Diffractive and subwavelength grating couplers for microphotonic waveguides

DOIResolve DOI: http://doi.org/10.1109/ICTON.2012.6253914
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Proceedings titleICTON 2012: 14th International Conference on Transparent Optical Networks
Conference14th International Conference on Transparent Optical Networks, ICTON 2012, 2 July 2012 through 5 July 2012, Coventry
Article number6253914
Subject3 dB bandwidth; Back reflection; Coupling efficiency; Effective medium; Excitation field; Fabrication tolerances; Fundamental modes; Grating couplers; Higher-order modes; I-line steppers; Microphotonic waveguides; Multimodes; Silicon rib waveguides; Single etch; Sub-wave length grating; Sub-wavelength; Surface grating; Wavelength dependence; Wavelength ranges; Fabrication; Refractive index; Ridge waveguides; Transparent optical networks; Waveguides
AbstractWe review our advances in diffractive and subwavelength grating coupler structures for microphotonic waveguides. We present a subwavelength grating fiber-chip edge coupler with a loss as low as 0.9 dB and with minimal wavelength dependence over a broad wavelength range exceeding 200 nm. We also present fiber-to-chip surface grating couplers based on subwavelength effective medium. The effective medium refractive index is engineered to control the strength of the grating and thereby maximize coupling efficiency, while mitigating back reflections at the same time. We analyze the fabrication tolerances of the coupler, which are of particular relevance for large scale photonic fabrication. Furthermore, we present the first grating coupler for micrometric silicon rib waveguides, which is particularly challenging since the coupler waveguide region is multimode. We experimentally demonstrate grating couplers in 1.5 μm thick silicon ridge waveguides with a coupling efficiency of 2.2 dB and a 3 dB bandwidth of 40 nm. An inverse taper is used to match the fundamental mode of the interconnection waveguide with the optimum grating coupler excitation field, with negligible higher order mode excitation. The coupler was fabricated using i-line stepper lithography and single etch step. © 2012 IEEE.
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AffiliationInformation and Communication Technologies; National Research Council Canada
Peer reviewedYes
NPARC number21270093
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Record created2013-12-20
Record modified2016-05-09
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