Abstract-One-way edge modes in truncated semiconductor photonic crystal at terahertz frequencies

Lingjuan He, Linfang Shen, Xiaohua Deng, Kai Yuan,

https://iopscience.iop.org/article/10.1088/2040-8986/ab1bcd/pdf

Terahertz one-way edge modes in truncated photonic crystals (PhCs) are investigated theoretically. The PhC consists of a square array of air columns in semiconductor. By applying an external dc magnetic field in the PhC, a band gap is generated by lifting the degeneracy point of the lowest two bands. Based on this band gap, edge mode always exists in the truncated PhC for any boundary cutting, and it may propagate unidirectionally or bidirectionally, closely depending on the PhC boundary shape. It is shown that for one-way edge mode, the PhC boundary cutting has remarkable influence on the propagation length when the semiconductor loss is taken into account. A boundary structure is introduced into the PhC system for weakening the loss effect, and the propagation length of the one-way edge mode can be increased nearly by twice by optimizing the boundary parameters.

Abstract-A modified hexagonal photonic crystal fiber for terahertz applications

https://www.sciencedirect.com/science/article/pii/S0925346718301873


We present a Zeonex based highly birefringent and dispersion flattened porous core photonic crystal fiber (PC-PCF) for polarization preserving applications in the terahertz region. In order to facilitate birefringence, an array of elliptical shaped air holes surrounded by porous cladding is introduced. The porous cladding comprises circular air-holes in a modified hexagonal arrangement. The transmission characteristics of the proposed PCF are investigated using a full-vector finite element method with perfectly matched layer (PML) absorbing boundary conditions. Simulation results show a high birefringence of 0.086 and an ultra-flattened dispersion variation of 
$\pm 0.03$ ps/THz/cm at optimal design parameters. Besides, a number of other important wave-guiding properties including frequency dependence of the effective material loss (EML), confinement loss, and effective area are also investigated to assess the fiber’s effectiveness as a terahertz waveguide.

Abstract-Superconductor based ternary periodic multilayered structure as a single and multichanneled filter in the terahertz region

Nirmala Maria D’souza and Vincent Mathew

https://www.osapublishing.org/ao/abstract.cfm?uri=ao-56-24-6765&origin=search

A single as well as a multichanneled filter in the terahertz region has been proposed by designing a one-dimensional photonic crystal (PhC) structure using a high-temperature superconductor air-dielectric ternary periodic structure. The filter is designed without incorporating any defect, which has rarely been proposed in a ternary PhC structure. The theoretical study of transmittance was performed by applying the transfer matrix method. The transition from single channel to desired multichannel is achieved by adjusting the number of periods. Furthermore, the impact of the thicknesses and dielectric constants of the constituting layers was investigated. In addition to this, the tunability is achieved by the influence of temperature-dependent dielectric constant of the superconductor.

© 2017 Optical Society of America

Abstract-Enhanced terahertz fingerprint detection with ultrahigh sensitivity using the cavity defect modes

Xiaomei Shi,  Zhanghua Han, 

• • • 
      
  • https://www.nature.com/articles/s41598-017-13612-9
    We report a new scheme of realizing terahertz fingerprint detection with ultrahigh sensitivity. Instead of using the direct absorption of terahertz through a bare sample in the regular transmission scheme, a cavity mode resonating at the characteristic frequency of the sample is used and due to the high dependence of the cavity mode transmission on the material loss, an amplified transmission decaying is observed when the sample is loaded into the cavity. Furthermore, this scheme retains the feature of substance identification. A one-dimensional photonic crystal cavity is used as the example for the detection of α-lactose and an efficient detection of 10 nm α-lactose can be achieved, which corresponds to 1/57000 of the free space wavelength at the characteristic frequency of 0.529 THz, exhibiting a sensitivity over 400 times higher than the regular transmission method.

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

Abstract-Terahertz Sensor Using Photonic Crystal Cavity and Resonant Tunneling Diodes

Kazuma Okamoto, Kazuisao Tsuruda, Sebastian Diebold, Shintaro Hisatake, Masayuki Fujita Tadao,  Nagatsuma

https://link.springer.com/article/10.1007%2Fs10762-017-0391-0

In this paper, we report on a terahertz (THz) sensing system. Compared to previously reported systems, it has increased system sensitivity and reduced size. Both are achieved by using a photonic crystal (PC) cavity as a resonator and compact resonant tunneling diodes (RTDs) as signal source and as detector. The measured quality factor of the PC cavity is higher than 10,000, and its resonant frequency is 318 GHz. To demonstrate the operation of the refractive index sensing system, dielectric tapes of various thicknesses are attached to the PC cavity and the change in the resonator’s refractive index is measured. The figure of merit of refractive index sensing using the developed system is one order higher than that of previous studies, which used metallic metamaterial resonators. The frequency of the RTD-based source can be swept from 316 to 321 GHz by varying the RTD direct current voltage. This effect is used to realize a compact frequency tunable signal source. Measurements using a commercial signal source and detector are carried out to verify the accuracy of the data obtained using RTDs as a signal source and as a detector.