Engineering lattice matching, doping level, and optical properties of KY(WO4)2:Gd, Lu, Yb layers for a cladding-side-pumped channel waveguide laser
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Single-crystalline KY1−x−y−z GdxLuyYbz(WO4)2 layers are grown onto undoped KY(WO4)2 substrates by liquid-phase epitaxy. The purpose of co-doping the KY(WO4)2 layer with suitable fractions of Gd3+ and Lu3+ is to achieve lattice-matched layers that allow us to engineer a high refractive-index contrast between waveguiding layer and substrate for obtaining tight optical mode confinement and simultaneously accommodate a large range of Yb3+ doping concentrations by replacing Lu3+ ions of similar ionic radius for a variety of optical amplifier or laser applications. Crack-free layers, up to a maximum lattice mismatch of ~0.08 %, are grown with systematic variations of Y3+, Gd3+, Lu3+, and Yb3+ concentrations, their refractive indices are measured at several wavelengths, and Sellmeier dispersion curves are derived. The influence of co-doping on the spectroscopy of Yb3+ is investigated. As evidenced by the experimental results, the lattice constants, refractive indices, and transition cross-sections of Yb3+ in these co-doped layers can be approximated with good accuracy by weighted averages of data from the pure compounds. The obtained information is exploited to fabricate a twofold refractive-index-engineered sample consisting of a highly Yb3+-doped tapered channel waveguide embedded in a passive planar waveguide, and a cladding-side-pumped channel waveguide laser is demonstrated.
KeywordsLattice Mismatch Planar Waveguide Channel Waveguide Grown Layer Refractive Index Contrast
The authors thank A. Hollink for technical assistance with the growth setup, Yaroslav E. Romanyuk for helpful discussions, and Martin Krejci from Oclaro Inc. for providing the diode bar. This project was financially supported by The Netherlands Organization for Scientific Research (NWO) through the VICI Grant no. 07207 “Photonic integrated structures”.
- 11.S.V. Borisov, R.F. Klevtsova, Crystal structure of KY(WO4)2. Sov. Phys. Crystallogr. 13, 420–421 (1968). (Transl.: Kristallografiya 13, 517-519 (1968))Google Scholar
- 15.Y.E. Romanyuk, Liquid-phase epitaxy of doped KY(WO4)2 layers for waveguide lasers. Ph.D. thesis, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland (2006)Google Scholar
- 16.P.V. Klevtsov, L.P. Kozeeva, R.F. Klevtsova, Crystallographic study of potassium-yttrium tungstate and molybdate. Izv. Akad. Nauk SSSR Neorgan. Mater. 4, 1147–1151 (1968)Google Scholar
- 25.D. Geskus et al. Highly efficient channel waveguide laser at the 981-nm zero-line of Yb3+. (are preparing a manuscript)Google Scholar
- 41.L.J. McKnight, S. Calvez, Gain-guided KYb(WO4)2 laser, in Digest of Europhoton Conference 2010, Europhysics Conference Abstract Vol. 34C (European Physical Society, Mulhouse, 2010), p. 24, paper WeP19Google Scholar