A very high-rate laser system that includes: - a mode-locking oscillator adapted to generate a source laser beam comprising a series of source pulses of femtosecond or picosecond duration, at a first repetition frequency, and - an optical amplifier system adapted to receive and amplify the series of source pulses to a second repetition frequency multiple of the first repetition frequency, the multiple being a natural integer number higher than or equal to two, so as to generate a series of laser pulses of very high repetition frequency, further including a repetition frequency multiplier device (4, 44) arranged between the oscillator and the optical amplifier system, the repetition frequency multiplier device (4, 44) comprising a first optical coupler-splitter, a first optical delay line and a second optical coupler-splitter having a first output, the first optical coupler-splitter being adapted to spatially split the source laser beam into a first pulse beam at the first repetition frequency and a second pulse beam at the first repetition frequency, the first optical delay line being arranged between the first optical coupler-splitter and the second optical coupler-splitter on a trajectory of the second pulse beam at the first repetition frequency, the first optical delay line being adapted to induce an optical delay equal to a half-period of the first repetition frequency on the second pulse beam and to generate a second pulse beam delayed by a half-period, and the second optical coupler-splitter being adapted to recombine the first beam and the second beam delayed by a half-period, and to form on the first output a first recombined beam in which the pulses are rated at the second repetition frequency equal to twice the first repetition frequency, characterized in that the first repetition frequency is higher than or equal to 800 megahertz. - a mode-locking oscillator adapted to generate a source laser beam comprising a series of source pulses of femtosecond or picosecond duration, at a first repetition frequency, and - an optical amplifier system adapted to receive and amplify the series of source pulses to a second repetition frequency multiple of the first repetition frequency, the multiple being a natural integer number higher than or equal to two, so as to generate a series of laser pulses of very high repetition frequency, further including a repetition frequency multiplier device (4, 44) arranged between the oscillator and the optical amplifier system, the repetition frequency multiplier device (4, 44) comprising a first optical coupler-splitter, a first optical delay line and a second optical coupler-splitter having a first output, the first optical coupler-splitter being adapted to spatially split the source laser beam into a first pulse beam at the first repetition frequency and a second pulse beam at the first repetition frequency, the first optical delay line being arranged between the first optical coupler-splitter and the second optical coupler-splitter on a trajectory of the second pulse beam at the first repetition frequency, the first optical delay line being adapted to induce an optical delay equal to a half-period of the first repetition frequency on the second pulse beam and to generate a second pulse beam delayed by a half-period, and the second optical coupler-splitter being adapted to recombine the first beam and the second beam delayed by a half-period, and to form on the first output a first recombined beam in which the pulses are rated at the second repetition frequency equal to twice the first repetition frequency, characterized in that the first repetition frequency is higher than or equal to 800 megahertz.