From N₂ (337 nm) to high-order harmonic generation: 40 years of coherent source development in the UV and VUV

An abbreviated history of the development of several selected coherent sources (primary and nonlinear) in the 100-400-nm spectral region over the past four decades is presented here. In this comparatively brief span of time, peak output powers in the UV have risen by more than eight orders of magnitude, and photons from the near-UV to the threshold of the soft X-ray region are now generated routinely at kilohertz repetition frequencies. A few of the milestones and individuals who contributed to this period of enormous progress will be discussed.