Grating couplers are proposed for polarization-independent coupling of light between a single-mode fiber and a 220-nm-thick channel waveguide on silicon-on-insulator. The grating couplers have nonuniform grating periods that are composed of the intersection or union of a set of two near-optimal TE- and TM-grating periods. The proposed grating couplers have a coupling efficiency greater than 20% and polarization dependent loss (PDL) lower than 0.5 dB within 3-dB bandwidth in design. For the evaluation of the design concept, a fabricated intersection grating coupler has the PDL of less than 0.8 dB within the wavelength range of 1540 to 1560 nm, and the coupling efficiency is ∼18%.
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http://dx.doi.org/10.1364/OL.40.003941 | DOI Listing |
Grating-assisted, contra-directional couplers (GA-CDCs), owing to their four-port operations, can offer several important advantages over traditional, single waveguide-based Bragg gratings. However, how to flexibly design the spectral responses of GA-CDCs has been much less studied. We report the spectral tailoring methodology of GA-CDCs to achieve arbitrary, physically realizable, complex spectral responses.
View Article and Find Full Text PDFPolymer photonics is receiving significant attention due to its potential for a wide range of integrated photonic applications and wide wavelength transparency. Wafer-scale testing is challenging due to low-index contrast in polymer waveguides. In this Letter, we demonstrate an amorphous silicon based out-of-plane polymer waveguide grating coupler.
View Article and Find Full Text PDFWe propose and validate a new, to the best of our knowledge, approach for high coupling efficiency polarization splitting waveguide grating couplers (PSWGCs). The high coupling efficiency is achieved by using a polysilicon overlay grating, which is shifted with respect to the underlying silicon grating. The PSWGC is designed to couple the two orthogonal polarizations in different directions.
View Article and Find Full Text PDFSurface grating couplers, such as fiber-chip grating couplers and optical antennas, are fundamental devices in photonic integrated circuits, as they enable the coupling of light between the chip and an external medium. An important metric of surface grating couplers is the coupling efficiency, and high values, greater than -1 dB, are required for applications in quantum technology, light detection and ranging, and optical interconnects. Surface grating couplers typically suffer from radiation loss to the substrate, which significantly limits their coupling efficiency.
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