Fabricating optical fibre-top cantilevers for temperature sensing

Abstract

In this paper, we propose techniques to fabricate micro-cantilevers onto the end of standard single mode optical fibres using a combination of picosecond laser machining and focused ion beam milling techniques and demonstrate their use as temperature sensors. Using this approach the cantilever can be pre-aligned with the core of the fibre during fabrication, therefore offering a stable and straightforward means of optically addressing the cantilever. The cantilever is designed to measure deflection over a range of 10 µm using a simple readout technique. A phase recovery algorithm is employed to reduce the interrogation error to around 2–3 nm. Finally, a temperature cycling experiment demonstrates that the cantilever could be used as a temperature sensor from room temperature to 500 °C with an average rms temperature error from 20 °C to 500 °C of ∼±1.4 °C.

Optical Fiber Probe Microcantilever Sensor Based on Fabry–Perot Interferometer

“…The ps-laser direct machining greatly reduces the processing time and has a good processing accuracy with respect to chemical etching methods. Exploiting the high machining speed of ps-laser direct machining and the excellent surface roughness of FIB milling, Li et al [ 56 ] proposed a microcantilever temperature sensor with a high sensitivity of 40.2 nm/°C in the range from room temperature to 500 °C. Similar to [ 55 ], a fiber-top microcantilever that was 110 μm long, 18 μm wide and 8 μm thick was first machined by ps-laser machining.…”

A review of focused ion beam applications in optical fibers

“…Free hanging cantilevers have found broad applications in a variety of research fields such as position sensing, topography measurements, and biochemical manipulations [122,180,181]. FIB machining has been effectively employed to integrate the cantilevers onto the tip of an optical fiber for creating miniaturized fiber sensors [122][123][124][125][126][127][128][129][130]. The fiber-top cantilever is usually positioned to cover the core area of an optical fiber, and therefore the laser light coupled to the core is partially reflected back into the fiber by the cantilever.…”

“…Furthermore, Li et al fabricated various micro-cantilevers onto the top of an optical fiber as temperature [128] and pH [129] sensors. In this case, a picosecond (ps) pulsed laser was first used to remove large volumes of material, and thus to reduce the total FIB fabrication time.…”

A high-temperature parallel double-Fabry–Pérot interferometer sensor based on the Vernier effect

“…Common techniques for fabricating FPIs involve chemical etching [13], laser micromachining [14,15], vacuum RFmagnetron sputtering diaphragms [16] and fused splicing [17]. However, chemical etching with hydrofluoric acid can be dangerous, and it is hard to control the etching rate precisely.…”