a method of creating difference frequency laser pulses by difference frequency generation comprises the steps of providing ultrashort laser pulses having a spectral bandwidth corresponding to a fourier limit of below 50 fs and containing first spectral components and second spectral components having larger frequencies than the first spectral components , and driving a dfg process by the ultrashort laser pulses in an optically non - linear crystal , wherein the df laser pulses are generated in the crystal by difference frequencies between the first and second spectral components , resp ., said difference frequencies comprising third spectral components being lower in frequency than the first and second spectral components , wherein at least one enhancement cavity with resonator mirrors spanning a beam path is provided and the crystal is placed in the beam path of the enhancement cavity , the ultrashort laser pulses are input coupled and coherently added in the at least one enhancement cavity , at least one circulating ultrashort laser pulse is created in the at least one enhancement cavity , which drives the dfg process in the crystal for generating the df laser pulses , and the at least one enhancement cavity is adapted for recycling the at least one ultrashort laser pulse passing through the crystal . furthermore , a photonic source for creating df laser pulses is described , including one or more enhancement cavities .