Carrier-Envelope Offset-Free Pulse Train by Difference-Frequency Generation from a Si3N4-Waveguide Supercontinuum Output

We present a novel approach to generate a frequency comb based on Difference Frequency Generation (DFG). The frequency components required for the DFG process are generated in a Si 3 N 4 waveguide. A mode-locked 200 MHz oscillator is amplified in an Erbium-doped fiber, compressed to a duration of 42 fs and coupled into the waveguide. The power for generating the necessary spectral components in the waveguide is reduced by a factor of five compared to a setup based on highly nonlinear fiber.