ИСТИНА

Numerous applications of powerful femtosecond beam demands shaping of the beam transversal profile in the far or near diffractive zone – ranging from femtosecond filamentation to the dense plasma formation. We show that with specially designed diffractive optical elements (DOE) it is possible to form femtosecond beam of a desired shape at high peak power both after the DOE and in the focal spot. We studied different DOE forming high order Hermitt-Gaussian or modified Airy beams, as well as special DOE forming specific intensity distribution in the focal spot without phase jumps. We consider impact of a DOE onto the powerful femtosecond beam characteristics. In the case of HG and similar beams we showed that a DOE can be placed before the compressor to avoid DOE damage and lower acquired nonlinear phase. We present experimental data for the two applications: (i) regular plasma jets generation on the surface of liquid gallium and (ii) regularized multifilamentation in air.