Very low threshold green lasing in microspheres by up-conversion of IR photons

Abstract

A green up-conversion laser is demonstrated in a 120 µm diameter microsphere of Er 3+-doped ZBLAN at room temperature. Lasing occurs around 540 nm with a 801 nm diode laser pump. The lasing threshold of only 30 µW of absorbed power is over two orders of magnitude lower than the lowest previously observed in IR-visible up-conversion lasing (Funk D S et al 1997 Electron. Lett. 33 1958-60).