Abstract

We report on a new methodology for acoustic-impedance mapping based on a fiber-optic platform with high spatio-temporal resolution. TRapped Acoustic Phonon (TRAP) modes are excited by side irradiation of a focused laser beam via photoacoustic effect and detected by an implanted fiber laser by reading out its output frequency change. Local acoustic impedance of the surrounding medium can be derived from the acoustic spectrum of the TRAP modes. Impedance mapping can be achieved by scanning the excitation laser beam along the optical fiber. We demonstrate its validity by mapping the impedance across the interface between two miscible liquids in a microfluidic channel. Preliminary result presents a spatial resolution below 100 microns and a frame rate at 50 Hz.

© 2018 The Author(s)