Understanding wide field-of-view flat lenses: an analytical solution [Invited]

Abstract

Wide field-of-view (FOV) optics are widely used in various imaging, display, and sensing applications. Conventional wide FOV optics rely on complicated lens assembly comprising multiple elements to suppress coma and other Seidel aberrations. The emergence of flat optics exemplified by metasurfaces and diffractive optical elements (DOEs) offers a promising route to expand the FOV without escalating complexity of optical systems. To date, design of large FOV flat lenses has been relying upon iterative numerical optimization. Here, we derive, for the first time, to the best of our knowledge, an analytical solution to enable computationally efficient design of flat lenses with an ultra-wide FOV approaching 180°. This analytical theory further provides critical insights into working principles and otherwise non-intuitive design trade-offs of wide FOV optics.

Metasurface optics enabled computational sensing

“…However, the phase mask optimization is a time-consuming process which requires manual tuning and empirical choice of the parameters. Here, we use direct search (DS) algorithm [37][38][39][40][41][42][43] to optimize the DH phase mask. The figure-of-merit is defined as the sum of the lower intensities between the two foci over a discrete set of sampling rotation angles, minus variation of the intensity between different angles.…”

Wide field-of-view long-wave infrared metalenses

“…[20][21][22][23][24] Here, we utilize a single-element fisheye metalens architecture by combining a single-layer metasurface with an optical aperture. [25][26][27][28] It features an easy-to-fabricate configuration and planar focal plane. The optimum phase profile of the WFOV flat lens is derived through an analytical solution, 25 which is able to explore the full design parameter space without intensive computational load.…”

“…[25][26][27][28] It features an easy-to-fabricate configuration and planar focal plane. The optimum phase profile of the WFOV flat lens is derived through an analytical solution, 25 which is able to explore the full design parameter space without intensive computational load.…”

Thickness bound for nonlocal wide-field-of-view metalenses

“…To achieve wide FOV with diffraction-limited focusing, one can use metasurface doublets [25][26][27][28][29][30][31][32] or triplets 33 analogous to conventional multi-lens systems, add an aperture stop so incident light from different angles reach different regions of the metasurface [34][35][36][37][38][39] , or use inversedesigned multi-layer structures 40,41 ; these approaches are schematically illustrated in Fig. 1b, c.…”

“…Shrestha et al 51 and Presutti et al 52 related the maximal operational bandwidth of achromatic metalenses to the numerical aperture (NA), lens diameter, and thickness, which was generalized to wide-FOV operation by Shastri et al 53 and diffractive lenses by Engelberg et al 54 . Shastri et al investigated the relation between absorber efficiency and its omnidirectionality 55 39 , and Martins et al studied the trade-off between the resolution and FOV for doublet-based metalenses 32 . Each of these studies concerns one specific type of design.…”