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Advisor(s)
Abstract(s)
Photonic circuits find applications in biomedicine, manufacturing, quantum computing and
communications. Photonic waveguides are crucial components, typically having cross-section orders
of magnitude inferior when compared with other photonic components (e.g., optical fibers, light
sources and photodetectors). Several light-coupling methods exist, consisting of either on-plane (e.g.,
adiabatic and end-fire coupling) or off-plane methods (e.g., grating and vertical couplers). The grating
coupler is a versatile light-transference technique which can be tested at wafer level, not requiring
specific fiber terminations or additional optical components, like lenses, polarizers or prisms. This
study focuses on fully-etched grating couplers without a bottom reflector, made from hydrogenated
amorphous silicon (a-Si:H), deposited over a silica substrate. Different coupler designs were tested,
and of these we highlight two: the superimposition of two lithographic masks with different periods
and an offset between them to create a random distribution and a technique based on the quadratic
refractive-index variation along the device’s length. Results were obtained by 2D-FDTD simulation.
The designed grating couplers achieve coupling efficiencies for the TE-like mode over −8 dB (mask
overlap) and −3 dB (quadratic variation), at a wavelength of 1550 nm. The coupling scheme considers
a 220 nm a-Si:H waveguide and an SMF-28 optical fiber.
Description
Keywords
Grating coupler Light coupling Photonic waveguide Silicon-on-insulator Amorphous silicon Off-plane coupling
Citation
Almeida, D.; Lourenço, P.; Fantoni, A.; Costa, J.; Vieira, M. Grating Coupler Design for Low-Cost Fabrication in Amorphous Silicon Photonic Integrated Circuits. Photonics 2024, 11(9), 783. https://doi.org/10.3390/photonics11090783
Publisher
MDPI