Molecular alignment-assisted spectral broadening and shifting in the near-infrared with a recycled depleted pump from an optical parametric amplifier

TL;DR

This paper presents a novel method using recycled depleted pump pulses from an optical parametric amplifier to induce molecular alignment, resulting in significant spectral broadening and shifting in the near-infrared range.

Contribution

It introduces a new approach combining molecular alignment with nonlinear optics to achieve large spectral shifts and broadening using recycled pump pulses.

Findings

Spectral shifts up to 204 nm achieved.

Spectral broadening exceeds one octave.

Maximum shifts occur at specific polarization orientations.

Abstract

We demonstrate how the depleted pump of an optical parametric amplifier can be recycled for impulsive alignment of a molecular gas inside a hollow-core fiber and use such alignment for the broadening and frequency shift of the signal pulse at a center wavelength of $\sim 1300$nm. Our results combine non-adiabatic molecular alignment, self-phase modulation and Raman non-linearities. We demonstrate spectral shifts of up to 204 nm and a spectral broadening of more than one octave. We also report on the time delays at which broadening occurs, which do not coincide with any of the molecular rotational constants. Further, we encounter that maximum frequency shifts occur when the signal and pump have perpendicular polarization instead of parallel.