A multistep pulse compressor (MPC) based on a single-pass single-grating pair (SSGP) is proposed to simplify the entire multi-petawatt (PW) compressor. Only one grating pair with relatively long perpendicular distance is used to generate the same amount of spectral chirp compared with a four-grating main compressor. As SSGP compressor induces the largest spatial chirp, it can introduce the best beam-smoothing effect to the laser beam on the last grating. When considering the diffraction loss of only two gratings, the total compression efficiency of the SSGP compressor is even larger than that of a four-grating main compressor. Furthermore, the wavefront aberration induced by the SSGP compressor can be better compensated by using deformable mirrors; however, it is difficult or complicated to be well compensated in a four-grating compressor. Approximately 50–100 PW laser pulses can be obtained using this SSGP-based multistage-smoothing MPC with a single laser beam.

Studies of single-event laser-target interaction for fusion reaction schemes leading to volume ignition are discussed. Conditions were explored where single-event ns-laser pulses give rise to temperatures sufficient for volume ignition. Thus, ignition is possible, particularly if X-ray reabsorption is sufficiently high. Unfortunately, this scheme requires laser pulses with energies above 5 MJ and target densities of compressed DT above 1000 g/cm−3. Both requirements are quite demanding for near term systems. Nevertheless the present state technology and the detailed knowledge about volume ignition at direct drive are a basis. Systems as NIF or LMJ can well confirm these physics-clarified conditions and the technology for large laser systems with sufficient repetition rate and for a drastic reduction of the size and costs is necessary and possible and by physics similar to the known reductions in transistor development.