Wandel Scott, Lin Ming-Wei, Yin Yanchun, Xu Guibao, Jovanovic Igor
Opt Express. 2016 Mar 7;24(5):5287-5299. doi: 10.1364/OE.24.005287.
Ultrafast mid-infrared (IR) coherent radiation plays an important role in strong-field physics, wherein the use of longer wavelengths has reduced the optical intensities needed to drive light-matter interactions by orders of magnitude in comparison to near-IR radiation. Optimizing parametric interactions for generation and characterization of mid-IR pulses is an enabling step for those applications. We report on the production of >50 µJ femtosecond pulses centered at 5 µm in a two-stage optical parametric amplifier (OPA) based on ZnGeP, a high-performance optical material in this spectral region. The OPA is pumped by an ultrafast 2-µm source. Amplified pulses have been characterized by parametric upconversion, enabling the use of standard silicon detectors. A numerical model of the system has been developed and tested to control dispersion, group-velocity mismatch, and off-axis parametric fluorescence. The source architecture is suitable for production of mJ-level mid-IR ultrafast pulses without the use of chirped-pulse amplification, where convenient pumping could be realized directly by mid-IR laser sources based on materials such as Cr:ZnSe or Cr:ZnS.
超快中红外（IR）相干辐射在强场物理中起着重要作用，与近红外辐射相比，在该领域使用更长波长可将驱动光与物质相互作用所需的光强度降低几个数量级。优化用于产生和表征中红外脉冲的参量相互作用是实现这些应用的关键一步。我们报告了基于ZnGeP（该光谱区域的一种高性能光学材料）的两级光学参量放大器（OPA）产生中心波长为5 µm、能量大于50 µJ的飞秒脉冲。该OPA由超快2 µm光源泵浦。放大后的脉冲通过参量上转换进行了表征，从而能够使用标准硅探测器。已开发并测试了该系统的数值模型，以控制色散、群速度失配和离轴参量荧光。该光源架构适用于在不使用啁啾脉冲放大的情况下产生mJ级中红外超快脉冲，通过基于Cr:ZnSe或Cr:ZnS等材料的中红外激光源可直接实现便捷泵浦。
