We demonstrate that nonlinear frequency upconversion of few-cycle near-infrared (NIR) laser pulses, by means of harmonic generation in noble gases, is a promising approach for extending cutting-edge, few-cycle ultrafast technology into the deep ultraviolet and beyond, without the need for UV dispersion control. In our experiment, we generate 3.7-fs pulses in the deep UV (approximately 4.6 eV) with adjustable polarization and gigawatt-scale peak power. We demonstrate that the implementation of this concept with a quasi-monocycle driver offers the potential for advancing UV pulse generation towards the 1-fs frontier.

Intense few-cycle light pulses in the deep ultraviolet

A comprehensive analysis of the production and detection of circularly polarized VUV light using reflection optics is presented. Experimental results using gold reflectors are given. The necessary measurements to determine all Stokes parameters of an arbitrary VUV light beam are discussed.

Production and measurement of circular polarization in the VUV.

The Stokes parameters, which completely represent the polarization state of light, have been measured in the 5–80-eV energy region for synchrotron-radiation beams on the VUV to soft X-ray beamlines at the Photon Factory. Various states of polarization were produced for the emerging beam by deflecting the incoming beam vertically with respect to the entrance slit of the monochromator with a premirror of the beamline. The resultant beam was polarization-analyzed using a polarimeter comprising two triple-reflection polarizers. Increasing the beam-deflection angle was found to result in a change in the polarization state from predominantly horizontal linear polarization to elliptical polarization. This procedure could be used both to produce and to verify circular polarization with | P c | ≳ 80% in the energy range 60–80 eV, which could be immediately applied to MCD experiments. Unpolarized light could clearly be distinguished from circularly polarized light. The unpolarized component was found to become larger with increasing energy on a soft X-ray beamline; this was shown to be mainly due to scattering by beamline optical elements.

Elliptical-polarization analyses of synchrotron radiation in the 5–80-eV region with a reflection polarimeter

Previous measurements of the birefringence of sapphire and magnesium fluoride have been extended to their respective limits of transparency, revealing anomalous dispersion effects at short wavelengths, which are qualitatively discussed. Possible practical applications to Lyot filters and quarter-wave plates for Lyman-alpha are indicated.

Anomalous Dispersion of Birefringence of Sapphire and Magnesium Fluoride in the Vacuum Ultraviolet

Anomalous dispersion of birefringence of sapphire and magnesium fluoride in the vacuum ultraviolet

Polarization and phase shifts of Lyman-alpha flux reflected from Al, Al2O3, ZnS, MgF2, and SiO films were measured. A circular polarizer having a 5° angle of acceptance and 12% transmittance was constructed using Al2O3 and Al mirrors. The amount of flux in the desired state of circular polarization was between 83% and 90%.

Thomas J. McIlrath

Papers

Circular Polarizer for Lyman-alpha Flux*