Specific features of direct formation of graphite-like microstructures in polycarbonate samples by single femtosecond laser pulses

We present the result of the experiments on producing graphite-like cylindrical microstructures by focusing single femtosecond laser pulses into the bulk of a transparent polymer (polycarbonate). The microstructures are embedded in a cladding with a modified refractive index, possessing waveguide properties. In the experiments with nontransparent screens and diaphragms, placed in the laser beam in front of the entrance pupil of the objective with a large numerical aperture, we have found that the paraxial rays are blocked by the peripheral ones, which reduces the length of the destruction region in the pre-focal zone. In the experiments with transparent screens and diaphragms, introducing optical delays τ_d between the paraxial and peripheral rays, the quantitative dependence of the destruction region length in the pre-focal zone on the value of τ_d is determined.