Recent developments in laser sources operating in the mid-IR (3–8μm) have been motivated by the numerous possibilities for both fundamental and applied research. One example is the ability to unambiguously detect pollutants and carcinogens due to the much larger oscillator strengths of their absorption features in the mid-IR spectral region compared with the visible. Broadband sources are of particular interest for spectroscopic applications since they remove the need for arduous scanning or several lasers and allow simultaneous use of multiple absorption features thus increasing the confidence level of detection. In addition, sources capable of producing ultrashort and intense mid-IR radiation are gaining relevance in attoscience and strong-field physics due to wavelength scaling of re-collision based processes. In this paper we review the state-of-the-art in sources of coherent, pulsed mid-IR radiation. First we discuss semi-conductor based sources which are compact and turnkey, but typically do not yield short pulse duration. Mid-IR laser gain material based approaches will be discussed, either for direct broadband mid-IR lasers or as narrowband pump lasers for parametric amplification in nonlinear crystals. The main part will focus on mid-IR generation and amplification based on parametric frequency conversion, enabling highest mid-IR peak power pulses. Lastly we close with an overview of nonlinear post-compression techniques, for decreasing pulse duration to the sub-2-optical-cycle regime.

中文翻译：

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中红外超短脉冲生成

中红外（3-8μm）激光源的最新发展受到基础研究和应用研究的众多可能性的推动。一个例子是明确检测污染物和致癌物质的能力，因为与可见光相比，它们在中红外光谱区域的吸收特征的振荡强度要大得多。宽带光源对光谱应用特别感兴趣，因为它们不需要费力的扫描或多个激光器，并允许同时使用多个吸收特征，从而提高检测的置信度。此外，由于基于再碰撞的过程的波长缩放，能够产生超短和强中红外辐射的源在自体科学和强场物理学中越来越重要。在本文中，我们回顾了相干脉冲中红外辐射源的最新技术。首先，我们讨论基于半导体的源，它们是紧凑和交钥匙的，但通常不会产生短脉冲持续时间。将讨论基于中红外激光增益材料的方法，用于直接宽带中红外激光器或作为非线性晶体参数放大的窄带泵浦激光器。主要部分将侧重于基于参数变频的中红外生成和放大，从而实现最高的中红外峰值功率脉冲。最后，我们概述了非线性后压缩技术，用于将脉冲持续时间减少到亚 2 光周期机制。但通常不会产生短脉冲持续时间。将讨论基于中红外激光增益材料的方法，用于直接宽带中红外激光器或作为非线性晶体参数放大的窄带泵浦激光器。主要部分将侧重于基于参数变频的中红外生成和放大，从而实现最高的中红外峰值功率脉冲。最后，我们概述了非线性后压缩技术，用于将脉冲持续时间减少到亚 2 光周期机制。但通常不会产生短脉冲持续时间。将讨论基于中红外激光增益材料的方法，用于直接宽带中红外激光器或作为非线性晶体参数放大的窄带泵浦激光器。主要部分将侧重于基于参数变频的中红外生成和放大，从而实现最高的中红外峰值功率脉冲。最后，我们概述了非线性后压缩技术，用于将脉冲持续时间减少到亚 2 光周期机制。实现最高的中红外峰值功率脉冲。最后，我们概述了非线性后压缩技术，用于将脉冲持续时间减少到亚 2 光周期机制。实现最高的中红外峰值功率脉冲。最后，我们概述了非线性后压缩技术，用于将脉冲持续时间减少到亚 2 光周期机制。