Group velocity independent coupling into slow light photonic crystal waveguide on silicon nanophotonic integrated circuits

Slow light in photonic crystal waveguide can significantly enhance the light-matter interaction, which is a promising approach toward building ultra-compact photonic devices. However, optical coupling from strip waveguide to slow light photonic crystal waveguide is challenging due to the group velocity mismatch between these waveguides. This issue can be addressed by designing a photonic crystal taper that allows the defect guided mode in photonic crystal waveguide to slow down gradually when it enters the photonic crystal waveguide from strip waveguide, thereby minimizing the group velocity mismatch. By using the photonic crystal taper design, experimental results show coupling efficiency can be enhanced by more than 20dB in normal group velocity region with 5dB less fluctuation as compared to the control group, which does not have photonic crystal taper. Enhancement right before photonic bandgap cutoff can be up to 28dB. Measurement results show excellent agreement with two-dimensional (2D) finite-difference time domain (FDTD) simulation.

[1]  M. Notomi,et al.  Extremely large group-velocity dispersion of line-defect waveguides in photonic crystal slabs. , 2001, Physical review letters.

[2]  H. Hamann,et al.  Active control of slow light on a chip with photonic crystal waveguides , 2005, Nature.

[3]  T. Krauss,et al.  Ultracompact and low-power optical switch based on silicon photonic crystals. , 2008, Optics letters.

[4]  Thomas F. Krauss.  Slow light in photonic crystal waveguides , 2007 .

[5]  C M de Sterke,et al.  Efficient slow light coupling into photonic crystals. , 2007, Optics express.

[6]  Wei Jiang,et al.  High speed silicon photonic crystal waveguide modulator for low voltage operation , 2007 .

[7]  Ray T. Chen,et al.  Electro-optic polymer infiltrated silicon photonic crystal slot waveguide modulator with 23 dB slow light enhancement , 2010 .

[8]  Steven G. Johnson,et al.  Adiabatic theorem and continuous coupled-mode theory for efficient taper transitions in photonic crystals. , 2002, Physical review. E, Statistical, nonlinear, and soft matter physics.

[9]  Ray T. Chen,et al.  Photonic crystal slot waveguide absorption spectrometer for on-chip near-infrared spectroscopy of xylene in water , 2011 .

[10]  Marco Gnan,et al.  Efficient coupling into slow-light photonic crystal channel guides using photonic crystal tapers. , 2007, Optics express.

[11]  Yurii A Vlasov,et al.  Coupling into the slow light mode in slab-type photonic crystal waveguides. , 2006, Optics letters.

[12]  Ray T. Chen,et al.  Wideband group velocity independent coupling into slow light silicon photonic crystal waveguide , 2010 .

[13]  Wei Jiang,et al.  80-micron interaction length silicon photonic crystal waveguide modulator , 2005 .

[14]  Wei Jiang,et al.  Thermooptically Tuned Photonic Crystal Waveguide Silicon-on-Insulator Mach–Zehnder Interferometers , 2007, IEEE Photonics Technology Letters.