Bodrov S B, Stepanov A N, Bakunov M I
Opt Express. 2019 Feb 4;27(3):2396-2410. doi: 10.1364/OE.27.002396.
It is commonly adopted that the widely used method of terahertz generation by tilted-pulse-front pumping of a lithium niobate crystal is optimized when both the tilted front of the pump optical pulse and the image of the diffraction grating, which introduces the tilt, are parallel to the exit surface of the crystal. We consider more general situations. In particular, we show that a deviation of the grating image plane from parallel to the crystal exit surface leads to deterioration of the terahertz beam quality but does not significantly affect the terahertz energy. If the grating image plane and the crystal exit surface are mutual parallel, but they are nonparallel to the pulse front, the terahertz beam quality remains unaffected and the terahertz energy can be unexpectedly higher (about two times for pump pulses of a ~400 fs duration) than in the standard scheme. We propose a modified design of the tilted-pulse-front scheme based on our findings.
通常采用的方法是，当泵浦光脉冲的倾斜前沿和引入倾斜的衍射光栅的像都与铌酸锂晶体的出射面平行时，对通过倾斜脉冲前沿泵浦铌酸锂晶体产生太赫兹的广泛使用方法进行优化。我们考虑更一般的情况。特别是，我们表明光栅像平面偏离与晶体出射面平行会导致太赫兹光束质量下降，但不会显著影响太赫兹能量。如果光栅像平面与晶体出射面相互平行，但它们与脉冲前沿不平行，太赫兹光束质量不受影响，并且太赫兹能量可能会出乎意料地更高（对于持续时间约为400 fs的泵浦脉冲，大约是标准方案的两倍）。基于我们的发现，我们提出了一种改进的倾斜脉冲前沿方案设计。
