Abstract:
Terahertz radiation occupies a middle ground between microwaves and infrared light waves known as the terahertz gap, where technology for its generation and manipulation is in its infancy. The frequency band of 0.1-10 THz, known as THz band has brought potential applications in many important fields. For wave propagation THz systems use free space as medium. But in free space waves face many difficulties which is very big issue for wave propagation. So, we have to use guided transmission instead of unguided transmission.
In the meantime, many guided transmission lines have many kinds of deprivation such as Effective Material Loss (EML), Confinement Loss, Bending Loss, Dispersion Loss, Power Fraction issue etc.
A highly sensitive porous core – photonic crystal fiber (PC-PCF) has been designed and analyzed for remote detection of chemical analytes in terahertz frequency range. The PC-PCF has been modelled using rectangular structured air holes in the core with square structured cladding. The full Vectorial finite Element Method (FEM) has been used to tune the geometrical parameters also to characterize the fiber.
At 1.8 THz, 37.3 µm slotted hole width and x-polarization mode the relative sensitivity for water, ethanol and benzene are 93.68%, 94.25%, and 94.43% respectively. The relative sensitivity obtained for the y polarization for water, ethanol and benzene are 94.4%, 94.92%, and 95.09% respectively. Effective Material Loss (EML) of water, ethanol benzene at frequency 1.8THz at x- polarization 0.06 cm-1, 0.055 cm-1, 0.054 cm-1 and at y-polarization 0.044 cm-1, 0.0411 cm-1, 0.054 cm-1 respectively. Effective area at optimum design parameters at x-polarization mode are 2.38E- 07m2, 2.25E-07m2 and 2.21E-07m2 at y-polarization mode are 2.38E-07m2, 2.25E-07m2 and 2.21E-07m2 for water, ethanol and benzene respectively.
Simulation results demonstrate a high relative chemical sensitivity for different analytes. Moreover, the PCF shows very low near zero Dispersion Variation, high Modal Effective Area, high Birefringence and high Numerical Aperture (NA). The practical implementation of the fiber is feasible with the present fabrication techniques. The optimized PCF with such attractive characteristic has commercial applications in remote chemical sensing as well as polarization preserving applications of terahertz waves.
Description:
Supervised by Prof. Dr. Mohammad Rakibul Islam
Professor,
Department of Electrical and Electronic Engineering, Islamic University of Technology (IUT), Board Bazar, Gazipur-1704