Abstract-Broadband high-resolution terahertz single-pixel imaging

Adam Vallés, Jiahuan He, Seigo Ohno, Takashige Omatsu, Katsuhiko Miyamoto

https://arxiv.org/abs/2006.05877

We report a simple single-pixel imaging system with a low mean squared error in the entire terahertz frequency region (3-13 THz) that employs a thin metallic ring with a series of directly perforated random masks and a subpixel mask digitization technique. This imaging system produces high-quality reconstructed images with resolutions of up to 320 x 320 pixels. It can be extended to develop advanced imaging systems in the near-ultraviolet to terahertz region.

Abstract-Terahertz-wave generation from surface phonons at forbidden frequencies of lithium niobate

Jun-ichi Shikata, Seigo Ohno, Hiroaki Minamide,

https://www.jstage.jst.go.jp/article/elex/advpub/0/advpub_17.20200133/_article

This paper describes terahertz (THz)-wave generation within forbidden bands in polar crystals, focusing on the A1 phonon modes in lithium niobate. This material exhibits two negative-permittivity frequency ranges at 7.4-12.7 THz and 18.8-25.6 THz for the lowest and highest A1 modes, respectively. Exploiting the finite-difference time-domain simulations, we demonstrate that both the surface phonon modes can be radiative with a structured grating. Fourier analyses of the radiative fields reveal the relevant peaks in the spectrum as well as the dispersion relations. Our results provide a novel method for coherent THz-wave sources at unexplored THz frequencies.

Abstract-Off-resonance and in-resonance metamaterial design for a high-transmission terahertz-wave quarter-wave plate

Zhengli Han, Seigo Ohno, Yu Tokizane, Kouji Nawata, Takashi Notake, Yuma Takida, and Hiroaki Minamide

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-43-12-2977

This Letter describes a novel metamaterial design by employing off-resonance and in-resonance excitation for a high-transmission terahertz-wave quarter-wave plate (QWP). The device is demonstrated with a thin film metamaterial with double-layer split ring resonators (SRRs). Different from a usual resonant metamaterial device, here we design the work frequency off from the inductor-capacitor (LC) resonance for the TE mode, while in a dipole resonance for the TM mode to obtain the artificial birefringence. Rectangular SRRs in this Letter provide a choice to optimize the off-resonance and in-resonance excitation, to assist the double-layer design for high transmission. Converting a linearly polarized wave to circular polarization with our QWP, the experiment confirms a transmittance of 0.8 and an ellipticity of 0.99 at 0.98 THz. The developed thin film device is flexible and has a thickness of 48 μm (sub-wavelength). This is an advantage for potential integration in systems where overall device compactness is required.

© 2018 Optical Society of America

Abstract-Thin terahertz-wave phase shifter by flexible film metamaterial with high transmission

Zhengli Han, Seigo Ohno, Yu Tokizane, Kouji Nawata, Takashi Notake, Yuma Takida, and Hiroaki Minamide

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-25-31186

Thin terahertz (THz)-wave optical components are fundamentally important for integrated THz-wave spectroscopy and imaging systems, especially for phase manipulation devices. As described herein, a thin THz-wave phase shifter was developed using a flexible film metamaterial with high transmission and polarization independent properties. The metamaterial unit structure employs double-layer un-split ring resonators (USRRs) with a designed distance between the two layers to obtain phase retardance of π/2, thus constituting a THz-wave phase shifter. The metamaterial design keeps the transmission coefficient as high as 0.91. The phase shifter also has polarization independence due to the four-fold symmetry of the USRR structure. Because of the subwavelength feature size of the USRR, this shifter can offer benefits for manipulating the spatial profile for the THz-wave phase through design of a binary optics phase plate by arranging a USRR array. The thickness of 48 μm has benefits for developing integrated THz optics and other applications that demand compactness and flexibility. The developed film size of 5 cm × 5 cm from the device fabrication process is suitable for THz lenses or gratings of large optical components.

© 2017 Optical Society of America under the terms of the OSA Open Access Publishing