Laser emission at 413 and 730 nm in upconversion-pumped YLiF 4 :Nd 3+

Recently, there has been considerable progress in the development of rare-earth lasers pumped by upconversion excitation.1-4 In particular, laser operation at visible wavelengths shorter than those of the pump was demonstrated in YAlO3:Er3+ and YLiF4:Er3+ at 550 nm,1 and in LaF3:Nd3+ at 380 nm4 using either sequential two-photon absorption or energy transfer processes for upconversion pumping. Here we report two new laser transitions of the neodymium ion at 413.0 and 729.5 nm using upconversion pumping of YLiF4:Nd3+ at low temperatures.