Abstract

Recently, we have demonstrated down-conversion laser operation in planar and linear Nd:LiYF₄(YLF) waveguide structures grown by liquid phase epitaxy (LPE) [1,2]. However, a first device of a one-dimensional geometry was obtained by subsequent mechanical polishing steps followed by the growth of a cladding layer. Substantial improvement seems possible by an exploration of different surface structuring techniques in order to reduce the cross-section down to about 5×5 μm at a length of 1 to 1.5 cm. Current work to be presented includes (i) an exploration of chemical polishing agents, (ii) ion etching or laser ablation for a pre-(I) or post­structuring (II) procedure. Further activities comprise high energy ion implantation. YLF substrates are obtained by a vertical gradient freezing technique. Because of the phase diagram of pure YLF, the process of LPE is restricted to operate rather at a low ratio of LiF / YF₃ varying in the range of 3/2 to about 1/2. Controlling the thickness of an active layer down to ~5 μm is hence demanding with respect to the control of temperature (ΔT < 0.5 - 1.0 °C). Because of this the present LPE approach includes one polishing step (see I, II). An alternative avoiding polishing at any intermediate step would lower the YLF concentration in the liquid phase in order to decrease the growth speed (LiF/LiCl-flux).

© 1998 IEEE