Advanced Optical Materials最新文献

Quasi-2D lead-halide perovskites consist of conducting inorganic layers with tunable thickness (n) separated by large organic spacer cations. Typically, domains with different n and bandgaps are formed within a single film. Here, the crystallization of the films is tuned by mixing Dion-Jacobson (DJ) with Ruddlesden-Popper (RP) spacer cations. Compared to the quasi-2D perovskite film based on solely the DJ type spacer 1,4-phenylenedimethylammonium (PDMA), a film with less defects and more vertically aligned crystallization is achieved by addition of the RP type spacer propylammonium (PA). As the film structure plays an important role in the photophysics, time-resolved photoluminescence (TRPL) and femtosecond transient absorption (TA) are used to investigate the impact of mixing these spacer cations on the dynamics of hot carrier cooling, the occurrence and directionality of energy or electron transfer between the different domains, and the exciton and charge carrier dynamics. Exciton transfer from low-n to high-n domains occurs at a favorable faster rate for the PDMA-based film (0.0640 ps⁻¹) compared to the PA-based film (0.0365 ps⁻¹), while the mixed spacer film demonstrates intermediate behavior (0.0473 ps⁻¹). This study facilitates the design of advanced materials with optimized photophysical characteristics for a next generation of optoelectronic devices.

Quantitative Dynamic Structural Color

In article number 2401152 Nithesh Kumar, Judson D. Ryckman, and co-workers demonstrate an approach to overcome the limited sensitivity and often qualitative nature of structural-color-based sensors and indicators in a scheme referred to as ‘quantitative dynamic structural color’. As illustrated in this cover image, their scheme relies on a spectrally engineered mesoporous metamaterial combined with dichromatic laser illumination. The sensors achieve a well-defined and strongly enhanced color response toward refractometric stimuli including small molecules, vapors, and aerosols.

Defect Suppression in Te-Doped Cs₂ZrCl₆ Perovskite Nanoparticles

Lead-free Cs₂ZrCl₆:Te (CZCT) @ alkyl-terminated silica-oligomer (ASO) core/shell perovskite nanoparticles (PNCs) were designed and synthesized with the highest photoluminescence quantum yield (PLQY) of up to 96% and robust thermal tolerance simultaneously. The high PLQY was attributed to the comprehensive defect suppression through crystallization and surface control. The fabricated white light-emitting diodes based on the CZCT@ASO PNCs exhibit a color coordinate of (0.31, 0.33) and a color rendering index of 86. For further details, see article number 2303079 by Guangguang Huang, Shujie Wang, Zuliang Du, and co-workers from Henan University (the Iron Pagoda in the image representing its culture and spirit).

The design and experimental demonstration of double-step, 1D amorphous germanium grating structures supporting quasi bound-states-in-continuum (quasi-BIC) resonance at 3.2 µm wavelength and its application to third-order sum-frequency generation-based up-conversion are reported. Linear transmission measurements on the fabricated metasurface with loosely focussed excitation spanning 0–3° angles show very good agreement with ideal plane-wave excitation of the periodic photonic structure. TSFG measurements performed on the same structures with tightly focusing mid-infrared signal and pump beams using a reflective-type objective with 15–40° angular excitation show ≈375 times enhancement with significant blue-shift in the resonance feature by ≈300 nm. To understand this excitation angle dependence of the resonance characteristics, a generalized plane-wave expansion (PWE) model is developed by considering varying excitation angle plane-waves incident on the metasurface with a discretized angular spectrum representation used to coherently combine the resultant electric and magnetic fields to obtain the linear transmission characteristics and nonlinear TSFG spectra. The PWE method is found to be particularly effective in modeling linear and nonlinear responses under realistic illumination conditions while ensuring optimal utilization of computational resources. Good agreement is obtained between the PWE simulations, linear transmission, and nonlinear TSFG measurements by considering appropriate angular excitation.

A compact and responsive thermoelectric photodetector is introduced for the mid-infrared. By resonantly coupling mid-infrared light to a Sb₂Te₃-Bi₂Te₃ thermoelectric junction, a thermocouple is formed that is directly heated by narrow-band mid-infrared radiation. Near-perfect absorption is achieved at this hot junction through the resonantly enhanced coupling of light to free-electrons in the Bi₂Te₃ and Sb₂Te₃ materials. The fabricated devices operate at 3.6 µm and demonstrate a responsivity of 10.2 V W⁻¹, a specific detectivity of 4.6  × 10⁶ cm Hz^1/2 W⁻¹, and a bandwidth in the order of 1 kHz. The optimal detection wavelength can be spectrally tuned by changing the resonant cavity dimensions. This work shows a path toward miniaturized mid-infrared detectors and spectrometers with high sensitivity, responsivity, and bandwidth. Importantly, the device presented here is ideal for industrial production, which it is hoped will provide wider access to mid-infrared technologies for chemical sensing, medicine, and security.

Reconfigurable and tunable holograms hold significant practical value in the fields of anti-counterfeiting, optical security, and information display due to their ability to reprogram holographic patterns and create variable visual effects. However, current encryption techniques face challenges in achieving rapid encryption/decryption and ensuring consistent methods. In this study, a method for producing a reconfigurable encryption hologram utilizing the deformation and recovery properties of micropillars in response to liquid is demonstrated. Micron-scale micropillars are fabricated using femtosecond laser two-photon polymerization. By exploiting the rapid deformation and recovery capabilities of micropillars with specific pitches and aspect ratios in response to liquids, micropillar structures and holograms are combined to construct reconfigurable holograms. The encrypted pattern information in the reconfigurable holograms is only readable following immersion in alcohol and laser irradiation. The proposed method offers a facile, reversible, reusable, and practical solution for information encryption, with significant potential in anti-counterfeiting and optical security.