The tilted-pulse-front setup utilizing a diffraction grating is one of the most successful methods to generate single- to few-cycle terahertz pulses. However, the generated terahertz pulses have a large spatial inhomogeneity, due to the noncollinear phase-matching condition and the asymmetry of the prism-shaped nonlinear crystal geometry, especially when pushing for high optical-to-terahertz conversion efficiency. A ${\rm 3D} + 1$ (${x,y,z,t}$) numerical model is necessary in order to fully investigate the terahertz generation problem in the tilted-pulse-front scheme. We compare in detail the differences among ${\rm 1D} + 1$, ${\rm 2D} + 1$, and ${\rm 3D} + 1$ models. The simulations show that the size of the optical beam in the pulse-front-tilt plane sensitively affects the spatiotemporal properties of the terahertz electric field. The terahertz electric field is found to have a strong spatial dependence such that a few-cycle pulse is generated only near the apex of the prism. Even though the part of the beam farther from the apex can contain a large fraction of the energy, the terahertz waveform shows less few-cycle character. This strong spatial dependence must be accounted for when using the terahertz pulses for strong-field physics and carrier-envelope-phase sensitive experiments such as terahertz acceleration, coherent control of antiferromagnetic spin waves, and terahertz high-harmonic generation.

中文翻译：

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完整的3D +1倾斜脉冲前设置建模，可生成单周期太赫兹

利用衍射光栅的倾斜脉冲前设置是产生单周期至几周期太赫兹脉冲的最成功方法之一。但是，由于非共线相位匹配条件和棱柱形非线性晶体几何形状的不对称性，特别是在追求高光-太赫兹转换效率时，产生的太赫兹脉冲具有较大的空间不均匀性。为了充分研究倾斜脉冲前方案中的太赫兹生成问题，必须使用$ {\ rm 3D} + 1 $（$ {x，y，z，t} $）数值模型。我们将详细比较$ {\ rm 1D} + 1 $，$ {\ rm 2D} + 1 $和$ {\ rm 3D} + 1 $之间的差异楷模。仿真表明，脉冲前倾平面中光束的大小敏感地影响了太赫兹电场的时空特性。发现太赫兹电场具有很强的空间依赖性，因此仅在棱镜的顶点附近会产生几个周期的脉冲。即使光束远离顶点的部分可能包含很大一部分能量，太赫兹波形也显示出较少的周期特性。当使用太赫兹脉冲进行强场物理和对载波-包络相敏感的实验（例如太赫兹加速度，反铁磁自旋波的相干控制以及太赫兹高谐波产生）时，必须考虑这种强烈的空间依赖性。