Abstract-The active modulation of flexible terahertz tube

Jing Liu, Hongyu Ji, Jingling Shen, Cunlin Zhang, Yuejin Zhao,


https://www.sciencedirect.com/science/article/abs/pii/S0925346719304756

We demonstrated a flexible polyimide terahertz tube that can modulate Terahertz (THz) wave efficiently based on indium oxide (In2O3) nanoparticle. The transmission of the THz pulse can be modulated using optical control over 0.2 to 2.6 THz, and the modulation depth reached up to 14%. By combining nano-indium oxide layer with metal periodic metamaterial structure, the modulation was optimized to 35%. The results show that a photo-excited tunable terahertz modulator can be realized by irradiating the structure under different intensity of the laser beam.

Abstract-Reconfigurable Terahertz Quarter-Wave Plate for Helicity Switching Based on Babinet Inversion of an Anisotropic Checkerboard Metasurface

Yosuke Nakata, Kai Fukawa, Toshihiro Nakanishi, Yoshiro Urade, Kunio Okimura, and Fumiaki Miyamaru

https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.11.044008

Dynamic helicity switching by utilizing metasurfaces is challenging because it requires deep modulation of polarization states. To realize such helicity switching, this paper proposes a dynamic metasurface functioning as a switchable quarter-wave plate, the fast axis of which can be dynamically rotated by ${90}^{\circ }$. The device is based on the critical transition of an anisotropic metallic checkerboard, which realizes the deep modulation and simultaneous design of the switchable states. After verifying the functionality of the ideally designed device in a simulation, we tune its structural parameters to realize practical experiments in the terahertz frequency range. By evaluating the fabricated sample with vanadium dioxide, the conductivity of which can be controlled by temperature, its dynamic helicity switching function is demonstrated.

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Abstract-Basic phase-locking, noise, and modulation properties of optically mutual-injected terahertz quantum cascade lasers

Yuanyuan Li, Ning Yang, Yan Xie, Weidong Chu, Wei Zhang, Suqing Duan, and Jian Wang

Fig. 2 Time evolution of |EA|, |EB | (first column), the corresponding power spectral density (second column), and instantaneous frequency (third column) with different coupling strength κ and detuning frequency ΔΩ/2π. The coupling strength in the first three rows are set as κ = 9.87 × 10−3, which is the case of moderate coupling. (a)–(c) within the phase-locking regime, ΔΩ/2π = 0.5GHz, (d)–(f) out of the pahse-locking regime, ΔΩ/2π = 5GHz, (g)–(i) out of the pahse-locking regime, ΔΩ/2π = 0.55GHz. The fourth row is the case of strong coupling with κ = 0.247. (j)–(l) out of the pahse-locking regime, ΔΩ/2π = 0.2GHz. The effective injection current is 1.5Ith in all simulations.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-27-3-3146

The phase-locking, noise, and modulation properties of two face-to-face optically mutual-injected terahertz (THz) quantum cascade lasers (QCLs) are analyzed theoretically. In the phase-locking range, the two THz QCLs are in stationary states working at the same frequency. Outside the phase-locking range, the amplitude and the instantaneous frequency of the optical field oscillate with time, and the power spectrum shows a series of discrete peaks. For strong mutual injection, the optical field of the THz QCL array also exhibits oscillatory behavior. Coherent collapse or chaotic behavior is not observed within the range of the parameters used in this simulation. The spontaneous emission noise of phase-locked THz QCLs is higher than that of THz QCLs at free-running operation, and mutual injection may introduce additional modulation peaks in the noise spectrum. The modulation response of the mutual-injected THz QCLs to an individual modulation is investigated. It is found that the modulation bandwidth and the phase difference are significantly dependent on the modulation parameters. These results are helpful for further understanding the nonlinear dynamic behaviors of THz QCLs under optical injection and provide theoretical support for the development of THz QCL phase-locked arrays.

© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Graphene-based hybrid plasmonic waveguide for highly efficient broadband mid-infrared propagation and modulation

Longfang Ye, Kehan Sui, Yanhui Liu, Miao Zhang, and Qing Huo Liu

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-12-15935

In this paper, a graphene-based hybrid plasmonic waveguide is proposed for highly efficient broadband surface plasmon polariton (SPP) propagation and modulation at mid-infrared (mid-IR) spectrum. The hybrid plasmonic waveguide is composed of a monolayer graphene sheet in the center, a polysilicon gating layer, and two inner dielectric buffer layers and two outer parabolic-ridged silicon substrates symmetrically placed on both sides of the graphene. Owing to the unique parabolic-ridged waveguide structure, the light-graphene interaction and subwavelength SPPs confinement of the fundamental SPP mode for the hybrid waveguide can be significantly increased. Under the graphene chemical potential of 1.0 eV, the proposed waveguide can achieve outstanding SPP propagation performance with long propagation length of 12.1-16.7 μm and small normalized mode area of ~10−4 in the frequency range of 10-20 THz, exhibiting more than one order smaller in the normalized mode area while remaining the propagation length almost the same level with respect to the hybrid plasmonic waveguide without parabolic ridges. By tuning the graphene chemical potential from 0.1 to 1.0 eV, we demonstrate the waveguide has a modulation depth greater than 51% for the frequency ranging from 10 to 20 THz and reaches a maximum of nearly 100% at the frequency higher than 18 THz. Benefitting from the excellent broadband mid-IR propagation and modulation performance, the graphene-based hybrid plasmonic waveguide may open up a new way for various mid-IR waveguides, modulators, interconnects and optoelectronic devices.

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

Abstract-Mechanical Terahertz Modulation Based on Single-Layered Graphene

Long Cheng, Zuanming Jin, Zongwei Ma, Fuhai Su, Yang Zhao, Yongzhuan Zhang, Tongyu Su, Yan Sun, Xueli Xu, Zhi Meng, Yuecheng Bian, Zhigao Sheng


http://onlinelibrary.wiley.com/doi/10.1002/adom.201700877/full

The 2D terahertz (THz) modulator, enabling efficient manipulation of such versatile band in nanoscale, is crucial for THz microdevices and systems, but its implementation is difficult and remains challenging in practice. Here, a novel 2D THz modulator based on single-layered graphene under mechanical strain is demonstrated. Bidirectional, i.e., both positive and negative, THz modulation effect is realized by utilizing unconventionally distributed strains on graphene. Such mechanical modulation is found to be stable and reversible, and its modulation depth can exceed 26% at 1 THz under 10–2 GPa strain. Observations of both the strain and frequency dependent modulation behavior evidence the mechanical strain-induced change of the Dirac-like energy dispersion in graphene, which is distinctive from that of the electrical and optical approaches. Due to the reliability and wide applicability of mechanical forces, these results provide an alternative route for chip-scale THz modulation devices based on 2D materials.

Abstract-Terahertz modulation based on surface plasmon resonance by self-gated graphene

Zhenhai Qian, Dongxiao Yang, Wei Wang

https://www.sciencedirect.com/science/article/pii/S0030401817311604

We theoretically and numerically investigate the extraordinary optical transmission through a terahertz metamaterial composed of metallic ring aperture arrays. The physical mechanism of different transmission peaks is elucidated to be magnetic polaritons or propagation surface plasmons with the help of surface current and electromagnetic field distributions at respective resonance frequencies. Then, we propose a high performance terahertz modulator based on the unique PSP resonance and combined with the metallic ring aperture arrays and a self-gated parallel-plate graphene capacitor. Because, to date, few researches have exhibited gate-controlled graphene modulation in terahertz region with low insertion losses, high modulation depth and low control voltage at room temperature. Here, we propose a 96% amplitude modulation with 0.7 dB insertion losses and ∼$$5.5 V gate voltage. Besides, we further study the absorption spectra of the modulator. When the transmission of modulator is very low, a 91% absorption can be achieved for avoiding damaging the source devices.

Abstract-Terahertz Plasmonic Field-Induced Conductivity Modulation in Gold

A. Y. Elezzabi,

P. Maraghechi

& S. R. Greig

http://www.nature.com/srep/2015/150610/srep10812/full/srep10812.html

We report the observation of terahertz (THz) electric field induced conductivity modulation in sub-wavelength gold plasmonic media. Through all-THz pump-probe time-resolved transmission spectroscopy, we demonstrate that the presence of induced surface charges influences near-field mediated light propagation. The phenomenon is ascribed to the enhanced metal conductivity due to enhanced surface density of conduction electrons. The surface induced charge dynamics are revealed via phase-dependent time-resolved signatures. The phenomenon is a prelude to a wide class of ultrafast active THz plasmonic devices and paves the way for plasmonic field effects devices, similar to semiconductor ones.