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[IEEE 2019 IEEE/MTT-S International Microwave Symposium - IMS 2019 - Boston, MA, USA (2019.6.2-2019.6.7)] 2019 IEEE MTT-S International Microwave Symposium (IMS) - Silicon-Micromachined Waveguide Calibration Shims for Terahertz Frequencies
摘要： A new method of realising precision waveguide shims for use in THz Through-Re?ect-Line (TRL) calibrations, based on silicon-micromachining, is introduced. The proposed calibration shims combine a thin λ/4 silicon layer, co-fabricated with a thicker layer which provides mechanical support. This design overcomes the limitations of CNC milling for the creation of calibration shims, facilitating use of standard TRL calibration at currently challenging frequencies. The novel shim ?ts inside the inner recess of a standard waveguide ?ange and is compatible with conventional ?ange alignment pins. Five micromachined shims were fabricated in a silicon-on-insulator process for operation in the WM-570 waveguide band (325 – 500 GHz). The fabricated shims show excellent performance across the entire band, with return loss in excess of 25 dB, insertion loss below 0.2 dB and high uniformity between samples. Veri?cation reveals that the micromachined shims have an electrical length within 2% of the expected value. Comparative measurements of a DUT calibrated with the proposed shim and a previously un-used conventional metallic shim show that the novel concept offers equivalent, if not better, performance. The mechanical design of the micromachined shim and the rigid nature of silicon ensure that it will not suffer from performance degradation with repeated use, as is problematic with thin metallic shims. This work enables the creation of low-cost, highly-repeatable, trace- able calibration shims with micrometer feature-sizes and high product uniformity, surpassing the limits of current techniques.
关键词： calibration,micromachining,TRL,terahertz,waveguide,THz
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - SiC-SiO <sub/>2</sub> MEMS-DBR Based Widely Tunable Optical Filters Around 1550 nm with Narrow FWHM
摘要： Ever growing optical data transmission networks and miniaturization of spectroscopic equipment demand for small, energy efficient and mass-produced optical components. Here we present distributed Bragg reflector (DBR) mirror based widely tunable optical Fabry-Perot filters comprising a novel material combination namely, silicon carbide (SiC) and silicon dioxide (SiO2) layers with refractive indices of 2.46 and 1.45, respectively. The resulting refractive index step of 1, provides high reflectivities (>99.5 %) with wide stopbands of more than 300 nm. Hence, large wavelength tuning range and a narrow full width at half maximum (FWHM) filtered signals can be produced. Structuring the dielectric layers by surface micromachining creates a free standing movable mirror supported by four beams. Due to inherent stress created during low-temperature plasma enhanced chemical vapor depositions (PECVD) we obtain a tunable stable plane concave resonator. In the end the cross section of a filter shows a fixed bottom DBR deposited on a silicon substrate, a tunable airgap and an electrothermally actuated top MEMS DBR with a gold electrode for heating current IMEMS. On the substrate backside where the filtered signal is exiting an anti-reflection coating is deposited.
关键词： tunable optical filters,SiC-SiO2 MEMS-DBR,PECVD,Fabry-Perot filters,surface micromachining
更新于2025-09-11 14:15:04
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Femtosecond Laser Micromachining of Fabry-Pérot Interferometers for Magnetic Field Sensing
摘要： Fs-laser micromachining is a high precision fabrication technique that can be used to write novel three-dimensional structures, depending on the nature of light-matter interaction. In fused silica, the material modification can lead to (i) an increase of the refractive index around the focal volume, resulting in the formation of optical circuits, or (ii) an enhancement of the etch rate of the laser-affected zones relative to the pristine material, leading to a selective and anisotropic etching reaction that enables fabrication of microfluidic systems. Here, both effects are combined to fabricate a Fabry-Pérot interferometer, where optical waveguides and microfluidic channels are integrated monolithically in a fused silica chip. By filling the channel with a magnetic fluid whose refractive index changes with an external magnetic field, the device can be used as a magnetic field sensor. A linear sensitivity of -0.12 nm/mT is obtained in the 5.0±0.5 to 33.0±0.5 mT range, with the field being applied parallel to the light propagation direction.
关键词： Magnetic Field Sensing,Optofluidic Sensor,Femtosecond Laser Micromachining,Ferrofluids,Fabry-Pérot Interferometers
更新于2025-09-11 14:15:04
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A Low-Profile and High-Gain Frequency Beam Steering sub-THz Antenna Enabled by Silicon Micromachining
摘要： A very low-profile sub-THz high-gain frequency beam steering antenna, enabled by silicon micromachining, is reported for the first time in this paper. The operation bandwidth of the antenna spans from 220 GHz to 300 GHz providing a simulated field of view of 56?. The design is based on a dielectric filled parallel-plate waveguide (PPW) leaky-wave antenna fed by a pillbox. The pillbox, a two-level PPW structure, has an integrated parabolic reflector to generate a planar wave front. The device is enabled by two extreme aspect ratio, 16 mm x 16 mm large perforated membranes, which are only 30 μm thick, that provide the coupling between the two PPWs and form the LWA. The micromachined low-loss PPW structure results in a measured average radiation efficiency of ?1 dB and a maximum gain of 28.5 dBi with an input reflection coefficient below ?10 dB. The overall frequency beam steering frontend is extremely compact (24 mm x 24 mm x 0.9 mm) and can be directly mounted on a standard WM-864 waveguide flange. The design and fabrication challenges of such high performance antenna in the sub-THz frequency range are described and the measurement results of two fabricated prototypes are reported and discussed.
关键词： beam steering,leaky-wave antennas,silicon on insulator,terahertz radiation,silicon micromachining,quasi-optics,submillimeter-wave antennas
更新于2025-09-11 14:15:04
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Effects of Laser Fluence and Pulse Overlap on Machining of Microchannels in Alumina Ceramics Using an Nd:YAG Laser
摘要： The quality of micro-features in various technologies is mostly affected by the choice of the micro-fabrication technique, which in turn results in several limitations with regard to materials, productivity, and cost. Laser beam micro-machining has a distinct edge over other non-traditional methods in terms of material choices, precision, shape complexity, and surface integrity. This study investigates the effect of laser fluence and pulse overlap while developing microchannels in alumina ceramic using an neodymium-doped yttrium aluminum garnet (Nd:YAG) laser. Microchannels 200 μm wide with different depths were machined using different laser peak fluence and pulse overlap (percentage of overlap between successive laser pulses) values. It was found that high pulse overlaps and fluences should be avoided as they give rise to V-shaped microchannels i.e., 100% bottom width errors. The optimal peak fluence range was found to be around 125–130 J/cm2 corresponding to 3–5 μm depth per scan. In addition, channels fabricated with moderate pulse overlap were found to be of good quality compared to low pulse overlaps.
关键词： microchannels,laser,fluence,alumina,micromachining
更新于2025-09-11 14:15:04
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Compact silicon-micromachined wideband 220-330 GHz turnstile orthomode transducer
摘要： This paper reports on a turnstile-junction orthomode transducer (OMT) implemented by silicon micromachining in the 220 – 330 GHz band. Turnstile OMTs are very wideband and allow for co-planar ports, but require accurate and complex geometries which makes their fabrication challenging at higher frequencies. The compact 10 x10 x0.9 mm3 OMT-chip presented in this paper is the first micromachined full-band OMT in any frequency range, and only the second turnstile OMT implemented above 110 GHz. The measured insertion loss (0.3 dB average, 0.6 dB worst-case) and the cross-polarization (60 dB average, 30 dB worst-case) over the whole waveguide band represent the best performance of any wideband OMT, regardless of design or fabrication technology, in the 220 – 330 GHz band. The return loss with 22 dB average (16 dB worst-case) is comparable or better than previous work. The paper discusses design considerations and compromises of this complex 9 layer silicon micromachined device, including the influence of sidewall slopes, underetching, and post-bonding misalignment between the chips. It is shown that for a device which is very sensitive to geometrical variations, such as a turnstile OMT, it is necessary to anticipate and compensate for any fabrication imperfections in the design to achieve high RF performance.
关键词： terahertz,mmW,DRIE,orthomode transducer,turnstile,silicon micromachining,THz,millimeter wave,MEMS,OMT
更新于2025-09-11 14:15:04
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An Investigation of Processes for Glass Micromachining
摘要： This paper presents processes for glass micromachining, including sandblast, wet etching, reactive ion etching (RIE), and glass reflow techniques. The advantages as well as disadvantages of each method are presented and discussed in light of the experiments. Sandblast and wet etching techniques are simple processes but face difficulties in small and high-aspect-ratio structures. A sandblasted 2 cm × 2 cm Tempax glass wafer with an etching depth of approximately 150 μm is demonstrated. The Tempax glass structure with an etching depth and sides of approximately 20 μm was observed via the wet etching process. The most important aspect of this work was to develop RIE and glass reflow techniques. The current challenges of these methods are addressed here. Deep Tempax glass pillars having a smooth surface, vertical shapes, and a high aspect ratio of 10 with 1-μm-diameter glass pillars, a 2-μm pitch, and a 10-μm etched depth were achieved via the RIE technique. Through-silicon wafer interconnects, embedded inside the Tempax glass, are successfully demonstrated via the glass reflow technique. Glass reflow into large cavities (larger than 100 μm), a micro-trench (0.8-μm wide trench), and a micro-capillary (1-μm diameter) are investigated. An additional optimization of process flow was performed for glass penetration into micro-scale patterns.
关键词： reactive ion etching,wet etching,sandblast,glass reflow process,glass micromachining
更新于2025-09-10 09:29:36
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A MEMS Accelerometer Based on Wavelength Modulation Using an Integrated Blazed Grating
摘要： This paper reports a MEMS optical fiber accelerometer with an integrated blazed grating as wavelength modulation component. The accelerometer includes a V-shape cantilever beam, a vertically symmetrical proof mass and an integrated blazed grating. The accelerometer prototype is fabricated with bulk micromachining processes and is tested. The bandwidth of the accelerometer is 200Hz. The optical sensitivity and nonlinearity of the measure range ±5.2g is 1.63nm/g @100Hz and 0.06% respectively. The x-axis and y-axis cross-axis sensitivities are 2% and 4.5% respectively. In the full temperature range of -20?C to 200 ?C, the temperature sensitivity is 2.8pm/ ?C. Thanks to the mentioned characteristics, the proposed MEMS accelerometer could have a wide range of applications, such as rail traffic and attitude heading sensing applications.
关键词： blazed grating,microsensors,optical fiber sensors,micromachining,Accelerometers,Microelectromechanical systems
更新于2025-09-10 09:29:36
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Progresses in Chemical Sensor || Air-Suspended Silicon Micro-Bridge Structures for Metal Oxide- Based Gas Sensing
摘要： Maintaining specific temperature is a key parameter for most of the gas sensing materials, particularly for metal oxide-based thin film layers, to operate them more efficiently to detect different gaseous (or vapor) species at ppm and ppb concentration levels. For field applications, battery-operated micro-gas-sensors, power dissipation and the required temperature stability are to be maintained with a close tolerance for better signal stability and also to analyze the generated data from the sensing element. This chapter mainly focuses on several metal oxide films to highlight the base temperature and its creation on silicon-based platforms. Air-suspended structures are highlighted, and a comparison is drawn between simple and MEMS-based structures from the power dissipation point of view. Ease of fabrication and operation limitations are explained with fabrication issues.
关键词： Platinum resistance thermometer,Gas sensing devices,Platinum micro-heater,Surface micromachining,MEMS,Metal oxide thin films
更新于2025-09-09 09:28:46
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Nano- and Microfabrication for Industrial and Biomedical Applications || Basic technologies for microsystems
摘要： This chapter introduces the reader the processes used to manufacture microelectronics. A silicon wafer is coated with a resist, most usually by wet deposition. Vapor deposition is also used, but high vacuum conditions are needed. The resist is a photosensitive polymer, which either cross-links or is destroyed under ultra violet (UV) light. Photolithography illuminates this resist through a pattern. The pattern is designed by computer-aided design (CAD), and copied onto a mask of borosilicate. Silicon is machined by wet chemical etching (which has precision limitations, but relatively low cost), or dry etching processes, in which its surface is bombarded with ions. Alternatively, the Bosch process uses gasses heated under low pressure to a plasma state to etch the surface. A great deal of research is under way to investigate other techniques and materials for use in microsystems. Examples include the use of powder blasting and laser ablation as etching techniques, and single-crystal (SC) quartz, amorphous glass, and thermoplastic polymers as alternatives to silicon. Thick resist lithography and locally controlled photopolymerization are techniques that could be used to create microscale features in these polymers. Since recent developments in industrial, biological, and biomedical applications particularly embrace replication technology as a means to pattern multiple parts from a master pattern or even use it for stamping biomolecular features onto a surface for the design and development of novel biological assays, it is time to introduce soft-lithography among the basic microsystems technologies together with a set of nanolithographies presented in Chapter 4.
关键词： soft-lithography,silicon micromachining,thin films,microsystems,nanolithography,photolithography
更新于2025-09-09 09:28:46