Endoscopic optical imaging has the potential for providing critical clinical imaging feedback for a variety of lumi- nal organs, with notable applications identified in the cardiovascular, pulmonary, and gastrointestinal systems. A significant drawback of optical endoscopes with side-viewing distal optics is that they must be mechanically rotated in order to obtain a complete 360 degree picture of the organ being imaged. Arguably, this fact serves as the biggest impediment to realizing the full potential of endoscopic optical imaging: in addition to the com- promises one has to make in terms of distal optics, the mechanical rotation of the imaging endoscope entails serious drawbacks for researchers, clinicians, and commercial enterprises engaged in the imaging modality. Though difficult to manufacture and subject to far too frequent degradation and outright breakage, perhaps the biggest issues with mechanically rotated imaging endoscopes are the hard limit mechanical rotation imposes on image acquisition speed and the difficulty or inability to integrate certain highly valuable functional and contrast enhancing techniques such as elastography and polarimetry. These facts point to an outdated, stagnant design that is deeply in need of reinvention. The goal of the proposed research is to develop a novel optical endoscope that does not need to be rotated to perform 360 degree imaging. The practical advantages of our proposed en- doscope include increased clinical utility and appeal, widely broadened research possibilities, and the establish- ment of a clear direction for future optical endoscope research. The aims for this proposal are as follows. Specific Aim 1 focuses on the design and development of the novel metasurface that will enable passive mod- ulation of the transmitted beam direction. The metasurface will encode in its nanostructures a large number of independent holograms that are each individually selective for specific beam parameters and are engineered to transmit the beam at a unique angle along a complete circle. The metasurface will additionally encode a holo- graphic lens, eliminating the need for bulk lenses in the distal optical assembly. Characterization of the fabri- cated metasurface will focus on aspects such as beam profile and spot size, selectivity, and efficiency. Specific Aim 2 incorporates the metasurface from Aim 1 into a fiber optic endoscope design that utilizes a 360 degree reflecting element for redirecting the holographically-selected beam along a direction nearly perpendic- ular to the endoscope axis for luminal imaging. Optical characterization will be performed similarly to as in Aim 1, accounting for the combined result of the metasurface and reflector. These tests will be complemented by ex vivo imaging of airway segments to assess imaging performance.

Screening, diagnosis, and monitoring of disease in internal organs is challenging as tissues are not readily ac- cessible. Endoscopic optical imaging possesses the greatest potential for addressing this problem, but its util- ity is significantly impaired by outdated, problematic endoscope design. The successful development of our metasurface-enhanced endoscope will bring dramatic improvements to the technology while also setting a clear course for future technological innovations.