Nonlinear Optics with Two-Colour Lasers

激光在50年前改变了光学研究，现在已经产生了无数的应用。 激光器工作在从红外到紫外的许多波长，但要完全覆盖光谱，就需要非线性光学。超短脉冲激光器现在可以通过称为光学整流的非线性过程产生远红外辐射，并且可以通过高次谐波产生非线性地驱动频率直到极紫外线。然而，一些光谱间隙仍然存在，该提案旨在填补6至25µm的“分子指纹”光谱区域，其中几乎每个分子在其吸收光谱中都有独特的特征。 沿着在环境监测和医疗应用中的应用，该光谱区域对于在这些波长处具有强吸收线的爆炸物的痕量气体检测变得越来越重要。在滑铁卢，我们正在开发一种双色短脉冲光纤激光系统，该系统将通过在非线性晶体中对两种激光输出进行差频混合，产生跨越指纹区域的中红外波长，具有足够的功率用于痕量气体检测。

Lasers transformed optics research 50 years ago and have now spawned innumerable applications. Lasers operate at many wavelengths from the infrared to the ultraviolet, but to completely cover the optical spectrum, nonlinear optics is needed. Ultrashort pulse lasers can now generate far-infrared radiation through a nonlinear process known as optical rectification and can nonlinearly drive the frequency up to the extreme ultraviolet by high order harmonic generation. However, some spectral gaps still exist and this proposal aims to fill in the "molecular fingerpint" spectral region from 6 to 25µm, where almost every molecule has a distinctive signature in its absorption spectra. Along with applications in environmental monitoring and medical applications, this spectral region is becoming increasingly important for trace gas detection of explosives that have strong absorption lines at these wavelengths. At Waterloo, we are developing a two-colour, short pulse fiber laser system, which will generate mid-infrared wavelengths across the fingerprint region with sufficient power for trace gas detection, by difference frequency mixing the two laser outputs in a nonlinear crystal.