Development of infrared imaging using degenerate four wave mixing

激光光谱二维成像（2D-imaging，简称2D-imaging）是研究物质在燃烧、等离子体等化学环境中的行为的一种非常有效的技术。然而，由于缺乏快速、灵敏的成像设备，红外波长区域的2d成像受到限制。为了克服这个问题，我们提出了红外DFWM图像的频率上转换检测，用于气相物种分布的可视化。通过在背景气体中激光烧蚀产生的膨胀的Cs羽流的可视化，证明了该系统的能力。对该系统的保真度进行了数值和实验研究。本方案可以很容易地扩展到中红外区域，通过采用市上可用的光学参量振荡器作为DFWM的泵浦源，并采用合适的非线性晶体（如KTP）代替B=BBO。

Laser-spectroscopic two-dimensional imaging(2D-imaging)is a very powerful technique for the investigation of the species behavior in the chemical environments such as combustion, plasma and so on. However, 2D-imaging in the infrared wavelength region is limited due to a lack of a fast, sensitive imaging device. To overcome this problem, We have proposed the frequency up-conversion detection of IR DFWM images for the visualization of species distribution in the gas phase. The ability of the present system has been demonstrated by visualizing an expanding Cs plume generated by the laser ablation in a background gas. The fidelity of the proposed system has been investigated numerically and experimentally.The present scheme can be easily extended into the mid-infrared region by employing a commercially available optical parametric oscillator as a pump source for DFWM and a suitable nonlinear crystal such as KTP instead of B=BBO.