Optical frequency comb sources based on quadratic nonlinearities provide an interesting alternative to Kerr combs in terms of reduced pump power requirements and extended spectral coverage. We review theory and recent experiments of quadratic optical frequency combs based on second-harmonic generation and optical parametric oscillation.
Funding Agencies|Ministero dellIstruzione, Universita e Ricerca (MIUR) (2015KEZNYM-NEMO); H2020 European Research Council (ERC)European Research Council (ERC) [757800]