New optical pressure sensor based on the Fabry-Perot interferometer combined with mechanoluminescence diaphragm

This paper presents the preliminary study on new optical pressure sensor based on a Fabry-Perot interferometer (FPI) combined with mechnoluminescence diaphragm, which emits mechnoluminescent light when mechanical stimulation (in this study, alternating pressure) is applied. The FPI is a superposition of light reflected by two parallel reflective surfaces (i.e.: thin mirrors) and shows the wavelength change due to cavity changes. The optical device is often called an interferometer which the distance between the two surfaces (i. e, resonance length) changes. Fiber-optic Fabry-Perot (FOPF) pressure sensor uses this interference phenomenon by attaching a flexible diaphragm at the end surface of interferometer. When the pressure is applied to the diaphragm, distance between the two surfaces inside FOFP sensor can change. As a result, the external pressure can be detected either by measuring these interferences using a spectrometer or by capturing using a camera module with image processing. In this study, we explore the possibility of using ML diaphragm made of SrAl2O4:Eu2+,Dy3+ (SAO) powder as new diaphragm. ML diaphragm is thin composite and can emit green mechanoluminescent light (520nm) when the alternating pressure is applied. Spectral response turned out to be then changed and related to the magnitude of applied pressure.