Abstract-Design of terahertz spectroscopy based optical sensor for chemical detection

• Shuvo Sen, 
• Kawsar Ahmed

https://link.springer.com/article/10.1007/s42452-019-1247-0

In this article, a new design of circular cladding with a rotated-hexacore in photonic crystal fiber (RH-CPCF) has been suggested for chemical sensing application in the THz regime. The five layers circular cladding and two layers rotated-hexacore in circular shape are designed here. All numerical results are obtained with a procedure of finite element method and perfectly match layered boundary condition in terahertz (THz) wave propagation. After the simulation result, the proposed RH-CPCF shows the high relative sensitivity is 76.44%, 77.16% and 73.20% for three chemicals such as Ethanol (n = 1.354), Benzene (n = 1.366) and Water (n = 1.330) at 1 THz. On the other hand, the low confinement losses are 2.33 × 10⁻⁰³ dB/m, 3.07 × 10⁻⁰⁶ dB/m and 2.84 × 10⁻⁰² dB/m for same in three chemicals at 1 THz. Moreover, effective area, effective mode index and total power fraction in core air holes are also briefly described here. In addition, this proposed circular photonic crystal fiber (RH-CPCF) can be used especially for chemical sensing in biomedical, industrial quality control, material research, micro-optics and many communication applications in THz technology.

Abstract-A Novel Hexahedron Photonic Crystal Fiber in Terahertz Propagation: Design and Analysis

Bikash Kumar Paul, Md. Ashraful Haque, Kawsar Ahmed, Shuvo Sen

https://www.mdpi.com/2304-6732/6/1/32

A novel hexahedron fiber has been proposed for biomedical imaging applications and efficient guiding of terahertz radiation. A finite element method (FEM) has been applied to investigate the guiding properties rigorously. All numerically computational investigated results for optimum parameters have revealed the high numerical aperture (NA) of 0.52, high core power fraction of 64%, near zero flattened dispersion of 0.5 ± 0.6 ps/THz/cm over the 0.8–1.4 THz band and low losses with 80% of the bulk absorption material loss. In addition, the V–parameter is also inspected for checking the proposed fiber modality. The proposed single-mode hexahedron photonic crystal fiber (PCF) can be highly applicable for convenient broadband transmission and numerous applications in THz technology.

Abstract-Ultrahigh birefringence, ultralow material loss porous core single-mode fiber for terahertz wave guidance

Kawsar Ahmed, Sawrab Chowdhury, Bikash Kumar Paul, Md. Shadidul Islam, Shuvo Sen, Md. Ibadul Islam, and Sayed Asaduzzaman

https://www.osapublishing.org/ao/abstract.cfm?uri=ao-56-12-3477&origin=search

In this paper, a novel polarization-maintaining single-mode photonic crystal fiber (PCF) has been suggested for terahertz (THz) transmission applications. The reported PCF has five layers of hexagonal cladding with two layers of porous core. The cladding and core territory of the PCF are constituted by circular and elliptical air cavities, accordingly acting as a dielectric medium. Different geometrical parameters of the proposed PCF including pitches and diameters of circular air holes with the major and minor axes of elliptical air cavities being varied with the optimized structure. Various effects on the proposed PCF such as eccentricity and porosity effects are also carefully investigated. The numerical process is investigated by one of the most popular methods, the finite element method (FEM). All numerical computational results have revealed the ultrahigh birefringence in the order of 1.19×10−02$1.19\times {10}^{-02}$ as well as the ultralow bulk absorption material loss of 0.0689  cm−1$0.0689{\mathrm{cm}}^{-1}$ at the 1 THz activation frequency. Besides, the V-parameter is also investigated for checking the proposed fiber modality. The proposed single-mode porous core hexagonal PCF is expected to be useful for convenient broadband transmission and numerous applications in the areas of THz technology.

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