Ultra‐compact and ultra‐broadband hybrid plasmonic‐photonic vertical coupler with high coupling efficiency, directivity, and polarisation extinction ratio

• Published in: IET optoelectronics 2022-06, Vol.16 (3), p.124-132
• Main Authors: Pezeshki, Hamed, Wright, Amanda J., Larkins, Eric C.
• Format: Article
• Language: English
• Subjects: plasmonics; surface plasmon resonance
• ISSN: 1751-8768; 1751-8776
• DOI: 10.1049/ote2.12063

An ultra‐compact, ultra‐broadband vertical coupler for dense photonic integrated circuits is reported with a 1.07 × 0.62 μm2 wavelength‐scale footprint. This hybrid plasmonic‐photonic coupler uses a unique two‐plane plasmonic nanoantenna array on a silicon‐on‐insulator waveguide. The in‐ and out‐of‐plane interference of the multipole moments and dual‐feed nanoantennas results in efficient, unidirectional coupling. Finite‐element simulations show that, for a 0.8 μm diameter Gaussian beam, the maximum coupling efficiency (CE) is −3.4 dB across the telecommunication C‐, L‐ and U‐bands with a 3‐dB bandwidth of 230 nm. The CE is > 9 dB higher than recently reported ultra‐compact plasmonic couplers. The maximum directivity and polarisation extinction ratio across the C‐ to U‐bands are 9.2 and 24.1 dB, respectively. Finally, as an out‐coupler, it has a vertical directivity of >8.5 dB, enabling its use for vertical optical interconnects between two vertically separated circuits.