Lossy mode resonance generation by using uncoated double cladding fiber

This work demonstrates as a novelty the generation of lossy mode resonances (LMR) in uncoated optical fiber with high index cladding (HIC), without use of an additional high refractive index thin film. For this purpose, commercially available double cladding fiber (DCF) having W-type refractive index profile was chosen for the purpose and spliced between two multi-mode fibers at the two ends. Here, the outer cladding of DCF fiber is having higher refractive index than the inner one which allows to generate LMR phenomena. The LMR phenomena can be tuned by changing the thickness of the outer cladding of DCF fiber e.g., by using chemical etching. The resulted fabricated device is characterized towards surrounding medium refractive index, demonstrating the sensitivity of about 1100 nm/RIU in RI range of 1.33-1.39, further making such devices suitable for bio-chemical sensing. This novel sensing becomes an alternative to other thin film based optical fiber sensors due to advantages in terms of simplicity, cost and stability.