We have developed a novel class of projection lithography systems that provide both high-throughput resist patterning and dielectric via formation for production of a variety of electronic modules, including optoelectronic waveguides, flat-panel displays, multichip modules, printed circuit boards, and microelectromechanical systems. The new technology eliminates limitations of current lithography tools, including contact and proximity tools, conventional projection systems, steppers and scanners, and direct-write machines. Further, the new system concept is highly modular, thereby providing equipment upgradability as well as choice of user-specified system configurations. These results are achieved with a novel, hexagonal seamless scanning concept and a single-planar stage system configuration that provide both high optical and scanning efficiencies, and combine high-resolution imaging with very large exposure area capability. We describe the new technology and present experimental results. These lithography systems are highly attractive for cost-effective production of microelectronic devices with feature sizes ranging from 15 micrometers to below 1 micrometers and substrate sizes ranging from 150 X 150 mm to larger than 610 X 660 mm.

We demonstrate the integration of vertical-cavity surface- emitting laser (VCSEL) arrays with Si-dummy chips for potential use in short-distance parallel optical interconnects. An 8 X 8 flip-chip bonded InGaAs VCSEL array was successfully modulated at data rates up to 0.8 Gbit/s/channel, corresponding to an aggregate data transmission capacity in excess of 50 Gbit/s. A 2 X 4 VCSEL array was indirectly flit-chip bonded to a Si substrate via a transparent glass carrier and package- limited data rates of 0.4 Gbit/s/channel were achieved. The large signal modulation bandwidth of these devices exceeded 2 Gbit/s. The electrical driving characteristics of the devices were found to be compatible with 3.3 V CMOS technology.

This paper describes the design, electrical nd optical test results for a 500Mb/s, 32-channel VCSEL driver ICs with built-in self-test and clock generation circuitry. The circuit design and silicon parts are available to the research community through the Consortium for Optical and Optoelectronic Technologies in Computing and the Optoelectronics Industry Association. This device is specifically targeted at users building VCSEL-based smart photonic system demonstrators.

Planar lightwave circuit (PLC) hybrid integration is a promising way to realizing low-cost and highly functional optical components which are integrated with opto-electronic (OE) devices. As low-cost components, WDM hybrid transceiver modules have been developed to construct the fiber-to-the- home networks. As highly functional optical components, a multi-wavelength light source, a high-speed optical wavelength selector and a differential photoreceiver module have been demonstrated to construct optical transmission and switching systems employing dense wavelength-division- multiplexing and time-division-multiplexing technologies. This paper reviews the current status and recent progress on the PLC hybrid integration.

Cross-connect switch is a popular switching architecture for telecom and datacom applications. Using various switching components and a k-shuffle interconnect, a cross-connect switch can be configured for general-purpose, blocking as well as non-blocking networking applications. We show that a 1D k-shuffle interconnect pattern is topologically equivalent to a 2D transposition transform pattern. Based on this observation and using space-invariant optical components, the transposition transform interconnect is experimentally implemented. To achieve a sensible packing, we propose to incorporate fiber arrays into the implementation so that the interconnect offers connectorized plug-and-play capability with its switching arrays. Experimental results of implementing a 256 X 256 connectorized free-space and fiber hybrid transposition transform interconnect for cross-connect switching are presented. Key parameters, such as insertion loss, cross- talk, and bit-error-rate of the hybrid interconnect module are measured. Video data are used to demonstrate interconnect quality of various link channels. Scalability to larger interconnects are speculated.

A complete set of methods for the calculation of electrical crosstalk in Optoelectronic Integrated Circuits is presented. From the examination of typical chip architecture, it is shown that the inductive coupling due to thin bondwires is critical. The model can be easily applied to several OEICs. Design guidelines are presented.

The investigations on GaAs/AlGaAs multiple quantum well self electro-optic effect device (SEED) arrays for optoelectronic smart pixels are reported. The hybrid integration of GaAs/AlGaAs multiple quantum well devices flip-chip bonding directly over 1 micrometers silicon CMOS circuits are demonstrated. The GaAs/AlGaAs multiple quantum well devices are designed for 850 nm operation. The measurement result under applied biases show the good optoelectronic characteristics of elements in SEED arrays. The 4 X 4 optoelectronic crossbar structure consisting of hybrid CMOS- SEED smart pixels have been designed, which could be potentially used in optical interconnects for multiple processors.

We propose to implement a modularly structured planar wave- guiding star-coupler for large-core polymer fiber-based optical interconnect applications. An 8 X 8 version of the coupler is demonstrated using polymer materials. The planar star-coupler can be mass-produced using injection molding technology at substantially low cost. Measurements indicate that by properly working out a trade-off between device compactness, uniformity and coupling efficiency, a < 2.0 dB power fluctuation among all receiving channels and a 3.1 dB excess power loss are obtainable.

Optoelectronic (OE) switching is a promising approach for routing signals in fiber optic networks. Recently, the integration of a 4 X 4 MSM array with optical surface waveguides has been reported. This technique greatly simplifies the packaging of an OE switch. The on-chip polyimide optical waveguides perform the optical signal distribution to a matrix of MSMs which are responsible for the switching operation itself. Photoresponse bandwidths exceeding 4 GHz have been demonstrated. Another important characteristic of a switch is the switching speed since it determines the reconfiguration time. Mechanical and thermal optical waveguide switches offer switching speeds of the order of milliseconds which is sufficient for network traffic management but too slow for packet switching. We report measurements on the switching characteristics of a 4 X 4 optoelectronic switch performed in both the frequency and time domain. In the time domain, the individual crosspoints exhibit a rise time of 3 ns. However, a sizeable overshoot and ringing settles only after 35 ns. This constitutes the reconfiguration time at present. This is confirmed by measurements in the frequency domain of the electrical transmission from control line to output line. The 3-dB switching bandwidth is a few hundred megahertz. The 35 ns reconfiguration time indicates that it is already suitable for packet switching in a 10 Mb/s network. Switching speed measurements on individual MSMs suggests that modifications to the switch circuit could improve the switching time. The switch could also find application as a component in the wavelength conversion circuit of a WDM fiber optic network.

In this paper, we report our success in depositing sol-gel derived silica films on InP using multiple spin coating and rapid thermal processing. The effect of rapid thermal process temperature and time duration on the property of the film is studied. The dependence of the single layer thickness as well as its refractive index upon the film preparation parameters have been obtained and are compared with that on silicon substrates. As a result of the study, a crack-free SiO₂ film with a thickness of 0.5 micrometers has been successfully deposited on InP at a processing temperature of 450 degrees C. We believe that our experimental result has indicated that it is possible to fabricate hybridized integrated optics devices on compound semiconductors through the sol-gel route.

A scheme for a five volt V(pi) ) nonlinear optical (NLO) polymer optoelectronic (OE) device is presented with the potential to realize an interaction length that is about an order of magnitude shorter than conventional five volt V(pi) ) NLO polymer OE devices. It utilizes available NLO polymer materials for the core layer and a conductive polymer material for the cladding layers. Since the cladding layer material is more conductive than the core material, most of the applied poling and modulation voltages is dropped across the core layer, rendering a more efficient device. Using an NLO polymer material with electrooptic (EO) coefficients of say 22 pm/V, it is feasible to demonstrate < 2 mm OE devices operating at TTL voltage levels. These small device sizes could lead to use within electronic multichip modules. In addition, since the majority of the poling voltage is dropped across the core layer, less voltage is required so that in-situ poling becomes possible.

A new hybrid design tunable semiconductor laser, with a wide tuning range, a narrow linewidth, simple tuning/control algorithms, low variations in output power across its tuning range and simple fabrication, is introduced. This hybrid laser consists of a large spot reflective amplifier (LS-RA) coupled to a Lithium Niobate Acousto-Optic Filter (AOF), giving wavelength selective feedback. The LS-RA waveguide is angled by 10 degrees to the coupling facet, but is normal to the other facet, giving reflectivities of 5 X 10^-5 and 3 X 10^-1 respectively. This amplifier structure allows maximum coupling to the AOF without stringent alignment tolerance. THe AOF consists of a 2-stage acoustic TE/TM converter with a high TE reflectivity coating at the end. A propagating surface acoustic wave is employed to phase-match the TE and TM modes of a specific wavelength, achieving a narrow-band feedback into the LS-RA. Output power and wavelength of the hybrid laser are controlled by the LS-RA current and RF drive frequency of the AOF respectively. Simulations using a Time-Domain Model and initial experiments have shown that the hybrid laser have a wide tuning range, narrow linewidth, SMSR >= 30 dB and low power variations across its tuning range.

Waveguide npin heterojunction phototransistors (HPTs) are investigated for analog fiber-optic link applications. The device is fabricated on a semi-insulating InP substrate with an integrated CPW transmission line. At low optical power, an incremental DC responsivity of approximately 16 A/W is observed at 1.3 micrometers wavelength. It is demonstrated that the HPT responsivity at RF frequencies can be increased through a second optical beam. Signal mixing experiment using two RF-modulated optical beams shows that the waveguide npin HPT can be used as an effective integrated photodetector/mixer for RF signal up- and down-conversion.

We have performed quantum-mechanical analyses of strain- symmetrized Ge/Si QWIPs grown upon a realized buffer layer of Si_0.4Ge_0.6 on Si. The multi-quantum-well (MQW) QWIP has 50 angstrom-thick compressively strained p-doped Ge quantum wells and 200 angstrom-thick tensile-strained Si- rich SiGe barriers. This MQW allows shorter-wavelength IR sensing than prior-art unbuffered Si_0.64Ge_0.36/Si asymmetrically strained QWIPs because the valence band offsets are approximately 3x larger. We predict normal- incidence higher-temperature operation over the 1.7-to-3.8- micrometers wavelength band using the bound-to-bound and bound-to- continuum transitions HH1-SO1 and HH1-SO-C respectively. We expect that the p-i-p Ge/Si MQW pixels analyzed here can be fashioned into 2D imaging arrays, and that the arrays can be integrated monolithically with Si readout circuity. We also anticipate that multi-spectral IR imaging will be feasible by the technique of vertical epitaxial stacking of 'sub- QWIPs' within each pixel - where each sub-QWIP has a narrowband spectral response that differs from its neighbor's, and each sub-QWIP's electrical readout current is independent of its neighbor's.

Switching and amplifying characteristics of a newly developed monolithic InGaAs active pixel imager array are presented. The sensor array is fabricated from InGaAs material epitaxially deposited on an InP substrate. It consists of an InGaAs photodiode connected to InP depletion- mode junction field effect transistors for low leakage, low power, and fast control of circuit signal amplifying, buffering, selection, and reset. This monolithically integrated active pixel sensor configuration eliminates the need for hybridization with silicon multiplexer. In addition, the configuration allows the sensor to be front illuminated, making it sensitive to visible as well as near IR signa radiation. Adapting the existing 1.55 micrometers fiber optical communication technology, this integration will be an ideal system of optoelectronic integration for dual band applications near room temperature, for use in atmospheric gas sensing in space, and for target identification on earth. In this paper, two different types of small 4 X 1 test array will be described. The effectiveness of switching and amplifying circuits will be discussed in terms of circuit effectiveness in preparation for the second phase demonstration of integrated, 2D monolithic InGaAs active pixel sensor arrays for applications in transportable shipboard surveillance, night vision, and emission spectroscopy.

As the photonic integrated circuits (PICs) are increasingly utilized for high-performance computer systems and communication networks, there exists a need to synthesize PICs automatically and rapidly. In this paper, we describe a methodology for modeling, simulation, and synthesis of optical waveguide networks for a rapid PIC prototyping. A good agreement between simulation result and actual prototype measurement has been observed for various PIC components like Y-branch, X-crossing, and directional coupler. The architecture and design methodology of optoelectronic system simulator (OS) is presented by utilizing the optoelectronic H-tree clock distribution network example.

The performance requirements of computer, telecommunication, and data-communication systems have increased considerably in recent years to a point where large-scale electronic systems nov suffer from an interconnection bottleneck Large computational systems, with tens, hundreds, or more nodes: are composed of many chip-to-chip and/or module-tomodule interconnections. These complex interconnection systems must be efficient and fast for good overall system performance. Free-space optical interconnects (FSOI) when combined with electronics offer a potential solution to relieve this communication bottleneck 4.5,6,7.8,9,10,11 Indeed, FSOI offer advantages in terms of large interconnection density, high distance-bandwidth product, low power dissipation, and superior crosstalk performance, especially at high data rates. 2,13.14,15,16 However, packaging of FSOI has become one of the major issues, in which alignment is the key factor determining the feasibility and performance of the whole system 17,18.19.20 Critical advances are required to assemble optoelectronic and optical components in a rugged yet simple system fully compatible with conventional electronic packages. In the following sections, we present how a conventional PCB board is populated with optoelectronic detector and laser chips and mated to an FSOI layer that is assembled separately. This is achieved using only commercially available devices and services and enabled b means of simple passive alignment techniques. Design considerations, system simulations, as well as experimental results are presented.

Novel concepts have been developed for miniaturized fiber optic switches. They are based on transmittive microoptical components. Here, beam deflection is achieved by moving microprisms or microlenses with the use of miniaturized actuators, mainly piezoelectric actuators. The deflected beam is directed to a microlens array where each of the lenslets couples the beam into one of the output fibers. The latter are also used as a regular array. Such miniaturized switches can be realized with quite good optical parameters, and also short switching time in the order of 1 ms. For prototype fabrication and future production of such switches integration methods of the microoptical components and the actuators play an important role. In the case that all components are adjusted and fixed separately a rather complex procedure and equipment is required and a special optomechanical design must be used to ensure sufficient system stability. In order to decrease considerably the effort for system integration we tested several approaches for building at first certain subassemblies. This was especially successful for the lens array/fiber array integration as the most critical in the switch configuration. By using a lens array substrate thickness slightly smaller than the lenslet focal length we were able to fix the fiber array by gluing directly to the substrate surface. We also started to integrate other optical functions, such as deflection and collimation into one quasimonolithic component by replication techniques. Here, both microprism and microlens structures have been replicated onto SELFOC microlenses. 5

A packaging technology has been developed to integrate a lenslet array with surface micromachined segmented deformable micromirrors. 12 X 12 electrostatic micromirror arrays were fabricated through a commercial surface micromachining process and integrated with glass microlenses positioned directly over the micromirror. Control of the spacing and the lateral alignment between the lenslet array and the micromirrors was important for effective fill factor. The spacing control was accomplished using glass spacer, and the lateral alignments were achieved by the use of an interferometric microscope. Measured results of the micromirrors' optical performance demonstrated the success of the packaging technology.

This paper describes the main characteristics of a miniaturized multipurpose IR spectrometer. The miniaturized spectrometer comprise of three silicon micromachined devices: an electrically modulated thermal IR emitter, and electrically tunable Fabry-Perot interferometer and a photodetector. The IR emitter and the detector are monolithically integrated into a silicon substrate. In addition, the silicon substrate carries an integrated circuit die-bonded and wire-bonded on the silicon substrate. The whole spectrometer assembly is packaged in a DIL package having holes for the incoming and outgoing radiation. The dimensions of the package are 12 mm X 23 mm X 5 mm. This concept enables the realization of a miniaturized spectrometer for high-volume and low-cost products. In the miniaturization, the critical optical characteristic is the throughput of a system. In addition, the S/N-ratio and crosstalk of the module are the main electrical characteristics to be considered in the miniaturization. In this paper, the performance of the spectrometer module is presented via measurements including the radiometric analysis, S/N-ratio analysis and crosstalk analysis.

Novel thin film photodiode is proposed. The active layer is thinner than the wavelength of the incident light. A part of the incident light beam is detected and the rest passes through the thin film photodiode without the absorption. Being inserted in the optical field, this sensor can detect the intensity profile formed along the propagating direction of the laser beam. This function is applied to construct the new interferometer detecting the intensity profile of the standing wave produced by the incoming and the reflected laser beams.

ASOC device technology was developed by Bookham for volume manufacturing of integrated optical components. It is based on single-mode rib waveguides formed on silicon-on-insulator wafers and uses many of the same processing techniques used in the manufacture of conventional silicon chips. ASOC is a hybrid technology, using discrete InP-based lasers and photodiodes mounted on the silicon as sources and detectors. Bookham's products are based on a set of integrated optics elements that can be put together to form a number of practical integrated optics devices. The first products to be produced in volume are optical transceivers and transmitters primarily for telecommunication access networks. A narrow-linewidth laser for WDM network applications is also being produced, and the company is involved in the development of silicon waveguide technology for sensor applications such as environmental monitoring.

A novel technique, the so-called skew ray imaging concept, has been developed for beam transformation of high power diode laser bars. It leads to beam circularization with optimum brightness conservation. This concept uses two key microoptical components: a fast axis collimator microlens (FAC) of high isoplanatism and a special array of beam deflecting elements, the number of which corresponds to the single emitter number of the diode laser. Using this concept of skew ray imaging in a modified form, prototypes of pumping sources for visible fiber laser have been developed and built up. Several watts of optical power have been focused into a small spot of 25 micrometers with a numerical aperture of 0.35. GRIN cylindrical microlenses with 0.1 mm focal length and diffractive blazed gratings as redirector have been used. The grating periods of the redirector sections have been between 8 and 100 (mu) M. They have been produced by e-beam direct writing in resist. After optimization of the fabrication process the diffraction efficiencies of al sections have been beyond 86 percent with good reproducibility. Special techniques have been sued for system integration. The FAC microlenses have been attached to a copper lens holder with a subsequent gluing process of the holder to the laser diode heatsink. A UV-curable adhesive with extremely low shrinkage has been selected. The redirector element has been integrated with an additional possibility for lateral adjustment in order to compensate minor residual walk-off effects of the microlens when the laser power is varied from zero to maximum. A very compact pumping source of 3 inches X 1 inch X 1 inch dimensions has been realized with 5 W optical power in the desired spot. First diode pumped fiber laser operation in the visible has been demonstrated with this source.

Hybrid integration of optoelectronic devices, such as GaAs MQW modulators, to CMOS VLSI circuits provides the opportunity to design ICs that integrate millions of transistors and thousands of high-speed optical I/Os for high-performance computing and switching applications. One of the challenges in designing such large-scale ICs lies in the development of an efficient method for integrating existing VLSI circuit layouts with 2D arrays of optoelectronic devices. This paper presents several such methods and describes their application.

There are many different types of components used in optical communication systems. Difficulties in interconnecting these elements are responsible for the increased cost and complexity of many systems. One of the main issues is the coupling efficiency between the different components involved. The coupling efficiency is affected by mode mismatches as well as device misalignments. In this paper, we look at the example of a hybrid optical switch to show some of the coupling issues when using otpical interconnects. We first show how the use of tapered polymer waveguides can perform a mode transformation in order to reduce the mode mismatch. We also present results for a Monte-Carlo simulation which shows the effects of the component misalignments in the hybrid device.

System alignment is often the cost driver in the production of optical system. In order to both miniaturize and reduce production costs, wafer scale integration of active and passive components is required. This integration relies on a host of techniques to align and bond active and passive devices into a monolithic structure. Moreover, this initial packaging is accomplished while the optics and supporting structures are in wafer form, thereby providing parallel fabrication with resultant cost savings. This paper describes the fundamental techniques for producing IMOS from wafer scale substrates. The relative merits of each approach are discussed, along with design concerns for successful application. Two example systems are discussed, each using a different fabrication technique.

This paper analyzes the manufacturing cost of photonic system using software that combines several methods for accurate cost accounting. Activity based costing assigns al capital equipment, material and labor costs directly to the product rather than to overheads. Cost of ownership models determine the cost of using machines under different financial and utilization scenarios. Libraries of standard machines, process steps, and process sequences facilitate rapid model building and modification. Using libraries for semiconductor and photonics fabrication, along with packaging and optomechanical assembly, we construct cost models for 2D VCSEL array communication modules. The result of the analysis is that the model cost is driven mainly by the epitaxial material cost, and laser yield limits VCSEL arrays to small scale integration.

Silicon v-groove structures have been utilized for passive positioning of optical fiber for fiber optic and opto- electronic applications. In this paper, we will present our results of using micro-machined silicon v-groove arrays to passively align optical fiber arrays to micro rod optics. We will also demonstrate the integration of N fiber arrays bonded into the silicon v-groove with a 1xN micro lens array, which is composed of a 2 inch-phase level diffractive optics. For the assembly of 1x6 fiber array and lens array with 16 phase level diffractive optics, the experimental results indicated that total insertion loss per link is typically 1.5-2.0 dB/channel.

A replication technique allowing for the wafer scale integration of microoptical elements is presented and illustrated by various examples. The technique is based on polymer UV reaction moulding using a modified contact mask aligned where mask and wafer are replaced by the replication tool and an arbitrary substrate, respectively. The technology takes advantage of the high precision and adjustment accuracy of photolithography equipment. The replication masters are nickel shims, etched Silicon wafers or uv-transparent fused silica tools. The latter ones allow for replication on opaque substrates. Additionally, polymer elements with unique properties can be obtained by the combination of replication and resist technology using partially transparent replication tools. Wafer scale hybrid integration of microoptical subsystems is accomplished by replication of polymer elements like lenses, lens arrays, micro prisms etc. onto semiconductor wafers containing detectors or VCSELs, or by combining microoptical elements on both sides of a glass wafer. The use of thin layers of uv cured polymers on inorganic substrates results in good thermal and mechanical stability compare to all-polymer devices.