This PDF file contains the front matter associated with SPIE Proceedings Volume 6899, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

We describe our R & D on optoelectronic packaging technologies such as the optical backplane utilizing 300 pieces of the high index contrast fine multimode fibers and the low-cost and high-density OE-conversion parallel link modules operating at 10 Gbps /ch for less than 1 m regime applications. Combination of the developed backplane and the modules implies potential of 3 Tbps aggregate throughputs at the board-to-board level optical interconnections. We also introduce novel component technologies for low-cost and high-density optical coupling between optical devices. These technologies include the monolithic two wavelengths twin VCSELs and easy self-alignment coupling technology capable of alleviating difficulties for optics penetration inside the box.

This paper presents the latest progress toward fully embedded board level optical interconnects in the aspect of optical bus architecture design, waveguide fabrication and device integration. A bidirectional optical bus architecture is designed and can be fabricated by a one-step pattern transfer method, which can form a large cross section multimode waveguide array with 45° micro-mirrors by silicon hard molding method. The waveguide propagation loss is reduced to 0.09dB/cm and the coupling efficiency of the metal-coated reflecting mirror is experimentally measured to be 85%. The active optoelectronic devices, vertical surface emitter lasers and p-i-n photodiodes, are integrated with the mirror-ended waveguide array, and successfully demonstrate a 10 Gbps signal transmission over the embeddable optical layer.

Multilayer optical interconnects offer high interconnection densities and flexible routing schemes. Signals can be routed between the different layers, which can limit the number of cross-overs. In addition, the characteristics of 2D opto-electronic elements can be fully exploited. The alignment between the different optical elements is critical for the performance of the system. Efficient coupling structures are required to couple the light signals between two layers. We propose the use of laser ablated 45° mirrors, which are integrated with the waveguides. Two mirror configurations are proposed: one based on total internal reflection (TIR) and a metallized 45° mirror. A two layer optical structure is presented that contains multimode waveguides and micro-mirrors. The achievable alignment accuracy between the multimode waveguides and micro-mirrors in the two layers is in accordance with the results obtained from a numerical study. Experimental realizations of the mentioned structures and the first results on the loss measurements on the mirrors are presented.

We proposed a novel optical coupling technology for short-reach interconnection (<10m) on flexible polymer waveguides. In order to decrease time and cost of fabrication and assembly, edge-emitting lasers and edge-viewing photodetectors are embedded directly into flexible polymer waveguide in a parallel lithography process. This avoids lenses or angle-reflected components, such as 45° mirrors or volume gratings, which are widely used for VCSEL coupling. Multi-channel optical interconnection can be implemented by passive alignment in a one-time optical lithography process, and no additional expensive components are needed to achieve high coupling efficiency.

In this study, a low-cost (with bare chips) and high (optical, electrical, and thermal) performance optoelectronic system with a data rate of 10Gbps is designed and analyzed. This system consists of a rigid printed circuit board (PCB) made of FR4 material with an optical polymer waveguide, a vertical cavity surface emitted laser (VCSEL), a driver chip, a 16:1 serializer, a photo-diode detector, a Trans-Impedance Amplifier (TIA), a 1:16 deserializer, and heat spreaders. The bare VCSEL, driver chip, and serializer chip are stacked with wire bonds and then solder jointed on one end of the optical polymer waveguide on the PCB via Cu posts. Similarly, the bare photo-diode detector, TIA chip, and deserializer chip are stacked with wire bonds and then solder jointed on the other end of the waveguide on the PCB via Cu posts. Because the devices in the 3D stacking system are made with different materials, the stresses due to the thermal expansion mismatch among various parts of the system are determined.

System integrators are driven by the demands of hybrid module manufacturers to provide machines with a higher degree of system integration while maintaining full process automation at max. throughput and yield. The full automated packaging process involves Pick&Place of several components like photo diode, laser sub-mount, integrated optical chip and PCB. Whereby some components are placed passively supported by vision inspection and some are aligned actively by closing a control loop on nano-scale precision. The system applies adhesive bonding for fixation of the components. The presentation shows how various assembly steps are combined in one machine concept for assembling and qualifying complex hybrid modules. Therefore modern assembly machines relay to special hardware designs i.e. for trays, chucks, motion concepts and calibration systems as well as for software features as data base interfaces, recipe controlled processes and flexible process editor. However beside hardware and software feasibility also necessary device characterisation is an important feature in assembly machines.

A taper coupler with multimode input and single mode output is presented for coupling between edge emitting laser diode and silicon waveguide. The tapered coupler structure is optimized and tolerance for laser diode placement is studied. A typical coupling efficiency of -2dB is achieved from laser diode to silicon waveguide. With tolerance of +/- 4μm laterally or vertically, the variation of the coupling efficiency is about 3dB. The tolerance is large compared with other methods. Tilting angle at laser diode and the small gap between tapered coupler and silicon waveguide also affect the overall coupling. From our studies, horizontal and vertical offsets are more critical for laser diode placement in order to have a good coupling. The new design can be applied to photonics packaging because it will make passive assembly easier by having larger tolerance for packaging compared with the conventional method with lens.

Self Assembly is a promising alternative to conventional pick and place robotic assembly of micro components. Its benefits include parallel integration of parts with low equipment costs. Various approaches to self assembly have been demonstrated, yet demanding applications like assembly of micro-optical devices require increased positioning accuracy. This paper proposes a new method for design of self assembly bonds that addresses this need. Current methods have zero force at the desired assembly position and low stiffness. This allows small disturbance forces to create significant positioning errors. The proposed method uses a substrate assembly feature to provide a high accuracy alignment guide to the part. The capillary bond region of the part and substrate are then modified to create a non-zero positioning force to maintain the part in the desired assembly position. Capillary force models show that this force aligns the part to the substrate assembly feature and reduces sensitivity of part position to process variation. Thus, the new configuration can substantially improve positioning accuracy of capillary self-assembly. This will result in a dramatic decrease in positioning errors in the micro parts. Various binding site designs are analyzed and guidelines are proposed for the design of an effective assembly bond using this new approach.

New surface mount optical coupling solutions for short reach and chip level connection are presented. These miniaturized optical interconnects have advanced micro-optics integrated within fiber connectors, chips and light sources. Interconnect fabrication is compatible with Si CMOS processing, III-V processing and automated surface mount assembly processing. The combination of these fabrication and assembly processing methods enable dramatic cost reductions for optical interconnects.

We have developed a film waveguide which has excellent bending properties. The waveguide can be fabricated by existing exposure/development processes and facilities with a core and a cladding dry film. Based on the bending loss simulation results, we fabricated the film waveguides of which the core-cladding index difference (relative index difference) of the waveguide was 3.1% and were evaluated transmission and bending properties. The propagation loss measured by a cut-back method was 0.15dB/cm at wavelength of 850nm. There was little change in optical loss on a 360-degree bend test with a 2mm radius of curvature. No loss increase and no damage to the film waveguide were observed after MIT folding endurance test more than one hundred thousand times with a 2mm bending radius of curvature at -30, 23 and 85 °C. The film waveguide demonstrated good folding endurance over a wide range of temperatures.

In order to realize ultra-small light modulators for chip-scale optical interconnects, high-performance electro-optic (EO) materials are required. Conjugated linear molecular wires are expected as one of the candidates of the EO materials due to high-carrier-mobility characteristics of their π-conjugated systems. We propose waveguides with conjugated polymers fabricated by the carrier-gas-type organic CVD, which enables the selectively aligned growth and the selective growth of polymer wires. Using poly-azomethine (poly-AM) as the conjugated polymer, the selectively aligned growth and the selective growth are demonstrated experimentally. 4-μm-wide waveguides are formed by the selectively aligned growth, and propagation of light beams of 650 nm in wavelength is observed. Characterization of EO effect and other properties of the poly-AM waveguides is under way.

Light coupling in micro-optic systems is one of the most important and difficult to implement processes, having major impact on the system performance, and requiring significant investment in design, equipment and tooling, and process know-how. While packaging has a dominant share in cost of electro-optical devices, coupling processes may have the highest impact on the yielded cost of the product. In this paper we present a broad spectrum of coupling schemes and approaches that were developed during evolution of photonics and electro-optical instrumentation. Some recent coupling trends geared towards reduction of production and packaging costs will also be discussed.

In this paper, the optical design of 4-channel WDM Transmission Optical Subassemblies (TOSA)/Receiver Optical Subassemblies (ROSA) is reported. The TOSA and ROSA are being developed for uncooled modules for CWDM applications and are compatible with the SFP/SFF form factor TOSA and ROSA. The physical dimension of OSA together with the electronic circuitries is limited to 10×6×5 mm³. The designs of TOSA and ROSA are employed using four thin film filters (TFFs) to select the specific channel wavelength, four 500 μm ball lenses, one 2.5 mm ball lens and a high reflection mirror using folded optical configuration. The optical elements are to be assembled on a SiOB, except the 2.5 mm ball lens. The simulation results are used to estimate the required optical components assembly accuracy. Based on the simulation results, the tolerance requirement for tilting the mirror and first thin film filter is approximately ± 0.2° for the longest optical path namely Channel 4.

With the continued miniaturization and sophistication of current generations of semiconductor devices, it is the limitations of data transfer rates that are beginning to impact system performance. Although conventional pathways continue progressing, researchers are moving toward optical interconnects as a potential solution. Optical interconnection is a promising way to replace existing global or chip-to-chip interconnects in future integrated circuits. In contrast to existing metallic wiring, optical interconnects exhibit smaller distance-related loss or distortion of the signal, no deleterious fringing effects and no heat dissipation in the interconnect itself. Pioneering interconnect schemes are currently being developed using both planar waveguides and fibers to distribute optical signals around printed circuit boards. However, researchers are now attempting to incorporate novel, freespace optical interconnects, which will boost data transfer rates by a factor of a thousand. These systems consist of a number of components including vertical cavity surface emitting lasers (VCSELs), lenses, diffractive optical elements and detectors. Integration of single components into sub-systems will help to minimize the optical system footprint for both on-chip and chip-to-chip interconnects. This paper will present the development of both independent and integrated with VCSELs,static diffractive optical element (DOEs) made of SU8 and prove the feasibility of such an approach. SU8 is a negative tone photoresist, conventionally used for high aspect ratio MEMS-based structures. Recent developments in thin film SU8 along with its low absorption at long wavelengths makes it a suitable material for optical applications. By developing a low cost lithography based process, SU-8 DOEs can be efficiently integrated directly on laser sources with minimal effect to VCSEL performance. This approach could have a significant impact on the creation of next generation optical I/O fabrics.

We examined fast response organic light-emitting diodes (OLEDs) for new applications of visible optical communications. For the practical use in this field, the fast transmission speed of OLEDs is required to be used in many applications, but the low carrier mobility of organic materials and the long fluorescence lifetime (FL) organic emitting materials limit the transmission speed of OLEDs. Therefore, we investigated the influence of the FL on transient properties of photoluminescence (PL), which were evaluated by the frequency dependence of PL intensity excited by a modulated violet laser diode. The FLs of several organic emitting materials were also measured, and we found the clear relationship between the FL and the transient properties of PL intensity. The fastest cutoff frequency of PL intensity was achieved 160 MHz utilizing short FL material, 1,4-bis[2-[4-[N,N-di(ptolyl)amino]phenl]vinyl]benzene. We also investigated another way to increase the transmission speed utilizing a semiconductor-organic multilayer structure, of which ZnS was used as an electron transport layer. The maximum cutoff frequency of this device was achieved 20.3 MHz, while that of the organic multilayer structure was 8.7 MHz at a sine wave voltage of 7 V and a bias voltage of 5 V. This result indicates that the high carrier mobility of the ZnS layer causes the increase in the transmission speed of OLEDs. We demonstrated one institutive demonstrator module of visible optical communications, which consisted of the transceiver module with an OLED and the pen-type receiver module with a photo-diode at a point. The movie files was transmitted at a speed of 230 kbps, when the point of a pen-type receiver module approaches the emitting area of an OLED. Furthermore, the pseudo-random signal with 1Mbps was also transmitted with this visible optical communication system. Such a system enables to connect between transceiver and receiver module without precious alignment because of the large emitting area of OLEDs. So, we think that many people, from children to aged people, are easy to get information from OLEDs without being aware of using optical communications. Furthermore, the communication field is limited near the emitting area of an OLED, resulting in a safe data transmission.

In optoelectronics diode lasers and especially diode laser bars are playing an important role for applications in high power diode lasers as well as diode laser pumped solid state lasers. Inside the manufacturing process of laser bar systems the electro optical test of laser bars is essential to sort out the good parts which fulfil the quality specified. An electro optical test station was developed and integrated which performs the so called LIV test. The voltage vs. current, the intensity vs. current and spectral distribution of each of the emitters can be measured and logged. The results will be evaluated and according to flexible parameter management the decision about acceptable quality is supplied automatically. The data will be processed by data base capabilities, hence this the system can be integrated into the general manufacturing data management. Due to the modular design of the test station it is capable to be integrated in a fully automated visual inspection and test system suitable for mass production as well as in a semi automated system which fits more the demands of R&D applications. The design of the test station, test results and a critical discussion of advantages will be presented.

An optical sub-assembly of MUX/DEMUX where optical devices are hybrid-integrated on a silicon optical bench (SiOB) using a low cost passive alignment method was reported. A tight tolerance of positional and tilting angular accuracy is required for optical devices attachment in order to maximize the coupling efficiency. The critical positioning transverse to the optical axis merely depends on the symmetry, and accuracy of the position and shape of trenches. Any inaccuracy primarily affects the non-critical positioning, i.e., z-axis & θz, in the direction along the optical axis; misalignment accumulated and causes undesired insertion loss. All the piece parts, i.e., mirror, thin-film filters (TFFs), ball lens, SiOB etc., have a defined tolerance in their dimensions and surfaces which increases the challenge in achieving high placement accuracy along the optical axis. The effects from these inherent inaccuracies of the position and shape of trenches and piece parts could be minimized by improve the bottom flatness, and proper procedure selection. Misalignment at each axis, e.g. x-, y-, z-, θx, θy & θz was characterized and its effect to the coupling efficiency was discussed.

Silicon Optical Bench (SiOB) is a popular solution for passive assembly of optical module. In order to realize an optical transmitter or receiver module, it is necessary to integrate high frequency optoelectronic components such as signal photodiodes (PD) or laser diodes (LD) onto the SiOB. In this way, the module's electrical and optical performances can be further improved, and a higher degree of miniaturization can be achieved. The challenge for this integration is not only on the assembly accuracy for the LD and PD, it required the design of low loss electrical interconnect at high frequency. However, the standard silicon substrate used in the SiOB has a high electrical loss especially at high frequency. This imposed a limitation on the electrical interconnection length between the optoelectronic components and their I/O interfaces. It is proposed here to design the electrical interconnection using a layer of SiO₂ sandwiched between two layers of metal layer. Simulations have demonstrated that by varying the thickness of the SiO₂ layer, an optimum electrical performance can be achieved.

In this work, three approaches are proposed to implement high-speed 850-nm optical receivers fully in standard bulk 0.18 μm silicon (Si) CMOS technology. In the first approach, the lateral p-i-n photodiode (PD) with designed block well to limit the photocarriers being generated from the laterally depleted regions is integrated in optical receiver. The receiver consists of TIA, LA, offset-cancellation-network and buffer to provide a conversion gain of 110 dBΩ and data rate of 2.5 Gbps operation. In the second receiver, the spatially modulated PD (SMPD) with -3 dB bandwidth of 590 MHz is integrated in optical receiver with the extra adaptive equalizer and demonstrates a data rate of 3.125 Gbps. Finally, the proposed novel structure of PD eliminates the slow diffusion photocarriers by using body contact design to create a new current path under the PD. A bandwidth of 2.8 GHz with 100 % improvement in PD is obtained. The eye diagrams of PD with cable connected amplifiers at 2.5 Gbps, 4 Gbps and 5 Gbps are demonstrated. Furthermore, the optical receiver's optical-electrical (O-E) conversion bandwidth is also increased from 3.6 GHz to 4.3 GHz. To our knowledge, these are the highest O-E conversion bandwidth of the PD and optical receiver ever reported by using the standard bulk 0.18 μm Si CMOS technology.

We experimentally demonstrate a novel slot photonic crystal waveguide for guiding light with low group velocity in a 100-nm-wide low-index region. The unique optical property and structural features of the slotted photonic crystals best match the requirements for active material-based silicon devices. We integrate the novel photonic crystal waveguide with a multimode interference-based coupling structure and measure a 20dB efficiency enhancement compared with direct coupling configuration. The measured transmission spectra are in good agreement with simulated band diagram.

There is an increasing demand for tunable lasers in telecommunications networks for test equipment, optical components and other applications. In DWDM systems, multiple data streams propagate concurrently on a single mode fiber. DWDM networks are based on a DFB lasers operating at a wavelength defined by ITU wavelength grid. Statistical variations associated with the manufacture of DFB laser results in yield losses. Continuously tunable external lasers are developed to overcome the limitations of DFB lasers. Various laser tuning mechanisms are being explored to provide external cavity tunable lasers to provide a stable single mode output. The packaged tunable laser source (TLS) for DWDM network also need to include several optical elements for isolation and data modulation like collimator, focusing lens, fiber pigtail, a modulator and output fiber segment. In this publication, we propose a novel semi integrated miniature high frequency tunable laser design based on Silicon Optical Bench (SiOB) concept. One of the mirrors is a movable MEMS structure changing the optical path length. We propose micro optical design between laser diode and the MEMS mirror for efficient optical coupling and side mode suppression. We also present the compatibility between the optical coupling and MEMS actuation range. We present the coupling efficiency results over the tuning range. We also propose a method of monitoring the output power of the tunable laser using waveguide coupler structures which are integrated in the silicon wafer and method of packaging in a miniature package compatible to the industry standard form factor.

A multi-channel gated-oscillator-based clock and data recovery (CDR) circuit for chip-to-chip optical link applications is proposed and designed. The key components of the proposed CDR are a charge-pump phase-locked loop (CPPLL), gated-oscillators, and decision circuits. The proposed multi-channel CDR has the center frequency of gated oscillator around 2.5 GHz; however, the input data rate of each channel can be up to 3.2 Gbps. It achieves an acquisition time of 1 μs. The power dissipation is 18.27 mW for the CPPLL and 21.21 mW for each channel of the CDR. The chip size of the CPPLL is 800×750 µm², while that of each channel of the CDR is 200×250 μm² in a 0.18 μm CMOS technology.

The high cost of optoelectronics components typically used for long-haul communication is prohibitive in the Fiber to the Home (FTTH) and Passive Optical Networks (PONs). One method of cost reduction is through the reducing the cost of the electronics in the transceiver and reducing the packaging cost. We report the development of low-cost 2.5-Gbps optical transceiver for Gigabit Passive Optical Network (GPON) using CMOS driver ICs and chip-on-board assembly method. We developed the Laser Diode Driver (LDD), Trans-impedance Amplifier (TIA), Limiting Amplifier (LA) and the Clock and Data Recovery (CDR) using CMOS technology for short reach application and developed the burst mode version of the ICs for PON applications. The ICs are designed in house and fabricated on a standard CMOS 8" wafer with 0.18μm technology. The devices operate at 1.8V and are low power in nature, thus reducing the demand on power dissipation. The transceiver consists of an un-cooled and direct modulated laser diode driven with a LDD, a high speed PIN photo-diode with amplifier and CMOS ICs. The bare CMOS ICs are attached on a transceiver substrate that is compliant with the small form-factor pluggable (SFP) package multisource agreement (MSA) and coupled to a 1310nm FP laser TOSA and a PIN ROSA with LC connector. The integrated transceiver is characterized up to 2.5-Gbps. In this publication, we present the detail of the module development, assembly methods and performance characterization at 1310nm.

The IBM Terabus program has developed parallel optical interconnects for terabit/sec-class chip-to-chip communications through printed circuit boards with integrated optical waveguides. 16 TX + 16 RX channel transceiver "Optomodules" were assembled and fully characterized, with fiber-coupled full links operating up to 15 Gb/s, for an aggregate bi-directional data transfer rate of 240 Gb/s. Furthermore, we have demonstrated a complete link between two Optomodules through polymer waveguides on a printed circuit board, with all 32 uni-directional links operating error-free at 10Gb/s, for a 160 Gb/s bidirectional aggregate data rate. This is the fastest, widest, and most integrated multimode optical bus ever demonstrated.

The following paper presents research on the manufacture of circuit boards with buried optical waveguides using thin-glass sheets (display glass), which represents a further development of earlier research on buried optical waveguide substrates using polymer. An ion-exchange process was developed to manufacture the waveguides in thin-glass sheets, thereby eliminating the necessity of mechanically structuring the layers. The waveguide properties were simulated and experimentally validated. The circuit board assembly and the concept for the optical coupling from the module to the board and from the board to the backplane are presented. The design and assembly of pluggable electro-optical transmitter and receiver modules is described.

Optical links are well known to present significant advantages over electrical links for very high-speed data rate at 10Gpbs and above per channel. However, the transition towards optical interconnects solutions for short and very short reach applications requires the development of innovative packaging solutions that would deal with very high volume production capability and very low cost per unit. Moreover, the optoelectronic transceiver components must be able to move from the edge to anywhere on the printed circuit board, for instance close to integrated circuits with high speed IO. In this paper, we present an original packaging design to manufacture parallel optic transceivers that are surface mount devices. The package combines highly integrated Multi-Chip-Module on glass and usual IC ceramics packaging. The use of ceramic and the development of sealing technologies achieve hermetic requirements. Moreover, thanks to a chip scale package approach the final device exhibits a much minimized footprint. One of the main advantages of the package is its flexibility to be soldered or plugged anywhere on the printed circuit board as any other electronic device. As a demonstrator we present a 2 by 4 10Gbps transceiver operating at 850nm.

We describe the design and development of a high-speed 8-channel hybrid integrated optical transceiver package with Clock and Data Recovery (CDR) circuits. The package concept has been developed to be compatible with microprocessor package technology and at the same time allow the integration of low cost, high-performance optical components. A 90nm CMOS optical transceiver chip, 850nm 10Gb/s GaAs based vertical cavity surface emitting laser (VCSEL) array and PIN photodiode array are flip-chip mounted on a standard microprocessor Land Grid Array (LGA) package substrate. The CMOS drivers and receivers on the transceiver chip and the optical components (VCSEL and Photodiode arrays) are electrically coupled using a short transmission line routed on the top surface of the package. VCSEL and photodiode arrays are optically coupled to on-package integrated polymer waveguide arrays with metallized 45° mirrors. The waveguides, which are terminated with multi-terminal (MT) fiber optic connectors, couple out/in high-speed optical signals to/from the chip. The CMOS transceiver chip fully integrates all analog optical circuits such as VCSEL drivers, transimpedance amplifiers and clock and data recovery (CDR) retiming circuit with a low jitter LC-PLL. Digital circuits for pseudorandom bit-pattern sequence generators (PRBS) and bit-error rate test (BERT) are fully integrated. 20Gb/s electrical and 18Gb/s optical eye diagrams for the transmitter were measured out of the package. A fully packaged transmitter and receiver including clock data recovery at 10Gb/s have also been measured.

The package integration of optical components with electronic integrated circuits (ICs) for optical interconnects is a subject of much debate and will, to a large extent, determine the performance of the optical interconnect system. In this paper we examine the challenges of incorporating optical interconnects into a computer system; specifically we cover several ways to integrate the optical components with a central processing unit (CPU) or chipset. Critical performance parameters such as the supported distance, power consumption and the achievable bandwidth are all impacted by the electrical integration between the IC and the optical components. Additional electrical link issues which also have a large impact on the performance of the link will be discussed as well; these include protocol related issues as well as signal integrity concerns, such as the jitter budget. We will also discuss the performance of some of the competing electrical technologies in order to provide a better understanding of the implementation challenge facing the developers of optical interconnect technology. Rack to rack communications are quickly moving to optical links, board to board communication is the next step and chip to chip communication is still further out as the electrical solutions for this topology have a great deal of headroom.

Optical links offer many advantages over copper based solutions for 10 Gb/s interconnects, including lighter weight, longer reach and lower power consumption. Copper solutions are either very bulky and of limited reach (10GBASE-CX4) or have high power dissipation (>10W for a 10GBASE-T link). Previous optical solutions for high-volume, short interconnects have been limited by cost and connector cleanliness considerations. In this paper, we describe a duplex active optical cable which overcomes these limitations. Active optical cables not only retain the advantages of optical links with the external characteristics of an electrical cable, but provide additional advantages in performance and yield by eliminating the extra link margins inherent in open optical link standards. A new electrical connector is described which provides excellent return loss performance, high density and a rugged, consumer friendly design. Performance results for 15m graded index plastic optical fiber and 100m multimode glass fiber based cables are reported. Low jitter contribution and power dissipation of ~1W per link are achieved. Finally the design and performance of adapters allowing the use of this cable in present SFP+ and XFP transceiver systems is presented.

With the ongoing progress in chip scaling, the data flow to and from chip packages is increasing accordingly. The simultaneous increase of channel count and channel speed in an essentially constant form factor becomes a more and more demanding challenge. The resulting I/O-bottleneck is considered to be a major limiting factor for the overall performance of future chip packages and computing systems. Optical interconnects offer both increased channel density as well as longer link reach at high frequencies. Our current work focuses on integrating optical I/O with standard organic packages in order to maximize the aggregate data flow to and from such packages. We present a novel approach for attaching an electro-optical conversion module directly on top of the organic chip package, together with experimental results of a first prototype implementation.

Three-dimensional optical wiring, consisting of stacked optical waveguide films with 45° mirrors, is a backbone for integrated optical interconnects and solar energy conversion systems. By using the self-organized lightwave network (SOLNET) technique, we observed leakage/scattering of guided light beams at 45° mirrors of core end facets in optical waveguide films. When 405-nm write beams were introduced into the optical waveguide having a photo-refractive material layer on the back, three excess lines of SOLNET, which may be caused by the guided beam tunneling into the cladding film and by the refraction at core end facet corners, were grown from the 45° mirror, in addition to a vertical waveguide of SOLNET formed by reflected beams. To reduce the leakage/scattering, we proposed the two-layer skirt-type cores with low-index (LI) part and high-index (HI) part. The LI part located between the HI part and the cladding film prevents the guided beams from tunneling into the film. The skirt-type core end facets put the corners away from the beam path. These effects were confirmed by simulations using the beam propagation method and the finite difference time domain method. Optical waveguide films with the proposed structure were fabricated by the built-in mask method.

In this paper, different hybridly integrated optical devices including optical multiplexer/ demultiplexer and optical transceivers are described. The devices were made using polymer planar light wave circuit (P2LC) technology. Laser diodes, photodiodes, and thin-film filters have been integrated. Key issues involved in this technology, in particular the coupling between laser diodes and polymer waveguides, and between waveguides and photodiodes and also fibers are discussed.

A stable and high-efficiency optical transmitter module was fabricated for optical printed circuit board (OPCB) based interconnections. A bottom-emitting VCSEL was directly bonded on a 90°-bent fiber connection block. Since this transmitter module does not have free space between the VCSEL and the connection block, it reduces the optical losses due to the scattering and beam divergence at the interface between the VCSEL and the connection block. A ray trace simulation for the optical loss supports the conclusion that closer contact of VCSEL to the connection block can provide higher coupling efficiency by eliminating the optical losses induced by the Fresnel reflection and the beam divergence. The index matching fluid treatment between the VCSEL and the connection block improves the coupling efficiency especially in the longitudinal direction. This trend was experimentally identified. Effective heat discharge through the contacted connector in this module improves significantly the power characteristics of the VCSEL. The L-I-V curves demonstrate that the fabricated VCSEL module shows higher optical powers than the bare VCSEL improving from +0.3 dB to +3.3 dB. Successful eye diagram at the speed of 5 Gb/s/ch with 850 nm was obtained. The bit error rate was 10^-9 at the speed of 5 Gb/s/ch, and it became lower than 10^-12 at the speed below 3 Gb/s/ch.

Heat dissipation, thermal stresses, and cost are key packaging design issues for virtually all semiconductors, including photonic applications such as diode lasers, light-emitting diodes (LEDs), solid state lighting, photovoltaics, displays, projectors, detectors, sensors and laser weapons. Heat dissipation and thermal stresses affect performance and reliability. Copper, aluminum and conventional polymeric printed circuit boards (PCBs) have high coefficients of thermal expansion, which can cause high thermal stresses. Most traditional low-coefficient-of-thermal-expansion (CTE) materials like tungsten/copper, which date from the mid 20^th century, have thermal conductivities that are no better than those of aluminum alloys, about 200 W/m-K. There are an increasing number of low-CTE materials with thermal conductivities ranging between that of copper (400 W/m-K) and 1700 W/m-K, and many other new low-CTE materials with lower thermal conductivities. An important benefit of low-CTE materials is that they allow use of hard solders. Some advanced materials are low cost. Others have the potential to be low cost in high-volume production. High-thermal-conductivity materials enable higher power levels, potentially reducing the number of required devices. Advanced thermal materials can constrain PCB CTE and greatly increase thermal conductivity. This paper reviews traditional packaging materials and advanced thermal management materials. The latter provide the packaging engineer with a greater range of options than in the past. Topics include properties, status, applications, cost, using advanced materials to fix manufacturing problems, and future directions, including composites reinforced with carbon nanotubes and other thermally conductive materials.

Polymer Optical Fiber (POF) optical modules are gaining momentum due to their applications in short distance communications. POFs offer more flexibility for plug and play applications and provide cost advantages. They also offer significant weight advantage in automotive and avionic networks. One of the most interesting field of application is home networking. Low cost optical components are required, since cost is a major concern in local and home networks. In this publication, a fast and easy to install, low cost solution for efficient light coupling in and out of Step Index- POF is explored. The efficient coupling of light from a large core POF to a small area detector is the major challenge faced. We simulated direct coupling, lens coupling and bend losses for step index POF using ZEMAX^R optical simulation software. Simulations show that a lensed fiber tip particularly at the receiver side improves the coupling efficiency. The design is optimized for 85% coupling efficiency and explored the low cost fabrication method to implement it in the system level. The two methods followed for lens fabrication is described here in detail. The fabricated fiber lenses are characterized using a beam analyzer. The fabrication process was reiterated to optimize the lens performance. It is observed that, the fabricated lenses converge the POF output spot size by one fourth, there by enabling a higher coupling efficiency. This low cost method proves to be highly efficient and effective optical coupling scheme in POF communications.