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  • Print publication year: 2015
  • Online publication date: April 2015

5 - Optical I/O

from Part II - Passive Components

Summary

In this chapter, we describe the design of these two types of optical input/output coupling techniques: fibre grating couplers in Section 5.2, and edge couplers in Section 5.3. A method of creating a mask layout for a focusing grating coupler is presented. Methods for polarization management are also discussed in Section 5.4.

The challenge of optical coupling to silicon photonic chips

Owing to the large refractive index contrast between the silicon core (n = 3.47 at 1550 nm) and the silicon dioxide cladding (n = 1.444 at 1550 nm), propagation modes are highly confined within the waveguide with dimensions on the order of a few hundred nanometers (see Sections 3.1 and 3.2). Although a benefit for large-scale integration, the small feature size of the waveguide raises the problem of a huge mismatch between the optical mode within an optical fibre and the mode within the waveguide. The cross-sectional area of an optical fibre core (with a diameter of 9°m) is almost 600 times larger than that of a silicon waveguide (with dimensions of 500 nm × 220 nm), hence requires components that adjust the mode-field diameter accordingly.

Several approaches have been demonstrated to tackle the problem of the aforementioned mode mismatch. Edge coupling using spot-size converters and lensed fibres is one solution used to address this, and high-efficiency coupling with an insertion loss below 0.5 dB has been demonstrated [1]. In addition, both TE and TM polarizations can be efficiently coupled. However, this approach can only be used at the edge of the chips, and the implementation of such designs requires complicated post-processes and high-resolution optical alignment, which increase the packaging cost.

Grating couplers are an alternative solution to tackle the issue of mode mismatch. Compared to the edge coupling, grating couplers have several advantages: alignment to grating couplers during measurement is much easier than alignment to edge couplers; the fabrication of grating couplers does not require post-processing, which reduces the fabrication cost; grating couplers can be put anywhere on a chip, which provides flexibility in the design as well as enabling wafer-scale automated testing.

[1] Sharee, McNab, Nikolaj, Moll, and Yurii, Vlasov. “Ultra-low loss photonic integrated circuit with membrane-type photonic crystal waveguides”. Optics Express 11.22 (2003), pp. 2927–2939 (cit. on pp. 162, 164).
[2] A., Mekis, S., Abdalla, D., Foltz, et al. “A CMOS photonics platform for high-speed optical interconnects”. Photonics Conference (IPC). IEEE. 2012, pp. 356–357 (cit. on pp. 162, 164).
[3] Wissem Sfar, Zaoui, Andreas, Kunze, Wolfgang, Vogel, et al. “Bridging the gap between optical fibers and silicon photonic integrated circuits”. Optics Express 22.2 (2014), pp. 1277–1286. DOI: 10.1364/OE.22.001277 (cit. on pp. 162, 164).
[4] Dirk, Taillaert, Harold, Chong, Peter I., Borel, et al. “A compact two-dimensional grating coupler used as a polarization splitter”. IEEE Photonics Technology Letters 15.9 (2003), pp. 1249–1251 (cit. on p. 162).
[5] N., Na, H., Frish, I. W., Hsieh, et al. “Efficient broadband silicon-on-insulator grating coupler with low back-reflection”. Optics Letters 36.11 (2011), pp. 2101–2103 (cit. on p. 164).
[6] D., Vermeulen, Y., De Koninck, Y., Li, et al. “Reflectionless grating coupling for silicon-on-insulator integrated circuits”. Group IV Photonics (GFP). IEEE. 2011, pp. 74–76 (cit. on p. 164).
[7] D., Taillaert, F., Van Laere, M., Ayre, et al. “Grating couplers for coupling between optical fibers and nanophotonic waveguides”. Japanese Journal of Applied Physics 45.8A (2006), pp. 6071–6077 (cit. on pp. 164, 179).
[8] D., Vermeulen, S., Selvaraja, P., Verheyen, et al. “High-efficiency fiber-to-chip grating couplers realized using an advanced CMOS-compatible silicon-on-insulator platform”. Optics Express 18.17 (2010), pp. 18278–18283 (cit. on pp. 164, 179).
[9] X., Chen, C., Li, C. K. Y., Fung, S. M. G., Lo, and H. K., Tsang. “Apodized waveguide grating couplers for efficient coupling to optical fibers”. Photonics Technology Letters, IEEE 22.15 (2010), pp. 1156–1158 (cit. on p. 164).
[10] G., Roelkens, D., Vermeulen, S., Selvaraja, et al. “Grating-based optical fiber interfaces for silicon-on-insulator photonic integrated circuits”. IEEE Journal of Selected Topics in Quantum Electronics 99 (2011), pp. 1–10 (cit. on p. 164).
[11] A., Mekis, S., Gloeckner, G., Masini, et al. “A grating-coupler-enabled CMOS photonics platform”. IEEE Journal of Selected Topics in Quantum Electronics 17.3 (2011), pp. 597–608. DOI: 10.1109/JSTQE.2010.2086049 (cit. on pp. 164, 180).
[12] Attila, Mekis, Sherif, Abdalla, Peter M. De, Dobbelaere, et al. “Scaling CMOS photonics transceivers beyond 100 Gb/s”. SPIE OPTO. International Society for Optics and Photonics. 2012, 82650A–82650A (cit. on p. 164).
[13] Yun, Wang, Jonas, Flueckiger, Charlie, Lin, and Lukas, Chrostowski. “Universal grating coupler design”. Proc. SPIE 8915 (2013), 89150Y. DOI: 10. 1117/12.2042185 (cit. on pp. 168, 170).
[14] F., Van Laere, T., Claes, J., Schrauwen, et al. “Compact focusing grating couplers for silicon-on-insulator integrated circuits”. IEEE Photonics Technology Letters 19.23 (2007), pp. 1919–1921 (cit. on pp. 168, 179).
[15] R., Waldhusl, B., Schnabel, P., Dannberg, et al. “Efficient coupling into polymer waveguides by gratings”. Applied Optics 36.36 (1997), pp. 9383–9390 (cit. on p. 179).
[16] Yun, Wang. “Grating coupler design based on silicon-on-insulator”. MA thesis. University of British Columbia, 2013 (cit. on p. 182).
[17] Tom, Baehr-Jones, Ran, Ding, Ali, Ayazi, et al. “A 25 Gb/s silicon photonics platform”. arXiv:1203.0767v1 (2012) (cit. on p. 182).
[18] Na, Fang, Zhifeng, Yang, Aimin, Wu, et al. “Three-dimensional tapered spot-size converter based on (111) silicon-on-insulator”. IEEE Photonics Technology Letters 21.12 (2009), pp. 820–822 (cit. on p. 182).
[19] Minhao, Pu, Liu, Liu, Haiyan, Ou, Kresten, Yvind, and Jorn M, Hvam. “Ultra-low-loss inverted taper coupler for silicon-on-insulator ridge waveguide”. Optics Communications 283.19 (2010), pp. 3678–3682 (cit. on p. 182).
[20] V. R., Almeida, R. R., Panepucci, and M., Lipson. “Nanotaper for compact mode conversion”. Optics Letters 28.15 (2003), pp. 1302–1304 (cit. on p. 183).
[21] B., Ben Bakir, A. V., de Gyves, R., Orobtchouk, et al. “Low-loss (< 1 dB) and polarization-insensitive edge fiber couplers fabricated on 200-mm silicon-on-insulator wafers”. IEEE Photonics Technology Letters 22.11 (2010), pp. 739–741. DOI: 10.1109/LPT.2010.2044992 (cit. on pp. 183, 189).
[22] Jens H., Schmid, Przemek J., Bock, Pavel, Cheben, et al. “Applications of subwavelength grating structures in silicon-on-insulator waveguides”. OPTO. International Society for Optics and Photonics. 2010, 76060F–76060F (cit. on p. 183).
[23] R., Takei, M., Suzuki, E., Omoda, et al. “Silicon knife-edge taper waveguide for ultralow-loss spot-size converter fabricated by photolithography”. Applied Physics Letters 102.10 (2013), p. 101108 (cit. on p. 183).
[24] Tai, Tsuchizawa, Koji, Yamada, Hiroshi, Fukuda, et al. “Microphotonics devices based on silicon microfabrication technology”. IEEE Journal of Selected Topics in Quantum Electronics, 11.1 (2005), pp. 232–240 (cit. on pp. 183, 189, 190).
[25] Tymon, Barwicz, Michael R., Watts, Milos A., Popovi, et al. “Polarization-transparent microphotonic devices in the strong confinement limit”. Nature Photonics 1.1 (2007), pp. 57–60 (cit. on pp. 190, 191).
[26] Thierry, Pinguet, Steffen, Gloeckner, Gianlorenzo, Masini, and Attila, Mekis. “CMOS photonics: a platform for optoelectronics integration”. In Silicon Photonics II. Ed. David J., Lockwood and Lorenzo, Pavesi. Vol. 119. Topics in Applied Physics. Springer Berlin Heidelberg, 2011, pp. 187–216. ISBN: 978-3-642-10505-0. DOI: 10.1007/978-3-642-10506-7_8 (cit. on p. 191).
[27] Daniel, Kucharski, Drew, Guckenberger, Gianlorenzo, Masini, et al. “10Gb/s 15mW optical receiver with integrated Germanium photodetector and hybrid inductor peaking in 0.13μm SOI CMOS technology”. Solid-State Circuits Conference Digest of Technical Papers (ISSCC), 2010 IEEE International. IEEE. 2010, pp. 360–361 (cit. on p. 191).
[28] Wim, Bogaerts, Dirk, Taillaert, Pieter, Dumon, et al. “A polarization-diversity wavelength duplexer circuit in silicon-on-insulator photonic wires”. Optics Express 15.4 (2007), pp. 1567–1578 (cit. on p. 191).
[29] David A. B., Miller. “Self-configuring universal linear optical component”. Photonics Research 1.1 (2013), pp. 1–15 (cit. on p. 191).
[30] Jan Niklas, Caspers, Yun, Wang, Lukas, Chrostowski, and Mohammad, Mo-jahedi. “Active polarization independent coupling to silicon photonics circuit”. Proc. SPIE. 2014, pp. 9133–9217 (cit. on p. 192).
[31] Wesley D., Sacher, Tymon, Barwicz, Benjamin J. F., Taylor, and Joyce K. S., Poon. “Polarization rotator-splitters in standard active silicon photonics platforms”. Optics Express 22.4 (2014), pp. 3777–3786 (cit. on p. 192).