A Highly Birefringent Photonic Crystal Fiber for Terahertz Spectroscopic Chemical Sensing

Tianyu Yang,Shidi Liu,Yunjie Shi,Liang Zhang,Yuming Dong

doi:10.3390/s21051799

Abstract

A photonic crystal fiber (PCF) with high relative sensitivity was designed and investigated for the detection of chemical analytes in the terahertz (THz) regime. To ease the complexity, an extremely simple cladding employing four struts is adopted, which forms a rectangular shaped core area for filling with analytes. Results of enormous simulations indicate that a minimum 87.8% relative chemical sensitivity with low confinement and effective material absorption losses can be obtained for any kind of analyte, e.g., HCN (1.26), water (1.33), ethanol (1.35), KCN (1.41), or cocaine (1.50), whose refractive index falls in the range of 1.2 to 1.5. Besides, the PCF can also achieve high birefringence (∼0.01), low and flat dispersion, a large effective modal area, and a large numerical aperture within the investigated frequency range from 0.5 to 1.5 THz. We believe that the proposed PCF can be applied to chemical sensing of liquid and THz systems requiring wide-band polarization-maintaining transmission and low attenuation.

Highlights

Mircostructured fibers (MFs) or photonic crystal fibers (PCFs) with air holes periodically arranged in the cross-section have attracted considerable attention in the last two decades due to their unusual design flexibility
Since the first PCF was reported in the end of the last century [4], attention was mainly focused on its optical applications
A new rectangular suspended-core PCF with an extremely simple core and cladding has been developed in the THz regime for liquid sensing

Summary

Introduction

Mircostructured fibers (MFs) or photonic crystal fibers (PCFs) with air holes periodically arranged in the cross-section have attracted considerable attention in the last two decades due to their unusual design flexibility. Since the first PCF was reported in the end of the last century [4], attention was mainly focused on its optical applications. The THz band, which covers the spectral range from 0.1 THz to 10 THz, could effectively alleviate the spectrum scarcity and capacity limitations of current systems. Unlike the microwave and optical bands, many features of the THz band are only being studied. One important reason that the THz band was not intensively investigated before is the high transmission loss by the moisture in air during its propagation. To alleviate the loss issue of THz communications, THz optical PCFs [5] have been used as waveguides in many applications, such as THz antennas [6] and polarization-maintaining THz systems [7]

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