Emission of terahertz radiations from fractal antennas

This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in APPLIED PHYSICS LETTERS. 95(22):221111 (2009) and may be found at https://doi.org/10.1063/1.3271181 .We investigate the emission of terahertz radiation from a photoconductive fractal antenna fabricated on a semi-insulating gallium arsenide substrate. Owing to the self-similarity of fractal structures, our fractal antenna shows a multiband emission of terahertz radiation. The emission intensity at peak frequency is about twice that from a bow-tie antenna. We also investigate the mechanism of the multiband emission by using the finite-difference time-domain calculation.ArticleAPPLIED PHYSICS LETTERS. 95(22):221111 (2009)journal articl

Emission of terahertz radiations from fractal antennas

This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in APPLIED PHYSICS LETTERS. 95(22):221111 (2009) and may be found at https://doi.org/10.1063/1.3271181 .We investigate the emission of terahertz radiation from a photoconductive fractal antenna fabricated on a semi-insulating gallium arsenide substrate. Owing to the self-similarity of fractal structures, our fractal antenna shows a multiband emission of terahertz radiation. The emission intensity at peak frequency is about twice that from a bow-tie antenna. We also investigate the mechanism of the multiband emission by using the finite-difference time-domain calculation.ArticleAPPLIED PHYSICS LETTERS. 95(22):221111 (2009)journal articl

Past Achievements and Future Challenges in 3D Photonic Metamaterials

Photonic metamaterials are man-made structures composed of tailored micro- or nanostructured metallo-dielectric sub-wavelength building blocks that are densely packed into an effective material. This deceptively simple, yet powerful, truly revolutionary concept allows for achieving novel, unusual, and sometimes even unheard-of optical properties, such as magnetism at optical frequencies, negative refractive indices, large positive refractive indices, zero reflection via impedance matching, perfect absorption, giant circular dichroism, or enhanced nonlinear optical properties. Possible applications of metamaterials comprise ultrahigh-resolution imaging systems, compact polarization optics, and cloaking devices. This review describes the experimental progress recently made fabricating three-dimensional metamaterial structures and discusses some remaining future challenges

1歳から12歳の幼児および児童におけるボールキック能力の発達過程

The purpose of this study was to determine the developmental process of the ball kicking ability in children. One hundreds and ninety-five boys and one hundreds and seventy-five girls, aged 1 to 12, participated in this study as subjects. The subjects performed two tests, the stationary ball kicking and the rolling-ball kicking tests. The movements of the subjects and the ball were filmed by using a 16mm cine-camera. The kicking ball speed, the swinging speed of the kicking foot, the distance from the support foot to the ball, and the contact places of the foot and the ball at the instant of the kicking were measured. Both of the ball speed and the swinging speed of the kicking foot was linearly augmented with increasing the age in boys and girls. Linear relationship between the ball speed and the swinging speed of the kicking foot was obtained in both boys and girls. The higher ball speed and swinging speed of the kicking foot was observed in boys than in girls over 1 to 12 years. In both boys and girls, the ball speed and the swinging speed was lower in the rolling-ball kicking than in the placeball kicking. The rate of ball speed to kicking foot swinging speed was augmented with increasing age

Broadband Linear-Dichroic Photodetector in a Black Phosphorus Vertical p-n Junction

The ability to detect light over a broad spectral range is central for practical optoelectronic applications, and has been successfully demonstrated with photodetectors of two-dimensional layered crystals such as graphene and MoS2. However, polarization sensitivity within such a photodetector remains elusive. Here we demonstrate a linear-dichroic broadband photodetector with layered black phosphorus transistors, using the strong intrinsic linear dichroism arising from the in-plane optical anisotropy with respect to the atom-buckled direction, which is polarization sensitive over a broad bandwidth from 400 nm to 3750 nm. Especially, a perpendicular build-in electric field induced by gating in black phosphorus transistors can spatially separate the photo-generated electrons and holes in the channel, effectively reducing their recombination rate, and thus enhancing the efficiency and performance for linear dichroism photodetection. This provides new functionality using anisotropic layered black phosphorus, thereby enabling novel optical and optoelectronic device applications.Comment: 18 pages, 5 figures in Nature Nanotechnology 201

Terahertz sensing method for protein detection using a thin metallic mesh

A label-free biological sensor, which is based on the resonant transmission phenomenon of a thin metallic mesh, is proposed in the terahertz wave region. By using this sensor, we demonstrate the highly sensitive detection of small amounts of protein horseradish peroxidase. For quantitative investigation of the sensitivity of our sensor, horseradish peroxidase was printed on the metallic mesh surface by using a commercial available printer. A distinct shift of the transmission dip frequency is observed for 500 pg/mm2 (11 fmol) of horseradish peroxidase printed on the metallic mesh, indicating the significantly high sensitivity of our sensor