Guiding light through absorbing structures using a linear transducer at diagnostic intensities

Optical visualization methods face the problem of shadowing of deep regions of samples by absorbing inclusions above them. Shadowing effectively blocks part of the sample, leading to the loss of crucial information, in particular in a biomedical imaging context. Via the piezooptic effect, ultrasound (US) can create lenses and waveguides suitable for pulsed illumination. In this work, we demonstrate the crucial information recovery from the shadowed regions using ultrasound-induced refractive index modification. We show the light guiding effect by measuring the intensity of light passing through the target onto the camera in transparent and low-scattering media with flat and bulk absorbers. In addition, by means of ultrasonic lightguiding, we demonstrate the ability to investigate the details of the absorbing structure. In particular, we acquire information about the position of the edge of the absorber which is blurred due to scattering. These findings have potential to enhance optical imaging techniques in complex absorbing environments, with possible applications in medical diagnostics.