High-speed non-contact measurement of elasto-optic coefficient via laser-induced phonons

The elasto-optic coefficient, which describes the interaction of acoustic waves and light in a medium, allows a contrast mechanism in optomechanics. However, the non-contact measurement is a challenge, limiting the study of some materials such as liquids. We present a high-speed non-contact method based on laser-induced phonons. The elasto-optic coefficients of common liquids are measured with only 10 ms and an averaged relative standard deviation of 1.52%, complementing the rare liquid data. By deciphering Brillouin spectra, the elasto-optic coefficient and viscoelastic parameters can be obtained simultaneously, and the introduction of the elasto-optic coefficient makes the characterization more sensitive. Benefiting from spatially resolved measurement, the elasto-optic coefficient is mapped to provide another contrast mechanism for mechanical imaging and may prove useful to characterize biological cells and tissues.