ph9b01703_si_001.pdf (366.77 kB)
Inverse Designed Metalenses with Extended Depth of Focus
journal contribution
posted on 2020-03-27, 13:03 authored by Elyas Bayati, Raphaël Pestourie, Shane Colburn, Zin Lin, Steven G. Johnson, Arka MajumdarExtended
depth of focus (EDOF) lenses are important for various
applications in computational imaging and microscopy. In addition
to enabling novel functionalities, EDOF lenses can alleviate the need
for stringent alignment requirements for imaging systems. Existing
designs, however, are often inefficient or produce an asymmetric point
spread function (PSF) that blurs images. Inverse design of nanophotonics,
including metasurfaces, has generated strong interest in recent years
owing to its potential for generating exotic and innovative optical
elements, which are generally difficult to design based on intuition
alone. Using adjoint optimization-based inverse electromagnetic design,
in this paper, we designed a cylindrical metasurface lens operating
at ∼625 nm with a depth of focus exceeding that of an ordinary
lens. We validated our design by nanofabrication and optical characterization
of silicon nitride metasurface lenses (with a lateral dimension of
66.66 μm) with three different focal lengths (66.66, 100, and
133.33 μm). The focusing efficiencies of the fabricated extended
depth of focus metasurface lenses are similar to those of traditional
metalenses.