We report a miniature hydrogen sensor that consists of a subwavelength diameter tapered optical fiber coated with an ultra thin palladium film. The optical properties of the palladium layer changes when the device is exposed to hydrogen. Consequently, the absorption of the evanescent waves also changes. The sensor was tested in a simple light transmission measurement setup that consisted of a 1550 nm laser diode and a photodetector. Our sensor is much smaller and faster than other optical hydrogen sensors reported so far. The sensor proposed here is suitable for detecting low concentrations of hydrogen at normal conditions.

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We report the fabrication and modeling of single-mode tapered optical fiber sensors. The fabrication technique consist of stretching a section of fiber with an oscillating flame torch. Such a process allows controllable fabrication of lossless tapered fibers with a uniform waist. The sensor transmittance is modeled with a simple ray optics approach. In the model, all the taper parameters are taken into account. Our results indicate that sensor sensitivity can be adjusted with the taper waist diameter. As an example a gold-coated tapered fiber is theoretically and experimentally analyzed.

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