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Effect of the Pd-Au thin film deposition technique on optical fiber hydrogen sensor response time

2008; American Institute of Physics; Linguagem: Inglês

10.1063/1.2926836

1935-0465

Donato Luna-Moreno, David Monzón-Hernández, Dalia Martínez, Carlos Juárez Lora, Niklaus Ursus Wetter, Jaime Frejlich,

Advanced Fiber Optic Sensors

Optical absorption changes of the evanescent wave in an optical fiber were used to determine the hydrogen response characteristic of two different palladium‐gold thin films. The films were deposited over optical fibers using two different evaporation procedures. In the first, defined as co‐evaporation, gold and palladium were simultaneously evaporated using thermal and electron gun heating, respectively. In the other one, we called multilayer, alternating nano‐layers of gold and palladium were deposited over the fiber also using thermal and electron gun heating. Films were deposited over a core diameter mismatch optical fiber, that basically consist of a small piece of standard single‐mode fiber (SMF) spliced between two multimode fibers (MMFs). Due to core diameter mismatch the SMF cladding guides light producing an evanescent wave in the SMF cladding and outer medium interface. The sensitive Pd‐Au thin film was deposited over the single mode fiber section. When the device is exposed to hydrogen the palladium refractive index diminishes and causes attenuation changes of the evanescent fields. Adding gold to palladium allows the fabrication of fast, durable, and reliable sensors suitable for the detection of hydrogen concentration below the critical 4%.