Time-reversed ultrasonically encoded optical focusing into scattering media

Area of Science:

• Biomedical optics
• Photonics
• Acousto-optics

Background:

• Light focusing is crucial for biomedical applications but is limited in scattering media.
• Existing methods to overcome diffusion limits lack a practical internal guide star.

Purpose of the Study:

• To propose and experimentally validate a novel method for light focusing inside scattering media.
• To overcome the diffusion limit in light delivery for biomedical applications.

Main Methods:

• Developed Time-Reversed Ultrasonically Encoded (TRUE) optical focusing.
• Used focused ultrasound to encode diffused light, creating a virtual internal guide star.
• Time-reversed the encoded light and transmitted it back to the ultrasonic focus.

Main Results:

• Demonstrated successful light delivery to a dynamically defined location within a scattering medium.
• TRUE optical focusing is unaffected by multiple light scattering.
• Achieved effective focusing in biological tissue due to lower ultrasonic scattering.

Conclusions:

• TRUE optical focusing provides a practical solution for deep-tissue light delivery.
• This technique overcomes the limitations of previous methods for light focusing in scattering media.
• TRUE optical focusing has potential applications in biomedical imaging, manipulation, and therapy, as well as colloidal optics.