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

TL;DR

This paper introduces a universal hybrid optical waveguide approach using weak optical modes, combining low-loss and high-density advantages for photonic integrated circuits.

Contribution

A new hybrid waveguide design based on weak optical modes that is applicable to various materials and achieves low loss and high compactness.

Findings

Achieved a minimum bending radius of 90 microns with low bending loss.

Demonstrated an upper limit of 0.7 dB/cm optical loss.

Validated the platform with high-performance PIC components.

Abstract

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 micron (for a bending loss of 0.005 dB/90o ) and an upper limit for the optical 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.