Efficient coupling between thin-film plasmonic and SiN photonic waveguide

Bringing photonics and electronics into a common integration platform can unleash unprecedented performance capabilities in data communication and sensing applications. Plasmonics were proposed as the key technology that can merge ultra-fast photonics and low-dimension electronics due to their metallic nature and their unique ability to guide light at subwavelength scales. However, inherent high losses of plasmonics impede their practical deployment in PICs. To ameliorate this limitation, selective integration of individual nano-plasmonic devices on low-loss photonic platforms is considered, allowing for enhanced chip-scale functionalities with realistic power budgets. Likewise, highly-efficient and fabrication-tolerant optical interfaces for co-planar plasmonic and photonic waveguides become essential, bridging these two “worlds” and ease combined high-volume manufacturing. In this work, a TM-mode butt-coupled interface for stoichiometric Si3N4 and gold-based thin-film plasmonic waveguides is proposed aiming to be utilized for bio-sensing applications. Following a systematic design process, this new configuration has been analyzed through 3D FDTD numerical simulations demonstrating interface insertion losses of 2dB at the wavelength of 1550 nm, with increased fabrication tolerance compared to silicon based waveguide alternatives.