Design and fabrication of compact Ge-on-SOI coupling structure

Abstract

In this paper, we have proposed and demonstrated a simple approach to fabricate vertical integrated structure for coupling between active germanium (Ge) waveguide and silicon-on-insulator (SOI) waveguide. The active Ge waveguide is sputtered after etching the underlying passive silicon (Si) waveguide. This method scuttles away from the difficulty involved in the waveguide fabrication by avoiding the etching process for the Ge waveguide, and thereby the waveguide quality is improved. The influences of the coupling structural parameters on the coupling loss are analyzed and discussed. The optimizing parameters are obtained for the fabrication. The minimal coupling loss is experimentally measured about 2.37 dB, and variation tendency of coupling loss against the structural parameters is consistent with the theoretical result. The proposed approach offers an effective path for vertical coupling between Ge and SOI optical components.

Keywords

taper coupler / integrated optics device / guided waves / silicon-on-insulator (SOI) waveguide / germanium (Ge) waveguide / active Ge device / Ge-on-SOI coupling structure

References

[1] Liu J, Sun X, Camacho-Aguilera R, Kimerling L C, Michel J. Ge-on-Si laser operating at room temperature. Optics Letters, 2010, 35(5): 679–681

[2] Ren S, Rong Y, Claussen S A, Schaevitz R K, Kamins T I, Harris J S, Miller D A B. Ge/SiGe quantum well waveguide modulator monolithically integrated with SOI waveguides. IEEE Photonics Technology Letters, 2012, 24(6): 461–463

[3] Liu J, Pan D, Jongthammanurak S, Wada K, Kimerling L C, Michel J. Design of monolithically integrated GeSi electro-absorption modulators and photodetectors on a SOI platform. Optics Express, 2007, 15(2): 623–628

[4] Dong P, Kirk A G. Compact double-grating coupler between vertically stacked silicon-on-insulator waveguides. Applied Optics, 2005, 44(35): 7540–7547

[5] Lu Z. Efficient fiber-to-waveguide coupling through the vertical leakage from a microring. Optics Letters, 2007, 32(19): 2861–2863

[6] Vusirikala V, Saini S S, Bartolo R E, Agarwala S, Whaley R D, Johnson F G, Stone D R, Dagenais M. 1.55-mm InGaAsP-InP laser arrays with integrated-mode expanders fabricated using a single epitaxial growth. IEEE Journal of Quantum Electronics, 1997, 3(6): 1332–1343

[7] Lamponi M, Keyvaninia S, Jany C, Poingt F, Lelarge F, de Valicourt G, Roelkens G, Van Thourhout D, Messaoudene S, Fedeli J M, Duan G H. Low-threshold heterogeneously integrated InP/SOI laser with a double adiabatic taper coupler. IEEE Photonics Technology Letters, 2012, 24(1): 76–78

[8] Bauters J F, Davenport M L, Heck M J R, Doylend J K, Chen A, Fang A W, Bowers J E. Silicon on ultra-low-loss waveguide photonic integration platform. Optics Express, 2013, 21(1): 544–555

[9] Zhou H, Sun J, Gao J, Jiang J, Zhou Y. Design of compact and efficient polarization-insensitive taper coupler for SiGe photonic integration. Optics Express, 2016, 24(21): 23784–23797

[10] Kwon M S, Shin J S, Shin S Y, Lee W G. Characterizations of realized metal-insulator-silicon-insulator-metal waveguides and nanochannel fabrication via insulator removal. Optics Express, 2012, 20(20): 21875–21887

[11] Liu J, Beals M, Pomerene A, Bernardis S, Sun R, Cheng J, Kimerling L C, Michel J. Waveguide-integrated, ultra-low energy GeSi electro-absorption modulators. Nature Photonics, 2008, 2(7): 433–437

[12] Gao J, Sun J, Jiang J, Zhou H, Zhou Y. Design and analysis of electro-absorption modulators with uniaxially stressed Ge/SiGe multiple quantum wells. Optics Express, 2017, 25(10): 10874–10884

[13] Feng D, Liao S, Dong P, Feng N, Liang H, Zheng D, Kung C, Fong J, Shafiiha R, Cunningham J, Krishnamoorthy A V, Asghari M. High-speed Ge photodetector monolithically integrated with large cross-section silicon-on-insulator waveguide. Applied Physics Letters, 2009, 95(26): 261105

[14] Fidaner O, Okyay A K, Roth J E, Schaevitz R K, Kuo Y H, Saraswat K C, Harris J S, Miller D A B. Ge-SiGe quantum-well waveguide photodetectors on silicon for the near-infrared. IEEE Photonics Technology Letters, 2007, 19(20): 1631–1633

[15] Palik E D. Handbook of Optical Constants of Solids. New York: Academic Press, 1985

[16] Lee C W, Chin M K, Iyer M K, Popov A. Asymmetric waveguides vertical couplers for polarization-independent coupling and polarization modes splitting. Journal of Lightwave Technology, 2005, 23(4): 1818–1827

[17] Lee C W. A review of polarization dependence applications for asymmetric waveguides vertical couplers in compound semiconductor indium phosphide. International Journal of Optics, 2011, 2011: 164023

[18] Gassenq A, Guilloy K, Osvaldo Dias G, Pauc N, Rouchon D, Hartmann J M, Widiez J, Tardif S, Rieutord F, Escalante J, Duchemin I, Niquet Y M, Geiger R, Zabel T, Sigg H, Faist J, Chelnokov A, Reboud V, Calvo V. 1.9% bi-axial tensile strain in thick germanium suspended membranes fabricated in optical germanium-on-insulator substrates for laser applications. Applied Physics Letters, 2015, 107(19): 191904

[19] Sukhdeo D S, Nam D, Kang J H, Brongersma M L, Saraswat K C. Direct bandgap germanium-on-silicon inferred from 5.7% 〈100〉 uniaxial tensile strain. Photonics Research, 2014, 2(3): A8–A13

[20] Fedeli J M, Cioccio L D, Marris-Morini D, Vivien L, Orobtchouk R, Rojo-Romeo P, Seassal C, Mandorio F. Development of silicon photonics devices using microelectronic tools for the integration on top of a CMOS wafer. Advances in Optical Technologies 2008, 2008: 412518

[21] Liu H C, Lin Y H, Hsu W. Sidewall roughness control in advanced silicon etch process. Microsystem Technologies, 2003, 10(1): 29–34

[22] Sökmen Ü, Stranz A, Fündling S, Merzsch S, Neumann R, Wehmann H H, Peiner E, Waag A. shallow and deep dry etching of silicon using ICP cryogenic reactive ion etching process. Microsystem Technologies, 2010, 16(5): 863–870

[23] Okada T, Fujimori J, Aida M, Fujimura M, Yoshizawa T, Katsumura M, Iida T. Enhanced resolution and groove-width simulation in cold development of ZEP520A. Journal of Vacuum Science & Technology B Microelectronics and Nanometer Structures, 2011, 29(2): 021604

[24] Pudiš D, Šušlik L, Kubicová I, Škriniarová J, Martinček I. Advanced optical methods for patterning of photonic structures in photoresist, III–V semiconductors and PMMA. In: Proceedings of 17th Slovak-Czech-Polish Optical Conference on Wave and Quantum Aspects of Contemporary Optics. 2010, 774608

Acknowledgements

This work was supported by the National Natural Science Foundation of China (NSFC) (Grant No. 61435004).

RIGHTS & PERMISSIONS

2018 Higher Education Press and Springer-Verlag GmbH Germany, part of Springer Nature