Spectral broadening and temporal compression of ∼100 fs pulses in air-filled hollow core capillary fibers

Abstract

Abstract:We experimentally study the spectral broadening of intense, ∼100 femtosecond laser pulses at 785 nm coupled into different kinds of hollow core capillary fibers, all filled with air at ambient pressure. Differently from observations in other gases, the spectra are broadened with a strong red-shift due to highly efficient intrapulse Raman scattering. Numerical simulations show that such spectra can be explained only by increasing the Raman fraction of the third order nonlinearity close to 100%. Experimentally, these broadened and red-shifted pulses do not generally allow for straightforward compression using, for example, standard chirped mirrors. However, using special hollow fibers that are internally coated with silver and polymer we obtain pulse durations in the sub-20 fs regime with energies up to 300 µJ.

Nanomechanical Optical Fiber with Embedded Electrodes Actuated by Joule Heating

“…Many of these efforts were focused on control of dispersion, enhancement of the nonlinearity, reduction of the fiber transmission loss, or increase of sensitivity to environmental conditions in single-material MOFs [5]. Multi-material MOFs have also been developed for added functionality, e.g., hollow-core fibers filled with liquids [6] or gases [7] for sensing, with gases for high-power pulse compression [8,9] and nonlinear effects [10,11], with semiconductors for electronic functionality [12], and with integrated electrodes [13,14] and liquid crystals [15] for optical switching.…”

High-energy few-cycle pulses: post-compression techniques

“…Some sources require HCF scaling to opposite direction: those where either due to low pulse energy and/or long pulse duration the peak power is insufficient for using noble gases-filled HCFs for spectral broadening. In this case molecular gases offer a viable solution where molecular rotation (Raman scattering) cause a non-instantaneous nonlinear response [169] leading to a pronounced enhancement of the red side of the spectrum [140,170]. On the one hand this slow nonlinearity can be much larger than the instantaneous Kerr-effect which makes it suitable to the compression of low peak-power pulses, on the other hand the input pulse duration needs to be sufficiently long to experience the Raman-effect (>100 fs).…”

Raman Red‐Shift Compressor: A Simple Approach for Scaling the High Harmonic Generation Cut‐Off

“…Various approaches based on SRS have been reported in gas cells, [ 26,27 ] hollow‐core photonic crystal fibers, [ 28,29 ] and large‐diameter hollow‐core fibers (HCF). [ 22,23,30–32 ] Particularly, in the study by Safaei et al [ 32 ] , we describe a new regime of nonlinear propagation in HCFs that derives from the spatiotemporal nonlinear Raman enhancement observed with subpicosecond driver pulses. This mechanism allows for scaling the peak power by producing broadband, self‐frequency shifted solitons driven by subpicosecond pulses.…”