Lightweight, miniaturized optical imaging systems are vastly anticipated in these fields of aerospace exploration, industrial vision, consumer electronics, and medical imaging. However, conventional optical techniques are intricate to downscale as refractive lenses mostly rely on phase accumulation. Metalens, composed of subwavelength nanostructures that locally control light waves, offers a disruptive path for small-scale imaging systems. Recent advances in the design and nanofabrication of dielectric metalenses have led to some high-performance practical optical systems. This review outlines the exciting developments in the aforementioned area whilst highlighting the challenges of using dielectric metalenses to replace conventional optics in miniature optical systems. After a brief introduction to the fundamental physics of dielectric metalenses, the progress and challenges in terms of the typical performances are introduced. The supplementary discussion on the common challenges hindering further development is also presented, including the limitations of the conventional design methods, difficulties in scaling up, and device integration. Furthermore, the potential approaches to address the existing challenges are also deliberated.

Separating lights into different paths according to the polarization states while keeping their respective path's polarizations with high purification is keen for polarization multiplex in optical communications. Metallic nanowire gratings with multi-slits in a period are proposed to achieve polarized beam splitters (PBSs) in reflection and diffraction. The setting of multi-slits largely reduces the reflection of photons with a transverse magnetific field via the plasmonic waveguiding effect, which leads to highly polarized output lights with extinction ratio larger than 20 dB in each channel. The proposed reflection/diffraction PBSs enrich the approaches to control the polarization states with the advantages of wide incident angles and flexible beam splitting angles.

by the nanoarrays, which lead to extraordinary transmission through dielectric apertures below diffraction limits [13,14] ; 3) the plasmonic waveguiding of dielectric slits, which supports broadband polarized transmission of transverse magnetic (TM) light, while prohibits the propagation of transverse electric (TE) light. [15] Utilizing these mechanisms, the spectra of metallic nanoarray can be flexibly tuned to meet a variety of applications by engineering the metal thickness, profile of the unit cells, and the period. For example, by tailoring the profile of the nanounit cell to be asymmetric (linear, elliptical, or rectangular), polarization-dependent tunability can be imposed on the PSC to make integrated colorfilters and polarizers [16,17] for more compact and lower power-consumption liquid crystal displays (LCDs). Recently, actively tunable PSCs based on elastomeric substrates have been reported. By stretching the substrates, the pitch and therefore scattering colors of PSCs can be modified in a wide range, which makes them promising as novel display devices. [18] Besides the structure, the permittivity of the metal materials also strongly affects the spectrum characteristics. For instance, with small damping factors, gold and silver metallic nanoarrays have sharp surface plasmon resonance dips that are suitable for high figure of merit biosensing. [19] While aluminum (Al) has a large absolute value of complex permittivity and a large plasmon frequency to maintain plasmonic characteristics at wavelength down to ultraviolet, thus it is suitable to make broadband nanowire polarizers with high extinction ratio of TM over TE light in the transmission. In addition, Al has been widely used in the packaging, decoration, and laser hologram tags to enhance the reflection of diffraction gratings. [19][20][21] In this work, we propose a kind of transmission films of 1D metallic nanowire gratings (MNGs), which show polarization-dependent PSC over broad spectrum. Such films can be used as a new type of high-security and more recognizable anti-counterfeiting tags: polarized chromatic plasmonic tags (PCPTs). The physical mechanisms responsible for the polarization-dependent chromaticity are revealed, which are used in the device design. In Section 2, the fabrication of the films and tags is presented and their transmission spectra are described as a function of the MNG parameters and incident light parameters. In Section 3, a physical model is presented to describe the polarization-dependent chromaticity. The paper concludes with a summary in Section 4.A kind of polarized chromatic plasmonic film is proposed based on subwavelength grating structure, which enables "blue transmission" for the transverse electric light and "red transmission" for the transverse magnetic light. Metal-insulator-metal plasmonic waveguiding and metallic nanowire scattering are revealed to be responsible for the chromatic shift. Based upon the unique transmission spectrum characteristics of such films, polarized chromatic plasmonic tags (PCPTs) ca...

After the publication of this article 1 , it is brought to our attention that some mathematical expressions contained errors. Details are listed below.1. In the paragraph below Eq. ( 1) on p.3, the expression of the root mean square of WAF

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With the rapidly growing demand of wearable displays, flexible and stretchable fingerprint recognition modules are needed, as one of the crucial components in a display device. In this work, a grating coupler typed optical fingerprint capture(OFC) based on Polydimethylsiloxane(PDMS) substrate is presented in both simulation and experiment. The PDMS not only affords superior elasticity, but also facilitates the breaking of total internal reflection (TIR) of coupling lights to enhance the capture of fingerprint. Multilayer‐coated gratings are proposed to achieve high optical coupling efficiency of incident light. The proposed sensitive and flexible OFC system is of great promising in the practical applications.

Optical signals input from a light source are used as media for human‐machine interaction via the coupling of sub‐wavelength gratings covered on the display screen. The system includes a laser pen, a transparent sub‐wavelength grating optical film which couples the incident light into waveguide, and photodetectors set on the sides of the film to sense and decide the position of incident light. Furthermore, we can load the modulated signal on the incident light so that it can transfer data to the display device. The design provides a novel remote ‘touch’ interaction which is of great practical meaning in the large screen displays.