Subdiffraction Focusing With A Long Focal Length Using A Terahertz-Wave Super-Oscillatory Lens

This Letter describes a super-oscillatory lens (SOL), with concentric ring-type metallic slits photolithographically fabricated on a glass substrate, that can function at subterahertz frequencies. The SOL has been investigated both experimentally and theoretically and demonstrates a spatial resolution of 1.5 mm (0.5 lambda), which is 0.45 times the diffraction limit, with a focal length of 75 mm (25 lambda) at 100 GHz (lambda = 3 mm). Furthermore, the depth of focus of the lens was measured to be 47 mm, which is 10.8 times larger than that of a conventional lens. This type of SOL, with subdiffraction focusing, is thus highly effective for use in industrial inspections with millimeter and terahertz waves. (C) 2021 Optical Society of America