Metalenses are nanostructured surfaces that mimic the functionality of optical elements. Many exciting demonstrations have already been made, for example, focusing into diffraction-limited spots or achromatic operation over a wide wavelength range. The key functionality that is yet missing, however, and that is most important for applications such as smartphones or virtual reality, is the ability to perform the imaging function with a single element over a wide field of view. Here, by relaxing the constraint on diffraction-limited resolution, we demonstrate the ability of single-layer metalenses to perform wide field of view (WFOV) imaging while maintaining high resolution suitable for most applications. We also discuss the WFOV physical properties and, in particular, we show that such a WFOV metalens mimics a spherical lens in the limit of infinite radius and infinite refractive index. Finally, we use Fourier analysis to explain the dependence of the FOV on the numerical aperture.

No abstract

This study aims to compare the efficacy of recombinant LH (rLH) supplementation for ovarian stimulation in gonadotrophin-releasing hormone-antagonist protocol for IVF/intracytoplasmic sperm injection cycles. Search strategies included online surveys of databases. The fixed effects model was used for odds ratio (OR) and effect size (weighted mean difference, WMD). Five trials fulfilled the inclusion criteria. When the meta-analysis was carried out, advantages were observed for the LH supplementation protocol with respect to higher serum oestradiol concentrations on the day of human chorionic gonadotrophin administration P < 0.0001; WMD: 514, 95% CI 368, 660) and higher number of mature oocytes (P = 0.0098; WMD: 0.88, 95% CI 0.21, 1.54). However, these differences were not observed in the total amount of recombinant FSH (rFSH) administered, days of stimulation, number of oocyets retrieved, the clinical pregnancy rate per oocyte retrieval, the implantation rate and miscarriage rate. This result demonstrates that the association of rLH with rFSH may prevent any decrease in oestradiol after antagonist administration and that a significantly higher number of mature oocytes was available for laboratory work. Nevertheless, it failed to show any statistically significant difference in clinically significant end-points in IVF (implantation and pregnancy rates). Additional randomized controlled trials are needed to confirm these results further.

Solar cells can strongly benefit from optical strategies capable of providing the desired broadband absorption of sunlight and consequent high conversion efficiency. While many diffractive light-trapping structures prove high absorption enhancements, their industrial application rather depends on simplicity concerning the integration to the solar cell concept and the process technology. Here, we show how simple grating lines can perform as well as advanced light-trapping designs. We use a shallow and periodic grating as the basic element of a quasi-random structure, which is highly suitable for industrial mass production. Its checkerboard arrangement breaks the mirror symmetry and is shown, for instance, to enhance the bulk current of a 1 µm slab of crystalline silicon by 125%. We explain its excellent performance by drawing a direct link between a structure's Fourier series and the implied photocurrent, derived from a large and diverse set of structures. Our design rule thus meets all relevant aspects of light-trapping for solar cells, clearing the way for simple, practical, and yet outstanding diffractive structures, with a potential impact beyond photonic applications. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Chromatic aberration is a major challenge faced by metalenses. Current methods to achieve broadband achromatic operation in metalenses usually suffer from limited size, numerical aperture, and working bandwidth due to the finite group delay of meta-atoms, thus restricting the range of practical applications. Multiwavelength achromatic metalenses can overcome those limitations, making it possible to realize larger numerical aperture (NA) and sizes simultaneously. However, they usually require three layers, which increases their fabrication complexity, and have only been demonstrated in small sizes, with low numerical aperture and modest efficiencies. Here, we demonstrate a 1 mm diameter red−green−blue achromatic metalens doublet with a designed NA of 0.8 and successfully apply the metalens in a digital imaging system. This work shows the potential of the doublet metasurfaces, extending their applications to digital imaging systems such as digital projectors, virtual reality glasses, high resolution microscopies, etc.