Abstract-Curved terahertz surface plasmonic waveguide devices

Mingrui Yuan, Yongchang Lu, Ying Zhang, Ziying Zhang, Yanfeng Li, Hongchao Liu, Xixiang Zhang, Jiaguang Han, Weili Zhang,

Structure and dispersion relation. (a) Schematic diagram and geometric parameters of the structure (the red arrow depicts the propagation direction of SPPs). The lower left inset shows the SEM image of the fabricated arc-shaped curved hole array excitation region as well as the fan-shaped coupling region. The lower right inset shows the fabricated waveguide structure. (b) The simulated dispersion relation (red line) of SPP mode for one row of metal pillars.

https://www.osapublishing.org/oe/abstract.cfm?URI=oe-28-2-1987

Strongly confined surface waves can be achieved on periodically structured metal surfaces and are known as spoof surface plasmon polaritons (SPPs). In this work, several terahertz SPP devices based on curved waveguides are demonstrated. The transmittance and bending loss of 90-degree curved spoof SPP waveguides with a radius of curvature ranging from 200 to 2300 µm are investigated to identify the regime for high transmission. A commutator is designed and experimentally demonstrated. Furthermore, coupling equations are derived and verified for efficient coupling between bend-straight waveguides and between bend-bend waveguides. The results will be of great value for future integrated terahertz plasmonic systems.

© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Parallel-plate waveguides for terahertz-driven MeV electron bunch compression

Mohamed A. K. Othman, Matthias C. Hoffmann, Michael E. Kozina, X. J. Wang, R. K. Li, and Emilio A. Nanni

Fig. 1 (a) Terahertz tapered parallel-plate waveguide for MeV electron bunch compression. (b) Example of single cycle THz waveform measured using EOS in free space (with a 100 µm thick GaP crystal) and its spectrum in (c) that is coupled into the structure. (d) The resulting electric field profile of the coupled THz electric field Ez field at a single frequency (0.65 THz).

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-27-17-23791

We demonstrate the electromagnetic performance of waveguides for femtosecond electron beam bunch manipulation and compression with strong-field terahertz (THz) pulses. The compressor structure is a dispersion-free exponentially-tapered parallel-plate waveguide (PPWG) that can focus single-cycle THz pulses along one dimension. We show test results of the tapered PPWG structure using electro-optic sampling (EOS) at the interaction region with peak fields of at least 300 kV/cm, given 0.9 µJ of incoming THz energy. We also present a modified shorted design of the tapered PPWG for better beam manipulation and reduced magnetic field as an alternative to a dual-feed approach. As an example, we demonstrate that with 5 µJ of THz energy, the PPWG compresses a 2.5 MeV electron bunch by a compression factor of more than 4, achieving a bunch length of about 18 fs.

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

Abstract-Eight-Capillary Cladding THz Waveguide With Low Propagation Losses and Dispersion

Maxim M. Nazarov,  Artur V. Shilov,  Kazbek A. Bzheumikhov,  Zaur Ch. Margushev,  Viktor I. Sokolov, Alexander B. Sotsky,  Alexander P. Shkurinov,

https://ieeexplore.ieee.org/document/8281070

We investigated the perspectives of a hollow core fiber with a cladding of eight polypropylene capillaries that provides flexibility, low propagation losses, and a single-mode regime in the terahertz frequency range. Optimization procedure is developed. The 7-dB/m propagation loss for 1.3-mm core size and 20-cm waveguide length is experimentally demonstrated at 2-2.2 THz frequency band. The measured group velocity dispersion do not exceed 1 ps/(THz·cm). The theoretical calculations based on the method of Green's functions confirm the experimental data, demonstrate the influence of capillary radius and wall thickness and predict 1.7-dB/m propagation losses for optimized geometry.

Abstract-Generation and investigation of terahertz Airy beam realized using parallel-plate waveguides

M. Wu, G. Shi,  T. Lang, Z. Han,

https://www.researchgate.net/publication/322193871_Generation_and_investigation_of_terahertz_Airy_beam_realized_using_parallel-plate_waveguides

In this paper, the launching of Airy beam in the terahertz region using waveguiding structures was proposed, designed and numerically characterized. By properly designing the waveguide slit width and the packing number in different sections of parallel-plate waveguides (PPWGs) array, arbitrary phase delay and lateral position-dependent amplitude transmission through the structure, required to realize the target Airy beam profile, can be easily fulfilled. Airy beams working at the frequency of 0.3 THz with good non-diffracting, self-bending, and self-healing features are demonstrated. This study represents a new alternative to scattering-based metasurface structures, and can be utilized in many modern applications.

Abstract-Thermally Tunable Narrow Band Filter Achieved by Connecting Two Opaque Terahertz Waveguides

Lan-Lan Xu,  Zhi-Yong Tao,  Tang-Qing Sang , Dan Xu,  Peng-Fei Wang, Ya-Xian Fan,

http://ieeexplore.ieee.org/document/7896525/


We propose a thermally tunable terahertz narrow band filter by combining two different periodic waveguides. When the terahertz tube wall is corrugated periodically, the transparent spectrum presents a very complex structure as various pass and stopbands emerging. The terahertz wave cannot propagate through the waveguide when its frequency falls into the stopbands. When we connected two tubes with different types of stopbands, it is very intriguing that we have found an unexpected ultra-narrow-band transparency in the frequency gap. Our findings provide a more feasible and effective terahertz waveguide filter beyond these existing ones. By using the finite-element method, we have obtained the filtering characteristics of the proposed structures. The filter bandwidth could be narrowed from 2.3 GHz to 0.29 MHz by increasing the number of waveguide segments and the highest Q -factor achieved is about 3.5×106 . Moreover, the tunability on temperature is obtained in a waveguide device of Au based on the combination of opaque structures.

Abstract-Terahertz Spectrometer of Wavelength Dimensions Based on Extraordinary Transmission

Meredith Henstridge, J. Zhou, L. Jay Guo, R. Merlin

(Submitted on 21 Nov 2016)

https://arxiv.org/abs/1611.07101

Subwavelength-slotted parallel plate waveguides exhibit a localized electromagnetic resonance bound to the slits at a frequency slightly below the transverse electric cutoff [R. Merlin, Phys. Rev. X 2, 031015 (2012)]. The resonance is long-lived and, as opposed to the vanishingly small transmission shown by a single sub-wavelength aperture, it gives perfect transmission for perfectly-conducting plates. We show that the aperture-supported resonances of a pair of slotted copper plates have long lifetimes at THz frequencies. Finite element method calculations show that these bound resonances can have quality factors greater than 100. Effects of plate length and imperfect parallel alignment are also discussed. Using THz time domain spectroscopy, we measured the transmission of a broadband pulse through a test structure for several plate separations. These results suggest that the slotted waveguide can function as a highly compact THz spectrometer.

Abstract-Artificial Dielectrics: Ordinary Metallic Waveguides Mimic Extraordinary Dielectric

2Author(s)

Mendis, R. ; Rice University, Houston, TX 77005 United States ; Mittleman, D.

http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6954587&sortType%3Dasc_p_Sequence%26filter%3DAND%28p_IS_Number%3A6954433%29

Consider an electromagnetic wave propagating in the empty space between two parallel metal plates. This situation is often the first example of guided waves encountered by undergraduate students since the solutions (the guided modes) are analytic and easily obtained. And yet, this seemingly simple configuration can give rise to a number of interesting and even counterintuitive phenomena. For the set of modes with the electric field pointing parallel to the surfaces of the two metal plates, the region between the plates, though simply empty space, mimics the properties of a dielectric medium with a wave velocity yp different from c, that of waves in vacuum. The waveguide therefore can be described as an artificial dielectric [1] with an effective refractive index n=c/yp different from unity. In contrast to naturally occurring dielectrics for which n 2 1, n can have a value less than unity. These waveguide-based artificial dielectrics were first introduced in a small body of work by the microwave community about half a century ago [2]-[5]. As discussed here [6]-[10], the wavelength scaling that results when moving from the microwave region to the terahertz (THz) region results in more practical structural dimensions. This gives new life to these artificial dielectrics for a variety of novel and exotic applications in THz science and technology.

Abstract-Design of a GaP/Si composite waveguide for CW terahertz wave generation via difference frequency mixing

Kyosuke Saito, Tadao Tanabe, and Yutaka Oyama   »View Author Affiliations

http://www.opticsinfobase.org/ao/abstract.cfm?uri=ao-53-17-3587

Applied Optics, Vol. 53, Issue 17, pp. 3587-3592 (2014)
http://dx.doi.org/10.1364/AO.53.003587

We design a GaP/Si composite waveguide to achieve efficient terahertz (THz) wave generation under collinear phase-matched difference frequency mixing (DFM) between near-infrared light sources. This waveguide structure provides a strong mode confinement of both near-infrared sources and THz wave, resulting in an efficient mode overlapping. The numerical results show that the waveguide can produce guided THz wave (5.93 THz) with a power conversion efficiency of6.6×10−4  W−1. This value is larger than previously obtained with the bulk GaP crystal: 0.5×10−9  W−1 [J. Lightwave Technol. 27, 3057 (2009)]. Our proposed composite waveguide can be achieved by bridging the telecom wavelength and THz frequency region.

© 2014 Optical Society of America