High Resolution Brillouin Sensing of Micro-Scale Structures

Abstract

Brillouin distributed measurement techniques have been extensively developed for structural health monitoring using fibre optic nerve systems. The recent advancement in the spatial resolution capabilities of correlation-based Brillouin distributed technique have reached the sub-mm regime, making this approach a suitable candidate for monitoring and characterizing integrated photonic devices. The small dimension associated with the short length of these devices—on the order of the cm- and mm-scale—requires high sensitivity detection techniques and sub-mm spatial resolution. In this paper, we provide an overview of the different Brillouin sensing techniques in various micro-scale structures such as photonic crystal fibres, microfibres, and on-chip waveguides. We show how Brillouin sensing is capable of detecting fine transverse geometrical features with the sensitivity of a few nm and also extremely small longitudinal features on the order of a few hundreds of μ m . We focus on the technique of Brillouin optical correlation domain analysis (BOCDA), which enables such high spatial resolution for mapping the opto-acoustic responses of micro-scale waveguides.

Brillouin scattering—theory and experiment: tutorial

“…The correlation peak can be swept through the device and therefore a distributed Brillouin measurement can be achieved. Such high spatial resolution can give insight into the Brillouin response of short integrated waveguides [69]. Note that all these techniques rely on backward Brillouin scattering.…”

Probing micron-scale distributed contortions via a twisted multicore optical fiber

“…Typically, the former utilizes the principles of microscopy or imaging, 15,23,24 whereas the latter leverages the change in properties of the EM radiation while being transported through a waveguide that is deformed or bent when contiguous to the contortions. 8,10,11,25,26 The drawback of free-space irradiation-based sensors is that they can be rendered inadequate when a direct line-of-sight is unavailable or the EM exposure and EM interference pose a threat. Among the EM waveguide designs, optical fibers represent a highly attractive platform for developing contortion sensors, owing to a variety of available design parameters and configurations, a shielded transport of EM radiation, and an opportunity for ultralong length distributed sensing operation.…”

“…[27][28][29] The optical-fiber contortion sensors may employ gratings, [29][30][31][32][33][34][35][36][37][38][39] modal interference, [40][41][42][43][44][45] radiationlosses, [46][47][48][49][50][51][52] or nonlinear effects to detect and measure the probed contortions. 10,26,53,54 In the past, optical fiber sensors for a distributed measurement of such parameters as temperature, pressure, strain, etc., have been extensively studied. The measurement of a bend radius and curvature as well as shape and position using optical fiber sensors has also been demonstrated previously.…”