Abstract
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 ($\lambda =3\; {\rm mm}$). 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.
© 2021 Optical Society of America
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