Nonlinear optical imaging with mid-infrared light

To a molecular spectroscopist, mid-infrared (MIR) light is useful because it enables spectroscopic analysis of molecules based on their molecular fingerprints. To an optical microscopist interested in biological materials, working with MIR light is not particularly attractive. This is because the use of MIR radiation corresponds to lower spatial resolution, introduces problems with water absorption, and requires the use of noisy and inefficient MIR detectors. This presentation discusses several approaches that work around these perceived problems. We highlight several recent developments that leverage nonlinear optical phenomena, including second-order and third-order optical effects, which offer mechanisms for imaging with sub-micrometer spatial resolution and signal detection with simple and reliable photodetectors. These developments turn MIR-based imaging into a sensitive approach for the microscopic mapping of various biological samples.