Abstract-Terahertz beam focusing through designed oblique metal-slit array

Takehito Suzuki, Masashi Sekiya,  Hideaki Kitahara,

https://www.osapublishing.org/ao/abstract.cfm?uri=ao-58-15-4007

Manipulation of propagating beams is essential in applications, and the potentially arising phenomena offer attractive optical components. However, the design of optical components using only naturally occurring materials has approached physical limits, and artificial materials such as metamaterials and metasurfaces are a way forward to open the door to sophisticated optical components. This paper shows manipulation of terahertz beams through designed oblique metal-slit arrays where a common metal-slit array does not perform as a lens. The oblique metal-slit array has a refractive index determined as a function of a steep angle. The lens consists of multiple metal plates with a designed oblique angle, and a convex output structure produces a focusing effect. We also suggest that the Brewster phenomenon in the lens can simply enhance the electric field intensity at the focal point. The Brewster condition of the lens is correlated with a jagged edged face on the input side with an appropriate metal-slit spacing and thickness. The phenomenon would be applicable to numerous promising components and applications such as gain-enhancement optical components and perfect impedance-matching polarizers.

© 2019 Optical Society of America

Abstract-Negative refractive index metamaterial with high transmission, low reflection, and low loss in the terahertz waveband

Takehito Suzuki, Masashi Sekiya, Tatsuya Sato,Yuki Takebayashi,

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-7-8314

The refractive index is a basic parameter of materials which it is essential to know for the manipulation of electromagnetic waves. However, there are no naturally occurring materials with negative refractive indices, and high-performance materials with negative refractive indices and low losses are demanded in the terahertz waveband. In this paper, measurements by terahertz time-domain spectroscopy (THz-TDS) demonstrate a metamaterial with a negative refractive index n of −4.2 + j0.17, high transmitted power of 81.5%, low reflected power of 4.3%, and a high figure of merit (FOM = |Re(n)/Im(n)|) of 24.2 at 0.42 THz. The terahertz metamaterial with these unprecedented properties can provide various attractive terahertz applications such as superlenses with resolutions beyond the diffraction limit in terahertz continuous wave imaging.

© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement