Generating acoustic signals of varying intensities via modulating continuous-wave lasers scanning in air

This report describes the generation of acoustic signals via laser-interference-based heating. Sound signals of varying intensities were generated by modulating two continuous-wave (CW) laser beams interfering in air. In this study, we discovered that the acoustic signals generated by two spatial-frequency-modulated CW lasers scanning in air are significantly stronger than those of a single CW laser. The intensity of photoacoustic signals is proportional to the diameter of the laser beam. Furthermore, our investigation showed that modulating the spatial frequency of the two laser beams can change the intensity of the acoustic signal. In addition, we found that the two beams stack better against a single beam when scanned vertically in three dimensions.