Compact Photonic Crystal Fiber for Sensing Applications in the THz Regime

Abstract

AbstractThis chapter deals with terahertz (THz) sensor-based photonic crystal fiber (PCF) and its various useful applications in multiple domain such as chemical, gas, biomedical and environmental. In the visible and infrared areas of optical fiber sensor, the probing length of evanescent fields is sub wavelength, limiting its use for identification of bigger targets. Because THz signal has a higher wavelength and THz sensors could be fit for a variety of sensing applications. The THz radiation (0.1–10 THz) has a huge potential in a wide application domain like sensing, biomedical industry, astronomy, medical imaging, security, agricultural industry, etc. Due to their adaptive design flexibility and wide range of applications in the THz spectrum, PCFs have emerged as an appealing alternative to electronics technology in this regard. Owing to the recent revolution in biomedical industry, nowadays the scientists are more focused in designing optical biosensors, where the PCF-based sensors are the most researched devices and almost controlling the modern photonic industry. PCFs-based sensors in THz regime have been extensively investigated owing to their high birefringence, ultra-high sensitivity, effective mode area, ultra-high sensitivity and minimum loss. With the advancement in technology, different hollow core and porous core PCFs have been successfully fabricated with extensive analysis of propagation characteristics and tested for various sensing applications like blood, gas, salinity, DNA, alcohol, liquid, food, hormones, enzymes, cells, urine, glucose, chemicals, etc. From the numerical analysis, the suitable background materials such as Teflon, Zeonex, PMMA and TOPAS are used for operation in THz region due to their high transparency in THz spectrum and feeble loss coefficient. Recently, a more effective THz sensors are envisaged through plasmonic principle by integrating novel metals and transition-metal dichalcogenide (TMDC) materials in the design of PCFs. In this chapter, different geometries of PCF and their light guiding mechanisms are thoroughly studied. Moreover, an extensive investigation is carried out vis-à-vis numerous sensing applications of PCF in THz spectrum, and their sensing performances are compared.KeywordsPhotonic crystal fiberTHz sensorChemical sensor and Biosensor