This PDF file contains the front matter associated with SPIE Proceedings Volume 7604, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Photonic integration technologies, which have been developed since the deployment of optical communication, are essential for increasing network capacity at a low cost and with efficient power consumption. This paper reviews recent progress on photonic integrated devices for 100G-class long-distance transmission technologies with advanced modulation formats.

Silicon oxynitride (SiON) is a highly attractive material for integrated optics, due to its excellent properties such as high transparency, adjustable refractive index and good stability. In general, the growth of SiON layers by plasma enhanced chemical vapor deposition (PECVD) is followed by a high temperature annealing step in order to remove hydrogen and to achieve low propagation losses in the 1.5-μm wavelength window. The high annealing temperature (>1100°C) required for sufficient hydrogen removal induces, however, side effects like significant inter-layer diffusion and micro-cracks resulting in deterioration of the device performance. In this paper compositional and optical properties of as-deposited and annealed boron (B) and phosphorous (P) doped SiON layers were investigated. The doped layers have been fabricated by introducing PH₃ and B₂H₆ gaseous precursors into the PECVD process. Hydrogen contents of the samples have been studied by Fourier transform infrared (FTIR) spectroscopy. Compared to undoped film, a 50% reduction of the hydrogen content was measured in as-deposited P-doped SiON layers. Further reduction down to the FTIR detection limit was achieved upon annealing at temperatures as low as 700°C. Besides hydrogen reduction the reflow properties of B and P doped SiON are also highly relevant for the realization of low-loss integrated optical circuits. Reactively ion etched channel waveguides have been reflown applying a temperature of 900°C. Significant reduction of the sidewall roughness has been confirmed by scanning electron microscopy.

Recent advances in the production of high-purity synthetic diamonds have made diamond an accessible host material for applications in present and future optoelectronic and photonic devices. We have developed a scalable process for fabricating photonic devices in diamond using reactive ion etching (RIE) and photolithography as well as using ion implantation to provide vertical confinement. Applying this we have demonstrated a few-moded waveguide with a large cross section for easier coupling to optical fibre. We present our work towards in-plane coupling to diamond waveguides and consequently characterisation of these waveguides. We also examine the application of diamond waveguides to other photonic applications for achieving light confinement in a subwavelength cavity site using a slot-waveguide design. Such cavities may be used to enhance photon-emission properties of a built-in diamond colour centre and to achieve strong light-matter interactions on the single-quantum level necessary for quantum information technology. Using single cavities as building block, we also show that these structures can be suitably coupled to form one-dimensional coupled-resonator array.

In the present paper we focus on the fabrication of waveguides which will be able to work in the large infrared window [6-20μm], compatible with the ESA requirements in the framework of the detection of Exo-solar planets by nulling interferometry. The first step in the fabrication of such components is the realization of planar waveguides being able to guide light in this spectral range. In order to do so, telluride materials were selected: Te₇₅Ge₁₅Ga₁₀ bulk glasses were chosen as substrates and TeGe films as guiding layers. The Te₇₅Ge₁₅Ga₁₀ bulk glasses were purified during their synthesis which ensures an optimal transmission in the whole range from 6 to 20 μm. TeGe thick films with different compositions were deposited by thermal co-evaporation. Homogeneous films with thickness up to 15 microns could be produced. The M-lines measurement of their refractive index at λ = 10.6 μm highlighted a linear behavior versus the atomic percentage in tellurium and confirmed their compatibility for the project. First planar waveguides could be optically characterized after having prepared their input and output facets by an appropriate polishing procedure. Guidance of light was demonstrated in the whole range [6-20 μm].

We report two novel strategies to integrate magneto-optical oxides on oxidized silicon and SOI platforms based on strip-loaded waveguide structures. By using conventional waveguide fabrication and thin film deposition techniques, strip-loaded waveguides for magneto-optical non-reciprocal phase shift (NRPS) applications can be integrated on a silicon platform. As a demonstration, two structures, i.e. As₂S₃/Y₃Fe₅O₁₂ (YIG) and YIG/SOI waveguides are fabricated. Using pulsed-laser deposition followed by rapid thermal annealing, yttrium iron oxide films in which more than 95 vol.% had crystallized into the YIG phase were achieved on both substrates. The optical loss of the As₂S₃/Y₃Fe₅O₁₂ waveguide was characterized by a cut-back method to be ~10 dB/cm at 1550 nm, while the optical loss of a 450nm wide YIG/SOI waveguide was determined to be 41 dB/cm at 1550 nm by measuring the quality factor Q of a pulley-type ring resonator consisting of such waveguides. The propagation loss of polycrystalline YIG on a SiO₂/Si substrate was around 50 dB/cm at 1550 nm wavelength. The NRPS and figure of merit of both waveguides were simulated. It is suggested that a Bi:YIG or Ce:YIG layer may be integrated in these waveguide structures to achieve a higher NRPS and figure of merit for optical isolator applications. These waveguide fabrication techniques offer a compact, low cost and etch-free route for integrating magneto-optical materials on a silicon platform, which may be useful for making future integrated optical isolators and other magneto-optical components.

We report on the design and realization of photonic integrated devices based on 3D organic microresonators. This has been achieved by combining microfluidics techniques and thin-film processes. The microfluidic device and the control of the flow rates of the continuous and dispersed phases allow the fabrication of organic microresonators with diameter ranging from 30 to 200 μm. The resonance of the sphere in air has been first investigated by using the Raman spectroscopy set-up demonstrating the appropriate photonic properties. Then the microresonators have been integrated on an organic chip made of the photosensitive resin SU-8 and positioned at the extremity of a taper and alongside a rib waveguide. The realization of these structures by thin-film processes needs one step UV-lithography leading to 6μm width and 30μm height. Both devices have proved the efficient evanescent coupling leading to the excitation of the whispering gallery modes confined at the surface of the organic 3D microresonators. Finally, a band-stop filter has been used to detect the resonance spectra of the resonators once integrated.

Erbium-doped aluminum oxide channel waveguides were fabricated on silicon substrates and their characteristics were investigated for Er concentrations ranging from 0.27 to 4.2 × 10²⁰ cm^-3. Background losses below 0.3 dB/cm at 1320 nm were measured. For optimum Er concentrations in the range of 1 to 2 × 10²⁰ cm^-3, internal net gain was obtained over a wavelength range of 80 nm (1500-1580 nm) and a peak gain of 2.0 dB/cm was measured at 1533 nm. 170 Gbit/s high-speed data amplification was demonstrated in an Al₂O₃:Er³⁺ channel waveguide with open eye diagrams and without penalty. A lossless 1×2 power splitter has been realized in Al₂O₃:Er³⁺ with net gain over a wavelength range of 40 nm (1525-1565 nm) across the complete telecom C-band.

We report the development of optofluidic ring resonator (OFRR) dye laser through the fluorescence resonance energy transfer (FRET) between the donor molecule labeled on an oligonucleotide and the acceptor molecule labeled on a complementary oligonucleotide. The OFRR is a thin-walled fused silica capillary with a diameter around 80 μm and a wall thickness of a few micrometers. The capillary cross-section forms a ring resonator supporting the high-Q whispering gallery modes (WGMs) with evanescent field penetrating into the capillary core, where gain medium flows through the OFRR capillary. In the OFRR FRET dye laser, the distance between donor and acceptor is controlled by the length of the DNA scaffold, which in turn determines the FRET efficiency. In this study, we investigate the lasing emission spectrum, threshold, and lasing power conversion efficiency. Cascade FRET lasing is also explored by using three dye molecules labeled on oligonucleotides. A lasing threshold as low as 5 μJ/mm² is demonstrated with the acceptor concentration of 30 μM.

An Erbium:Ytterbium codoped microcavity-based laser which is lithographically fabricated from sol-gel is demonstrated. Both single-mode and multimode lasing is observed in the C band (1550nm). The quality factor and pump threshold are experimentally determined for a series of erbium and ytterbium doping concentrations, verifying the inter-dependent relationship between the two dopants. The lasing threshold of the optimized device is 4.2 μW.

The realm of nanooptics is usually characterized by the interaction of light with structures having relevant feature sizes much smaller than the wavelength. To model such problems, a large variety of methods exists. However, most of them either require a periodic arrangement of a unit cell or can handle only single entities. But there exists a great variety of functional devices which may have either a spatial extent much larger than the wavelength and which comprise structural details with sizes in the order of a fraction of the wavelength or they may consist of an amorphous arrangement of strongly scattering entities. Such structures require large scale simulations where the fine details are retained. In this contribution we outline our latest research on such devices and detail the computational peculiarities we have to overcome. Presenting several examples, we show how simulations support the physical understanding of these devices. Examples are randomly textured surfaces used for solar cells, where guided modes excited in the light absorbing layers strongly affect the solar cell efficiency, amorphous metamaterials and stochastically arranged nanoantennas. The usage of computational experiments will be motivated by the unprecedented insight into the functionality of such components.

Optical properties of hybrid plasmonic waveguides and of low-Q cavities, formed by waveguides of finite length are investigated numerically. These structures are of interest as building-blocks of plasmon lasers. We use a time-harmonic finite-element package including a propagation-mode solver, a resonance-mode solver and a scattering solver for studying various properties of the system. Numerical convergence of all used methods is demonstrated.

We describe and analyze the phenomenon of partial image revivals in a multi-channel directional-coupler (MCDC) structure. Using supermodes, a MCDC is described as a composite waveguide structure and then analyzed in terms of multi-mode interference and the principle of self-imaging. As we bring the waveguides in the array closer together the supermodes beat to form partial images in between the complete mirror- and self-images. In this case, we have the advantage of the increased coupling and hence shorter image lengths, but with the disadvantage that the images are partial revivals of the input field. Nonetheless, we can take advantage of the partial image revivals that occur near complete mirror- and self-images, as they are almost complete images themselves. To demonstrate the use of this phenomenon we describe the simple design of a compact 1×2 wavelength division multiplexer based on a MCDC. The design highlights a trade-off between device length and isolation ratio, where although we use the partial self-image at 1.55 μm for a more compact device, the trade-off is a reduced isolation ratio when compared to 1.3 μm where a complete mirror-image is present.

Generic packaging concepts for silicon photonics have been developed in the frame of EU-funded Network of Excellence ePIXnet (FP6). Three approaches for Silicon photonic packaging will be presented within this paper. Two concepts provide solutions for fiber array coupling to high-index contrast photonic wire waveguide gratings. Third concept is the integration of inverted taper-based fiber coupling structure with silicon etched V-grooves. Using standardized SOI chip designs and commercial available assembly parts, the packaging concepts allow for small footprint or flexible use in an R&D environment. The work presented here has resulted from cooperation within the European Network of Excellence ePIXnet.

We report on quantum well intermixing of AlInGaAs-MQWs using the impurity-free vacancy diffusion method with dielectric capping layers which has potential for realization of photonic integrated circuits. The extent of the bandgap shifts with respect to different dielectric capping layers and alloy temperatures are investigated. The intermixing inhibitor and promoter are then integrated using combination of SiO₂ and SiN_x dielectric capping layers which shows a differential photoluminescence wavelength more than 110 nm. Based on this developed intermixing technique, we have fabricated AlInGaAs-InP based material stripe lasers emitting at two different wavelength ranges centered at 1519 nm and 1393 nm respectively. Characterizations including the current-voltage and electroluminescence measurements show that the integration of two-bandgaps can be achieved and furthermore a differential wavelength in lasing spectra up to 120 nm is demonstrated.

A new monolithic integration scheme of fabricating optical spot-size converter (SSC) is realized in this work. High-speed electroabsorption modulator (EAM) is used to integrate such SSC. By laterally tapering the active region of an optical waveguide through undercut active region, a vertically asymmetric waveguide coupler can be defined to form an SSC, where the top is a tapered active waveguide, and the bottom is a large core of passive waveguide mode-matched to single-mode fiber (SMF). Through the top tapered active waveguide, the effective index can be gradually varied in the propagation direction, momentarily matching the bottom low-index passive waveguide. It not only performs the resonant coupling in such asymmetric waveguide coupler, but also locks the transferred power by the tapered structure. InGaAsP/InP multiple quantum wells are used as active region of active waveguide. Based on the highly selective etching properties between InGaAsP and InP, the tapered active waveguide can be fabricated by a method, called selectively undercut-etching-active-region (UEAR), enabling the processing a narrow waveguide structure (up to submicron) by general wet etching from a large waveguide ridge. It also leads to good microwave performance of waveguide. By taking this advantage, a SSC-integrated EAM can perform high-speed electrical-to-optical (EO) response as well as low-insertion loss properties. A mode transfer efficiency of 70% is obtained in such SSC. By narrowing waveguide by UEAR, over 40 GHz of -3dB electrical-to-optical (EO) response is obtained from this device. The high efficient SSC integrated with high-speed EAM suggests that the UEAR technique can have potential for applications in high-speed optoelectronic fields.

Resonant leaky modes can be induced on dielectric, semiconductor, and metallic periodic layers patterned in one or two dimensions. Potential applications include bandpass and bandstop filters, laser mirrors, ultrasensitive biosensors, absorption enhancement in solar cells, security devices, tunable filters, nanoelectromechanical display pixels, dispersion/slow-light elements, and others. As there is now a growing realization worldwide of the utility of these devices, it is of interest to summarize their physical basis and present their applicability in photonic devices and systems. In particular, we have invented and implemented highly accurate, label-free, guided-mode resonance (GMR) biosensors that are being commercialized. The sensor is based on the high parametric sensitivity inherent in the fundamental resonance effect. As an attaching biomolecular layer changes the parameters of the resonance element, the resonance frequency (wavelength) changes. A target analyte interacting with a bio-selective layer on the sensor can thus be identified without additional processing or use of foreign tags. Another promising pursuit in this field is development of optical components including wideband mirrors, filters, and polarizers. We have experimentally realized such devices that exhibit a minimal layer count relative to their classical multilayer thin-film counterparts. Theoretical modeling has shown that wideband tuning of these filters is achievable by perturbing the structural symmetry using nano/microelectromechanical (MEMS) methods. MEMS-tuned resonance elements may be useful as pixels in spatial light modulators, tunable lasers, and multispectral imaging applications. Finally, mixed metallic/dielectric resonance elements exhibit simultaneous plasmonic and leaky-mode resonance effects. Their design and chief characteristics is described.

In this work, we describe the most recent progress towards the device modeling, fabrication, testing and system integration of active resonant subwavelength grating (RSG) devices. Passive RSG devices have been a subject of interest in subwavelength-structured surfaces (SWS) in recent years due to their narrow spectral response and high quality filtering performance. Modulating the bias voltage of interdigitated metal electrodes over an electrooptic thin film material enables the RSG components to act as actively tunable high-speed optical filters. The filter characteristics of the device can be engineered using the geometry of the device grating and underlying materials. Using electron beam lithography and specialized etch techniques, we have fabricated interdigitated metal electrodes on an insulating layer and BaTiO₃ thin film on sapphire substrate. With bias voltages of up to 100V, spectral red shifts of several nanometers are measured, as well as significant changes in the reflected and transmitted signal intensities around the 1.55um wavelength. Due to their small size and lack of moving parts, these devices are attractive for high speed spectral sensing applications. We will discuss the most recent device testing results as well as comment on the system integration aspects of this project.

We consider an aperiodic array of coupled metallic waveguides with varying subwavelength widths. For an incident plane wave, we numerically demonstrate that a focus of as small as one hundredth of a wavelength can be achieved for a focal distance that is much longer than the wavelength. Moreover, the focusing behavior can be controlled by changing either the incident wavelength, or the angle of incidence, thus providing the capability of nanoscale beam steering. We show that the behavior of such subwavelength focusing can be understood using Hamiltonian optics.

Resonant subwavelength gratings have proven to be excellent devices for producing narrow resonances useful for filtering applications. In this paper we discuss the use of RSGs in a rotary position encoder intended for use in harsh environments. To avoid problems with routing electrical signals to the encoder, a single fiber optic connection is used to address the device with multiplexed wavelengths corresponding to position bits. Each wavelength has a corresponding RSG that is patterned in the appropriate position locations. A demonstration device utilizing RSGs with TiO₂ and SiO₂ films on a silicon substrate will be presented. The design and modeling effort provided several RSGs with resonances addressable by a single tunable laser source. Since multimode fiber is used to route the optical signals, the gratings were designed to be polarization insensitive. Additionally, the individual RSGs accommodate significant wavelength shifts to simplify the integration of the encoder system. The fabrication of the devices was based on electron beam lithography and details of this work will be presented. Measurements of the individual RSGs as well as a demonstration of the determination of rotary position using these gratings will be shown.

The development of wafer-scale (3'' diameter) smart-cut lithium niobate (LN) single-crystal films of sub-micrometer thickness is reported. Z-cut LN wafers, implanted by high energy He-ions, are crystal-bonded to a SiO₂ layer on another Z-cut LN handle sample. The bonded pair of samples splits along the He-implanted layer by appropriate annealing. As this fabrication method is similar to the process widely used for silicon-on-insulator (SOI) fabrication, the resulting material is called LNOI. Two different routes to develop periodically poled LNOI photonic wires are discussed. The first one starts with poling of planar LNOI samples; the photonic wires are fabricated afterwards by ICP-etching. The second one starts with the fabrication of LNOI photonic wires; they are "locally" poled afterwards. As both approaches were not yet successful, a PPLN-substrate was ion beam sliced to generate a planar periodically poled LNOI sample directly. Using planar LNOI samples as starting material, high-quality photonic wires have been developed. The smallest structure has a cross-section of ~ 1 x 0.7 μm² only. Its optical properties with mode distributions, waveguide propagation losses, and group index were investigated. Moreover, the first periodically poled LNOI photonic wires were successfully fabricated, but not yet investigated optically. They are of great potential for second order nonlinear integrated optics.

We report on the fabrication of ion-sliced single-crystalline lithium niobate thin films and realization of electro-optically tunable microring resonators and photonic bandgap structures for high-density integrated optics devices. Using a home-built high-resolution laser lithography system we structured microring resonators with a free spectral range of > 7 nm, a quality factor of up to 10'000, and a tunability of 1 pm/V at wavelengths around 1.55 μm. Moreover, we show that the fabricated microrings can be detached from the original substrate and transferred onto any host substrate. This opens new possibilities for building hybrid integrated optics devices based on lithium niobate microrings and laterally or vertically coupled waveguides of different materials. Combining the laser lithography patterning and focused ion beam milling we have also fabricated planar photonic crystals structures. Triangular lattices of holes with a diameter of 240 nm and a separation of 500 nm exhibit a photonic bandgap in the wavelength range from 1390 and 1500 nm with an extinction ratio of up to 15 dB.

We review our development of sub-micron hot embossing or imprinting of glasses. We suggest that this is an emerging technology which shows great promise for the fabrication of glass photonic integrated circuits (PICs). The approach makes use of T_g (the glass transition) which gives inorganic compound glasses a key advantage over crystalline materials for fabricating photonic devices and PICs. Thus, when a glass is heated above T_g, the glass transforms to a supercooled liquid which may be shaped e.g. moulded. Cooling back down through T_g allows the shaping to be retained in the glassy state at room temperature. In this way, glasses may be shaped from the macro-scale e.g. to make light-refracting lenses down to the nano-scale e.g. for waveguides or photonic crystal arrays for dispersion management. Hence T_g is a reversible door to making photonic devices. This claim is illustrated by reviewing our recent work on hot embossing of inorganic compound glasses to make waveguides. Opportunities and potential pitfalls are highlighted. The background understanding of glass science underpinning the hot embossing methodology is presented.

Design, fabrication and optimization of high refractive index (2.1 @ 1070 nm), sub-micron thickness (200 nm) Tantalum Pentoxide waveguides is reported. Optimization of fabrication parameters reduces the propagation loss to ~ 1 dB/cm @ 1070 nm for Ta₂O₅ waveguides. Ta₂O₅ waveguides were found to be stable for high power application with no significant absorption peaks over a large range of wavelengths (600-1700 nm). Ta₂O₅ waveguides provide high intensity in the evanescent field, which is useful for efficient optical propelling of micro-particles. We have employed Ta₂O₅ waveguide to propel polystyrene micro-particles with 50 μm/s velocity.

Buried-type optical waveguide with blanches for the gate of optical signals was fabricated by nano ion-exchange method using the probe of atomic force microscope (AFM) as an electrode. 2-step procedure of the electric field-assisted Ag/Na-ion exchange followed by K/Na one was applied to prepare the waveguide structure inside the glass substrate. Pt-coated AFM probe as a cathode was attached to the glass surface and Ag⁺ ions in the core underneath the probe were partially extracted towards the glass surface. The protruding high index regions from the core towards the glass surface were found to work as the optical gate where the wavelength and intensity of light through the gate was determined by the condition of nano ion-exchange treatment.

Refractive index engineering (RI_Eng) by ion implantations is a generic methodology for constructing multi-component integrated circuits of electrooptic and nanophotonic devices with sub-wavelength features operating in the visible - near IR wavelengths. The essence of the method is to perform spatially selective implantations for sculpting complex 3D pre-designed amorphized patterns with sub-wavelength features and reduced refractive index within the volume of the substrate. A number of devices that were constructed in a substrate of potassium lithium tantalate niobate are described, including a submerged slab waveguide, an optical wire and a channel waveguide array.

We report on the photorefractive properties of tin-silica slab waveguides, deposited on vitreous-SiO₂ by means of sol-gel dip-coating technique. The basic composition of these amorphous binary systems is 75 SiO₂ - 25 SnO₂ mol% with 1 mol% of Eu³⁺ ions. Europium was chosen as an optical probe of the glass structure. These guiding structures exhibit low propagation losses (around 0.5 dB/cm at 633 nm) and a high refractive index modulation, as large as - 1.5 × 10^-3 under the UV irradiation of a KrF excimer laser source at λ = 248 nm, suitable for writing waveguide gratings.

We have been studying fluorescence enhancement from labeled oligonucleotides immobilized inside metallic nanoapertures. Fluorescence enhancement is a direct result of the localized field intensity enhancement within these nanoapertures from plasmonic excitation. We have also been developing specific surface chemistries for metallic films to localize capture oligos only inside these nanoapertures. Some of our recent results are overviewed.

The realization and characterization of the leaky loop integrated Fourier transform spectrometer (LLIFTS) in integrated optics are described. The component is compact, costless with no moveable parts. The principle lies on a two-beam interferometer in planar design using a leaky loop waveguide structure. The radiated part leaking from the loop induces an interference pattern at the end of the component. The structure has the advantage of controlling the shape of the interference pattern. Ion exchange technology used here requires only a single lithography step. Measurements have been made in the near infrared domain with wavelength resolution of 11 nm.

Transmission and reflection spectra of periodic and random stacks comprising positive index materials and metamaterials have been extensively studied. In this paper we investigate the effectiveness of periodic stacks of PIM/NIM for use as a sensor. The transfer matrix method is used to find the transmittance and reflectance. Differences between the zero average refractive index bandgap and Bragg bandgap are illustrated. It is shown how these bandgaps can be used as the basis for designing sensors with minimal cross-sensitivity.

A versatile, compact, and sensitive fiber-based optical Fabry-Pérot (FP) gas sensor is reported in this paper. The sensor probe is composed of a silver layer and a vapor-sensitive polymer layer that are deposited on the cleaved fiber endface to form an FP cavity sequentially. The interference spectrum generated from the reflected light at the silver-polymer and polymer-air interfaces changes upon the absorption of gas analytes. This structure enables using polymer of any refractive index (RI) as the sensing layer, which significantly enhances the sensor versatility. Two polymers of polyethylene glycol (PEG) 400 (RI=1.465-1.469) and Norland Optical Adhesive (NOA) 81 (RI=1.53-1.56) are used as the gas sensing polymer to demonstrate the feasibility of the FP sensor, and show drastically different sensor response to various gas analytes. In addition, we assemble the FP sensor with a short fused silica capillary into a sensor module, and employ it in the gas chromotgraphy (GC) system to investigate its capability as a GC detector for rapid on-column detection.

The size and the weight of current spectrometers is a serious issue regarding various applications, however the technologies used in existing spectrometers prevent them from substantial improvement. SWIFTS (Stationary Wave Integrated Fourier Transform Spectrometer) is a new familyof spectrometers based on a verypromising technology. It is based on an original wayto fully sample the Fourier interferogram obtained in a waveguide byeither a reflection (SWIFTS Lippmann) or counter-propagative (SWIFTS Gabor) interference phenomenon. The sampling can be simultaneouslydone without anymo ving part thanks to "nano-detectors" located in the evanescent field of the waveguide. It allows a dramatic reduction of the size and the weight of spectrometers while improving their performances (high stabilityand high resolution δσ < 1cm^-1). Here, we present the development status of the SWIFTS Gabor and the results obtained (resolution of 4cm^-1) with existing technical solutions for the "nano-detectors" in visible and near infrared.

Fiber optic gyroscope is an important development in the field of fiber optic sensors. It is now considered an alternative technology to the mechanical and laser gyroscopes for the inertial guidance and control applications. The advantages of FOG over mechanical gyroscopes are many like instantaneous operation, wide dynamic range, no g-sensitivity, maintenance free, and capability to withstand high shock and vibration and so on. The advantages over laser gyroscopes include cost effectiveness, light weight, low power consumption and improved ruggedness. The optical gyroscope principle was first demonstrated by Sagnac in 1913. Optical gyroscopes implemented so far use Sagnac effect, which states that an optical path difference induced by counter propagating beams in a rotating reference frame is proportional to the absolute rotation. The main requirement of a FOG is perfect reciprocity, i.e. in the absence of rotation, the counter propagating beams inside the fiber must travel identical paths thus resulting in zero phase shift. The phase shift in a Sagnac interferometer not only comprises of a non-reciprocal sources that set practical performance limits. These non-reciprocal sources generate random time varying output resulting in a bias drift even under zero rotation rates, which causes serious problems in present day gyroscope. In a FOG the reciprocal configuration ensures the bias stability, signal processing is used to obtain maximum sensitivity, a broad band source is used to eliminate the effect of back scattering, polarization coupling and Kerr effect and the closed loop operation is used to linearize the scale factor and improve its stability.

Nanoscale metal stripes support plasmonic modes with strongly confined fields. When combined with a waveguide-coupled microfluidic system, these stripes can provide highly sub-wavelength excitation regions for single biomolecule sensing, e.g. dark-field fluorescence detection of tagged DNA. Using a prism coupled geometry, we experimentally characterize the dispersion of plasmon modes in 80-500 nm wide metal stripes. Our results agree well with numerical modeling. We investigate how the stripe morphology affects the mode distribution and dispersion, and consider the implications for integrated near field fluorescence excitation.

We introduce a periodic plasmonic waveguiding structure which supports a guided subwavelength optical mode with slow group velocity at a tunable wavelength range and with a tunable slowdown factor. The structure consists of a metal-dielectric-metal (MDM) waveguide side-coupled to a periodic array of MDM stub resonators. Both the MDM waveguide and MDM stub resonators have deep subwavelength widths. We show that such a structure supports a guided optical mode with slow group velocity. The wavelength range in which slow light propagation is achieved can be tuned by adjusting the MDM stub resonator length and the periodicity of the structure. We also show that the slowdown factor increases as the periodicity of the structure decreases, and that light can be slowed down by several orders of magnitude. We find that there is a tradeoff between the slowdown factor and the propagation length of the supported optical mode. In addition, for a given slowdown factor and operating wavelength, the propagation length of the optical mode in the periodic plasmonic waveguide is much larger than the propagation length of the mode supported by a conventional MDM waveguide, in which the slowdown factor can be tuned by adjusting the dielectric layer width. Finally, we show that light can be coupled efficiently from a conventional MDM waveguide to such a periodic plasmonic waveguide. Such slow-light plasmonic waveguides could be potentially used in nonlinear and sensing applications. We use a characteristic impedance model and transmission line theory to account for their behavior.

We propose a "slot-to-slot" coupler to convert power between optical and metal-insulator-metal (MIM) plasmonic modes. Coupling efficiency of larger than 60% is obtained from 2D FDTD simulation. Based on this prototype, a quasi-MIM plasmonic junction is demonstrated using e-beam lithography onto an SOI substrate. The junction is formed by depositing a thin layer of gold (~20 nm) on part of a dielectric slot. When probed by 1520-nm laser, coupling efficiency of 36% is achieved for a 500-nm long quasi-MIM junction. Optical modulation is under investigation by pumping the device using visible light to change the optical property of gold.

Metal nanoparticle assemblies of designed structure are investigated as substrates for polarization manipulation in the near field region. Gold nanoparticles are known for their optical response due to the excitation of surface plasmons. Surface plasmons in coupled particles can strongly modulate light either in the far or near field region. The most common near field application of coupled particles is as field enhancing substrates for amplifying signals of molecules, for example, Raman signals, IR signals or fluorescence signals. However, the capabilities of metal nanoparticle assemblies can be extended beyond field amplification. Groups of particles can function as small antennas which convert far field excitation into localized fields with specific polarization. Through simulations we demonstrate that the near field polarization can be partially controlled through suitable design of nanoparticle configuration. The benefit of this configuration is that no probe excitation or other localized excitation is needed. The far field signal is converted into specific spots with designed polarization, which is not necessarily the same as excitation. Polarization is manipulated through the coupling of different surface plasmon modes. This polarization modulation extends down to the few nanometer scale and may provide us more control of interaction of light with nano-scale emitters or molecules.

We propose a novel approach for efficient sensitivity analysis and design optimization of surface plasmon polaritons (SPPs) based waveguide structures. This approach has been utilized to analyze and propose novel designs of different structures. It has been exploited to design a novel SPP waveguide using a metal loaded on silicon on insulator (SOI) for subwavelength applications. In this design, the SOI material is utilized due to its wide application in electronic circuits. It also allows for strong guiding and hence subwavelength light confinement. The utilized metal is gold (Au) at a wavelength of 1.55 μm. The effect of the different design parameters of this structure on the propagation length of the fundamental TM mode is efficiently studied using the proposed approach. The imaginary distance 3D ADI BPM is utilized to calculate the propagation length. The sensitivity information is then estimated using the adjoint variable method without any additional simulations. The same approach is utilized to propose an optimized design of new 1x3 SPP power splitter/combiner using metal on insulator. In this design the multimode interference phenomenon is utilized. Our goal is to minimize the insertion loss for practical applications. The optimized design has a low insertion loss of 1.5 dB and compact size.

The performances of a random-metal dielectric film composed of silver and fused silica balls were analyzed experimentally under optical AM and FM signal transmission. Optical AM and FM signals emitted from a 1550-nm-band laser diode were clearly transmitted in the random metal-dielectric film and through the optical near field generated on the film. Based on these signal transmission results, the feasibility of using this film to transmit optical AM and FM signals was experimentally confirmed in detail.

Label-free biosensors based on polymeric waveguides with Bragg reflection grating are demonstrated for the purpose of the highly sensitive protein detectors. Due to the unique processibility of the polymers in terms of nano-imprinting and the injection molding, the polymer waveguide devices has large potential to provide cost-effective solution for the disposable biosensors as long as robust immunoassay process is developed. The large contrast waveguide consisting of low index fluorinated polymer exhibits enhanced sensitivity of detecting cover index variation by 1.9 times.