Backscattering design for a focusing grating coupler with fully etched slots for transverse magnetic modes

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Veröffentlicht in:	Scientific reports Vol. 8. 2018, 1; Article-number 17746; insgesamt 8 Seiten
Personen und Körperschaften:	Hoffmann, Jahn (VerfasserIn), Schulz, Kai Marvin (VerfasserIn), Pitruzzello, Giampaolo (VerfasserIn), Fohrmann, Lena Simone (VerfasserIn), Petrov, Alexander (VerfasserIn), Eich, Manfred (VerfasserIn), Technische Universität Hamburg (Sonstige, Sonstige Körperschaft, 4oth), Technische Universität Hamburg Institut für Optische und Elektronische Materialien (Sonstige, Sonstige Körperschaft, 4oth)
Titel:	Backscattering design for a focusing grating coupler with fully etched slots for transverse magnetic modes/ Jahn Hoffmann, K. Marvin Schulz, Giampaolo Pitruzzello, Lena Simone Fohrmann, Alexander Yu Petrov & Manfred Eich
Format:	E-Book-Kapitel
Sprache:	Englisch
veröffentlicht:	2018
Gesamtaufnahme:	: Scientific reports, Vol. 8. 2018, 1; Article-number 17746; insgesamt 8 Seiten , volume:8
Quelle:	Verbunddaten SWB Lizenzfreie Online-Ressourcen

Details
Zusammenfassung:	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%.
Umfang:	Illustrationen, Diagramme 8
ISSN:	2045-2322
DOI:	10.1038/s41598-018-36082-z