Refractive index sensor based on the nanofilm coated double cladding fiber

A refractive index sensor was proposed by using the nanofilm coated double cladding fiber (DCF). The DCF has a resonant filtering transmission spectrum due to the depressed refractive index inner cladding. To modify the resonant cladding mode of the DCF, a nanofilm with high refractive index was coated on the DCF by using atomic layer deposition technology. With the coating, a reorganization of cladding modes occurred, and the sensitivity of the DCF to surrounding refractive index was enhanced.