Terahertz wave properties of alumina microphotonic crystals with a diamond structure

2008 ◽  
Vol 23 (4) ◽  
pp. 1036-1041 ◽  
Author(s):  
Hideaki Kanaoka ◽  
Soshu Kirihara ◽  
Yoshinari Miyamoto
Keyword(s):  
Photonic Band Gap ◽  
Three Dimensional ◽  
Expansion Method ◽  
Linear Shrinkage ◽  
Terahertz Wave ◽  
Diamond Structure ◽  
Terahertz Time Domain Spectroscopy ◽  
3D Cad ◽  
Unit Cells ◽  
Wave Properties

Fabrication and terahertz wave properties of alumina microphotonic crystals with a diamond structure were investigated. The three-dimensional diamond structure was designed on a computer using 3D-CAD software. The designed lattice constant was 500 μm. The structure consisted of 8 × 8 × 4 unit cells. Acrylic diamond structures with an alumina dispersion of 40 vol% were formed by using microstereolithography. Fabricated precursors were dewaxed at 600 °C and sintered at 1500 °C. The linear shrinkage ratio was about 25%. The relative density reached 97.5%. The electromagnetic wave properties were measured by terahertz time-domain spectroscopy. A complete photonic band gap was observed at the frequency range from 0.40 THz to 0.47 THz, and showed good agreement with the simulation results calculated by the plane wave expansion method. Moreover, localized modes were obtained at the frequencies 0.42 THz and 0.46 THz by introducing an air defect in the diamond structure. They corresponded to the simulation by the transmission line modeling method.

Terahertz Wave Properties of Ceramic Photonic Crystals with Graded Structure Fabricated by Using Micro-Stereolithography

2009 ◽  
Vol 631-632 ◽  
pp. 299-304 ◽  
Author(s):  
Soshu Kirihara ◽  
Toshiki Niki ◽  
Masaru Kaneko
Keyword(s):  
Electromagnetic Wave ◽  
Photonic Crystals ◽  
Photonic Band Gap ◽  
Three Dimensional ◽  
Expansion Method ◽  
Terahertz Wave ◽  
Diamond Structure ◽  
Terahertz Time Domain Spectroscopy ◽  
3D Cad ◽  
Wave Properties

Fabrication and terahertz wave properties of alumina micro photonic crystals with a diamond structure were investigated. The three-dimensional diamond structure was designed on a computer using 3D-CAD software. Acrylic diamond structures with alumina particles dispersion were formed by using micro-stereolithography. Fabricated precursors were dewaxed and sintered in the air. The electromagnetic wave properties were measured by terahertz time-domain spectroscopy. A complete photonic band gap was observed at the frequency range from 0.40 to 0.47 THz, and showed good agreement with the simulation results calculated by the plane wave expansion method. Moreover, a localized mode was obtained by introducing a plane defect between twinned diamond structures. The one-way transmission of the electromagnetic wave was realized by using this twinned photonic crystal with the graded diamond structure. They corresponded to the simulation by the transmission line modeling (TLM) method.

Electromagnetic properties of photonic crystals with diamond structure containing defects

2003 ◽  
Vol 18 (9) ◽  
pp. 2214-2220 ◽  
Author(s):  
Shingo Kanehira ◽  
Soshu Kirihara ◽  
Yoshinari Miyamoto ◽  
Kazuaki Sakoda ◽  
Mitsuo Wada Takeda
Keyword(s):  
Photonic Crystals ◽  
Band Gap ◽  
Photonic Band Gap ◽  
Three Dimensional ◽  
Expansion Method ◽  
Electromagnetic Properties ◽  
Diamond Structure ◽  
Multiple Reflections ◽  
Air Cavity ◽  
Photonic Band

Three-dimensional photonic crystals with a diamond structure, which are composed of the TiO2-based ceramic particles dispersed in an epoxy lattice, were fabricated by stereolithography. The diamond structure showed a photonic band gap in the 14.3–17.0 GHz range along the Γ-K 〈110〉 direction, which is close to the band calculation using the plain wave expansion method. Two types of lattice defects—air cavity and dielectric cavity—were introduced into the diamond structure by removing a unit cell of diamond structure or inserting a block of the lattice medium into the air cavity. The transmission of millimeter waves affected by multiple reflections at the defects was measured in the photonic band gap. Resonant frequencies in the defects were calculated and compared with the measurement results.

Stereolithographic Additive Manufacturing of Diamond Photonic Crystal Composed of Titania and Alumina Micro Lattices

2015 ◽  
Vol 2015 (CICMT) ◽  
pp. 000314-000321
Author(s):  
Soshu Kirihara
Keyword(s):  
Additive Manufacturing ◽  
Band Gap ◽  
Photonic Band Gap ◽  
Three Dimensional ◽  
Terahertz Wave ◽  
Diamond Lattice ◽  
Lattice Structures ◽  
W Band ◽  
Tlm Method ◽  
Localized Mode

Three dimensional micro photonic crystals with a diamond structure made of a dense titania and alumina were fabricated successfully by using stereolithographic additive manufacturing. Photonic band gap properties were investigated in gigahertz and terahertz wave frequency ranges. Acrylic diamond lattice structures with nanometer sized particles of titania and alumina dispersion at 40 vol. % were fabricated by the stereolithography. The forming accuracy was 10 μm. After dewaxing and sintering process, the titania and alumina diamond lattice structures were obtained. The relative density reached above 98 %. Electromagnetic wave transmittances were measured by using a W-band millimeter waveguide connected with a network analyzer and a terahertz wave time domain spectroscopy. In the transmission spectra for the Γ-X <100> direction, a forbidden band was observed at 90 – 110 GHz and 0.4 – 0.6 THz. The band gap frequencies well agreed with calculated results by plane wave expansion (PWE) method. Additionally, simulated results by transmission line modeling (TLM) method indicated that a localized mode can be obtained by introducing a plane defect between twinned diamond lattice structures.

Crystal Structure Analysis of Cu-Zr Alloys by Convergent Beam Diffraction

1981 ◽  
Vol 39 ◽  
pp. 354-355
Author(s):  
A. F. Marshall ◽  
J. W. Steeds ◽  
D. Bouchet ◽  
S. L. Shinde ◽  
R. G. Walmsley
Keyword(s):  
Crystal Structure ◽  
Point Group ◽  
Intermetallic Phase ◽  
Three Dimensional ◽  
Crystal Structure Analysis ◽  
Ion Milling ◽  
Composition And Structure ◽  
Unit Cells ◽  
Sputter Deposited ◽  
Convergent Beam

Convergent beam electron diffraction is a powerful technique for determining the crystal structure of a material in TEM. In this paper we have applied it to the study of the intermetallic phases in the Cu-rich end of the Cu-Zr system. These phases are highly ordered. Their composition and structure has been previously studied by microprobe and x-ray diffraction with sometimes conflicting results.The crystalline phases were obtained by annealing amorphous sputter-deposited Cu-Zr. Specimens were thinned for TEM by ion milling and observed in a Philips EM 400. Due to the large unit cells involved, a small convergence angle of diffraction was used; however, the three-dimensional lattice and symmetry information of convergent beam microdiffraction patterns is still present. The results are as follows:1) 21 at% Zr in Cu: annealed at 500°C for 5 hours. An intermetallic phase, Cu3.6Zr (21.7% Zr), space group P6/m has been proposed near this composition (2). The major phase of our annealed material was hexagonal with a point group determined as 6/m.

scholarly journals Automatized Evaluation of Students’ CAD Models

2021 ◽  
Vol 11 (4) ◽  
pp. 145
Author(s):  
Nenad Bojcetic ◽  
Filip Valjak ◽  
Dragan Zezelj ◽  
Tomislav Martinec
Keyword(s):  
Computer Aided Design ◽  
Three Dimensional ◽  
Computer Application ◽  
Test Cases ◽  
Cad Model ◽  
Computer Solution ◽  
3D Cad ◽  
Computer Aided ◽  
Cad Models ◽  
Aided Design

The article describes an attempt to address the automatized evaluation of student three-dimensional (3D) computer-aided design (CAD) models. The driving idea was conceptualized under the restraints of the COVID pandemic, driven by the problem of evaluating a large number of student 3D CAD models. The described computer solution can be implemented using any CAD computer application that supports customization. Test cases showed that the proposed solution was valid and could be used to evaluate many students’ 3D CAD models. The computer solution can also be used to help students to better understand how to create a 3D CAD model, thereby complying with the requirements of particular teachers.

scholarly journals Three-dimensional Maxwellian extended Newtonian gravity and flat limit

2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
Patrick Concha ◽  
Lucrezia Ravera ◽  
Evelyn Rodríguez ◽  
Gustavo Rubio
Keyword(s):  
Cosmological Constant ◽  
Three Dimensional ◽  
Expansion Method ◽  
Gravity Models ◽  
Newtonian Gravity ◽  
Newtonian Theory ◽  
Relativistic Limit ◽  
Expansion Procedure ◽  
Three Space ◽  
Chern Simons

Abstract In the present work we find novel Newtonian gravity models in three space-time dimensions. We first present a Maxwellian version of the extended Newtonian gravity, which is obtained as the non-relativistic limit of a particular U(1)-enlargement of an enhanced Maxwell Chern-Simons gravity. We show that the extended Newtonian gravity appears as a particular sub-case. Then, the introduction of a cosmological constant to the Maxwellian extended Newtonian theory is also explored. To this purpose, we consider the non-relativistic limit of an enlarged symmetry. An alternative method to obtain our results is presented by applying the semigroup expansion method to the enhanced Nappi-Witten algebra. The advantages of considering the Lie algebra expansion procedure is also discussed.

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