Abstract:
In this research, the main focus is to develop Photonic Crystal Fiber (PCF) structures which exhibit ultra-low loss in THz wave propagation. Several researchers recently proposed different types of PCF geometry to minimize the losses. These proposed PCF structure depicted a moderate effective material loss from 0.029 cm-1 to 0.086 cm-1. There are several ways to minimize the losses such as core cladding geometry selection, air holes size optimization, air holes position, core radius, material selections etc. In this context a sectored cladding and square core structured PCF is designed for THz wave propagation and a hexagonal asymmetrical slotted porous core PCF geometry is proposed for polarization maintaining fiber in the THz regime.
The proposed circular sectored cladding and square core PCF design exhibits extremely low effective material loss (EML) of 0.009 cm-1 at optimum design parameters. However, it shows very large effective area and a high core power fraction in the THz frequency range. Hence this PCF structure can‟t meet the requirements of polarization maintaining fiber characteristics. Thus, an asymmetrical hexagonal slotted porous core PCF geometry is developed for polarization maintaining fiber characteristics which exhibits significant differences of refractive index in x and y polarization mode with a low EML of 0.015 cm-1and confinement loss of 0.0001 cm-1.
Presently PCF in the THz regime has gained popularity for chemical sensing applications. In general presented PCF exhibits maximums 90% sensitivity but still have lots of possibilities to improve the sensitivity. In this context hollow core fiber geometry is proposed for chemical sensing application. Hollow core fiber has greater analyte volume inside the core area, thus facilitating tight confinement that increases the sensitivity. This proposed PCF based sensor shows relative sensitivity very close to 100%, along with also shows very low EML of 4×10-3 cm-1 and negligible confinement loss. Interestingly the asymmetrical hexagonal slotted porous core PCF also exhibits sensitivity in the range of 68% to 94% which is comparable to that of existing structures for chemical sensing applications.
The performances of the proposed designs are also compared with those of state-of-the-art works. In general all the three designs exhibit a superior EML and sensitivity while facilitating ease of fabrication.
