Coherent Nonlinear Optical Microscopy with Mid-infrared Radiation

Fundamental vibrational modes are efficiently excited by mid-infrared (MIR) radiation, in a light-matter interaction that is many orders of magnitude stronger than vibrational excitation through the Raman effect. Despite this clear advantage, MIR microscopy is not ubiquitously used for imaging of biological samples due to practical limitations including low spatial resolution, the use of expesensive cameras and the intrinsic limitation of absoprtion-based detection. Some of these limitations can be overcome when using nonlinear upconversion techniques to translate the driven MIR transition into a signal in the visible/NIR range of the spectrum. We will discuss several coherent nonlinear optical approaches that enable rapid laser-scanning microscopy in the MIR with high, three-dimensional resolution.