Simultaneous measurement of two ultrashort near-ultraviolet pulses produced by a multiplate continuum using dual self-diffraction dispersion-scan.

We present a new method based on self-diffraction dispersion-scan (SD d-scan) that enables the simultaneous measurement of two distinct ultrashort laser pulses in a region where they spatially and temporally overlap. This situation can arise when sampling and focusing two different spatial portions of a single inhomogeneous beam onto a medium. We demonstrate this new dual SD d-scan method by simultaneously characterizing two intense broadband ultraviolet pulses at 400 nm, with durations in the 10 fs range, originating from two different spatial portions of a beam produced by a multiplate continuum (MPC).

Inline self-diffraction dispersion-scan of over octave-spanning pulses in the single-cycle regime.

We present an implementation of dispersion-scan based on self-diffraction (SD d-scan) and apply it to the measurement of over octave-spanning sub-4-fs pulses. The results are compared with second-harmonic generation (SHG) d-scan. The efficiency of the SD process is derived theoretically and compared with the spectral response retrieved by the d-scan algorithm. The new SD d-scan has a robust inline setup and enables measuring pulses with over-octave spectra, single-cycle durations, and wavelength ranges beyond those of SHG crystals, such as the ultraviolet and the deep-ultraviolet.

Generation of high-energy vacuum UV femtosecond pulses by multiple-beam cascaded four-wave mixing in a transparent solid.

The generation of ultrashort vacuum UV (VUV) pulses by nondegenerate cascaded four-wave mixing of femtosecond pulses in a thin slide of a large band-gap transparent solid is numerically demonstrated. Using a novel noncollinear multiple-beam configuration, cascaded four-wave mixing of amplified 30 fs Ti:sapphire laser pulses at 800 nm, and their second harmonic in lithium fluoride results in the generation of VUV radiation down to 134 nm with energies in the µJ range and durations comparable to those of the pump pulses. The proposed geometry is advantageous in large dispersion scenarios, namely for generating radiation close to absorption bands. Hence these results set this technique as a promising way to efficiently generate ultrashort VUV radiation in solids for several applications in science and technology.

Octave-spanning spectra and pulse synthesis by nondegenerate cascaded four-wave mixing.

We present a theoretical model and 2D numerical simulation of cascaded four-wave mixing of femtosecond pulses in bulk chi((3)) media, evidencing the importance of 2D interaction geometries in the efficient generation of frequency-converted pulses. Octave-spanning spectra and pulse synthesis down to the sub-two-cycle regime is demonstrated without the need for complex amplitude or phase control, in agreement with experimental measurements.