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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\u2019s length. Results were obtained by 2D-FDTD simulation. The designed grating couplers achieve coupling efficiencies for the TE-like mode over \u22128 dB (mask overlap) and \u22123 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.<\/jats:p>","DOI":"10.3390\/photonics11090783","type":"journal-article","created":{"date-parts":[[2024,8,26]],"date-time":"2024-08-26T04:48:25Z","timestamp":1724647705000},"page":"783","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Grating Coupler Design for Low-Cost Fabrication in Amorphous Silicon Photonic Integrated Circuits"],"prefix":"10.3390","volume":"11","author":[{"given":"Daniel","family":"Almeida","sequence":"first","affiliation":[{"name":"ISEL\u2014Instituto Superior de Engenharia de Lisboa, Instituto Polit\u00e9cnico de Lisboa, 1959-007 Lisboa, Portugal"},{"name":"CTS UNINOVA and LASI, 2829-516 Caparica, Portugal"},{"name":"NOVA School of Science and Technology, NOVA University Lisbon, 2829-516 Caparica, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8785-445X","authenticated-orcid":false,"given":"Paulo","family":"Louren\u00e7o","sequence":"additional","affiliation":[{"name":"ISEL\u2014Instituto Superior de Engenharia de Lisboa, Instituto Polit\u00e9cnico de Lisboa, 1959-007 Lisboa, Portugal"},{"name":"CTS UNINOVA and LASI, 2829-516 Caparica, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9938-0351","authenticated-orcid":false,"given":"Alessandro","family":"Fantoni","sequence":"additional","affiliation":[{"name":"ISEL\u2014Instituto Superior de Engenharia de Lisboa, Instituto Polit\u00e9cnico de Lisboa, 1959-007 Lisboa, Portugal"},{"name":"CTS UNINOVA and LASI, 2829-516 Caparica, Portugal"}]},{"given":"Jo\u00e3o","family":"Costa","sequence":"additional","affiliation":[{"name":"ISEL\u2014Instituto Superior de Engenharia de Lisboa, Instituto Polit\u00e9cnico de Lisboa, 1959-007 Lisboa, Portugal"},{"name":"CTS UNINOVA and LASI, 2829-516 Caparica, Portugal"}]},{"given":"Manuela","family":"Vieira","sequence":"additional","affiliation":[{"name":"ISEL\u2014Instituto Superior de Engenharia de Lisboa, Instituto Polit\u00e9cnico de Lisboa, 1959-007 Lisboa, Portugal"},{"name":"CTS UNINOVA and LASI, 2829-516 Caparica, Portugal"},{"name":"NOVA School of Science and Technology, NOVA University Lisbon, 2829-516 Caparica, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2024,8,23]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"622","DOI":"10.1038\/s41928-018-0173-2","article-title":"Terahertz integrated electronic and hybrid electronic\u2013photonic systems","volume":"1","author":"Sengupta","year":"2018","journal-title":"Nat. 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