Abstract-Tunable terahertz dual-band perfect absorber based on the combined InSb resonator structures for temperature sensing

Hao Luo, Xi Wang, and Hang Qian

https://www.osapublishing.org/josab/abstract.cfm?uri=josab-38-9-2638

In this paper, a tunable perfect absorber (PA) based on a combined InSb resonator structure is proposed and investigated numerically in the terahertz (THz) region, which can serve as a dual-band temperature sensor. The unit cell of the proposed PA consists only of the combined InSb ring-disk-shaped resonator structures adhered on a continuous gold film and dielectric substrate. The permittivity of the InSb material is highly dependent on the variation of the external temperature. Numerical simulation results indicate that the proposed PA at a temperature of 290 K can achieve absorbance of 99.4% and 98.7% at 1.598 THz and 1.926 THz, respectively. The two absorption peaks are mainly attributed to the excitation of fundamental dipolar resonance modes caused by the ring-shaped and disk-shaped structures, separately. The absorption properties of the proposed PA can be adjusted by varying the structure parameters. Furthermore, the proposed dual-band PA can function as a temperature sensor with sensitivities of about 8.54 GHz/K and 16.25 GHz/K, respectively. Due to its excellent performance, the proposed dual-band PA could find many potential applications of thermal emitting, sensing, and detecting in the THz regime.

© 2021 Optical Society of America

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- Tunable terahertz/infrared coherent perfect absorption in a monolayer black phosphorus

Xi Wang, Qian Ma, Leiming Wu, Jun Guo, Shunbin Lu, Xiaoyu Dai, and Yuanjiang Xiang

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-5-5488

Black phosphorus (BP), a promising new two-dimensional (2D) material, has drawn a lot of attentions in academia and industry due to its extraordinary physical and chemical properties. In this paper, we theoretically demonstrate a monolayer BP that achieves coherent perfect absorption (CPA) at the THz/infrared band. It is found that quasi-CPA point does exist at the THz/infrared band. The CPA, which has a relative bandwidth of 141.3% and a coherent absorptivity of more than 90%, can be implemented at the quasi-CPA wavelength through a proper phase modulation. Moreover, the coherent absorptivity can be modulated with a high modulation depth by means of the phase difference between the two coherent counter-propagating beams. The angular selectivity of the monolayer BP is also investigated. The CPA wavelength is divided into two wavelength branches for TE and TM polarization at oblique incidence. In addition, the CPA wavelength can be tuned from THz to infrared band by adjusting the electron doping of the BP while maintaining the modulation depth of 104. Hence, our results may be potentially used for coherent modulations in terahertz/infrared detections and signal processing with 2D materials.

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

Abstract-Tunable and multichannel terahertz perfect absorber due to Tamm surface plasmons with graphene

Xi Wang, Xing Jiang, Qi You, Jun Guo, Xiaoyu Dai, and Yuanjiang Xiang

https://www.osapublishing.org/prj/abstract.cfm?uri=prj-5-6-536

In this paper, we have shown that perfect absorption at terahertz frequencies can be achieved by using a composite structure where graphene is coated on one-dimensional photonic crystal (1DPC) separated by a dielectric. Due to the excitation of optical Tamm states (OTSs) at the interface between the graphene and 1DPC, a strong absorption phenomenon occurs induced by the coupling of the incident light and OTSs. Although the perfect absorption produced by a metal–distributed Bragg reflector structure has been researched extensively, it is generally at a fixed frequency and not tunable. Here, we show that the perfect absorption at terahertz frequency not only can be tuned to different frequencies but also exhibits a high absorption over a wide angle range. In addition, the absorption of the proposed structure is insensitive to the polarization, and multichannel absorption can be realized by controlling the thickness of the top layer.

© 2017 Chinese Laser Press