Silicon nitride waveguide as a power delivery component for on-chip dielectric laser accelerators

Abstract

We study the weakly guided silicon nitride waveguide as an on-chip power delivery solution for dielectric laser accelerators (DLAs). We focus on the two main limiting factors on the waveguide network for DLAs: the optical damage and nonlinear characteristics. The typical delivered fluence at the onset of optical damage is measured to be ∼0.19 J/cm² at a 2 μm central wavelength and 250 fs pulse width. This damage fluence is lower than that of the bulk Si₃N₄ (∼0.65 J/cm²), but higher than that of bulk silicon (∼0.17 J/cm²). We also report the nonlinearity-induced spectrum and phase variance of the output pulse at this pulse duration. We find that a total waveguide length within 3 mm is sufficient to avoid significant self-phase modulation effects when operating slightly below the damage threshold. We also estimate that one SiN_x waveguide can power 70 μm silicon dual pillar DLAs from a single side, based on the results from the recent free-space DLA experiment.