Fourier transform with matched non-linear frequency modulation in femtosecond laser ranging with imbalanced dispersion.

We propose a new algorithm based on the Fourier transform with matched non-linear frequency modulation for processing femtosecond laser ranging data. The algorithm allows us to compensate for both the influence of the third-order dispersion in the fiber-based dispersive Fourier spectrometer and the influence of imbalanced second- and third-order dispersions in the interferometer. Computer simulations and experimental results show that the proposed algorithm significantly increases the accuracy of measuring the position of an object at larger displacements than the well-established non-linear time stretching.

Giantically blue-shifted visible light in femtosecond mid-IR filament in fluorides.

A giant blue shift (more than 3000 nm) of an isolated visible band of supercontinuum was discovered and studied in the single filament regime of Mid-IR femtosecond laser pulse at powers slightly exceeding critical power for self-focusing in fluorides. At the pulse central wavelength increasing from 3000 nm to 3800 nm the spectral maximum of the visible band is shifted from 570 nm and 520 nm up to 400 nm and 330 nm for BaF(2) and CaF(2), respectively, its spectral width (FWHM) being reduced from 50 - 70 nm to 14 nm. It is shown that the formation of this narrow visible wing is a result of the interference of the supercontinuum components in the anomalous group velocity dispersion regime.

Anti-Stokes wing of femtosecond laser filament supercontinuum in fused silica.

We have demonstrated that in the IR pulse filament the anomalous dispersion of fused silica leads to the formation of an isolated anti-Stokes wing (ASW), which is located in the visible region of the supercontinuum (SC). It is shown that the isolated ASW is formed by the interference of the light field of a SC undergoing anomalous group velocity dispersion.