Optical gain at 1.06 μm in the neodymium chloride-aluminum chloride vapor complex

First observation of optical gain for trivalent rare-earth molecular vapors is reported. Specifically, gain coefficients a few tenths percent/cm have been measured in the neodymium chloride—aluminum chloride vapor complex at 1.06 μm for the Nd3+ : 4F3/2→4I11/2 transition. The corresponding stored energy density at this wavelength is ≈35 J/l. The observed inversion lifetime of ≳10 μsec is interpreted to be dominated by near-resonant excited-state–excited-state binary collisions. Use of trivalent rare-earth molecular vapors as gain media in fusion laser amplifiers is discussed.