Vertical GaN power MOSFET is a novel technology that offers great potential for power switching applications. Being still in an early development phase, vertical GaN devices are yet to be fully optimized and require careful studies to foster their development. In this work, we report on the physical insights into device performance improvements obtained during the development of vertical GaN-on-Si trench MOSFETs (TMOS’s) provided by TCAD simulations, enhancing the dependability of the adopted process optimization approaches. Specifically, two different TMOS devices are compared in terms of transfer-curve hysteresis (H) and subthreshold slope (SS), showing a ≈ 75% H reduction along with a ≈ 30% SS decrease. Simulations allow attributing the achieved improvements to a decrease in the border and interface traps, respectively. A sensitivity analysis is also carried out, allowing to quantify the additional trap density reduction required to minimize both figures of merit.

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.

为了解决三自由度压电驱动纳米偏摆台中的多轴耦合与迟滞问题，设计了一种可以同时表征多个压电驱动器间耦合效应及其自身迟滞效应的耦合迟滞模型，并利用其逆模型进行前馈补偿以提升平台的定位和轨迹跟踪精度。首先，搭建了三自由度压电驱动偏摆台的控制系统并建立其运动学模型，将末端平台三自由度运动转化为三个压电驱动器的输出。然后，建立基于Prandtl-Ishlinskii模型的耦合迟滞模型，并对该模型及其逆模型的参数进行辨识。最后，通过开环逆模型前馈补偿来验证模型的有效性，并利用结合逆模型前馈和反馈的复合控制方法进行轨迹跟踪控制。实验结果表明：逆模型开环前馈补偿使三个压电驱动器间最大耦合位移均降低了70%以上，证明了所建立耦合迟滞模型的有效性，结合闭环反馈的复合控制方法对空间轨迹进行跟踪的最大均方根误差仅为0.06 mrad和0.42 μm，相比单纯闭环反馈分别减少了72%和87.5%，最大误差也减少了76%以上，有效消除了平台中耦合迟滞的影响，提高了平台的定位精度。

精密减速器回差试验台是非标设备，迄今对其精度特性缺乏系统性研究以至于还没有检定规程去评定该类测试设备的计量性能。为了评估精密减速器回差试验台的精度特性，提出了试验台精度的评定方法。首先，分析了精密减速器回差试验台的结构，确定了转矩传感器测量误差、角度传感器测量误差、转矩测量链摩擦转矩以及角度测量链弹性扭转角这四个因素是影响试验台精度的主要误差源。接着，研究了误差源的作用机理，提出了通过滞回曲线将转矩类误差转换为角度类误差的方法，统一了误差的类型。然后，提出了滞回曲线局部线性化的概念，实现了转矩类误差转换为角度类误差的简便计算。最后，根据回差的表达式给出了试验台精度的评定方法，并进行了测试实践。结果表明：几何回差的测试误差为±0.04ʹ；弹性回差的测试误差为±0.06'；总回差的测试误差为±0.04'，回差试验台精度满足要求，本文提出的方法对评定试验台精度是有效的。另外，对精密减速器输出端一转范围内多处测试，能提升测试精度。