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Jumping spiders (Salticidae) rely on accurate depth perception for predation and navigation. They accomplish depth perception, despite their tiny brains, by using specialized optics. Each principal eye includes a multitiered retina that simultaneously receives multiple images with different amounts of defocus, and from these images, distance is decoded with relatively little computation. We introduce a compact depth sensor that is inspired by the jumping spider. It combines metalens optics, which modifies the phase of incident light at a subwavelength scale, with efficient computations to measure depth from image defocus. Instead of using a multitiered retina to transduce multiple simultaneous images, the sensor uses a metalens to split the light that passes through an aperture and concurrently form 2 differently defocused images at distinct regions of a single planar photosensor. We demonstrate a system that deploys a 3-mm-diameter metalens to measure depth over a 10-cm distance range, using fewer than 700 floating point operations per output pixel. Compared with previous passive depth sensors, our metalens depth sensor is compact, single-shot, and requires a small amount of computation. This integration of nanophotonics and efficient computation brings artificial depth sensing closer to being feasible on millimeter-scale, microwatts platforms such as microrobots and microsensormore »networks.« less

The cycle life of rechargeable lithium (Li)‐metal batteries is mainly restrained by dendrites growth on the Li‐metal anode and fast depletion of the electrolyte. Here, we report on a stable Li‐metal anode enabled by interconnected two‐dimensional (2D) arrays of niobium nitride (NbN) nanocrystals as the Li host, which exhibits a high Coulombic efficiency (>99 %) after 500 cycles. Combining theoretical and experimental analysis, it is inferred that this performance is due to the intrinsic properties of interconnected 2D arrays of NbN nanocrystals, such as thermodynamic stability against Li‐metal, high Li affinity, fast Li⁺migration, and Li⁺transport through the porous 2D nanosheets. Coupled with a lithium nickel–manganese–cobalt oxide cathode, full Li‐metal batteries were built, which showed high cycling stability under practical conditions – high areal cathode loading ≥4 mAh cm⁻², low negative/positive (N/P) capacity ratio of 3, and lean electrolyte weight to cathode capacity ratio of 3 g Ah⁻¹. Our results indicate that transition metal nitrides with a rationally designed structure may alleviate the challenges of developing dendrite‐free Li‐metal anodes.

The spectral resolution and range of conventional spectrometers are typically limited by optical aberrations of their focusing elements, mainly due to chromatically induced astigmatism and an intrinsically curved focal plane. Traditional approaches to overcome this challenge require additional optical components which introduce significant bulk and design complexity to the system and prevent easy integration with portable devices. Here a single planar off‐axis focusing metalens consisting of subwavelength TiO₂nanofins whose focal spots lie along a plane and undergo minimal focal spot broadening for almost 200 nm across the visible spectrum is demonstrated. This allows us to achieve a miniature aberration‐corrected spectrometer with nanometer spectral resolution, while having a beam propagation distance of only 4 cm to the camera plane. This is achieved by dispersion engineering: tailoring the phase, group delay (GD) and GD dispersion of the metalens. This approach is general and can also be used to introduce customized functionalities to the metalens such as a linear dispersion in the frequency domain with minimal additional overhead.