High-energy laser-pulse self-compression in short gas-filled fibers

Abstract

We examine the spatio-temporal compression of energetic femtosecond laser pules within short gas filled fibers. The study is undertaken using an advanced nonlinear pulse propagation model based on a multimode generalized nonlinear Schrödinger equation that has been modified to include plasma effects. Plasma defocusing and linear propagation effects are shown to be the dominant processes within a highly dynamical mechanism that enables 100 fs pulses to be compressed into the fewcycle regime after <50 mm of propagation. Once the mechanism has been introduced, parameter spaces are explored and compressor designs suitable for performing high-field experiments in-situ are presented. We finish by showing how these designs may be extended to novel wavelengths and driving pulses delivered by state of the art high repetition rate lasers.

Extremely Nonlinear Optics Using Shaped Pulses Spectrally Broadened in an Argon- or Sulfur Hexafluoride-Filled Hollow-Core Fiber

“…Since the description of the propagation of the generating IR laser pulse and the harmonic radiation is full of twists and turns [24][25][26], i.e., Equations (1) and (5) suggest a complex intensity and wavelength dependence, the implementation of an evolutionary algorithm for finding the best suited pulse-shape is an established technique. (a) is a typical HHG spectrum from a hollow-core fiber with a pulse that is compressed by translating the prisms for highest XUV yield and using a flat mirror surface; (b) shows an optimization of the overall yield by adaptively shaping the deformable mirror.…”

Toward spatial and spectral control of waveguided high-harmonic generation

“…The second mechanism may be called intrinsic, i.e., when fluctuations are rather based on highly nonlinear effects in the capillary such as associated with spatio-temporal reshaping of the drive laser pulse inside the capillary. It has recently been observed in an identical waveguiding capillary that such reshaping is related to beating of drive laser light propagating simultaneously in the fundamental and higher-order modes that are excited through ionization-induced scattering of the driving laser pulse [57,95] . Furthermore, the modeling in [95] showed that nonlinear optical effects like self-phase modulation or self-steepening do not significantly modify the pulse propagation in such a capillary.…”

“…It has recently been observed in an identical waveguiding capillary that such reshaping is related to beating of drive laser light propagating simultaneously in the fundamental and higher-order modes that are excited through ionization-induced scattering of the driving laser pulse [57,95] . Furthermore, the modeling in [95] showed that nonlinear optical effects like self-phase modulation or self-steepening do not significantly modify the pulse propagation in such a capillary. This is confirmed by calculating the characteristic propagation length required for these processes to become dominant [94].…”

“…3.4a and b and stable from shot-to-shot. This suggests that under these conditions, i.e., high pressure and high pulse energy, the complex, ionization-induced nonlinear dynamics creates a single propagating mode for the driving laser pulse [95]. Although this mode will be very different from the fundamental (empty) waveguide mode, it will produce stable and reproducible XUV output in a similar way.…”

“…For instance, via ionization-induced spectral broadening and plasma-induced refraction the drive pulses can undergo self-compression [57,94]. Similarly, intensity dependent index changes can distort the wave fronts of the driving laser pulse, thereby exciting propagation in multiple waveguide modes (higher-order modes), the superposition of which creates spatio-temporal hot spots that further distort the drive laser propagation [57,95]. Eventually, there might also be simple, direct effects.…”