Optical apparatus for amplifying pulses in a pulsed laser-beam includes a pulse-stretcher having a single transmission-grating in a multi-pass configuration at a non-normal incidence angle. A regenerative amplifier amplifies stretched pulses in the laser-beam. A pulse-compressor including two spaced-apart reflection-gratings in a multi-pass configuration compresses the amplified pulses. Pulse-parameters of the compressed amplified pulses are optimized by iteratively adjusting the incidence angle of the pulsed laser-beam on the transmission-grating of the pulse-stretcher and the spacing between the reflection-gratings of the pulse-compressor.