Epitaxial Nd:YLF linear waveguide laser

We report laser operation in planar and linear Nd:YLF waveguide structures grown by liquid-phase epitaxy (LPE). We could reduce the relatively high threshold of 115-mW incident pump power observed for the planar waveguide to 8 mW in a ridge-type structure that we obtained by mechanical polishing and subsequent growth of a cladding layer. Substantial improvements seem possible with reduction of the losses caused by imperfect end-face reflection and scattering, as well as by use of techniques capable of producing smaller structures than the 40-microm-wide triangular ridge cross section that was obtained with polishing. Since the LPE technique is applicable to other activator ions as well, it might offer a route to development of low-threshold upconversion lasers.