Er 3+ and Yb 3+ doped active media for ‘eye safe’ laser systems

Abstract

There is considerable interest in compact pulsed high peak power laser sources emitting at wavelengths near 1.55 μm. Rangefinders and other applications with free space propagation could be a benefit of such devices. The wavelength of around 1.55 μm is in the eyesafe regime where significantly higher pulse energies can be used without damaging human eyes. Erbium- and ytterbium-doped YAG single crystals were obtained by the Czochralski method. The basis conditions of growth and the results of optical homogeneity measurements of the obtained crystals are presented. This report describes also the effect of variations of erbium, ytterbium, chromium ions and glass base compositions on laser efficiency and the improved properties of a new glass base. The spectral properties and laser characteristics were investigated. Absorption spectra of Er 3+- and Yb 3+-doped active media were measured in the spectral range 190 to 5000 nm at room temperature. Excitation and luminescence spectra were also recorded at room temperature with a Jobin-Yvon spectrofluorometer using a diode laser (Polaroid 4300, 980 nm, 1 W) as an excitation source. The measurements of the lifetime of the Er 3+ ions in the upper laser level ( 4I 13/2) of the samples were made by the direct method with pulse excitation.