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Silicon optical modulators

A Corrigendum to this article was published on 01 September 2010

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Abstract

Optical technology is poised to revolutionize short-reach interconnects. The leading candidate technology is silicon photonics, and the workhorse of such an interconnect is the optical modulator. Modulators have been improved dramatically in recent years, with a notable increase in bandwidth from the megahertz to the multigigahertz regime in just over half a decade. However, the demands of optical interconnects are significant, and many questions remain unanswered as to whether silicon can meet the required performance metrics. Minimizing metrics such as the device footprint and energy requirement per bit, while also maximizing bandwidth and modulation depth, is non-trivial. All of this must be achieved within an acceptable thermal tolerance and optical spectral width using CMOS-compatible fabrication processes. This Review discusses the techniques that have been (and will continue to be) used to implement silicon optical modulators, as well as providing an outlook for these devices and the candidate solutions of the future.

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Figure 1: Cross-sections of typical device structures implementing the three different mechanisms commonly used to electrically manipulate the free-carrier concentrations in plasma-dispersion-based silicon optical modulators.
Figure 2: The first devices to propose and realize modulation at gigahertz frequencies in silicon, together with the best present carrier-accumulation-type device.
Figure 3: Carrier-depletion-based silicon optical modulators, showing both the first proposed and present fastest devices.
Figure 4: The first silicon optical modulator to use a ring resonator structure to translate phase variations into intensity variations.
Figure 5: A possible future alternative to plasma-dispersion-based silicon optical modulators is the SiGe QCSE modulator.

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  • 12 August 2010

    Ref. 86 was incorrectly cited in both the title and the last data row of Table 1. The correct citation is ref. 24, and this has been corrected for all versions of the article.

References

  1. http://www.cl.cam.ac.uk/awm22/publications/miller2009motivating.pdf

  2. Miller, D. A. B. Rationale and challenges for optical interconnects to electronic chips. Proc. IEEE 88, 728–749 (2000).

    Article  Google Scholar 

  3. http://www.itrs.net/links/2007itrs/execsum2007.pdf

  4. Miller, D. Device requirements for optical interconnects to silicon chips. Proc. IEEE 97, 1166–1185 (2009).

    Article  Google Scholar 

  5. Pepeljugoski, P. K. et al. Low power and high density optical interconnects for future supercomputers. Optical Fiber Communication Conf. paper OThX2 (2010).

  6. Lee, B. G., Biberman, A., Chan, J. & Bergman, K. High-performance modulators and switches for silicon photonic networks-on-chip. IEEE J. Sel. Top. Quant. Electron. 16, 6–22 (2010).

    Article  ADS  Google Scholar 

  7. Pollock, C. & Lipson, M. Integrated Photonics Ch. 12, 301–334 (Kluwer Academic Publishers, 2003).

    Book  Google Scholar 

  8. Soref, R. & Bennett, B. Electrooptical effects in silicon. IEEE J. Quant. Electron. 23, 123–129 (1987).

    Article  ADS  Google Scholar 

  9. Reed, G. T. & Knights, A. P. Silicon Photonics: An Introduction Ch. 4, 97–103 (Wiley, 2004).

    Book  Google Scholar 

  10. Cocorullo, G. & Rendina, I. Thermo-optical modulation at 1.5 μm in silicon etalon. Electron. Lett. 28, 83–85 (1992).

    Article  Google Scholar 

  11. Reed, G. T. Silicon Photonics: The State of the Art Ch. 4, 95–145 (Wiley, 2008).

    Book  Google Scholar 

  12. Liu, J. et al. Waveguide-integrated, ultralow-energy GeSi electro-absorption modulators. Nature Photon. 2, 433–437 (2008).

    Article  ADS  Google Scholar 

  13. Kuo, Y.-H. et al. Strong quantum-confined Stark effect in germanium quantum-well structures on silicon. Nature 437, 1334–1336 (2005).

    Article  ADS  Google Scholar 

  14. Roth, J. E. et al. Optical modulator on silicon employing germanium quantum wells. Opt. Express 15, 5851–5859 (2007).

    Article  ADS  Google Scholar 

  15. Roth, J. E. et al. C-band side-entry Ge quantum-well electroabsorption modulator on SOI operating at 1 V swing. Electron. Lett. 44, 49–50 (2008).

    Article  Google Scholar 

  16. Krishnamoorthy, A. V. et al. Potentials of group IV photonics interconnects for 'red-shift' computing applications. Proc. 4th IEEE Int. Conf. Group IV Photonics 1–3 (2007).

  17. Barwicz, T. et al. Silicon photonics for compact, energy-efficient interconnects. J. Opt. Netw. 6, 63–73 (2007).

    Article  Google Scholar 

  18. Yoo, S. J. B. Future prospects of silicon photonics in next generation communication and computing systems. Electron. Lett. 45, 584–588 (2009).

    Article  Google Scholar 

  19. Alduino, A. & Paniccia, M. Wiring electronics with light. Nature Photon. 1, 153–155 (2007).

    Article  ADS  Google Scholar 

  20. Green, W. M., Rooks, M. J., Sekaric, L. & Vlasov, Y. A. Ultra-compact, low RF power, 10 Gb/s silicon Mach–Zehnder modulator. Opt. Express 15, 17106–17113 (2007).

    Article  ADS  Google Scholar 

  21. Helman, N. C. et al. Misalignment-tolerant surface-normal low-voltage modulator for optical interconnects. IEEE J. Sel. Top. Quant. Electron. 11, 338–342 (2005).

    Article  ADS  Google Scholar 

  22. Xu, Q., Schmidt, B., Pradhan, S. & Lipson, M. Micrometre-scale silicon electro-optic modulator. Nature 435, 325–327 (2005).

    Article  ADS  Google Scholar 

  23. Gardes, F. Y. et al. High-speed modulation of a compact silicon ring resonator based on a reverse-biased pn diode. Opt. Express 17, 21986–21991 (2009).

    Article  ADS  Google Scholar 

  24. Dong, P. et al. Low Vpp, ultralow-energy, compact, high-speed silicon electro-optic modulator. Opt. Express 17, 22484–22490 (2009).

    Article  ADS  Google Scholar 

  25. You, J.-B., Park, M., Park, J.-W. & Kim, G. 12.5 Gbps optical modulation of silicon racetrack resonator based on carrier-depletion in asymmetric p-n diode. Opt. Express 16, 18340–18344 (2008).

    Article  ADS  Google Scholar 

  26. Watts, M. R., Trotter, D. C., Young, R. W. & Lentine, A. L. Ultralow power silicon microdisk modulators and switches. Proc. 5th IEEE Int. Conf. Group IV Photonics 4–6 (2008).

  27. Vlasov, Y. Silicon photonics for next generation computing systems. Proc. 34th European Conf. Optical Communications paper Tu.1.A.1 (2008).

  28. Gondarenko, A., Levy, J. S. & Lipson, M. High confinement micron-scale silicon nitride high Q ring resonator. Opt. Express 17, 11366–11370 (2009).

    Article  ADS  Google Scholar 

  29. Holzwarth, C. W. et al. Accurate resonant frequency spacing of microring filters without postfabrication trimming. J. Vac. Sci. Technol. B 24, 3244–3247 (2006).

    Article  Google Scholar 

  30. Teng, J. et al. Athermal silicon-on-insulator ring resonators by overlaying a polymer cladding on narrowed waveguides. Opt. Express 17, 14627–14633 (2009).

    Article  ADS  Google Scholar 

  31. Ye, W. N., Michel, J. & Kimerling, L. C. Athermal high-index-contrast waveguide design. IEEE Photon. Tech. Lett. 20, 885–887 (2008).

    Article  ADS  Google Scholar 

  32. Xu, Q., Fattal, D. & Beausoleil, R. G. Silicon microring resonators with 1.5-μm radius. Opt. Express 16, 4309–4315 (2008).

    Article  ADS  Google Scholar 

  33. Xiao, S., Khan, M. H., Shen, H. & Qi, M. A highly compact third-order silicon microring add-drop filter with a very large free spectral range, a flat passband and a low delay dispersion. Opt. Express 15, 14765–14771 (2007).

    Article  ADS  Google Scholar 

  34. Xia, F., Rooks, M., Sekaric, L. & Vlasov, Y. Ultra-compact high order ring resonator filters using submicron silicon photonic wires for on-chip optical interconnects. Opt. Express 15, 11934–11941 (2007).

    Article  ADS  Google Scholar 

  35. Manipatruni, S. et al. Wide temperature range operation of micrometer-scale silicon electro-optic modulators. Opt. Lett. 33, 2185–2187 (2008).

    Article  ADS  Google Scholar 

  36. Lee, J.-M. et al. Controlling temperature dependence of silicon waveguide using slot structure. Opt. Express 16, 1645–1652 (2008).

    Article  ADS  Google Scholar 

  37. Vlasov, Y., Green, W. M. J. & Xia, F. High-throughput silicon nanophotonic wavelength-insensitive switch for on-chip optical networks. Nature Photon. 2, 242–246 (2008).

    Article  Google Scholar 

  38. Guha, B., Kyotoku, B. B. C. & Lipson, M. CMOS-compatible athermal silicon microring resonators. Opt. Express 18, 3487–3493 (2010).

    Article  ADS  Google Scholar 

  39. Liao, L. et al. 40 Gbit/s silicon optical modulator for high-speed applications. Electron. Lett. 43, 1196–1197 (2007).

    Article  Google Scholar 

  40. Soref, R. A. & Bennett, B. R. Kramers–Kronig analysis of electro-optical switching in silicon. Proc. SPIE Integrated Optical Circuit Engineering IV 704, 32–37 (1987).

    Article  ADS  Google Scholar 

  41. Lorenzo, J. P. & Soref, R. A. 1. 3 μm electro-optic silicon switch. Appl. Phys. Lett. 51, 6–8 (1987).

    Article  ADS  Google Scholar 

  42. Friedman, L., Soref, R. A. & Lorenzo, J. P. Silicon double-injection electro-optic modulator with junction gate control. J. Appl. Phys. 63, 1831–1839 (1988).

    Article  ADS  Google Scholar 

  43. Treyz, G. V. Silicon Mach–Zehnder waveguide interferometers operating at 1.3 μm. Electron. Lett. 27, 118–120 (1991).

    Article  Google Scholar 

  44. Treyz, G. V., May, P. G. & Halbout, J.-M. Silicon optical modulators at 1.3-μm based on free-carrier absorption. IEEE Electr. Device Lett. 12, 276–278 (1991).

    Article  ADS  Google Scholar 

  45. Jackson, S. M. et al. A novel optical phase modulator design suitable for phased arrays. J. Lightwave Technol. 16, 2016–2019 (1998).

    Article  ADS  Google Scholar 

  46. Jackson, S. M. et al. Optical beamsteering using integrated optical modulators. J. Lightwave Technol. 15, 2259–2263 (1997).

    Article  ADS  Google Scholar 

  47. Fischer, U., Schuppert, B. & Petermann, K. Integrated optical switches in silicon based on SiGe-waveguides. IEEE Photon. Tech. Lett. 5, 785–787 (1993).

    Article  ADS  Google Scholar 

  48. Tang, C. K., Reed, G. T., Wilson, A. J. & Rickman, A. G. Low-loss, single-model optical phase modulator in SIMOX material. J. Lightwave Technol. 12, 1394–1400 (1994).

    Article  ADS  Google Scholar 

  49. Tang, C. K., Reed, G. T., Wilson, A. J. & Rickman, A. G. Simulation of a low loss optical modulator for fabrication in SIMOX material. Proc. Symp. Mater. Res. Soc. 298, 247–252 (1993).

    Article  Google Scholar 

  50. Tang, C. K. & Reed, G. T. Highly efficient optical phase modulator in SOI waveguides. Electron. Lett. 31, 451–452 (1995).

    Article  Google Scholar 

  51. Cutolo, A., Iodice, M., Spirito, P. & Zeni, L. Silicon electro-optic modulator based on a three terminal device integrated in a low-loss single-mode SOI waveguide. J. Lightwave Technol. 15, 505–518 (1997).

    Article  ADS  Google Scholar 

  52. Cutolo, A., Iodice, M., Irace, A., Spirito, P. & Zeni, L. An electrically controlled Bragg reflector integrated in a rib silicon on insulator waveguide. Appl. Phys. Lett. 71, 199–201 (1997).

    Article  ADS  Google Scholar 

  53. Sciuto, A., Libertino, S., Alessandria, A., Coffa, S. & Coppola, G. Design, fabrication, and testing of an integrated Si-based light modulator. J. Lightwave Technol. 21, 228–235 (2003).

    Article  ADS  Google Scholar 

  54. Hewitt, P. D. & Reed, G. T. Improving the response of optical phase modulators in SOI by computer simulation. J. Lightwave Technol. 18, 443–450 (2000).

    Article  ADS  Google Scholar 

  55. Hewitt, P. D. & Reed, G. T. Multi micron dimension optical p-i-n modulators in silicon-on-insulator. Proc. SPIE 3630, 237–243 (1999).

    Article  ADS  Google Scholar 

  56. Winney, T. et al. Single-chip variable optical attenuator and multiplexer subsystem integration. Optical Fiber Communication Conf. paper TuK4 (2002).

  57. Dainesi, P. et al. CMOS compatible fully integrated Mach-Zehnder interferometer in SOI technology. IEEE Photon. Tech. Lett. 12, 660–662 (2000).

    Article  ADS  Google Scholar 

  58. Png, C. E., Chan, S. P., Lim, S. T. & Reed, G. T. Optical phase modulators for MHz and GHz modulation in silicon-on-insulator (SOI). J. Lightwave Technol. 22, 1573–1582 (2004).

    Article  ADS  Google Scholar 

  59. Barrios, C. A., Almeida, V. R., Panepucci, R. & Lipson, M. Electrooptic modulation of silicon-on-insulator submicrometer-size waveguide devices. J. Lightwave Technol. 21, 2332–2339 (2003).

    Article  ADS  Google Scholar 

  60. Liu, A. et al. A high-speed silicon optical modulator based on a metal-oxide-semiconductor capacitor. Nature 427, 615–618 (2004).

    Article  ADS  Google Scholar 

  61. Liao, L. et al. High speed silicon Mach-Zehnder modulator. Opt. Express 13, 3129–3135 (2005).

    Article  ADS  Google Scholar 

  62. Kajikawa, K., Tabei, T. & Sunami, H. An infrared silicon optical modulator of metal-oxide-semiconductor capacitor based on accumulation-carrier absorption. Jpn. J. Appl. Phys. 48, 04C107 (2009).

    Article  Google Scholar 

  63. http://www.ofcnfoec.org/conference_program/2009/images/09-DAndrea.pdf

  64. Gardes, F. Y., Reed, G. T., Emerson, N. G. & Png, C. E. A sub-micron depletion-type photonic modulator in silicon on insulator. Opt. Express 13, 8845–8854 (2005).

    Article  ADS  Google Scholar 

  65. Liu, A. et al. High-speed optical modulation based on carrier depletion in a silicon waveguide. Opt. Express 15, 660–668 (2007).

    Article  ADS  Google Scholar 

  66. Marris-Morini, D. et al. Optical modulation by carrier depletion in a silicon PIN diode. Opt. Express 14, 10838–10843, (2006).

    Article  ADS  Google Scholar 

  67. Gunn, C. CMOS photonics for high-speed interconnects. IEEE Micro 26, 58–66 (2006).

    Article  Google Scholar 

  68. Park, J. W., You, J.-B., Kim, I. G. & Kim, G. High-modulation efficiency silicon Mach–Zehnder optical modulator based on carrier depletion in a PN Diode. Opt. Express 17, 15520–15524 (2009).

    Article  ADS  Google Scholar 

  69. Narasimha, A. et al. An ultra low power CMOS photonics technology platform for H/S optoelectronic transceivers at less than $1 per Gbps. Optical Fiber Communication Conf. paper OMV4 (2010).

  70. Liow, T.-Y. et al. Silicon modulators and germanium photodetectors on SOI: Monolithic integration, compatibility, and performance optimization. IEEE J. Sel. Top. Quant. Electron. 16, 307–315 (2010).

    Article  ADS  Google Scholar 

  71. Feng, N. N. et al. High speed carrier-depletion modulators with 1.4V-cm VπL integrated on 0.25μm silicon-on-insulator waveguides. Opt. Express 18, 7994–7999 (2010).

    Article  ADS  Google Scholar 

  72. Gill, D. M. et al. Internal bandwidth equalization in a CMOS-compatible Si-ring modulator. IEEE Photon. Tech. Lett. 21, 200–202 (2009).

    Article  ADS  Google Scholar 

  73. Spector, S. J. et al. High-speed silicon electro-optical modulator that can be operated in carrier depletion or carrier injection mode. Conf. Lasers and Electro-Optics paper CFH4 (2008).

  74. Manipatruni, S., Qianfan, X., Schmidt, B., Shakya, J. & Lipson, M. High speed carrier injection 18 Gb/s silicon micro-ring electro-optic modulator. IEEE Proc. Lasers and Electro-Optics Soc. 537–538 (2007).

  75. Png, C. E. Silicon-on-insulator phase modulators. PhD thesis, Univ. Surrey (2004).

    Google Scholar 

  76. Soljacic, M. et al. Photonic-crystal slow-light enhancement of nonlinear phase sensitivity. J. Opt. Soc. Am. B 19, 2052–2059 (2002).

    Article  ADS  Google Scholar 

  77. Jiang, Y., Jiang, W., Gu, L., Chen, X. & Chen, R. T. 80-micron interaction length silicon photonic crystal waveguide modulator. Appl. Phys. Lett. 87, 221105 (2005).

    Article  ADS  Google Scholar 

  78. Gu, L., Jiang, W., Chen, X., Wang, L. & Chen, R. T. High speed silicon photonic crystal waveguide modulator for low voltage operation. Appl. Phys. Lett. 90, 071105 (2007).

    Article  ADS  Google Scholar 

  79. Tanabe, T., Nishiguchi, K., Kuramochi, E. & Notomi, M. Low power and fast electro-optic silicon modulator with lateral p-i-n embedded photonic crystal nanocavity. Opt. Express 17, 22505–22513 (2009).

    Article  ADS  Google Scholar 

  80. Chen, X., Chen, Y. S., Zhao, Y., Jiang, W. & Chen, R. T. Capacitor-embedded 0.54 pJ/bit silicon-slot photonic crystal waveguide modulator. Opt. Lett. 34, 602–604 (2009).

    Article  ADS  Google Scholar 

  81. Li, J., White, T. P., O'Faolain, L., Gomez-Iglesias, A. & Krauss, T. F. Systematic design of flat band slow light in photonic crystal waveguides. Opt. Express 16, 6227–6232 (2008).

    Article  ADS  Google Scholar 

  82. Brimont, A., Sanchis, P. & Marti, J. Strong electro-optical modulation enhancement in a slow wave corrugated waveguide. Opt. Express 17, 9204–9211 (2009).

    Article  ADS  Google Scholar 

  83. Chen, L., Preston, K., Manipatruni, S. & Lipson, M. Integrated GHz silicon photonic interconnect with micrometer-scale modulators and detectors. Opt. Express 17, 15248–15256 (2009).

    Article  ADS  Google Scholar 

  84. Batten, C. et al. Building manycore processor-to-DRAM networks with monolithic silicon photonics. 16th IEEE Symp. High Performance Interconnects 21–30 (2008).

  85. Stojanovic, V., Joshi, A., Batten, C., Yong-jin, K. & Asanovic, K. Manycore processor networks with monolithic integrated CMOS photonics. Conf. Lasers and Electro-Optics/Int. Quantum Electronics Conf. paper CTuC3 (2009).

    Google Scholar 

  86. Zheng, X. et al. Ultra-low-energy all-CMOS modulator integrated with driver. Opt. Express 18, 3059–3070 (2010).

    Article  ADS  Google Scholar 

  87. Liu, L. et al. Carrier-injection-based electro-optic modulator on silicon-on-insulator with a heterogeneously integrated III–V microdisk cavity. Opt. Lett. 33, 2518–2520 (2008).

    Article  ADS  Google Scholar 

  88. Kuo, Y.-H., Chen, H.-W. & Bowers, J. E. High speed hybrid silicon evanescent electroabsorption modulator. Opt. Express 16, 9936–9941 (2008).

    Article  ADS  Google Scholar 

  89. Chen, H.-W., Kuo, Y. H. & Bowers, J. E. 25Gb/s hybrid silicon switch using a capacitively loaded traveling wave electrode. Opt. Express 18, 1070–1075 (2010).

    Article  ADS  Google Scholar 

  90. Hochberg, M. et al. Terahertz all-optical modulation in a silicon-polymer hybrid system. Nature Mater. 5, 703–709 (2006).

    Article  ADS  Google Scholar 

  91. Rong, Y. et al. Quantum-confined Stark effect in Ge/SiGe quantum wells on Si. IEEE J. Sel. Top. Quant. Electron. 16, 85–92 (2010).

    Article  ADS  Google Scholar 

  92. Liu, J. et al. Design of monolithically integrated GeSi electro-absorption modulators and photodetectors on an SOI platform. Opt. Express 15, 623–628 (2007).

    Article  ADS  Google Scholar 

  93. Preston, K., Manipatruni, S., Gondarenko, A., Poitras, C. B. & Lipson, M. Deposited silicon high-speed integrated electro-optic modulator. Opt. Express 17, 5118–5124 (2009).

    Article  ADS  Google Scholar 

  94. Della Corte, F. G., Rao, S., Nigro, M. A., Suriano, F. & Summonte, C. Electro-optically induced absorption in α-Si:H/α-SiCN waveguiding multistacks. Opt. Express 16, 7540–7550 (2008).

    Article  ADS  Google Scholar 

  95. Jacobsen, R. S. et al. Strained silicon as a new electro-optic material. Nature 441, 199–202 (2006).

    Article  ADS  Google Scholar 

  96. Hon, N. K., Tsia, K. K., Solli, D. R., Jalali, B. & Khurgin, J. B. Stress-induced χ(2) in silicon — comparison between theoretical and experimental values. Proc. 6th IEEE Int. Conf. Group IV Photonics 232–234 (2009).

  97. Xu, Q., Manipatruni, S., Schmidt, B., Shakya, J. & Lipson, M. 12.5 Gbit/s carrier-injection-based silicon micro-ring silicon modulators. Opt. Express 15, 430–436 (2007).

    Article  ADS  Google Scholar 

  98. Liao, L. High speed silicon-on-insulator modulators based on the free carrier plasma dispersion effect. PhD thesis, Univ. Surrey (2008).

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Reed, G., Mashanovich, G., Gardes, F. et al. Silicon optical modulators. Nature Photon 4, 518–526 (2010). https://doi.org/10.1038/nphoton.2010.179

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