1,720,986 research outputs found
Development of a spring-less RF MEMS switch
No full textThis thesis reports on the development of a novel 77GHz low loss MEMS switch with a mechanically unrestrained armature, over a RF transmitting coplanar waveguide. Electrostatic actuation is used during the switching operation. The attractive force from the electrostatic field is generated by a pair of the actuation electrodes on both sides of the armature, depending on the direction of the movement.A Simulink model is employed to simulate the mechanical response of the switching armature. Different damping models are deployed into the Simulink model, yielding different actuation time for the switch. This model is also employed to design the dimensions of the MEMS switch in the mechanical domain. The effect of Van der Waal force between the dielectric layer and designed armature is also discussed. An electrical model of the RF MEMS switch is represented using lumped RLC components and characteristic impedance of the transmission line. The relationship between the electrical model and the scattering parameters is explained with the effects of the individual component on the S-Parameter being studied. Electromagnetic simulations have shown that the designed switch has potential of being employed in automotive collision avoidance system or in Doppler radar application. The proposed design is also capable of operating in lower frequency bands after some tuning, through different armature design.A clean room fabrication flow is described as part of the development process of this novel switch. This is based on two Pyrex wafers and a SOI wafer utilising a double bonding and DRIE processes. RF characterisation of the coplanar waveguide and the micron-scale prototype at DOWN state is also discussed.An alternative rapid prototyping technique based on high-frequency PCB and microscopic glass slide has been developed. This process is cheaper and requires shorter turnover time as compared to the clean room prototype. Electromechanical and SParameter measurements of the rapid prototype device are reported. These results are verified through simulations. The minimum actuation voltage of the prototype is 93V, with a rise and fall time of 165ms and 180ms. Switching is possible for frequencies from 2.8-5.5GHz and 6.6-10GHz, with the optimum frequency at 3.3GHz and 6.9GHz. The insertion loss and isolation of the prototype are -26.5dB and -38.5dB at 6.9GHz respectively. Although this is far from the state of the art for RF MEMS switches, it nevertheless proves the fundamental concept of a MEMS switch with an unrestrained armature by a prototype realised using a rapid prototype methodology
RAM-adaptive parallel generating and minimizing the layout file of wafer-scale metalens
No full textMetalens have emerged as an attractive device for astronomy observation because of their submillimeter thickness and lightweight as well as their powerful manipulating ability of light field’s amplitude, phase, and polarisation. However, the aperture size of a metalens is restricted within a millimetre scale by the layout file sizes. Here, we introduce the OASIS format to effectively reduce the layout file sizes and propose a RAM-adaptive parallel approach for accelerating the layout file generation of large-aperture metalens. By designing a metalens working in the wavelength of 1550nm, we demonstrate that the layout file sizes can be reduced by 94% via using OASIS format than conventional GDS format. Based on a multiple-core computer, the OASIS layout file of a 5cm-diameter metalens can be generated within 10 hours
Digitally tunable metasurfaces based on phase-change material
No full textA key recent advance in nanophotonics field has been the emergence of tunable, switchable and reconfigurable metasurfaces offering “optical properties on demand”. Various approaches have been developed to realize optical components made from metadevices reconfigurable by mechanical, electrical, or optical means. In general, however, most of the existing reconfigurable metasurfaces tune the properties over the entire device homogeneously when stimulated. In this work, we pioneered single-meta-molecule addressable digitally reconfigurable metadevices using the emerging paradigms of tunable metasurfaces - functional matter structured on the sub-wavelength scale, and by engaging new ideas of phase-change material integrated with nanostructures for dynamic light control. In our design, low loss dielectric nanostructures (amorphous Si nanorods) are patterned on top of phase-change foundation structures to form the hybrid meta-molecule. As for the phase-change medium, we use the chalcogenide glasses (e.g. germanium-antimony-telluride), which have pronounced contrast of dielectric properties observed between two phases. The laser-induced submicron-sized phase-change footprint allows us to address single meta-molecules individually. The reconfiguration of meta-molecules will be accomplished by re-amorphization of the phase-change material with a high-energy single optical pulse. The preliminary simulation results demonstrated the reconfigurable metasurfaces for phase and resonance frequency modulation of light based on the innovative platform of digitally and individually reconfigurable meta-molecules for applications in active beam shape and hologram displa
Nanofabrication of monolithically integrated multilayer metasurfaces via fully CMOS-compatible processes
No full textWe have developed a novel metasurface stacking methodology that is fully compatible with standard Complementary Metal-Oxide-Semiconductor（CMOS） processes, advancing the mass production and commercialization of metasurface technologies
Controlled generation and imaging application of Poincaré sphere beams via all-dielectric metasurface
No full textSingle-layer all-dielectric metasurface has attracted increasing attention in the generation and applications of higher-order and hybrid-order Poincaré sphere (HOPS and HyOPS) beams because of its powerful ability of manipulating the amplitude, phase, and polarization. However, there is not a unified theoretical frame to design all-dielectric metasurfaces for controlled generating unfocused and focused HOPS and HyOPS beams. Moreover, the controlled generation of focused HyOPS beams has not been demonstrated in imaging applications. Here, we will present a unified design method of the all-dielectric metasurfaces so that arbitrary vector vortex beams on a HOPS or HyOPS can be controlled generated and highly focused with a numerical aperture (NA). Then, we will demonstrate some metasurface samples which can generate and tightly focus the 5th-order HOPS beams and 0-1-order HyOPS beams with a NA of 0.89. Finally, a high-magnification (58X) and subwavelength-resolution (0.7λ) microscope will be demonstrated by utilizing the 0-1-order HyOPS beams sample as an objective lens. Benefiting from the tunability of the topological charge carried by the focal field, the imaging mode of the microscope can be tune from bright field mode to edge-enhancement mode
Near-infrared metalens empowered dual-mode high resolution and large FOV microscope
No full textThe spiral phase contrast microscope can clearly distinguish the morphological information of the low contrast objects (i.e., biological samples) owing to the isotropic edge-enhancement effect, while the bright field microscope can image the overall morphology of amplitude objects. However, the imaging resolution, magnification, and field of view of conventional spiral phase contrast microscopes based on 4f filtering configuration are limited by the system's complexity. Here, compact dual-mode microscopes working at near-infrared using the engineered metalens are reported, which can be tuned between the spiral phase contrast imaging and bright field imaging by polarization control. The metalens combine the high-resolution objective lens and polarization-controlled phase filter into a single-layer nanofins array. Two infinity-corrected microscope systems are demonstrated to achieve subwavelength resolution (0.7λ), large magnification (58X), and large field of view (600 × 800 µm). Unstained onion epidermal is imaged by the microscope to show the dual-mode imaging ability for the biological sample. Finally, a singlet dual-mode microscope system is demonstrated to show the edge-detection application for industrial standards. These results can open new opportunities in applications of biological imaging, industrial machine vision, and semiconductor inspection.</p
Dataset in support of the paper: Near-infrared metalens empowered dual-mode high resolution and large FOV microscope
No full textThis dataset provides the initial data for the figures 3d and 4d in the paper (Title: Near-infrared metalens empowered dual-mode high resolution and large FOV microscope). To be published in Advanced Optical Materials</span
Manipulation of higher-order Poincaré sphere beams beyond the diffraction limit using single-layer metasurface
No full textControl and generation of arbitrary higher-order Poincaré sphere (HOPS) beams have attracted intensive interest because of the potential of extreme optical manipulation using HOPS beams. Here, we experimentally demonstrate the control of focused HOPS beams with multi-foci of 22% smaller than the diffraction limit via a single-layer metasurface. Since the optical tweezer based on a highly focused laser beam was invented in 1970 and awarded the Nobel Prize in 2018, it has been explored for manipulating microscale and nanoscale particles in both over-damped and under-damped regimes, which makes it possible to move biological and chemical molecules via a contactless way, to study light-matter interaction, and to realize a macro quantum system. The on-chip generation and manipulation of HOPS beams would effectively extend the dimension (2D to 3D) and complexity (single particle to multiple particles) of optical manipulation. Here, we show that a single-layer dielectric metasurface can be used for simultaneously manipulating and highly focusing the HOPS beam via manipulating the incident laser beam’s polarization. A metasurface with a diameter of 1.2mm and a numerical aperture of 0.9 is fabricated following a CMOS-compatible process. Then, it is measured in a custom-built microscope system with a camera working at 1550nm
Arbitrary hybrid and higher-order Poincaré sphere beams generation by metasurfaces via a unified design framework
No full textThe unique phase profile and polarisation distribution of the vector vortex beam have been a subject of increasing interest in classical and quantum optics. The development of higher-order Poincaré sphere and hybrid-order Poincaré sphere has provided a systematic description of vector vortex beams. However, the generation of arbitrary vector vortex beams on a higher-order and a hybrid-order Poincaré sphere via a metasurface lacks a unified design framework, despite numerous reported approaches. This paper presents a novel, unified general design framework incorporating all design parameters (e.g., focal length, orders) of arbitrary higher-order Poincaré sphere and hybrid-order Poincaré sphere beams into a single equation. In proof-of-concept experiments, we experimentally demonstrated four metasurfaces to generate arbitrary beams on the 5th-order higher-order Poincaré sphere (non-focused and tightly-focused, NA 0.89), 0-2 order and 0-1 order hybrid-order Poincaré sphere. We showed higher-order Poincaré sphere beams' propagation and focusing properties, the super-resolution focusing characteristics of the 1st-order cylindrical vector vortex beams, and the different focusing properties of integer-order and fractional-order cylindrical vector vortex beams. The simplicity and feasibility of the proposed design framework make it a potential catalyst for arbitrary vector vortex beams using metasurfaces in applications of optical imaging, communication, and optical trapping
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