Combined Plasma-Based Fiber Etching and Diamond-Like Carbon Nanooverlay Deposition for Enhancing Sensitivity of Long-Period Gratings

Abstract

This paper presents an application of reactive ion etching followed by diamond-like carbon nanooverlay deposition using radio frequency plasma-enhanced chemical vapor deposition method for effective tuning of the refractive index (RI) sensitivity of long-period gratings (LPGs). Both etching and deposition take place within one process. Combination of both plasma-based processes allows for well-controlled tuning of the LPG sensorial response up to its operation at both dispersion turning point of higher order cladding modes and mode transition regime. As a result of the processing, the RI sensitivity has been enhanced up to over 12 000 nm/RIU per single resonance in narrow RI range (1.3344–1.3355 RIU) and over 2000 nm/RIU in broader RI range (1.34–1.356 RIU). Experimental results have been supported by numerical analyses that show capabilities for further significant improvement of both RI sensitivity and range of RI measured with the enhanced sensitivity.