Laser machining of sensing components on the end of optical fibres

Micro-cantilevers play a major role in sensing, especially since the invention of the atomic force microscope. Applications range from surface profiling to bio-medical sensing enabled through coating-activated cantilevers. Current readout methods are based on either optical deflection (of a laser beam reflected from the cantilever surface) or piezo-resistive response (of piezo-electric elements bonded to the cantilever surface). The first of these approaches requires significant space whilst the second is sensitive to electromagnetic effects. An alternative solution is to manufacture a cantilever onto the end of an optical fibre and use interferometry to monitor its deflection; in this paper we describe the development and application of a picosecond-laser machining process to fabricate such a device. The development of techniques to avoid cracking and debris re-deposition during this machining process is described, and a cantilever sensor with excellent optical performance is demonstrated and tested.