由于视网膜病变的类间图像特征差别小及分类临界值相对模糊，自动分级算法存在识别与分级准确率低的问题，提出了融合高效通道注意力（Efficient Channel Attention， ECA）特征的ConvNeXt视网膜病变自动分级模型。针对数据集中数据不足的问题，采用水平翻转左右变换的方法扩充数据，并引入相关数据集来均衡数据的分布。针对眼底图像中出现的图像模糊、光照不均等问题，采用Graham方法对图像进行预处理突出病变特征。提出了融合注意力的ConvNeXt网络来辅助医生诊断视网膜病变，引入ECA机制，并设计了E-Block模块，该模块具有高性能、低参数的特性，能够在训练过程中有效捕捉跨通道交互的信息，同时避免降维。采用迁移学习方法训练网络的所有层参数，加入dropout方法避免ConvNeXt网络的学习能力过强导致的过拟合问题。实验结果表明，所提出的模型敏感性为95.20%，特异度为98.80%，准确率为95.21%。与常用的网络相比，本文方法针对视网膜病变自动分级各项性能指标均有提高。

We present the frequency control of a 759 nm laser as a lattice laser for an ytterbium (Yb) optical clock. The frequency stability and accuracy are transferred from the Yb optical clock via an optical frequency comb. Although the comb is frequency-stabilized on a rubidium microwave clock, the frequency instability of the 759 nm laser is evaluated at the 10-15 level at 1 s averaging time. The frequency of the 759 nm laser is controlled with an uncertainty within 1 Hz by referencing to the Yb clock transition. Such a frequency-controlled 759 nm laser is suitable for Yb optical clocks as the lattice laser. The technique of laser frequency control can be applied to other lasers in optical clocks.

We report two ultra-stable laser systems automatically frequency-stabilized to two high-finesse optical cavities. By employing analog-digital hybrid proportional integral derivative (PID) controllers, we keep the merits of wide servo bandwidth and servo accuracy by using analog circuits for the PID controller, and, at the same time, we realize automatic laser frequency locking by introducing digital logic into the PID controller. The lasers can be automatically frequency-stabilized to their reference cavities, and it can be relocked in 0.3 s when interruption happens, i.e., blocking and unblocking the laser light. These automatic frequency-stabilized lasers are measured to have a frequency instability of 6×10-16 at 1 s averaging time and a most probable linewidth of 0.3 Hz. The laser systems were tested for continuous operation over 11 days. Such ultra-stable laser systems in long-term robust operation will be beneficial to the applications of optical atomic clocks and precision measurement based on frequency-stabilized lasers.

提出并设计了一种用于低温环境下测量温度的光纤布拉格光栅(FBG)双头管式封装结构，探究了涂覆层材料和封装形式对光纤Bragg光栅传感器低温传感稳定性和精度的影响。同时，试验研究了封装长度对双头管式传感器中心波长与温度的关系，通过多次重复试验测定了传感器低温灵敏度和重复性误差。研究结果表明：由于高折丙烯酸酯涂覆层具有较高的热膨胀系数，因此在77~273 K液氮环境中其增敏效果相对于聚酰亚胺和裸光纤更为显著；采用双头管封装后，FBG中心波长与温度具有高度线性关系，且能有效解决无封装裸FBG易受荷载扰动特性；适当提高封装长度有利于提高封装体系灵敏度系数。重复试验结果表明，所设计的双头管式封装FBG低温传感器灵敏度可达14~20 pm/K，测试误差和灵敏度优于传统FBG低温传感器。

We report a long-term frequency-stabilized optical frequency comb at 530–1100 nm based on a turnkey Ti:sapphire mode-locked laser. With the help of a digital controller, turnkey operation is realized for the Ti:sapphire mode-locked laser. Under optimized design of the laser cavity, the laser can be mode-locked over a month, limited by the observation time. The combination of a fast piezo and a slow one inside the Ti:sapphire mode-locked laser allows us to adjust the cavity length with moderate bandwidth and tuning range, enabling robust locking of the repetition rate (f_r) to a hydrogen maser. By combining a fast analog feedback to pump current and a slow digital feedback to an intracavity wedge and the pump power of the Ti:sapphire mode-locked laser, the carrier envelope offset frequency (f_ceo) of the comb is stabilized. We extend the continuous frequency-stabilized time of the Ti:sapphire optical frequency comb to five days. The residual jitters of f_r and f_ceo are 0.08 mHz and 2.5 mHz at 1 s averaging time, respectively, satisfying many applications demanding accuracy and short operation time for optical frequency combs.