Abstract: A method for providing an ensemble of beamlets effectively acting as a high-energy laser pulse is disclosed. According to the method, a beamlet pattern with a plurality of spatially distributed laser beamlets is provided. The beamlets are spread in time by introducing a different temporal delay to each of the beamlets. The beamlets are spectrally broadened. The beamlets are incoherently combined in space and time to provide the ensemble of beamlets. Also disclosed is a method for accelerating charged particles. Further disclosed is an optical arrangement for providing an ensemble of beamlets effectively acting as a high-energy laser pulse. The optical arrangement comprises a beamlet generating device providing a beamlet pattern of spatially distributed laser beamlets, a step optic for spreading the spatially distributed laser beamlets in time, a spectral broadening device, and a combining device for incoherently combining the spectrally broadened beamlets in space and time to provide the ensemble of beamlets.