PFI-TT: Metasurface-Optical Fiber Endoscopy Probe for Advanced Imaging

The broader impact/commercial potential of this Partnerships for Innovation - Technology Translation (PFI-TT) project stems from the drastic reduction in size of an endoscope’s active imaging component to less than 200 microns: the size of a single human hair. Most current endoscope designs are larger than their target body region and must be forced through a narrow passage before imaging begins. The small footprint of the proposed Meta-Optical Fiber Endoscope (MOFE) device allows significantly less invasive treatment, reducing the likelihood of complications and the need for anesthesia during the procedure. The MOFE platform also targets other untapped biomedical imaging markets, such as cardiac, deep brain, and simultaneous multi-functional imaging. Additionally, these all-on-fiber structures offer greater potential for large scale and low-cost fabrication than current designs. Rather than requiring the assembly of many individual components, a complete MOFE probe can be realized in a single standard nanofabrication process, representing a substantial reduction in cost per device. The method employed to produce these probes can also be performed on a planarized fiber bundle, allowing hundreds or thousands of devices to be made in parallel. The proposed project will produce Meta-Optical Fiber Endoscope devices. By using flat optical metasurfaces, i.e. artificial sheet materials with sub-wavelength thickness, no wider than the fiber tip itself, it is possible to replace bulky glass optical imaging components (lenses, mirrors, prisms, etc.) with a device aspect ratio defined by the ultra-thin fiber components. This project will represent the first unification of optical metasurfaces—fabricated directly on-fiber—with other advanced imaging techniques, such as wavefront shaping in multimode fiber, optical coherence tomography, and multifunctional brain imaging, including beta testing of these novel devices. The titanium dioxide nanocylinder metasurfaces used in this project are highly efficient, i.e. over 90% transmission in the visible range, and able to tune the transmitted phase to have full wavefront control. The current prototype will include lensing to a controllable focal length, tunable beam steering, polarization insensitive functionality, and even multifunctionality combining any of the above simultaneously by integrating electrically tunable materials. This project will mark the first integration of high-index visible metasurfaces directly on the fiber endface. The metasurface’s tunability will lead to large field of view imaging, which is not available in existing endoscopy without bulky mechanical scanners. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.