Photonics Research Group Home
Ghent University Research Topics
About People Research Publications Education


Siliconnitride photonic integrated circuit platform

Research Area: Photonic integrated circuits for the visible/near IR , Silicon photonics for biomedical applications , Silicon photonics for lab-on-chip spectroscopy

Main Researcher: Ananth Subramanian

The field of integrated photonics has evolved to become a real world technology. But most of it is based on SOI based waveguide technology that takes advantage of its high-index-contrast and the mature CMOS processing leading to low-cost, high volume and efficient photonic circuits. In the recent years, there has been a tremendous demand for the CMOS-compatible technologies for “visible photonics” (λ= 400-1000 nm) mainly for bio-sensing application but also for nonlinear applications such as frequency comb and supercontinuum generation. For the lab-on-a-chip systems that are increasingly being used for detecting and sensing a range of biological species such as proteins DNA etc, wavelengths in the range of visible-very NIR are of particular interest due to negligible water absorption and minimal photo-damage to the cells. Unfortunately, silicon is not an ideal material to accomplish this because silicon is no longer transparent below 1.1 μm wavelength. Therefore, in order to derive the benefits of CMOS-based technology and high-index-contrast for smaller footprint whilst working in the visible-NIR wavelength range, silicon nitride (Si3N4) is the preferred choice of material.

Technology development
Si3N4 is a dielectric material with a refractive index ~ 2.0 and is transparent in the 400-5000 nm wavelength range. It has a lower thermal coefficient than silicon therefore less prone to thermal fluctuations and owing to lower-index-contrast than silicon, much lower loss can be achieved even at shorter wavelengths. It does not suffer from two-photon absorption and has a relatively high Kerr nonlinearity making it a viable material for on-chip nonlinear applications as well.
Under the umbrella of ERC grant InSpectra and in collaboration with IMEC, there is an ongoing activity for the development of PECVD based low-loss Si3N4 platform in the visible-NIR wavelength range. A significant progress has made towards developing stable technology for low-loss PECVD Si3N4 platform.

SEM of (a) Si3N4 waveguide cross-section, (b) complete cross-section & (c) GC with 630 nm period and 140 nm etch depth
SEM of (a) Si3N4 waveguide cross-section, (b) complete cross-section & (c) GC with 630 nm period and 140 nm etch depth

We achieved singlemode low-loss wire waveguides (clad and unclad) in the visible-NIR wavelength range. For the clad waveguides, losses measured were well below 1 dB/cm in the 532-900 nm wavelength range. For the unclad waveguides, losses < 1 dB/cm was achieved at λ=900 nm whereas losses were measured in the range of 1-3 dB/cm for λ=780 and 532 nm respectively. Measurements across different dies over a wafer yielded good uniformity pointing towards stable process for the waveguide fabrication. The index of the material was ~ 1.9 @ 785 nm
Grating couplers (air clad) at the wavelengths 780 and 900 nm have also been characterized to extract coupling efficiency of these couplers. Both the couplers exhibited a coupling efficiency of ~6.5 dB/coupler with a 1 dB bandwidth in the range of 25-30 nm. The efforts are underway to further improve the performance of various passive devices through further process developments, additional reflectors and post-processing techniques such as ALD.

The main objective of the Si3N4 technology development is geared towards a whole gamut of activities listed below:
GaAs VCSEL integration on SiN waveguide circuits
Raman spectroscopy on a siliconnitride waveguide platform
Nanoplasmonic approach for Raman spectroscopy on siliconnitride waveguides
Intracellular Raman spectroscopy sensing based on resonant photonic structures
Chi(3) VIS/NIR nonlinear optics in silicon-based waveguide circuits

Other people involved:

Related Research Projects


    International Journals

  1. X. Nie, E.M.P. Ryckeboer, G. Roelkens, R. Baets, CMOS-compatible broadband co-propagative stationary Fourier transform spectrometer integrated on a silicon nitride photonics platform, Optics Express, 25(8), United States, p.A409-A418 (2017)  Download this Publication (3.1MB).
  2. D. Martens, P. Bienstman, Comparison between Vernier-cascade and MZI as transducer for biosensing with on-chip spectral filter, Nanophotonics 2017, (2017)  Download this Publication (1.2MB).
  3. A. Hermans, C. Kieninger, K. Koskinen, A. Wickberg, E. Solano, J. Dendooven, M. Kauranen, S. Clemmen, M. Wegener, C. Koos, R. Baets, On the determination of chi(2) in thin films: a comparison of one-beam second-harmonic generation measurement methodologies, Scientific Reports, 7, p.44581 (2017)  Download this Publication (948KB).
  4. A. Rahim, E.M.P. Ryckeboer, A. Subramanian, S. Clemmen, B. Kuyken, A. Raza, A. Hermans, M. Muneeb, S. Dhoore, Y. Li, U.D. Dave, P. Bienstman, N. Le Thomas, G. Roelkens, D. Van Thourhout, Helin, Philiplle, Severi, Simone, Rottenberg, Xavier, R. Baets, Expanding the Silicon Photonics Portfolio with Silicon Nitride Photonic Integrated Circuits, Journal of Lightwave Technology (invited), 35(4), p.639-649 (2017)  Download this Publication (598KB).
  5. A. Van Eeghem, S. Werquin, J.F.I.B Hoste, A. Goes, E. Vanderleyden, P. Dubruel, P. Bienstman, Double positive effect of adding hexaethyelene glycol when optimizing the hybridization efficiency of a microring DNA detection assay, Applied Surface Science, p.321-328 (2017)  Download this Publication (1.7MB).
  6. A. Dhakal, P.C. Wuytens, A. Raza, N. Le Thomas, R. Baets, Silicon Nitride Background in Nanophotonic Waveguide Enhanced Raman Spectroscopy, Materials, 10(140), (2017)  Download this Publication (1.6MB).
  7. D. Martens, GENGHUA, Dong, P. Bienstman, Optimized Si3N4 grating couplers for relaxed alignment requirements under flood illumination, Applied Optics, 56(5), p.1286-1290 (2017).
  8. Luis Hoffman, A. Subramanian, Philippe Helin, , Bert Du Bois, R. Baets, Pol Van Dorpe, Georges Gielen, Robert Peurs, Dries Bracken, Low Loss CMOS-compatible PECVD Silicon Nitride Waveguides and Grating Couplers for Blue Light Optogenetic Applications, Photonics, (2016)  Download this Publication (1.2MB).
  9. A. Subramanian, E.M.P. Ryckeboer, A. Dhakal, F. Peyskens, A. Malik, B. Kuyken, H. Zhao, S. Pathak, A. Ruocco, A. De Groote, P.C. Wuytens, D. Martens, F. Leo, W. Xie, U.D. Dave, M. Muneeb, Pol Van Dorpe, Joris Van Campenhout, W. Bogaerts, P. Bienstman, N. Le Thomas, D. Van Thourhout, Zeger Hens, G. Roelkens, R. Baets, Silicon and silicon nitride photonic circuits for spectroscopic sensing on-a-chip , Photonics Research (invited), 5(3), p.B47 (2015)  Download this Publication (1.5MB).
  10. S. Werquin, D. Vermeulen, P. Bienstman, Implementation of Surface Gratings for Reduced Coupling Noise in Silicon-on-Insulator Circuits, IEEE Photonics Technology Letters, 26(16), p.1589 - 1592 (2014)  Download this Publication (663KB).
  11. A. Khanna, A. Subramanian, Hayrinen, Markus, S. Selvaraja, Verheyen, Peter, D. Van Thourhout, Honkanen,Seppo, Lipsanen, Harri, R. Baets, Impact of ALD grown passivation layers on silicon nitride based integrated optic devices for very-near-infrared wavelengths, Optics Express, 22(5), p.5684-5692 (2014)  Download this Publication (1.5MB).
  12. A. Subramanian, P. Neutens, A. Dhakal, R. Jansen, T. Claes, X. Rottenberg, F. Peyskens, S. Selvaraja, P. Helin, B. Du Bois, K. Leyssens, S. Severi, P. Deshpande, R. Baets, P. Van Dorpe, Low-loss singlemode PECVD silicon nitride photonic wire waveguides for 532-900 nm wavelength window fabricated within a CMOS pilot line, IEEE Photonics Journal, 5(6), p.2202809 (2013)  Download this Publication (683KB).
  13. A. Subramanian, S. Selvaraja, P. Verheyen, A. Dhakal, K. Komorowska, R. Baets, Near infrared grating couplers for silicon nitride photonic wires, IEEE Photonics Technology Letters, 24(19), p.1700-1703 (2012)  Download this Publication (411KB).
      International Conferences

    1. E.M.P. Ryckeboer, X. Nie, A. Dhakal, D. Martens, P. Bienstman, G. Roelkens, R. Baets, Spectroscopic sensing and applications in Silicon Photonics, International Conference on Group IV Photonics (invited), (2017).
    2. E.M.P. Ryckeboer, D. Martens, H. D'heer, P. Bienstman, D. Van Thourhout, R. Baets, Optofluidic devices based on Silicon photonics, EOS World of Photonics Congress (invited), (2017).
    3. A. Hermans, M. Van Daele, J. Dendooven, S. Clemmen, C. Detavernier, R. Baets, Electro-Optic Modulation in Silicon Nitride Photonic Integrated Circuits by means of ALD ZnO Overlays, European Conference on Integrated Optics (ECIO), Netherlands, p.T5.3 (2017)  Download this Publication (579KB).
    4. P.C. Wuytens, A.G. Skirtach, R. Baets, Nanotriangle Decorated Silicon Nitride Waveguides for Integrated Surface-Enhanced Raman Spectroscopy, CLEO: Science and Innovations 2017, STh1M(8), United States, (2017)  Download this Publication (392KB).
    5. A. Raza, P.C. Wuytens, F. Peyskens, S. Clemmen, P. V. Dorpe, R. Baets, On-chip Enhanced Raman spectroscopy using metal slot waveguide, European Conference on Integrated Optics (ECIO), 19(T7.4), Netherlands, (2017).
    6. S. Clemmen, A. Raza, A. Dhakal, F. Peyskens, A. Subramanian, P, Van Dorpe, P.C. Wuytens, H. Zhao, E.M.P. Ryckeboer, S. Severi, N. Le Thomas, R. Baets, Spectroscopic sensing with silicon nitride photonic integrated circuits, Photonics West 2017, Proc. SPIE 10106, Integrated Optics: Devices, Materials, and Technologies XXI (invited), United States, p.101060T (2017)  Download this Publication (1.6MB).

        Back to overview