Abstract: A dye laser for generating laser pulses of long duration comprising an optic resonator which comprises an elongated dye cell, which contains light gain medium that can be excited to population inversion, the outputs of the laser pulses from the dye cell being formed of the end surfaces of the cell. There are mirrors placed in optical connection with the outputs of the laser pulses of the dye cell, at least one of the mirrors being partially transmissive for feeding the laser pulse out. Furthermore, means comprising at least one elongated gas discharge lamp are arranged in the longitudinal direction of the dye cell to feed excitation light into the dye cell so that the excitation light sweeps across the cell in the lateral direction of the cell.