H-type microchannel fiber humidity sensor by femtosecond laser-induced water breakdown

H-type microchannel in single-mode fiber was fabricated using femtosecond laser-induced water breakdown. The air can be brought into the fiber core position through H-type microchannel. As the relative humidity of the air changing from 25 to 60%, the transmission power of the fiber without coating any absorbent material on the fiber decreased more than -23 dB. The relative humidity sensitivity gets to as high as -1.00 dB/1%RH. The fiber with H-type microchannel structure can be used as humidity sensor as its high sensitivity, quick response, and low cost.