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Birefringence in azodye-doped polymethylmethacrylate and azodye-doped silica hybrid materials was induced by the two-photon excitation of a femtosecond laser. The growth and the relaxation characteristics of the photoinduced birefringence in the two types of material were investigated, and the probe transmittance for the induced birefringence was estimated to be 92%. Furthermore, an optical image storage based on this photoinduced birefringence was demonstrated. OCIS codes: 190.0190, 190.4400, 210.0210, 210.4810.

Visible light response is as important as energy band potential for photocatalytic water splitting. In this work, upconversion CeF3 nanoparticles are developed by O and N doping. The contents and species of O and N regulated by various temperatures act on the large-scale regulation of defects and band structures distinctly, which can suppress the recombination of photogenerated carriers. O,N-CeF3-160 nanoparticles establish the most suitable defects and electronic structure in all O,N-CeF3 nanoparticles. It exhibits the optimal oxygen evolution rates up to 1277 μmol g–1 h–1, whose apparent quantum yield (AQY) is up to 53.09% at 550 nm. The photoluminescence (PL) spectra and density of state (DOS) illustration elucidate the internal reason for the distinct photocatalysis activity. Defects are just as important as band structure in the modification of O,N-codoped CeF3 upconversion nanoparticles. This work provides the approach to regulate CeF3 upconversion materials to achieve better photoactivity under visible light. [ABSTRACT FROM AUTHOR]

Lead-halide perovskite nanocrystals (PeNCs) possess attractive linear and nonlinear optical properties. However, further adjusting their linear and nonlinear optical properties in a facile way remains a great challenge due to the inevitable instabilities. Herein, an effective host–guest system was successfully constructed by encapsulating PeNCs (CsPbX3 NCs) into a metal–organic framework (MOF), ZJU-28, via a sequential deposition method at ambient conditions. The accessible and charged frameworks of ZJU-28 facilitate the confinement growth of CsPbX3 NCs in the channels under a mild environment, and therefore facile halide-composition adjustment can be achieved by simply tuning the halide stoichiometry of CsX in a solution process, enabling wide-wavelength tunable one- and two-photon excited (1PE and 2PE) luminescence from 450 nm to 660 nm. Moreover, besides the confinement effect, effective separation, passivation and protection of CsPbX3 NCs are still achieved in ZJU-28⊃CsPbX3 crystals, resulting in a giant two-photon action cross-section which is comparable to that of colloidal CsPbX3 NCs densely capped by surface ligands, and significantly enhanced 1PE and 2PE photostability especially for the spectral stability of mixed-halide composites. These results will pave the way for the exploitation of highly stable and emission-tunable PeNCs composites in optoelectronic applications and even future integrated photonics. [ABSTRACT FROM AUTHOR]