Metamaterials have unlocked a number of unique optical properties for manipulating the electric and magnetic dipole resonances have drawn much attention over the past decades. It has been recognized that a metamaterial could provide a new approach to excite electromagnetic behaviors leading to potential applications in the fields of sensing, energy, and information The low-loss conformal processing integration of multi-band wide-angle electromagnetic antireflection metamaterials, functional layers and radome is a challenging research. In this paper, a high-permeability metamaterial with similar electromagnetically induced transparency (EIT) characteristics is constructed around the metal split ring, and the equivalent dielectric constant and equivalent permeability of the split ring meta-unit are analyzed based on the equivalent medium parameter inversion model. Analyze the regulation mechanism of array structure parameters on electromagnetic characteristics. The research results show that this EIT wave-transmitting material has the characteristics of wide working frequency, high transmission rate, and insensitive to electromagnetic wave incident angle and polarization direction. In view of this, a multi-band broadband electromagnetic antireflection metamaterial with a multi-layer nested coupling structure (open resonant ring-chiral spiral ring-cross symmetrical structural unit) is designed, which is continuous in different polarized electromagnetic waves from 0 degrees to 80 degrees. Large-angle oblique incidence 11GHz, 15GHz, 33Ghz three-band high transmission rate, bandwidth up to 1.3GHz, 1.02GHz and 1.678GHz.
A novel driving scheme utilizing the resonance effect of the micro-mirror is presented to reduce the drive voltage of the silicon-based MEMS (microelectromechanical systems) torsion-mirror optical switch. A mixed bias of DC (direct current) and AC (alternating current) is adopted to drive the torsion mirror. Both the numerical simulation and experiment results show that the driving voltage of the optical switch is reduced by nearly 50%, from more than 270V to 130V.
A kind of 0°-90° tilting micro-mirror with fiber holding structures monolithically, which is composed of a metal-coated polysilicon or single crystal silicon film, is fabricated by the MEMS process technology based on regular silicon wafers as well as SOl wafers using the mixed micromachining of surface and bulk silicon microelectronics. According to the scalar scattering theory, a mathematical model, which describes the effects of the surface roughness on reflectivity and scattering, is constructed to analyze the optical properties of micro-mirrors. Then the surface roughness of a series of micro-mirrors with different coated metals is measured by the AFM. The diffraction effect of etching holes and the optical power transmission through MEMS multi-layer membranes are analyzed in theory preliminarily. To characterize the dynamic response of the micro-mirrors and optimize the design of driving system, a novel reduced order model of micro-mirrors is brought forward to fulfilled the mechanics-electrics coupling simulation to verify the theoretical analysis and the experimental results easily. Based on the investigation on theory, simulation and experiments together, some ameliorated processing methods of producing the micro-mirrors are advanced to improve the total performances.
The electromechanical characteristics of a novel micro torsion-mirror actuator and the optical properties about the light scattering and reflection of its micro-mirror under the influence of mirror surface roughness are investigated experimentally and theoretically. The electrostatic yielding voltages for driving the metal-coated polysilicon or single crystal silicon micro-mirrors suspended by elastic torsion beams to tilt from 0° to 90° spontaneously are in the range of 270~290 V and the minimum holding voltages for keeping the tilting angle of the mirrors to be in 90° are found 55 V or so when the thickness of the torsion-beams is about 1 ?m. The lifetime and the estimated shortest actuating time of the micro torsion-mirror actuators can reach 108 at least and less than 2 ms, respectively. The maximum value of the surface roughness of the micro-mirrors is 69.443 nm and the distribution of the surface roughness is smooth, which is acceptable for wavelength division multiplexing applications basically. In general, the novel torsion-mirror actuators can be applied as optical switches for optical networking.
Photoelectronic characteristics of the fabricated InxGa1-xAs/AlyGa1- yAs/AlzGa1-zAs asymmetric step quantum-well middle wavelength (3 to approximately 5 micrometers ) infrared detectors are studied. The components display photovoltaic-type photocurrent response as well as the bias- controlled modulation of the peak wavelength of the main response, which is ascribed to the Stark shifts of the intersubband transitions from the local ground states to the extended first excited states in the quantum wells, at the 3 to approximately 5.3 micrometers infrared atmospheric transmission window. The blackbody detectivity (Dbb*) of the detectors reaches to about 1.0 X 1010 cm(DOT)Hz1/2/W at 77 K under bias of +/- 7 V. By expanding the electron wave function in terms of normalized plane wave basis withn the framwork of the effective-mass envelope-function theory, the linear Stark effects of the intersubband tansitions between the ground and first excited states in the asymmetric step well are calculated. The obtained results agree well with the corresponding experimental measurements.
Mid-infrared absorption in boron-doped and modulation boron- doped self-assembled Ge quantum dots grown on (001) oriented Si substrates is reported for the first time in this paper. The structures, which were grown by a solid source molecular beam epitaxy system, are composed of 20 or 30 periods of Ge dot layers and Si spacer films. The structural properties of the multilayers and some uncapped Ge dots on sample surface were tested by cross-sectional transmission electron and atomic force microscopes, respectively. Through use of Fourier transform infrared and Raman spectrometers, infrared absorption signals peaking in the mid-infrared range were observed. The absorption is strongly polarized along the growth axis of the samples. Experimental and theoretical analysis suggests that the mid-infrared response be attributed to intraband transitions in the valence band of the Ge quantum dots. This study demonstrates the application potential of these kinds of Ge/Si quantum dot multilayer structures for developing mid-infrared photodetectors.
This paper proposes and demonstrates for the first time a novel optically-coupled quantum well
infrared detector for conversion of mid or far infrared radiation into near infrared radiation. It is in
fact the monolithic integration of a GaAs/A1GaAs multiple quantum well intraband photodetector
(QWIP) and an InGaAs/GaAs quantum well resonant cavity light emitting diode (RCLED) in which
the active region is sandwiched in between a GaAs/AlAs quarter wave n-type distributed Bragg
reflector (DBR) and a GaAs/AlGal\As/A1As/AlXGal\As quarter wave p-type DBR. Experimental
results show that this new optoelectronic device exhibits an impressive external efficiency because of
Fabry-Perot resonance microcavity enhancement and mode-coupling effects in the RCLED, and that
its internal efficiency of the photon energy conversion is about unity for high quality InGaAs/GaAs
quantum wells. Since near infrared detectors normally have much higher detectivity values than those
for far infrared detectors, the proposed detector, demonstrated here by a one-dimensional array, should
be easy to scale up into large two-dimensional focal plane arrays (FPAs) and suitable for thermal
imaging application using optical interconnection directly. This new unique approach combines the
recently developed vertical-cavity surface emitting laser (VCSEL) technology with the newly
established QWIP technology both based on GaAs and related epitaxially grown alloys, such as
A1GaAs and InGaAs. Its advantage over conventional approach, usually applying an InSb or a
HgCdTe detectorarray hybrid bonded to a Si chip for multiplexing, is that it uses a mature materials
system and avoids hybrid bonding and any thermal mismatch.
A new voltage-tunable two-order GaAs/AlGaAs multistacks quantum well infrared photodetector (QWIP) has been investigated in this work. The infrared photodetector consists of GaAs/AlAs/AlGaAs double barrier quantum wells (DBQWs) and GaAs/AlGaAs square quantum wells (SQWs) with photovoltaic and photoconductive dual-mode operation in the 3 approximately 5.3 micrometers and 7.5 approximately 12 atmosphere windows. Experimental and theoretical studies have been conducted on the device physics of the intersubband transitions based on photoexcitation from ground state to different upper subbands including quasibound subband in DBQWs to virtual energy levels within the continuum in SQWs. These allow a better understanding of the optical and transport behaviors of the QWIP. The unique performance and very simple voltage-tunable switching behavior of the two-color GaAs/AlGaAs QWIP are expected to be quite competitive with HgCdTe and InSb infrared photodetectors for large area staring array imaging and two- color or multi-color detecting applications where material uniformity and simple device technology are important.
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