Second-harmonic generation imaging microscopy with ps pulsed lasers

Second harmonic generation (SHG) imaging microscopy is a nonlinear optical imaging technique that uses SHG as a contrast mechanism to produce high-resolution images. SHG occurs in materials with non-centrosymmetric crystal structures. Therefore, SHG imaging has been applied for characterization of 2D semiconductors, transition-metal dichalcogenides (TMDs) such as WS2 and MoSe2, lithium niobate crystals, PZT thin films, graphene, lanthanides, and even biological tissues. It provides information on the crystal lattice, assesses crystal quality and maps grain boundaries, defects, and mechanical strain. Furthermore, SHG imaging reveals the number of stacked layers as well as their orientation with respect to each other.