Weak optical modes for high-density and low-loss photonic circuits

Dielectric optical waveguides constitute the main building blocks of photonic integrated circuits (PICs). Channels with high refractive index contrast can provide very compact PIC components, whereas structures with lower index exhibit less propagation loss. A hybrid concept that can combine the best of high- and low-index materials is highly required. Here, we devise a new approach to realize compact and low-loss hybrid optical waveguides based on the interaction of weak optical modes. This is a rather universal approach that can be applied to a wide range of optical materials. To prove the principle, the hybrid waveguide structure is formed by combining a low-index polymer and a thin layer of silicon nitride. For this material combination, a minimum bending radius of 90 mu m (for a bending loss of 0.005 dB/90 degrees) and a propagation loss of 0.7 dB/cm are achieved. The viability of this platform is demonstrated through a series of high-performance novel PIC components. This hybrid waveguide platform enabled by a powerful and simple design concept holds great promise for high-density and low-loss PICs. (c) 2023 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

We developed a new approach to achieve compact and low-loss hybrid optical waveguides by utilizing the interaction of weak optical modes and combining high-index and low-index materials. By combining a low-index polymer and a thin layer of silicon nitride, we achieved a minimum bending radius of 90 μm (with a bending loss of 0.005 dB/90 degrees) and a propagation loss of 0.7 dB/cm. The viability of this technology was demonstrated through a series of high-performance novel photonic integrated circuit components. This hybrid waveguide platform, enabled by a powerful and simple design concept, holds great promise for high-density and low-loss PICs.