Acoustic vortex induced bubble cage: An on-demand light guide in turbid media

Guiding light in a scattering medium poses significant challenges, thus limiting the use of the optical device. We propose using an acoustic-vortex-induced bubble cage to confine light distribution within scattering media. The acoustic vortex creates a central null-pressure region surrounded by a high-pressure area, forming a ring-shaped bubble cage via cavitation. This structure acts as a light guide, confining photons within the central null during travel. Phantom experiments demonstrate a 50 % reduction in laser beam width and a 16.4 % ±1.0 % improvement in photon fluence. Effective photon confinement requires the laser beam width to match or be smaller than the central null width. It was also explored that a bubble cage acts as an optical lens, which can focus and steer photons. This technique offers reversible, on-demand, and non-contact photon manipulation in scattering mediums.