Abstract

Frequency mismatches between resonators significantly impact the spectral responses of coupled resonator filters, such as high-order microring filters. In this paper, techniques allowing fabrication of frequency-matched high-index-contrast resonators are proposed, demonstrated, and analyzed. The main approach consists of inducing small dimensional changes in the resonators through alteration of the electron-beam dose used to expose either the actual resonator on a wafer or its image on a lithographic mask to be later used in filter fabrication. Third-order microring filters fabricated in silicon-rich silicon nitride, with optical resonator frequencies matched to better than 1 GHz, are reported. To achieve this, the average ring-waveguide widths of the microrings are matched to within less than 26 pm of a desired relative width offset. Furthermore, optimization and calibration procedures allowing strict dimensional control and smooth sidewalls are presented. A 5-nm dimensional control is demonstrated, and the standard deviation of sidewall roughness is reduced to below 1.6 nm.

© 2006 IEEE

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  1. C. Manolatou, M. A. Popovic, P. T. Rakich, T. Barwicz, H. A. Haus and E. P. Ippen, "Spectral anomalies due to coupling-induced frequency shifts in dielectric coupled resonator filters", in Proc. Opt. Fiber Commun. Conf., Washington, DC, 2004, pp. 379-381.
  2. M. A. Popovic, C. Manolatou and H. A. Haus, "Coupling-induced resonance frequency shifts in coupled dielectric multi-cavity filters", Opt. Express, vol. 14, no. 3, pp. 1208-1222, Feb. 2006.
  3. T. Barwicz, M. A. Popovic, P. T. Rakich, M. R. Watts, H. A. Haus, E. P. Ippen and H. I. Smith, "Microring-resonator-based add-drop filters in SiN: Fabrication and analysis", Opt. Express, vol. 12, no. 7, pp. 1437-1442, Apr. 2004.
  4. B. E. Little, "A VLSI photonic platform", in Proc. Opt. Fiber Commun. Conf., vol. 2, Washington, DC, 2003, pp. 444-445.
  5. J. V. Hryniewicz, P. P. Absil, B. E. Little, R. A. Wilson and P.-T. Ho, "Higher order filter response in coupled microring resonators", IEEE Photon. Technol. Lett., vol. 12, no. 3, pp. 320-322, Mar. 2000.
  6. Y. Yanagase, S. Suzuki, Y. Kokubun and S. T. Chu, "Box-like filter response and expansion of FSR by a vertically triple coupled microring resonator filter", J. Lightw. Technol., vol. 20, no. 8, pp. 1525-1529, Aug. 2002.
  7. M. A. Popovic, T. Barwicz, M. R. Watts, P. T. Rakich, L. Socci, E. P. Ippen, F. X. Kärtner and H. I. Smith, "Multistage high-order microring-resonator filters with relaxed tolerances for high through-port extinction", presented at the Conf. Lasers and Electro-Optics, Baltimore, MD, Paper CMP2, 2005.
  8. A. Melloni and M. Martinelli, "Synthesis of direct-coupled-resonators bandpass filters for WDM systems", J. Lightw. Technol., vol. 20, no. 2, pp. 296-303, Feb. 2002.
  9. M. A. Popovic, M. R. Watts, T. Barwicz, P. T. Rakich, L. Socci, E. P. Ippen, F. X. Kärtner and H. I. Smith, "High-index-contrast, wide-FSR microring-resonator filter design and realization with frequency-shift compensation", presented at the Optical Fiber Communication Conf., Anaheim, CA, Paper OFK1, 2005.
  10. Mitsubishi Rayon America Inc., "aquaSAVE Datasheet", 2004.
  11. T. Barwicz and H. I. Smith, "Evolution of line-edge-roughness during fabrication of high index-contrast microphotonic devices", J. Vac. Sci. Technol. B, Microelectron. Process. Phenom., vol. 21, no. 6, pp. 2892-2896, Nov./Dec. 2003.
  12. S. Yasin, D. G. Hasko, M. N. Khalid, D. J. Weaver and H. Ahme, "Influence of polymer phase separation on roughness of resist features", J. Vac. Sci. Technol. B, Microelectron. Process. Phenom., vol. 22, no. 2, pp. 574-578, Mar./Apr. 2004.
  13. F. Ladouceur, J. D. Love and T. J. Senden, "Effect of side wall roughness in buried channel waveguides", Proc. Inst. Elect. Eng.-Optoelectron., vol. 141, no. 4, pp. 242-248, Aug. 1994.
  14. D. Marcuse, "Radiation losses of dielectric waveguides in terms of the power spectrum of the wall distortion function", Bell Syst. Tech. J., vol. 48, no. 10, pp. 3233-3244, Dec. 1969.
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  16. K. K. Lee, D. R. Lim, H. C. Luan, A. Agarwal, 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., vol. 77, no. 11, pp. 1617-1619, Sep. 2000.
  17. Y. A. Vlasov and S. J. McNab, "Losses in single-mode silicon-on-insulator strip waveguides and bends", Opt. Express, vol. 12, no. 8, pp. 1622-1631, Apr. 2004.
  18. U. Hofmann, R. Crandall and L. Johnson, "Fundamental performance of state-of-the-art proximity effect correction methods", J. Vac. Sci. Technol. B, Microelectron. Process. Phenom., vol. 17, no. 6, pp. 2940-2944, Nov./Dec. 1999.
  19. L. Stevens, R. Jonckheere, E. Froyen, S. Decoutere and D. Lanneer, "Determination of the proximity parameters in electron beam lithography using doughnut-structures", Microelectron. Eng., vol. 5, no. 1-4, pp. 141-150, Dec. 1986.
  20. S. A. Rishton and D. P. Kern, "Point exposure distribution measurements for proximity correction in electron-beam lithography on a sub-100 nm scale", J. Vac. Sci. Technol. B, Microelectron. Process. Phenom., vol. 5, no. 1, pp. 135-141, Jan./Feb. 1987.
  21. T. H. P. Chang, "Proximity effect in electron-beam lithography", J. Vac. Sci. Technol., vol. 12, no. 6, pp. 1271-1275, Nov./Dec. 1975.
  22. Y. Ma, F. Cerrina, T. Barwicz and H. I. Smith, "Theoretical and experimental study of electron beam exposure for microphotonic devices", presented at the Electron, Ion Photon Beam Technology Nanofabrication Conf., Orlando, FL, May 31-Jun. 3 2005.
  23. S. A. Prahl. (1988). "Light transport in tissue," Ph.D. dissertation, Biomed. Eng., Univ. Texas, Austin. [Online]. Available: http://omlc.ogi. edu/pubs/pdf/prahl88.pdf
  24. C. W. Holzwarth, private communication, Apr. 2005
  25. T. Barwicz, "Accurate nanofabrication techniques for high-index-contrast microphotonic devices", Ph.D. dissertation, Dept. Mater. Sci. Eng., Mass. Inst. Technol., Cambridge, MA, 2005.

Other (25)

C. Manolatou, M. A. Popovic, P. T. Rakich, T. Barwicz, H. A. Haus and E. P. Ippen, "Spectral anomalies due to coupling-induced frequency shifts in dielectric coupled resonator filters", in Proc. Opt. Fiber Commun. Conf., Washington, DC, 2004, pp. 379-381.

M. A. Popovic, C. Manolatou and H. A. Haus, "Coupling-induced resonance frequency shifts in coupled dielectric multi-cavity filters", Opt. Express, vol. 14, no. 3, pp. 1208-1222, Feb. 2006.

T. Barwicz, M. A. Popovic, P. T. Rakich, M. R. Watts, H. A. Haus, E. P. Ippen and H. I. Smith, "Microring-resonator-based add-drop filters in SiN: Fabrication and analysis", Opt. Express, vol. 12, no. 7, pp. 1437-1442, Apr. 2004.

B. E. Little, "A VLSI photonic platform", in Proc. Opt. Fiber Commun. Conf., vol. 2, Washington, DC, 2003, pp. 444-445.

J. V. Hryniewicz, P. P. Absil, B. E. Little, R. A. Wilson and P.-T. Ho, "Higher order filter response in coupled microring resonators", IEEE Photon. Technol. Lett., vol. 12, no. 3, pp. 320-322, Mar. 2000.

Y. Yanagase, S. Suzuki, Y. Kokubun and S. T. Chu, "Box-like filter response and expansion of FSR by a vertically triple coupled microring resonator filter", J. Lightw. Technol., vol. 20, no. 8, pp. 1525-1529, Aug. 2002.

M. A. Popovic, T. Barwicz, M. R. Watts, P. T. Rakich, L. Socci, E. P. Ippen, F. X. Kärtner and H. I. Smith, "Multistage high-order microring-resonator filters with relaxed tolerances for high through-port extinction", presented at the Conf. Lasers and Electro-Optics, Baltimore, MD, Paper CMP2, 2005.

A. Melloni and M. Martinelli, "Synthesis of direct-coupled-resonators bandpass filters for WDM systems", J. Lightw. Technol., vol. 20, no. 2, pp. 296-303, Feb. 2002.

M. A. Popovic, M. R. Watts, T. Barwicz, P. T. Rakich, L. Socci, E. P. Ippen, F. X. Kärtner and H. I. Smith, "High-index-contrast, wide-FSR microring-resonator filter design and realization with frequency-shift compensation", presented at the Optical Fiber Communication Conf., Anaheim, CA, Paper OFK1, 2005.

Mitsubishi Rayon America Inc., "aquaSAVE Datasheet", 2004.

T. Barwicz and H. I. Smith, "Evolution of line-edge-roughness during fabrication of high index-contrast microphotonic devices", J. Vac. Sci. Technol. B, Microelectron. Process. Phenom., vol. 21, no. 6, pp. 2892-2896, Nov./Dec. 2003.

S. Yasin, D. G. Hasko, M. N. Khalid, D. J. Weaver and H. Ahme, "Influence of polymer phase separation on roughness of resist features", J. Vac. Sci. Technol. B, Microelectron. Process. Phenom., vol. 22, no. 2, pp. 574-578, Mar./Apr. 2004.

F. Ladouceur, J. D. Love and T. J. Senden, "Effect of side wall roughness in buried channel waveguides", Proc. Inst. Elect. Eng.-Optoelectron., vol. 141, no. 4, pp. 242-248, Aug. 1994.

D. Marcuse, "Radiation losses of dielectric waveguides in terms of the power spectrum of the wall distortion function", Bell Syst. Tech. J., vol. 48, no. 10, pp. 3233-3244, Dec. 1969.

T. Barwicz and H. A. Haus, "Three-dimensional analysis of scattering losses due to sidewall roughness in microphotonic waveguides", J. Lightw. Technol., vol. 23, no. 9, pp. 2719-2732, Sep. 2005.

K. K. Lee, D. R. Lim, H. C. Luan, A. Agarwal, 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., vol. 77, no. 11, pp. 1617-1619, Sep. 2000.

Y. A. Vlasov and S. J. McNab, "Losses in single-mode silicon-on-insulator strip waveguides and bends", Opt. Express, vol. 12, no. 8, pp. 1622-1631, Apr. 2004.

U. Hofmann, R. Crandall and L. Johnson, "Fundamental performance of state-of-the-art proximity effect correction methods", J. Vac. Sci. Technol. B, Microelectron. Process. Phenom., vol. 17, no. 6, pp. 2940-2944, Nov./Dec. 1999.

L. Stevens, R. Jonckheere, E. Froyen, S. Decoutere and D. Lanneer, "Determination of the proximity parameters in electron beam lithography using doughnut-structures", Microelectron. Eng., vol. 5, no. 1-4, pp. 141-150, Dec. 1986.

S. A. Rishton and D. P. Kern, "Point exposure distribution measurements for proximity correction in electron-beam lithography on a sub-100 nm scale", J. Vac. Sci. Technol. B, Microelectron. Process. Phenom., vol. 5, no. 1, pp. 135-141, Jan./Feb. 1987.

T. H. P. Chang, "Proximity effect in electron-beam lithography", J. Vac. Sci. Technol., vol. 12, no. 6, pp. 1271-1275, Nov./Dec. 1975.

Y. Ma, F. Cerrina, T. Barwicz and H. I. Smith, "Theoretical and experimental study of electron beam exposure for microphotonic devices", presented at the Electron, Ion Photon Beam Technology Nanofabrication Conf., Orlando, FL, May 31-Jun. 3 2005.

S. A. Prahl. (1988). "Light transport in tissue," Ph.D. dissertation, Biomed. Eng., Univ. Texas, Austin. [Online]. Available: http://omlc.ogi. edu/pubs/pdf/prahl88.pdf

C. W. Holzwarth, private communication, Apr. 2005

T. Barwicz, "Accurate nanofabrication techniques for high-index-contrast microphotonic devices", Ph.D. dissertation, Dept. Mater. Sci. Eng., Mass. Inst. Technol., Cambridge, MA, 2005.

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