This paper presents a brief review and discussion on the opportunities and challenges facing the optical components and sub-systems vendors. Specifically, this paper discusses some of the current components and sub-system development on the low loss CWDM filters, wavelength blockers, PLC switch arrays, wavelength selective switches, optical protection switching sub-systems, tunable filters and DCMs, and in addition, the fiber-coupled short-wavelength diode-lasers for medical applications.

Optical communication systems have evolved from simple point-to-point transmission systems in the late 1970's to today's multi-channel DWDM systems integrated with optical switching. These advanced DWDM systems have very stringent optical performance, system reliability, and cost requirements. As a result, deployment of these systems has been limited to date. This situation has started to change recently and a lot of industry interest is now focused on deploying advanced optical systems in high performance telecommunication environments. Integrating optical functions in a single opto-electronic integrated circuit (OEIC) has the potential to accelerate this deployment by reducing manufactured costs, reducing physical card size, and increasing reliability. This paper will describe a specific instance of a DWDM transport and optical switching system, and its functional decomposition into individual cards. The requirements that are then imposed on the optical components placed on these cards are described. We will show the function of advanced switching and optical monitoring. Initial validation of a system card was made using off-the-shelf discrete optical components and then replaced with an OEIC implementation. Results of the integration experience will be presented.

Optical technology plays an increasingly important role in numerous information system applications, including optical communications, storage, signal processing, biology, medicine, and sensing. As optical technology develops, there is a growing need to develop scalable and reliable photonic integration technologies. These include the development of passive and active optical components that can be integrated into functional optical circuits and systems, including filters, electrically or optically controlled switching fabrics, optical sources, detectors, amplifiers, etc. We explore the unique capabilities and advantages of nanotechnology in developing next generation integrated photonic information systems. Our approach includes design, modeling and simulations of selected components and devices, their nanofabrication, followed by validation via characterization and testing of the fabricated devices. The latter exploits our recently constructed near field complex amplitude imaging tool. The understanding of near field interactions in nanophotonic devices and systems is a crucial step as these interactions provide a variety of functionalities useful for optical systems integration. Furthermore, near-field optical devices facilitate miniaturization, and simultaneously enhance multifunctionality, greatly increasing the functional complexity per unit volume of the photonic system. Since the optical properties of near-field materials are controlled by the geometry, there is flexibility in the choice of constituent materials, facilitating the implementation of a wide range of devices using compatible materials for ease of fabrication and integration.

The confluence of highly integrated computation chips, huge off-chip interconnectivity requirements, increasingly high channel speeds, and the large spatially extended systems being considered for future high end servers, together with the looming issues of thermal and power management offer an opportunity for optical interconnects to become the preferred solution for many interconnect domains. Optical interconnects are already the technology of choice for the longer length links required in computing systems (10's of meters). However, to achieve this status for link distances at the backplane and card level will require increasingly integrated optical interconnect solutions, which presents many challenges as well as opportunities. The primary inhibitor to adoption of optical interconnects in this ultra-short distance regime is poor cost competitiveness with electrical links. The cost reductions possible with evolutionary enhancement of today's parallel optical modules will not be enough. Potential technologies which could break this cost barrier include the use of waveguides on card to eliminate the optical "module," and chip integrated photonics plus electronics. This paper will discuss the issues and challenges for optics in this short distance regime and present some of the technical solutions that we are pursuing.

Due to ever-faster processor clock speeds, there is a rising need for increased bandwidth to transfer large amounts of data, noise-free, within computer and telecommunications systems. A related requirement is the demand for high bit-rate, short-haul links. Here, optical transmission paths are a viable alternative to high-frequency electrical interconnections, whereby layers with integrated waveguides are particularly suitable. The reasons for this include that a higher connection density can be achieved and the power dissipation, as well as interference from electromagnetic radiation, are significantly lower. The article presents general considerations and the results of research conducted by the German BMBF Project NeGIT, into the manufacture of circuit boards with embedded polymer optical waveguides. The electrical-optical boards were fabricated using precise photolithographic processes and standard lamination methods. They possess the thermal stability necessary for manufacturing processes and operational conditions, in terms of both bond strength and the stability of the optical properties. As part of this project, a design of an optical coupling in the daughter card and board backplane interfaces was developed and is presented as the centerpiece of this study.

We present a review of our work on the micro/nano-scale design, fabrication and integration of optical waveguide arrays and devices for what we call application-specific "optical printed circuit boards" (O-PCBs). Generic O-PCBs are composed of an optical layer carrying basic forms of optical wires and devices and an electrical layer carrying arrays of electrical wires and devices. Application-specific O-PCBs carry optical layers that are composed of varied forms of optical wires and devices tailored to perform specific functions. In this paper, we present two examples of application specific O-PCB: One is a module for inter-chip optical interconnection application and the other is an all optical wavelength splitting triplexer module that we investigated for subscriber telecommunication application. The inter-chip optical interconnection module is to replace copper wires between the central processing units (CPUs) and memory chips in the computer system. The triplexer module is composed of an array of cascaded directional couplers to split the wavelengths for fiber-to-the-home (FTTH) subscriber system application. All these O-PCBs consist of planar circuits and arrays of polymer waveguides and devices of various dimensions and characteristics to perform the functions of transporting, switching, routing and distributing optical signals on flat modular boards. We fabricate polymer waveguide by way of thermal or ultraviolet (UV) embossing (or imprinting) technique. Theoretical calculations provide design rules for the miniaturization of the waveguide devices and for the maximization of the integration densities of the waveguides and devices to be placed on the O-PCBs.

We report integrated devices in chalcogenide glass for all-optical signal processing, based on pure Kerr (near instantaneous) optical nonlinearities. We demonstrate an integrated 2R optical regenerator operating through a combination of nonlinear self-phase modulation followed by spectral filtering, with a potential to reach bit rates in excess of 1Tb/s. It consists of a low loss As2S3 chalcogenide rib waveguide incorporating a high quality Bragg grating written by an ultra-stable Sagnac interferometer. We achieve a nonlinear power transfer curve using 1.4ps pulses, sufficient for suppressing noise in an amplified link. In addition, we report photonic crystal structures fabricated by focused ion beam (FIB) milling in AMTIR-1 (Ge33As12Se55) chalcogenide glass. We realize high quality free-standing photonic crystal membranes, and observe optical "Fano" resonances in the transmission spectra at normal incidence. We achieve good agreement with theoretical results based on 3D finite difference time-domain calculations. Finally, we achieve resonant evanescent coupling to photonic crystal waveguides via tapered microstructured optical fibre (MOF) nanowires.

We present our design and fabrication methodology of planar photonic crystal wavelength switches and the optical micro-bench surrounding them. The core device is a channel add-drop multiplexer (CADM) whose pass/transfer element can be turned off and on in tens of nanoseconds. The photonic crystal consists of a regular triangular array of SiO₂ -filled holes in an amorphous Ge₃Si film. The film is sandwiched between two SiO₂ cladding layers. The pass and transfer buses consist of linear extended defects in the crystal, with the pass bus and each drop bus separated by a cavity resonator defect tuned to each wavelength. There is a small region where an ECD-designed chalcogenide alloy is incorporated into each resonator. Switching is accomplished by changing the structure of the chalcogenide between amorphous and crystalline, using a short wavelength diode laser. The optical bench consists of photonic wire waveguides formed in the Ge₃Si film and deep trenches in an underlying thick SOI film to accommodate bonded access fibers, both features being photolithographically co-aligned to the photonic crystal array. This, along with our impedance-matching interface designs, assures that there is low input-output power loss. The local reconfigurability in effect elevates the CADM to an all-optical router. Sub-100 nanosecond latency enables packet-level discernment. The large difference in optical constants of the two chalcogenide phases provides high on-off contrast (low crosstalk). The stability of the two phases gives complete latching nonvolatility. Our current progress in building and testing prototypes of our switches is also presented.

The effects of design parameters on the modulating voltage and optical bandwidth are reported for lithium niobate, GaAs and polymer electro-optic modulators by using rigorous numerical techniques. It is shown that by etching lithium niobate, the switching voltage can be reduced and the bandwidth improved. For a GaAs-based modulator using higher aluminium content in the buffer layer for a given optical loss can shorten the device length. It is also observed that the dielectric loss and impedance matching play a key role in velocity-matched high-speed modulators with low conductor loss. It is also indicated in the work that by using tantalium pentoxide coating, velocity matching can be achieved for GaAs modulators. The effect of non-vertical side wall on the polarisation conversion and single mode operation and the bending loss of polymer rib waveguide for electro-optical modulators are also reported.

Novel algorithms based upon Mueller matrix terms are presented herein, which allow the recovery of the spectra associated with incident transverse electrical (TE) and transverse magnetic (TM) orthogonal states of polarization. These, in turn, give more insight into polarization-dependent frequency shifts and other performance-related parameters of interest. This elegant patent-pending solution entails little computational efforts and can significantly improved the testing capacity and capabilities of component designers and contract manufacturers.

This paper reports numerically analyzed results on temperature dependent performances of planar-type long period waveguide gratings (LPWGs) for thermally tunable wavelength filter applications. The thermally tunable characteristics of the LPWG with a four-layer geometry have been evaluated. The calculated results show that the tuning characteristics depend significantly on the temperature dependent refractive index change rate of the core and clad waveguide materials compared to their thermal expansion coefficient.

We developed model and unveiled the mechanism of the large wavelength-dependent attenuation (WDA) that has been hindering the development of tilting-mirror MEMS VOA. We developed a new tilting-mirror VOA with low WDA of <0.1dB at 20dB attenuation.

From long haul, metro access and intersystem links the trend goes to applying optical interconnection technology at increasingly shorter distances. Intrasystem interconnects such as data busses between microprocessors and memory blocks are still based on copper interconnects today. This causes a bottleneck in computer systems since the achievable bandwidth of electrical interconnects is limited through the underlying physical properties. Approaches to solve this problem by embedding optical multimode polymer waveguides into the board (electro-optical circuit board technology, EOCB) have been reported earlier. The principle feasibility of optical interconnection technology in chip-to-chip applications has been validated in a number of projects. For reasons of cost considerations waveguides with large cross sections are used in order to relax alignment requirements and to allow automatic placement and assembly without any active alignment of components necessary. On the other hand the bandwidth of these highly multimodal waveguides is restricted due to mode dispersion. The advance of WDM technology towards intrasystem applications will provide sufficiently high bandwidth which is required for future high-performance computer systems: Assuming that, for example, 8 wavelength-channels with 12Gbps (SDR¹) each are given, then optical on-board interconnects with data rates a magnitude higher than the data rates of electrical interconnects for distances typically found at today's computer boards and backplanes can be realized. The data rate will be twice as much, if DDR² technology is considered towards the optical signals as well. In this paper we discuss an approach for a hybrid integrated optoelectronic WDM package which might enable the application of WDM technology to EOCB.

Optical interconnects have gradually replaced electrical interconnects in the long-distance telecom, local-area, and rackto- rack link classes. We believe that this transition will also happen in the card-backplane-card datacom link class, both for bandwidth*length reasons and for density reasons. In analogy to the transition from individually wired boards to integrated printed circuit boards, we believe that eventually board-level optical interconnects will be based on an integrated technology such as board-embedded waveguides. In order to bring optical waveguide technology into mainstream product development plans, however, numerous challenges on many levels have to be met. Problems to be tackled span from the base level of materials (stability, processability) and devices (reliability, lifetime), over the subsystem level of packages (concepts, cost-efficient assembly and alignment) all the way up to the system level (link architecture, system packaging, heat management). A sustainable solution can only be reached if the development of all individual technology components is done with the whole system in mind. Important figures of merit are the cost per gigabit per second, the power per gigabit per second, and the maturity/reliability of the technology. We will give an overview of our optical interconnect activity, with respect to these challenges. We will discuss the options, explain our technology decisions and present some results of our multi-disciplinary activity.

Electrical interconnection networks connecting the different processors and memory modules in modern large-scale multiprocessor machines are running into several physical limitations. In shared-memory machines, where the network is part of the memory hierarchy, high network latencies cause a significant performance bottleneck. Parallel optical interconnection technologies can alleviate this bottleneck by providing fast and high-bandwidth links. Moreover, new devices like tunable lasers and detectors or MEMS mirror arrays allow us to reconfigure the network at runtime in a data transparent way. This allows for extra connections between distant node pairs that communicate intensely, achieving a high virtual network connectivity by providing only a limited number of physical links at each moment in time. In this paper, we propose a reconfigurable network architecture that can be built using available low cost components and identify the limitations these components impose on network performance. We show, through detailed simulation of benchmark executions, that the proposed network can provide a significant speedup for shared-memory machines, even with the described limitations.

The CMOS IC industry thrives on the down-scaling drive for ever smaller transistors, leading to faster, smaller and more complex digital systems. These ICs are interconnected by electrical tracks running on Printed Circuit Boards. Due to different frequency-dependent sources of signal degradation, the performance of these electrical interconnects lags behind the IC performance. As the electrical interconnect bottleneck increasingly impacts overall system performance, the interest in optical interconnects at the inter-chip level is growing. An important question to answer is how and where such optical interconnects should be implemented. Therefore, we first discuss the weaknesses of electrical interconnects and the potential benefits of optical interconnects. From this we then consider the implications on the introduction of optical interconnects and we argue why integration is of key importance for the successful introduction of optical interconnects at this level. Finally we describe how we have implemented optical inter-chip interconnects in a demonstrator system and go into more detail on the different levels of integration in this demonstrator system.

High-density parallel optical interconnection is introduced as a solution to solve transmission bottlenecks in memory test system. A protocol-free parallel optical module capable of transmitting from DC to 34.1 Gbps (4.267 Gbps × 8 ch) has been developed. Data transmission throughput density per unit volume of 19 Gbps/cc and random jitter of less than 3ps rms are achieved. And also, we will describe the manufacturing process, the module testing, and self-diagnosis for optical transmission system. Furthermore, high-density optical connector and high-density optical fiber cable suited for mechanical requirements of Memory Test System have been developed.

An optical cell switch for interconnecting massively parallel nodes offers the potential for reduction in size, power consumption, and cost of high-performance computing (HPC) interconnects. We designed an architecture based on a broadcast and select approach that is highly flexible in terms of supported ports and can easily scale from a 16x16 to a 2048x2048 port switch by exploiting both wavelength multiplexing and fiber multiplexing. The optical system is designed for 40 Gb/s operation, but the full 160 Gb/s switching likely required of a commercial system can be supported by this architecture. At the core of the switch is an array of semiconductor optical amplifiers (SOAs), which provide fast switching (~1 ns), high extinction ratio (>40 dB) for cross-talk reduction, and optical gain (15 dB typical). The full optical switch consists of a 2-stage broadcast and select design for fiber select and color select, leading to a bufferless low-latency crossbar cell switch. A switch system demonstrator with 8 full optical paths has been implemented and used for performance characterization. A fast 40 Gb/s cell receiver was developed and proven to support up to 9 dB dynamic range. System demonstration measurements have shown that a raw BER of 10-15 is achievable. Optical cross-talk is negligible and does not degrade the system performance. The system design and verification experiments demonstrate that a scaleable 40 Gb/s switch for massively parallel systems is feasible and offers the potential for significant size, power consumption, and cost reduction by applying the scalability of an optical solution to a HPC system.

We evaluate VCSEL interconnects for next-generation High Productivity Computers in which hundreds of terabits of bandwidth are envisioned. We present results for VCSEL based links operating PAM-4 signaling using a commercial 0.13μm CMOS technology. We perform a complete link analysis of the Bit Error Rate, Q factor, random and deterministic jitter by measuring waterfall curves versus margins in time and amplitude. We demonstrate that VCSEL based PAM-4 can match or even improve performance over binary signaling under conditions of bandwidth limited 100meter multi-mode optical link at 5Gbps. We present the first sensitivity measurements for optical PAM-4 and compare it with binary signaling. An empirical relationship for VCSEL scaling versus bit rate and aperture is presented in order to explore reliability of VCSEL-based links. Reliability is found to degrade with aperture with a fourth order power law dependence.

High Power Optical Amplifiers (HPOAs) are key components in high-bandwidth, free-space communication systems. In many applications, these HPOAs must be highly-reliable, which leads to specific design choices. Erbium/Ytterbium co-doped cladding-pumped gain stages provide high power and efficiency. Some of the design choices and key results will be described. Amplifiers with output power exceeding 10 W and fundamental spatial-mode output will be described.

An active quench and reset circuit (AQRC) is an essential control circuit for ensuring high-speed photon counting with geiger-mode avalanche photodiodes (GMAPs). Its purpose is to turn off the detector when an avalanche has been detected, register a photon count and then reset the device to its quiescent bias voltage after a preset interval, to enable further avalanche events to be counted. This paper presents an AQRC-IC, developed using Europractice's ASIC Service. The purpose of the design was to develop a high-speed CMOS AQRC for hybrid integration with in-house GMAPs. The designed ASIC, developed using AMS' 3.3 V 0.35 μm CMOS process models, includes a ballast resistor for the external GMAP, a comparator sensing-stage, an active quench and an active reset stage. The hold-off time is determined using external silicon delay lines and an FPGA. The ASIC is implemented on a ceramic DIP as is the GMAP, and the AQRC prototype achieves a saturated count-rate of 5 Mcounts/s, an active quench of 45 ns, an active reset of 30 ns and possible increments of the hold-off time between 50 ns and 500 ns.

This paper describes the integration of an automatic gain and bias control circuit for avalanche photodiodes with the Sensl PCMPLusX photon counting module. The combination is a self contained module with integrated sensor, power supply, cooling and full microprocessor control system. The sensors can be configured remotely via a PC enabling the user to optimize the sensor performance for a particular application. The system has four channels which can be configured either in photon counting mode or gain control mode. With the photon counting module enabled the user can optimize detector characteristics such as quantum efficiency, dark count, amplification and operating temperature for specific applications. With the gain control module enabled the system allows the user to program the sensor to a desired multiplication gain factor and the circuit to automatically adjust for fluctuations in supply voltage.

The integration of photonics and electronics on a single silicon substrate requires technologies that can add optical functionalities without significantly sacrificing valuable wafer area. To this end, we have developed an innovative fabrication process, called SIMOX 3-D Sculpting, that enables monolithic optoelectronic integration in a manner that does not compromise the economics of CMOS manufacturing. In this technique, photonic devices are realized in subsurface silicon layers that are separated from the surface silicon layer by an intervening SiO₂ layer. The surface silicon layer may then be utilized for electronic circuitry. SIMOX 3-D sculpting involves (1) the implantation of oxygen ions into a patterned silicon substrate followed by (2) high temperature anneal to create buried waveguide-based photonic devices. This process has produced subterranean microresonators with unloaded quality factors of 8000 and extinction ratios >20dB. On the surface silicon layers, MOS transistor structures have been fabricated. The small cross-sectional area of the waveguides lends itself to the realization of nonlinear optical devices. We have previously demonstrated spectral broadening and continuum generation in silicon waveguides utilizing Kerr optical nonlinearity. This may be combined with microresonator filters for on-chip supercontiuum generation and spectral carving. The monolithic integration of CMOS circuits and optical modulators with such multi-wavelength sources represent an exciting avenue for silicon photonics.

Recent important advances in subwavelength nanostructures offer extraordinary control over the properties of light. We can now manipulate the propagation, storage, and generation of light, as well as practically prescribe its matter interaction properties based on first-principles. Photonic crystals, in particular, offer the unique ability to achieve ultrahigh Q/V_m nanocavities, and the arbitrary control of dispersion characteristics to increase photon-matter interaction times. In addition, silicon photonics offer the unique opportunity towards the convergence of electronics and photonics in a monolithic silicon platform for unprecedented information processing capacity. In this talk, we will review critical advances in these arenas, as well as present our developments in fundamental and applied studies of optics in subwavelength nanostructures.

Over a four-year period from 2001 to 2005, the Microphotonics Center Industry Consortium at MIT evaluated the vast array of new technologies that have disrupted the telecommunications industry. As part of its mission, the consortium researched a variety of communications-related technical and business topics, presented recommendations for the rational restructuring of the industry, and developed a 30-year communications technology roadmap (CTR). The CTR program was guided by industry-led Technology Working Groups (TWGs), with the support of MIT faculty and students. We present the findings of the Organics in Optoelectronics TWG in terms of advances in organic-material based optoelectronic integrated circuits (OEICs), and we propose a roadmap for optoelectronic integration enabled by hybrid organic-inorganic OEICs.

The proliferation of optical systems has manifested the need for materials that possess a unique combination of physical, chemical, and optical properties as well as being easily fabricated into low loss waveguide structures. This paper focuses on the optical properties and waveguide performance of perfluorocyclobutyl-based (PFCB) polymers and copolymers. Topics include their experimental and theoretical optical performance, new PFCB derivatives and hybrids, and novel highly light emissive nanocomposites using inorganic lanthanide nanoparticles.

A 4-bit polymer optoelectronic true time delay device is demonstrated. The device is composed of monolithically integrated, low loss, passive polymer waveguide delay lines and 2x2 polymer thermo-optic switches. Waveguide junction offsets and air trenches simultaneously reduce the bending loss and device area. Simulations are used to optimize the trench and offset structures for fabrication. The 16 time delays generated by the device are measured to range from 0 to 177 ps in 11.8 ps increments. The packaged device has an insertion loss of 14.5 dB and the delay switching speed is 2 ms. The delays generated by the device are suitable for steering a 1D or 2D sub-array of an X-band phased array antenna system.

Photonic crystals (PhCs) provide a promising nanophotonic platform for developing novel optoelectronic devices with significantly reduced device size and power consumption. Silicon nanophotonics is anticipated to play a pivotal role in the future nano-system integration owing to the maturity of sub-micron silicon complementary metal oxide semiconductor (CMOS) technology. An ultra-compact silicon modulator was experimentally demonstrated based on silicon photonic crystal waveguides. Modulation operation was achieved by carrier injection into an 80-micron-long silicon PhC waveguide of a Mach-Zehnder interferometer (MZI) structure. The driving current to obtain a phase shift of pi across the active region was as low as 0.15 mA, owing to slow light group velocity in PhC waveguides. The modulation depth was 92%. The electrode between the two waveguide arms of the MZI structure was routed to the space outside the MZI. In real devices, this planarized routing design would be essential to integrating the silicon modulator with electrical driving circuitry on a single silicon chip. For laboratory test, this routing scheme also eliminated the need of placing a bulky pad between the two arms and gave our modulator a distinctive slim profile and a much smaller footprint. Polymeric photonic crystals were designed for superprism based laser beam steering applications, and were fabricated by nano-imprint and other techniques.

Planar optics have become the leading technology for DWDM applications, due to its high performance and low manufacturing costs enabled by wafer scale processing. A powerful new design tool has been successfully applied to Planar Lightwave Circuit (PLC) design and fabrication, enabling rapid design information turns, mask and process error correction, and higher final device yields. We also present a new wideband AWG design that permits a low-ripple passband shape over a larger range of the DWDM spectrum. Combined with state-of-the-art semiconductor fabrication techniques, these new designs and methodologies have enabled a new generation of high-performance, high-yield PLC-based Reconfigurable Optical Add-Drop Modules (ROADM's). Optical data from a representative sample of almost 200 ROADM modules is presented, showing a tight statistical distribution of wide passband, low ripple, low insertion loss, and low polarization dependent loss devices.

In the quest for cost-effective bi-directional transceivers for the fibre-to-the-premise (FTTP) applications, this article describes the development of such devices manufactured on the Planar Lightwave Circuit (PLC) platform. The transceiver consists of the optical head, which receives, filters and detects the optical signals and the electronics, which processes these signals according to specific protocols. In this article, the realization of the optical head (known as a diplexer or triplexer) will be the main focus, with key results, such as the manufacture of the hybridization platform, the design and performance of the optical filters and the hybridization on the laser and photodiodes, presented. The challenges faced in the development will be described as well as the next steps to achieving the final product.

From its foundation Inplane Photonics focused on developing integrated solutions based on Planar Lightwave Circuit(PLC) technology. It is universally agreed that the path to lower cost-per-function in Photonics, as in Electronics, leads to integration. The timing of introduction of a new technological solution and the rate at which it will penetrate the market very much depends on the interplay between the size of the market, advantages the new technology offers, and the investment needed to achieve the level of performance that is envisioned. In telecom applications, where the main drivers for technology selection are cost and performance, such large-scale investment did not materialized yet for the PLC technology mostly due to a limited market size.

Monolithic photonic integration offers unsurpassed perspectives for higher functional density, new functions, high per-formance, and reduced cost for the telecommunication. Advanced local material growth techniques and the emerging photonic crystal (PhC) technology are enabling concepts towards high-density photonic integration, unprecedented per-formance, multi-functionality, and ultimately optical systems-on-a-chip. In this paper, we present our achievements in photonic integration applied to the fabrication of InP-based mode-locked laser diodes capable of generating optical pulses with sub-ps duration using the heterogeneous growth of a new uni-traveling carrier ultrafast absorber. The results are compared to simulations performed using a distributed model including intra-cavity reflections at the sections inter-faces and hybrid mode-locking. We also discuss our work on InP-based photonic crystals (PhCs) for dense photonic integration. A combination of two-dimensional modeling for functional optimization and three-dimensional simulation for real-world verification is used. The fabricated structures feature more than 3.5μm deep holes as well as excellent pattern-transfer accuracy using electron-beam lithography and advanced proximity-effects correction. Passive devices such as waveguides, 60° bends and power splitters are characterized by means of the end-fire technique. The devices are also investigated using scanning-near field optical microscopy. The PhC activity is extended to the investigation of TM bandgaps for all-optical switches relying on intersubband transitions at 1.55μm in AlAsSb/InGaAs quantum wells.

Magnetically doped Fe:InP and Fe:InGaAsP was characterized for verdict coefficient. The verdet coefficient was measured to be 180°/mm/T for Fe:InGaAsP, which is higher than YIG. High mesa waveguide of Fe doped InP/InGaAsP was fabricated and characterized. Faraday rotation in InP/InGaAsP waveguide was measured for the first time. The measured verdict coefficient is 33.3°/mm/T, which is only four times smaller than that of YIG.

We demonstrate 10Gbit/s operation of two different types of monolithic photocurrent driven wavelength converters (PD-WC). These photonic integrated circuits use a Semiconductor Optical Amplifier (SOA)-PIN photodetector receiver to drive an Electro-absorption (EA), or Mach-Zehnder (MZ) modulator that is integrated with a SGDBR tunable laser. We demonstrate improvements in optical bandwidth, insertion losses, device gain, and modulation efficiency.

Monolithically-integrated optical gain-competition inverters are demonstrated at 1.55 μm in the InGaAsP/InP material system. The optical inverters consist of etched-facet slave lasers that are side-injected with tapered etchedfacet master lasers. Single-input optical inverters show improved quenching contrast for devices with larger taper width with respect to the slave laser length. Inverter performance also shows a dependence on the ridge width and lasing modes of the slave laser. Two-input optical inverters are characterized which demonstrate NAND and NOR logic operation at different slave laser currents.

In this paper we first present a brief overview of our work on indium phoshide integrated optical circuits. Integrated circuits can be produced that contain active components such as optical amplifiers and passive component such as waveguides, arrayed waveguide gratings and phase modulators. With this set of components complete laser systems can be designed and realized on a chip. Then we will present in what way our integration technology can be used to generate and utilize ultrafast optical pulses. Issues concerning the realization, operation and future developments will be discussed.

We designed and fabricated an optical-electrical printed circuit board, which we call OE-PCB, by laminating a board of embedded polymer waveguide arrays between two electrical printed circuit boards. The polymer waveguide arrays are molded by embossing technique using a specially designed silicon mold, which can form the optical waveguide arrays and the 45 degree mirrors concurrently. The integrated silicon molds are fabricated by dry etching or wet etching. The layers of the waveguide arrays are sandwiched and laminated between the upper and the lower electrical PCBs to form the OE-PCBs.

Shallow junction silicon avalanche photodiodes developed for photon-counting applications exhibit a multiplication gain of several hundred when operated near breakdown. The small size and relatively large gain of these devices identifies them as potential candidates for short-haul optical networking at 650nm. Of importance is the frequency response of these devices and in particular the limitations on achievable bandwidth placed by the packaging of the diodes. This work investigates the effect package capacitance has on the frequency response of Geiger Mode Avalanche Photodiodes (GMAP) when compared to micro-stripline mounted devices. Impulse response measurements are made of the diode using a pulsed laser diode at a wavelength of 650 nm which provides pulses with full-width at half maximum (FWHM) of 70 ps typical and 200 ps maximum. A Fast Fourier Transform (FFT) is applied to the measured pulse to convert it to the frequency domain and de-embed the response of the test fixture and cable assembly. The electrical parameters of the packaged and micro-stripline mounted devices are compared in the frequency domain to see the effect of the package capacitance on the frequency response. Different device geometries are explored to identify suitable candidates for short-haul plastic optical fibre communications.

In this work, we use the photon polymerization process to prepare conducting polymer patterns and optical memory devices (CPROM). For the CPROM and image development, polyvinyl alcohol (PVA) is used as a solid support doped with the aniline monomer and transition metals, whereas for the patterns development, the ink, of a conventional DeskJet printer is substituted by a solution of transition metal ions that is used to print the desired pattern on substrates previously treated, in an aqueous solution of conducting polymer monomer. Both processes use photons and transition metals instead of conventional oxidants to promote polymerization of the aniline monomer inside the host medium, or on a flat surface, such as glossy paper. The SEM analysis of the CPROM shows that the metal particles grow in form of wire with diameter of 100 nm and lengths up to 4μm long. The conductivity of the printed conducting polymer patterns on glossy paper is about 2 × 10^-2 S/cm. These results strongly suggest that this new, fast and low cost technology can be used to produce conducting polymer structures for all polymer electronic devices applications.

This paper demonstrates the experimental results of combining new state-of-the-art Geiger mode avalanche photodiodes with an integrated hybrid active/passive quenching circuit. This creates an ultra-compact form factor for a low-light level detection module. Both devices, the photodiode and the quenching circuit, are fabricated using conventional CMOS process technology and wafer substrates. The photodiodes operate at low voltage levels (30 V to 40V). Detector active areas are of various dimensions (10μm to 50μm) and shapes (circular, cylindrical or square). The integrated active/passive quenching circuit is included on a 2.5 mm × 2.5 mm die, which has the functionalities of bias conditioning, passive/active quench, output signal generation and active recharge. The prototypes are hybrid packaged onto a PCB substrate. The module is characterised for detecting very low level optical signals such as the single photon activities. Parameters such as dark counts, timing jitter, and responsivity will be shown for the compact detection module. Our findings show that the proposed avalanche photodiode operation is considerably faster than the conventional discrete systems and the module size is greatly reduced.

Methacrylate based copolymers containing thermal and UV cross-linkable groups were prepared, ad their optical properties were investigated. Copolymerization of octafluoropentyl methacrylate (OFPMA) with hydroxyethyl methacrylate (HEMA) was followed by reacting HEMA and methacrylic anhydride (MAAN), yielding a fluorinated copolymer with cross-linkable pendant group. The refractive indices of the copolymers before cross-linking ranged from 1.4329 to 1.4646, and those of the cross-linked copolymers varied from 1.4500 to 1.4822, depending on the fluorine content.

We propose a new model of the rate equation for the time domain analysis. A modulated signal is analyzed by the rate equation using the finite difference method (FDM) in time domain. For the analysis of modulated optical signal, an injection current term in the rate equation is altered to an appropriated electrical term either for analog or digital signal. The bandwidth, transmission characteristics and nonlinearity of laser diodes are analyzed by the proposed rate equation model.

We propose the optical transceiver having reference clock generator and CDR with delayed data topology in this paper. The 125MHz reference clock of optical transmitter have been extracted from 10 × 250 Mb/s data arrays. The clock extraction of reference clock generator is achieved by summing the edge information of the each data. Moreover, our optical transmitter includes 2-stacks NMOS serializer scheme rather than 3-stacks conventional scheme to achieve high speed operation. In optical receiver design, we employ a novel CDR with delayed data topology to overcome the problems in conventional CDR such as instability in locking state, nonlinearity output proportional to phase difference, false locking at harmonic frequency. The optical transceiver is designed by using of 0.35μm CMOS technology.

For a simple, precise and low-cost planar lightwave circuit (PLC) device, we describe a novel method using polymer mold. Channel waveguide, made of polymer for transmitting a signal, is fabricated by using the replication method. Among replication techniques, NIL is preferred because of its simplicity and short process time and ease of precise manufacturing. NIL technique requires the precise mold as an embossing tool. By this time, the popular molds for embossing are silicon, nickel, and quartz, but these are not desirable due to their high cost, complex fabrication process, short life-time by brittleness and so on. In this study, we are trying to replace by polymer mold for mass production. We choose PDMS liquid and epoxy resin as a mold material for UV embossing and hot embossing, respectively. The used materials show superior quality from the viewpoint of mechanical strength, dimensional stability, and optical transparency. In advance, we make PDMS mold for UV embossing. With the developed distortion-free and void- free epoxy mold, we perform heat-treatment by sub-Tg annealing to improve the mechanical properties of mold. And we fabricate epoxy mold for hot embossing using the fabricated PDMS frame. The fabrication of an optical core is reported using NIL technique with fabricated polymer molds. This fabricated pattern for optical device is about 7 μm at depth, 6 μm at width. These values have the small difference below 1 μm compared to the original stamp and the surface roughness of core is about 14 nm root mean square. This is satisfactory value for a low-loss optical waveguide and it also represent that the fabricated polymer mold shows the possibility of mold for embossing.

We designed a compact wavelength-splitter using self-collimated diffraction in two-dimensional polymeric photonic crystal (PhC). In a three-dimensional finite difference time-domain (3-D FDTD) simulation, the beams of two different wavelengths (1043-nm and 1550-nm) are separated at an angle of 15 degrees in the PhC region. And, we fabricated this device using ultra-violet (UV) embossing technique that can be simply performed at room temperature with a silicon mold. We expect that this design concept and low-cost mass production method of a PhC-based device enable us to realize a very high-density integrated circuits due to its simple fabrication process and compact size.

We propose a novel directional coupler type switch based on mode transfer by thermo-optic effect. In our design, the directional coupler switch maintains the anti-coupling by changing the refractive index in ON state and the coupling in OFF state. In this paper, the directional coupler switch consisted of only one single electrode on the opposite side of input waveguide in the coupling region. The coupling region was designed to have the coupling length for perfect optical coupling. Polymer materials with large thermo-optic coefficient were adopted for the change of the refractive index profiles of two waveguides. As the thermo-optic coefficient of polymer materials is negative, the refractive index decreases by applied voltage. When the electrode is sufficiently powered, the incident light only propagates along the input waveguide due to breaking the symmetry. For the optimized switch design, our simulating study shows the extinction ratios of -21.2 and -28.3 dB in OFF and ON states, respectively. The required variation of the refractive index for switching is only order of 10^-3. This concept is expected to improve the power consumption and the extinction ratio of a directional coupler switch.

We present the design of a newly conceived triplexing optical microsystem that can provide bases for three wavelengths splitting function for gigabit passive optical network application. Three wavelengths consist of one for the upstream, 1310nm wavelength signal and the other two for downstream, 1490nm and 1550nm wavelength signal. The triplexer module is designed in the form of a planar optical integrated circuit using three directional couplers. In order to increase wavelength splitting performance we arrange the directional coupler by cascaded connecting method and use the asymmetric Y-branch. We analyzed its performance characteristics by BPM. The optical crosstalk of the 1310nm signal to the 1490nm signal and the 1550nm signal are -27.92dB and -66.83dB, respectively in the upstream. In the case of downstream the optical loss is less than 0.5dB with 20nm bandwidth and the optical crosstalk reaching less than -30dB in the downstream is 19nm.

This paper reports, for the first time, a new method of fabricating a 45°-micro-reflector-ended polymer waveguide using one-step UV embossing technique. This technique allowed us to fabricate an array twelve channel multimode polymer waveguides equipped with a 45°-micro-reflector by using a one-step UV embossing technique. For the embossing we used a 45°-ended silicon waveguide mold. The silicon waveguides mold has a 45° slope prefabricated at the end of each waveguide structure. First, a 1um-thick-SiO₂ layer is grown on the (100) silicon substrate. Then, the waveguide channel is patterned. The patterned waveguide channel is tilted at 45° from (100) silicon alignment base line to use the wet etching morphology which has 90° and 45° etched slopes when exposed to KOH and isopropanol saturated KOH solutions. After that, silicon substrate is wet etched with KOH solution to form the rectangular waveguide patterns. Another thin SiO₂ layer is deposited again to protect the waveguide patterns and substrate. A thin line is then patterned on the top of the waveguide structure and a thin-line shaped silicon surface of the top of the waveguide structure is opened. Then, the opened silicon surface is wet etched in KOH saturated with isopropanol solution. The other area is protected by SiO₂ layer. The etched shape has a V-shape and the angle from the bottom side is 45°. After SiO₂ removal and cleaning, 45°-ended silicon waveguide mold is completed. With this mold, UV embossing is performed to form undercladding structure and 45° slope simultaneously. And a metal film is coated on the surface of the 45° slope. And then, core polymer is filled and cured by UV irradiation. This method can be applicable to waveguide structures of sizes ranging from multimode to single mode.