Analysis of silicon nitride partial Euler waveguide bends

TL;DR

This paper analyzes and experimentally validates silicon nitride partial Euler waveguide bends at 850 nm, demonstrating reduced bend loss and enabling higher component density in photonic circuits.

Contribution

It provides a detailed analysis of loss mechanisms and introduces optimized partial Euler bends for improved waveguide performance.

Findings

Reduced bend loss with optimized Euler geometry

Experimental validation of theoretical models

Higher component density in photonic circuits

Abstract

In this work we present a detailed analysis of individual loss mechanisms in silicon nitride partial Euler bends at a wavelength of 850 nm. This structure optimizes the transmission through small radii optical waveguide bends. The partial Euler bend geometry balances losses arising from the transition from the straight to the bend waveguide mode, and radiative losses of the bend waveguide mode. Numerical analyses are presented for 45-degree bends commonly employed in S-bend configurations to create lateral offsets, as well as 90- and 180-degree bends. Additionally, 90-degree partial Euler bends were fabricated on a silicon nitride photonic platform to experimentally complement the theoretical findings. The optimized waveguide bends allow for a reduced effective radius without increasing the total bend loss and, thus, enable a higher component density in photonic integrated circuits.