
3
e growing availability of turnkey ultrafast laser sources has fueled a revolution in optical micros-
copy, with second-harmonic generation (SHG) imaging emerging as a powerful probe for local order.
e coherent nature of SHG results in high specicity for certain classes of ordered structures, oen
producing virtually no detectable background from disordered media. Consequently, image contrast
is unique from that achievable using conventional optical methods. SHG has been used, and promises
to provide continued insight, in the study of a wide variety of ordered systems, such as cells, organelles,
tissues, complex surfaces, and other chira