Broadband fiber-chip zero-order surface grating coupler with 0.4  dB efficiency.

Surface grating couplers enable efficient coupling of light between optical fibers and nanophotonic waveguides. However, in conventional grating couplers, the radiation angle is intrinsically wavelength dependent, thereby limiting their operation bandwidth. In this Letter, we present a zero-order surface grating coupler in silicon-on-insulator which overcomes this limitation by operating in the subwavelength regime. By engineering the effective refractive index of the grating region, both high coupling efficiency and broadband operation bandwidth are achieved. The grating is assisted by a silicon prism on top of the waveguide, which favors upward radiation and minimizes power losses to substrate. Using a linear apodization, our design achieves a coupling efficiency of 91% (-0.41  dB) and a 1-dB bandwidth of 126 nm.

[1]  R. Baets,et al.  Compact efficient broadband grating coupler for silicon-on-insulator waveguides. , 2004, Optics letters.

[2]  S. Janz,et al.  A broad-band waveguide grating coupler with a subwavelength grating mirror , 2006, IEEE Photonics Technology Letters.

[3]  Zach DeVito,et al.  Opt , 2017 .

[4]  P R Cooper,et al.  Refractive-index measurements of paraffin, a silicone elastomer, and an epoxy resin over the 500-1500-nm spectral range. , 1982, Applied optics.

[5]  Siegfried Janz,et al.  Broadband polarization independent nanophotonic coupler for silicon waveguides with ultra-high efficiency. , 2015, Optics express.

[6]  Dingshan Gao,et al.  High Efficiency and Broadband Two-Dimensional Blazed Grating Coupler With Fully Etched Triangular Holes , 2012, Journal of Lightwave Technology.

[7]  Wei Shi,et al.  Design of broadband subwavelength grating couplers with low back reflection. , 2015, Optics letters.

[8]  R. Ulrich,et al.  Theory of the Prism–Film Coupler by Plane-Wave Analysis , 1970 .

[9]  Roel Baets,et al.  High efficiency grating coupler between silicon-on-insulator waveguides and perfectly vertical optical fibers. , 2007, Optics letters.

[10]  S. T. Peng,et al.  Analysis and design of grating couplers , 1977 .

[11]  Dennis W Prather,et al.  Total internal reflection-evanescent coupler for fiber-to-waveguide integration of planar optoelectric devices. , 2004, Optics letters.

[12]  Siegfried Janz,et al.  Refractive index engineering with subwavelength gratings for efficient microphotonic couplers and planar waveguide multiplexers. , 2010, Optics letters.

[13]  Siegfried Janz,et al.  Waveguide sub‐wavelength structures: a review of principles and applications , 2015 .

[14]  R. Soref,et al.  The Past, Present, and Future of Silicon Photonics , 2006, IEEE Journal of Selected Topics in Quantum Electronics.

[15]  R. Ulrich,et al.  Optimum Excitation of Optical Surface Waves , 1971 .

[16]  Siegfried Janz,et al.  Subwavelength index engineered surface grating coupler with sub-decibel efficiency for 220-nm silicon-on-insulator waveguides. , 2015, Optics express.

[17]  T. Krauss,et al.  Compact and Highly Efficient Grating Couplers Between Optical Fiber and Nanophotonic Waveguides , 2007, Journal of Lightwave Technology.

[18]  Alejandro Ortega-Moñux,et al.  Fourier Based Combined Techniques to Design Novel Sub-Wavelength Optical Integrated Devices , 2012 .

[19]  Lee Carroll,et al.  Optimising apodized grating couplers in a pure SOI platform to -0.5 dB coupling efficiency. , 2015, Optics express.

[20]  Siegfried Janz,et al.  Waveguide grating coupler with subwavelength microstructures. , 2009, Optics letters.

[21]  Young-Kai Chen,et al.  Wide Bandwidth Silicon Nitride Grating Coupler , 2010, IEEE Photonics Technology Letters.