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https://doi.org/10.15480/882.1988
Publisher DOI: | 10.1038/s41598-018-36082-z | Title: | Backscattering design for a focusing grating coupler with fully etched slots for transverse magnetic modes | Language: | English | Authors: | Hoffmann, Jahn Schulz, Kai Marvin Pitruzzello, Giampaolo Fohrmann, Lena Simone Petrov, Alexander Yu ![]() Eich, Manfred |
Issue Date: | 10-Dec-2018 | Publisher: | Macmillan Publishers Limited, part of Springer Nature | Source: | Scientific Reports 1 (8): - (2018-12-01) | Abstract (english): | Grating couplers are a fundamental building block of integrated optics as they allow light to be coupled from free-space to on-chip components and vice versa. A challenging task in designing any grating coupler is represented by the need for reducing back reflections at the waveguide-grating interface, which introduce additional losses and undesirable interference fringes. Here, we present a design approach for focusing TM grating couplers that minimizes these unwanted reflections by introducing a modified slot that fulfills an anti-reflection condition. We show that this antireflection condition can be met only for the Bloch mode of the grating that concentrates in the dielectric. As a consequence the light is scattered from the grating coupler with a negative angle, referred to as “backscattering design”. Our analytic model shows that the anti-reflection condition is transferrable to grating couplers on different waveguide platforms and that it applies for both TE and TM polarizations. Our experimentally realized focusing grating coupler for TM-modes on the silicon photonics platform has a coupling loss of (3.95 ± 0.15) dB at a wavelength of 1.55 µm. It has feature sizes above 200 nm and fully etched slots. The reflectivity between the grating coupler and the connected waveguide is suppressed to below 0.16%. |
URI: | https://hdl.handle.net/11420/1991 | DOI: | 10.15480/882.1988 | ISSN: | 2045-2322 | Journal: | Scientific reports | Institute: | Optische und Elektronische Materialien E-12 | Document Type: | Article | Project: | Open Access Publizieren 2018 - 2019 / TU Hamburg Mid infrared gas sensing |
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