Abstract-All-dielectric metamaterial analogue of electromagnetically induced transparency and its sensing application in terahertz range

Tian Ma, Qiuping Huang, Hongchuan He, Yi Zhao, XIaoxia Lin, and Yalin Lu

Fig. 2 (a) Schematic of the all-dielectric metamaterial composed of two asymmetric split ring resonators. Inset: top view of the unit cell. All dimensions shown here are $h=100\mu m,$ $t=30\mu m,$ $P_x=400\mu m,$ $P_y=400\mu m,$ $R_1=75\mu m,$ $R_2=75\mu m,$ $\alpha =160°,$ and $\beta =120°.$ (b) Microscopy of the fabricated sample. Bars refer to 500μm. (c) Transmission spectra and (d) corresponding group delay of the proposed metamaterial

http://aoip.osa.org/oe/abstract.cfm?uri=oe-27-12-16624

A novel electromagnetically induced transparency (EIT) all-dielectric metamaterial is proposed, fabricated, and characterized. The unit cell of the proposed metamaterial comprises of two asymmetric split ring resonators (a-SRRs) positioned with a mirror symmetry. The asymmetric nature of a-SRRs results from the length difference of two arcs. Optical properties of the fabricated metamaterial are investigated numerically using finite difference method, as well as experimentally using a terahertz time-domain spectroscopy. The results confirm that the proposed metamaterial exhibits an EIT transparent window in the frequency range around 0.78THz with a Q-factor of ~75.7 and a time-delay up to ~28.9ps. Theoretical investigations show that EIT effects in our metamaterial are achieved by hybridizing two bright modes in the same unit cell, which are aroused by the excitation of magnetic moments. We also confirm that the proposed metamaterial has great potential for sensing applications with high sensitivity and high figure of merit (FOM), which guarantees potential applications in in situ chemical and biological sensing.

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

Abstract-Design of a Pre-Bunched THz Free Electron Laser

Ruixuan Huang, Weiwei Li,  Zhouyu Zhao, Heting Li, Jigang Wang, Tian Ma, Qiuping Huang, Zhigang He, Qika Jia, Lin Wang, Yalin Lu

https://www.mdpi.com/2571-712X/1/1/21/htm

Terahertz (THz) radiation has attracted much attention in new scientific and industrial applications. There has been significant recent progress in generating THz with accelerators. To investigate the collective behavior of electron dynamics, we have proposed a new high throughput material characterization system, which supplies a multiple light source. The system includes a pre-bunched THz free electron laser (FEL), which is a high-power narrow-band THz source with a wide tuning range of frequency. The physical design with the main components of the facility is introduced, and the simulation results are illustrated. Radiation of 0.5–3.0 THz is obtained by the fundamental wave of the pre-bunched beam, and radiation covering 3.0–5.0 THz is realized by second harmonic generation. As the simulation shows, intense THz radiation could be achieved in a frequency from 0.5–5.0 THz, with a peak power of several megawatts (MWs) and a bandwidth of a few percent.

Abstract-Metallized 3D printed hollow core waveguide Bragg grating for dispersion compensation in terahertz range

Tian Ma, Kathirvel Nallapan,  Hichem Guerboukha,  Maksim Skorobogatiy

http://ieeexplore.ieee.org/document/8066906/

A novel terahertz (THz) waveguide Bragg grating is proposed for dispersion compensation. The results confirm single mode guidance of the fundamental mode, as well as large negative group velocity dispersion in the vicinity of 0.14THz and 0.16THz, respectively.

Abstract-Analog signal processing in the terahertz communication links using waveguide Bragg gratings: example of dispersion compensation

Tian Ma, Kathirvel Nallapan, Hichem Guerboukha, and Maksim Skorobogatiy

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-10-11009

We study the possibility of analog signal processing for the upcoming terahertz (THz) high-bitrate communications using as an example the problem of dispersion compensation in the THz communication links. In particular, two Waveguide Bragg Grating devices (WBGs) operating in the transmission mode are detailed. WBGs are designed by introducing periodic corrugation onto the inner surface of the metalized tubes. The resultant devices operate in a single mode regime either in the vicinity of the modal cutoff or in the vicinity of a bandgap edge, featuring large negative group velocity dispersions (GVD). We fabricate the proposed WBGs using 3D stereolithography, and metallize them using wet chemistry. Optical properties of the fabricated WBGs are investigated both theoretically and experimentally. The results confirm single mode guidance, relatively high coupling efficiency, as well as large negative group velocity dispersions in the range of several -100’s ps/(THz · cm) in the vicinity of 0.14THz. This makes the short sections of proposed WBGs suitable for compensating positive dispersion incurred in the THz wireless links or fiber-assisted THz interconnects for signals of several-GHz bandwidth. Finally, we comment on the challenges associated with the analog signal processing in the THz spectral range.

© 2017 Optical Society of America

Abstract-3D Printed Hollow-Core Terahertz Optical Waveguides with Hyperuniform Disordered Dielectric Reflectors

http://onlinelibrary.wiley.com/doi/10.1002/adom.201600171/full

Novel hollow-core THz waveguides featuring hyperuniform disordered reflectors are proposed, fabricated, and characterized. The reflector comprises aperiodically positioned dielectric cylinders connected with dielectric bridges. The proposed waveguides are fabricated using a 3D MultiJet printer. Optical properties of the fabricated waveguides are investigated numerically using finite element method, as well as experimentally using terahertz time-domain spectroscopy. The results confirm that proposed waveguides exhibit sizable photonic bandgaps (21%) even with relatively low refractive index contrast (resin/air). Position of the bandgaps can be easily tuned by varying reflector geometrical parameters.