We demonstrate low-loss silicon slot waveguides patterned with 248 nm deep-UV lithography and filled with atomic layer deposited aluminum oxide. Propagation losses less than 5 dB/cm are achieved with the waveguides. The devices are fabricated using low-temperature CMOS compatible processes. We also demonstrate simple, compact and efficient strip-to-slot waveguide couplers. With a coupler as short as 10 µm, coupling loss is less than 0.15 dB. The low-index and low-nonlinearity filling material allows nonlinearities nearly two orders of magnitude smaller than in silicon waveguides. Therefore, these waveguides are a good candidate for linear photonic devices on the silicon platform, and for distortion-free signal transmission channels between different parts of a silicon all-optical chip. The low-nonlinearity slot waveguides and robust couplers also facilitate a 50-fold local change of the waveguide nonlinearity within the chip by a simple mask design.

© 2011 OSA

1. H. Rong, A. Liu, R. Jones, O. Cohen, D. Hak, R. Nicolaescu, A. Fang, and M. Paniccia, “An all-silicon Raman laser,” Nature433(7023), 292–294 (2005). [CrossRef] [PubMed]
2. Y.-H. Kuo, H. Rong, V. Sih, S. Xu, M. Paniccia, and O. Cohen, “Demonstration of wavelength conversion at 40 Gb/s data rate in silicon waveguides,” Opt. Express14(24), 11721–11726 (2006). [CrossRef] [PubMed]
3. R. Salem, M. A. Foster, A. C. Turner, D. F. Geraghty, M. Lipson, and A. L. Gaeta, “All-optical regeneration on a silicon chip,” Opt. Express15(12), 7802–7809 (2007). [CrossRef] [PubMed]
4. Q. Xu and M. Lipson, “All-optical logic based on silicon micro-ring resonators,” Opt. Express15(3), 924–929 (2007). [CrossRef] [PubMed]
5. M. Hochberg and T. Baehr-Jones, “Towards fabless silicon photonics,” Nat. Photonics4(8), 492–494 (2010). [CrossRef]
6. Q. Xu, V. R. Almeida, R. R. Panepucci, and M. Lipson, “Experimental demonstration of guiding and confining light in nanometer-size low-refractive-index material,” Opt. Lett.29(14), 1626–1628 (2004). [CrossRef] [PubMed]
7. T. Baehr-Jones, B. Penkov, J. Huang, P. Sullivan, J. Davies, J. Takayesu, J. Luo, T.-D. Kim, L. Dalton, A. Jen, M. Hochberg, and A. Scherer, “Nonlinear polymer-clad silicon slot waveguide modulator with a half wave voltage of 0.25 V,” Appl. Phys. Lett.92(16), 163303 (2008). [CrossRef]
8. C. Koos, P. Vorreau, T. Vallaitis, P. Dumon, W. Bogaerts, R. Baets, B. Esembeson, I. Biaggio, T. Michinobu, F. Diederich, W. Freude, and J. Leuthold, “All-optical high-speed signal processing with silicon–organic hybrid slot waveguides,” Nat. Photonics3(4), 216–219 (2009). [CrossRef]
9. Y. Yue, L. Zhang, J. Wang, R. G. Beausoleil, and A. E. Willner, “Highly efficient nonlinearity reduction in silicon-on-insulator waveguides using vertical slots,” Opt. Express18(21), 22061–22066 (2010). [CrossRef] [PubMed]
10. T. Baehr-Jones, M. Hochberg, C. Walker, and A. Scherer, “High-Q optical resonators in silicon-on-insulator-based slot waveguides,” Appl. Phys. Lett.86(8), 081101 (2005). [CrossRef]
11. G. Wang, T. Baehr-Jones, M. Hochberg, and A. Scherer, “Design and fabrication of segmented, slotted waveguides for electro-optic modulation,” Appl. Phys. Lett.91(14), 143109 (2007). [CrossRef]
12. A. Spott, T. Baehr-Jones, R. Ding, Y. Liu, R. Bojko, T. O’Malley, A. Pomerene, C. Hill, W. Reinhardt, and M. Hochberg, “Photolithographically fabricated low-loss asymmetric silicon slot waveguides,” Opt. Express19(11), 10950–10958 (2011). [CrossRef] [PubMed]
13. Z. Wang, N. Zhu, Y. Tang, L. Wosinski, D. Dai, and S. He, “Ultracompact low-loss coupler between strip and slot waveguides,” Opt. Lett.34(10), 1498–1500 (2009). [CrossRef] [PubMed]
14. H. Sun, A. Chen, A. Szep, and L. R. Dalton, “Efficient fiber coupler for vertical silicon slot waveguides,” Opt. Express17(25), 22571–22577 (2009). [CrossRef] [PubMed]
15. T. Alasaarela, D. Korn, L. Alloatti, A. Säynätjoki, A. Tervonen, R. Palmer, J. Leuthold, W. Freude, and S. Honkanen, “Reduced propagation loss in silicon strip and slot waveguides coated by atomic layer deposition,” Opt. Express19(12), 11529–11538 (2011). [CrossRef] [PubMed]
16. A. Säynätjoki, T. Alasaarela, A. Khanna, L. Karvonen, P. Stenberg, M. Kuittinen, A. Tervonen, and S. Honkanen, “Angled sidewalls in silicon slot waveguides: conformal filling and mode properties,” Opt. Express17(23), 21066–21076 (2009). [CrossRef] [PubMed]
17. A. S. Sudbo, “Film mode matching: a versatile numerical method for vector mode field calculations in dielectric waveguides,” Pure Appl. Opt.2(3), 211–233 (1993).
18. J. Song, H. Zhao, Q. Fang, S. H. Tao, T. Y. Liow, M. B. Yu, G. Q. Lo, and D. L. Kwong, “Effective thermo-optical enhanced cross-ring resonator MZI interleavers on SOI,” Opt. Express16(26), 21476–21482 (2008). [CrossRef] [PubMed]
19. F. Grillot, L. Vivien, S. Laval, and E. Cassan, “Propagation loss in single-mode ultrasmall square silicon-on-insulator optical waveguides,” J. Lightwave Technol.24(2), 891–896 (2006). [CrossRef]
20. M. Gehl, R. Gibson, J. Hendrickson, A. Homyk, T. Alasaarela, A. Säynätjoki, A. Tervonen, S. Honkanen, S. Zandbergen, B. C. Richards, J. D. Olitzky, A. Scherer, G. Khitrova, H. M. Gibbs, J.-Y. Kim, and Y.-H. Lee, “Effect of atomic layer deposition on the quality factor of silicon nanobeam cavities,” presented at Fundamental Optical Processes in Semiconductors 2011, August 1–5, 2011, Lake Junaluska, NC, USA.

Appl. Phys. Lett.

• T. Baehr-Jones, B. Penkov, J. Huang, P. Sullivan, J. Davies, J. Takayesu, J. Luo, T.-D. Kim, L. Dalton, A. Jen, M. Hochberg, and A. Scherer, “Nonlinear polymer-clad silicon slot waveguide modulator with a half wave voltage of 0.25 V,” Appl. Phys. Lett.92(16), 163303 (2008). [CrossRef]
• T. Baehr-Jones, M. Hochberg, C. Walker, and A. Scherer, “High-Q optical resonators in silicon-on-insulator-based slot waveguides,” Appl. Phys. Lett.86(8), 081101 (2005). [CrossRef]
• G. Wang, T. Baehr-Jones, M. Hochberg, and A. Scherer, “Design and fabrication of segmented, slotted waveguides for electro-optic modulation,” Appl. Phys. Lett.91(14), 143109 (2007). [CrossRef]

J. Lightwave Technol.

• F. Grillot, L. Vivien, S. Laval, and E. Cassan, “Propagation loss in single-mode ultrasmall square silicon-on-insulator optical waveguides,” J. Lightwave Technol.24(2), 891–896 (2006). [CrossRef]

Nat. Photonics

• C. Koos, P. Vorreau, T. Vallaitis, P. Dumon, W. Bogaerts, R. Baets, B. Esembeson, I. Biaggio, T. Michinobu, F. Diederich, W. Freude, and J. Leuthold, “All-optical high-speed signal processing with silicon–organic hybrid slot waveguides,” Nat. Photonics3(4), 216–219 (2009). [CrossRef]
• M. Hochberg and T. Baehr-Jones, “Towards fabless silicon photonics,” Nat. Photonics4(8), 492–494 (2010). [CrossRef]

Nature

• H. Rong, A. Liu, R. Jones, O. Cohen, D. Hak, R. Nicolaescu, A. Fang, and M. Paniccia, “An all-silicon Raman laser,” Nature433(7023), 292–294 (2005). [CrossRef] [PubMed]

Opt. Express

• Y.-H. Kuo, H. Rong, V. Sih, S. Xu, M. Paniccia, and O. Cohen, “Demonstration of wavelength conversion at 40 Gb/s data rate in silicon waveguides,” Opt. Express14(24), 11721–11726 (2006). [CrossRef] [PubMed]
• R. Salem, M. A. Foster, A. C. Turner, D. F. Geraghty, M. Lipson, and A. L. Gaeta, “All-optical regeneration on a silicon chip,” Opt. Express15(12), 7802–7809 (2007). [CrossRef] [PubMed]
• Q. Xu and M. Lipson, “All-optical logic based on silicon micro-ring resonators,” Opt. Express15(3), 924–929 (2007). [CrossRef] [PubMed]
• Y. Yue, L. Zhang, J. Wang, R. G. Beausoleil, and A. E. Willner, “Highly efficient nonlinearity reduction in silicon-on-insulator waveguides using vertical slots,” Opt. Express18(21), 22061–22066 (2010). [CrossRef] [PubMed]
• A. Spott, T. Baehr-Jones, R. Ding, Y. Liu, R. Bojko, T. O’Malley, A. Pomerene, C. Hill, W. Reinhardt, and M. Hochberg, “Photolithographically fabricated low-loss asymmetric silicon slot waveguides,” Opt. Express19(11), 10950–10958 (2011). [CrossRef] [PubMed]
• H. Sun, A. Chen, A. Szep, and L. R. Dalton, “Efficient fiber coupler for vertical silicon slot waveguides,” Opt. Express17(25), 22571–22577 (2009). [CrossRef] [PubMed]
• T. Alasaarela, D. Korn, L. Alloatti, A. Säynätjoki, A. Tervonen, R. Palmer, J. Leuthold, W. Freude, and S. Honkanen, “Reduced propagation loss in silicon strip and slot waveguides coated by atomic layer deposition,” Opt. Express19(12), 11529–11538 (2011). [CrossRef] [PubMed]
• A. Säynätjoki, T. Alasaarela, A. Khanna, L. Karvonen, P. Stenberg, M. Kuittinen, A. Tervonen, and S. Honkanen, “Angled sidewalls in silicon slot waveguides: conformal filling and mode properties,” Opt. Express17(23), 21066–21076 (2009). [CrossRef] [PubMed]
• J. Song, H. Zhao, Q. Fang, S. H. Tao, T. Y. Liow, M. B. Yu, G. Q. Lo, and D. L. Kwong, “Effective thermo-optical enhanced cross-ring resonator MZI interleavers on SOI,” Opt. Express16(26), 21476–21482 (2008). [CrossRef] [PubMed]

Opt. Lett.

• Z. Wang, N. Zhu, Y. Tang, L. Wosinski, D. Dai, and S. He, “Ultracompact low-loss coupler between strip and slot waveguides,” Opt. Lett.34(10), 1498–1500 (2009). [CrossRef] [PubMed]
• Q. Xu, V. R. Almeida, R. R. Panepucci, and M. Lipson, “Experimental demonstration of guiding and confining light in nanometer-size low-refractive-index material,” Opt. Lett.29(14), 1626–1628 (2004). [CrossRef] [PubMed]

Pure Appl. Opt.

• A. S. Sudbo, “Film mode matching: a versatile numerical method for vector mode field calculations in dielectric waveguides,” Pure Appl. Opt.2(3), 211–233 (1993).

Other

• M. Gehl, R. Gibson, J. Hendrickson, A. Homyk, T. Alasaarela, A. Säynätjoki, A. Tervonen, S. Honkanen, S. Zandbergen, B. C. Richards, J. D. Olitzky, A. Scherer, G. Khitrova, H. M. Gibbs, J.-Y. Kim, and Y.-H. Lee, “Effect of atomic layer deposition on the quality factor of silicon nanobeam cavities,” presented at Fundamental Optical Processes in Semiconductors 2011, August 1–5, 2011, Lake Junaluska, NC, USA.

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