Metal halide perovskites have become one of the most competitive new-generation optoelectronic materials due to their excellent optoelectronic properties. Vacuum evaporation can produce high-purity and large-area films, leading to the wide application of this method in the semiconductor industry and optoelectronics field. However, the electroluminescent performance of vacuum-evaporated perovskite light-emitting diodes (PeLEDs) still lags behind those counterparts fabricated by solution methods. Herein, based on vacuum evaporation, 3D perovskite films are obtained by three-source co-evaporation. Considering the unique quantum well structure of quasi-2D perovskite can significantly enhance the exciton binding energy and improve the radiative recombination rate, leading to a high photoluminescence quantum yield (PLQY). Subsequently, the highly stable and low-defect-density quasi-2D perovskite is introduced into 3D perovskite films through post-treatment with phenethylammonium chloride (PEACl). To minimize the degradation of film quality caused by PEACl treatment, a layer of guanidinium bromide (GABr) is vacuum evaporated on top of PEACl treatment to further improve the quality of emitting layer. Finally, under the synergistic post-processing modification of PEACl and GABr, blue PeLEDs with a maximum external quantum efficiency (EQE) of 6.09% and a maximum brightness of 1325 cd/m2 are successfully obtained. This work deepens the understanding of 2D/3D heterojunctions and provides a new approach to construct PeLEDs with high performance.
The progressive number of old adults with cognitive impairment worldwide and the lack of effective pharmacologic therapies require the development of non-pharmacologic strategies. The photobiomodulation (PBM) is a promising method in prevention of early or mild age-related cognitive impairments. However, it remains unclear the efficacy of PBM for old patients with significant age-related cognitive dysfunction. In our study on male mice, we show a gradual increase in the brain amyloid beta (Aβ) levels and a decrease in brain drainage with age, which, however, is associated with a decline in cognitive function only in old (24 months of age) mice but not in middle-aged (12 months of age) and young (3 month of age) animals. These age-related features are accompanied by the development of hyperplasia of the meningeal lymphatic vessels (MLVs) in old mice underlying the decrease in brain drainage. PBM improves cognitive training exercises and Aβ clearance only in young and middle-aged mice, while old animals are not sensitive to PBM. These results clearly demonstrate that the PBM effects on cognitive function are correlated with age-mediated changes in the MLV network and may be effective if the MLV function is preserved. These findings expand fundamental knowledge about age differences in the effectiveness of PBM for improvement of cognitive functions and Aβ clearance as well as about the lymphatic mechanisms responsible for age decline in sensitivity to the therapeutic PBM effects.
The integration of machine learning with photonic and optoelectronic components is progressing rapidly, offering the potential for high-speed bio-inspired computing platforms. In this work, we employ an experimental fiber-based dendritic structure with adaptive plasticity for a learning-and-control virtual task. Specifically, we develop a closed-loop controller embedded in a single-mode fiber optical dendritic unit (ODU) that incorporates Hebbian learning principles, and we test it in a hypothetical temperature stabilization task. Our optoelectronic system operates at 1 GHz signaling and sampling rates and applies plasticity rules through the direct modulation of semiconductor optical amplifiers. Although the input correlation (ICO) learning rule we consider here is computed digitally from the experimental output of the optoelectronic system, this output is fed back into the plastic properties of the ODU physical substrate, enabling autonomous learning. In this specific configuration, we utilize only three plastic dendritic optical branches with exclusively positive weighting. We demonstrate that, despite variations in the physical system’s parameters, the application of the ICO learning rule effectively mitigates temperature disturbances, ensuring robust performance. These results encourage an all-hardware solution, where optimizing feedback loop speed and embedding the ICO rule will enable continuous stabilization, finalizing a real-time platform operating at up to 1 GHz.
Silica nanoparticles were used to develop a bluish-green emitting Ba2SiO4:Eu2+ phosphor, demonstrating their potential for white light applications. The phosphor showed a 48% enhancement of emission intensity compared to conventional silica-assisted phosphors. The use of silica nanoparticles as a precursor could lead to the creation of a more homogeneous distribution of cations and dopant ions. This uniform distribution could facilitate the proper infusion of dopants into the crystal host, resulting in improved emission. The phosphor exhibited high thermal stability, with 56% of its luminescence intensity maintained even at 190 ℃ compared to room temperature. To reduce thermal stress, a flexible remote phosphor has been developed successfully using optimized silica nanoparticles assisted Ba2SiO4:Eu2+ phosphor.
The power conversion efficiency of all-perovskite tandem solar cells is predominantly constrained by optical absorption losses, especially reflection losses. In this simulation study, we propose the optimization of a dual-interface serrated microstructure to mitigate these optical reflection losses in all-perovskite tandem solar cells. By adjusting the geometry of the periodic serrated structures at both the front interface and the back electrode, we enhance light absorption in the wide-bandgap perovskite layer and promote light scattering in the narrow-bandgap perovskite layer. The structural modification reduces the reflection-induced photocurrent density loss from 4.47 to 3.65 mA cm-2. It is expected to boost the efficiency of all-perovskite tandem solar cells to approximately 31.13%, representing a 3.41% increase. The dual-interface optimization effectively suppresses reflection losses and improves the overall photocurrent of all-perovskite tandem solar cells. These results offer a promising strategy for minimizing optical losses and enhancing device performance in all-perovskite tandem solar cells.
Taking the advantage of ultrafast optical linear and nonlinear effects, all-optical signal processing (AOSP) enables manipulation, regeneration, and computing of information directly in optical domain without resorting to electronics. As a promising photonic integration platform, silicon-on-insulator (SOI) has the advantage of complementary metal oxide semiconductor (CMOS) compatibility, low-loss, compact size as well as large optical nonlinearities. In this paper, we review the recent progress in the project granted to develop silicon-based reconfigurable AOSP chips, which aims to combine the merits of AOSP and silicon photonics to solve the unsustainable cost and energy challenges in future communication and big data applications. Three key challenges are identified in this project: (1) how to finely manipulate and reconfigure optical fields, (2) how to achieve ultra-low loss integrated silicon waveguides and significant enhancement of nonlinear effects, (3) how to mitigate crosstalk between optical, electrical and thermal components. By focusing on these key issues, the following major achievements are realized during the project. First, ultra-low loss silicon-based waveguides as well as ultra-high quality microresonators are developed by advancing key fabrication technologies as well as device structures. Integrated photonic filters with bandwidth and free spectral range reconfigurable in a wide range were realized to finely manipulate and select input light fields with a high degree of freedom. Second, several mechanisms and new designs that aim at nonlinear enhancement have been proposed, including optical ridge waveguides with reverse biased PIN junction, slot waveguides, multimode waveguides and parity-time symmetry coupled microresonators. Advanced AOSP operations are verified with these novel designs. Logical computations at 100 Gbit/s were demonstrated with self-developed, monolithic integrated programmable optical logic array. High-dimensional multi-value logic operations based on the four-wave mixing effect are realized. Multi-channel all-optical amplitude and phase regeneration technology is developed, and a multi-channel, multi-format, reconfigurable all-optical regeneration chip is realized. Expanding regeneration capacity via spatial dimension is also verified. Third, the crosstalk from optical as well as thermal coupling due to high-density integration are mitigated by developing novel optical designs and advanced packaging technologies, enabling high-density, small size, multi-channel and multi-functional operation with low power consumption. Finally, four programmable AOSP chips are developed, i.e., programmable photonic filter chip, programmable photonic logic operation chip, multi-dimensional all-optical regeneration chip, and multi-channel and multi-functional AOSP chip with packaging. The major achievements developed in this project pave the way toward ultra-low loss, high-speed, high-efficient, high-density information processing in future classical and non-classical communication and computing applications.
This study explores the application of cold plate liquid cooling technology in co-packaged optics (CPO). By integrating optical modules and the switch chip on the same substrate, CPO shortens the electrical interconnection distance, effectively solving the problems of high power consumption and poor signal integrity of traditional pluggable optical modules under high bandwidth. However, the surge in power density and the thermal crosstalk resulting from high integration density make thermal management one of the key challenges that constrain the reliability of high-capacity co-packaged optics. For the unique architecture of CPO, this study analyzes its heat dissipation needs in detail, and a thermal management scheme is designed. The thermal management scheme is simulated and optimized based on the Navier−Stokes equation. The simulation results show that, in a 51.2 Tbit/s CPO system, the junction temperature of the switch chip is 97.3 °C, the maximum junction temperature of the optical modules is 31.3 °C, and the temperature difference between the optical modules is 2.4 °C to 1.2 °C. To verify the simulation results, a thermal test experimental platform is built, and the experimental results show that the temperature simulation difference is within 4% and the pressure change trend is consistent with the simulation. Combining the experimental data and simulation results, the designed heat sink can satisfy the heat dissipation demands of the 51.2 Tbit/s bandwidth CPO system. This conclusion demonstrates the potential of liquid-cooling technology in CPO, providing support for research on liquid-cooling technology in the CPO. The design provides a theoretical and practical basis for the high performance and reliability of optoelectronic integration technology in wavelength division multiplexing (WDM) systems and micro-ring device applications, contributing to the application of next-generation optical communication networks.
Under the excitation of a 980 nm laser, the visible upconversion (UC) luminescence of Er3+ ions doped Yb3+ ions selfactivated NaYb(MoO4)2 phosphor and crystal, as well as the Yb3+/Er3+ ions codoped NaBi(MoO4)2 crystal were investigated comprehensively. The results indicate that all three samples exhibit two significant green emission bands and a weak red emission band in the visible band corresponding to the transitions of 2H11/2/4S3/2→4I15/2 and 4F9/2→4I15/2 of Er3+ ions, respectively. Through the variable power density spectra of three different samples, the relationship between the energy back transfer (EBT) process of Yb3+-Er3+ ions and the power density point and Yb3+ ion concentration was investigated. The EBT process was observed in both the Er3+ ions doped Yb3+ ions self-activated NaYb(MoO4)2 phosphor and crystal, as confirmed by the luminescence image of the sample. At high power density, the Yb3+ ions self-activated sample exhibited yellow luminescence, with the crystal appearing later than the phosphor. In contrast, the NaBi(MoO4)2 crystal displayed bright green emission within the measured power density range. In addition, by monitoring the relative intensity change of Yb3+ emission in 5 at% Er3+: NaYb(MoO4)2 crystal, the generation of EBT process in self-activated samples at high power density is more directly explained. These experimental results provide a reliable basis for our comprehensive understanding of the EBT mechanism, and also provide a reliable direction for the final determination of the optimal excitation power density for optical temperature measurement.
