Fluorescence lifetime imaging can reveal the high-resolution structure of various biophysical and chemical parameters in a microenvironment quantitatively. However, the depth of imaging is generally limited to hundreds of micrometers due to aberration and light scattering in biological tissues. This paper introduces an iterative multi-photon adaptive compensation technique (IMPACT) into a two-photon fluorescence lifetime microscopy system to successfully overcome aberrations and multiple scattering problems in deep tissues. It shows that 400 correction modes can be achieved within 5 min, which was mainly limited by the frame rate of a spatial light modulator. This system was used for high-resolution imaging of mice brain tissue and live zebrafish, further verifying its superior performance in imaging quality and photon accumulation speed.

水下光学成像技术对于海底资源勘测、海洋生态监测、水下搜索救援、水下考古等应用具有重要意义。相比传统水下摄像机，距离选通成像技术可以过滤选通切片外的后向散射噪声和环境背景噪声，实现高质量水下成像，但是在浑浊水体中仍然会受切片内后向散射噪声影响，导致成像距离缩短。对此，开展了光学偏振与距离选通成像结合的水下偏振选通成像技术研究，利用后向散射光良好的保偏性去除选通切片范围内的后向散射噪声，提升目标识别距离。通过理论仿真和实验研究，对比分析了不同水质下距离选通成像和偏振选通成像目标识别距离的差异。发现存在临界衰减系数c₀：当水体衰减系数小于等于c₀时，光学偏振对于提升距离选通成像工作距离无效果；当水体衰减系数大于c₀时，偏振可提升距离选通成像工作距离。实验中还发现，目标反射率会影响临界衰减系数。该研究有利于不同水质下距离选通成像的优化应用。

Two-dimensional (2D) nonlinear optical mediums with high and tunable light modulation capability can significantly stimulate the development of ultrathin, compact, and integrated optoelectronics devices and photonic elements. 2D carbides and nitrides of transition metals (MXenes) are a new class of 2D materials with excellent intrinsic and strong light-matter interaction characteristics. However, the current understanding of their photo-physical properties and strategies for improving optical performance is insufficient. To address this issue, we rationally designed and in situ synthesized a 2D Nb₂C/MoS₂ heterostructure that outperforms pristine Nb₂C in both linear and nonlinear optical performance. Excellent agreement between experimental and theoretical results demonstrated that the Nb₂C/MoS₂ inherited the preponderance of Nb₂C and MoS₂ in absorption at different wavelengths, resulting in the broadband enhanced optical absorption characteristics. In addition to linear optical modulation, we also achieved stronger near infrared nonlinear optical modulation, with a nonlinear absorption coefficient of Nb₂C/MoS₂ being more than two times that of the pristine Nb₂C. These results were supported by the band alinement model which was determined by the X-ray photoelectron spectroscopy (XPS) experiment and first-principal theory calculation. The presented facile synthesis approach and robust light modulation strategy pave the way for broadband optoelectronic devices and optical modulators.

Optical microcavities offer a promising platform for highly efficient light–matter interactions. Recently, the combination of microresonators and 2D materials in the nanoscale has further enriched the optoelectronics of microcavity geometries, spurring broad advances including lasers, nonlinear converters, modulators, and sensors. Here, we report the concept of compact dual-laser cogeneration in a graphene-microcavity fiber, which offers a way to cancel the optical common mode noises. Driven by a single 980 nm pump, orthogonally polarized laser lines are generated in a pair of degeneracy breaking modes. The two laser lines produce a heterodyne beat note at 118.96 MHz, with frequency noise down to 200Hz2/Hz at 1 MHz offset, demonstrating a linewidth of 930 Hz in vacuum. This compact device enables on-line and label-free NH3 gas detection with high resolution, realizing a detection limit on a single pmol/L level, and a capability to quantitatively trace gas–graphene interactions. Such a combination of graphene optoelectronics and microcavity photonics demonstrates a novel physical paradigm for microlaser control and offers a new scheme for in situ chemical sensing.

为满足高能同步辐射光源（High Energy Photon Source，HEPS）束流位置测量的需求，研制了各种类型的束流位置探测器（Beam Position Monitor，BPM）。位置灵敏度系数是BPM的一项重要参数，通过它可以精确计算束流的位置。使用边界元法计算束流位置探测器的灵敏度系数，适用于在无法使用天线模拟束流进行实际测量和有限元软件进行模拟的场合。以HEPS储存环BPM的参数为例，首先用边界元法分析计算了具有圆形横截面的BPM的位置灵敏度系数，在此基础上，分析了椭圆形（HEPS增强器）与八边形（BEPCII储存环）管道的系数。将该方法应用于BPM的设计与分析中，确定了高能光源增强器BPM纽扣电极的方位角和北京正负电子对撞机BPM的纽扣电极间距。此外，计算了上述BPM的位置灵敏度系数分布Mapping图。圆形管道BPM的位置灵敏度系数结果与解析值接近，相对误差在1%左右，椭圆形与八边形管道BPM的计算结果与实际测量结果的偏差都在2%左右，证明了边界元法计算束流位置探测器的位置灵敏度系数是一种可靠的方法，可用于BPM的设计与相关问题的分析。