Abstract The development of parametric devices down-converting the laser frequency to the mid-infrared (3–30 µm) based on non-oxide nonlinear optical crystals is reviewed. Such devices, pumped by solid-state laser systems operating in the near-infrared, fill in this spectral gap where no such lasers exist, on practically all time scales, from continuous-wave to femtosecond regime. All important results obtained so far with difference-frequency generation, optical parametric oscillation, generation and amplification are presented in a comparative manner, illustrating examples of recent achievements are given in more detail, and some special issues such as continuum and frequency comb generation or pulse shaping are also discussed. The vital element in any frequency-conversion process is the nonlinear optical crystal and this represents one of the major limitations for achieving high energies and average powers in the mid-infrared although the broad spectral tunability seems not to be a problem. Hence, an overview of the available non-oxide nonlinear optical materials, emphasizing new developments such as wide band-gap, engineered (mixed), and quasi-phase-matched crystals, is also included.

中文翻译：

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使用非氧化物非线性晶体将固态激光源降频到中红外光谱范围

摘要 综述了基于非氧化物非线性光学晶体将激光频率下变频至中红外 (3-30 µm) 的参量器件的发展。这种由在近红外波段工作的固态激光系统泵浦的设备填补了这个光谱空白，在那里没有这种激光器存在，几乎在所有时间尺度上，从连续波到飞秒范围。迄今为止在差频生成、光学参量振荡、生成和放大方面获得的所有重要结果都以比较的方式呈现，更详细地举例说明了最近的成就，以及一些特殊问题，例如连续谱和频率梳生成或脉冲还讨论了塑造。任何频率转换过程中的重要元素都是非线性光学晶体，这代表了在中红外实现高能量和平均功率的主要限制之一，尽管宽光谱可调性似乎不是问题。因此，还包括对可用非氧化物非线性光学材料的概述，重点介绍宽带隙、工程（混合）和准相位匹配晶体等新发展。