Adhesive joint design for minimizing fiber alignment shift during UV curing

In fiber-optic device packaging using UV curable adhesive bonding, the curing process often causes fiber alignment shift-distortion of the already aligned fiber-optic setups, and thus reduce the assembly yield. A new method for the adhesive joint design for minimizing fiber alignment shift during adhesive curing is reported in this paper. It is demonstrated that for any adhesive, the bonding joint can be designed to alleviate the alignment shift, regardless of adhesives used. The approach provides guideline for high yield and low-cost assembly of fiber-optic devices using adhesive bonding.     

Automatic Vision-Based Optical Fiber Alignment Using Multirate Technique

Automatic optical fiber alignment is the key to reducing the cost of the packaging process for the manufacturing of fiber-optic devices. This paper develops a vision-based active optical fiber alignment technique for coarse positioning using a piezoactuated moving platform that is controlled to reduce the alignment difference to within a certain degree. To overcome the adverse effect of the delay time between the motion control system and the vision system, the methodology based on the multirate control scheme is presented. Experimental results verify the effectiveness of the proposed approach.      

Silicon photodetector structure for direct coupling of optical fibers to integrated circuits

A novel detector structure exhibiting real-estate efficient coupling of optical fibers to semiconductor devices is described. The integrated fiber-optic coupler employs vertical insertion of a tapered single-mode fiber into a laser-etched cylindrical hole in the substrate. It features a small surface footprint, mechanical stability, and accurate alignment. Fabricated in silicon, the p-n junction detectors have typically shown responsivities of 0.23 A/W at 0.63 µm, corresponding to a quantum efficiency of 45 percent, and dark currents below 1 nA.     

MEMS integrated submount alignment for optoelectronics

One of the most expensive and time-consuming production processes for single-mode fiber-optic components is the alignment of the photonic chip or waveguide to the fiber. The alignment equipment is capital intensive and usually requires trained technicians to achieve desired results. Current technology requires active alignment since tolerances are only /spl sim/0.2/spl mu/m or less for a typical laser diode. This is accomplished using piezoelectric actuated stages and active optical feedback. Joining technologies such as soldering, epoxy bonding, or laser welding may contribute significant postbond shift, and final coupling efficiencies are often less than 80%. This paper presents a method of adaptive optical alignment to freeze in place directly on an optical submount using a microelectromechanical system (MEMS) shape memory alloy (SMA) actuation technology. Postbond shift is eliminated since the phase change is the alignment actuation. This technology is not limited to optical alignment but can be applied to a variety of MEMS actuations, including nano-actuation and nano-alignment for biomedical applications. Experimental proof-of-concept results are discussed, and a simple analytical model is proposed to predict the stress strain behavior of the optical submount. Optical coupling efficiencies and alignment times are compared with traditional processes. The feasibility of this technique in high-volume production is discussed.     

Energy‐Level Alignment at the Organic/Electrode Interface in Organic Optoelectronic Devices

It is commonly believed that the work‐function reduction effect of the cathode interfacial material in organic electronic devices leads to better energy‐level alignment at the organic/electrode interface, which enhances the device performance. However, there is no agreement on the exact dipole direction in the literature. In this study, a peel‐off method to reveal the buried organic/metal interface to examine the energy‐level alignment is developed. By splitting the device at different interfaces, it is discovered that oppositely oriented dipoles are formed at different surfaces of the interfacial layer. Moreover, the function of the electrode interface differs in different device types. In organic light‐emitting diodes, the vacuum‐level alignment generally occurs at the organic/cathode interface, while in organic photovoltaic devices, the Fermi‐level pinning commonly happens. Both are determined by the integer charge‐transfer levels of the organic materials and the work‐function of the electrode. As a result, the performance enhancement by the cathode interfacial material in organic photovoltaic devices cannot be solely explained by the energy‐level alignment. The clarification of the energy‐level alignment not only helps understand the device operation but also sets up a guideline to design the devices with better performance.     

Free-space fiber-optic switches based on MEMS vertical torsionmirrors

This paper reports on the design, fabrication, and performance of a novel MEMS (micro-electro-mechanical-system) fiber-optic switch based on surface-micromachined vertical torsion mirrors. The vertical torsion mirror itself can be used as a 1×2 or an ON-OFF switch. A 2×2 MEMS fiber-optic switch with four vertical torsion mirrors has also been fabricated. The switching voltage is measured to be 80 V for switching angles of 45°. We have achieved a switching time of less than 400 μs (fall time) and an optical insertion loss of 1.25 dB for single-mode fibers. In addition, a bulk-micromachined silicon submount has been developed to package the switch with microball lenses and multimode fibers with passive alignment. With the micromachined switch chip and the hybrid-packaging scheme, the size, weight, and potentially the cost of the fiber-optic switches can be dramatically reduced     

Methods for passive fiber chip coupling of integrated opticaldevices

A useful technique for high precision passive coupling of single mode optical fibers to integrated optical devices is crucial for cost effective packaging especially in multiport devices like switches (N×N) and other WDM components. These devices were fabricated on two different material bases, silicon on insulator (SOI) and polymers. In both cases the waveguides are based on the oversized rib waveguide concept and utilize silicon as a substrate. Two possible fabrication processes for this passive fiber chip coupling IN or ON silicon are presented and compared. The first approach involves a technology similar to flip chip fabrication using a sub- and superstrate, that allows separate processing of v-grooves for fiber alignment and the integrated optical devices. The self aligned mounting of the chip is achieved by a v-shaped rib-groove combination created by wet chemical etching, where the rib is the exact negative of the groove so that the flip chip is put on precisely defined crystal planes rather than on sensitive edges, which would be the case when using rectangular alignment ribs. The second approach utilizes the same chip for waveguides and fiber alignment structures which makes it possible to define both in the same lithographic step and thereby eliminating any vertical displacement. Processing difficulties arise primarily from completely different processing requirements of fiber aligning v-grooves and integrated waveguides. The need to define patterns of the size of only several microns (μm) in the proximity to deep grooves makes the use of an electrophoretic photoresist necessary that is deposited via galvanic means on the extremely nonplanar surface. Both processes allow for fiber chip alignment precisions in the sub-μm range which was also experimentally verified with coupling losses as low as 0.7 dB per end-face. The fabrication processes along with experimental and theoretical results are presented     

Fiber-optic devices for local area network application

Recent developments on fiber-optic devices are reviewed from the local area network (LAN) application viewpoint. Future technical trends are also discussed, along with current research activities. In local area network systems, low device cost and easy maintenance or maintenance-free devices are especially required. Light sources and photodetectors suitable for the systems are described. InGaAsP/InP light emitting diodes can cover a broad application field, up to a gigabits per second super high-speed network region. Optical passive devices, which include branching couplers, switches and connectors, are mentioned as essential components. Compact transmitter/receiver module technology is a key factor in realizing optical-fiber local area network systems. An example of 200-Mbit/s transmitter/receiver module is reported.     

Novel intelligent automation method for out-of-plane fiber-laser alignment in the presence of initial nonplanar misalignments: three-point approach

A novel and cost-effective method is developed for the roll alignment automation for out-of-plane coupling between a laser and an angled facet single-mode fiber. The method is based on an approximated closed-form analytical formula for the functional dependence of out-of-plane laser-fiber coupling efficiency on relative rotational angle between fiber and laser. In this method, only three measurements are needed to locate maximum optical power coupling position in the presence of initial fiber-laser relative rotational angular misalignments. This intelligent searching method can easily be incorporated into any conventional fiber-optic alignment optimization algorithms and is sufficiently general for alignment automation of even more complicated out-of-plane fiber-optic alignment in the presence of initial nonplanar misalignments.     

Fiber-Optic Transceiver Module for High-Speed Intrasatellite Networks

High-speed intrasatellite networks are needed to interconnect units such as synthetic aperture radars, high-resolution cameras, and fast image-compression processors that produce data beyond gigabits per second. We have developed a fiber-optic link, named SpaceFibre, which operates up to 3.125 Gb/s and is compatible with the existing SpaceWire network. The link provides symmetrical, bidirectional, full-duplex, and point-to-point communication. It employs 850-nm vertical-cavity surface emitting lasers, radiation-hardened laser-optimized 50/125 mum graded-index fibers, and GaAs p-i-n photo diodes. The transceiver electronics is realized using a multilayer-ceramic-substrate technology that enables the passive alignment of optical fibers to active devices. The SpaceFibre link demonstrator was tested to transfer data at 2.5 Gb/s over 100 m with a bit error rate of less than 1.3middot10^-14. Fiber-pigtailed modules were stressed with temperature variations from -40degC to +85degC, vibrations up to 30 g, and mechanical shocks up to 3900 g. The test results of 20 modules show that the SpaceFibre link is a promising candidate for the upcoming high-speed intrasatellite networks     

An innovative technique for packaging power electronic buildingblocks using metal posts interconnected parallel plate structures

Power electronics building blocks (PEBBs) are envisioned as integrated power modules consisting of power semiconductor devices, power integrated circuits, sensors, and protection circuits for a wide range of power electronics applications, such as inverters for motor drives and converters for power processing equipment. At the Center for Power Electronics Systems, we developed a topology for a basic building block-a two-switch two-diode half-bridge converter in totem-pole configuration with built-in gate-driver and protection circuitry, fiber-optic receiver/transmitter interface, and soft-switching capability. Based on the topology, a series of prototype modules, with 600 V, 3.3 kW rating, were fabricated using an innovative packaging technique developed for the program-metal posts interconnected parallel plate structure (MPIPPS). This new packaging technique uses direct attachment of bulk copper, not wire-bonding of fine aluminum wires, for interconnecting power devices. Electrical performance data of the packaged devices show that an air-cooled 15 kW inverter, operating from 400 V dc bus with 20 kHz switching frequency can be constructed by integrating three prototype modules, which is almost double what could be achieved with commercially packaged devices of the same rating     

40 Gbit/s PIN/TIA组件光纤耦合分析与实验研究

文章对40 Gbit/s PIN/TIA组件的光纤耦合进行了理论分析,并进行了一些实验研究.通过使用紫外胶和精细固化方法, 进行了光纤耦合固定,使得40 Gbit/s PIN/TIA组件灵敏度达到国内领先水平.经测试,40 Gbit/s PIN光纤精细对准后的响应度可达0.65 A/W,耦合固定后的光响应度超过0.46 A/W.     

Sage_Husa自适应滤波在大方位失准角初始对准的研究

由于光纤惯导系统导航精度不高,方位角常为大角度,因此系统初始对准的滤波方程为非线性的,为改善非线性模型下初始对准的精度,提出了一种改进Sage_Husa自适应卡尔曼滤波方法并应用于光纤惯导系统初始对准中。建立了大方位失准角初始对准的非线性误差模型,给出了Sage_Husa自适应卡尔曼滤波方程,对Sage_Husa自适应卡尔曼滤波不适合用在非线性滤波的缺陷进行了改进,建立系统噪声统计的估值器,对非线性误差方程进行了改进Sage_Husa自适应卡尔曼滤波仿真。仿真结果表明:改进Sage_Husa自适应卡尔曼滤波能够很好地处理初始对准中的非线性问题,提高初始对准精度,方位失准角误差估计精度较EKF提高27%。     

Design and development of optoelectronic mixed signal system-on-package (SOP)

This paper describes the design and development of a 2.5-Gb/s optical transceiver module as a mixed signal SOP for access networks. The module development consists of concurrent design of an optoelectronic package optimizing optical, electrical, thermal, mechanical functions and optical subassembly and RFICs housed in a chip-on-board package. The optical subassembly (OSA) consists of laser and photodiode assembled on a silicon substrate. The transmit and the receiver sections are combined into a single fiber through a polymer coupler on silicon. The splitter between the transmit and receive section is realized using a polymer waveguide. The electronic ICs are assembled on a multilayer organic substrate. The package design includes optical coupling design, impedance matched transmission line design for RF signals, electrical layout design for mixed signals and thermal design for the package. The module is housed in a plastic molded nonhermetic package to achieve low cost packaging. The assembly is completed using passive alignment of optical devices and attachment of electronic devices using adhesives. In this paper, we present the details of the component design and the development of packaging process methods to achieve the design specifications, test results and process guidelines for assembly and integration.     

带框LTCC生瓷烘干技术

在LTCC基板加工中,生瓷预烘干、图形印刷后烘干可能会产生中心位置塌陷、破损、翘曲等形变问题.而LTCC是通过加工多层生瓷、按一定顺序准确对准,再层压、切割后共烧而成,为满足产品平整度及位置对准精度要求,我们必须解决各层烘干过程中存在的形变问题,保证每一层生瓷加工质量.文章介绍了LTCC基板制造过程中带框生瓷烘干的工艺...     

Assembly of laser-fiber arrays

This paper describes techniques and machinery for first-level packaging of laser-to-fiber interconnects using batch assembly and active alignment. These techniques are economical because the costs of labor-intensive processes, such as parts handling, fiber-polishing, and alignment, are shared among the many elements of the array. Using these techniques, prototype packages have been built consisting of 32-wide arrays of 1300 nm lasers coupled to 32-wide arrays of single-mode fiber-optic stubs. Building the package involves three steps: (1) preparing the laser array for handling and alignment by soldering it to a metallized silicon carrier; (2) building the fiber array by stripping the fibers, placing them precisely into etched silicon V-grooves, bonding them in place, and polishing both ends; and (3) aligning the two arrays to each other using batch, active alignment. Batch alignment succeeds to the extent that each array is collinear, so the collinearity achieved in processes (1) and (2) is crucial. Typically, collinearity of ±1 μm or better is achieved for each array. When such arrays are batch aligned using the techniques described herein, the average coupling efficiency is about 88% as large as it would be if each laser-fiber pair were optimally aligned individually     

Fully Stable and Homogeneous Lyotropic Liquid Crystal Alignment on Anisotropic Surfaces

Lyotropic chromonic liquid crystals have great potential in both biosensing and optical devices due to their biocompatible nature and strong optical characteristics. These applications, however, demand a homogeneous and stable alignment on anisotropic surfaces, a challenge that, so far, has not been solved adequately. In this work, it is shown how to drastically increase the quality of in‐plane alignment and stability of these liquid crystals on conventional rubbed polyimide substrates by the addition of a small amount of a nonionic surfactant. Samples with surfactant show excellent alignment that is stable for months, while control samples without surfactant show much poorer alignment that further deteriorates in days. Also, well‐aligned dry films of chromonics can be prepared following this approach. It is demonstrated how to obtain high‐quality alignment by controlling the concentration and the nature of the surfactant, in particular its molecular structure and hydrophilic/lipophilic balance (HLB value) and other critical parameters are discussed. It is believed that this approach may very well be essential for advancing the applicability of these water‐based, biocompatible, and often highly dichroic materials for a wide range of uses.     

Manufacturing of laser diode modules: Integration and automation of laser diode-fiber alignment and RIN characterization

Laser diode-fiber alignment and relative intensity noise (RIN) characterization are two crucial steps to the manufacturing of fiber pigtailed laser diode modules. Integrating both steps into a single automatic process can increase yield, improve the throughput and reduce manufacturing cost. This work presents a novel scheme of the integrated laser-diode-to-fiber alignment and RIN testing automation for the manufacturing of Fabry-Perot (FP) laser diode module hosted in a low cost isolator-free coaxial-type package. It is demonstrated that the value of RIN is not only determined by the intrinsic spontaneous emission of the laser diode, but also strongly dependent on the fiber-laser alignment and pigtailing process. It is experimentally determined, for the first time, that regardless of the type of lensed fiber employed for fiber-laser coupling, and with or without the presence of angular misalignment, there is an optimal fiber-laser alignment location at which the RIN value reaches its minimum. Moreover, it is observed that both RIN minimization and laser power coupling maximization occur at the same fiber-laser alignment position.     

Aligned microcontact printing of biomolecules on microelectronicdevice surfaces

Microcontact printing (muCP) of extracellular matrix proteins is a fascinating approach to control cell positioning and outgrowth, which is essential in the development of applications ranging from cellular biosensors to tissue engineering. Microelectronic devices can be used to detect the activity from a large number of recording sites over the long term. However, signals from cells can only be recorded at small sensitive spots. In this paper, we present an innovative setup to perform aligned muCP of extracellular matrix proteins on microelectronic devices in order to guide the growth of electrogenic cells specifically to these sensitive spots. Our system is based on the combination of a fine-placer with redesigned micro stamps having a rigid glass cylinder as backbone for attachment in the alignment tool. Alignment is performed moving the device with an optical table under microscopic control of the superimposed images from stamp and device surface. After successful alignment, the stamp is brought into contact with the device surface by means of a high-precision lever. With our setup, we were able to pattern up to 40 devices per hour. A lateral alignment accuracy of < 2microm has been achieved. Aligned neuronal growth on patterned devices was demonstrated with dissociated hippocampal neurons.     

Laser welding induced alignment distortion in butterfly lasermodule packages: effect of welding sequence

Welding-induced-alignment-distortion (WIAD) is a serious issue in fiber-optic component attachment using laser welding, which can significantly affect the packaging yield. Elimination or minimization of WIAD is expected to be possible if the laser welding process and all relevant packaging parameters can be optimized. The effect of laser welding sequence on WIAD for butterfly laser diode packages is reported for the first time in this work. The results demonstrate that WIAD deduction can be as high as 96% if an appropriate welding sequence is employed