Abstract

We demonstrate 0.8dB/cm transmission loss for a single-mode, strip Si/SiO2 waveguide with submicrometer cross-sectional dimensions. We compare the conventional waveguide-fabrication method with two smoothing technologies that we have developed, oxidation smoothing and anisotropic etching. We observe significant reduction of sidewall roughness with our smoothing technologies, which directly results in reduced scattering losses. The rapid increase in the scattering losses as the waveguide dimension is miniaturized, as seen in conventionally fabricated waveguides, is effectively suppressed in the waveguides made with our smoothing technologies. In the oxidation smoothing case, the loss is reduced from 32 dB/cm for the conventional fabrication method to 0.8 dB/cm for the single-mode waveguide width of 0.5 μm. This is to our knowledge the smallest reported loss for a high-index-difference system such as a Si/SiO2 strip waveguide.

© 2001 Optical Society of America

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References

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  1. J. Foresi, D. Lim, A. Agarwal, L. Kimerling, M. Tavassoli, M. Cox, M. Cao, and W. Greene, “Small radius bends and large angle splitters in SOI waveguides,” Proc. SPIE 3007, 112–118 (1997).
    [CrossRef]
  2. S. Suzuki, M. Yanagisawa, Y. Hibino, and K. Oda, “High-density integrated planar lightwave circuits using SiO2–GeO2 waveguides with a high refractive index difference,” J. Lightwave Technol. 12, 790–796 (1994).
    [CrossRef]
  3. A. Merlos, M. Acero, M. H. Bao, J. Bansells, and J. Esteve, “TMAH/IPA anisotropic etching characteristics,” Sens. Actuators A 37–38, 737 (1993).
    [CrossRef]
  4. T. Feuchter and C. Thirstrup, “High precision planar waveguide propagation loss measurement technique using a Fabry–Perot cavity,” IEEE Photon. Technol. Lett. 6, 1244–1247 (1994).
    [CrossRef]
  5. K. K. Lee, D. R. Lim, H.-C. Luan, A. Agrawal, J. Foresi, and L. C. Kimerling, “Effect of size and roughness on light transmission in a Si/SiO2 waveguide: experiments and model,” Appl. Phys. Lett. 77, 1617–1619 (2000).
    [CrossRef]
  6. O. Tabata, R. Asahi, H. Funabashi, K. Shimaoka, and S. Sugiyama, “Anisotropic etching of silicon in TMAH solutions,” Sens. Actuators A 34, 51 (1992).
    [CrossRef]
  7. S. Ghandhi, VLSI Fabrication Principles, Silicon and Gallium Arsenide (Wiley-Interscience, New York, 1994).
  8. D. Marcuse, “Mode conversion caused by surface imperfections of a dielectric slab waveguide,” Bell Syst. Tech. J. 48, 3187–3215 (1969).
    [CrossRef]
  9. F. P. Payne and J. P. R. Lacey, “A theoretical analysis of scattering loss from planar optical waveguides,” Opt. Quantum Electron. 26, 977–986 (1994).
    [CrossRef]

2000 (1)

K. K. Lee, D. R. Lim, H.-C. Luan, A. Agrawal, J. Foresi, and L. C. Kimerling, “Effect of size and roughness on light transmission in a Si/SiO2 waveguide: experiments and model,” Appl. Phys. Lett. 77, 1617–1619 (2000).
[CrossRef]

1997 (1)

J. Foresi, D. Lim, A. Agarwal, L. Kimerling, M. Tavassoli, M. Cox, M. Cao, and W. Greene, “Small radius bends and large angle splitters in SOI waveguides,” Proc. SPIE 3007, 112–118 (1997).
[CrossRef]

1994 (3)

S. Suzuki, M. Yanagisawa, Y. Hibino, and K. Oda, “High-density integrated planar lightwave circuits using SiO2–GeO2 waveguides with a high refractive index difference,” J. Lightwave Technol. 12, 790–796 (1994).
[CrossRef]

T. Feuchter and C. Thirstrup, “High precision planar waveguide propagation loss measurement technique using a Fabry–Perot cavity,” IEEE Photon. Technol. Lett. 6, 1244–1247 (1994).
[CrossRef]

F. P. Payne and J. P. R. Lacey, “A theoretical analysis of scattering loss from planar optical waveguides,” Opt. Quantum Electron. 26, 977–986 (1994).
[CrossRef]

1993 (1)

A. Merlos, M. Acero, M. H. Bao, J. Bansells, and J. Esteve, “TMAH/IPA anisotropic etching characteristics,” Sens. Actuators A 37–38, 737 (1993).
[CrossRef]

1992 (1)

O. Tabata, R. Asahi, H. Funabashi, K. Shimaoka, and S. Sugiyama, “Anisotropic etching of silicon in TMAH solutions,” Sens. Actuators A 34, 51 (1992).
[CrossRef]

1969 (1)

D. Marcuse, “Mode conversion caused by surface imperfections of a dielectric slab waveguide,” Bell Syst. Tech. J. 48, 3187–3215 (1969).
[CrossRef]

Acero, M.

A. Merlos, M. Acero, M. H. Bao, J. Bansells, and J. Esteve, “TMAH/IPA anisotropic etching characteristics,” Sens. Actuators A 37–38, 737 (1993).
[CrossRef]

Agarwal, A.

J. Foresi, D. Lim, A. Agarwal, L. Kimerling, M. Tavassoli, M. Cox, M. Cao, and W. Greene, “Small radius bends and large angle splitters in SOI waveguides,” Proc. SPIE 3007, 112–118 (1997).
[CrossRef]

Agrawal, A.

K. K. Lee, D. R. Lim, H.-C. Luan, A. Agrawal, J. Foresi, and L. C. Kimerling, “Effect of size and roughness on light transmission in a Si/SiO2 waveguide: experiments and model,” Appl. Phys. Lett. 77, 1617–1619 (2000).
[CrossRef]

Asahi, R.

O. Tabata, R. Asahi, H. Funabashi, K. Shimaoka, and S. Sugiyama, “Anisotropic etching of silicon in TMAH solutions,” Sens. Actuators A 34, 51 (1992).
[CrossRef]

Bansells, J.

A. Merlos, M. Acero, M. H. Bao, J. Bansells, and J. Esteve, “TMAH/IPA anisotropic etching characteristics,” Sens. Actuators A 37–38, 737 (1993).
[CrossRef]

Bao, M. H.

A. Merlos, M. Acero, M. H. Bao, J. Bansells, and J. Esteve, “TMAH/IPA anisotropic etching characteristics,” Sens. Actuators A 37–38, 737 (1993).
[CrossRef]

Cao, M.

J. Foresi, D. Lim, A. Agarwal, L. Kimerling, M. Tavassoli, M. Cox, M. Cao, and W. Greene, “Small radius bends and large angle splitters in SOI waveguides,” Proc. SPIE 3007, 112–118 (1997).
[CrossRef]

Cox, M.

J. Foresi, D. Lim, A. Agarwal, L. Kimerling, M. Tavassoli, M. Cox, M. Cao, and W. Greene, “Small radius bends and large angle splitters in SOI waveguides,” Proc. SPIE 3007, 112–118 (1997).
[CrossRef]

Esteve, J.

A. Merlos, M. Acero, M. H. Bao, J. Bansells, and J. Esteve, “TMAH/IPA anisotropic etching characteristics,” Sens. Actuators A 37–38, 737 (1993).
[CrossRef]

Feuchter, T.

T. Feuchter and C. Thirstrup, “High precision planar waveguide propagation loss measurement technique using a Fabry–Perot cavity,” IEEE Photon. Technol. Lett. 6, 1244–1247 (1994).
[CrossRef]

Foresi, J.

K. K. Lee, D. R. Lim, H.-C. Luan, A. Agrawal, J. Foresi, and L. C. Kimerling, “Effect of size and roughness on light transmission in a Si/SiO2 waveguide: experiments and model,” Appl. Phys. Lett. 77, 1617–1619 (2000).
[CrossRef]

J. Foresi, D. Lim, A. Agarwal, L. Kimerling, M. Tavassoli, M. Cox, M. Cao, and W. Greene, “Small radius bends and large angle splitters in SOI waveguides,” Proc. SPIE 3007, 112–118 (1997).
[CrossRef]

Funabashi, H.

O. Tabata, R. Asahi, H. Funabashi, K. Shimaoka, and S. Sugiyama, “Anisotropic etching of silicon in TMAH solutions,” Sens. Actuators A 34, 51 (1992).
[CrossRef]

Ghandhi, S.

S. Ghandhi, VLSI Fabrication Principles, Silicon and Gallium Arsenide (Wiley-Interscience, New York, 1994).

Greene, W.

J. Foresi, D. Lim, A. Agarwal, L. Kimerling, M. Tavassoli, M. Cox, M. Cao, and W. Greene, “Small radius bends and large angle splitters in SOI waveguides,” Proc. SPIE 3007, 112–118 (1997).
[CrossRef]

Hibino, Y.

S. Suzuki, M. Yanagisawa, Y. Hibino, and K. Oda, “High-density integrated planar lightwave circuits using SiO2–GeO2 waveguides with a high refractive index difference,” J. Lightwave Technol. 12, 790–796 (1994).
[CrossRef]

Kimerling, L.

J. Foresi, D. Lim, A. Agarwal, L. Kimerling, M. Tavassoli, M. Cox, M. Cao, and W. Greene, “Small radius bends and large angle splitters in SOI waveguides,” Proc. SPIE 3007, 112–118 (1997).
[CrossRef]

Kimerling, L. C.

K. K. Lee, D. R. Lim, H.-C. Luan, A. Agrawal, J. Foresi, and L. C. Kimerling, “Effect of size and roughness on light transmission in a Si/SiO2 waveguide: experiments and model,” Appl. Phys. Lett. 77, 1617–1619 (2000).
[CrossRef]

Lacey, J. P. R.

F. P. Payne and J. P. R. Lacey, “A theoretical analysis of scattering loss from planar optical waveguides,” Opt. Quantum Electron. 26, 977–986 (1994).
[CrossRef]

Lee, K. K.

K. K. Lee, D. R. Lim, H.-C. Luan, A. Agrawal, J. Foresi, and L. C. Kimerling, “Effect of size and roughness on light transmission in a Si/SiO2 waveguide: experiments and model,” Appl. Phys. Lett. 77, 1617–1619 (2000).
[CrossRef]

Lim, D.

J. Foresi, D. Lim, A. Agarwal, L. Kimerling, M. Tavassoli, M. Cox, M. Cao, and W. Greene, “Small radius bends and large angle splitters in SOI waveguides,” Proc. SPIE 3007, 112–118 (1997).
[CrossRef]

Lim, D. R.

K. K. Lee, D. R. Lim, H.-C. Luan, A. Agrawal, J. Foresi, and L. C. Kimerling, “Effect of size and roughness on light transmission in a Si/SiO2 waveguide: experiments and model,” Appl. Phys. Lett. 77, 1617–1619 (2000).
[CrossRef]

Luan, H.-C.

K. K. Lee, D. R. Lim, H.-C. Luan, A. Agrawal, J. Foresi, and L. C. Kimerling, “Effect of size and roughness on light transmission in a Si/SiO2 waveguide: experiments and model,” Appl. Phys. Lett. 77, 1617–1619 (2000).
[CrossRef]

Marcuse, D.

D. Marcuse, “Mode conversion caused by surface imperfections of a dielectric slab waveguide,” Bell Syst. Tech. J. 48, 3187–3215 (1969).
[CrossRef]

Merlos, A.

A. Merlos, M. Acero, M. H. Bao, J. Bansells, and J. Esteve, “TMAH/IPA anisotropic etching characteristics,” Sens. Actuators A 37–38, 737 (1993).
[CrossRef]

Oda, K.

S. Suzuki, M. Yanagisawa, Y. Hibino, and K. Oda, “High-density integrated planar lightwave circuits using SiO2–GeO2 waveguides with a high refractive index difference,” J. Lightwave Technol. 12, 790–796 (1994).
[CrossRef]

Payne, F. P.

F. P. Payne and J. P. R. Lacey, “A theoretical analysis of scattering loss from planar optical waveguides,” Opt. Quantum Electron. 26, 977–986 (1994).
[CrossRef]

Shimaoka, K.

O. Tabata, R. Asahi, H. Funabashi, K. Shimaoka, and S. Sugiyama, “Anisotropic etching of silicon in TMAH solutions,” Sens. Actuators A 34, 51 (1992).
[CrossRef]

Sugiyama, S.

O. Tabata, R. Asahi, H. Funabashi, K. Shimaoka, and S. Sugiyama, “Anisotropic etching of silicon in TMAH solutions,” Sens. Actuators A 34, 51 (1992).
[CrossRef]

Suzuki, S.

S. Suzuki, M. Yanagisawa, Y. Hibino, and K. Oda, “High-density integrated planar lightwave circuits using SiO2–GeO2 waveguides with a high refractive index difference,” J. Lightwave Technol. 12, 790–796 (1994).
[CrossRef]

Tabata, O.

O. Tabata, R. Asahi, H. Funabashi, K. Shimaoka, and S. Sugiyama, “Anisotropic etching of silicon in TMAH solutions,” Sens. Actuators A 34, 51 (1992).
[CrossRef]

Tavassoli, M.

J. Foresi, D. Lim, A. Agarwal, L. Kimerling, M. Tavassoli, M. Cox, M. Cao, and W. Greene, “Small radius bends and large angle splitters in SOI waveguides,” Proc. SPIE 3007, 112–118 (1997).
[CrossRef]

Thirstrup, C.

T. Feuchter and C. Thirstrup, “High precision planar waveguide propagation loss measurement technique using a Fabry–Perot cavity,” IEEE Photon. Technol. Lett. 6, 1244–1247 (1994).
[CrossRef]

Yanagisawa, M.

S. Suzuki, M. Yanagisawa, Y. Hibino, and K. Oda, “High-density integrated planar lightwave circuits using SiO2–GeO2 waveguides with a high refractive index difference,” J. Lightwave Technol. 12, 790–796 (1994).
[CrossRef]

Appl. Phys. Lett. (1)

K. K. Lee, D. R. Lim, H.-C. Luan, A. Agrawal, J. Foresi, and L. C. Kimerling, “Effect of size and roughness on light transmission in a Si/SiO2 waveguide: experiments and model,” Appl. Phys. Lett. 77, 1617–1619 (2000).
[CrossRef]

Bell Syst. Tech. J. (1)

D. Marcuse, “Mode conversion caused by surface imperfections of a dielectric slab waveguide,” Bell Syst. Tech. J. 48, 3187–3215 (1969).
[CrossRef]

IEEE Photon. Technol. Lett. (1)

T. Feuchter and C. Thirstrup, “High precision planar waveguide propagation loss measurement technique using a Fabry–Perot cavity,” IEEE Photon. Technol. Lett. 6, 1244–1247 (1994).
[CrossRef]

J. Lightwave Technol. (1)

S. Suzuki, M. Yanagisawa, Y. Hibino, and K. Oda, “High-density integrated planar lightwave circuits using SiO2–GeO2 waveguides with a high refractive index difference,” J. Lightwave Technol. 12, 790–796 (1994).
[CrossRef]

Opt. Quantum Electron. (1)

F. P. Payne and J. P. R. Lacey, “A theoretical analysis of scattering loss from planar optical waveguides,” Opt. Quantum Electron. 26, 977–986 (1994).
[CrossRef]

Proc. SPIE (1)

J. Foresi, D. Lim, A. Agarwal, L. Kimerling, M. Tavassoli, M. Cox, M. Cao, and W. Greene, “Small radius bends and large angle splitters in SOI waveguides,” Proc. SPIE 3007, 112–118 (1997).
[CrossRef]

Sens. Actuators A (2)

A. Merlos, M. Acero, M. H. Bao, J. Bansells, and J. Esteve, “TMAH/IPA anisotropic etching characteristics,” Sens. Actuators A 37–38, 737 (1993).
[CrossRef]

O. Tabata, R. Asahi, H. Funabashi, K. Shimaoka, and S. Sugiyama, “Anisotropic etching of silicon in TMAH solutions,” Sens. Actuators A 34, 51 (1992).
[CrossRef]

Other (1)

S. Ghandhi, VLSI Fabrication Principles, Silicon and Gallium Arsenide (Wiley-Interscience, New York, 1994).

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Figures (4)

Fig. 1
Fig. 1

Fabrication steps of the oxidation smoothing waveguides. The additional steps that the waveguides go through after they are patterned by photolithography and RIE are shown. After these fabrication steps, a blanket SiO2 layer is deposited on top as an upper cladding.

Fig. 2
Fig. 2

Fabrication steps of the anisotroptic-etching waveguides. The substrate is (100) Si, and the SiO2 mask is aligned in the 110 direction so that the resulting Si core will reveal 111-type surfaces on the sidewalls. After these fabrication steps, a blanket SiO2 layer is deposited on top as an upper cladding.

Fig. 3
Fig. 3

AFM images of the top and the sidewall of the waveguides fabricated by three methods. The sidewall:roughness values, σ:Lc, of the three samples are 10  nm:50  nm, 2  nm:50  nm, and 2  nm:50  nm, respectively.

Fig. 4
Fig. 4

Transmission losses of waveguides fabricated by three methods. Two calculation plots based on the Marcuse, Payne, and Lee model are included that correspond to the sidewall:roughness values σ:Lc of 10  nm:50  nm and 2  nm:50  nm, respectively. The thick curve corresponds to the roughness value of the conventionally fabricated waveguide, and the dashed curve corresponds to that of the oxidation smoothing and the anisotropic etching waveguides.

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αs=4.3σ22k0d4n1gfe,

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