Piston and tilt interferometry for segmented wave front sensing

Summary form only given. Segmented wave front phase measurement is a key technological topic for next generation of kHz lasers, which will be based on the combination of small-scale laser sources (fibers) before focusing on target, such as in Laser WakeField Acceleration (LWFA) [1].There are several methods to measure the relative piston (or average phase-shift) between beams at kHz bandwidth. However, most of them only measure piston and neglect tip/tilt information. We present here a new technique called PISTIL (PISton and TILt) [2], which measures absolute pistons (using λ disambiguation), as well as tilts of wave fronts segmented into regular hexagonal or Cartesian grids (Fig. 1.a).