Generation of femtosecond optical vortices using a single refractive optical element

It is shown experimentally for small spectral bandwidth that spiral phase plates (SPPs) can generate optical vortices in femtosecond beams without the need for additional dispersion compensation elements. An autocorrelation measurement performed on the obtained optical vortex (OV) beam showed that the SPP did not significantly change the pulse duration. Hence the single element SPP, already an established beam shaping technique in continuous wave and high power regimes, is presented as an efficient and practical means to obtain OVs that are free from spatial chirp in femtosecond beams.