We identify the physical factors that limit the terahertz (THz) yield of an optical rectification (OR) of ultrashort multiterawatt laser pulses in large-area quadratically nonlinear crystals. We show that the THz yield tends to slow its growth as a function of the laser driver energy, saturate, and eventually decrease as the laser beam picks up a spatiotemporal phase due to the intensity-dependent refraction of the OR crystal. We demonstrate that, with a careful management of the driver intensity aimed at keeping the nonlinear length larger than the coherence length, OR-based broadband THz generation in large-area lithium niobate (LN) crystals is energy-scalable, enabling an OR of multiterawatt laser pulses, yielding ${\sim 10}$ $\unicode{x00B5} {\rm{J}}/{\rm{cm}}^2$ of THz output energy per unit crystal area. With a 27-fs, 10-TW, 800-nm Ti:sapphire laser output used as a driver for OR in large-area LN crystals, this approach is shown to provide a THz output with a pulse energy above 10 µJ and a bandwidth extending well beyond 6 THz, supporting single-cycle THz waveforms.

中文翻译：

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通过对光束分裂阈值附近的超短多太瓦激光脉冲进行光学整流来产生宽带太赫兹

我们确定了限制大面积二次非线性晶体中超短多太瓦激光脉冲光学整流 (OR) 的太赫兹 (THz) 产量的物理因素。我们表明，由于 OR 晶体的强度相关折射，太赫兹产量趋于减慢其增长，作为激光驱动器能量的函数，饱和并最终随着激光束拾取时空相位而降低。我们证明，通过仔细管理旨在保持非线性长度大于相干长度的驱动强度，大面积铌酸锂 (LN) 晶体中基于 OR 的宽带 THz 生成是能量可扩展的，从而实现了多太瓦的 OR激光脉冲，产生${\sim 10}$ $\unicode{x00B5} {\rm{J}}/{\rm{cm}}^2$每单位晶体面积的太赫兹输出能量。使用 27-fs、10-TW、800-nm Ti:sapphire 激光输出作为大面积 LN 晶体中 OR 的驱动器，这种方法显示出提供脉冲能量高于 10 µJ 和带宽的太赫兹输出远远超出 6 THz，支持单周期 THz 波形。