High Angle Sensitivity Research Articles

High-accuracy direction measurement and high-resolution computational spectral reconstruction based on photonic crystal array

Portable and wearable miniaturized spectrometers play a crucial role in various fields. In this paper, we present a method for simultaneously realizing high-accuracy direction measurement and high-resolution computational spectral reconstruction based on the angle sensitivity of conventional photonic crystals (PCs), wherein an optical filter array is composed of multiple one-dimensional PCs. The high-angle sensitivity of PCs results in angle-dependent optical spectra. When these spectra with different angles are used to reconstruct the target spectra in an unknown direction and the interval between adjacent angles is sufficiently small, the accurate direction of the target can be automatically identified. Moreover, the computational spectra still have high resolution over a wide range of incidences. The computational spectra under arbitrary polarizations can also be recognized based on the polarization dependence of the PCs at an oblique incidence. Our research results are significant for engineering a new miniaturized comprehensive computational spectrometer with target-direction perception and omnidirectional spectral reconstruction abilities.

Observation of giant room-temperature anisotropic magnetoresistance in the topological insulator β-Ag2Te

Achieving room-temperature high anisotropic magnetoresistance ratios is highly desirable for magnetic sensors with scaled supply voltages and high sensitivities. However, the ratios in heterojunction-free thin films are currently limited to only a few percent at room temperature. Here, we observe a high anisotropic magnetoresistance ratio of −39% and a giant planar Hall effect (520 μΩ⋅cm) at room temperature under 9 T in β-Ag2Te crystals grown by chemical vapor deposition. We propose a theoretical model of anisotropic scattering — induced by a Dirac cone tilt and modulated by intrinsic properties of effective mass and sound velocity — as a possible origin. Moreover, small-size angle sensors with a Wheatstone bridge configuration were fabricated using the synthesized β-Ag2Te crystals. The sensors exhibited high output response (240 mV/V), high angle sensitivity (4.2 mV/V/°) and small angle error (<1°). Our work translates the developments in topological insulators to a broader impact on practical applications such as high-field magnetic and angle sensors.

Absolute wavelength scanning interferometry for measuring the thickness of optical elements.

A technique for measurement of the thickness of optical elements using absolute wavelength scanning interferometry is presented in this paper. To achieve high-grade optical components and systems, the thickness of both planar and non-planar optical components must be measured with an accuracy of a few micrometers. The proposed technique is based on the Fizeau interferometer and interconnects data from three different tunable laser diodes yielding a long effective wavelength range and thus low measurement uncertainty. The uncertainty of the central thickness measurement ranges from hundreds of nanometers to a few microns. The method allows to measure the thickness of both flat optical elements as well as lenses with curved surfaces. Moreover, the areal information provided by the interferometry and its high angle sensitivity help to quickly and precisely align the measured component and reduce misalignment errors. The results of thickness measurements have been validated and cross-tested with other techniques. In addition to the thickness, the technique provides some additional information (wedge, surface form error) in the case of flat samples and can be easily and quickly modified (mounting of a Fizeau transmission sphere) to measure other essential parameters of optical elements. Thus, this one approach can replace many single-purpose measuring devices while maintaining high accuracy.

Narrowband diffuse thermal emitter based on surface phonon polaritons

Abstract Thermal emission engineering with ability to realize spectral and spatial selection has attracted great attention in recent years. Nanophotonic control of thermal radiation has demonstrated narrowband thermal emitter but with high angle-sensitivity and diffuse thermal emitter but with low quality factor (Q). Here, we demonstrate a simultaneous narrowband, diffuse thermal emitter consisting of 80 nm (&lt;λ/100) thick Ge nanostructures on a silicon carbide (SiC) phononic material. Based on surface phonon polaritons, a spectral coherent emission with a high Q factor of 101 is achieved at ∼10.9 μm wavelength in experiment. Furthermore, this phonon-mediated nanostructure provides spatial control with strong diffuse thermal emission with a full angle at half maximum of 70°. Additionally, the emission wavelength and intensity are tuned by replacing Ge with phase change materials (Ge2Sb2Te5 and In3SbTe2). The designed narrowband diffuse thermal emitter offers new perspectives for the engineering of emission and paves the way for infrared applications, including thermal sources, radiative cooling, infrared sensing, and thermal photovoltaics.

Conductive Porous MXene for Bionic, Wearable, and Precise Gesture Motion Sensors.

Reliable, wide range, and highly sensitive joint movement monitoring is essential for training activities, human behavior analysis, and human-machine interfaces. Yet, most current motion sensors work on the nano/microcracks induced by the tensile deformation on the convex surface of joints during joint movements, which cannot satisfy requirements of ultrawide detectable angle range, high angle sensitivity, conformability, and consistence under cyclic movements. In nature, scorpions sense small vibrations by allowing for compression strain conversion from external mechanical vibrations through crack-shaped slit sensilla. Here, we demonstrated that ultraconformal sensors based on controlled slit structures, inspired by the geometry of a scorpion's slit sensilla, exhibit high sensitivity (0.45%deg−1), ultralow angle detection threshold (~15°), fast response/relaxation times (115/72 ms), wide range (15° ~120°), and durability (over 1000 cycles). Also, a user-friendly, hybrid sign language system has been developed to realize Chinese and American sign language recognition and feedback through video and speech broadcasts, making these conformal motion sensors promising candidates for joint movement monitoring in wearable electronics and robotics technology.

High angle sensitivity of carbon nanotubes films reinforced composites to electromagnetic interference shielding

Electromagnetic interference (EMI) shielding composites with high angle sensitivity were fabricated by the introduction of highly aligned carbon nanotubes (CNTs) films into an epoxy matrix as reinforcement and conducting framework. Anisotropic structure was obtained which led to high angle sensitivity in electrical conductivity, mechanical performance and EMI shielding property. Conductivity can change from 307.12 S m−1 in in-plane direction to non-conductive in out-of-plane direction, EMI effectiveness can be tuned from almost transparent to microwaves to 33.1 dB with incident wave angle changing from 0° to 90°. Moreover, mechanical performance was enhanced as CNTs films played main role in bearing load.

Temperature‐independent fiber bragg grating tilt sensor

AbstractA novel fiber Bragg grating (FBG) tilt sensor is proposed to detect the magnitude and the direction of a two‐dimensional inclination by using four FBGs. High angle sensitivity and measurement resolution have been achieved, and the temperature effect has been eliminated completely without additional temperature compensation schemes. Experimental results verified the feasibility of the proposed idea. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2250–2252, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25425