Sensors based on optical resonators often have their measurement range limited by their cavity linewidth, particularly in the measurement of time-varying signals. This paper introduces a method for optical frequency shift detection using multiple harmonics to expand the dynamic range of sensors based on optical resonators. The proposed method expands the measurement range of optical frequency shift beyond the cavity linewidth while maintaining measurement accuracy. The theoretical derivation of this method is carried out based on the equation of motion for an optical resonator and the recursive relationship of the Bessel function. Experimental results show that the dynamic range is expanded to 4 times greater than the conventional first harmonic method while still maintaining accuracy. Furthermore, we present an objective analysis of the correlation between the expansion factor of the method and the linewidth and free spectrum of the optical resonator.

相较于单涡旋光束，涡旋阵列光束能够扩充信息的传输容量，研究其传输特性对其光通信应用具有重要意义。本文选取阶数为n的螺旋因斯-高斯(HIG_n,n)模式，采用海上大气折射率变换的功率谱，模拟海面大气湍流。基于相位屏法研究了一维阵列涡旋光束在海面大气湍流中光强、相位、闪烁因子和质心漂移的变化情况。结果表明：（1）HIG_n,n模式的闪烁因子和质心漂移标准差随湍流强度以及大气湍流内尺度的增加而增加；（2）n为奇数的HIG_n,n模式的闪烁因子随着阶数的增大而减小，且高于n为偶数的HIG_n,n模式；（3）阶数n>1的HIG_n,n模式比LG_0,1模式具有更好的稳定性；（4）阶数越高，HIG_n,n模式的质心漂移标准差越小。其次，选取线性阵列涡旋光束（LAVBs）进行对比，研究得出虽然LAVBs比HIG光束具有更好的传输性能，但由于HIG光束具有独特的结构，故可适用于不同的应用场景。最后，分析了椭圆参量和椭圆环数对HIG模式传输的影响，结果表明适当地增大椭圆参量或椭圆环数有助于提高HIG模式的抗湍流能力。本文研究结果对涡旋光束的海上应用具有指导意义。

光学电压传感器在温度稳定性方面仍有亟待解决的问题，一是电光晶体在温度变化时存在温度梯度，导致表面温度与光路温度不等；二是晶体物性参数也会受到温度影响。为此提出一种基于温度场与双卡尔曼滤波（Dual Kalman，D-Kalman）参数估计的温度补偿方法。以锗酸铋晶体为研究对象，在对传感器输出信号进行交直流分离的基础上，先利用半解析法建立晶体暂态温度场模型，再分别通过卡尔曼滤波与中心差分卡尔曼滤波实现对晶体内部温度和初始温度下晶体折射率的状态估计，最后将修正参数与传感器输出信号高频分量相结合计算补偿电压。实验结果表明，传感器在外界温度为［20 ℃，40 ℃］以0.5 ℃/min速率不断升高的环境下，暂态温度场解析式的仿真精度在0.02%以内，实验测量精度在0.2%左右，补偿输出电压测量精度优于0.52%。与同平台下反向传播神经网络温度补偿效果以及不同平台下的补偿效果相比，该方法提高了传感器测量精度。

针对传统γ射线探测实验装置定位精度不高、搭建麻烦、可开展的实验项目少，不利于实验重复与教学等缺点，该文设计开发了一款γ射线探测与测量综合实验教学平台，完成了平台的机械设计加工以及γ射线探测专用数字化多道分析器研制。基于该平台，可完成多个关于γ射线探测与应用的认知、基础、综合型、探究型实验项目。实践教学效果证明，该平台稳定性好，操作性强，实验结果准确，方便教师教学，能使学生更好地理解与掌握γ射线的性质、γ射线与物质相互作用的机制以及γ射线的应用。

We demonstrate the generation of a unique regime of multiple solitons in a Tm-doped ultrafast fiber laser at ∼1938.72 nm. The temporal pulse-to-pulse separation among the multiple solitons, 10 in a single-pulse bunch, increases from 0.89 ns to 1.85 ns per round trip. In addition, with the increasing pump power, the number of bunched solitons increases from 3 up to 24 linearly, while the average time separation in the soliton bunch varies irregularly between ∼0.80 and ∼1.52 ns. These results contribute to a more profound comprehension of nonlinear pulse dynamics in ultrafast fiber lasers.

High-intensity vortex beams with tunable topological charges and low coherence are highly demanded in applications such as inertial confinement fusion (ICF) and optical communication. However, traditional optical vortices featuring nonuniform intensity distributions are dramatically restricted in application scenarios that require a high-intensity vortex beam owing to their ineffective amplification resulting from the intensity-dependent nonlinear effect. Here, a low-coherence perfect vortex beam (PVB) with a topological charge as high as 140 is realized based on the super-pixel wavefront-shaping technique. More importantly, a globally adaptive feedback algorithm (GAFA) is proposed to efficiently suppress the original intensity fluctuation and achieve a flat-top PVB with dramatically reduced beam speckle contrast. The GAFA-based flat-top PVB generation method can pave the way for high-intensity vortex beam generation, which is crucial for potential applications in ICF, laser processing, optical communication and optical trapping.

Orbital angular momentum (OAM), described by an azimuthal phase term exp ( jlθ ) , has unbound orthogonal states with different topological charges l. Therefore, with the explosive growth of global communication capacity, especially for short-distance optical interconnects, light-carrying OAM has proved its great potential to improve transmission capacity and spectral efficiency in the space-division multiplexing system due to its orthogonality, security, and compatibility with other techniques. Meanwhile, 100-m free-space optical interconnects become an alternative solution for the “last mile” problem and provide interbuilding communication. We experimentally demonstrate a 260-m secure optical interconnect using OAM multiplexing and 16-ary quadrature amplitude modulation (16-QAM) signals. We study the beam wandering, power fluctuation, channel cross talk, bit-error-rate performance, and link security. Additionally, we also investigate the link performance for 1-to-9 multicasting at the range of 260 m. Considering that the power distribution may be affected by atmospheric turbulence, we introduce an offline feedback process to make it flexibly controllable.