We report in this paper the principal function of the electrically controlled variable optical attenuator (VOA) using polymer dispersed liquid crystal (PDLC) and describe the fabrication procedure on silicon v-groove. We have fabricated three VOA with a pitch of 2 mm on a single silicion v-groove chip with total dimensions of 12 mm x 10 mm. We have achieved a cell-dependent contrast ratio from 8 dB to 14 dB by applying a control voltage U_RMS (squared wave voltage, f = 10 kHz) from 0 to 30 V. We measured also a cell-dependent polarization dependent loss (PDL): < 3.6 dB for two cells and < 1.6 dB for one cell depending on the control voltage. The strong variation of the PDL and contrast ratio is due to the non-optimized PDLC processing parameters. Due to the large pitch size there is no crosstalk. The estimated power consumption is very low (< 1 μW), so the described fabrication procedure meets the requirements low cost, small power consumption and compact size. We have used this three VOA and proper chosen delay lines to build up a liquid crystal phase shifter (LCPS) for optically generated RF-signals at f_RF = 2 GHz. Using the vector sum of two signals a continuously 360° phase shift of the RF-signal is demonstrated. We will present the theory and measurement results of 360° phase shifting. This LCPS can be used to control individually the phase and amplitude of each antenna element.

In order to reduce size and cost, and at the same time increase overall performance, we designed a compact 8-ch CWDM MUX/DeMUX scheme based on free space optics. The device offers the following competitive performance specifications: IL < 0.8dB, IL ripple < 0.2dB, PDL < 0.1dB, PMD < 0.15ps, CD < 3ps/nm, IL uniformity < 0.3dB, adjacent channel isolation > 40dB, return loss > 50dB and pass-band bandwidth > 14nm. Such a device can operate in the temperature range of -10C° to 70C° with a TDL ~0.002dB/C°. In this paper, we will discuss the following three critical aspects of its design and implementation: (I) Design considerations and tolerance simulation. Here we discuss optimization of a set of critical design parameters: angle of incidence (AOI), beam size (BS), working distance (WD), filter aperture, filter orientation and filter-to-filter distance. (II) Build-in tolerance and critical alignment control. We have done extensive simulations to identify the critical variables and tolerance range for each variable. Based on this analysis, we then built in the alignment guidance and tolerances control into mechanical design. (III) Process control, material selection and surface preparation: Here we discuss the proper usage of the adhesives including the types of dual-effect adhesives, use of silica filler and coupling agent, surface preparation to achieve proper surface energy, tension and porosity, the optimum combination of the substrate and adhesive material for best shear and peel strength, and balancing temperature compensation and stress absorption.

We report performance characteristics for High Dynamic Range Integrated (HDRI) 10 Gb/s receiver. The receiver is based on hybrid integration of a MEMS actuator and 10 Gb/s photodetector in a differential output coplanar package. A free space micro-optics approach provides a compact coupling scheme with minimal insertion loss and packaging complexity. The presented integration concept is compatible with both P-I-N and avalanche photodiodes (APD). When packaged with an APD, the HDRI 10 Gb/s receiver demonstrates a dynamic range in excess of 40 dB with typical back-to-back sensitivity of -25 dBm with a 2³¹-1 PRBS 10 Gb/s data stream using NRZ format. The HDRI receiver provides a cost-effective alternative to a discretely packaged variable optical attenuator (VOA) and 10 Gb/s receiver combination, resulting in substantial reduction in size, fiber management, and total insertion loss. The HDRI receiver may be used in both long haul and dynamic metro networks.

In recent years, high power diode lasers have become established in many applications like material processing, fiber laser and amplifier pumping, free space communication, direct printing and medical diagnosis and procedures. In particular, advances in laser diode packaging have resulted in devices with high wall-plug efficiency, enhanced reliability and low cost of ownership. Despite the advances of recent years, packaging, testing and reliability assurance still account for a majority of the cost of a fiber coupled laser diode. At MKPA-Panasonic, we are developing new fiber coupled laser diode package designs to enable low cost, high reliability assemblies that are amenable to high volume manufacturing. In this paper, we present a new low-profile, uncooled package for single-emitter high power laser diode packaging applications. Detailed design information, thermal modeling and reliability data for this small footprint, low profile optical flat package (OFP) with 4W output power in a 0.15NA, 100 micron core fiber is presented. The unique packaging technology resulting in good thermal and reliability performance in uncooled environments is discussed. All the assembly processes for the package are performed in a flux-free environment. The package is devoid of epoxy and can be hermetically sealed for high reliability operation. A reduced bill of materials and assembly steps result in significant cost savings. The design eliminates all non-vertical assembly processes for ease of assembly. Other features include passive die attach and integrated fiber mount. This package is specifically designed to address the fiber laser pump, industrial material processing, solid state laser pumping, printing and medical application markets.

We present a novel optoelectronic package incorporating Vertical-Cavity Surface-Emitting Laser (VCSEL) arrays with built-in power monitors. The power monitor consists of a thin film amorphous silicon p-i-n photodetector that is fabricated on glass. Sets of micro-machined springs for electrical contacting are also fabricated in the same process on the same glass substrate. The springs are made by sputtering, masking, and releasing a stress-engineered conductive thin film. The stress-engineered film is patterned into electrical routing wires whose ends curl up into compliant springs when released from the substrate. Hybrid packages are formed by pressing the micro-machined springs against individual contact pads of the GaAs VCSEL array in a flip-chip assembly process. The power monitor is designed so it lies directly in front of the laser array in the path of the light after module assembly. Although only about 2% of the laser power is absorbed by the sensor, a large signal to noise ratio is retained because of the sensor’s extremely low dark current. Our typical laser output powers of about 1 mW at wavelengths of 811 nm produces power monitor photocurrents of 0.5 to 1 μA, which, for our detectors, correspond to dynamic ranges of over five orders of magnitude.

Nonblocking crossconnect photonic switches based on light beam deflection require planar optical modules with hybrid integration of active deflector chips. In this work we present optical modules with two dimensional silica microlens arrays and slab waveguides fabricated on silicon substrates. The 1.55 μm light is launched in the input microlens array, which collimates parallel beams propagating along the module. The slab waveguide vertically confines the light. The output microlenses focus the beams laterally into output fibers. Two chips are inserted in the light path after the input microlens and before the output microlens arrays. The input and output microlenses allow propagation of the light beams through modules up to 100 mm long with a beam width of less than 400 μm. A hybrid integration process flow is developed to place the deflector chips in the light path with high alignment accuracy. The chips are flip-chip bonded to the substrate with submicron accuracy in the vertical positioning. Various contributions can lead to the chip displacements such as, for example, standoff island height variations, aligner tolerances, substrate bow, etc. Experiments are conducted to evaluate the effect of chip displacement on the insertion losses of the hybrid-integrated modules. 100-mm long optical modules with input and output chips are fabricated with less than 4 dB insertion losses. The analysis of loss contributions and possibilities for improvements are discussed.

Based on radiation mode coupling through a self-formed polymer waveguide extension, efficient single-mode optical coupling can be achieved between active and passive chips while relaxing the stringent positioning requirements. A 20dB improvement can be achieved according to simulation results. Single-mode waveguides have been successfully demonstrated using GE photo-definable polymer materials.

We describe the development of a high-speed, 12-channel (8-data, 2-clock and 2-alignment channels), parallel optical link with a unique packaging concept. The package is used to demonstrate the viability of chip-to-chip optical I/O in very large scale integration (VLSI) circuits. However, for implementation of optical systems in high performance computing applications, the cost of components and packaging has to come down significantly from the traditional optical communication distances. In the current work we attempted to realize such a system by using power efficient optical and electronic components together with a potentially low cost packaging solution compatible with the electronics industry. Vertical Cavity Surface Emitting Lasers (VCSEL), positive-intrinsic-negative (PIN) photodetectors, polymer waveguide arrays as well as CMOS transceiver chip were heterogeneously integrated on a standard microprocessor flip-chip pin grid array (FCPGA) substrate. The CMOS transceiver chip from 0.18μm processing technology contains VCSEL drivers, transimpedance and limiting amplifiers and on-chip self-testing circuits. A self-test circuit in such high-speed systems will be highly beneficial to reduce the testing cost in real products. For fully assembled packages we measured a 3 Gb/s optical eye for the transmitter (24Gb/s aggregate data rate) and a transmission over the complete link was achieved at 1 Gb/s (8Gb/s aggregate data rate).

The drive to faster data transmission speeds, more integration, smaller form factors and higher signal integrity all favor the eventual adoption of optical transmission schemes in data buses. This contribution will discuss emerging technologies from Shipley Company, LLC to address the needs of optoelectronic signal transmission. In particular, the discussion will focus on materials and processes that are in development to function within existing printed circuit board (PCB) & microelectronic manufacturing schemes. One topic that is described in detail involves photo-patternable, polymer interconnect technologies. Another topic describes progress in Shipley’s ability to integrate these interconnects into prototypical PCB processes. Progress in connecting the planar waveguides to connectorization schemes will be also be described. Other topics include lithographic and patterning metrics, optical characteristics of interconnects, morphological features of patterned waveguides, integration and coupling considerations, thermal and mechanical properties of the system and general assembly processes..

With the ever-increasing need to solve larger and more complex problems, multiprocessing is attracting more and more research efforts. One of the challenges facing the multiprocessor designers is to fulfill in an effective manner the communications among the processes running in parallel on multiple multiprocessors. The conventional electrical backplane bus provides narrow bandwidth as restricted by the physical limitations of electrical interconnects. In the electrical domain, in order to operate at high frequency, the backplane topology has been changed from the simple shared bus to the complicated switched medium. However, the switched medium is an indirect network. It cannot support multicast/broadcast as effectively as the shared bus. Besides the additional latency of going through the intermediate switching nodes, signal routing introduces substantial delay and considerable system complexity. Alternatively, optics has been well known for its interconnect capability. Therefore, it has become imperative to investigate how to improve multiprocessing performance by utilizing optical interconnects. From the implementation standpoint, the existing optical technologies still cannot fulfill the intelligent functions that a switch fabric should provide as effectively as their electronic counterparts. Thus, an innovative optical technology that can provide sufficient bandwidth capacity, while at the same time, retaining the essential merits of the shared bus topology, is highly desirable for the multiprocessing performance improvement. In this paper, the optical centralized shared bus is proposed for use in the multiprocessing systems. This novel optical interconnect architecture not only utilizes the beneficial characteristics of optics, but also retains the desirable properties of the shared bus topology. Meanwhile, from the architecture standpoint, it fits well in the centralized shared-memory multiprocessing scheme. Therefore, a smooth migration with substantial multiprocessing performance improvement is expected. To prove the technical feasibility from the architecture standpoint, a conceptual emulation of the centralized shared-memory multiprocessing scheme is demonstrated on a generic PCI subsystem with an optical centralized shared bus.

We propose a new scheme of the lensed fiber employing a pyramid-shaped fiber (PSF) for coupling the high-power diode lasers into the single-mode fibers (SMFs). First, the PSF was fabricated by grinding technique and then heating in a fusing splicer to form a quasi-ellipsoidal endface which described by the symmetric radius of curvatures in two axes. For an optimum microlens with high coupling efficiency, the dominate radius of curvature is typically smaller than the fiber mode field diameter. The advantage of the PSF structure was to be able to form the microlenses with small dominate rdius of curvatures and high asymmetric ratios of radius of curvatures, and therefore, this novel PSF can form microlenses with high aspect ratios to match the far field of the 980nm high power diode lasers which were used in the application of erbium-doped fiber amplifier (EDFA). A coupling efficiency of 83% has been demonstrated. A simplified and practical model was propsed to predict the radius of curvatures in the fabrication. The calculation of divergence angles and aspect ratios of lensed fiber far-field patterns were included in this study.

We present a method for coupling from a single mode fiber, or fiber ribbon, into an SOI waveguide for integration with silicon opto-electronic circuits. The coupler incorporates the advantages of the tapered waveguides and prism couplers, yet offers the flexibility of planar integration. The coupler can be fabricated on a double polished silicon wafer using direct polishing or grayscale photolithography. Tapered waveguides or J-couplers are then used as lateral mode converters. An experimental setup with a rotational stage and a pneumatic plunger has been built for adjusting the incident angle and tunnel layer thickness, which are key factors in determining the coupling efficiency. When optimal coupling is achieved on the setup, the coupler can be packaged using epoxy bonding. Thus, a fiber-waveguide parallel coupler or connector can be easily constructed. Electromagnetic calculation predicts a coupling efficiency of 77%(-1.14dB insertion loss) for a silicon-to-silicon coupler with a uniform tunnel layer. The coupling efficiency is experimentally achieved to be 46%(-3.4dB insertion loss) excluding the loss in silicon and the reflections from the input surface and output facet.

The modeling, realization and characterization of photonic module based on the use of Low Temperature Co-fired Ceramics (LTCC) technology is reported. The 3D modeling of the system provides possibility to optimize structures, materials and components in order to achieve optimal performance for the final product and still maintain reasonably low fabrication costs. The cost-effectiveness in the product can be further optimized using an iterative optimization process, in which the effect of module manufacturing tolerances and assembly process tolerances is simulated by a VisVSA Monte-Carlo simulation. The tolerance distributions produced by a VisVSA simulation are used as input parameters together with optical component tolerances in an ASAP Monte-Carlo simulation, in which the final module optical performance distribution in simulated production is obtained. The module cost, performance and optical performance limited yield is possible to define with this iterative process. As an example of this kind of packaging modeling, we present a demonstrator module having a high-power multimode laser diode with a 1μm x 100μm emitting area coupled to a 62.5/125μm graded-index (NA=0.275) multimode fiber. The tolerance modeling results are verified by experimental characterization of the packaged prototypes. Measured coupling efficiencies were in good agreement with simulated ones, when the fiber NA was 0.2 or larger. The measured coupling efficiency, however, was 38% lower than simulated, when the fiber NA was 0.12. This was probably due to the laser mode structure difference between simulation model and reality. Coupling efficiency of 0.46 was obtained in a passively aligned demonstrator module, when the nominal value was 0.48.

Short-range optical interconnection is more emphasizing in high performance systems. Multimode waveguide array is considered as a major interconnection medium due to the relatively easy packaging with devices. The multimode fiber array conjunction with VCSEL and Pin photodiode array is widely used in board to board and/or system to system interconnection. We demonstrate a flexible optical waveguide film which was composed of VCSEL, photodiode array, multimode waveguide array and 45 degree micro mirror couplers. The flexible waveguide film has many potentials such as it can be integrated with typical rigid electronic board and free from geometrical constraint. The waveguide film with 45° mirror was fabricated on a flexible transparent substrate using soft molding technique and then thin film VCSEL and photo-detector array are integrated. Master structure of the waveguide, which has multimode waveguide array and 45° mirror structure was fabricated using conventional lithography and microtome technique.

We report on optical interconnection using laser direct writing on polymeric channel waveguides. The optical transmitters and receivers are designed and fabricated using commercially available integrated circuits. The optical interconnect packaging is achieved by laser writing the packaged polymeric channel waveguides from the pre-connected optical transmitters to the receivers with transmitters and receivers turned on to monitor the optical interconnection and packaging process.

Integration of high-speed parallel optical interconnects into printed wiring boards (PWB) is studied. The aim is a hybrid optical-electrical board including both electrical wiring and embedded polymer waveguides. Robust optical coupling between the waveguide and the emitter/detector should be achieved by the use of automated pick-and-place assembly. Different coupling schemes were analyzed by combining non-sequential ray tracing with Monte-Carlo tolerance simulation of misalignments. The simulations demonstrate that, with optimized optomechanical structures and with very low loss waveguides, it is possible to achieve acceptable total path loss and yield with the accuracy of automated assembly. A technical demonstrator was designed and realized to allow testing of embedded interconnects based on three different kind of optical coupling schemes: butt-coupling, and couplings based on micro-lens arrays and on micro-ball lenses. They were implemented with PIN and flip-chip-VCSEL arrays as well as 10-Gb/s/channel electronics onto LTCC-based (low-temperature co-fired ceramic) transmitter and receiver modules, which were surface mounted on high-speed PWBs. The polymer waveguides were on separate FR-4 boards to allow testing and characterization of alignment tolerances with different waveguides. With micro-lens array transmitter, the measured tolerances (±10 μm) were dominated by the thickness of the waveguides.

WDM is an enabling technology for future satellite communications to increase capacity of bandwidth and network efficiency. Polymer based substrate mode optical interconnects is advantageous over its competing technologies, such as waveguide and free space approaches, in terms of insertion loss, robustness, and packaging. In this paper, we will describe polymer substrate mode photonic interconnects and their reconfiguration functions for separation of coarse and dense wavelength channels.

An adaptive optical filter based on novel thermo-optic polymeric waveguide lattice filters is proposed. Unlike conventional interference or resonance based optical filter, the adaptive filter is based on thermo-optic two-port waveguide lattice filters, which can greatly reduce the size, complexity and considerably increase the tuning range of an optical filter. By employing integrated variable optical attenuators (VOA), which functioned as the dynamically reconfigurable filter coefficients, the profile of the filter can be dynamically controlled. The classical frequency sampling and step down recursion algorithms are used for the synthesis of the VOA filter coefficients. Simulation and preliminary experimental results show that a tuning range of 50nm can be realized with filter extinction ration of ~40dB. The larger tunaing range comes from the larger by thermo-optic (TO) coefficients of polymer materials. Since it is based on polymeric waveguides, this device can be easily integrated with other polymer waveguide devices such as optical switches, EO modulators, and thus form a building block for photonic intergrated circuits.