为了实现Ka波段回旋行波管高纯度TE₀₁模式输入，通过在输出口添加滤波结构，对二级功分TE₀₁输入耦合器进行改进，改进后杂散模式传输效率由平均7%下降至2%。该结构主体为一个级联的两级Y型功分网络，能高效地实现矩形波导TE₁₀模式到圆波导TE₀₁模式的转换。在基于传输线理论对功分网络的传输性能理论分析的基础上，借助三维电磁仿真软件进行多次优化迭代，最终得到了一个在31 GHz附近模式转换效率大于99%的宽带TE₀₁输入耦合器, 该输入耦合器具有5 GHz的−0.1 dB插入损耗带宽，同时有效频带内的平均模式转换效率高达98.6%，模式纯度在99%以上并且回波损耗小于−15 dB。采用矢量网络分析仪对该器件进行了背靠背冷测实验，结果表明，其带内衰减约为0.5 dB，与仿真计算结果偏差较小，符合工程实际需求。

Light plays a central role in many applications. The key to unlocking its versatility lies in shaping it into the most appropriate form for the task at hand. Specifically tailored refractive index modifications, directly manufactured inside glass using a short pulsed laser, enable an almost arbitrary control of the light flow. However, the stringent requirements for quantitative knowledge of these modifications, as well as for fabrication precision, have so far prevented the fabrication of light-efficient aperiodic photonic volume elements (APVEs). Here, we present a powerful approach to the design and manufacturing of light-efficient APVEs. We optimize application-specific three-dimensional arrangements of hundreds of thousands of microscopic voxels and manufacture them using femtosecond direct laser writing inside millimeter-sized glass volumes. We experimentally achieve unprecedented diffraction efficiencies up to 80%, which is enabled by precise voxel characterization and adaptive optics during fabrication. We demonstrate APVEs with various functionalities, including a spatial mode converter and combined intensity shaping and wavelength multiplexing. Our elements can be freely designed and are efficient, compact, and robust. Our approach is not limited to borosilicate glass but is potentially extendable to other substrates, including birefringent and nonlinear materials, giving a preview of even broader functionalities, including polarization modulation and dynamic elements.

We report on a vortex laser chirped-pulse amplification (CPA) system that delivers pulses with a peak power of 45 TW. A focused intensity exceeding 10¹⁹ W/cm² has been demonstrated for the first time by the vortex amplification scheme. Compared with other schemes of strong-field vortex generation with high energy flux but narrowband vortex-converting elements at the end of the laser, an important advantage of our scheme is that we can use a broadband but size-limited q-plate to realize broadband mode-converting in the front end of the CPA system, and achieve high-power amplification with a series of amplifiers. This method is low cost and can be easily implemented in an existing laser system. The results have verified the feasibility to obtain terawatt and even petawatt vortex laser amplification by a CPA system, which has important potential applications in strong-field laser physics, for example, generation of vortex particle beams with orbital angular momentum, fast ignition for inertial confinement fusion and simulation of the extreme astrophysical environment.

We report on a conceptually new type of waveguide in glass by femtosecond laser direct writing, namely, photonic lattice-like waveguide (PLLW). The PLLW’s core consists of well-distributed and densified tracks with a sub-micron size of 0.62 µm in width. Specifically, a PLLW inscribed as hexagonal-shape input with a ring-shape output side was implemented to converse Gaussian mode to doughnut-like mode, and high conversion efficiency was obtained with a low insertion loss of 1.65 dB at 976 nm. This work provides a new freedom for design and fabrication of the refractive index profile of waveguides with sub-micron resolution and broadens the functionalities and application scenarios of femtosecond laser direct-writing waveguides in future 3D integrated photonic systems.

基于开放式谐振腔及准光学模式变换理论，设计并实现了一种应用于回旋管振荡器冷测的高阶模式激励器。以140 GHz、TE_28，8模工作为例，通过计算机编程控制三维移动测量平台和网络分析仪完成了相应的实验测量。当模拟仿真获得在谐振腔激起频率为140.179 GHz、Q值为855、输出场分布与TE_28，8模的相关性为90.9 %时，对应设计构建模式激励器完成的冷测结果频率为140.155 GHz、Q值为876、横向电场明显具有TE_28，8的特征，为回旋管振荡器研究和设计过程检验提供了一个有效的实验平台。

文章提出了一种3-μm中红外波段偏振无关且CMOS兼容的石墨烯调制器，器件主要包括两部分：模式转换结构及石墨烯调制器。该调制器不仅满足于CMOS兼容的要求，而且能够实现基膜的偏振无关调制。仿真结果表明该调制器在2.95 μm到3.05 μm的中红外波段能够实现高于20 dB的消光比，TE和TM模式的插入损耗都低于1.3 dB，其偏振相关损耗低于1.09 dB。通过计算，当器件长度为420 μm，能够获得高达9.47 GHz的3 dB带宽。