Although grating couplers have become the de-facto standard for optical access to integrated silicon photonics platforms, their performance at visible wavelengths, in moderate index contrast platforms such as silicon nitride, leaves significant room for improvement. In particular, the index contrast governs the diffraction efficiency per grating tooth and the resulting overall coupler length. In this work, we develop two approaches to address this problem: a dielectric grating that sums multiple optical modes to increase the overall output intensity; and an embedded metal grating that enhances the attainable refractive index contrast, and therefore reduces the on-chip footprint. We present experimental results that can be developed to realize compact efficient visible wavelength photonic interconnects, with a view toward cryogenic deployment for quantum photonics, where space is constrained and efficiency is critical.
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http://dx.doi.org/10.1364/OL.468275 | 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 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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