Quasi-phase-matching of momentum and energy in nonlinear optical processes

Quasi-phase-matching (QPM) has always been thought of as a purely spatial phenomenon. Now, scientists show that QPM can be extended to the temporal domain, introducing temporal and spatiotemporal modulations of the nonlinear susceptibility. This concept paves the way for the manipulation of light through nonlinear interactions, and may have unique applications in nonlinear optics.