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首页> 外文会议>Conference on Terahertz and Gigahertz Electronics and Photonics >Generation of multi-cycle THz-pulses via optical rectification in periodically inverted GaAs
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Generation of multi-cycle THz-pulses via optical rectification in periodically inverted GaAs

机译：在定期倒置的GaAs中通过光学整流产生多循环Thz脉冲

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We demonstrate an efficient room temperature source of narrow-bandwidth terahertz (THz) radiation using femtosecond pump pulses and periodic GaAs structure as a nonlinear material. In the past, several THz generation schemes exploited optical rectification in nonlinear crystals using femtosecond laser technology. Most of them generated single-cycle THz-pulses with broad bandwidth, using nonlinear crystals shorter than the phase-matching coherence length. Recently a novel technique to generate multi-cycle THz-pulses in the pre-engineered domain structure of periodically-poled lithium niobate (PPLN) crystals has been demonstrated. Quasi-phase matching (QPM) structures such as PPLN consist of a periodic system of domains of inverted crystal orientation. The sign of second order nonlinear polarization generated by femtosecond pulses is inverted at domain boundaries. If domain length is comparable with coherence length, QPM between THz-wave and nonlinear polarization extends the interaction length between THz and optical pulses. In the present work, using periodic GaAs structures we have achieved exceptionally high photon as well as energy conversion efficiency: 3% and 0.07% respectively. We have examined two different types of periodic QPM GaAs samples: diffusion-bonded GaAs wafers and all-epitaxially-grown orientation-patterned GaAs crystals with 3-10 mm thicknesses. The incident optical pulse energy was in the micro-Joule range and pulse duration was ~100 fsec. We measured spectral properties of THz radiation using Michelson interferometer and a bolometer. Narrow-bandwidth (~100GHz) THz output, tunable between 1 and 3 THz, was achieved. THz frequency was tuned either by tuning the light source wavelength between 2 and 4.4 microns, or by selecting GaAs samples with different QPM periods. Our theoretical analysis, based on known GaAs dispersion properties, shows good agreement between the measured and predicted THz frequencies.
机译：我们展示了使用飞秒泵脉冲和周期性GaAs结构作为非线性材料的窄带宽太赫兹（THz）辐射的有效室温源。过去，几种THz生成方案使用飞秒激光技术利用非线性晶体中的光学整流。它们中的大多数产生具有宽带宽的单周期THz脉冲，使用比相位匹配的相干长度短的非线性晶体。最近，已经证明了一种新的技术，用于在定期抛光铌酸锂（PPLN）晶体的预工程结构域结构中产生多循环THZ脉冲。诸如PPLN的准相位匹配（QPM）结构包括倒晶域的周期性系统。由飞秒脉冲产生的二阶非线性极化的符号在域边界处反转。如果域长度与相干长度相当，则THz波和非线性偏振之间的QPM延伸了THz和光脉冲之间的相互作用长度。在本作工作中，使用周期性GaAs结构，我们已经实现了极高的光子以及能量转换效率：3％和0.07％。我们已经检查了两种不同类型的周期性QPM GaAs样本：扩散键合的GaAs晶片和具有3-10mm厚度的全外延增长的取向图案化GaAs晶体。入射光脉冲能量在微焦耳范围内，脉冲持续时间为〜100 fsec。我们使用Michelson干涉仪和辐射计测量了THz辐射的光谱特性。实现窄带宽（〜100GHz）THz输出，在1到3星之间进行可调。通过调谐2到4.4微米之间的光源波长或通过选择具有不同QPM时段的GaAs样本来调谐THz频率。我们基于已知的GaAs色散性能的理论分析显示了测量和预测的THz频率之间的良好一致性。

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