Nano-optic endoscope for high-resolution optical coherence tomography in vivo

Acquisition of high-resolution images from within internal organs using endoscopic optical imaging has numerous clinical applications. However, difficulties associated with optical aberrations and the trade-off between transverse resolution and depth of focus significantly limit the scope of applications. Here, we integrate a metalens, with the ability to modify the phase of incident light at subwavelength level, into the design of an endoscopic optical coherence tomography catheter (termed nano-optic endoscope) to achieve near diffraction-limited imaging through negating non-chromatic aberrations. Remarkably, the tailored chromatic dispersion of the metalens in the context of spectral interferometry is utilized to maintain high-resolution imaging beyond the input field Rayleigh range, easing the trade-off between transverse resolution and depth of focus. We demonstrate endoscopic imaging in resected human lung specimens and in sheep airways in vivo. The combination of the superior resolution and higher imaging depth of focus of the nano-optic endoscope is likely to increase the clinical utility of endoscopic optical imaging.