Structuring of LiYF4 for 1-D waveguide laser investigations by chemical wet etching techniques

In the course of the structuring of YLF substrates for waveguide investigat ions, close to 300 chemical wet etchants have been tested. Thereof, only (i ) H2SO4 (IM)/Al(NO3)(3) (0.5M), (ii) HNO3 (2M)/FeCl3 (0.5M), (iii) HNO3 (2M )/ZrOCl2 (0.5M), (iv) HI (2M)/VCl3 (0.5M), (v) HI (2M)/ZrOCl3 (0.5M), (vi) HBr (2M)/FeCl3 (0.5M), (vii) HBr (2M)/GaOOH (saturated) and (viii) HBr (2M) /FeCl3 (0.5M) gave surface roughnesses of similar to 100 nm or lower on a-f aces. a-faces were etched 2-4 times faster than c-faces. It could be shown that a thermal treatment (annealing) prior to etching has a significant inf luence on the etching behaviour. Evidence for a surface transformation duri ng annealing could be found. Besides wet chemical etching, preliminary resu lts on laser ablation and ion beam etching (IBE) are promising in the case of IBE. For the first time, photolithography and chemical wet etching have produced grooves of 5-7 x 3-4 mu m on chromium-coated YLF substrates. Using IBE, ridges of 2, 3, 5 and 10 mu m width and similar to 3 mu m height have been fabricated. (C) 1999 Elsevier Science B.V. All rights reserved.