  Photoinjectors and Free Electron Lasers (FEL) are amongst the most advanced
systems in accelerator physics and have consistently pushed the boundaries of
emittance and x-ray peak power. In this paper, laser shaping at the cathode is
proposed to further lower the emittance and reduce electron beam tails, which
would result in brighter x-ray production. Using dispersion controlled
nonlinear shaping (DCNS), laser pulses and beam dynamics were simulated in
LCLS-II. The photoinjector emittance was optimized and the resulting e-beam
profiles were then simulated and optimized in the linac. Finally, the expected
FEL performance is estimated and compared to the current technology: Gaussian
laser pulses on the cathode. The e-beams produced by DCNS pulses show a
potential for 35% increase in x-ray power per pulse during SASE when compared
to the standard Gaussian laser pulses.
