Detection of circularly polarized light (CPL) has a high potential for development of various optical technologies. Conventional photodetectors require optical polarizers on the device to detect polarized light, and this causes substantial losses of sensitivity and resolution in light detection. Here, we report direct CPL detection by a photodiode using a helical one-dimensional (1D) structure of lead halide perovskites composed of naphthylethylamine-based chiral organic cations. The 1D structure with face-sharing (PbI₆)⁴⁻ octahedral chains whose helicity is largely affected by chiral cations shows intense circular dichroism (CD) signals over 3000 mdeg at 395 nm with the highly anisotropy factor (g_CD) of 0.04. This high CD enables photocurrent detection with effective discrimination between left-handed and right-handed CPLs. The CPL detector based on this 1D perovskite achieved the highest polarization discrimination ratio of 25.4, which largely surpasses the direct detecting CPL devices (<4) using chiral plasmonic metamaterials and organic materials.

Fresnel incoherent correlation holography (FINCH) was a milestone in incoherent holography. In this roadmap, two pathways, namely the development of FINCH and applications of FINCH explored by many prominent research groups, are discussed. The current state-of-the-art FINCH technology, challenges, and future perspectives of FINCH technology as recognized by a diverse group of researchers contributing to different facets of research in FINCH have been presented.

Near‐infrared (NIR) light emitting diodes (LEDs) with the emission wavelength over 900 nm are useful in a wide range of optical applications. Narrow bandgap NIR emitters have been widely investigated using organic compounds and colloidal quantum dots. However, intrinsically low charge mobility and luminescence efficiency of these materials limit improvement of the external quantum efficiency (EQE) of NIR LEDs, which is far from practical applications. Herein, a highly efficient NIR LED is demonstrated, which is based on an energy transfer from wide bandgap all inorganic perovskite (CsPbCl₃) to ytterbium ions (Yb³⁺) as an NIR emitter doped in the perovskite crystalline film. High mobility of electrically excited carriers in the perovskite crystalline film provides a long carrier diffusion and enhances radiative recombination of an emission center due to minimized charge trapping losses, resulting in high EQE value in LEDs. The NIR emission of Yb³⁺ at around 1000 nm is found to be sensitized by CsPbCl₃ thin film with a photoluminescence quantum yield over 60%. The LED based on Yb³⁺‐doped CsPbCl₃ film exhibits a high EQE of 5.9% with a peak wavelength of 984 nm, achieved by high carrier transporting ability and effective sensitized emission property in the solid‐film structure.

The structural and spectroscopic properties of a Cu(I) complex bearing a methylene-linked bis(N-heterocyclic carbene) ligand, [Cu₂(μ-Me-mbim)₂](PF₆)₂ were investigated. X-ray single crystal structure analysis revealed that the complex is binuclear similar to the corresponding silver(I) complex. In [Cu₂(μ-Me-mbim)₂](PF₆)₂, cation–π interaction between copper and the adjacent carbene carbon is observed. On the other hand, the copper–copper interaction is very weak in the crystal and almost negligible in solution. The absorption spectrum of [Cu₂(μ-Me-mbim)₂](PF₆)₂ in methanol shows a strong absorption band (ε = 23 000 dm³ mol⁻¹ cm⁻¹) and a weaker shoulder (ε = 6200 dm³ mol⁻¹ cm⁻¹) at 261 nm and 300 nm, respectively. From molecular orbital calculations using TD-DFT, these absorption bands are assigned to the metal-centered transitions with some contribution from the NHC orbitals. The powdered sample of [Cu₂(μ-Me-mbim)₂](PF₆)₂ shows bright blue-green phosphorescence with a high quantum yield (43%). The phosphorescence is of dual-emission character at room temperature with peak maxima at 374 nm and 482 nm whereas it changes to a single emission band centered around 500 nm at 77 K. Molecular orbital calculations indicate that the luminescence derives from the triplet MC and MLCT mixed excited states. A methanolic solution of [Cu₂(μ-Me-mbim)₂](PF₆)₂ shows yellow-green phosphorescence with a peak maximum at 542 nm. Unlike in the solid state, no dual-emission was observed. These results suggest that the dual emission is caused by differences in the contribution of metal–metal interactions at room temperature in the solid state. The differences in the absorption and emission properties between [Cu₂(μ-Me-mbim)₂](PF₆)₂ and the related Cu(I)–diphosphine complex, [Cu₂(μ-dcpm)₂](BF₄)₂ are discussed.