Broadband imaging with one planar diffractive lens

Abstract

We demonstrate imaging over the visible band using a single planar diffractive lens. This is enabled via multi-level diffractive optics that is designed to focus over a broad wavelength range, which we refer to as an achromatic diffractive lens (ADL). We designed, fabricated and characterized two ADLs with numerical apertures of 0.05 and 0.18. Diffraction-limited focusing is demonstrated for the NA = 0.05 lens with measured focusing efficiency of over 40% across the entire visible spectrum (450 nm to 750 nm). We characterized the lenses with a monochromatic and a color CMOS sensor, and demonstrated video imaging under natural sunlight and other broadband illumination conditions. We use rigorous electromagnetic simulations to emphasize that ADLs can achieve high NA (0.9) and large operating bandwidth (300 nm in the visible spectrum), a combination of metrics that have so far eluded other flat-lens technologies such as metalenses. These planar diffractive lenses can be cost-effectively manufactured over large areas and thereby, can enable the wide adoption of flat, low-cost lenses for a variety of imaging applications.

Multi-plane, multi-band image projection via broadband diffractive optics

“…Previously, we have shown broadband diffractive lenses for imaging [11][12][13][14][15][16]. In analogy with that work, here we show that the BDOE is equivalent to a lens whose point-spread function (PSF) is structured in the form of the desired image.…”

Near-IR wide-field-of-view Huygens metalens for outdoor imaging applications

“…In Refs. [35,36], it is argued that the only advantage of a metasurface over a diffractive surface is if one wants to manipulate the polarization. This would mean that conventional metalenses, which manipulate only the phase of the light, are redundant.…”

High-NA achromatic metalenses by inverse design

“…To fully explore the design space and the tradeoffs associated with numerical aperture, bandwidth, and efficiency, we primarily design two-dimensional dielectric profiles, while demonstrating that the methods scale to fully threedimensional films. We make no periodic / unit-cell approximations, and indeed the designs that we discover often show rapidly varying spatial profiles; to ensure feasible computation times, we design devices in the 10- [8,9,21] with similar bandwidths, which operate only in the low-NA regime.…”