Shaofen Gao

We demonstrate a very strong laser gain in the near UV, at 391 nm, involving one- and two-photon transitions between initial and final levels of the transition. This opens the way to the realization of all-optical lasers at short wavelengths. The amplifying medium is N2${}^{{\boldsymbol{+}}}$ at low density, pumped by an intense laser source at a longer wavelength, i.e., 800 nm.