- Open Access
Smectic bubble lasers for acoustic and pressure measurements in air and water
Phys. Rev. Applied 24, 034023 – Published 8 September, 2025
DOI: https://doi.org/10.1103/p1mc-1gp6
Abstract
Recently, we have demonstrated that dye-doped soap and smectic bubbles can be used as lasers. Here we investigated smectic bubble lasers for their potential to measure pressure changes in both air and water and as microphones. Smectic bubbles consist of a very thin smectic liquid crystal film. In contrast to ordinary soap bubbles, smectic bubbles are highly stable. When illuminated with a pump laser, they exhibit whispering gallery mode lasing with sharp, regularly spaced peaks in the emission spectrum. The bubbles enable extremely precise measurement of pressure changes based on wavelength shifts of the lasing peaks. We have demonstrated that smectic bubbles can be inflated under water and used as water pressure sensors. Additionally, we have used smectic bubble lasers in air as highly sensitive microphones to detect sound waves across different frequencies with advantages over conventional microphones. Their extremely thin walls result in negligible acoustic impedance. Furthermore, bubble size changes due to pressure variations depend only on bubble volume, eliminating the need for calibration and making performance independent of manufacturing precision or defects. This also leads to a linear amplitude response, and a flat frequency response over a wide range of frequencies. Unlike most microphones, bubble lasers can measure arbitrarily small frequencies down to static pressure, making them promising candidates for acoustic wave detection in various applications.
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