A novel low-loss four-bit bandpass filter using RF MEMS switches

This paper details the design and simulation of a novel low-loss four-bit reconfigurable bandpass filter that integrates microelectromechanical system(MEMS)switches and comb resonators.A T-shaped reconfigurable resonator is reconfigured in a'one resonator,multiple MEMS switches'configuration and used to gate the load capacitances of comb resonators so that a multiple-frequency filtering function is realized within the 7-16 GHz frequency range.In addition,the insertion loss of the filter is less than 1.99 dB,the out-of-band rejection is more than 18.30 dB,and the group delay is less than 0.25 ns.On the other hand,the size of this novel filter is only 4.4 mm×2.5 mm×0.4 mm.Our results indicate that this MEMS reconfigurable filter,which can switch 16 central frequency bands through eight switches,achieves a low insertion loss compared to those of traditional MEMS filters.In addition,the advantages of small size are obtained while achieving high integration.     

一种智能光网络中的亚毫秒光开关阵列

设计研制了一种亚毫秒级微机械光开关阵列.该阵列驱动电压为5V,开关时间小于750μs, 插入损耗在0.6 dB～0.8 dB之间,串扰<－70 dB.具有结构简单、成本低廉、可大规模集成的优点,能很好地解决智能光网络节点连接设备OADM快速信号转换和串扰问题.详细介绍了该光开关阵列实现原理,报告了器件性能测试,并应用FEA软件分析了开关单元中磁场和开关驱动过程.     

Effect of oxygen partial pressure on the structural and optical properties of dc reactive magnetron sputtered molybdenum oxide films

Molybdenum oxide films (MoO₃) were deposited on glass and crystalline silicon substrates by sputtering of molybdenum target under various oxygen partial pressures in the range 8 × 10⁻⁵–8 × 10⁻⁴ mbar and at a fixed substrate temperature of 473 K employing dc magnetron sputtering technique. The influence of oxygen partial pressure on the composition stoichiometry, chemical binding configuration, crystallographic structure and electrical and optical properties was systematically studied. X-ray photoelectron spectra of the films formed at 8 × 10⁻⁵ mbar showed the presence of Mo⁶⁺ and Mo⁵⁺ oxidation states of MoO₃ and MoO_3−x. The films deposited at oxygen partial pressure of 2 × 10⁻⁴ mbar showed Mo⁶⁺ oxidation state indicating the films were nearly stoichiometric. It was also confirmed by the Fourier transform infrared spectroscopic studies. X-ray diffraction studies revealed that the films formed at oxygen partial pressure of 2 × 10⁻⁴ mbar showed the presence of (0 k 0) reflections indicated the layered structure of α-phase MoO₃. The electrical conductivity of the films decreased from 3.6 × 10⁻⁵ to 1.6 × 10⁻⁶ Ω⁻¹ cm⁻¹, the optical band gap of the films increased from 2.93 to 3.26 eV and the refractive index increased from 2.02 to 2.13 with the increase of oxygen partial pressure from 8 × 10⁻⁵ to 8 × 10⁻⁴ mbar, respectively.     

Magnetically actuated bi-directional microactuators with permalloy and Fe/Pt hard magnet

Bi-directional polyimide (PI) electromagnetic microactuator with different geometries are designed, fabricated and tested. Fabrication of the electromagnetic microactuator consists of 10 μm thick Ni/Fe (80/20) permalloy deposition on the PI diaphragm by electroplating, high aspect ratio electroplating of copper planar coil with 10 μm in thickness, bulk micromachining, and excimer laser selective ablation. They were fabricated by a novel concept avoiding the etching selectivity and residual stress problems during wafer etching. A mathematical model is created by ANSYS software to analyze the microactuator. The external magnetic field intensity (H_ext) generated by the planar coil is simulated by ANSYS software. ANSYS software is used to predict the deflection angle of the microactuator. Besides, to provide bi-directional and large deflection angle of microactuator, hard magnet Fe/Pt is deposited at a low temperature of 300 °C by sputtering onto the PI diaphragm to produce a perpendicular magnetic anisotropic field. This magnetic field can enhance the interaction with H_ext to induce attractive and repulsive bi-directional force to provide large displacement. The results of magnetic microactuator with and without hard magnets are compared and discussed. The preliminary result reveals that the electromagnetic microactuator with hard magnet shows a greater deflection angle than that without one.     

A novel structural VO2 micro-optical switch

In this letter, a novel optical switch based on vanadium dioxide (VO₂) thin film on substrates of silicon (100) has been fabricated. The vanadium dioxide thin films were deposited by reactive ion beam sputtering followed by a post-annealing. The testing result shows the insertion loss of the optical switches is about 1–2 dB, and the extinction ratio is up to 26 dB. The speed of the switches is as fast as 60 ns.     

Maximum number of connectable laser diode optical switch (LDSW) systems

The maximum number of connectable laser diode optical switches (LDSWs) was studied through the baseband signal-to-noise ratio calculation. For an NRZ 100 Mbits^–1 PCM-IM signal, 60 stages of LDSWs can be connected with a 6-nm optical bandpass filter inserted after the last stage at an input signal level of –30 dB m and an internal gain of 16 dB. A PCM-IM signal of 10 Gbits^–1 can be transmitted through 130 stages of LDSWs at an internal gain of 8 dB and an input signal level of –20 dB m.     

A novel multifunctional electronic calibration kit integrated by MEMS SPDT switches

Design and simulation results of a novel multifunctional electronic calibration kit based on microelectromechanical system (MEMS) single-pole double-throw (SPDT) switches are presented in this paper. The short-open-load-through (SOLT) calibration states can be completed simultaneously by using the MEMS electronic calibration, and the electronic calibrator can be reused 10⁶ times. The simulation results show that this novel electronic calibration can be used in a frequency range of 0.1 GHz-20 GHz, the return loss is less than 0.18 dB and 0.035 dB in short-circuit and open-circuit states, respectively, and the insertion loss in through (thru) state is less than 0.27 dB. On the other hand, the size of this novel calibration kit is only 6 mm×2.8 mm×0.8 mm. Our results demonstrate that the calibrator with integrated radio-frequency microelectromechanical system (RF MEMS) switches can not only provide reduced size, loss, and calibration cost compared with traditional calibration kit but also improves the calibration accuracy and efficiency. It has great potential applications in millimeter-wave measurement and testing technologies, such as device testing, vector network analyzers, and RF probe stations.     

MRI dynamic range and its compatibility with signal transmission media

As the number of MRI phased array coil elements grows, interactions among cables connecting them to the system receiver become increasingly problematic. Fiber optic or wireless links would reduce electromagnetic interference, but their dynamic range (DR) is generally less than that of coaxial cables. Raw MRI signals, however, have a large DR because of the high signal amplitude near the center of k-space. Here, we study DR in MRI in order to determine the compatibility of MRI multicoil imaging with non-coaxial cable signal transmission. Since raw signal data are routinely discarded, we have developed an improved method for estimating the DR of MRI signals from conventional magnitude images. Our results indicate that the DR of typical surface coil signals at 3 T for human subjects is less than 88 dB, even for three-dimensional acquisition protocols. Cardiac and spine coil arrays had a maximum DR of less than 75 dB and head coil arrays less than 88 dB. The DR derived from magnitude images is in good agreement with that measured from raw data. The results suggest that current analog fiber optic links, with a spurious-free DR of 60–70 dB at 500 kHz bandwidth, are not by themselves adequate for transmitting MRI data from volume or array coils with DR 90 dB. However, combining analog links with signal compression might make non-coaxial cable signal transmission viable.     

Nonlinear optical properties of Cu nanocluster composite fabricated by 180 keV ion implantation

Metal nanocluster composite glass prepared by 180 keV Cu ions into silica with dose of 5×10¹⁶ ions/cm² has been studied. The microstructural properties of the nanoclusters has been verified by optical absorption spectra and transmission electron microscopy (TEM). Third-order nonlinear optical properties of the nanoclusters were measured at 1064 and 532 nm excitations using Z-scan technique. The nonlinear refraction index, nonlinear absorption coefficient, and the real and imaginary parts of the third-order nonlinear susceptibility were deduced. Results of the investigation of nonlinear refraction by the off-axis Z-scan configuration were presented and the mechanisms responsible for the nonlinear response were discussed. Third-order nonlinear susceptibility χ⁽³⁾ of this kind of sample was determined to be 8.7×10⁻⁸ esu at 532 nm and 6.0×10⁻⁸ esu at 1064 nm, respectively.     

Fabrication of pellicle beam splitters for optical bus application

The optical bus architecture for on-board applications requires a number of optical splitters with precise split ratios to route part of the input signal. Since hollow metal waveguide provides well collimated beams with very small gap loss, it opens the possibility of inserting discrete optical beam splitters (taps). The optical tap requires low excess loss, polarization insensitivity, temperature stability, minimized walk-off of the propagating beam, and cost effective manufacturing. By benefiting from the mature interference coating technology for polarization insensitivity and temperature stability, we design a pellicle beam splitter based on a static microelec tro-mechanical system (MEMS) and develop processes to fabricate pellicle splitters using wafer level bonding of silicon and glass substrates, with subsequent thinning to 20 μm. With the approaches described in this paper, we have demonstrated optical beam splitters with excess loss of less than 0.17 dB that operate at a data rate of 10 Gb/s showing a clean eye diagram while providing controlled split ratio and polarization insensitivity. We have demonstrated a high yielding MEMS based silicon processing platform which has the potential to provide a cost effective manufacturing solution for optical beam splitters.     

Boron and indium incorporation in GaP(0 0 1) surfaces by vapour deposition: Density-functional supercell calculations of the surface stability

Using surface supercells and the density-functional method, surface formation energies are calculated for probable GaP(0 0 1) reconstructions without and with indium or/and boron substitutions. Obtained surface stability diagrams provide surface compositions and surface structures in dependence on the growth conditions: indium atoms are built into the c(4 × 4) patterns under strongly P-rich conditions and into the β2(2 × 4) reconstruction under less P-rich conditions. Under In-rich and non-P-rich conditions, initial structures of metallic InGa phases are formed in the (2 × 4) mixed-dimer reconstruction. In the c(4 × 4) and (2 × 4) mixed-dimer patterns the full range of In:Ga content is accessible by variation of the In:Ga ratio in the gas phase. Boron can be built into the c(4 × 4) patterns of the GaP(0 0 1) surface in form of isolated atoms or nearest-neighbours under strongly P-rich and moderately to strongly B-rich conditions. The boron incorporation is strongly enhanced at the surface in respect to theoretical predictions for the bulk, what explains the larger content found experimentally. Assuming P-rich conditions, which are suitable for the growth of the ternary alloys, the obtained surface stability diagram for the quaternary (BInGa)P shows that nearly the full range of In:Ga content is accessible. However, the boron content in the alloy is restricted as found analogously for (BGa)P and is independent of the indium content. The expected increase of the boron content in presence of indium cannot be confirmed. Contrary to the analogous GaAs systems, boron atoms do not substitute phosphor atoms (antisite position) in GaP, (InGa)P, (BGa)P, and (BInGa)P.     

Flexible integration of optical switch with optical power splitting and attenuating functions for optical fiber-based networking applications

A flexible integration of optical switch with optical power splitting and attenuating functions has been proposed to optimally serve optical fiber-based networking applications. In this switch, an etched binary-slope sidewall reflector is electrostatically actuated in and out of the plane to manipulate optical signals between input and output optical fibers. The fabrication process is a simple combination of a bulk-silicon micromachining process and silicon-to-glass anodic bonding where fiber alignment grooves, reflectors and actuators are fabricated on the same silicon substrate. Ball-lensed fibers are assembled with the device to achieve high coupling efficiency. Performances of the fabricated devices are measured and discussed. The switching time is less than 9 ms at 31 V. The excess loss of the device is less than 3 dB and the controllable attenuation range is up to 38 dB at 139 V, respectively. Moreover, polarization-dependent loss is less than 0.7 dB in the whole attenuation and splitting range.     

A High-gain Wideband Antenna with Double Fabry-perot Cavities

A high-gain wideband antenna, using the electromagnetic resonances of double Fabry-Perot (F-P) cavities, is proposed. The two cavities are excited by a patch antenna placed in the cavities on top of the ground plane. One of the double F-P cavities is formed by a ground plane and a single metallic strips array, and the other consists of the patch and the metallic strips array. The two F-P cavities have different resonance points which yield the frequency bandwidth of 7% between 13.0 and 14 GHz with S₁₁ ≤ 10 dB, meanwhile, in this frequency region high gain is also obtained. Moreover, the center frequency and bandwidth could be adjusted by changing the cavity length. The high-gain wideband antenna was manufactured and measured. The measured VSWR is less than 2 from 13.3 GHz to 15.2 GHz, the measured gain is 13.5 dB at 13.5 GHz. In addition to that, a considerable improvement of 7 dB in terms of gain is obtained when compared to the same antenna without metallic strips.     

Serpentine Spring Corner Designs for Micro-Electro-Mechanical Systems Optical Switches with Large Mirror Mass

In this paper, we describe the design principles of serpentine springs with high reliability for the micro-electromechanical systems (MEMS) optical switches with large mirror mass. The most often seen failure mode of the MEMS optical switches under reliability tests is the breaking of these springs, which provide the restoring force for the MEMS actuators. The breaking points are usually at the turning corner of the serpentine springs when the MEMS optical switches are under a high G shock test or a vibration test. In order to overcome the difficulties, we redesigned the corner shapes of the springs with careful consideration. We will discuss the theoretical analysis and simulation modeling for the corner shapes of serpentine springs. MEMS optical switches with redesigned serpentine springs are fabricated and tested to prove the proposed design. The results show that the MEMS optical switches with new serpentine springs can pass rigorous reliability tests.     

Polarisation-insensitive strip-loaded waveguide for electro-optic modulators and switches

A polarisation-insensitive electro-optic (EO) waveguide consisting of a dye-doped TiO₂/SiO₂ slab and a SU-8 strip-loaded rib is designed and fabricated. By optimizing the refractive index and size of waveguide, a trade-off between polarisation-insensitive condition and large EO efficiency (optical field interaction with the EO material) is obtained. The average transmission loss of the waveguide is less than 2.0 dB/cm. A Mach-Zehnder (M-Z) interferometer intensity modulator based on this waveguide with excellent poling stability is fabricated and measured, exhibiting 7 V half-wave voltage with 1.8 cm EO interaction length and 2.7 cm total length. This strip-loaded structure is proved to be a valuable application in EO modulators and switches.     

Lasing characteristics of Rhodamine B and Rhodamine 6G as a sensitizer in sol–gel silica

We report lasing characteristics of Rhodamine B (Rh. B) in sol–gel silica under excitation with frequency-doubled Nd:YAG laser and sensitization with Rhodamine 6G (Rh. 6G). The principle of radiative energy transfer (from Rh. 6G to Rh. B) has been utilized as a longitudinally Rh. 6G laser (at 585 nm)-pumped Rh. B laser process in the same sample. Rh. B offers a high photostable and efficient laser dye in sol–gel silica sensitized with Rh. 6G; 75,000 shots as a laser half-lifetime of the sample and 24% efficiency at pumping intensity 0.1 J/cm² of 532 nm. Wavelength shift occurs from 606 to 630 nm in the Rh. B laser with increasing its concentration from 1×10⁻⁴ to 8×10⁻⁴ M. The measured optical gain for Rh. B sensitized with Rh. 6G in sol–gel silica is higher than that in ethanol. A new effect has been observed; at 1×10⁻⁴ M of Rh. B and 0.5×10⁻⁴ M of Rh. 6G mixture, the emitted color of laser is changed by changing the pump intensity of frequency-doubled Nd:YAG laser.     

Gain flattening technique for optical wireless front-end receiver considering various large window photodetectors

A novel gain flattening technique for an optical wireless front-end receiver structure involving a bootstrap transimpedance amplifier (BTA) integrated with a MEMS variable feedback capacitor has been demonstrated. The MEMS varicap replaces a fixed capacitance as the feedback element in the front end system to optimize the performance of the BTA in terms of its frequency response. The implementation of the MEMS device with a BTA optical front-end receiver was verified using CoventorWare ARCHITECT. The simulation results showed that the approach can significantly flatten the peaking gain by up to 14 dB, when considering a system with various photodetector capacitances, ranging in value from 100 pF to 1 nF.     

Study on a MEMS silicon-based non-silicon mirror for an optical switch

A micro-electro-mechanical system (MEMS) silicon-based non-silicon mirror for a 2D optical switch is designed, fabricated and measured. The result shows that the mirror has good reflective performance. And driven by static electricity, it can rotate more than 10° at voltage less than 15 V. This kind of novel mirror will have good potential applications for MEMS optical switches.     

A new form of optical transmission system using 1 × 6 optical switch

Optical switches are useful for various optical systems. This paper describes a new form of optical transmission system, using 1 × 6 optical switch with built-in optical multiplexer. The insertion loss of the optical switch was 3.1 dB (including filter loss of 1.4 dB). This switch is useful for a traffic monitoring system, and its transmission characteristics were measured. The measured signal-to-noise ratio is 44 dB when the switch is applied to a 2-km video transmission line.     

A comprehensive study of MEMS behavior under EOS/ESD events: Breakdown characterization,dielectric charging,and realistic cures

The breakdown characterization of both out- and in-plane electrostatically actuated RF–MEMS switches with air-gaps from 1.0 to 6.7 μm was studied. The emitted electromagnetic field during the testing was analyzed, in order to have an indication of the air-breakdown occurrence. Furthermore, we studied the effect of TLP and HBM events on the dielectric charging of tested MEMS, furnishing the experimental evidence that ESD events should not be responsible of this important reliability problem for MEMS, and that ESD tester parasitic elements can influence the MEMS electromechanical behavior characterization. Finally, a simple, but effective, varistor based protection structure was explored.