Petahertz-bandwidth spectral combs from the amplified spontaneous emission of a collisional plasma-based x-ray laser

TL;DR

This paper demonstrates the generation of petahertz-bandwidth spectral combs from a collisional plasma-based x-ray laser's amplified spontaneous emission when irradiated with a near-infrared laser, enabling ultrafast extreme ultraviolet radiation control.

Contribution

It introduces a novel method to produce and manipulate spectral combs in the petahertz range using plasma-based x-ray lasers and IR field modulation.

Findings

Spectral combs with petahertz bandwidth are generated from plasma x-ray lasers.

IR field intensity controls the transition between combs and quasimonochromatic emission.

Frequency tuning range of XUV radiation is approximately twice the IR modulation frequency.

Abstract

The possibility of generating spectral combs of petahertz bandwidth is demonstrated from amplified spontaneous emission (ASE) of a collisional plasma-based x-ray laser when its active medium is irradiated with a linearly polarized near-infrared (IR) laser field. It is shown that at a sufficiently high IR-field intensity these combs correspond to a sequence of subfemtosecond beats of extreme ultraviolet (XUV) radiation of a deterministic shape. At the same time, at a lower IR-field intensity ASE remains quasimonochromatic, but its frequency shifts as a result of the IR-field-induced quadratic Stark effect. In this case, the frequency tuning range of XUV radiation is approximately twice the frequency of the modulating IR field. In addition, modulation by the IR field leads to amplitude and frequency discrimination of the polarization components of ASE, parallel and orthogonal to the IR field. The possibility of observing these effects is analyzed for a collisional plasma x-ray laser based on neon-like Ti12+ ions with an unperturbed ASE wavelength of 32.6 nm and a modulating field with a wavelength of 1 {\mu}m and an intensity in the range of 10^16 - 10^17 W/cm^2.