  Although the first lasers invented operated in the visible, the first on-chip
devices were optimized for near-infrared (IR) performance driven by demand in
telecommunications. However, as the applications of integrated photonics has
broadened, the wavelength demand has as well, and we are now returning to the
visible (Vis) and pushing into the ultraviolet (UV). This shift has required
innovations in device design and in materials as well as leveraging nonlinear
behavior to reach these wavelengths. This review discusses the key nonlinear
phenomena that can be used as well as presents several emerging material
systems and devices that have reached the UV-Vis wavelength range.
