arXiv subjects

Chikara Sakurai

Publications and source records attributed to Chikara Sakurai.

5 recordsLinked to original sources

arXiv2019

Special polarization characteristic features of a three-dimensional terahertz photonic crystal semi-quantitatively evaluated by using a FEM

A previous work [1] experimentally confirmed that the special polarization characteristic features of a three-dimensional terahertz (THz) photonic crystal with a silicon inverse diamond structure whose lattice point shape was vacant regular octahedrons, did not apply to general physical and optical basic rules in appearance. One of the basic rules is that, according to Maxwell's equations, the electric-field direction of the reflected wave rotates by 180 degrees from that of the incident wave in the case of complete reflection (Bragg reflection) and normal incidence. It is said that three-dimensional photonic crystals have no polarization anisotropy within photonic band gap (stop gap, stop band) of high symmetry points in normal incidence. Experimental results, however, confirmed that the polarization orientation of a reflected wave was rotated by 90 degrees for that of an incident wave at a frequency within photonic band gap. In this work, measured reflected spectra [1] were semi-quantitatively evaluated by being compared with reflection ones by using a FEM (finite element method). These results suggest that measured polarization anisotropy does not apply to Maxwell's equations in appearance but applies to these equations in essential as expected.

physics.optics↗

arXiv2019

Special polarization characteristic features of a three dimensional terahertz photonic crystal not apparently apply to physical and optical basic rules

A silicon inverse diamond structure whose lattice point shape was vacant regular octahedrons had a complete photonic band gap at around 0.4 THz and X point's photonic band gap (0.36 THz to 0.44 THz) by plane wave expansion method. It is said that three-dimensional photonic crystals have no polarization anisotropy in photonic band gap (stop gap, stop band) of high symmetry points in normal incidence. Experimental results, however, confirmed that the polarization orientation (electric-field direction) of a reflected wave was different from that of an incident wave whose direction was [001]. The polarization orientation of the incident wave was parallel to the surface (001) of the photonic crystal, and it was set in the orientation defined as $θ$ $^\circ$ (degree). The angle, $θ$ was 0$^\circ$ to 90$^\circ$ per 15$^\circ$. A sample was rotated in plane (001) instead of the incident wave, relatively. The polarization orientation of the reflected wave was parallel to that of the incident wave for $θ$ = 0$^\circ$ and 90$^\circ$, in contrast, the former was perpendicular to the latter for $θ$ = 45$^\circ$ in the vicinity of 0.42 THz. For an intermediate $θ$, the former was an intermediate orientation. As far as the photonic crystal in this work is concerned, these phenomena do not apply to physical and optical basic rules in appearance.

physics.optics↗

arXiv2019

Special polarization characteristic features of a three-dimensional terahertz photonic crystal with a silicon inverse diamond structure

The band structure of an Si inverse diamond structure whose lattice point shape was vacant regular octahedrons, was calculated using plane wave expansion method. A complete photonic band gap was theoretically confirmed at around 0.4 THz. It is said that three-dimensional photonic crystals have no polarization anisotropy in photonic band gap (stop gap, stop band) of high symmetry points in normal incidence. However, it was experimentally confirmed that the polarization orientation of a reflected wave was different from that of an incident wave, [I$(X,Y)$], where $(X,Y)$ is the coordinate system fixed in the photonic crystal. It was studied on a plane (001) at around X point's photonic band gap (0.36 $-$ 0.44 THz) for incident wave direction [001] by rotating a sample in the plane (001), relatively. The polarization orientation of the reflected wave was parallel to that of the incident wave when that of the incident wave was I(1, 1) or I(1, $-$1). In contrast, the former was perpendicular to the latter when that of the incident wave was I(1, 0) or I(0, $-$1) at around 0.38 THz. As far as the photonic crystal in this work is concerned, method of resolution and synthesis of the incident polarization vector is not able to apply to the analyses of rotation of the measured reflected spectra in appearance.

physics.optics↗

arXiv2019

Special polarization characteristic features of a three-dimensional terahertz photonic crystal quantitatively evaluated by phase-differences with a FEM

A previous work, ref. 2 experimentally confirmed that measured special polarization characteristic features of a three-dimensional terahertz (THz) photonic-crystal did not apparently apply to general physical- and optical- basic rules. It is said that three-dimensional (3D) photonic crystals (PC) have no polarization anisotropy within photonic band gap (PBG, stop gap, stop band) of high symmetry points in normal incidence. None the less because two directions at right angles to each other on the plane (001) are constitutionally and optically identical in appearance, the polarization orientation of a reflected wave rotated by 90 degrees from that of an incident wave at a frequency within the PBG when that of the incident wave was the direction that bisects these two directions. The 3D-PC is a silicon inverse diamond structure whose lattice point shape is vacant regular octahedrons. In this work, the phase-difference, size and orientation of electric-field of the reflected wave, had been studied by using a FEM (finite element method). The analyses indicated the reason why the polarization orientation of the reflected wave is rotated by 90 degrees at the frequency within the PBG. In addition, it was found that the orbit of electric-field of the reflected wave becomes near-circularly-polarized one at another frequency within the PBG for the linear-polarization incident wave.

physics.optics↗

arXiv2019

Special reflecting features of a three-dimensional photonic crystal depending on cut surfaces oriented in the direction [001] within photonic bandgap

The reflecting features (reflected spectrum and phase) on the surface of pure-material plate depend on refractive index, extinction coefficient, incident angle, polarization direction and so on. The features, however, do not depend on a cut surface that is another uniformly processed surface in the same direction, which is obtained by being cut, etched and polished for example. In this work, the special reflecting features of a three-dimensional (3D) terahertz photonic crystal (PC) depending on the cut-surface oriented in the same direction [001], have been studied especially within photonic band gap by using a FEM (finite element method). The 3D-PC is a silicon inverse diamond structure whose lattice point shape is vacant regular octahedrons. The characteristic features were studied on four types of cut-surface that were shifted per a/4 (a: lattice constant) in the same direction [001], especially with two types of orientation, [(1,1) and (1,-1) in an XY-plane] of electric-field of the incident wave in normal incidence. It was found that eight types of reflected spectrum and those of phase in all four cut-surface types are able to be classified in two patterns, they are correlated with two types of unit cell suggested, and the reflecting features invert or do not invert according to the cut-surface.

physics.optics↗