Far-field spectral characterization of conical emission and filamentation in Kerr media

By use of an imaging spectrometer we map the far-field ($\theta-\lambda$) spectra of 200 fs optical pulses that have undergone beam collapse and filamentation in a Kerr medium. By studying the evolution of the spectra with increasing input power and using a model based on stationary linear asymptotic wave modes, we are able to trace a consistent model of optical beam collapse high-lighting the interplay between conical emission, multiple pulse splitting and other effects such as spatial chirp.Comment: 8 pages, 9 figure

Towards the generation of broadband optical vortices: extending the spectral range of a q-plate by polarization-selective filtering

Optical vortex beams in the visible and near-infrared spectrum over a wide spectral region are generated by a single S-waveplate polarization converter using polarization-selective filtering. A spectral coverage of 600 nm is demonstrated, with maximum efficiency at a wavelength of 530 nm. The broadband coverage is obtained using polarization filtering, which is applicable for any component based on geometric phase retardation. The efficiency of the filtering varies from 50% to 95% depending on the wavelength. This technique has potential application in stimulated emission microscopy and lithography