The invention relates to a device for the production of tuneable light impulses in a visible spectral range, comprising a laser system (LS) which emits femtosecond light impulses in the infrared spectral range, and an optical frequency converter (FC) for converting the wave lengths of the light impulses into the visible spectral range. According to the invention, the wave length of the light impulse emitted by the laser system can be tuned in order to provide said type of device which can be used as a light source for time-resolved fluorescence spectroscopy. Said device also comprises an optical stretcher which enables the duration of the impulse of the frequency converted light impulse to be increased to at least 1 ps.