electroabsorption modulator (EAM), and semiconductor optical amplifier (SOA). Common InGaAlAs multiple quantum well (MQW) layers are used in all device sections. The incorporation of local lateral metal gratings in the DFB section enables device fabrication by single-step epitaxial growth. The emission wavelength is λ=1.3 micrometer. More than 2 mW single-mode fiber-coupled output power as well as 10 dB/2 V static extinction ratio have been achieved. Modulation experiments clearly show 10 Gbit/s capability.

Progress in photonics by monolithic integration for higher functional density, performance and reduced cost faces challenging hurdles due to technological and functional heterogeneities. Advanced local material growth techniques are enabling concepts towards high-density photonic integration, unprecedented performance and multi-functionality and ultimately optical systems-on-a-chip. For example mode-locked laser diodes (MLLDs) are key devices for ultra-short pulse generation for all-optical Tbit/s communication networks. MLLDs suffer from material compromises and will benefit from the possibility to design the gain, absorber and passive-waveguiding sections independently. We have proposed and demonstrated the integration of a saturable absorber with a fast absorption recovery time based on an InP/InGaAsP uni-traveling-carrier structure (UTC) to achieve pulses below 1 ps with repetition rates up to 40 GHz. The use of the UTC absorber instead of the commonly employed reverse-biased gain material requires however the heterogeneous growth of multiple layer stacks on the same chip with the butt-coupled regrowth technique.Critical for the MLLD performance are the reflections and the optical coupling between the different monolithic integrated layer structures of passive, absorbing and amplifying sections. 2D FDTD simulations of the optical waveguides demonstrate that to minimize reflections an angled interface between the different structures is preferable and can lead to reflection coefficients as low as 10^-6. To obtain an angled interface we used a wet chemical etching process sequence of selective and non-selective etchants, which is sensitive to crystal orientation and yields a 55° tilted interface. In addition we can conclude from our simulations that in order to minimize both, insertion loss and reflections, a bending of the light guiding layers has to be prevented. Bendings can lead to measured losses of 5-7 dB per interface whereas correctly aligned light guiding layers results in losses of 1.5 dB and intensity reflections below 10^-5 per interface. The bendings originate from different growth rates near and far away from masked areas during regrowth due to reactants diffusion on the SiO2 mask. The bending can be minimized by optimizing the mask under etch of the SiO2 mask and low pressure MOVPE growth. We demonstrate operation of mode-locked laser diodes with an integrated UTC absorber and pulse durations below 1 ps.

This paper presents the first optical and spectroscopic characterization of zirconium based fluoride planar waveguides ZE (ZrF₄-ErF₃) and ZLE (ZrF₄-LaF₃-ErF₃) that have been fabricated by Physical Vapor Deposition (PVD) in dual evaporation configuration [1]. Transparent thin films have been obtained by adjusting vaporization temperature, composition of the ZrF₄-based glass and the LaF₃-ErF₃ batch. In order to improve resistance to moisture, a low refractive index (~1.32) KAlF₄ cladding has also been deposited. Infrared spectrum of the waveguides has confirmed the protecting role of the cladding layer for the active layer regarding hydrolysis. Luminescence measurements on waveguide samples have shown promising properties compared with the bulk samples, indicating that this system may be suitable for ceramization like in bulk configuration [2-3].

The design, fabrication technology and parameters are presented for monolithic linear 16-element IR emitter bar and the 8 x 8 stack of bars. Both types of devices are based on the Si p⁺in⁺-diodes with the 0.86 x 0.86 mm² emitting surface integrated into a single chip and operated at well above room temperatures by the contact double injection of free charge carrier. To bypass Si electronic band structure limitation, we utilized free carrier absorption as a way to monitor material below-bandgap IR thermal emission. At a device temperature T=453 K, nearly 1.0 mW output power and 420 K apparent temperature of IR (3 to 12 μkm spectral band) radiation could be achieved with ~0.8% external power efficiency and 0.1 ms rise-fall time. This represents the longer wavelengths, higher operating temperatures and output power from Si spontaneous emitters ever reported.

In this paper, we propose and analyze a versatile structure of electro-optical modulator on a polysilicon rib waveguide. The structure confines both optical field and charge carriers in a micron-size region. The optical field is confined by using a coplanar waveguide (CPW) structure. Software based on the Finite Element Method (FEM), allows a complete analysis of the distribution and penetration of the electric field (E) within the polysilicon rib waveguide. This analysis is validated by the use of Kramers-Kronig dispersion relations.

Most of the present high-speed light modulator technologies perform only binary modulation, which is not sufficient for visualization applications. A greyscale images could be obtained using temporal accumulation of binary images. This technique, known as temporal multiplexing, is applied without difficulties in applications with incoherent light (e.g. DMD video projectors). In coherent application, where the phase of the light is to take into account, temporal decomposition could introduce errors. In this paper, this point will be studied theoretically and with simulations on an optical image processor.

A VHDL-AMS model of a surface-stabilized ferroelectric liquid crystal cell is presented in this paper. The model is based on the uniform FLC theory known since 1990. Although not quantitative, this approach gives us a good idea of the behaviour of such crystals. The model will be characterized and the results will be compared. Many related phenomena (effect of the temperature, ion transport...) will be introduced to complete the behavioural description. The purpose of this work is the design of virtual prototype for a high-speed spatial light modulator.

We present a novel practical method for group delay compensation of Bragg gratings imprinted in planar waveguides for high speed DWDM systems. Although Bragg grating-based wavelength selective devices in optical fibers have reached their maturity, similar components built on the basis of planar technology are still the research issue. We analyze an integrated Mach-Zehnder interferometer-based Add-Drop multiplexer equipped with two pairs of gratings, one designed as a wavelength selective filter and the other one as a group delay compensator.

In the last years, the possibility of light generation and/or amplification in silicon, based on Raman emission, has achieved great results. However, some significant limitations, inherent to the physics of silicon, have been pointed out, too. In order to overcome these limitations, a possible option is to consider low dimensional silicon. On this line of argument, an approach based on Raman scattering in porous silicon is presented. We prove two significant advantage with respect to silicon: the broadening of spontaneous Raman emission and the tuning of the Stokes shift. Finally, we discuss about the prospect of Raman amplifier in porous silicon.

A theoretical investigation of thermo-optic effect in silicon-on-insulator rib waveguide arrays is presented. Two types of array arrangements are described, with the aim to find the configuration in which the heat is efficiently guided from the heater through the waveguide core without noticeably affecting the other adjacent waveguides. One of these array designs provides excellent thermal and optical separation between waveguides and efficient heat flow, allowing smaller switching power and faster response to be simultaneously achieved. Good thermal isolation for closely spaced SOI waveguide structures is very promising for the realization of dense photonic integrated circuits.

Silica-hafnia glass-ceramics waveguides activated by Er³⁺ ions were fabricated by sol-gel route. X ray diffraction and optical spectroscopy showed that after an adapted heat treatment, the resulting materials showed a crystalline environment. Analysis of the luminescence properties has demonstrated that erbium ions are, at least partially, trapped in a crystalline phase. Losses measurements at different wavelength highlight a very low attenuation coefficient indicating that this nanostructured material is suitable for a single band waveguide amplifier in the C band of telecommunication.

In this paper we present a general methodology for the design of resonant cavity enhanced (RCE) photodetectors based on the internal photoemission effect. In order to estimate the theoretical quantum efficiency we take advantage of the analytical formulation of the internal photoemission effect (Fowler theory), and its extension for thin films. In particular, the absorptance is numerically determined by means of an approach based on the transfer matrix method. Finally, we apply the proposed methodology to the design of a silicon RCE photodetector operating at 1.55μm, based on the internal photoemission effect at an Au-Si schottky barrier.

Liquid Crystals have many applications in photonics, but often the geometrical properties of the photonic structures give problems for controlling the alignment of the liquid crystal. We demonstrate the effect on the orientation of a nematic liquid crystal by structures etched in Silicon-on-Insulator (SOI) wafers, produced by photolithography. We characterize the alignment effect of several patterns, including configurations that allow multiple stable director orientations. Also, the influence of a surface treatment (like deposition of a monolayer on the structured surface) is discussed.

This work deals on the fabrication process of diffraction gratings made on Lithium Niobate substrates by means of focusing femtosecond laser pulses. The main optical features of these photonic structures are presented in this paper. As it was expected the relief gratings showed high diffraction efficiency in accordance to the index modulated profile of the crystal-air border resulting in this kind of diffractive structure. On the other hand, for the inside grating a higher diffraction efficiency for the first orders were found, however the overall diffraction efficiency was found to be similar to that obtained for the ablation structures made in this work; this result suggests that the index increment in the inside grooves should be very important. The thermal stability of these structures is also studied and discussed in this paper. It is found that for the relief gratings the diffraction efficiency is temperature independent up to 400°C degrees, while for the inside gratings a slight decrease on diffraction efficiency was observed after making a thermal annealing at 400°C during two hours. The grating fabrication method presented in this work can be a powerful tool for development of several photonic devices made inside/on Lithium Niobate by using femtosecond laser writing by means of the one step process.

In this paper we report on a multi-chip color variable LED linear module with new concepts of optics design, free encapsulation, mechanical assembly and color control. Six dice are mounted close together on a substrate and combined with a faceted dielectric collimator to shape the light output. To achieve a very slim optical collimator (with minimal thickness), we combine a mechanical reflector with a total intern reflection (TIR) collimator. One of the bottlenecks in LED module design is the very high coefficient of thermal expansion (CTE) for organic optical materials (encapsulant). This material is needed to make good optical contact between LED-chip and surrounding optical system. Therefore, it is important that the design can handle large volume changes of the encapsulant during LED operation whilst maintaining good and stable optical performance. Furthermore, the encapsulant needs to be soft to avoid high stresses on fragile components (e.g. bond wires). These problems are solved in our module. To overcome variations in the color of the light output due to temperature changes and ageing, this module is equipped with a temperature and a light sensor. The signals of these sensors are supplied to a color control algorithm, which changes the power levels to each LED color in the appropriate way. This algorithm is capable of reducing the color error Δu'v' from 0.022 (in open loop) to 0.005 for a temperature change of 50 degrees Celsius. Cooling of the linear module is based on natural convection. The operation temperature of the housing is about 300C above ambient temperature. Variable material combinations in the thermal path from the junction to the house have been modeled in order to minimize the internal thermal resistance. A prototype is made and optical performance is measured as well. The optical efficiency of the module is about 75%.