Min, WeiFreudiger, Christian WilhelmLu, SijiaXie, Xiaoliang2013-03-222011Min, Wei, Christian Wilhelm Freudiger, Sijia Lu, and Xiaoliang Sunney Xie. 2011. Coherent nonlinear optical imaging: Beyond fluorescence microscopy. Annual Review of Physical Chemistry 62:507-530.0066-426X1545-1593http://nrs.harvard.edu/urn-3:HUL.InstRepos:10461276The quest for ultrahigh detection sensitivity with spectroscopic contrasts other than fluorescence has led to various novel approaches to optical microscopy of biological systems. Coherent nonlinear optical imaging, especially the recently developed nonlinear dissipation microscopy (including stimulated Raman scattering and two-photon absorption) and pump-probe microscopy (including excited-state absorption, stimulated emission, and ground-state depletion), provides new image contrasts for nonfluorescent species. Thanks to the high-frequency modulation transfer scheme, these imaging techniques exhibit superb detection sensitivity. By directly interrogating vibrational and/or electronic energy levels of molecules, they offer high molecular specificity. Here we review the underlying principles and excitation and detection schemes, as well as exemplary biomedical applications of this emerging class of molecular imaging techniques.en-USlabel-free imagingcoherent Raman spectroscopystimulated Raman scattering microscopystimulated emission microscopypump-probe microscopyJournal Article2013-03-2210.1146/annurev.physchem.012809.103512