Focusing inside scattering media is a challenging task with a variety of applications in biomedicine. State of the art methods mostly require invasive feedback inside or behind the sample, limiting practical use. We present a technique for dynamic control and focusing inside scattering media that combines two powerful methods: optical coherence tomography (OCT) and wave-front shaping (WFS). We use OCT as a non-invasive feedback for WFS optimization of a separate, penetrating laser. Energy absorbed in the sample, creates thermal expansions that are used for the feedback mechanism. By maximizing thermal deformations within a selected focal region, we demonstrate enhanced focusing of light through scattering media beyond the ballistic regime and within the penetration range of OCT.
Tzang, Omer; Niv, Eyal; Caravaca-Aguirre, Antonio M; and Piestun, Rafael, "Thermal expansion feedback for wave-front shaping." (2017). Electrical, Computer & Energy Engineering Faculty Contributions. 10.