可见光通信（VLC）技术巧妙地融合了通信和照明或显示功能，为通信提供了高效便捷的方案。有机电致发光器件（OLED）作为最接近自然阳光的人造光源，在可见光通信系统的发射端展现出巨大的应用潜力。然而，受制于有机发光染料激子辐射复合速率较慢的限制，OLED在高频信号激励时响应速度较慢。为了克服这一限制，我们提出利用微腔结构，旨在通过微腔效应增强有机发光分子的自发辐射速率，从而改善器件的频率响应。研究结果表明，特定腔长的光学微腔引发的Purcell效应能够提升特定波长的光子态密度，从而加速其自发辐射速率。这种增强效应成功地将调制带宽从4 kHz提高到7 kHz，拓展了近75%的响应频率范围。

Topological nodal-line semimetals attract growing research attention in the photonic and optoelectronic fields due to their unique topological energy-level bands and fascinating nonlinear optical responses. Here, to the best of our knowledge, we first report the saturable absorption property of topological nodal-line semimetal HfGeTe and the related pulse modulation in passively Q-switched visible lasers. Few-layer HfGeTe demonstrates outstanding saturable absorption properties in the visible-light band, yielding the saturation intensities of 7.88, 12.66, and 6.64 µJ/cm² at 515, 640, and 720 nm, respectively. Based on an as-prepared few-layer HfGeTe optical switch and a Pr:LiYF₄ gain medium, Q-switched visible lasers are also successfully achieved at 522, 640, and 720 nm. The minimum pulse widths of the green, red, and deep-red pulsed lasers are 150, 125.5, and 420 ns, respectively. Especially for the green and red pulsed laser, the obtained pulse width is smaller than those of the low-dimensional layered materials. Our work sheds light on the application potential of topological nodal-line semimetals in the generation of visible pulsed lasers.

工业废水分类是水污染防治和水资源管理的前提和基础，相较于生活污水，工业废水的分类研究相对滞后。水体化学需氧量 (COD) 是衡量水体质量的核心指标，针对现有工业废水COD分类算法中预测精度较低的问题，提出基于门控循环单元 (GRU) 的卷积神经网络 (CNN) 混合模型。该模型首先将紫外-可见光谱法测得的工业废水COD数据进行高斯滤波去噪，然后把去噪后的光谱数据输入CNN模型进行特征提取，最后通过GRU神经网络实现工业废水COD分类。实验结果显示，CNN-GRU分类模型经过200次训练后达到收敛, 分类精度达到99.5%，与长短期记忆方法、GRU方法、CNN-LSTM方法相比，该混合模型的分类精度具有显著优势。

Although visible femtosecond lasers based on nonlinear frequency conversion of Ti:sapphire femtosecond oscillators or near-infrared ultrafast lasers have been well developed, limitations in terms of footprint, cost, and efficiency have called for alternative laser solutions. The fiber femtosecond mode-locked oscillator as an ideal solution has achieved great success in the 0.9 to 3.5 μm infrared wavelengths, but remains an outstanding challenge in the visible spectrum (390 to 780 nm). Here, we tackle this challenge by introducing a visible-wavelength mode-locked femtosecond fiber oscillator along with an amplifier. This fiber femtosecond oscillator emits red light at 635 nm, employs a figure-nine cavity configuration, applies a double-clad Pr^{3 +} -doped fluoride fiber as the visible gain medium, incorporates a visible-wavelength phase-biased nonlinear amplifying loop mirror (PB-NALM) for mode locking, and utilizes a pair of customized high-efficiency and high-groove-density diffraction gratings for dispersion management. Visible self-starting mode locking established by the PB-NALM directly yields red laser pulses with a minimum pulse duration of 196 fs and a repetition rate of 53.957 MHz from the oscillator. Precise control of the grating pair spacing can switch the pulse state from a dissipative soliton or a stretched-pulse soliton to a conventional soliton. In addition, a chirped-pulse amplification system built alongside the oscillator immensely boosts the laser performance, resulting in an average output power over 1 W, a pulse energy of 19.55 nJ, and a dechirped pulse duration of 230 fs. Our result represents a concrete step toward high-power femtosecond fiber lasers covering the visible spectral region and could have important applications in industrial processing, biomedicine, and scientific research.