We demonstrate designs of dielectric-filled anti-reflection coated (ARC) two-dimensional (2D) metallic photonic
crystals (MPhCs) capable of omnidirectional, polarization insensitive, wavelength selective emission/absorption. Up to
26% improvement in hemispherically averaged emittance/absorptance below the cutoff wavelength is observed for
optimized hafnium oxide filled 2D tantalum (Ta) PhCs over the unfilled 2D Ta PhCs. The optimized designs possess
high hemispherically averaged emittance/absorptance of 0.86 at wavelengths below the cutoff wavelength and low
hemispherically averaged emittance/absorptance of 0.12 at wavelengths above the cutoff wavelength, which is extremely
promising for applications such as thermophotovoltaic energy conversion, solar absorption, and infrared spectroscopy.
A novel thin film lead zirconate titanate Pb(Zr,Ti)O3 (PZT) MEMS energy harvesting device is designed and developed
for powering autonomous wireless sensors. It is designed to harvest energy from parasitic vibrational energy sources and
convert it to electrical energy via the piezoelectric effect. The new pie-shaped design for the harvester is about a size of a
nickel and has a radical departure from previous design concepts. This design always generates positive tension on the
PZT layer and then positive charge output throughout vibration cycles. It produces mono-polarity output charge without
using any additional bridge rectifier circuitry, which will be a huge cost saving for commercial production of scaled-up
products. Contrary to the high Q cantilever designs, the new design has a low Q, doubly anchored beam design, which
provides a wide bandwidth of operational frequency. This will enable more robust power generation even if the
frequency spectrum of the source vibration varies unexpectedly. Furthermore, the beam shape is optimized to achieve
uniform strain throughout the PZT layer. To authors' knowledge, this is the first self-rectifying piezoelectric power
generator at the MEMS-scale
Scanning probe microscopy (SPM) has been an important tool to image and manipulate micro/nano scale structures. The measurement is based on the optical detection of a very small deflection of a flexible cantilever while traveling near the sample surface. However, the use of a cantilever with a sharp oxidized conical tip is quite costly, very difficult to scale up and unable to scan variable hardness surfaces, such as cell membranes in vivo. A concept of in-plane probe tip is developed. It has a carbon nanotube tip, built-in actuator and a tip deflection sensor, all assembled in the same plane. Most of all, an in-plane probe design would enable the stiffness of the probe to become tunable by using MEMS clutched springs. This allows a continuous measurement of samples with inhomogeneous surface hardness without changing the probe in the middle of a measurement.
The majority of photonic crystals developed till-date are not dynamically tunable, especially in silicon-based structures. Dynamic tunability is required not only for reconfiguration of the optical characteristics based on user-demand, but also for compensation against external disturbances and relaxation of tight device fabrication tolerances. Recent developments in photonic crystals have suggested interesting possibilities for static small-strain modulations to affect the optical characteristics [1-3], including a proposal for dynamic strain-tunability [4]. Here we report the theoretical analysis, device fabrication, and experimental measurements of tunable silicon photonic band gap microcavities in optical waveguides, through direct application of dynamic strain to the periodic structures [5]. The device concept consists of embedding the microcavity waveguide [6] on a deformable SiO2 membrane. The membrane is strained through integrated thin-film piezoelectric microactuators. We show a 1.54 nm shift in cavity resonances at 1.56 um wavelengths for an applied piezoelectric strain of 0.04%. This is in excellent agreement with our modeling, predicted through first-order semi-analytical perturbation theory [7] and finite-difference time-domain calculations. The measured microcavity transmission shows resonances between 1.55 to 1.57 um, with Q factors ranging from 159 to 280. For operation at infrared wavelengths, we integrate X-ray and electron-beam lithography (for critical 100 nm feature sizes) with thin-film piezoelectric surface micromachining. This level of integration permits realizable silicon-based photonic chip devices, such as high-density optical filters and spontaneous-emission enhancement devices with tunable configurations.
In the present paper we report a high-fill factor uncooled IR micro-bolometer array; and, more particularly, a three- level IR bolometer including an almost 92 percent fill factor absorber and a separately-designed bridge structure for the electro-thermal isolation of thermal sensor; and a method for the silicon-based fabrication. The present 256 X 256 bolometer array comprises a CMOS readout circuitry, a bridge level, a pari of posts, and an absorption level. The fabrication of the presented bolometer feature that it uses double sacrificial layers so as to separate the absorber level from the bridge structure, electrical and thermal path between the absorber and substrate. Also, we chose a titanium thin-film as a bolometer material which is patterned to make a connection between the substrate contact and the post. The absorber level is compared of titanium metal film sandwiched between PECVD deposited silicon dioxide layers to preserve thermal isolation of a bolometer absorber and release the inertial stresses. Additional contact is formed to connect the metal thin-film to the serpentine resistive pattern on the absorbing membrane defined on the top of the second sacrificial layer. From the structural design, we can obtain a good thermal isolation without reducing IR absorbing area.
The thin-film micromirror array (TMA) is a new reflective type spatial light modulator fabricated with the optical microelectromechanical system (MEMS) technology. Micromachined thin-film piezoelectric actuators are used to control the tilt angle of each micromirror, which simply defines the gray scale of the matching screen pixel when it reflects the light for the lamp. The hidden actuator design with the two-sacrificial layer process provides the highest fill factor and flat enough micromirrors resulting the system optical efficiency of 22 percent, which is the highest efficiency among all the reflective and transmissive light modulators in the world at the present time. A working projector prototype of 5,400 true ANSI lumen is realized with three TMA modules and a 1 kW Xenon lamp. TMA projector prototype is brighter than any competing technology projectors in the world at the same lamp power, at least three times or more. The simplicity of the underlying principle and the highest optical efficiency of TMA enables high-brightness and cost competitive projection displays which has been impossible in the past. At the same cost, more brightness can be provided for the high-end large venue projectors. At the same brightness, lower cost products can be provided as desktop projectors for no-more-darkroom digital presentation and affordably priced HDTVs.
The Thin-Film Actuated Mirror Array (TFAMA) is a new reflective type spatial light modulator developed by using the microelectromechanical system technology. The micromachined thin-film piezoelectric actuators are used to control the tilting angle of micromirrors. This paper describes the principle, design, fabrication and the performance of the TFAMA module for high-brightness projection displays. Maximizing the optical performance in terms of the fill factor and the mirror flatness is the main issue of this paper. A hidden actuator design with the two- spacer process provides the highest optical efficiency among the reflection light modulators at the present time. A working projector prototype of 5,000 ANSI lumen is realized with three TFAMA modules with a 1 kW Xenon lamp.
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