Abstract-Modulators for mid-infrared and terahertz light

 

Journal of Applied Physics

Eric Herrmann,  Hua Gao, Zhixiang Huang, Sai Rahul Sitaram, Ke Ma,  Xi Wang, 

(a) Schematic drawing of a hybrid silicon split-ring resonator metasurface pumped by near-infrared femtosecond pulses. (b) Co-polarized transmission efficiency when pumping is ON (red) and OFF (blue). (a) and (b) Reproduced with permission from Cong et al., Light Sci. Appl. 7, 28 (2018). Copyright 2018 Springer Nature. (c) Schematic drawing of germanium-coated aluminum split-ring resonator metasurface on Kapton film, pumped by an 800 nm pulse. (d) THz transmission amplitude through the metasurface for various pump-probe delay times. (c) and (d) Reproduced with permission from Lim et al., Adv. Mater. 30, 1705331 (2018). Copyright 2018 John Wiley and Sons.

https://aip.scitation.org/doi/abs/10.1063/5.0025032

The rise of mid-infrared and terahertz wave technology over the past two decades has led to incredible insights and potential applications for next-generation optoelectronics. Modulators, which control amplitude, phase, and/or polarization of incident light, are widely used in communications, imaging, and sensing and are crucial for further development of technology functioning in the mid-infrared and terahertz frequency regimes. The lack of natural materials with optical responses in these frequency regimes has led to a surge in engineering efforts to create novel devices and architectures for achieving control over the properties of mid-infrared and terahertz radiation. Major efforts in the field have been devoted to studying carrier concentration modulation, liquid crystals, phase-change materials, and micro-electromechanical systems for controlling the light–matter interaction. Although there has been considerable progress in realizing mid-infrared and terahertz modulators, novel approaches are seeking higher modulation speed, more functionality, and miniaturized size. In this perspective, we review the recent advancements of modulators for mid-infrared and terahertz wavelengths. We discuss various modulation mechanisms, along with their relative performance, and consider future architectures to improve upon the current technology for mid-infrared and terahertz modulation.

Abstract-Insights into the water status in hydrous minerals using terahertz time-domain spectroscopy

Yuanyuan Ma, Haochong Huang, Sibo Hao, Kunfeng Qiu, Hua Gao, Lu Gao, Weichong Tang, Zili Zhang, Zhiyuan Zheng


https://www.nature.com/articles/s41598-019-45739-2

The determinations of water status incorporated in hydrous minerals are of considerable significances in geoscience fields. Coincidentally, the aqueous sensitivity of terahertz radiation has motivated numerous explorations in several cross-domain applications. Terahertz time-domain spectroscopy is employed as a major probing technique coupling of traditional detecting methods to uncover the mask of water status in copper sulfate pentahydrate as well as mineral quartz in this article. Based on the quantitative identification of water status in copper sulfate pentahydrate, the water incorporated in mineral quartz is verified qualitatively. Notable differences of optical constants originating from the water content are obtained for copper sulfate pentahydrate and mineral quartz. These present works indicate that terahertz technology can be considered as a promising method to satisfy the ever-increasing requirements in hydrous mineral analyses.

Abstract-Nanofocusing of terahertz wave in a tapered hyperbolic metal waveguide

Nanofocusing of terahertz wave in a tapered hyperbolic metal waveguide Hua Gao, Qing Cao, Minning Zhu, Da Teng, and Siyi Shen  »View Author Affiliations

Optics Express, Vol. 22, Issue 26, pp. 32071-32081 (2014)
http://dx.doi.org/10.1364/OE.22.032071

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http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-22-26-32071

Abstract

An tapered hyperbolic metal waveguide is suggested for the nanofocusing of terahertz waves. We numerically show that, at the frequency of 1 THz, the focal spot can be as small as only 5 nm, which is smaller than that of a plate waveguide by 2 orders of magnitude. Correspondingly, the longitudinal component of the energy flow density is stronger than that of a plate waveguide by 3 orders of magnitude for the same input. It is shown that these significant improvements come from the small imaginary part of the effective index of the hyperbolic metal waveguide.

© 2014 Optical Society of America