Abstract-Active Optically Controlled Broadband Terahertz Modulator Based on Fe3O4Nanoparticles

 Lu-Yao Xiong,   Bo Zhang,   Hong-Yu Ji,  Wei Wang,   Xin Liu,  Shu-Li He, Jing-Ling Shen

https://ieeexplore.ieee.org/document/8409966/

We report an active broadband terahertz (THz) modulator based on an Fe 3 O 4 nanoparticle/silicon (Si) structure, where the interface effects were measured in a homemade THz time-domain spectroscopy system. An approximately 100-nm Fe 3 O 4 nanoparticle thin film on the high-resistance Si substrate was easily attained by spin-coating ferrofluids. In our experiment, a modulation depth as high as 92% was achieved at an external laser irradiance of 3.6 W/cm 2 . This result can be explained by the accumulation of carriers at the interface of the hybrid structure, which induces intense absorption of the THz transmission. In addition, the limit modulated frequency of the device is ∼12 kHz. The superior performance of this device for THz wave modulation in comparison to other nanomaterial-based THz modulators and the ease of fabrication both illustrate that this is a promising method in the modulation of THz transmission. Furthermore, this modulator could also potentially provide an essential component in a wide variety of technologies, such as THz communications, THz imaging, etc.

Abstract-Low-loss terahertz polarization splitter based on an asymmetric dual-suspended-core fiber

Yuan-Feng Zhu,  Xin Liu,  Chun-Fang Rao; Hua Zhong, Hai-Mei Luo,  Yan-Hua Chen, Zhi-Qing Ye,  Hua Wang,

https://www.spiedigitallibrary.org/journals/Optical-Engineering/volume-57/issue-8/086112/Low-loss-terahertz-polarization-splitter-based-on-an-asymmetric-dual/10.1117/1.OE.57.8.086112.short?SSO=1

A relatively simple design of a terahertz (THz) polarization splitter based on an asymmetric dual-suspended-core fiber is proposed. One core is formed by two intersecting rectangular dielectric strips with dissimilar thickness, whereas the other is a round solid core suspended by crossed dielectric strips with the same thickness. The distance between the cores can be adjusted to ensure a short splitting length and low transmission loss. A THz polarization splitter with a length of 1.27 cm is realized with a low transmission loss of 0.53 and 0.67 dB for the x- and y-polarization modes, respectively. An extinction ratio of about −20  dB and a broad bandwidth of 0.046 THz are demonstrated.

© 2018 Society of Photo-Optical Instrumentation Engineers (SPIE)

Abstract-An active optically controlled broadband terahertz modulator based on Fe3O4 nano-particles

Luyao Xiong, Bo Zhang, Hongyu Ji, Wei Wang, Xin Liu, and Jing L. Shen

https://www.osapublishing.org/abstract.cfm?uri=ISUPTW-2018-TuK34

We report an active easily fabricated broadband terahertz modulator based on Fe3O4 nano-particles/Si structure,for which as high as 92% modulation depth was achieved at an external excitation laser of 3.6 W/cm2.

© 2018 OSA

Abstract-Magnetically controlled terahertz modulator based on Fe3O4 nanoparticle ferrofluids

Xin Liu, Luyao Xiong, Xiang Yu, Shuli He, Bo Zhang, Jingling Shen

http://iopscience.iop.org/article/10.1088/1361-6463/aaab97/meta


A multifunctional terahertz (THz) wave modulator fabricated from Fe3O4 nanoparticle ferrofluids and metamaterials was characterized in externally applied magnetic fields. Specifically, modulation depths and frequency shifts by the wave modulators were examined. A 34% THz amplitude modulation depth was demonstrated and the absorption peak of the metamaterial induced a frequency shift of 33 GHz at low magnetic field intensities. It is anticipated that this device structure and its tunable properties will have many potential applications in THz filtering, modulation, and sensing.

Abstract-Design of an all-optical fractional-order differentiator with terahertz bandwidth based on a fiber Bragg grating in transmission

Xin Liu and Xuewen Shu

https://www.osapublishing.org/ao/abstract.cfm?uri=ao-56-24-6714&origin=search

All-optical fractional-order temporal differentiators with bandwidths reaching terahertz (THz) values are demonstrated with transmissive fiber Bragg gratings. Since the designed fractional-order differentiator is a minimum phase function, the reflective phase of the designed function can be chosen arbitrarily. As examples, we first design several 0.5th-order differentiators with bandwidths reaching the THz range for comparison. The reflective phases of the 0.5th-order differentiators are chosen to be linear phase, quadratic phase, cubic phase, and biquadratic phase, respectively. We find that both the maximum coupling coefficient and the spatial resolution of the designed grating increase when the reflective phase varies from quadratic function to cubic function to biquadratic function. Furthermore, when the reflective phase is chosen to be a quadratic function, the obtained grating coupling coefficient and period are more likely to be achieved in practice. Then we design fractional-order differentiators with different orders when the reflective phase is chosen to be a quadratic function. We see that when the designed order of the differentiator increases, the obtained maximum coupling coefficient also increases while the oscillation of the coupling coefficient decreases. Finally, we give the numerical performance of the designed 0.5th-order differentiator by showing its temporal response and calculating its cross-correlation coefficient.

© 2017 Optical Society of America

Abstract-Monolayer graphene based organic optical terahertz modulator

Guocui Wang, Bo Zhang, Hongyu Ji,   Xin Liu, Ting He, Longfeng Lv, Yanbing Hou,  Jingling Shen,

http://aip.scitation.org/doi/full/10.1063/1.4973816

We investigate a high-efficiency broadband terahertz wave modulator with structures made from the conjugated polymer [2-methoxy-5-(2′-ethylhexyloxy)-1, 4-phenylennevinylene], graphene, and Si, irradiated with an external excitation laser. We demonstrate a strategy that can alleviate the tradeoff between the requirements of modulation depth and modulation speed in polymer/silicon terahertz wave modulators. Using terahertz time-domain and continuous-wave systems, we measured both the terahertz transmission modulation properties and the time responses of the modulator structures. The conjugated polymer/graphene/silicon structure achieved a high modulation factor of 93% for transmission as well as improved the modulation speed of the devices based on polymer/silicon. The high modulation efficiency of the polymer/graphene/silicon structure was induced by the enhancement in carrier density and the extremely high carrier mobility of graphene, respectively.

Abstract-Mechanically tunable terahertz graphene plasmonics using soft metasurface

Li Wang, Xin Liu, Jianfeng Zang,
http://iopscience.iop.org/article/10.1088/2053-1583/3/4/041007/meta;jsessionid=EB8BDE24B94CFE0F02A24EBB8E8B9051.c1.iopscience.cld.iop.org

This letter presents a new approach to continuously tune the resonances of graphene plasmons in terahertz soft metasurface. The continuous tunability of plasmon resonance is either unachievable in conventional plasmonic materials like noble metals or requires gate voltage regulation in graphene. Here we investigate a simplest form of terahertz metasurface, graphene nanoribbon arrays (GNRAs), and demonstrate the graphene plasmon resonance modes can be tailored by mechanical deformation of the elastomeric substrate using finite element method (FEM). By integrating the electric doping with substrate deformation, we have managed to tune the resonance wavelength from 13.7 to 50.6μm. The 36.9 μm tuning range is nearly doubled compared with that by electric doping regulation only. Moreover, we observe the plasmon coupling effect in GNRAs on waved substrate and its evolution with substrate curvature. A new decoupling mechanism enabled by the out-of-plane separation of the adjacent ribbons is revealed. The out-of-plane setup of plasmonic components extends the fabrication of plasmonic devices into three-dimensional space, which simultaneously increases the nanoribbon density and decreases the coupling strength. Our findings provide an additional degree of freedom to design reconfigurable metasurfaces and metadevices.