Real-time resilient focusing through a bending multimode fiber.

Area of Science:

• Optics and Photonics
• Biomedical Engineering
• Sensing Technologies

Background:

• Multimode optical fibers offer small size and flexibility for biomedical and sensing uses.
• Mode dispersion and coupling in these fibers disrupt light focusing and imaging.
• Existing methods struggle to maintain focus under dynamic conditions like bending.

Purpose of the Study:

• To develop a fast and effective method for re-focusing light transmitted through multimode optical fibers.
• To overcome the limitations of mode interference caused by fiber perturbations.
• To enable stable light focusing for advanced endoscopic and energy delivery applications.

Main Methods:

• Utilized a digital micro-mirror device (DMD) controlled by a field-programmable gate array (FPGA).
• Projected binary-amplitude computer-generated holograms to measure the fiber's transmission matrix.
• Implemented a system capable of re-focusing light within 37 milliseconds.

Main Results:

• Achieved light re-focusing in 37ms, an order of magnitude faster than prior methods.
• Maintained a stable focus spot despite significant fiber bending.
• Demonstrated a two-orders-of-magnitude enhancement in focus spot intensity relative to background.

Conclusions:

• The developed system enables rapid and stable light focusing through multimode optical fibers.
• This advancement significantly expands the potential of multimode fibers for real-time endoscopic imaging and targeted energy delivery.
• The technique overcomes critical challenges in optical wavefront shaping for dynamic environments.