Light guiding with photoacoustically generated ultrasound

The guiding or focusing of light, crucial in many applications, often relies on bulky optical elements that are difficult to place in delicate mediums like biological tissue. In current systems, the optical components are located outside the sample, limiting possibilities due to geometric constraints. Scattering further complicates the control of light within non-homogeneous media, restricting operating beyond 1 mm of depth. A promising solution involves shaped ultrasound to induce refractive index gradients within the tissue, acting as embedded lenses or waveguides. However, existing methods rely on bulky ultrasonic transducers, introducing invasiveness and fixing the ultrasound geometry. The proposed approach uses photoacoustic generation of pressure waves within the medium, allowing light guiding without geometrical constraints. As it is successfully demonstrated in tissue phantoms with different scattering coefficients, this method offers a promising solution in conditions not feasable with traditional external optical elements.