Terahertz (THz) time-domain spectroscopy (TDS) is a sensitive approach to material characterization. It critically relies on a sufficiently large bandwidth, which is not straightforwardly available in typical THz-TDS systems that are often limited to below 3 THz. Here, we introduce a hybrid THz-source concept based on a spintronic THz emitter (STE) deposited onto a thin, free-standing GaSe nonlinear crystal. By tuning the magnetic state and the phase-matching parameters of the hybrid emitter, we generate an ultrabroadband spectrum covering the full range from 1 to 40 THz. We achieve significantly enhanced spectral amplitudes above 10 THz compared to the bare STE, resulting in ultrashort THz-pulse durations down to 32 fs. Finally, we demonstrate the straightforward tunability of the shape of the few-cycle pulse from symmetric to antisymmetric.

中文翻译：

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结合自旋电子学和 GaSe 源的可调谐超宽带混合太赫兹发射器


太赫兹 （THz） 时域光谱 （TDS） 是一种对材料表征敏感的方法。它严重依赖于足够大的带宽，而这在通常限制在 3 THz 以下的典型 THz-TDS 系统中并不容易获得。在这里，我们介绍了一种基于自旋电子太赫兹发射器 （STE） 的混合太赫兹源概念，该概念沉积在薄的独立式 GaSe 非线性晶体上。通过调整混合发射器的磁态和相位匹配参数，我们生成了覆盖 1 至 40 THz 整个范围的超宽带频谱。与裸 STE 相比，我们实现了 10 THz 以上的显著增强频谱幅度，从而将超短 THz 脉冲持续时间降至 32 fs。最后，我们证明了小周期脉冲形状从对称到反对称的直接可调性。