Abstract-Terahertz Hollow Core Antiresonant Fiber with Metamaterial Cladding

Jakeya Sultana,  Md. Saiful Islam, Cristiano M. B. Cordeiro, Alex Dinovitser, Mayank Kaushik, Brian W.-H. Ng, Derek Abbott,

file:///C:/Users/Randy/Downloads/fibers-08-00014.pdf

A hollow core antiresonant photonic crystal fiber (HC-ARPCF) with metal inclusions is numerically analyzed for transmission of terahertz (THz) waves. The propagation of fundamental and higher order modes are investigated and the results are compared with conventional dielectric antiresonant (AR) fiber designs. Simulation results show that broadband terahertz radiation can be guided with six times lower loss in such hollow core fibers with metallic inclusions, compared to tube lattice fiber, covering a single mode bandwidth (BW) of 700 GHz. 

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-Terahertz detection of alcohol using a photonic crystal fiber sensor

Jakeya Sultana, Md. Saiful Islam, Kawsar Ahmed, Alex Dinovitser, Brian W.-H. Ng, and Derek Abbott

http://65.202.222.105/ao/abstract.cfm?uri=ao-57-10-2426

Ethanol is widely used in chemical industrial processes as well as in the food and beverage industry. Therefore, methods of detecting alcohol must be accurate, precise, and reliable. In this content, a novel Zeonex-based photonic crystal fiber (PCF) has been modeled and analyzed for ethanol detection in terahertz frequency range. A finite-element-method-based simulation of the PCF sensor shows a high relative sensitivity of 68.87% with negligible confinement loss of 7.79×10−12  cm−1$7.79\times {10}^{-12}{\mathrm{cm}}^{-1}$ at 1 THz frequency and 𝑥$x$-polarization mode. Moreover, the core power fraction, birefringence, effective material loss, dispersion, and numerical aperture are also determined in the terahertz frequency range. Owing to the simple fiber structure, existing fabrication methods are feasible. With the outstanding waveguiding properties, the proposed sensor can potentially be used in ethanol detection, as well as polarization-preserving applications of terahertz waves.

© 2018 Optical Society of America

Abstract-A Novel Approach for Spectroscopic Chemical Identification Using Photonic Crystal Fiber in the Terahertz Regime

 Md. Saiful Islam,  Jakeya Sultana,  Kawsar Ahmed,   Mohammad Rakibul Islam,  Alex Dinovitser,  Brian Wai-Him Ng, Derek Abbott,

http://ieeexplore.ieee.org/document/8115280/

A novel highly sensitive porous core-photonic crystal fiber (PC-PCF) has been designed and analyzed for detection of chemical analytes in the terahertz frequency range. The PC-PCF is designed using rectangular structured air holes in the core with a kagome structured cladding. The full vectorial finite-element method is used to tune the geometrical parameters and to characterize the fiber. Our results demonstrate a high relative chemical sensitivity with significantly lower confinement loss for different analytes. Moreover, the PCF shows near zero dispersion variation, high modal effective area, high birefringence, and high numerical aperture. The practical realization of the fiber is feasible with present fabrication techniques. Our optimized PCF has commercial applications in chemical sensing as well as applications in terahertz systems that require guided polarization preserving transmission.

Abstract-Zeonex-based asymmetrical terahertz photonic crystal fiber for multichannel communication and polarization maintaining applications

Md. Saiful Islam, Jakeya Sultana, Alex Dinovitser, Mohammad Faisal, Mohammad Rakibul Islam, Brian W.-H. Ng, and Derek Abbott

https://www.osapublishing.org/ao/abstract.cfm?uri=ao-57-4-666&origin=search

We report on the design, in-depth analysis, and characterization of a novel elliptical array shaped core rectangular shaped cladded photonic crystal fiber (PCF) for multichannel communication and polarization maintaining applications of terahertz waves. The asymmetrical structure of air holes in both core and cladding results in increased birefringence, while a compact geometry and different cladding air hole size makes the dispersion characteristic flat. The modal characteristics of the PCF are calculated using a finite element method. The simulated results show a near-zero dispersion flattened property of ±0.02  ps/THz/cm$\pm 0.02\mathrm{ps}/\mathrm{THz}/\mathrm{cm}$, high birefringence of 0.063, low effective material loss of 0.06  cm−1$0.06{\mathrm{cm}}^{-1}$, and negligible confinement loss of 5.45×10−13  cm−1$5.45\times {10}^{-13}{\mathrm{cm}}^{-1}$ in the terahertz frequency range. Additionally, the core power fraction, effective area, physical attributes, and potential fabrication possibilities of the fiber are discussed.

© 2018 Optical Society of America

Abstract-Terahertz time-domain spectroscopy of edible oils

Alex Dinovitser1, Dimitar G. Valchev1,2 and Derek Abbott1 

http://rsos.royalsocietypublishing.org/content/royopensci/4/6/170275.full.pdf

Chemical degradation of edible oils has been studied using conventional spectroscopic methods spanning the spectrum from ultraviolet to mid-IR. However, the possibility of morphological changes of oil molecules that can be detected at terahertz frequencies is beginning to receive some attention. Furthermore, the rapidly decreasing cost of this technology and its capability for convenient, in situ measurement of material properties, raises the possibility of monitoring oil during cooking and processing at production facilities, and more generally within the food industry. In this paper, we test the hypothesis that oil undergoes chemical and physical changes when heated above the smoke point, which can be detected in the 0.05–2 THz spectral range, measured using the conventional terahertz time-domain spectroscopy technique. The measurements demonstrate a null result in that there is no significant change in the spectra of terahertz optical parameters after heating above the smoke point for 5 min. 

Abstract-Terahertz Signal Classification Based on Geometric Algebra

Shengling Zhou, Dimitar G. Valchev,Alex Dinovitser
http://ieeexplore.ieee.org/document/7589042/

This paper presents an approach to classification of substances based on their terahertz spectra. We use geometric algebra to provide a concise mathematical means for attacking the classification problem in a coordinate-free form. For the first time, this allows us to perform classification independently of dispersion and, hence, independently of the transmission path length through the sample. Finally, we validate the approach with experimental data. In principle, the coordinate-free transformation can be extended to all types of pulsed signals, such as pulsed microwaves or even acoustic signals in the field of seismology. Our source code for classification based on geometric algebra is publicly available at: https://github.com/swuzhousl/Shengling-zhou/blob/geometric-algebra-classifier/GAclassifier/.