Method for generating ultra-short light pulses, wherein one round trip of the ultra-short light pulse formation inside a generator optical loop, where pulse propagates in the closed trajectory, comprises the steps of: - amplification of the light pulse in an amplifier (5, 6); - spectral broadening of the amplified light pulse due to the optical Kerr effect in a first optically transparent material; - selecting spectral components of the spectrally broadened light pulses, using a first spectrally-sensitive optical element; - the first spectrally-sensitive optical element selects from light pulses the spectral components corresponding to a first predetermined range of wavelengths, while spectral components of light pulses of other wavelengths are directed away from the generator optical loop; - the light pulses of said first predetermined range of wavelengths selected using said first spectrally-sensitive optical element can be amplified again and further are spectrally broadened for a second time due to the optical Kerr effect in a second optically transparent material or in the above-mentioned first optically transparent material; - spectrally broadened light pulses for the second time are separated using a second spectrally-sensitive optical element by selecting from light pulses the spectral components coresponding to a second predetermined range of wavelengths, while spectral components of the light pulses of other wavelengths are directed away from the generator optical loop; - said cycle of the operation sequence is repeated by propagating the light pulses in the generator optical loop and formation of the ultra-short light pulses takes place, characterized in that the first predetermined range of wavelengths of the light pulses selected using the first spectrally-sensitive optical element differs from the second predetermined range of wavelengths of the light pulses selected using the second spectrally-sensitive optical element such that the first predetermined range of wavelengths does not overlap with the second predetermined range of wavelengths, or the first predetermined range of wavelengths may partly overlap with the second predetermined range of wavelengths but losses of the formed laser resonator in said optical loop due to the spectral overlap are higher than the amplification so that lasing does not start. - amplification of the light pulse in an amplifier (5, 6); - spectral broadening of the amplified light pulse due to the optical Kerr effect in a first optically transparent material; - selecting spectral components of the spectrally broadened light pulses, using a first spectrally-sensitive optical element; - the first spectrally-sensitive optical element selects from light pulses the spectral components corresponding to a first predetermined range of wavelengths, while spectral components of light pulses of other wavelengths are directed away from the generator optical loop; - the light pulses of said first predetermined range of wavelengths selected using said first spectrally-sensitive optical element can be amplified again and further are spectrally broadened for a second time due to the optical Kerr effect in a second optically transparent material or in the above-mentioned first optically transparent material; - spectrally broadened light pulses for the second time are separated using a second spectrally-sensitive optical element by selecting from light pulses the spectral components coresponding to a second predetermined range of wavelengths, while spectral components of the light pulses of other wavelengths are directed away from the generator optical loop; - said cycle of the operation sequence is repeated by propagating the light pulses in the generator optical loop and formation of the ultra-short light pulses takes place, characterized in that the first predetermined range of wavelengths of the light pulses selected using the first spectrally-sensitive optical element differs from the second predetermined range of wavelengths of the light pulses selected using the second spectrally-sensitive optical element such that the first predetermined range of wavelengths does not overlap with the second predetermined range of wavelengths, or the first predetermined range of wavelengths may partly overlap with the second predetermined range of wavelengths but losses of the formed laser resonator in said optical loop due to the spectral overlap are higher than the amplification so that lasing does not start.