Microresonators are basic building blocks for compact photonic integrated circuits (PICs). The performance of the microresonators depends on their intrinsic and loaded quality factors (Q). Here we demonstrate the optical characterization of a single crystalline silicon microtoroidal resonator with integrated MEMS-actuated tunable optical coupler. The device is realized on a two-layer silicon-on-insulator (SOI) structure. It is fabricated by combining hydrogen annealing and wafer bonding processes. The device has been demonstrated to be operated in all three coupling regimes: under-coupling, critical coupling, and over-coupling. At an actuation voltage of 114 V, the extinction ratio at the resonant wavelength of 1548.18 nm reaches 22.4 dB. To characterize these quality-factor tunable microtoroidal resonators, we have also developed a comprehensive model based on time-domain coupling theory. The intrinsic and loaded Qs are extracted by fitting the experimental curves with the model. The intrinsic Q is 110,000. And the loaded Q is continuously tunable from 110,000 to 5,400. This device has potential applications in variable bandwidth filters, reconfigurable add-drop multiplexers, and optical sensors.

We have experimentally demonstrated the fabrication and the functioning of a rapidly prototyped optical cylindrical microcavity waveguide based biosensor. The device works on the principle of determination of the change to the light intensity of the input coupled light to the waveguide due to the interaction and binding of proteins to the cylindrical waveguide structure. The variation to the coupled light intensity is dependant on the nature of the protein i.e. its surface charge and the density of the proteins. This technique has been used to identify a specific protein biomarker associated with the identification of vulnerable coronary plaque -Myeloperoxidase (MPO). Detection sensitivity in the order of pg/ml has been demonstrated. The detection speed is in the order of seconds from the time of injection of the protein onto the sensor surface. The optical signature that is obtained to identify a protein is entirely dependant on the nature of adsorption of the protein on to the cylindrical cavity surfaces. This technique is a demonstration of detection of nanoscale proteins using a label free optical biosensor technique with unprecedented sensitivity.

This work focuses on the effects of custom-designed, two-dimensional grating structures on the sensitivity of optical waveguides biosensors in the input grating coupler configuration. Calculations suggest that suitably designed diffractive structures with optimum pitch in two orthogonal directions can increase the sensitivity of devices when compared to a conventional one-dimensional grating under the same conditions. A set of six diffractive structures designed for 1550 nm wavelength were fabricated by thermal nano-imprint lithography on silicon oxynitride waveguides; the silicon master stamp was patterned by deep UV stepper lithography. Preliminary experimental results indicate a sensitivity enhancement of a factor two due to the 2D diffractive couplers.

The liquid core optical ring resonator (LCORR) sensor is a newly developed capillary-based ring resonator that integrates microfluidics with photonic sensing technology. The circular cross-section of the capillary forms a ring resonator that supports whispering gallery modes (WGM). The WGM evanescent field is exposed to the capillary core and detects the aqueous samples conducted by the capillary using a label-free protocol. The high-Q of the WGM allows for repetitive light-analyte interaction, resulting in excellent sensitivity. Recently a detection limit of the LCORR on the order of 10^-6 refractive index units was reported. In this work, we have further integrated the LCORR with an anti-resonant reflective optical waveguide (ARROW) array for multiplexed sensor development. The ARROW, with an array of 8 waveguides separated by 250 microns each, consists of a core and a lower reflective double-layer with alternating high and low refractive index, and thus has a significant evanescent field above the waveguide. The WGM is excited at each LCORR/ARROW junction simultaneously when the LCORR is brought into contact with the ARROW array. We experimentally investigated the optimal waveguide geometry for WGM excitation using a range of waveguide heights from 2 to 5 microns. Furthermore, the LCORR/ARROW system is utilized for a biomolecule sensing demonstration. The LCORR/ARROW system is not only essential for assembling a robust, practical, and densely multiplexed sensor array, but also enables on-capillary flow analysis that has broad applications in capillary electrophoresis, chromatography, and lab-on-a-chip development.

With the development of optical telecommunication systems, there has been a huge work realized on integrated optics. Indeed, today several technologies are available to realize integrated devices. Among them, there is ion-exchange on glass which has been successfully used for more than twenty years to realize integrated optics devices such as wavelength multiplexers, splitters, optical amplifiers, lasers or sensors. In this paper we review the advances made by integrated optics on glass and we try to position this technology towards other technologies.

Due to remarkable properties of the chalcogenide glasses, especially sulphide glasses, amorphous chalcogenide films should play a motivating role in the development of integrated planar optical circuits and their components. This paper describes the fabrication and properties of optical waveguides of pure and rare earth doped sulphide glass films prepared by two complementary techniques: RF magnetron sputtering and pulsed laser deposition (PLD). The deposition parameters were adjusted to obtain, from sulphide glass targets with a careful control of their purity, layers with appropriate compositional, morphological, structural characteristics and optical properties. These films have been characterized by micro-Raman spectroscopy, atomic force microscopy (AFM), X-ray diffraction technique (XRD) and scanning electron microscopy (SEM) coupled with energy dispersive X-ray measurements (EDX). Their optical properties were measured thanks to m-lines prism coupling and near field methods. Rib waveguides were produced by dry etching under CF₄, CHF₃ and SF₆ atmosphere. The photo-luminescence of rare earth doped GeGaSbS films were clearly observed in the n-IR spectral domain and the study of their decay lifetime will be presented. First tests were carried out to functionalise the films with the aim of using them as sensor.

Tellurite glasses are known to be highly promising materials for broadening the amplification bandwidth of Er³⁺-doped waveguide amplifiers, as they have large stimulated emission cross sections and broad emission bandwidth around the 1.55 micron wavelength. Furthermore, they exhibit a wide transmission range, the lowest vibrational energy among oxide glass formers, and good non linear properties. Nevertheless fabrication of waveguides in tellurite glasses appears to be a challenging task and so far it has been reported only in a few papers. Here we report on the development of a method based on high-energy ion beam irradiation to create active channel waveguides in a tungsten-tellurite glass doped with Er₂O₃. The waveguide stripes have been realized by 1.5 MeV N⁺ irradiation of the glass sample through a silicon mask with doses of 1.0 x 10¹⁶ ions/cm² using a 5 MeV Van de Graaff accelerator. Multimode light propagation has indeed been observed in these channels, confirming the effectiveness of this technique.

Ion-exchange on glass has been successfully used for more than twenty years to realize integrated optics devices such as wavelength multiplexers, splitters, optical amplifiers, lasers or sensors. One of the major issue is today to integrate more functions on a single chip which is usually realized be reducing the dimensions of the waveguides. Nonetheless this reduction is intrinsically limited by the maximum index variation achievable. For this reason, we propose and investigate in this article the realization of 3D structures where waveguides are integrated vertically instead of horizontally. Based on the selective burial of ion-exchanged waveguides and the cascading of multiple ion-exchanges, the realization of "vertical" asymmetric and symmetric Y-junctions have been investigated theoretically.

We present a reconfigurable, compact, low loss, optical switch in silicon. The device utilizes the self-collimation properties of photonic crystal structures and provides a technique for efficiently switching an electromagnetic wave guided through a pre-engineered dispersion based photonic crystal self-guiding structure. The electromagnetic wave can be either in the microwave or optical regime based on the constituent materials and dimensions of the photonic crystal host. We propose that the "loss tangent" of dielectric material in the switching region can be modified by external "commands" to control the direction of propagation of the self-collimated signal and hence attain switching, thereby redirecting the light. Based on the geometrical orientation and position of the applied electric field, electromagnetic waves can be completely redirected (switched), or partially routed towards any arbitrary direction on a Manhattan grid or network. We have found that the induced loss does not significantly attenuate the waves switched in any direction. The structure presented can be generalized to an arbitrary N by M interconnected switching network or fabric, where the switching topology can be dynamically modulated by the application of external fields. To attain switching, the free-carrier absorption loss of Si is controlled by carrier injection from forward-biased PN junction. The concept device is designed and analyzed using the FastFDTD^TM accelerated hardware based FDTD technology.

A shallow-etched, distributed grating is proposed as a wavelength demultiplexer. The distributed grating constitutes a structure with completely decoupled reflective and diffractive properties. The theory behind the layout of the distributed grating is presented. The structure is modeled using RCWA and FDTD. Modeling results predict up to 79% efficiency over a 60nm wavelength range. Device fabrication results are presented. Early optical characterization of a test structure confirms the expected behavior for the device.

Bragg grating reflectors etched in amorphous silicon overlay films have been integrated with Ti:LiNbO₃ optical waveguides. Narrow (0.05 nm) reflectance spectrum with > 20 dB dip in the transmittance spectrum have been obtained at a wavelength of 1542.7 nm for TE polarization. The reflectance in the channel waveguides depends strongly on the depth of the etched grating. The effect of the Bragg waveguide loss factor on the transmittance and reflectance spectra is investigated using a model for contradirectional coupling that includes an attenuation coefficient. Good agreement between model predictions and experimental results is obtained. Applications of such integrated gratings in the fabrication of distributed feedback type and Fabry-Perot type electrooptic intensity modulators, for low switching voltage and high extinction needs, are demonstrated.

The Bragg reflection waveguide (BRW), or one-dimensional photonic crystal waveguide, has recently been proposed for a wide spectrum of applications ranging from particle acceleration to nonlinear frequency conversion. In this work, we conduct a thorough analytical investigation of the quarter-wave BRW, in which the transverse wavevector has a phase thickness of &pgr;/2 in each layer of the resonant cladding. For this case, an analytical solution to the mode dispersion equation is derived, and it is shown that the quarter-wave BRW is polarization degenerate, although the TE and TM mode profiles differ significantly as the external Brewster angle condition in the cladding is approached. Analytical expressions for waveguide properties such as the modal normalization constants, propagation loss, and overlap factors between the mode and each waveguide layer are derived. Finally, a perturbation theory is developed to calculate dispersion and tuning curves for the waveguide.

Recently the use of "vortex" beams of high azimuthal mode number has been proposed as a way of increasing the maximum peak power through-put of optical fibers beyond the few MW allowed for Gaussian beams by self-focusing. We report a numerical investigation of these and other schemes using a beam propagation approach that includes a Kerr-type nonlinearity.

Adaptive finite elements are the method of choice for accurate simulations of optical components. However as shown recently by Bienstman et al. many finite element mode solvers fail to compute the propagation constant's imaginary part of a leaky waveguide with sufficient accuracy. In this paper we show that with a special goal oriented error estimator for capturing radiation losses this problem is overcome.

There is a demand for reliable photonic switches and routers, of moderate switching or routing order, that can be integrated easily into photonic integrated circuits. For some time, low order MMI devices have been employed to provide a variety of circuit routing and switching functions. However, good performance of higher order MMI devices has been more difficult to achieve. This paper reviews the design criteria and design primitives for MMI structures and highlights their advantages and shortcomings.

Organic light emitting diodes are deemed to be valuable light sources for displays and general illumination in the future. In the last decade remarkable progress was made concerning materials, lifetime, and production techniques. One of the remaining challenges is to increase the light extraction efficiency of these devices. Due to the internal structure of the diodes, the light emitted by electron-hole recombinations within the electro-luminescent layer may be transferred into several channels: to slab guided modes, to substrate guided modes, and, to some limited extent only, to air propagating modes, directly. In order to get some physical insight where and why photons may be trapped in the slab geometry, a modal analysis is helpful. In configurations where metallic materials are used, the transversal magnetic light is prone to be annihilated by coupling to surface-plasmon polaritons which may have propagation length of a few microns only. A high index of refraction of the emitting material and an indium-tin-oxide electrode, eventually,contribute to light confinement within guided modes for both polarisations. In order to evaluate what parts of the dipole-like emission are transferred to what channel several methods can be used, e.g. the Finite-Difference-Time-Domain-Method, a rigorous coupled wave analysis including internal sources, and an approach based on Green-functions. Although the latter method is restricted to a plane geometry, it is a quite fast tool, which is well suited for the optimisation of a layered structure. To maximize the emission of the organic diodes, two basic strategies are self-evident. The first is to aim at a restricted coupling to guided waves. The second one addresses the recycling of light from unavoidable guided modes to air propagating modes. This can be achieved e.g. by scattering, by gratings, and by lens arrays, respectively.

This paper addresses on the theoretical analysis of a novel active ring microresonator filter, which is designed on Er-Yb co-doped phosphate glass. The filter characteristics of the proposed filter is analyzed by transfer matrix method, some universal relations for coupling of optical power between microresonator and dielectric waveguides and pump power are presented. The analytical expressions of filter bandwidth, free spectral range, and finesse are derived. Numerical results demonstrate that the change of pump power does not alter the resonance performance of ring micro-resonator filter, the improvement of which will have important effect on output characteristics of filter: reducing the filter bandwidth and increasing the finesse of the resonator filter.

A numerical optimization technique coupled with a finite element frequency domain solver was applied to a variety of Si nanowire photonic devices in an attempt to improve transmissions or matching to predefined criteria. The optimisation procedures are iterative in nature, in that they approach the optimal solution by exploring a sequence of carefully selected points in the parameter space. For any optimisation procedure to be effective, a good optimiser needs to be coupled with an efficient solver capable of modeling correctly all device configurations allowed by the parameter space. In the case of electromagnetic problems, it is particularly important that the divergence free condition is obeyed. The solver used here satisfies this condition and therefore greatly reduces the chances of the optimiser finding artificial optimal solutions with incorrect field distributions. This FEFD is used by a deterministic global optimisation method, which systematically subdivides the parameter space to split more quickly in regions most likely to contain an optimum. Since the entire parameter space is eventually explored, this optimisation technique is not only guaranteed to (eventually) find the globally optimal solution, but can also show other interesting local optima. As no gradient information is required, the method works well even in the presence of the random errors typically occurring when using Finite Element solvers where a unique optimised mesh is generated for each calculation.

We present an overview of a novel first principles quantum approach to designing and optimizing semiconductor QW material systems for target wavelengths. Using these microscopic inputs as basic building blocks we predict the L-I characteristic for a low power InGaPAs ridge laser without having to use adjustable fit parameters. Finally we employ these microscopic inputs to develop sophisticated simulation capabilities for designing and optimizing end packaged high power laser structures. As an explicit example of the latter, we consider the design and experimental demonstration of a vertical external cavity semiconductor laser (VECSEL).

Integration of semiconductor and metal structures into optical fibers to enable fusion of semiconductor optoelectronic function with glass optical fibers is discussed. A chemical vapor deposition (CVD)-like process, adapted for high pressure flow within microstructured optical fibers allows for flexible fabrication of such structures. Integration of semiconductor optoelectronic devices such as lasers, detectors, and modulators into fibers may now become possible.

A new approach to the physical description and quantification of bend loss in arbitrarily bent single-mode fibres is based on the coupling of the fundamental mode to cladding modes due solely to curvature change along the fibre. It is shown that there is an optimum bend design criterion that can reduce bend loss to almost arbitrarily low levels regardless of curvature provided only that the fibre coating index value is sufficiently smaller than that of the cladding index. This criterion has an analogy with the corresponding criterion for the design of approximately adiabatic single-mode depressed-cladding and W-fibres tapers.

We propose to exploit the unique properties of surface plasmons to enhance the signal-to-noise ratio of mid-infrared photodetectors. The proposed photodetector consists of a slit in a metallic slab filled with absorptive semiconductor material. Light absorption in the slit is enhanced due to Fabry-Perot resonances. Further absorption enhancement is achieved by surrounding the slit with a series of periodic grooves that enable the excitation of surface plasmons that carry electromagnetic energy towards the slit. Using this scheme, we design and optimize a photodetector operating at lambda_o = 9.8 microns with a roughly 250 times enhancement in the absorption per unit of volume of semiconductor material compared to conventional photodetectors operating at the same wavelength.

This paper describes a high sensitivity integrated optical sensor based on combined sensing of modal changes including amplitude, phase, and shape. The scheme is extremely simple, consisting of a single waveguide structure supporting two guided modes acting as sensor section, and a single guided mode in the output section. The transition of modes from the sensing to the output section is designed so that both modes contribute to the power of the output section mode. In this method, small changes in the sensing section are translated into power changes in the output section. Sensitivity values calculated for the new structure are an order of magnitude higher compared to previously reported SPR sensors. External control of the differential phase between the two propagating modes allows higher sensitivity, extended working range, and simplifies fabrication constraints.

We theoretically investigate the properties of compact couplers between high-index contrast dielectric slab waveguides and two-dimensional metal-dielectric-metal subwavelength plasmonic waveguides. We show that a coupler created by simply placing a dielectric waveguide terminated flat at the exit end of a plasmonic waveguide can be designed to have a transmission efficiency of ~70% at the optical communication wavelength. We also show that the transmission efficiency of the couplers can be further increased by using optimized multisection tapers. In both cases the transmission response is broadband. In addition, we investigate the properties of a Fabry-Perot structure in which light is coupled in and out of a plasmonic waveguide sandwiched between dielectric waveguides. Finally, we discuss potential fabrication processes for structures that demonstrate the predicted effects.

Plasmonic structures in lithium niobate are discussed, particularly long-range (low-loss) straight and curved metal stripe waveguides and electro-optic sections. Long-range waveguides are constructed as a thin narrow metal stripe embedded in a homogeneous optically infinite lithium niobate background. Structures are fabricated using trenching, direct wafer bonding and polishing, resulting in metal stripes and features bounded by lithium niobate lower and upper claddings. Theory and fabrication are discussed, and preliminary experimental results are presented.

In this paper, Digital Holographic Microscopy (DHM) is presented as a powerful tool for quality control of microoptical components. It will be shown that not only the single-shot full field-of-view nanometer axial resolution makes DHM an ideal solution for such samples, but the DHM numerical wavefront correction formalism is perfectly adapted to provide advanced features like aberration coefficients, radius of curvature or optical surfaces roughness measurements. Both transmission and reflection configurations can be used depending of the micro-components under investigation. A transparent high aspect-ratio micro-components investigation procedure is also exposed in order to unable phase unwrapping. Each feature is illustrated with typical examples, ranging from a wide variety of micro-lenses (aspherical, cylindrical, squared) to cornercube micro-structures or diffractive elements.

The integration of optical interconnections in printed circuit boards (PCBs) is an emerging field that arouses rapidly growing interest worldwide. At present the key issue is to identify a technical concept, which allows for the realization of optical interconnections that are compatible to existing PCB manufacturing processes. Above all, the material in which the optical interconnections are embedded has to withstand increased temperatures and lamination pressures as well as various wet chemistry processes. AT&S uses so-called two-photon absorption (TPA) laser structuring - a rather new and innovative technology - to realize optical circuits in a special polymer layer. In this case a near infrared laser is applied working in the femto-second regime. The high photon density that can be reached in the laser's focus results in a modification of the optical polymer, which is usually photosensitive in the UV-spectrum of light only. In our particular case, the refractive index of the optical polymer is increased. Choosing the right laser intensity and focus propagation speed one achieves a waveguide well embedded within the polymer layer, which has not been affected by the laser. In contrast to one-photon absorption, which only allows a two dimensional respectively lateral modification of a polymer, this technology allows a modification within the volume resulting in 3D-microstructures inside the polymer layer. Apart from the possibility to realize structures in three dimensions, this TPA-technique has additional advantages. First of all, it allows one step fabrication, which reduces costs and production time compared to etching procedures or conventional UV lithography processes. Moreover, this technique allows varying the waveguide's cross section geometry and diameter simply varying size and form of the structuring laser focus. Whereas the realization of optical waveguides is not challenging anymore the coupling of waveguides with optoelectronic components is rather delicate. That is, the waveguide's ends have to be accurately positioned close to the emitting surface of the signal source and the sensing area of the light detector, respectively. Using the TPA technology to structure optical waveguides AT&S has successfully evaluated a powerful method to solve this interface problem for the realization of integrated optical interconnections (IOIs) on PCBs.

We investigate the properties of a multimode-interference (MMI) coupled micro ring cavity resonator with total-internal-reflection (TIR) mirrors and a semiconductor optical amplifier (SOA). The TIR mirrors were fabricated by the self-aligned process with a loss of 0.7 dB per mirror. The length and width of an MMI are 142 &mgr;m and 10 &mgr;m, respectively. The resulting free spectral range (FSR) of the resonator was approximately 1.698 nm near 1571 nm and the extinction ratio was about 17 dB. These devices might be useful as optical switching and add-drop filters in a photonic integrated circuit or as small and fast resonator devices.

The unique optical properties of photonic crystals allow a dense and simple integration of optical functionality on a small footprint. We have investigated the integration of tunable photonic crystal (PhC) lasers with a wavelength monitor. The small size of the monitor allows an integration on an all-active layer structure, which leads to a rather simple fabrication process. The tunable lasers are based on two coupled PhC waveguides with slightly different length. PhC mirrors are placed at the end, joint and front of the two waveguides. Tuning is achieved by a variation of the injection currents in the two segments. The wavelength monitor, which is placed behind the rear mirror of the laser, consists of a multi-mode PhC waveguide. Mode coupling between the fundamental mode and a higher order mode results in a wavelength-dependent transmission of the waveguide. In the region of the mode coupling, the higher order mode is extracted out of the waveguide through a sufficiently thin waveguide boundary. The power of the transmitted and extracted light is detected by two photodiodes, which are integrated with the wavelength monitor. The photocurrents of the these diodes show a clear dependence on the laser wavelength, in good agreement with simulations.

An analysis of superprism effect in low index contrast polymer photonic crystal is presented. It shows extremely sensitivity to the wavelength and angle of the incident light due to the strong anisotropy of photonic band structures. Two-dimensional (2-D) polymer photonic crystals with triangular lattice structure were fabricated by soft lithography using elastomeric polydimethylsiloxane (PDMS) templates. Dense two dimensional photonic crystal superprism structures with feature sizes of 150-500nm and aspect ratios of up to 1.25 were successfully replicated by soft lithography. Large field size and easy fabrication are two major advantages when compared with other imprint technology. Atomic Force Microscopy images showed that the molded structures had high fidelity to the masters. Such an effective, low cost, and high throughput soft lithography technique could find wide use in making photonic crystal based nanostructures.

We present a new high-index-contrast material system to realize ridge waveguides and PhC waveguides made of a thin silicon slab embedded in two silica layers. Hence fully symmetrical structures can be etched and two important conditions for low-loss guiding of light can be matched: The symmetry properties of the material avoid polarization mixing and the high index contrast leads to strong confinement of light. Because of operating completely below the lightcone the PhC waveguides allow theoretically lossless guiding of light.

Compact photonic crystal mirrors (PCM) formed in suspended InP membranes are theoretically and experimentally studied under normal incidence. They are based on the coupling of free space waves with slow Bloch modes of the crystal. These mirrors provide high-efficiency and broadband reflectivity (stop-band superior to 400nm), when involving two slow Bloch modes of the crystal. They allow also for an accurate control of the polarization. These PCMs can be used in new photonic devices, where they replace DBR mirrors. The authors report on the demonstration of a compact and highly selective (Q>1000) tunable filter at 1.55&mgr;m, using a Fabry-Perot resonator combining a bottom micromachined 3-pair-InP/air-gap Bragg reflector with a top InP/air PCM. Micromechanical tuning of the device via electrostatic actuation is also demonstrated over a 20nm range for a maximum 4V tuning voltage. The active version of this device is also considered: a PCM-VCSEL is studied, combining a solid 40 quarter wavelength InP/InGaAlAs DBR with a top PCM. First experimental results show a high Q-factor (around 2000) compatible with a laser regime. We finally demonstrate in this paper a vertical-cavity Fabry-Perot filter with ultimate compactness, associating two PCMs.

By integrating soft-lithography-based nanofluidics with silicon nanophotonics, we demonstrate dynamic, liquid-based addressing and high &Dgr;n/n (~0.1) refractive index modulation of individual features within photonic structures at subwavelength length scales. We show ultracompact tunable spectral filtering through nanofluidic targeting of a single row of holes within a planar photonic crystal. We accomplished this with an optofluidic integration architecture comprising a nanophotonic layer, a nanofluidic delivery structure, and a microfluidic control engine. Variants of this technique could enable dynamic reconfiguration of photonic circuits, selective introduction of optical nonlinearities, or delivery of single molecules into resonant cavities for biodetection.

Nanofibers from symmetrically and unsymmetrically functionalized p-quaterphenylenes are fabricated by a bottom-up process on muscovite mica. The symmetrically functionalized p-quaterphenylenes emit intense, polarized blue light after unpolarized UV-excitation. Upon implementing electron push-pull functional groups like chlor and methoxy groups to the molecular building block new properties of the nanoaggregates have been generated: the nanofibers exhibit increased non-linear optical properties, acting, e.g., as frequency doublers after excitation with NIR femtosecond laser pulses. Depending on the growth conditions the chloro-methoxy-p-quaterphenylene forms either parallel nanofibers or nano-branches on a muscovite mica substrate, adding another degree of freedom for the design of, e.g., resonator structures.

The integration of hollow anti-resonant reflecting optical waveguides (ARROWs) with vapor cells on silicon chips provides a compact platform for a number of optical applications, including the study of quantum coherence effects such as electromagnetically induced transparency and single-photon nonlinearities, as well as frequency stabilization standards. The use of hollow waveguides allows for light propagation in low index (vapor) media with compact mode areas. ARROWs make particularly attractive waveguides for this purpose because they can be interfaced with solid core waveguides, microfabricated on a planar substrate, and are effectively single mode. ARROW fabrication utilizes an acidremoved sacrificial core surrounded by alternating plasma deposited dielectric layers, which act as Fabry-Perot reflectors. A demonstration platform consisting of solid and hollow core waveguides integrated with rubidium vapor cells has been constructed. Rubidium was used because it is of particular interest for studying quantum coherence effects. Liquefied rubidium was transferred from a bulk supply into an on-chip vapor cell in an anaerobic atmosphere glovebox. Optical absorption measurements confirmed the presence of rubidium vapor within the hollow waveguide platform. Coherence dephasing in the small dimensions of the ARROW (quantum coherence effect) can be addressed by adding a buffer gas and passivation coatings to the ARROW walls.

In this study, the signal-to-noise ratio of a glass-based guided-wave optical microphone was successfully improved by both increasing sensitivity and reducing noise. The optical microphone has a square diaphragm as a pressure-sensitive structure and a straight single-mode waveguide across the diaphragm. Sensitivity of the microphone and resonance frequency of the diaphragm are dependent on the area and thickness of the diaphragm. In this study, in order to increase sensitivity, the diaphragm dimensions were enlarged from 16 mmx16 mmx0.15 mm in the previous study to 20 mmx20 mmx0.15 mm. According to theoretical calculations, the phase sensitivity and resonance frequency were 2.5 mrad/Pa and 3.4 kHz for a 20 mmx20 mmx0.15 mm diaphragm, respectively. The sensitivity was theoretically expected to be twice as high as that in the previous study. To reduce noise, a bandpass filter with passband from 300 Hz to 3 kHz was employed. After fabrication of the optical microphone, sound pressure, ranging from 100 to 122 dB-SPL, was applied to the microphone with a frequency of 1 kHz. The measured output of the optical microphone was almost proportional to the sound pressure, and the minimum detectable sound pressure level of the microphone was experimentally evaluated to be 100 dB-SPL.

The fabrication and characterization of the p-i-n optical waveguide modulators on silicon-on-insulator (SOI) substrate were demonstrated. The modulation was based on the mechanism of carrier injection, or plasma dispersion effect. The corresponding p and n regions were defined in both types of silicon substrates (conventional p-doped and highly resistive SOI substrates with respective resistivities of &rgr;~7-10&OHgr;-cm and &rgr;~7000-10000&OHgr;-cm) using the spin-on-dopant (SOD) technique. The SOD diffusion process was conducted at 900-1000°C in nitrogen ambient. The diffusion time and temperature, and the resistivity of SOI substrate used were the primary parameters dictating the resultant dopant concentrations and diffusion depths. For the modulators fabricated with various waveguide widths and electrode lengths, the corresponding modulation index was enhanced in response to an increase in the electrode (or modulation) length and/or a decrease in waveguide width. The highest modulation index of ~4.15% was successfully achieved for a silicon p-i-n waveguide modulator with 5&mgr;m,wide waveguide and 7mm-long modulation electrode.

We report the fabrication and characterization of broad emission linewidth GaAs/AlGaAs quantum-well based superluminescent diodes. A photon absorption section and an optical amplifier sections are monolithically integrated on the device to suppress feedback oscillation and to amplifier the optical power, respectively. The device emitters at 850 nm peak wavelength, and exhibits a broad bandwidth of 65 nm, output power > 3.5 mW, and a spectral ripple of 0.5 dB at 20^oC under continuous wave operation.

A novel design of multimode interference coupler with deeply etched air trenches at the boundary of the multimode section is proposed for photonic integrated circuitry on low-index-contrast materials. The device length decreases from 820 microns to 750 microns for a 1X8 polymer multimode interference coupler. Due to the enhanced optical confinement, the optimized coupler with air trenches experimentally achieved 0.28/0.23dB reduced insertion loss, 2.16/2.34dB improved contrast ratio for TE and TM polarization, compared with conventional multimode interference coupler. The device entirely covers the wavelength range of both C-band and L-band, which is sufficient for broad band communication.