A new deep blue extended super continuum light source is provided wherein said super continuum at least extends to a low wavelength border λlow low below 480 nm comprising a pump source which operates at a at least one wavelength λpump and produces pump pulses of a duration (full width half maximum) longer than 0.1 picoseconds with a repetition rate higher than 1 MHz, and a peak power λpeak, and a micro-structured optical transmission medium having at least one wavelength of zero dispersion λzero, and for the parameters for said pump source exhibiting a second order dispersion parameter β2, and a non-linear parameter λ arranged so that the optical transmission medium exhibits a modulation instability gain extending to wavelengths above a wavelength λhigh≧1300 nm and a phase match between λ1ow and a wavelength λmatch≧λhigh, wherein the pump is adapted to provide energy within the region of anomalous dispersion of the transmission medium.