This PDF file contains the front matter associated with SPIE Proceedings Volume 6896, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

We discuss realization, properties and performance of the adaptive finite element approach to the design of optical waveguides. Central issues like the construction of higher-order vectorial finite elements, local error estimation, automatic and adaptive grid refinement, transparent boundary conditions and fast linear system solution by domain decomposition techniques will be discussed.

We analyze coupled optical defect cavities realized in finite one-dimensional Photonic Crystals. Viewing these as open systems where waves are permitted to leave the structures, one obtains eigenvalue problems for complex frequencies (eigenvalues) and Quasi-Normal-Modes (eigenfunctions). Single defect structures (photonic crystal atoms) can be viewed as elementary building blocks for multiple-defect structures (photonic crystal molecules) with more complex functionality. The QNM description links the resonant behavior of individual PC atoms to the properties of the PC molecules via eigenfrequency splitting. A variational principle for QNMs permits to predict the eigenfield and the complex eigenvalues in PC molecules starting with a field template incorporating the relevant QNMs of the PC atoms. Further, both the field representation and the resonant spectral transmission close to these resonances are obtained from a variational formulation of the transmittance problem using a template with the most relevant QNMs. The method applies to both symmetric and nonsymmetric single and multiple cavity structures with weak or strong coupling between the defects.

We derive a comprehensive coupled-mode theory, including resonant vertical radiation, for the analysis of non-periodic grating circular Bragg lasers. We analyze the threshold levels and modal properties of such lasers employing mixed-order Bragg gratings to achieve both strong confinement and efficient vertical emission. By reducing the threshold gain and maximizing the emission efficiency, we suggest an optimal design for the circular Bragg microdisk lasers which indicates low-threshold and high-efficiency operation is possible.

We investigate the thermal antenna behavior of emissive/absorptive substrates coated by passive optical multilayer systems that contain negative refractive index metamaterials (NIM). Spectral and angular distributions of the thermal radiation emittance for periodic defect-containing multilayer with NIM is addressed. We analyze realistic finite structures and took into account dispersion and losses in the NIM part. The application of NIM-containing 1D structures offers new degrees of freedom for the design, thus opening a path to obtain spectrally and spatially selective thermal emitters that could lead to improvements in the existing systems for thermal radiation control.

In the mid 80's, the doping of optical fiber's core with rare earth atoms has been a major breakthrough in the field of optical telecommunications since it allowed the realization of in-line optical amplifiers. However, erbium-doped fiber amplifiers are a few meters long and a huge effort has been made in order to realize compact and efficient active devices based on rare-earth-doped waveguides. For this purpose the use of phosphate glasses instead of silicate ones has been investigated because they allow a better solubility of the inserted rare earths. In this paper we present the realization of a hybrid Neodymium-doped passively Q-switched waveguide laser made by ion exchange on a Schott IOG-1 phosphate laser glass combined with the deposition of a BDN saturable absorber diluted in a cellulose acetate polymer cladding. In a first step, we present the CW operation of the laser with an undoped cladding. We show that for a 3.5-μm wide, 1.4-cm long waveguide realized by a silver-sodium ion exchange, a 6 mW output has been achieved by creating a Fabry-Perot cavity with dielectric multilayers mirrors sticked to the chip facets. Then, the characterizations performed on the BDN doped layers are presented. It is shown that a proper selection of the hybrid guiding structure and saturable absorber concentration entail an excess absorption ranging from 1 to 10 dB/cm at zero flux. Finally, results on Q-switched behavior are presented. Optical pulse duration of 2-ns (FWHM) was obtained with repetition rates ranging from 5 to around 50 kHz for a 22 W pulse peak power.

Fabrication results are reported for making optical gratings in chalcogenide glasses. Two approaches are being investigated: 1) thermal nanoimprinting of the glass using a mold master, and 2) direct patterning of the chalcogenide glass using a combination of electron beam lithography (EBL) and reactive ion etching (RIE). Preliminary results are presented for the nanoimprint and EBL experiments. The nanoimprint results show very smooth sidewalls.

Ion-exchange technology on glass has been successfully used for more than twenty years to manufacture dependable and low cost integrated optics active and passive devices on silicate or phosphate glasses substrates in the telecommunication wavelengths operation range (from λ = 0.8 to 1.7 μm). However, the recent developments of integrated optics instruments for astronomical interferometers or biological sensors have lead to an increase of the devices operation range towards the mid-infrared. For these reasons, we present in this paper the realization of both surface and buried waveguides by means of ion-exchange on a glass which is transparent until λ = 5 μm. In this study, the choice of germanate glass BGA-G115 from Kigre Inc. has been made because of both its similarity with silicate glass, its content of Na⁺ ions and its excellent transparency in the considered operation range. A complete study of the silver ion diffusion on this new glass matrix has been performed allowing the determination of silver and sodium ion-diffusion coefficients at working temperature and silver concentration. Using theses data, simulations have shown that an ion-exchange of 90 min in a 0.03AgNO_3-0.97NaNO₃ molten salt at a temperature of 330°C can lead to the realization of surface single mode channel waveguides at either λ = 1.55 μm or λ = 3.39 μm depending on the diffusion window width. To demonstrate channel waveguides on BGA-G115, a specific technological process based on the deposition of a polycrystalline silicon masking layer has been implemented. Single-mode channel waveguides, with a 2.5 μm diffusion window width, have thus been realized and characterized at the wavelength of 1.55 m. Modal size has been measured to be 10 μm ± 1 μm x 7 μm ± 1 μm for propagation losses of 1.2 dB/cm ± 0.5 dB/cm for a 2 cm ± 0.1 cm long device. As for buried waveguides, their feasibility has been demonstrated on multimode ones where a burying depth of 25 μm ± 2 μm has been measured.

Ultra-small silicon-based photonic-crystal ring resonators (PCRRs), both passive and active, will be key contributors to the emerging low-power nanophotonic technology. We have modeled and simulated the diameter-dependent loss, Q, and FSR of such PCRRs and find a 0.02 dB "intrinsic" loss that is independent of diameter, unlike the ~1/D loss of micro-strip resonators. Close to 100% drop efficiency at the drop channel of 1557.5nm was obtained by design with a high spectral selectivity of Q greater than 1319 in the single-ring PCRR-based add-drop filters with ring radius of 1.2 μm. Ultra-compact polymer modulators were proposed and simulated, based on the hybrid integration of functional polymer materials with Si based PCRRs, which can lead to high speed modulators, suitable for photonic integration and RF photonics.

Optical waveguide adiabatic tapers enable low-loss connections between devices with dissimilar mode profiles. Common examples are semiconductor lasers, single-mode optical fibers and planar waveguides. Planar lithographic processes can easily create tapers in the plane but out-of-plane, symmetric tapers are difficult. Three-dimensional direct-write lithography into photopolymer naturally creates radially-symmetric waveguides when the motion is parallel to the optical axis of the writing focus, but absorption in the photopolymer inevitably attenuates the index with depth. We demonstrate that material absorption, translation speed and/or writing power can be used to control this taper, providing an inexpensive mode coupler for integrated optical systems.

High efficiency diffractive light incouplers for light guides are described. We show that it is possible to couple white LED light into light guide with good white balance and high incoupling efficiency by using binary radial grating structures. Furthermore, a double-sided perpendicularly oriented grating configuration at opposite sides of a thin light guide is shown to provide significantly higher overall efficiency than one sided grating. This is a configuration that can be used in many mobile backlighting applications. In addition, a double grooved binary grating is introduced which can produce theoretically up to 100% incoupling efficiencies by using monochromatic light sources. This high efficiency is comparable to the slanted gratings. Replication techniques and incoupling efficiency simulations for slanted gratings are introduced by using a high refractive index material (n=1.71@525 nm).

A new type of a resonator defined by two or more mode-converting gratings in a waveguide is proposed and analyzed. It is shown that the proposed structure can exhibit narrow resonances similar to Fabry-Perot cavities but has an advantage of being a four-port device and thus is capable of serving as an add-drop filter in various integrated optical circuits.

We demonstrate the use of deep ultraviolet (DUV) reduction photolithography, today's foremost commercial nanofabrication technology, in the patterning of integrated nanophotonic filters based on etched channel waveguide gratings. DUV photolithographic fabrication is seen to enable control over individual grating lines at the level of nanometers enabling spectral engineering of the filter function in unprecedented fashion. Novel filter apodization approaches are introduced and demonstrated that uniquely leverage DUV nanofabrication power. The demonstrated filter functions are highly relevant for coarse wavelength division multiplexing and fiber to the premise applications.

We propose an original diffraction grating demultiplexer (spectrometer) device with a very small footprint, designed for the silicon-on-insulator waveguide platform. The wavelength dispersive properties are provided by a second-order diffraction grating lithographically defined and etched in the sidewall of a curved Si waveguide. The grating is blazed to maximize the -1^st order diffraction efficiency. The diffracted light is coupled into the silicon slab waveguide via an impedance matching sub-wavelength grating (SWG) graded-index (GRIN) anti-reflective interface. The waveguide is curved in order to focus the light onto the Rowland circle, where different wavelengths are intercepted by different output waveguides. The phase errors were substantially reduced using an apodized design with a chirped grating pitch, which assures a constant effective index along the grating length. The simulated crosstalk is -30 dB. The device has 15 channels with a spacing of 25 nm, thus a broadband operational bandwidth of 375 nm. Its performance approaches the diffraction limit. The device layout size is 90 μm × 50 μm, which is the smallest footprint yet reported for a mux/dmux device of a similar performance.

Chirped Bragg gratings can be utilized in various application regions due to their characteristic spectral and group delay responses. Chirped Bragg gratings based on the planar waveguide technology can present several advantages over chirped fiber Bragg gratings. We have proposed and demonstrated that the chirp characteristics of waveguide Bragg grating (WBG) devices can be tailored by adopting specifically tapered core profiles. On the ground of our analytical and experimental results, we established the dependence of the modal effective index on the core width. Using the relationship, we designed and fabricated polymeric WBG devices with precisely controlled linear chirp parameters. Then, one of the fabricated WBG device was packaged and applied to tunable dispersion compensation (TDC) for 40-Gbps optical signal transmission. It was ascertained that the optical signal quality was significantly improved by tuning the operation condition of the packaged TDC module.

We present results of our work aiming towards the amplification of surface plasmon-polariton modes in long-range waveguide structures. Such structures are formed by a thin gold stripe sitting on a silicon dioxide substrate. The active medium consists of organic-dye molecules with emission wavelengths in the near infra-red region, dissolved in dimethyl sulfoxide and ethylene glycol. The active solution is index matched to the substrate and serves as upper cladding, forming a symmetric waveguide structure. The large gain coefficients that can be obtained with organic dyes together with the low attenuation coefficients offered by symmetric long-range surface plasmo-polariton waveguides make these structures good candidates to achieve net amplification in the near infra-red region.

The authors show that the incorporation of gain media in only a selected device area can annul the effect of material loss, and enhance the performance of loss-limited plasmonic devices. In addition, they demonstrate that optical gain provides a mechanism for on/off switching in metal-dielectric-metal (MDM) plasmonic waveguides. The proposed gain-assisted plasmonic switch consists of a subwavelength MDM plasmonic waveguide side-coupled to a cavity filled with semiconductor material. In the absence of optical gain in the semiconductor material filling the cavity, an incident optical wave in the plasmonic waveguide remains essentially undisturbed by the presence of the cavity. Thus, there is almost complete transmission of the incident optical wave through the plasmonic waveguide. In contrast, in the presence of optical gain in the semiconductor material filling the cavity, the incident optical wave is completely reflected. They show that the principle of operation of such gain-assisted plasmonic devices can be explained using a temporal coupled-mode theory. They also show that the required gain coefficients are within the limits of currently available semiconductor-based optical gain media.

Channel plasmon polaritons (CPPs) propagating along the bottom of subwavelength grooves cut into a metal surface were recently shown to exhibit strong confinement combined with low propagation loss, a feature that makes this guiding configuration very promising for the realisation of ultracompact photonic components. Here, the results of our investigations of CPP guiding by V-grooves cut into gold are presented, demonstrating efficient waveguide-ring (WR) resonator-based plasmonic components (including WR resonators and a WR resonator-based add-drop multiplexer). The CPP waveguides represent 0.5-μm-wide and 1.3-μm-deep V-grooves in gold, which are combined with 5- and 10-μm-radius ring resonators. The CPP-based components are characterized in the wavelength range of 1425-1620 nm by use of near-field optical microscopy, exhibiting the wavelength selectivity of ~40 nm.

Optical ring resonators have been investigated for a number of interesting devices, including dye lasers and sensors. However, in general, these devices can only operate on liquid samples with a low refractive index (RI) because the whispering gallery modes (WGMs) are bound in the resonator through total internal reflection at the resonator/sample boundary. We recently introduced a new opto-fluidic ring resonator (OFRR) that uses a thin-walled capillary to deliver the sample through an array of ring resonators contained within the circular cross-section of the capillary. Thus, in the OFRR, the WGM is bound at the outer surface while the evanescent field interacts with the sample at the inner surface. Therefore, the OFRR can operate on samples of lower and higher RI than the capillary material. This unique feature, in combination with the OFRR's practical fluidic delivery design and its simplicity make it an attractive opto-fluidic device for sensors, lasers, and other applications. We analyze the OFRR's capability to support WGMs that are excited externally through fiber tapers and that interact with the sample inside. Using a quantum mechanical analogy, we show that for liquid cores with a higher RI than the capillary material, two coupled propagating waves exist that enable WGMs inside the liquid core to be excited by a fiber taper outside the OFRR, across a few microns. We experimentally verify our analysis by demonstrating refractometric sensors and dye lasers with core RIs lower and higher than the capillary.

Recently, low threshold Raman silicon lasers based on ring resonator architecture have been demonstrated. One of the key elements of the laser cavity is the directional coupler that couples both pump and signal light in and out of the ring resonator from the bus waveguide. The coupling coefficients are crucial for achieving desired laser performance. In this paper, we report design, fabrication, and characterization of tunable silicon ring resonators for Raman laser and amplifier applications. By employing a tunable coupler, the coupling coefficients for both pump and signal wavelength can be tailored to their optimal values after the fabrication, which significantly increases the processing tolerance and improves the device performance.

We summarize the results of a European Project entitled WAPITI (Waferbonding and Active Passive Integration Technology and Implementation) dealing with the fabrication and investigation of active/passive vertically coupled ring resonators, wafer bonded on GaAs, and based on full wafer technology. The concept allows for the integration of an active ring laser vertically coupled to a transparent bus waveguide. All necessary layers are grown in a single epitaxial run so that the critical coupling gap can be precisely controlled with the high degree of accuracy of epitaxial growth. One key challenge of the project was to establish a reliable wafer bonding technique using BCB as an intermediate layer. In intensive tests we investigated and quantified the effect of unavoidable shrinkage of the BCB on the overall device performance. Results on cw-operation, low threshold currents of about 8 mA, high side-mode suppression ratios in the range of 40 dB and large signal modulation bandwidths of up to 5 GHz for a radius of 40 μm shows the viability of the integration process.

We numerically demonstrate the feasibility of constructing an all-optical pulse restorer by using a microresonator structure with Kerr nonlinearity. We obtain a clear nonlinear power transfer curve suitable for all-optical regeneration (reshaping) in the frequency and the time domains. The fully integrated device is based on 2 cascaded sets of finite chains of 3 coupled nonlinear identical microring resonators side coupled with 3 straight waveguides. The microrings are constituted by the same instantaneous, dispersive, local Kerr material. The first set suppresses the noise in "0" and the second limits the amplitude fluctuations in "1" of return-to-zero optical data streams. For a device made in p-toluene sulphonate (PTS) with n₂ = 2.2×10^-12 cm²/W with linear losses α = -5 dB/cm and nonlinear losses α₂ = 0.5 cm/GW and considering amplitude, jitter and width fluctuations we evaluate an amplitude Q-factor improvement of 4.94 dB for a data rate of 40 Gb/s and input intensity n₂I₀ = 5 × 10^-4. Since we take advantage from field enhancement at resonance, this integrated reshaper could be much smaller than other gates based on nonlinear fibers or waveguides.

Optimum combination of light source and medium (optical fiber) for radio-over-fiber application in home optical network was investigated. Japan National Television System Committee (NTSC-J) signal was employed to study the spectrum and the movie quality in different multi-mode fiber link. Noise in glass-based multi-fiber link was lowered by switching the light source from a Fabry-Perot (FP) to a vertical cavity surface-emitting laser (VCSEL). A graded-index plastic optical fiber (GIPOF) link performed a low-noise transmission using FP laser diode. The results supported the GIPOF link to be a good low-cost analog optical link solution using FP laser diode and no lens.

Recent developments in the short distance communication have made polymer optical fibers (POF) an attractive product in the high speed data communication market. The requirement of a large bandwidth, low cost, light weight and flexibility in installation have placed them over the copper cables especially in applications like home networking and automotives. Since POFs are large core multimoded fibers, their band width is limited by intermodal dispersion. This confines POFs application to low data rate short distance communications. Restrictive mode launchers (RML) and higher order mode strippers placed in the data link helps to reduce the intermodal dispersion. The techniques used to implement these signal conditioners should be simple and cost effective to keep POFs attractive in the short distance communication. In this paper we explore the possibility of integrating the RML and mode stripping elements in the transmitter and receiver package itself. The pre-designed optical signal conditioning elements are projected to get molded in the plastic packages and are fiber plug in modules. This connector less package design, universal to any light source proposes to enhance the data rate and is widely manufacturable at an ease of installation and low cost.

A novel integrated optical modulator based on electrooptical control of Bragg gratings has been developed and fabricated. The modulator can provide both the shift of the central wavelength and the change of a shape of the spectral response of Bragg gratings. The frequency modulation (FSK) of optical signals with frequency deviation of 25 GHz was experimentally demonstrated using this modulator. It is suggested not only central wavelength, but the optical spectrum shape can be used for modulation of optical signals with information content. A novel type of optical modulators will provide addition flexibility and possibility of using FSK formats in combination with optical spectral code division multi access (OCDMA) and gives an opportunity of new network architectures with simple optical processing on the level of addressing and routing.

Silicon is excellent material for realizing compact nanophotonic ICs operating at wavelengths in the telecom range. Moreover, the desired circuits can be realized with the most advanced equipment available, used also for the fabrication of high-end electronic circuits. Efficient light emission and amplification directly from silicon remains a bottleneck however. Therefore, we developed an alternative approach, based on the heterogeneous integration of III-V epitaxial material and silicon nanophotonic circuits. Following fabrication and planarization of the latter, small unprocessed dies of InP-based epitaxial material are bonded on top. Next, the substrate of these dies is removed down to an etch stop layer. Finally the desired active optoelectronic devices are processed in the remaining III-V layers using waferscale processes. The critical alignment between the sources and the underlying nanophotonic circuits is ensured through accurate lithography. In this paper we review some recent devices fabricated through this integration process.

The GaP-based dilute nitride Ga(NAsP) reveals a direct band gap and first laser device operation based on GaP substrate have been demonstrated recently. Since the lattice mismatch between GaP and Si is very small and the defect free deposition of thick GaP/Ga(NP) sequences on off-oriented Si substrate have been reported in literature, the epitaxial transfer of this novel direct band gap material Ga(NAsP) on Si substrate should allow for the monolithic integration of laser diodes on Si microprocessors. The present study introduces a nucleation scheme of GaP on exact oriented (001) Si substrate by metal organic vapour phase epitaxy (MOVPE) to achieve this goal. Appling an optimized annealing procedure to (001) Si substrates with a slight off-orientation towards (see manuscript) direction leads to a Si surface, where step-doubling has set in and bi-atomic terraces are formed. Even though mono-atomic terraces are still present in low density, an optimized GaP nucleation procedure ensures self-annihilation of all present antiphase domains (APDs) and reveals an antiphase disorder free III/V film on Si after the deposition of about 50nm of GaP. This ideal nucleation layer together with a precise strain-management allows for the deposition of Ga(NAsP)/(BGa)(AsP) multi-quantum-well (MQW) heterostructures embedded in 1μm thick (BGa)P layers on Si substrate. Structural investigations using X-ray diffraction (XRD) and transmission electron microscopy (TEM) prove a high crystal quality and abrupt heterointerfaces. This monolithic integration concept of the GaP-based laser material on exact oriented (001) Si substrates enables the integration of optoelectronic devices into the standard CMOS process.

We demonstrate Si-CMOS-compatible lift-off fabrication of chalcogenide glass waveguides monolithically integrated on a silicon platform. As a novel route of glass film patterning, lift-off allows several benefits: leverage with Si-CMOS process compatibility; ability to fabricate single-mode waveguides with core sizes down to submicron range; reduced sidewall roughness; and wide applicability to other non-silica glass compositions. High-index-contrast (HIC) single-mode strip waveguides have been fabricated with from several glass target compositions including Ge₂₃Sb₇S₇₀, As₂S₃, As₃₆Ge₆S₅₈, As₃₆Sb₆S₅₈ and TeO₂. We measured Ge-Sb-S waveguides with low loss and excellent wafer-scale uniformity. We have experimentally demonstrated propagation loss reduction via graded-index (GRIN) cladding layers in HIC glass waveguides. These efforts have shown that scattering loss arising from sidewall roughness can be significantly reduced without compromising the high-index-contrast condition by inserting thin GRIN cladding layers with refractive indices intermediate between the core and topmost cover of a strip waveguide.

In this paper, we review the status of monolithic and hybrid integration of planar lightwave circuits (PLCs). Building blocks needed for system integration based on polymeric materials, III-V semiconductor materials, LiNbO₃ and SOI on Silicon are summarized with pros and cons. Due to the maturity of silicon CMOS technology, silicon becomes the platform of choice for optical application specific integrated circuits (OASICs). However, the indirect bandgap of silicon makes the formation of electrically pumped silicon laser a remote plausibility which requires hybrid integration of laser sources made out of III-V compound semicouductor.

Photonic microring resonators have great potential in the application of highly sensitive label-free biosensors and detection of high-frequency ultrasound due to high Q-factor resonances. Design consideration, device fabrication techniques, experimental results are report in this paper.

In this paper we report on an integrated spectrometer device, fabricated in epoxy resist (SU-8) on silicon, designed for Raman spectroscopy and direct coupling to a CCD element. Furthermore a nanostructured surface is prepared on a gold coated silicon chip to enhance the Raman signal. We show examples of low resolution Surface Enhanced Raman Spectra (SERS) recorded with this chip and provide an outlook on the future possibilities. Traditional optical detection in Lab-on-Chip devices often requires sample pretreatment including chemical reactions in order to identify and detect a certain substance (e.g. attachment of a fluorescent marker). The basic idea in bringing Raman spectroscopy to the chip is to avoid these chemical reactions and directly enable identification of the substance by its Raman spectrum. Two different methods were used to prepare the nanostructured surfaces. The first method is based on an aqueous suspension of gold nanoparticles and polystyrene beads deposited on a gold surface. The suspension was dried and the polystyrene beads were removed using an appropriate solvent (methane dichloride). The second approach includes gold coated random silicon nanostructures so-called "black silicon". The surfaces were characterized using a commercial Raman spectrometer and the enhancement factor was found to be strongly dependant on the concentration on the sample surface. The surface was impregnated with a droplet (10 μl, 100 μM) of Rhodamin 6G and Nileblue respectively. Using the on-chip spectrometer we have recorded surface enhanced Raman spectra of Nileblue and Rhodamin 6G respectively. The results show that these systems are suitable for low cost extremely compact Raman sensors with possible applications reaching from process monitoring to homeland security and point of care devices.

A rapid, label-free on-line virus detection method has been developed based on opto-fluidic ring resonator (OFRR). The OFRR employs a fused silica capillary with a diameter around 100 μm. The circular cross section of the capillary forms the ring resonator that supports the whispering gallery modes (WGMs). The OFRR wall is only a few micrometers. Thus, the evanescent field of the WGMs extends into the core and interacts with the sample flowing in the core. The WGM spectral position shifts in response to the binding of biomolecules to the OFRR inner surface, providing quantitative and kinetic information about the biomolecule interaction. In this work, M13 filamentous phage and anti-M13 antibody are chosen as a model system to demonstrate the detection and quantification of virus in liquid samples. Anti-M13 antibodies are first covalently attached on the aminosilane coated OFRR surface to provide a bioselective layer. The detection is then performed when the virus concentration varies from 10¹¹ pfu/mL down to 10³ pfu/mL. Our experimental results show that the OFRR is capable of detecting M13 at a concentration as low as 1000 pfu/mL. Control experiments are carried out to show the specificity of the detection. A theoretical model is developed to analyze the experimental results. The OFRR are advantageous in virus detection, as it integrates the ring resonator with fluidic channels and provides continuous on-line monitoring capability. It also has great potential for sensitive, rapid, and low-cost micro total analysis devices for biomolecule detection.

This article presents recent advances in scattering-type near field optical scanning microscopy used as a powerful characterization tool for integrated optics. By significant examples, it is shown that this specific probe microscopy based on an Atomic Force Microscope setup with optical heterodyne detection functionalities allows for in situ quantitative study of the complex field propagating in compact silicon on insulator photonic structures (single channel waveguides, MMI splitters and microdisk resonators).

This paper deals with a new spectrograph on integrated optics. It is composed of an Y-junction where the two junction arms are guided in a loop structure in order to obtain an interference pattern. The measurement of this intensity distribution gives access to the optical spectrum source after a Inverse Fourier Transform. To measure it, we use the property of the loop composed of a bent waveguide which is a leaky structure. Depending on the radius of the bent waveguide, a part of the light leaks from the waveguide to outside. The radiated power, proportional to the intensity in the waveguide, is coupled into a plan waveguide set near the bent waveguide. Indeed the two structures are separated by a gap which changes along the periphery of the loop. This structure enables both to control the leaking light part and to confine in the plan waveguide the propagation of the radiated field. Thereby, the radiated intensity is measured at a peculiar distance of the loop on a perpendicular plan to the input waveguide. So, the interference pattern measured is magnified by the ratio of the plan waveguide length over the loop radius, allowing to use a commercial photodetectors array to sufficiently sample the interference pattern. The spectrum is finally obtained operating a Discrete Fourier Transform. The device modelization is divided in two parts. The first part describes the coupling between the bent and the plan waveguide modelised by a modal method based on a Fourier series expansion (RCWA) combined with an exponential conformal mapping in order to simulate the electromagnetic field near the loop. The second part describes the Helmholtz-Kirchhoff theorem to simulate the far-electromagnetic field. From the interference pattern modelized, the spectrum of the signal is then calculated. A demonstrator in integrated optics on glass is being developed.

A novel integrated optical component useful for two-species detection, particle velocity measurement and cell-sorting in lab-on-a-chip devices is described. The component consists of dual waveguides that can simultaneously deliver light of two wavelengths to two fixed points in a microchannel. Labeled cells in the channel can be detected by laser-induced fluorescence stimulated by either wavelength or their velocities determined by measuring the time between peaks in the captured signals. The properties of the integrated optical component are determined by simulations and measurements and the measurement of velocities of fluorescent particles in pressure-driven flows is demonstrated.

Many applications and related studies of solar energy have been focused on guiding sunlight into indoor for illumination purposes. To approach the objective, one of the high efficient solar concentrator is base on cassegrain construction. However, exposure of UV in sunlight has been proved to be hazardous to human, and rich heat content of IR degrades illumination quality. In order to solve the two problems, we develop an innovative cassegrain solar concentrator system utilizing the theory of chromatic aberration by a chromatic lens to reduce UV and IR. A dispersion model to consider the impact of the chromatic lens and a guiding fiber is also proposed. In the result, the system can filter out the UV completely and half of the IR. Further, the chromaticity coordinates of collected light for illumination is almost equal to sunlight, and the color difference is so small that it appears equal to the human eye.

Recently, many researchers have tried to design a system for indoor illumination because the benefits of solar systems. A simple parabolic reflector is often used to collect sunlight but the efficiency is poor when sunlight isn't incident normally. Therefore, an accurate machine to track sun has to be used. In order to get better tolerance, a light pipe based solar concentrator (LPBSC) which comprises a parabolic reflector and a hollow reflective light pipe is proposed. We develop a math model which combines the reflection times of sunlight in light pipe and the candela data of parabolic reflector to analyze the efficiency. And then, straight light pipe is replaced by tapered light pipe to improve the tolerance. Optical simulation software, TracePro, and mathematical software, MATLAB, are used to prove the model is correct and feasible. In the results, LPBSC can improve the tolerance to get good efficiency.

The utilization of sunlight is very helpful to saving resources. Different approaches were used for that purpose, but the most of these systems only collect the light of some area of building and illuminate the room near window. Therefore, the primary idea of this paper is to collect large area of sunlight and convert planer light to parallel linear light so it could be guided to the deeper room. A "small unit" which could condense light is designed, and after combining, they could convert the planer light into the parallel linear light beam for the deeper room. Besides, we develop a mathematical model to describe the parallelism of the output light of the unit. OSLO is used to verify the model of the unit, and TracePro is used to verify the efficiency of the system.

Due to the idea of everlasting green architecture, it is of increasing importance to guild natural light into indoors. The advantages are multifold - to have better color rendering index, excellent energy savings from environments viewpoints and make humans more healthy, etc. Our search is to design an innovative structure, to convert outdoor sun light impinges on larger surfaces, into near linear light beam sources, later convert this light beam into near point sources which enters the indoor spaces then can be used as lighting sources indoors. We are not involved with the opto-electrical transformation, to the guild light into to the building, to perform the illumination, as well as the imaging function. Because non-imaging optics, well known for apply to the solar concentrators, that can use non-imaging structures to fulfill our needs, which can also be used as energy collectors in solar energy devices. Here, we have designed a pair of large and small parabolic reflector, which can be used to collect daylight and change area from large to small. Then we make a light-guide system that is been designed by us use of this parabolic reflector to guide the collection light, can pick up the performance for large surface source change to near linear source and a larger collection area.

Microring resonators are promising candidates for photonic signal processing applications. However, almost all resonators that have been reported so far use directional couplers or 2×2 multimode interference (MMI) couplers as the coupling element between the ring and the bus waveguides. In this paper, instead of using 2×2 couplers, novel structures for microring resonators based on 3×3 MMI couplers are proposed. The characteristics of the device are derived using the modal propagation method. The device parameters are optimized by using numerical methods. Optical switches and filters using Silicon on Insulator (SOI) then have been designed and analyzed. This device can become a new basic component for further applications in optical signal processing. The paper concludes with some further examples of photonic signal processing circuits based on MMI couplers.

The radix 5 based system employs five separate characters that have no semantic meaning except not representing the other characters. Traditional literature has a random string of binary sequential characters as being "less patterned" than non-random sequential strings. A non-random string of characters will be able to compress, were as a random string of characters will not be able to compress. This study has found that a radix 5 based character length allows for equal compression of random and non-random sequential strings. This has important aspects to information tranmission and storage.

Optoelectronic oscillators have been studied since many years now, their high spectral purity being one of their most interesting quality for photonics signal processing, communication or radio over fiber systems. One part of the structure is a long fiber optic feedback loop acting as a delay line. Different techniques have been introduced such as multiple loops in order to get very narrow spectral lines and large mode spacing. One of the problems due to long fiber loops is the size and the requirement of temperature control. In order to go toward integrated solutions it is also possible to introduce optical resonators instead of a delay line structure (as for classical electronic oscillators). But such resonators should present very high quality factor. In this paper we demonstrate solutions using resonators based on polymer materials such as PMMA-DCM. Structures such as micro-rings, micro-disks or stadium-shaped resonator have been realized at the laboratory. Quality factor of 6000 have already been achieved leading to an equivalent fiber loop of 19 m for an oscillator at 10 GHz. But it has been already theoretically proved that quality factor greater than one thousand hundred could be obtained. These resonators can be directly implemented with Mach-Zehnder optical modulators based on electro-optic polymer such as PMMA-DR1 leading to integrated solutions. And in the future it should be also possible to add a laser made with polymer material, with a structure as stadium-shape polymer micro-laser. The fully integrated photonic chip is not so far. The last important function to be implemented is the tuning of the oscillation frequency.

The paper presents the results concerning with beam quality improvement by concurrently modifying the index and the doping profile in LMA fibers. Further, the mode effective area is maximized by providing a passive ring in the cladding. The influence of the index profile over the distribution of the optical power among various modes is presented. The aim is to favor the fundamental mode by concurrently rejecting the higher modes, i.e. generating a quality beam. Simulation results and manufacturer's tests led to a novel design which consists in providing a passive ring in the cladding. That was of great help in rejecting the higher-order modes, and it can be applied to a large range of LMA fibers. The cladding ring procedure is of interest for Liekki, and it is very likely that it would be put into production.