Ongoing progress in micro- and nano-material fabrication has led to novel devices and new optical properties have emerged. Among these properties are high optical nonlinearities, which can be used for light-based operations such as frequency shifting and optical computing. Optimizing and utilizing optical nonlinearities requires sensitive instruments to study them. Given the miniature sizes of the new materials under study, conventional analysis approaches may be insufficient, thus putting an emphasis on emerging technologies. Four-wave mixing (FWM) microscopy is a budding technique that is poised to become a useful tool in materials science. FWM microscopy provides a fast eye for spotting small structures and uncovering their material properties. The FWM signal derives its selectivity from material-specific electronic resonances and Raman transitions, providing an optical microscope that is attuned to visualizing and studying a broad range of micro- and nano-structured materials. In this article, the basics of FWM microscopy are discussed and the impact of this technique in materials science is highlighted.

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DOI: 10.1016/j.mattod.2013.08.001