A transparent sheet display by plastic MEMS

Abstract— A new type of color‐image display pixel based on MEMS (microelectromechanical systems) technology of plastic materials is presented. The mechanism for making color is optical interference using a Fabry‐Perot interferometer. A thin sheet of PEN (polyethylene naphthalate) with a metal half‐mirror was laminated over a glass or PEN substrate with an optical cavity inside. The electrostatically controlled deformation of the PEN film changes the color of the transmitting light by interference within the optical cavity. Color pixels of three primary colors (red, green, and blue) were successfully developed and demonstrated, with a driving voltage ranging from 80 to 120 Vdc. Thanks to the mechanical flexibility of the PEN films, the display could operate even when placed on a curved surface.     

Finite element analysis and experimental validation of suppression of span in optical MEMS pressure sensors

Microsystem Technologies - An optical pressure sensor working on the principle of Fabry–Perot Interferometer (FPI) is designed for pressures range of 1 bar absolute. The sensor is...     

A new inhomogeneous partially reflecting surface for Fabry‐Perot antenna to reduce side lobe level

In this article, an extension of the spatial filter method to study Fabry‐Perot antennas with homogeneous or inhomogeneous partially reflecting surface (PRS) of finite size is proposed. This tool was subsequently validated through the study of different Fabry‐Perot antennas, with homogeneous PRS and inhomogeneous GRadient‐INdex (GRIN) PRS that present very high side lobe level (SLL). Since they are due to structure truncation, a new inhomogeneous PRS to reduce the SLL is designed with the new analytical tool. The new inhomogeneous PRS for Fabry‐Perot antenna is characterized by simulations and measurements. Compared to the homogeneous PRS antenna, the proposed PRS allows a SLL reduction of 5 dB without decreasing the 14 dBi directivity.     

光纤法珀腔声传感器理论与仿真分析研究

根据干涉原理,对基于低精细度法珀腔的光纤声传感器的敏感机理进行了理论分析,明确了采用单色光源工作时需要满足正交相位点和小信号的条件。采用ANSYS软件,对敏感声波的振膜进行了预应力振动模态和预应力谐响应有限元分析,仿真了在声波作用下振膜的振动特性,以及其频率响应特性。进一步分析了光纤法珀腔声传感器的灵敏度与材料、结构、光学、电学参量的关系,以及它的动态范围。     

High‐gain waveguide slot antenna using simple parasitic patch's cover

In this article, a way based on using miniature patch cells has been proposed to increase gain and bandwidth of the waveguide slot antenna. In the presented approach, an array of 3 × 3 metal patches has been used as superstrate to create Fabry Perot theorem resonance cavity. The proposed high ‐ gain and simple antenna is composed of a conventional waveguide slot antenna with an extended broad wall, and an array of parasitic patches which are symmetrically placed over slot at a distance of about free ‐ space half wavelength. The slot has been created on a rectangular waveguide WR90 with 22.86 mm × 10.16 mm × 52.5 mm dimension, also extended wall dimension is 2λ₀ (67.5 mm) × 3λ₀ (107 mm). It has been shown that the proposed structure compared with the conventional waveguide slot antenna improves antenna peak gain from 6.5 to 16.5 dBi and, in the same time, antenna bandwidth from 11% to around 16.2%. More important advantage of the proposed antenna is that unlike to other Fabry Perot antenna with the same gain, there is not any dielectric material in the proposed structure. A prototype antenna was simulated, fabricated, and measured for verification.     

双干涉式微位移测量系统的研究与性能改善􀀁

本文提出了光扫描光纤传输双Ｆａｂｒｙ－Ｐｅｒｏｔ干涉系统用于测量绝对为微位移,该系统把扫描波长作为内部转换参数,采用参考长度与敏感头间隙长度比较,从而得到绝对测量值。     

Developing stable optical fiber refractometers using PMDI with two-parallel Fabry–Perots

The paper presents a new approach to developing an optical fiber refractometer. The objective of the study is to come up with a relatively inexpensive but reliable optical refractometer that can be used to measure the change of refractive index in a resolution of 10⁻⁵ and to work in a dynamic range up to 6×10⁻³ at a DC frequency of up to 100 Hz. It is known that the phase modulations of optical fiber sensors are very sensitive to external disturbances, especially to the effects of thermal drifts or vibrations. A cancellation technique to compensate the effect of variation on a PZT stack is proposed in this paper to stabilize the system. Two parallel Fabry–Perot sensing cavities corresponding to two path-matching cavities for read-out systems are employed to form path-matching differential interferometries (PMDI). One Fabry–Perot cavity is used as sensing head, and the other as reference sensor. As a result, the experimental data show that the change of refractive index of a so designed sensing system can be kept in at the level of 10⁻⁴ without any serious variations even for a 3-h long-term monitoring. Accordingly, the proposed new system can be easily implemented and used as a long-term monitoring system in a medical care environment.     

Fabrication of a thin plasmonic color sheet embedded with Al subwavelength gratings in parylene

In this study, we developed a thin plasmonic color sheet (TPCS) embedded with Al subwavelength gratings for use in flexible optical transmission filters, and experimentally demonstrated its transmission characteristics. Al subwavelength gratings were formed in a freestanding thin poly-para-xylylene (parylene-N) film less than 1-μm thick by using electron beam (EB) direct writing and sacrificial etching. The fabricated TPCS contained Al subwavelength gratings with periods ranging from 400 nm to 600 nm, and succeeded in shifting the transmission peak wavelength from 510 nm to 650 nm in the visible range. The freestanding thin parylene-N film deposited by room-temperature chemical vapor deposition provided enough flatness to the TPCS with a height difference of 900 nm in a whole filter area, resulting in uniform transmission spectra. The experimentally obtained peak shift dependent on the grating period agreed well with theoretical calculation results.     

Thermal and Optical Characterization of Silicon-Based Tunable Optical Thin-Film Filters

In this paper, we report on the successful fabrication and comprehensive optical and electrothermal characterization of a silicon-based tunable optical filter. Of particular interest here are the static and transient electrothermal characteristics of the filter membrane. The filter is configured as a Fabry-Perot resonator with dielectric Bragg reflectors and is fabricated as a stress-compensated multilayer of dielectric thin-films. Tunability is achieved by changing the refractive index of the solid-state cavity material through thermal modulation, accomplished by Joule heating in metal thin-film resistors. The filter layers are configured as a membrane to provide good thermal isolation and its electrothermal behavior was characterized in steady-state and dynamically. A maximum stable temperature difference of 450 K and a heating efficiency of 13.4 K mW^-1 were measured with a thermal time constant for the filter hotplate of 3 ms. The filter's spectral width is 0.28 nm at a wavelength of 1550 nm and through thermal modulation it was possible to shift the filter peak over more than 29 nm.     

Design,modeling, and mechanical characterizations of micromachined InP-based actuator for tunable MOEMS applications

A novel InP-based microactuator, which is actuated by electrostatic means, has been proposed, designed, fabricated, and characterized for tuning applications in the 1.5 μm wavelength domains. Its structural design is based on the global optimization method. The tunable device is a big square membrane, which is supported by four identical cantilever beams. The three alternating layers Si₃N₄/SiO₂ as a distributed Bragg reflector (DBR) mirror, which were previously reported, have been formed on the top of the membrane. Based on the optical interferometric measurements, the proposed Fabry–Perot filter has demonstrated a maximum deflection of ∼321 nm with an applied voltage up to 12 V, an average sensitivity of ∼27 nm/V, a pull-in voltage of 12.7 V, and a release voltage of 10.7 V. It is also observed that its natural frequency is 88.4 kHz. This measured frequency implies that the tuning speed of our device is fast for optical operations within 0.01 ms. In addition, our device’s mirror remains so flat with a good planarity of 0.07°, which is strictly required for the filter’s optical performance. This optical performance can be achieved, when the micromachined structure has a tuning displacement up to ∼38 nm with a low tuning voltage up to 5 V. When compared with the finite element models (FEM), which were generated by the commercialized software, Coventor™, our experimental results agree well in terms of the natural frequency, pull-in voltage and deflections. Thus, our tunable filter, which is based on the optimized design, enables better performances including reduced actuation voltages, large pull-in voltage, improved device reliability, and fast switching times. Our device can also quickly snap back to the original position. In addition, the undesired spring-softening effect has been reduced.     

Novel interconnection technology for heterogeneous integration of MEMS�CLSI multi-chip module

We developed novel interconnection technology for heterogeneous integration of MEMS and LSI multi-chip module, in which MEMS and LSI chips would be horizontally integrated on substrate and vertically stacked each others. The cavity chip composed of deep Cu TSV-beam lead interconnections was developed for interconnecting MEMS chips with high step height of more than few hundreds micrometer without the degradation of sensing elements. Fundamental characteristics were successfully obtained from pressure sensing MEMS chip with 360 μm thickness, which was connected to Si substrate by the cavity chip. MEMS and LSI chips were vertically integrated by using the cavity chip without any changing of chip design and extra processes. This interconnection technology can give strong solution for heterogeneous integration of MEMS and LSI chips multi-chip module.     

Optical micro-paddle beam deflection measurement for electrostatic mechanical testing of nano-scale thin film application to MEMS

The authors describe their design for a paddle-like cantilever beam sample to relieve non-uniform stress distribution in beam-bending tests of the mechanical properties of thin film applications to MEMS. We added the sample to a custom-designed system equipped with an electrostatic panel and optical interferometer. The system overcomes problems associated with using nano-indentation for testing, and reduces errors tied to the amount of contact force required to bend the beam. Accurate paddle cantilever beam deflection was obtained using a four-step phase-shifting process with a Michelson interferometer. Film strain was determined using a simple force equilibrium equation. Residual stresses were measured at −41.3 MPa for 150 nm silver film, −3.2 MPa for 150 nm gold film, and −16.8 MPa for 150 nm copper film. We observed residual stresses for copper films at different thicknesses. The results indicate high tensile stress forms during the early deposition stage for thin copper film due to grain coalescence, and a decrease in stress with an increase in film thickness. In copper films with thicknesses greater than 153 nm, lattice relaxation associated with the surface mobility of metallic atoms changed residual stress from tension to compression.     

High-resolution electrostatic analog tunable grating with a single-mask fabrication process

We present the design, modeling, fabrication, and characterization of the microelectromechanical systems (MEMS) analog tunable diffraction grating with the concept of transverse actuation. In contrast to the vertically actuated "digital" tunable grating, our prototype design trades angular tunable range for tuning resolution. The prototype shows an angular tunable range of 250 /spl mu/rad with 1-/spl mu/rad resolution at 10 V. Grating pitch changes corresponding to the full range and resolution are 57 nm and 2.28 /spl Aring/, respectively confirmed by experimental measurement and theoretical calculation. Simulation shows that subradian tunable range is feasible with better lithographic design rules or higher actuation voltage. The single-mask fabrication process offers several advantages: 1) Excellent optical flatness; 2) ease of fabrication; and 3) great flexibility of device integration with existing on-chip circuitry. Tunable gratings such as the one presented here can be used for controlling dispersion in optical telecommunications, sensing, etc., applications.     

Flexible thin‐film transistors application of amorphous tin oxide‐based semiconductors

The structural, optical, and electrical properties of Si‐doped SnO₂ (STO) films were investigated in terms of their potential applications for flexible electronic devices. All STO films were amorphous with an optical transmittance of ~90%. The optical band gap was widened as the Si content increased. The Hall mobility and carrier density were improved in the SnO₂ with 1 wt% Si film, which was attributed to the formation of donor states. Si (1 wt%) doped SnO₂ thin‐film transistor exhibited a good device performance and good stability with a saturation mobility of 6.38 cm²/Vs, a large I_on/I_off of 1.44 × 10⁷, and a SS value of 0.77 V/decade. The device mobility of a‐STO TFTs at different bending radius maintained still at a high level. These results suggest that a‐STO thin films are promising for fabricating flexible TFTs.     

Crystallization of amorphous‐Si using nanosecond laser interference method

Laser crystallization of a 50‐nm thick amorphous‐Si (a‐Si) thin film on glass substrate was examined by a Nd:YAG (λ = 1064 nm) nanosecond laser and a two‐beam laser interference method. In spite of the low absorption rate of the laser wavelength in the a‐Si, crystallized Si ripple patterns were observed following a single laser pulse irradiation. The atomic force microscope (AFM) measurement revealed that surface ripple arrays are protruded as high as 120 nm at the positions corresponding to the maximum laser intensity and the ripples are composed of narrow double peaks with a separation of 1 μm. Raman image mapping was used to plot the spatial distribution of the crystallized Si phase. It was found that a 1064‐nm‐wavelength nanosecond laser could crystallize an a‐Si thin film into polycrystalline‐Si (poly‐Si) by nonlinear absorption under high laser energy irradiation.     

基于强度解调的Fabry－Perot型光纤MEMS压力传感器

运用微机械系统加工技术制作了一种新型法布里-珀罗干涉型光纤微机电系统压力传感器,该传感器通过测量反射光谱的移动测量压力.运用多腔干涉原理对该传感器进行理论以及模拟分析得出,通过改变压力传感器的尺寸可较容易的调节压力线性测量范围和灵敏度.实验结果表明,在压力线性测量范围[0.1～1.0]MBa内,灵敏度可达到12.71 nm/MPa(光谱移动/压力).     

Novel tunable laser sources with 1.5-μm and 1.57-μm cascaded DFB reflectors for in situ gas monitoring applications

Novel tunable lasers based on 1.5-μm and 1.57-μm cascaded distributed-feedback reflectors are realized for real-time monitoring of H₂O and CO gas mixtures immediately in multi-gas sensor systems. With simple fabrication procedures, the new design allows the realization of a widely tunable laser source that can cover the H₂O and CO absorption wavelength bands. With the temperature tuning of 0.1 nm/°C and current tuning of 0.014 nm/mA, the laser can be tuned to cover over 3 nm wavelength range in each wavelength band. Experiments verify that the lasers can have more than 38 dB SMSR over the tuning range. The characteristics of high power, excellent spectral purity, and simple wavelength switching control can simplify the analysis procedures of gas sensing and thus reduce the cost. By direct absorption method, the tunable laser has been successfully adopted in a diode laser sensor system for monitoring of water vapor concentration near 1.5 μm and carbon monoxide near 1.57 μm. Less than 15% error in the line strength is observed between the measured data and HITRAN database.     

Widely Tunable MEMS-Based Fabry–Perot Filter

This paper describes the use of strain stiffening in fixed-fixed beam actuators to extend the tuning range of microelectromechanical-systems-based Fabry–Perot filters. The measured wavelength tuning range of 1.615–2.425 $muhbox{m}$ is the largest reported for such a filter. Curvature in the movable mirror was corrected using a low-power oxygen plasma to controllably alter the stress gradient in the mirror. After curvature correction, the linewidth of a filter was 52 nm, close to the theoretical minimum for our mirror design. As a proof of concept, a filter was bonded to a broadband infrared detector, realizing a wavelength-tunable infrared detector. All measured data have been compared to theoretical models of the optics and mechanics of the filters, with excellent agreement between theory and measurement demonstrated in all cases. Finally, the Young's modulus and stress of the actuator materials were extracted directly from the measured voltage–displacement curves, demonstrating a novel technique for material property measurement.$hfill$[2009-0070]      

Application of a parallel DSMC technique to predict flowcharacteristics in microfluidic filters

Using a parallel implementation of the direct simulation Monte Carlo (DSMC) method, periodic MEMS microfilters are studied in detail. The dependence of the flow characteristics on geometry, Knudsen number, pressure difference, spacing between the filter elements, and accommodation coefficients are investigated. By comparing DSMC results with the widely used analytical formulas, the validity range of the analytical approaches is evaluated. The simulation results show that velocity slip exists both on the filter channel walls and on the filter membrane and results in an increased flow rate. Velocity slip increases strongly with decreasing accommodation coefficients. For long channels, this results in a strong increase in flow rate; whereas for short channels, the increase in flow rate is limited. For the filter separations considered in this paper, we observe that separation between filter channels does not influence the flow rate within each channel     

一种基于体硅工艺的微机械可调节椭圆低通滤波器

提出了一种椭圆低通可调滤波器的调谐方法,即通过调节第一传输零点(FTZ)来改变3 dB截止频率Tc.解析计算表明,小范围内改变FTZ既可调节Tc和滚降速率,又能保证通带和阻带的特性基本不变.作者提出FTZ的移动可由串联谐振支路处容性MEMS开关的分布加载来实现,并基于微扰法求出器件中心谐振频率及特性的变化规律.本文相应设计了Tc为16 GHz的7阶步进式滤波器.高频有限元全波仿真表明,每加载一个MEMS开关,Tc改变约1.5 GHz,损耗特性则几乎不变.这证明了理论分析方法有较高的准确性,而且器件设计具有数字化调节能力和较出色的微波性能.这种方法也可用于高通和带通滤波器.论文还介绍了器件的体硅微加工流程及MEMS开关的初步加工结果.