  We present laser results obtained from a Dy$^{3+}$-Tb$^{3+}$ co-doped
LiLuF$_{4}$ crystal, pumped by a blue emitting InGaN laser diode, aiming for
the generation of a compact 578 nm source. We exploit the yellow Dy$^{3+}$
transition $^{4}$F$_{9/2}$ $\Longrightarrow$ $^{6}$H$_{13/2}$ to generate
yellow laser emission. The lifetime of the lower laser level is quenched via
energy transfer to co-doped Tb$^{3+}$ ions in the fluoride crystal. We report
the growth technique, spectroscopic study and room temperature continuous wave
(cw) laser results in a hemispherical cavity at 574 nm and with a highly
reflective output coupler at 578 nm. A yellow laser at 578 nm is very relevant
for metrological applications, in particular for pumping of the forbidden
$^{1}$S$_{0} \Longrightarrow ^{3}$P$_{0}$ Ytterbium clock transition, which is
recommended as a secondary representation of the second in the international
system (SI) of units. This paper was published in Optics Letters and is made
available as an electronic reprint with the permission of OSA. The paper can be
found at the following URL on the OSA website:
http://dx.doi.org/10.1364/OL.39.006628. Systematic or multiple reproduction or
distribution to multiple locations via electronic or other means is prohibited
and is subject to penalties under law.
