This PDF file contains the front matter associated with SPIE Proceedings Volume 7221, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Advanced Photonic Integrated Circuits (PICs) have changed the way capacity is added to optical networks. This paper outlines the operational challenges of scaling WDM optical networks to support Internet growth rates using traditional approaches. It describes the advantages PIC-based solutions offer in terms of size, simplicity, power consumption, and reliability. Future directions enabled by advanced photonic integration are considered.

In this paper, we report the theoretical study of polymer-based photonic crystals for laser beam steering which is based on the superprism effect as well as the experiment fabrication of the two dimensional photonic crystals for the laser beam steering. Superprism effect, the principle for beam steering, was separately studied in details through EFC (Equifrequency Contour) analysis. Polymer based photonic crystals were fabricated through double exposure holographic interference method using SU8-2007. The experiment results were also reported.

We present a concept for an artificial optical skin, a flexible foil in which a novel type of optical force sensing elements is integrated. The principle relies on the change in coupling between two arrays of crossing polymer waveguides separated by a thin layer of soft silicone. When the exerted pressure is increasing, the distance between the waveguides decreases and consequently power is transmitted from one to another. A process flow to produce a proof of principle demonstrator with arrays of Truemode^TM waveguides embedded in silicone is described. In a second approach also the waveguides are fabricated in silicone using an embossing technique.

We demonstrate single RF beam transmission and reception of an X-band phased array antenna using highly dispersive photonic crystal fiber (PCF) based true-time-delay (TTD) lines. The dispersion coefficient of the fabricated fiber is as high as -600ps/nm/km at a wavelength of 1545nm. Coupling between a dispersion shifted fiber (DSF) and the fabricated PCF is performed by using an ultra high numerical aperture (UHNA) intermediate fiber, which helps in achieving a good coupling efficiency and keeping the insertion loss of the delay lines to under 3.5dB. Using the PCF-TTD network, we report the transmission of 8.4GHz signal at 7.4⁰ and 12GHz signal at 21.2⁰ by tuning the laser wavelength to 1547.72nm and 1552.52nm respectively. Single beam receiving capability is also demonstrated by accurately detecting 8.4GHz signal coming from -7.4⁰ and 12GHz signal coming from -21.2⁰ by tuning the wavelengths to 1547.72nm and 1552.52nm respectively..

Optical technologies have changed the way people live since centuries, and the pace of knowledge creation and implementation has strongly increased in the recent past. Prominent examples of recent change include the speed with which information can be exchanged, allowing delay-free intercontinental communication, and the advent of the broadband internet. The conception of planar waveguide optics has already ignited fundamental and manufacturing research decades back, and its proclaimed uses were manifold, including data communication, bio analytics, or illumination. The advances in waveguide optics have also generated many approaches to integrate optical technology into packaging technology using fabrication methods known from the semiconductor or the printed circuit board (PCB) industry. These technologies allow planar integration of optical waveguides and support the miniaturization of integrated systems. With the first experiments dating back to the 1970's, the performance of planar integrated optical systems has risen from proof-of-principle to a point where it is becoming increasingly appealing for many applications to use planar integrated optical technology. A review of the state-of-the-art in integration technologies is given and the prospectus for the use of integrated PCB based optical links is assessed and favorable conditions for successful implementation are proposed.

Recently, Nissan Chemical Industries, LTD, developed the photo-induced refractive index variation sol-gel materials, in which the refractive index increases from 1.65 to 1.85 by ultra-violet (UV) light exposure and baking. The materials enable us to fabricate high-index-contract waveguides without developing/etching processes and strong-lightconfinement self-organized lightwave network (SOLNET). Therefore, the materials are expected promising for nanoscale optical circuits with self-alignment capability. Nano-scale optical circuits with core thickness of ~230 nm and core width of ~1 μm were fabricated. Propagation loss was 1.86 dB/cm for TE mode and 1.89 dB/cm for TM mode at 633 nm in wavelength, indicating that there were small polarization dependences. Spot sizes of guided beams along core width direction and along core thickness direction were respectively 0.6 μm and 0.3 μm for both TE and TM mode. Bending loss of S-bending waveguides was reduced from 0.44 dB to 0.24 dB for TE mode with increasing the bending curvature radius from 5 μm to 60 μm. Difference in bending loss between TM and TE mode was less than 10%. Branching loss of Y-branching waveguides was reduced from 1.33 dB to 0.08 dB for TE mode, and from 1.34 dB to 0.12 dB for TM mode with decreasing the branching angle from 80° to 20°. These results indicate that the photoinduced refractive index variation sol-gel materials can realize miniaturized optical circuits with sizes of several tens μm and guided beam confinement within a cross-section area less than 1.0 μm² with small polarization dependences, suggesting potential applications to intra-chip optical interconnects. In addtion, we fabricated self-organized lightwave network (SOLNET) using the photo-induced refractive index variation sol-gel materials. When write beams of 405 nm in wavelength were introduced into the sol-gel thin film under baking at 200°C, self-focusing was induced, and SOLNET was formed. SOLNET fabricated by low write beam intensity exhibited strong light confinement. Furthermore, SOLNET was found to be drawn automatically to reflective portion such as a defect and a silver paste droplet in the sol-gel thin film during SOLNET formation, indicating that reflective SOLNET is formed. The results suggest that the photo-induced refractive index variation sol-gel materials can provide self-alignment capability to the nano-scale optical circuits.

Optical lines using polymer materials fabricated on an organic substrate with metal lines and pads are proposed to realize fully optical interconnections among high performance LSIs. This optical line enable transmit high speed optical signals not only on a plane surface but to vertical direction. It has following four particular portions; (1) Curved parallel optical waveguide; (2) 45 degree reflection mirror; (3) Optical via hole with coaxial structure; (4) Optical joint between package and board. The optical line characterized by transmission loss and passed through eye diagram, and good optical signal transmission is confirmed to really use for optical interconnection between LSIs. Then on-board optical signal transmission is demonstrated by that VCSEL and PIN-PD are assembled using flip-chip technology on a circuit board with other electric devices of driving circuit, and also package-to-board optical joint are demonstrated by passing through solder reflow process.

Photonic integration significantly reduces power consumption, cost, and size while it enhances reliability and functionality. As modern networking and computing systems require high-performance, low-power, and agile optical communications, photonic integration is emerging as critically important technology for future networking and computing. On the other hand, the main challenge with photonic integration lies in the yield and process-compatibility. This paper reviews the impact of photonic integration in optical communications, discusses the challenges, and probes the future prospects for photonic integration.

We present a peripheral fiber connector to seamlessly interface optical fiber ribbons with polymer optical waveguides integrated on a Printed Circuit Board (PCB). Laser ablation was used to fabricate the optical board, featuring alignment features which enable an accurate positioning of an alignment plate carrying MT-compatible guide pins. These allow for a high-precision in-line mating of commercial MT ferrules with the board-integrated waveguides. The alignment plate is fabricated through deep proton writing (DPW) and is mounted on the PCB by means of steel micro-balls, and is compatible with mass replication technologies.

Nano-photonics and electrical-optical integration are rapidly growing fields with a strong potential for applications in a wide spectrum covering optical sensing, data & telecommunication. Its merit of ultra compactness and planarity becoming a challenge since the periphery remained micro-level and out-of-plane coupling becomes necessary. We introduce new planar optical coupling elements for electrical-optical circuit boards, sensors and nano-devices. The novel photonic packaging technology using thin glass foils bridge the growing field of nano-photonics to the micro-photonic periphery. Innovative features are added to this technique to leverage its generic usage and first experimental results are presented.

We introduce a novel approach to interconnect multiple chips together with a silicon photonic WDM point-to-point network enabled by optical proximity communications to act as a single large piece of logical silicon much larger than a single reticle limit. We call this structure a macrochip. This non-blocking network provides all-to-all low-latency connectivity while maximizing bisection bandwidth, making it ideal for multi-core and multi-processor interconnections. We envision bisection bandwidth up to TBps for an 8x8 macrochip design. And a 5-6x improvement in latency can be achieved when compared to a purely electronic implementation. We also observe better overall performance over other optical network architectures.

Scaling computing systems to Exaflops (10¹⁸ floating point operations per second) will require tremendous increases in communications bandwidth but with greatly reduced power consumption per communicated bit as compared to today's petaflop machines. Reaching the required performance in both density and power consumption will be extremely challenging. Electrical and optical interconnect technologies that may be part of the solution are summarized, including advanced electrical printed circuit boards, VCSEL-array based optical interconnects over multimode fibers or waveguides, and singlemode silicon photonics. The use of optical interconnects will play an ever-larger role in intrasystem communications. Although optics is used today primarily between racks, it will gradually migrate into backplanes, circuit cards, and eventually even on-chip. Keywords: optical interconnects, supercomputers, exascale,

The "vanishing-core" tapered coupler is an all-fiber device that efficiently couples light between a standard low-numerical- aperture (NA) waveguide, such as a standard silica fiber, and a high-NA waveguide or device with a dissimilar mode field profile, such as a planar waveguide or laser diode. The coupler is comprised of a central core surrounded by a concentric secondary core for low-NA coupling on one side of the device. The central core effectively disappears on the tapered end of the device. Light escaping the "vanishing-core" at the tapered end of the fiber is confined in the secondary core by the surrounding cladding for high-NA coupling. This lens-less, low-insertion-loss solution obviates the need for a significant air gap between coupled components required in lensed fibers and thereby enables the use of index matching compounds. The all-fiber design also facilitates polarization selective and polarizing coupling and provides a path towards a high density of passively aligned interconnects.

Two kinds of optical transmitter (Tx) modules using an 1310 nm long-wavelength and an 850 nm short-wavelength 4-channel VCSELs have been fabricated and characterized for comparison. 4-channel VCSEL driver has been fabricated by a CMOS 0.18 μm process and used in common for the fabrication of both modules. Both of the modules showed less than 1 x 10^-12 of bit error rates (BERs) and clear eye openings at the speed of 2.5 Gbps and 3. 5 Gbps. 3dB bandwidths of the two different Tx modules of 850 nm and 1310 nm VCSELs are 3.76 GHz for 850 nm VCSEL and 3.80 GHz for 1310 nm VCSEL. The optical crosstalks of the both transmitter modules are less than -50 dB in common. Crosstalk evaluation of the two optical interconnection systems using these two Tx modules shows that the application of the 1310 nm wavelength VCSEL as well as 850 nm wavelength VCSEL for the optical interconnections is expected to be possible.

Formulations containing silicon-based polymers have been used for the formation of planar waveguides on flexible substrates. The substrate of choice is compatible with the flexible waveguide and is made of materials commonly utilized in the printed circuit board industry. When the flexible waveguide material is combined with the chosen substrate using processes compatible with printed circuit board manufacturing techniques, the resultant optical interconnects display sufficient flexibility, low optical loss (<0.05 dB/cm at 850 nm), and high reliability.

This paper presents an overview of multimode waveguides and waveguide components formed from siloxane polymer materials which are suitable for use in optical interconnection applications. The components can be cost-effectively integrated onto conventional PCBs and offer increased functionality in optical transmission. The multimode waveguides exhibit low loss (0.04 dB/cm at 850 nm) and low crosstalk (< -30 dB) performance, large alignment tolerances and negligible mode mixing for short waveguide lengths. Error-free data transmission at 10 Gb/s over 1.4 m long waveguides has been successfully demonstrated. Waveguide crossings exhibit very low excess losses, below 0.01 dB/crossing, and excellent crosstalk performance. Low loss is obtained for waveguide bends with radii of curvature larger than 8 mm and 6 mm for 90° and S-shaped bends respectively. High-uniformity splitting is achieved with multimode Y-splitters even in the presence of input misalignments. Y-combiners are shown to benefit from the multimode nature of the waveguides allowing low loss combining (4 dB for an 8×1 device). A large range of power splitting ratios between 30% and 75% is achieved with multimode coupler devices. Examples of system applications benefiting from the use of these components are briefly presented including a terabit capacity optical backplane, a radio-over-fibre multicasting system and a SCM passive optical network.

Nanostructured materials are intensively investigated due to their wide range of physical and chemical properties which result in a large variety of applications. From an industrial point of view, emphasis has not only to be on materials performance and on control of their properties, but also on cost reduction either for the materials, the processes, or for both. Materials are searched for which enable different processing technologies, feature sizes and shapes as well as an integration up to a centimeter scale. The combination of low-cost materials with tunable material parameters such as low optical absorption, tunable refractive index, good processability as well as high chemical, thermal and mechanical stability, is very attractive for integrated optical applications. A particular class of low-cost nanoscale materials which fulfills these requirements is the class of inorganic-organic hybrid polymers (ORMOCER^(R)s¹) which are synthesized by catalytically controlled hydrolysis/ polycondensation reactions, resulting in storage-stable, photo-sensitive resins. The material properties, for example refractive index or optical absorption, can be widely varied by choice of alkoxysilane precursors or synthesis conditions such as catalysts or solvents. In addition, the material properties can also be significantly influenced by the technological processing conditions. For example, the degree of organic cross-linking can be adjusted by variation of UV initiator kind and concentration, or by various exposure doses. This, consequently, is directly correlated to the refractive index. The impact of processing conditions on the refractive index was investigated by FTIR spectroscopy and refractive index measurements. The refractive indices are correlated to the material's degree of organic cross-linking, and application examples will be given.

We report on various single and multimode channel waveguide structures fabricated via microtransfer molding and microfluidic techniques. These soft lithographic fabrication techniques can result in an inexpensive and rapid turnover of various types of channel waveguide structures and general integrated optic devices. It may be particularly useful for production of waveguides on user-desired surface substrates including those of a curved or distorted nature. Microscopic cross-sectional images for both single and multimode waveguides are obtained and compared between the two fabrication methods. The novel microfluidic technique results in superior waveguide formation and improved propagation loss performance.

The limits to silicon modulator bandwidth and power consumption are explored. Traditional electrical interconnects provide insufficient bandwidth (~10Gb/s) and consume far too much power (~10pJ/bit) for future high performance computing applications. Microphotonic devices closely integrated with advanced CMOS electronics have the potential to dramatically lower intra- and inter-chip communication power consumption while greatly increasing available bandwidth. Our recent results confirm the significant advantages offered by microphotonic communication links. We have broken the 100fJ/bit barrier by demonstrating 4-micron diameter microdisk modulators achieving 10Gb/s data transmission with a bit-error-rate below 10^-12 and a measured power consumption of only 85fJ/bit. Through rigorous simulation and experimentation, we consider ultimate limits to silicon modulator bandwidth and power consumption.

We demonstrate active control of propagating surface waves on a mid-infrared extraordinary optical transmission grating. The surface waves are excited at the interface between a GaAs substrate and a periodically patterned metal film using a dual wavelength quantum cascade laser. The spectral properties of the laser and the transmission grating are characterized by Fourier Transform Infrared spectroscopy. In addition, the far-field emission from excited surface waves at the metal/GaAs interface is studied using a novel spatial and spectral imaging technique. By actively controlling the optical properties of the grating, we demonstrate the ability to control the coupling of incident coherent radiation to surface waves on the grating. With increased tunability of the grating, directional control of excited surface waves should be achievable. These results suggest that the development of actively tunable plasmonic structures could result in plasmonic routers and switches for interconnect or sensing applications.

We present a new class of low-loss integrated optical waveguide structures as CMOS-compatible industrial standard for photonic integration on silicon or glass. A TriPleXTM waveguide is basically formed by a -preferably rectangular- silicon nitride (Si₃N₄) shell filled with and encapsulated by silicon dioxide (SiO₂). The constituent materials are low-cost stoichiometric LPVCD end products which are very stable in time. Modal characteristics, birefringence, footprint size and insertion loss are controlled by design of the geometry. Several examples of new applications will be presented to demonstrate its high potential for large-scale integrated optical circuits for telecommunications, sensing and visible light applications.

It has been previously published how, using two separate Vertical-Cavity-Surface-Emitting-Lasers (VCSELs), a miniature laser-Doppler interferometer can be made for quasi-three-dimensional displacement measurements. For the use in consumer applications as PC-mice, the manufacturing costs of such sensors need to be minimized. This paper describes the fabrication of a low-cost laser-self-mixing sensor by integrating silicon and GaAs components using flip-chip technology. Wafer-scale lens replication on GaAs wafers is used to achieve integrated optics. In this way a sensor was realized without an external lens and that uses only a single GaAs VCSEL crystal, while maintaining its quasi-three-dimensional sensor capabilities.

We present a new approach to wide angle optical beam steering based on nano-membrane-based phased array structures with unequally spaced elements. In our approach, the array elements are positioned in such way that grating lobes associated with different sub-arrays do not overlap. Therefore, we reduce the side-lobe-level of the array radiation pattern and at the same time we can avoid the optical coupling between adjacent waveguides by relaxing the half-wavelength spacing requirement for large angle beam steering. By optimizing the optical waveguide structure for the maximum full-width at half-maximum of the single radiator's radiation pattern we discuss the optimum performance achievable using the Unequally-spaced Waveguide Arrays.

High-power, packaged diode-laser sources continue to evolve through co-engineering of epitaxial design, beam conditioning and thermal management. Here we review examples of improvements made to key attributes including reliable power, brightness, power per unit volume and value.

Compact high power laser light sources emitting a single frequency with diffraction limited beams in continuous wave (CW) operation are required for many applications including frequency conversation. We present a hybrid integrated package consisting of a distributed feedback ridge-waveguidemaster-oscillator power- amplifier mounted on an AlN micro-optical bench with a CW output power of 4.5W at 976 nm having a beam propagation ratio of M² < 2 (including second order moments). The longitudinal mode emission has a linewidth of λ < 10 pm. Due to thermal decoupling the wavelength shift is nearly independent of the amplifier pump-current.

In any assembly, where two devices are to be precisely connected, the integrity and quality of this connection (bond) is a key factor in the overall performance of the final device. In micro-assembly and optoelectronics, this connection is typically gold to gold, solder, or epoxy bond. The chemistries can vary, but the critical issues remain the same. Placement accuracy is an important consideration and is normally the starting point for most bonding applications. In optoelectronics, the placement of a laser will be critical to its performance. Often edge-to-edge alignment is needed, which requires optical resolution of one micron or better. Laser bars have the added challenge of requiring this high optical resolution, but over distances of more than 10 millimeters. Equally important is what happens after a device has been aligned to a substrate ready for bonding. Both thermal and force parameters must be considered. Voiding in the material or oxidation during the soldering process all need to be minimized. This paper will look at recent innovations to improve the final bond. These innovations include temperature ramp rate, heated inert atmosphere and component uniformity. These processing techniques are particularly applicable in optoelectronics applications, such as laser diode and laser bar bonding.

Diode lasers are playing an increasingly important role in various applications, including pump sources for solid-state and fiber lasers, optical communications, printing systems, optical data storage, and electro-optical sensors. Compact package size, lower cost, and emission spectra from UV to IR, combined with conversion efficiencies in excess of 50% makes diode lasers a preferred choice over several other laser types. High-power diode laser beams are multimode, and can be described as an incoherent superposition of the limited number of individual lateral modes contained in the beam. The ability to shape and control the output beam characteristics of diode lasers requires establishing an accurate model of the multimode laser beam. We propose a general multimode laser beam model based on incoherent superposition of apodized Hermite-Gaussian modes to describe the spatial intensity distribution and propagation characteristics of the high-power diode laser beams. Free-space propagation characteristics of high power diode laser beams are compared with propagation characteristics of propagation invariant Hermite-Gaussian beams. Diffraction effects caused by micro-optics components will be presented, which show a significant impact on the intensity distributions of the individual lateral modes composing the beam, as well as on the multimode laser beam spatial distribution as a whole.

To reduce efforts for optical assembly, we developed the reflective self-organized lightwave network (R-SOLNET). In R-SOLNET, optical devices with wavelength filters on their core facets are distributed in photo-induced refractive-index increase (PRI) media such as photo-polymers. Write beams from some devices and reflected write beams from the wavelength filters of the other devices overlap. In the overlap regions, the refractive index increases, pulling the write beams to the wavelength filter locations (the "pulling water" effect). By self-focusing, self-aligned optical waveguide networks are formed between the optical devices. Simulations based on the finite difference time domain method revealed that self-aligned optical waveguides of R-SOLNET are formed between cores with 2-μm and 0.5-μm widths including Y-branching waveguides. Experiments demonstrated that R-SOLNET is formed between an optical fiber and a micro-mirror placed with ~800-μm gap. For angular misalignment of 3o between the optical fiber and the micro-mirror, a bow-shaped R-SOLNET was observed. For lateral misalignment of 30 μm, an S-shaped R-SOLNET was observed. These results suggest that by placing reflective elements in PRI media, optical waveguides can be lead to the elements to form R-SOLNET. This enables self-aligned optical couplings for optoelectronic boards, intra-chip optical circuits, VCSELs/PDs, optical switches, and so on.

Optical interface multichip modules promise to alleviate the bottlenecks of electrical interconnection. Two kinds of optical transmitter multichip module were fabricated for optical printed circuit board (OPCB) based interconnections for performance analysis. Each of the modules consist of 1 x 4 bottom-emitting VCSELs flip-chip bonded on a CMOS driver array IC for optical interconnection; among them one is an 850nm short-wavelength and the other is a 1310nm long-wavelength VCSEL. The short- and long-wavelength VCSELs have -3dB bandwidth of about 3.6 GHz and 2.6 GHz, respectively. Four-channel driver array which has been fabricated in a 0.18μm Si-CMOS technology requires 1.8V of power supply, is used for the both multichip transmitter modules. Short- and long-wavelength multichip modules are bumped with Au/Sn solder and gold stud bump wire respectively using the flip-chip bonding technology. The multichip modules have a dimension of 1.1mm x 1.2mm x 0.5mm for the four channels. The multichip module employing flip-chip bonding technology reduces unwanted crosstalk due to bond wires. The two modules showed BER less than 10^-12 and clear eye openings at 2.5 Gbps. We measured the frequency response and crosstalk of long-wavelength multichip module and will compare them with the short-wavelength multichip module to evaluate which module is preferable for the optical interconnection applications on optical PCBs.

Photonic crystal (PhC) is a new class of material which has a periodic modulation of dielectric constant. PhC will exhibit superprism effect, negative refraction and self-collimating ultra-low group velocity due to the anomalous dispersion of PhC . We can utilize the characters of photonic bandgap(PBG), defect band, pass band and band edge to control the propagation of the light .This research was to investigate the refraction and superprism effect of photonic crystals .The study background and the basic theories of photonic crystals were introduced. The refraction of photonic crystals and superprism effect were discussed with the correlating knowledge and the computing methods. A new theory of light refraction at the surface of a photonic crystal was put forward and simulated. The simulating results of this application for negative refraction and superprism effect were demonstrated by some simulating figures. These may bring about important potential applications in some areas. Keywords: photonic crystal, superprism effect, simulation

Currently, free space optical interconnect systems can be severely limited by optical crosstalk that can arise due to unfocused systems and misalignments between transmitter and receiver elements. To address this limitation, space-time codes, largely developed for radio frequency channels, are adapted for use in a free space optical interconnect system. We have extended space-time coding for a 4x4 optical channel based on on-off keying that uses real intensity-based signals. These codes improve system performance by taking advantage of the optical crosstalk in a system composed of multiple transmitters and receivers. Data is encoded by space-time codes based on orthogonal designs and is split into four streams that are simultaneously transmitted using four transmitters with the same wavelength. The received signal at each of the four optical receivers is a superposition of the transmitted signals with the addition of noise. Decision metrics are calculated making use of the received signals and the optical path gains which are determined using channel training. These metrics, in conjunction with maximum likelihood decoding, decouple the individual signals transmitted from different transmitters. Use of the modified codes based on orthogonal designs allows for simple maximum likelihood decoding based on minimum Euclidean distance. Simulated results show that our system can achieve a low BER on the order of 10^-6 even in case of a substantial misalignment between the transmitter and receiver.

Robust and efficient optical coupling from laser-to-fiber and from fiber-to-detector is an important consideration for loss limited optical data links. Standard chip scale package process flow used by the semiconductor industry is based upon machine vision assisted "pick-and-place" die attach and wirebonding operations. To realize scalable heterogeneous integration of optical elements, mass production must be done within the framework of existing manufacturing equipment and avoid active opto-mechanical alignment steps. This publication reports on the performance of a set of a refractive, hemi-aspheric, nonimaging optical concentrators that are simple and amenable to standard package integration flow with passive alignment. A set of lenses are made by single-point diamond-turning and injection molding of unfilled polyetherimide, which is relatively transparent at the link operating wavelength of 850 nm. The goal of the design is to balance the absolute coupling at optimum alignment with wide margins for angular and linear misalignment.