Crystalline silicon tilting mirrors for optical cross-connect switches

This paper discusses a two-piece approach for fabricating two-dimensional (2-D) arrays of tilting MEMS mirrors with application in very-large optical cross-connect switches. In the new process, a two-sided etching of silicon-on-insulator (SOI) wafers is used to create crystalline mirrors on a first wafer that is later aligned and bonded to a separate wafer containing the activation electrodes, traces, and bond pads. The approach allows a very close spacing of mirror elements and a very simple design for the mechanical structures, and also greatly simplifies wire routing.     

A monolithically integrated surface micromachined touch mode capacitive pressure sensor

A monolithically integrated surface micromachined touch mode capacitive pressure sensor and its interface circuits are presented. The device includes the capacitance to voltage, and capacitance to frequency converters on the same chip. The sensor is fabricated using a surface micromachining technology, which is processed simultaneously with a conventional 2.0-μm double-poly, double-metal n-well CMOS process. The performance of the integrated sensor meets the design specifications of good linearity and good stability. Evaluation results on the completed ‘sensor and circuit' chip are presented.     

A fully integrated surface micromachined magnetic microactuatorwith a multilevel meander magnetic core

A fully integrated magnetic microactuator using surface micromachining techniques is presented. To achieve this device, low-resistance meander conductors located in a single plane were interwoven with multilevel meander magnetic cores. This `wrapped' solenoid (with the core wrapped around the conductor) was fabricated in a fully integrated fashion. A magnetic microactuator was realized by incorporating a surface micromachined nickel-iron cantilever beam as part of the magnetic circuit of the core. The nickel-iron cantilever beam was 2.5 μm thick, 25 μm wide, and 780 μm long, and the magnetic circuit contained seventeen turns of meander-type solenoid coils. Cantilever beam tip deflection of 6 μm in the vertical direction was achieved when a DC voltage less than 1 V (and resulting drive current of 800 mA) was applied to the coils. This fully integrated multilevel topology offers advantages in a variety of micromagnetic applications, where actuators can be fabricated on the same substrate with an integrated circuit and actuated with low voltages     

Packet mode and QoS algorithms for buffered crossbar switches with FIFO queuing

The buffered crossbar switch architecture has recently gained considerable research attention. In such a switch, besides normal input and output queues, a small buffer is associated with each crosspoint. Due to the introduction of crossbar buffers, output and input dependency is eliminated, and the scheduling process is greatly simplified. We analyze the performance of switch policies by means of competitive analysis, where a uniform guarantee is provided for all traffic patterns. We assume that each packet has an intrinsic value designating its priority and the goal of the switch policy is to maximize the weighted throughput of the switch. We consider FIFO queueing buffering policies, which are deployed by the majority of today’s Internet routers. In packet-mode scheduling, a packet is divided into a number of unit length cells and the scheduling policy is constrained to schedule all the cells contiguously, which removes reassembly overhead and improves Quality-of-Service. For the case of variable length packets with uniform value density (Best Effort model), where the packet value is proportional to its size, we present a packet-mode greedy switch policy that is 7-competitive. For the case of unit size packets with variable values (Differentiated Services model), we propose a β-preemptive (β is a preemption factor) greedy switch policy that achieves a competitive ratio of 6 + 4β + β ² + 3/(β − 1). In particular, its competitive ratio is at most 19.95 for the preemption factor of β = 1.67. As far as we know, this is the first constant-competitive FIFO policy for this architecture in the case of variable value packets. In addition, we evaluate performance of β-preemptive greedy switch policy by simulations and show that it outperforms other natural switch policies. The presented policies are simple and thus can be efficiently implemented at high speeds. Moreover, our results hold for any value of the internal switch fabric speedup.     

A fully integrated micromachined magnetic particle separator

A prototype micromachined magnetic particle separator that can separate magnetic particles from suspended liquid solutions has been realized on a silicon wafer. The requisite magnetic field gradients are generated by integrated inductive components in place of permanent magnets, which yields several advantages in design flexibility, compactness, electrical and optical monitoring, and integration feasibility (thus enabling mass production). Preliminary experiments have been performed on aqueous suspensions of magnetic beads. At 500 mA of dc current, approximately 0.03 Tesla of magnetic flux density is achieved at the gap between the quadrupoles, and the magnetic particles rapidly move toward the quadrupoles, separate from the buffer solution, and clump on the poles. The magnetic particles clumped on the poles are also easily released when the dc current is removed, achieving the primary purpose of a separator. The device shows that micromachined magnetic components have a high potential in biological or biomedical applications, especially in separating small amounts of cells or DNA that are marked with magnetic beads, especially when close monitoring and control of the process is important     

Linearization of electrostatically actuated surface micromachined2-D optical scanner

This paper presents an effective method of linearizing the electrostatic transfer characteristics of micromachined two-dimensional (2-D) scanners. The orthogonal scan angles of surface micromachined polysilicon scanner are controlled by using quadrant electrodes for electrostatic actuation. By using a pair of differential voltages over a bias voltage, we could improve the distortion of projected images from 72% to only 13%. A theoretical model has been developed to predict the angle-voltage transfer characteristics of the 2-D scanner. The simulation results agree very well with experimental data. Differential voltage operation has been found to suppress the crosstalk of two orthogonal scan axes by both experiment and theoretically. We have found that a circular mirror is expected to have the lowest angular distortion compared with square mirrors. Perfect grid scanning pattern of small distortion (0.33%) has been successfully obtained by predistorting the driving voltages after calibration     

表面微机械MEMS温度传感器研究

提出一种基于表面微机械工艺的MEMS温度传感器,其基本原理是：由于材料热膨胀系数的差异,复合悬臂梁在热应力作用下发生弯曲,进而影响压阻单元中的应力分布,压阻变化通过惠斯登电桥读出,由电桥输出电压变化表征温度的变化。相比于其他温度传感器,这种微机械温度传感器的灵敏度高、尺寸小、精度高。针对提出的温度传感器结构,文中给出了传感器的设计原理、制备工艺以及信号检测电路的设计。经测试,传感器的灵敏度为9.2 mV/℃,具有良好的稳定性。     

Performance enhancement in buffered delta networks using crossbar switches and multiple links

It is shown that the throughput of buffered delta networks can be increased substantially by modifying the structure and operation of their crossbar switches, by using multiple links to connect the switches in the network, or by combining multiple delta networks in parallel. The variations tried in the structure of the crossbar switches are the size of the switch and the number of buffers in each switch, their capacity, and their position in the switch. Among the alternatives mentioned above, the use of two parallel links for each switch connection results in the highest throughput improvement.     

Bulk micromachined tunneling tips integrated with positioning actuators

We have successfully developed an integrated micromechanical system for controlling tunneling current. A pair of nanoscale tunneling tips have been integrated with a silicon micromachined electrostatic actuator of high-aspect ratio. The tip sharpness has been observed to be as sharp as commercial tips by scanning over surface of carbon graphite as an atom scale. We have also succeeded to observe the tunneling current in the air and in the vacuum condition (in TEM).     

MEMS optical switches and interconnects

This paper reviews several optical connecting devices that are based on microelectromechanical systems (MEMS) components. In this paper, we divide optical connecting devices into two categories. The first category includes MEMS-based optical switches developed for optical fiber communication, which perform optical switching, wavelength division multiplexing (WDM) routing, and/or optical cross connection. The other category consists of MEMS-based optical interconnects that have been constructed primarily for use in rack-to-rack, board-to-board, chip-to-chip, card-to-card and/or intra-chip interface connections. Working principles of these MEMS optical connecting devices will also be discussed in this paper.     

Convert-and-Deliver: a scalable multicast optical cross-connect with reduced power splitting fan-out

Powerful computing systems interconnected via high-bandwidth wavelength division multiplexing (WDM) fibers are becoming inevitable to meet the needs of emerging computation and communication applications. Enabling multicast over WDM links requires the use of multicast-capable optical cross-connects (MC-OXCs) equipped with power splitters to replicate and interconnect an input signal on a particular wavelength to one or more output fibers, possibly on different wavelengths. All existing design approaches for FW×FW strictly nonblocking MC-OXCs with F fibers, each carries W wavelengths require the use of power splitters with a fan-out degree of O(FW). For typical large values of F and W, complex and power-consuming active devices are needed to compensate for the lost power due to splitting. In this paper, we propose a new class of strictly nonblocking MC-OXC, namely, the Convert-and-Deliver (CAD) cross-connect to reduce power consumption. The new CAD OXC uses power splitters with a fan-out degree of only O(F) instead of O(FW). It is shown that, making the fan-out degree independent of W in the proposed design does not only reduce splitting power loss considerably, but it also enhances the scalability of the design. In particular, for any value of F, upgrading the number of wavelengths per fiber does not incur any changes to the fan-out degree or the power loss in the used splitters; a feature that cannot be obtained with any existing MC-OXC design approach.     

Tunable Fabry-Perot surface micromachined interferometer-experiments and modeling

We present an optical tunable Fabry-Perot micromachined interferometer. The device is monolithically integrated with a p⁺-n photodiode on a silicon substrate, providing an adequate positioning of the photonic and microoptical components. The Fabry-Perot micro-interferometer consists of two parallel mirrors and lets the light with a particular wavelength pass through. The wavelength depends on the gap between the mirrors. We can change the gap of the micro-mechanical Fabry-Perot interferometer by applying a voltage to the mirrors, an electrostatic force inducing an attraction between the substrate and the top mirror. A simulation of the mechanical behavior was performed based on finite elements, using CoventorWare software. The method included an electro-mechanical simulation for a square parallel plate actuation with four connecting beams. The finite elements method (FEM) simulations of the device (the Fabry-Perot tunable filter) are performed for optimizing the design parameters in order to model the overall system performance, both the steady-state behavior and dynamic response.     

Capacitive microphone with a surface micromachined backplate usingelectroplating technology

A technology for surface micromachining of free-standing metal microstructures using metal electrodeposition on a sacrificial photoresist layer has been applied to a condenser microphone. Electroplating technology has been used to implement a suspended and perforated 15-μm-thick microstructure in copper, which serves as backplate electrode in the condenser microphone. The 1.8×1.8 mm ² large microphone diaphragm is in monocrystalline silicon and is fabricated with anisotropic etching of the substrate wafer. The realized prototypes have a measured sensitivity of 1.4 mV/Pa using a bias voltage of 28 V. The bandwidth is limited by an anti-resonance at 14 kHz which is due to the semi-rigid backplate. The resonance behavior of the backplate structure has been analyzed with finite element modeling with results in good agreement with measured data     

Optical properties of surface micromachined mirrors with etch holes

We have investigated the optical properties of surface-micromachined polycrystalline silicon reflectors within the visible spectral range at five different wavelengths. The measurement results of the reflectivity of various microreflectors at four different incident angles (20°, 30°, 45°, and 60°) are presented. Optical properties of microreflectors realized using the multiuser MEMS process (MUMPS) have been investigated. Our studies have found that etch holes, widely used in the surface micromachining process to reduce the time for releasing structures by sacrificial undercutting, have a great influence on the optical properties of micromachined mirrors. Diffraction patterns created by two-dimensional etch-hole arrays on micromachined mirrors have been investigated. The diffraction by etch holes obeys the Fraunhofer diffraction theory when a collimated light source (e.g., a laser beam) is incident. We have shown that when the dimension of etch holes increases, an increasing portion of the incident power will be diffracted and transmitted due to etch holes, leading to decreasing reflectivity of surface micromachined mirrors     

Preemptive and non-preemptive scheduling of optical switches with configuration delay

Utilizing optical technologies for the design of packet switches and routers offers several advantages in terms of scalability, high bandwidth, power consumption, and cost. However, the configuration delays of optical crossbars are much longer than that of the electronic counterpart, which makes the conventional slot-by-slot scheduling methods no longer the feasible solution. Therefore, some tradeoff must be found between the empty time slots and configuration overhead. This paper classifies such scheduling problems into preemptive and non-preemptive scenarios, each has its own advantages and disadvantages. Although non-preemptive scheduling is inherently not good at achieving the above-mentioned tradeoff, it is shown, however, that the proposed maximum weight matching (MWM) based greedy algorithm is guaranteed to achieve an approximation 2 for arbitrary configuration delay, and with a relatively low time complexity O(N2). For preemptive scheduling, a novel 2-approximation heuristic is presented. Each time in finding a switch configuration, the 2-approximation heuristic guarantees the covering cost of the remaining traffic matrix to have 2-approximation. Simulation results demonstrate that 2-approximation heuristic (1) performs close to the optimal scheduling, and (2) outperforms ADJUST and DOUBLE in terms of traffic transmission delay and time complexity.     

InP-based optical waveguide MEMS switches with evanescent coupling mechanism

An optical waveguide MEMS switch fabricated on an indium phosphide (InP) substrate for operation at 1550 nm wavelength is presented. Compared to other MEMS optical switches, which typically use relatively large mirrors or long end-coupled waveguides, our device uses a parallel switching mechanism. The device utilizes evanescent coupling between two closely-spaced waveguides fabricated side by side. Coupling is controlled by changing the gap and the coupling length between the two waveguides via electrostatic pull-in. This enables both optical switching and variable optical coupling at voltages below 10 V. Channel isolation as high as -47 dB and coupling efficiencies of up to 66% were obtained with switching losses of less than 0.5 dB. We also demonstrate voltage-controlled variable optical coupling over a 17.4 dB dynamic range. The devices are compact with 2 /spl mu/m/spl times/2 /spl mu/m core cross section and active area as small as 500 /spl mu/m/spl times/5 /spl mu/m. Due to the small travel range of the waveguides, fast operation is obtained with switching times as short as 4 /spl mu/s. Future devices can be scaled down to less than 1 /spl mu/m/spl times/1 /spl mu/m waveguide cross-sectional area and device length less than 100 /spl mu/m without significant change in device design.     

The evolution of solitons in coupled resonator optical waveguides and photonic-crystal waveguides

We successfully used the tight binding theory to derive the extended discrete nonlinear Schrödinger equation to describe the soliton propagation and to obtain the soliton propagation criteria (SPC) in the nonlinear photonic-crystal waveguides (PCWs) and coupled resonant optical waveguides (CROWs) containing Kerr media. From these criteria, we obtain the soliton-propagating region of CROWs in different numbers of separated rods and strengths of self-phase modulation (SPM). The defined soliton-propagating regions coincide with the regions of modulation instability in the CROWs. In the PCWs, the positive Kerr coefficient medium needs to be added to support the pulse propagation in low frequency or low wave vector region of the dispersion curve; while negative Kerr effect is for high frequency case. Due to the linear combination of various cosine harmonic functions in the dispersion relations of both CROWs and PCWs, the pulse broadening which is mainly caused by the third-order dispersion at SPC is the lowest at the boundary of dispersion curves. However, due to the different magnitudes of coupling coefficients in CROWs and PCWs, the group velocity, dispersion and strength of SPM in CROWs are all smaller than those in PCWs.     

Asymmetric surface roughness measurements and meniscus modeling of polysilicon surface micromachined flaps

Polycrystalline silicon (polysilicon) films are primary structural materials for microelectromechanical systems (MEMS). Due to relatively high compliance, large surface-to-volume ratio, and small separation distances, micromachined polysilicon structures are susceptible to surface forces which can result in adhesive failures. Since these forces depend on surface properties especially surface roughness, three types of microhinged flaps were fabricated to characterize their roughness and adhesive meniscus properties. The flaps enabled access to both the top and bottom surfaces of the structural polysilicon layers. Roughness measurements using an atomic force microscope revealed that MEMS surfaces primarily exhibit non-Gaussian surface height distributions, and for the release procedures studied, the bottom surface of the structural layers was significantly smoother and prone to higher adhesion compared to the top surface. A non-symmetric surface roughness model using the Pearson system of frequency curves was coupled with a capillary meniscus adhesion model to analyze the effects of surface roughness parameters (root-mean-square, skewness, and kurtosis), relative humidity, and surface contact angle on the interfacial adhesion energy. Using the measured roughness properties of the flaps, four different surface pairs were simulated and compared to investigate their effects on capillary adhesion. It was found that since the base polysilicon layer (poly0) was rougher than the base silicon nitride and the structural layer on poly0 was also rougher than that on silicon nitride, depositing MEMS devices on poly0 layer rather than directly on silicon nitride will reduce the adhesion energy.     

Surface- and bulk- micromachined two-dimensional scanner driven by angular vertical comb actuators

In this paper, we present the design, fabrication, and measurements of a two-dimensional (2-D) optical scanner with electrostatic angular vertical comb (AVC) actuators. The scanner is realized by combining a foundry-based surface-micromachining process (Multi-User MEMS Processes-MUMPs) with a three-mask deep-reactive ion-etching (DRIE) postfabrication process. The surface-micromachining provides versatile mechanical design and electrical interconnect while the bulk micromachining offers high-aspect ratio structures leading to flat mirrors and high-force, large-displacement actuators. The scanner achieves dc mechanical scanning ranges of /spl plusmn/6.2/spl deg/ (at 55 Vdc) and /spl plusmn/4.1/spl deg/ (at 50 Vdc) for the inner and outer gimbals, respectively. The resonant frequencies are 315 and 144 Hz for the inner and the outer axes, respectively. The 1-mm-diameter mirror has a radius of curvature of over 50 cm. [1454].     

A design method and its CAD prototype system for surface micromachined MEMS devices

Microsystem Technologies - Now the MEMS design method of “bottom–up” (mask-to-shape-to-function) has been adopted widely. However, it is complicated, time-consuming and not...