Fabrication of y-splitters and Mach-Zehnder structures on (Yb,Nb):RbTiOPO₄/RbTiOPO₄ epitaxial layers by reactive ion etching

Butt, M.A., Solé, R., Pujol, M.C., Ródenas, A., Lifante, G., Choudhary, A., Murugan, G.S., Shepherd, D.P., Wilkinson, J.S., Aguiló, M. and Díaz, F. (2015) Fabrication of y-splitters and Mach-Zehnder structures on (Yb,Nb):RbTiOPO₄/RbTiOPO₄ epitaxial layers by reactive ion etching. Journal of Lightwave Technology, 33 (9), 1863-1871. (doi:10.1109/JLT.2014.2379091).

Abstract

Reactive ion etching of RbTiOPO₄ (001) substrates and (Yb,Nb):RbTiOPO₄/RbTiOPO₄ (001) epitaxial layers has been performed using fluorine chemistry. A maximum etch rate of 8.7 nm/min was obtained, and the deepest etch achieved was 3.5 µm. The (Yb,Nb)-doped epitaxial layers showed a slower etching rate when compared with undoped material. Liquid phase epitaxial growth of cladding layers has also been performed, resulting in a high-quality interface growth without appreciable defects. 9-mm-long Mach Zehnder interferometer (MZI) and 9-mm-long Y-splitter structures were designed and patterned in RbTiOPO₄ substrates and (Yb,Nb):RbTiOPO₄/RbTiOPO₄ (001) epitaxial layers. The structures fabricated in RbTiOPO₄ substrates were filled with laser active (Yb,Nb):RbTiOPO₄ higher refractive index core material, and finally an RbTiOPO₄ cladding was grown on the samples. The refractive index difference between the (Yb,Nb):RbTiOPO₄ layer and the RbTiOPO₄ substrate at 1.5 µm has been measured and optical waveguiding at this wavelength has been demonstrated.

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Contributors

Author: G.S. Murugan

Author: D.P. Shepherd

Author: J.S. Wilkinson

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