Single-cycle terahertz pulses with amplitudes exceeding 1 MV/cm generated by optical rectification in LiNbO3 and applications to nonlinear optics
Single-cycle terahertz pulses with amplitudes exceeding 1 MV/cm generated by optical rectification in LiNbO3 and applications to nonlinear optics
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DOI：
10.1117/12.910063
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发表时间：
2011-02
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影响因子：
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通讯作者：
H. Hirori;Koichiro Tanaka
中科院分区：
文献类型：
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作者：
H. Hirori;Koichiro Tanaka
利用倾斜泵浦脉冲前沿方案，在LiNbO_3晶体中对飞秒激光脉冲进行光学整流，获得了单周期太赫兹(THz)脉冲。在我们的太赫兹产生装置中，为了获得最佳的太赫兹光束特性和泵浦-太赫兹转换效率，必须满足光栅的图像与倾斜的光脉冲前沿重合的条件。产生的太赫兹脉冲的光谱中心在1太赫兹左右。设计的聚焦几何结构可以使太赫兹光束紧密聚焦，光斑尺寸接近衍射极限，获得了1.2 mV/cm的最大太赫兹电场。此外，还研究了强太赫兹脉冲与GaAs量子阱的非线性相互作用。在这里，我们展示了与直流偏压不同的是，强烈的太赫兹脉冲可以产生大量的电子-空穴对，形成激子，发出近红外发光。与载流子倍增相关的明亮发光表明，在强场的相干驱动下，载流子可以有效地获得足够的动能来诱导一系列碰撞电离，这可以在皮秒时间尺度上使载流子数量增加约三个数量级。
Using a tilted-pump-pulse-front scheme, we generate single-cycle terahertz (THz) pulses by optical rectification of femtosecond laser pulses in LiNbO3. In our THz generation setup, to obtain optimal THz beam characteristics and pumpto- THz conversion efficiency the condition that an image of a grating coincides with a tilted-optical-pulse front is fulfilled. Generated THz pulses have spectra centered at around 1 THz. A designed focusing geometry enables tight focus of the THz beam with a spot size close to the diffraction limit, and the maximum THz electric field of 1.2 MV/cm is obtained. In addition, the nonlinear interactions of GaAs quantum wells with the intense THz pulses have been studied. Here we show that the intense THz pulse, unlike a DC bias, can generate a substantial number of electron-hole pairs forming excitons that emit near-infrared luminescence. The bright luminescence associated with carrier multiplication suggests that the carriers coherently driven by a strong field can efficiently gain enough kinetic energy to induce a series of impact ionizations, which we demonstrate can increase the number of carriers by about three orders of magnitude on picosecond timescale.