title: Trench-embedding fiber taper sensor fabricated by a femtosecond laser for gas refractive index sensing.
abstract: A fiber in-line, multimode coupling interferometer with a trench-embedding, fiber taper probe is proposed and fabricated by femtosecond-laser-induced water breakdown. The reflection-type taper probe is used for gas refractive index (RI) detection from 1.0001143 to 1.0002187 and temperature sensing from 50°C to 500°C. The largest RI sensitivity of the taper probe embedded with a trench at a width of 18.4 μm is 669.502  nm/RIU for hybrid nitrogen and helium. Temperature sensitivity is 9.97  pm/°C and it shows good linearity through the whole testing range. The new-type multimode interferometer is appropriate for high-accuracy gas RI detection of micrometer-scale spaces and wide-range temperature compensation can be realized.
authors.forename: Zhitao
authors.initials: Z
authors.lastname: Cao
authors.forename: Lan
authors.initials: L
authors.lastname: Jiang
authors.forename: Sumei
authors.initials: S
authors.lastname: Wang
authors.forename: Peng
authors.initials: P
authors.lastname: Wang
authors.forename: Fei
authors.initials: F
authors.lastname: Zhang
authors.forename: Yongfeng
authors.initials: Y
authors.lastname: Lu