Analysis of Dielectric Waveguide Grating and Fabry–Perot Modes in Elastic Grating in Optical Detection of Ultrasound

In our previous work, we have demonstrated that dielectric elastic grating can support Fabry–Perot modes and provide embedded optical interferometry to measure ultrasonic pressure. The inside the an enhancement in sensitivity figure of merit compared thin film-based structures. Here, this paper, propose a theoretical framework explain also supports waveguide mode, which parameters control excitation two modes. properties modes, including coupling conditions loss mechanisms, are discussed. proposed has period micron scale, is shorter than wavelength incident ultrasound leading scattering. gap regions allow thickness be compressed by coupled surface acoustic wave mode. compression measured using interferometer through one guided narrow bandpass filter enabling ultrasensitive mode sense changes displacement. This mechanical gives rise broader detectable pressure range detection; enhanced 2.7 times 23 times, respectively, conventional