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Generating few-cycle radially polarized pulses

A radially polarized beam is axially symmetric and is able to produce tightly focused light fields beyond the Gaussian beam diffraction limit. However, with the current technology, its duration is limited by the relatively narrow bandwidth that the generation techniques can support. Using a 10 cycle pulse with a central wavelength of 1.8 μm, we show that radially polarized beams can be compressed to the few-cycle regime, while still maintaining their radially polarized nature. Therefore, it seems feasible, using only well-developed methods, to reach focused intensities of ∼1019  W/cm2. Conversion via high-harmonic generation will also open a route for applications in attosecond science, especially for a wide range of optical measurements and optical control that require high spatial and high temporal resolution.