Focusing light inside dynamic scattering media with millisecond digital optical phase conjugation

Area of Science:

• Biomedical Optics
• Optical Engineering
• Biophysics

Background:

• Digital optical phase conjugation (DOPC) enables light focusing through scattering media.
• Existing DOPC methods are too slow for thick, living biological tissues and lack efficiency for focusing light inside tissues.

Purpose of the Study:

• To develop a faster and simpler DOPC system capable of focusing light through and inside scattering media, including thick and moving biological tissues.
• To overcome the speed limitations of previous wavefront shaping techniques for *in vivo* applications.

Main Methods:

• Utilized a ferroelectric liquid crystal spatial light modulator for a faster DOPC system.
• Employed ultrasound-guided DOPC combined with a binary wavefront measurement for focusing light inside scattering media.
• Controlled 2.6 × 10⁵ optical degrees of freedom for wavefront shaping.

Main Results:

• Achieved light focusing through 3 mm thick moving chicken tissue with a system latency of 3.0 ms.
• Demonstrated light focusing inside moving tissue with a latency of 6.0 ms, significantly faster than previous systems.
• The system's speed approaches tissue decorrelation rates, enabling real-time manipulation.

Conclusions:

• The developed DOPC system offers a significant advancement in speed and capability for optical focusing in scattering media.
• This breakthrough is crucial for advancing non-invasive *in vivo* deep-tissue optical imaging, manipulation, and therapy.
• The system's speed and ability to focus light internally represent a major step towards practical biomedical optical applications.