Micro-machining of in-fibre 45° mirror optical fibre cantilever for dual-axis acceleration measurement

Abstract

Focused Ion Beam (FIB) machining has been demonstrated to be capable of fabricating nano and micro-structure elements. In this paper we demonstrate techniques to design and fabricate 45˚ micro-mirrors into the end of multi-core fibers (MCF) using FIB processing. The mirrors are finished by a two-step process: a scanning process which is used to make a rough cut followed by a polishing process to create an optical surface finish mirror. The machined 45˚mirrors can be accurately aligned with optical fiber cores, which avoid issues associated with the alignment of external turning mirror components. Proof-of-concept demonstration shows that the fabricated structure is capable of measuring two axes acceleration interferometrically with a linear acceleration range from 0.2 g to 4 g and an r.m.s. error of 0.03 g. Acceleration measurements of frequency response up to 700 Hz and cross-sensitivity of ~4.2% are demonstrated.