Dijkstra, M.

García Blanco, S.M.

Martinussen, S.M.

Mu, Jinfeng

van Emmerik, C.I.

English

NARCIS 

A novel polishing stop for accurate integration of potassium yttrium double tungstate on silicon dioxide

University of Twente Research Information

A novel polishing stop for accurate integration of potassium yttrium double tungstate on silicon dioxide C.I. van Emmerik1,*, S.M. Martinussen1, J.Mu1, Dijkstra1, and S.M. García-Blanco1,**RENOS Project Rare Earth Novel On-chip SourcesGoal: development of high-contrast waveguide fabrication technique in KY(WO4)21. Optical Sciences Group, MESA+ Institute for Nanotechnology, University of Twente, The Netherlands *     E-mail: c.i.vanemmerik@utwente.nl**   E-mail: s.m.garciablanco@utwente.nlWhy?• High refractive index (n≈2 @ 1550 nm)• Long inter-ionic distance for RE ions (<d>≈0.5 nm) [1]and high cross-sections for RE ions [2]• High Raman yield [3]Challenges• Impossible to grow on most substrates• Small waveguide dimensions• Defect free layersRequirements• Round beveled KYW edges(to avoid chipping of the edges)• Low temperature adhesive• High precision (± 0.1 µm) z-direction[1] M. C. Pujol, X. Mateos, R. Sole, J. Massons, J. Gavalda, X. Solans, F. Dı´az, and M. Aguilo, “Structure, crystal growth and physical anisotropy of KYb(WO4)2, a new laser matrix,” J. Appl. Crystal- logr., no. 35, pp. 108–112, 2002.[2] Y.-S. Yong, S. Aravazhi, S. A. Vázquez-Córdova, J. J. Carjaval, F. Díaz, J. L. Herek, S. M. García-Blanco, and M. Pollnau, “Temperature-dependent absorption and emission of potassium double tungstates with high ytterbium content,” Opt. Express, vol. 24, no. 23, p. 26825, Nov. 2016.[3] A. A. Kaminskii, A. F. Konstantinova, V. P. Orekhova, A. V Butashin, R. F. Klevtsova, and A. A. Pavlyuk, “Optical and nonlinear laser properties of the χ(3)-active monoclinic α-KY(WO4)2 crystals,” Crystallogr. Reports,         vol. 46, no. 4, pp. 665–672, Jul. 2001..Requirements• Hard material• Room temperature process(to minimize stress due to CTE mismatch of the layers)• High precision (Hlayer ≈ 1.0 ± 0.1 µm)Polishing stopFabrication of polishing stopThinningResultsBondingStage MaterialGrinding 400/ 800/ 1000 SiC pasteLapping 9/ 3/ 1 µm Al2O3 suspension on cast iron diskPolishing 3 µm CeO2 / 40 nm SiO2 on polyurethane diskProcessPulsed laser depositionof e.g. TiO2, Al2O3 at ~25 oC• Layer as thin as the polishing stop• Acceptable planarity• Reduction of polishing speed by 3-4 times• Higher yield expected• Increase surface quality (RMS < 2.0 nm) for low transmission losses• Etching of waveguides on thin layerOutlookFinetech Fineplacer Lamda precision flip-chip bonder with 0.5 µm X-Y positioning accuracy.Schematic representation of a bonded KYW sample with the polishing stop.Logitech PM5 precision lapping and polishing systemHybrid integration of KY(WO4)2Material• KY(WO4)2 crystal 1.0 cm by 1.0 cm, 1.0 mm thick• SiO2 substrate 2.0 cm by 2.0 cm, 0.5 mm thickGoal• Hybrid integration of KY(WO4)2 crystal with a final layer thickness of ~1 µm.KY(WO4)2 bonded on a SiO2 substrate with 6.0 µm  wide pillars separated 500.0 µm

A novel polishing stop for accurate integration of potassium yttrium double tungstate on silicon dioxide

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