Exploiting complex media for biomedical applications

“Turbidity” caused by multiple light scattering distorts the propagation of waves and thus undermines optical imaging. For example, translucent biological tissues exhibiting optical turbidity have posed limitations on the imaging depth and energy transmission. However, recent advances in wavefront-sensing and wavefront-shaping technologies have opened the door to imaging and controlling wave propagation through a complex scattering medium. In this chapter, a novel method called turbid lens imaging (TLI) is introduced that records a transmission matrix (TM) of a scattering medium characterizing the input-output response of the medium. The knowledge of this TM allows one to find an incident wave out of the distorted transmitted wave. Therefore, it converts the highly complex medium into a useful imaging optics. By the use of the TM, the image distortion by a scattering medium can be eliminated and a clean object image can be retrieved as a result. The TLI was also adapted for imaging through a multimode optical fiber, which is a scattering medium, for the endomicroscopic imaging. In addition to imaging, the knowledge of TM was used to enhance light energy delivery through a highly scattering medium. This seemingly implausible task was made possible by coupling light into the resonance modes, called transmission eigenchannels, of the medium. With all these studies, the TLI will lead to great important applications in deep-tissue optical bio-imaging and disease treatment.