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Tolerant silicon photonic microcircuits

Research Area: Design and Modeling for Integrated Photonics, Silicon photonics for telecom, datacom and interconnect , Large-scale Photonic Integration

Main Researcher: Sarvagya Dwivedi

In the past decade, silicon photonics has rapidly become one of the most promising photonic integration technologies.
The main reason is due to silicon has a very high refractive index, enabling optical waveguides with a very high refractive index contrast. The consequence of this is that waveguide cross sections can be shrunk to sub-micrometer dimensions, and the waveguides can be bent with only a few micrometer bend radius. Therefore, photonic circuits in silicon can be orders of magnitude smaller than their predecessors made in low-contrast glass. However, some of the strengths of silicon photonics also introduce weaknesses. The high refractive index contrast that allows the small waveguides and sharp bends also makes the waveguides terribly sensitive to any variation in the cross section. While good process control already allows nanometer-level accuracy, this is often insufficient for wavelength selective functions, such as channel drop filters in a wavelength-division multiplexing (WDM) system. Pre-fabrication or post-fabrication trimming of the components can be used to correct the effects of the last nanometer fabrication offsets. Also, silicon has a strong thermo-optic coefficient, meaning that its refractive index changes as a function of temperature. This is beneficial if it is used for tuning circuit elements, but that also implies additional power consumption. A passive silicon photonic circuit will therefore need temperature stabilization, or a method is needed to compensate for the thermo-optic effect of silicon. One method for this is the introduction of materials with opposite thermo-optic coefficients, such as polymers, but this introduced additional process complexity and it is not always desirable to incorporate such materials in a CMOS-like process flow.

Compact all- silicon athermal filter
Compact all- silicon athermal filter

We propose to address the tolerances not at the technology level, but rather through smart design solutions.For instance an a-thermal filter can be constructed by combining two waveguide geometries with a different thermo-optic coefficient, and this is achieved by just changing the width of the waveguide or polarization ( shown in the figure) , and thus the confinement of light in silicon.
The key challenge that we will address in this project is the poor tolerance of silicon photonic devices to variability, induced by both the manufacturing process and operational behavior. The research is on going for more complex circuits.

Other people involved:

Related Research Projects

PhD thesises


    International Journals

  1. A. Li, W. Bogaerts, Fundamental Suppression of Backscattering in Silicon Microrings, Optics Express, (2017)  Download this Publication (2.5MB).
  2. S. Dwivedi, A. Ruocco, M. Vanslembrouck, T. Spuesens, P. Bienstman, P. Dumon, T. Van Vaerenbergh, W. Bogaerts, Experimental Extraction of Effective Refractive Index and Thermo-Optic Coefficients of Silicon-On-Insulator Waveguides using Interferometers, Journal of Lightwave Technology , 33(21), p.4471 - 4477  (2015)  Download this Publication (854KB).
  3. S. Dwivedi, H. D'heer, W. Bogaerts, Maximizing fabrication and thermal tolerances of all-silicon FIR wavelength filtering devices, Photonics Technology Letters , 27(8), p.871-874 (2015)  Download this Publication (1.3MB).
  4. W. Bogaerts, M. Fiers, P. Dumon, Design Challenges in Silicon Photonics, J. Sel. Top. Quantum Electron., 20(4), p.1-8 (2014)  Download this Publication (363KB).
  5. S. Dwivedi, H. D'heer, W. Bogaerts, A compact all-silicon temperature insensitive filter for WDM and bio-sensing applications, IEEE Photonics Technology Letters , 25(22), p.2167 - 2170 (2013)  Download this Publication (903KB).
  6. P. De Heyn, J. De Coster, P. Verheyen, G. Lepage, M. Pantouvaki, P. Absil, W. Bogaerts, J. Van Campenhout, D. Van Thourhout, Fabrication-Tolerant Four-Channel Wavelength-Division-Multiplexing Filter based on Collectively Tuned Si Microrings, Journal of Lightwave Technology, 31(16), p.2785-2792 (2013)  Download this Publication (1.2MB).
      International Conferences

    1. W. Bogaerts, Scaling Up Silicon Photonic Circuits: Where Are the Challenges?, International Workshop on Optical/Photonic Interconnects for Computing Systems (OPTICS Workshop) (invited), 3, Switzerland, (2017)  Download this Publication (275KB).
    2. W. Bogaerts, Challenges for Designing Large-scale Integrated Photonics, European Conference on Integrated Optics (ECIO) / Workshop on Optical Waveguide Theory an Numerical Modeling (OWTNM) (invited), Poland, p.OWTNM-I-01 (2016)  Download this Publication (268KB).
    3. A. Ribeiro, S. Dwivedi, W. Bogaerts, A Thermally Tunable but Athermal Silicon MZI Filter, 18th European Conference in Integrated Optics 2016 (ECIO), Poland, p.paper ECIO/0-25 (2016)  Download this Publication (289KB).
    4. S. Dwivedi, P. De Heyn, P. Absil, J. Van Campenhout, W. Bogaerts, Coarse Wavelength Division Multiplexer on Silicon-On-Insulator for 100 GbE, 12th International Conference on Group IV Photonics (GFP), Canada, p.WC2 (2015)  Download this Publication (265KB).
    5. S. Dwivedi, T. Van Vaerenbergh, A. Ruocco, T. Spuesens, P. Bienstman, P. Dumon, W. Bogaerts, Measurements of Effective Refractive Index of SOI Waveguides using Interferometers, Integrated Photonics Research, Silicon and Nano Photonics (IPR 2015), United States, p.IM2A.6 (2015)  Download this Publication (1.4MB).
    6. S. Dwivedi, H. D'heer, W. Bogaerts, Fabrication tolerant silicon MZI filter, 11th International Conference on Group IV Photonics (GFP), France, p.147-148 (2014)  Download this Publication (644KB).
    7. S. Dwivedi, H. D'heer, W. Bogaerts, A compact temperature insensitive filter using splitter polarization-rotating section, Group IV Photonics, South Korea, p.WC6 (2013)  Download this Publication (1.1MB).
    8. S. Dwivedi, W. Bogaerts, Compact Athermal Filter in Silicon Waveguides for WDM and bio-sensing applications, Fiber Optics and Photonics 2012, p.M.2.B.3, India, (2012)  Download this Publication (480KB).

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