Multiple-harmonic generation in rare gases at high laser intensity

TLDR

The study experimentally measures vacuum ultraviolet emission from a 15‑Torr rare‑gas medium under a 1064‑nm laser and analyzes phase‑matching conditions. The experiment uses a 1064‑nm laser at high intensity to generate harmonics in a 15‑Torr rare‑gas cell, measuring conversion efficiency versus laser intensity and gas density. Odd harmonics up to the 33rd in Ar, 29th in Kr, and 21st in Xe were observed, with a steep decline, plateau, and sharp cutoff in the harmonic spectrum.

Abstract

We present experimental measurements of vacuum ultraviolet light emission processes in a 15-Torr rare-gas medium exposed to a strong 1064-nm laser field. Apart from a small number of lines which correspond to discrete transitions, and a broad continuum emission, we essentially observe the odd harmonics of the laser field, up to very high order. At a 3\ifmmode\times\else\texttimes\fi{}${10}^{13}$ W ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$ laser intensity, the highest-order harmonics observed are the 33rd in Ar, the 29th in Kr, and the 21st in Xe. The harmonic distribution presents three regions: a steep decrease for the first harmonics, a plateau, and a sudden cutoff at high order. We study the variation of the conversion efficiency for some of the harmonics as a function of the incident laser intensity and the atomic density. Finally, we analyze the harmonic-generation results as thoroughly as possible, in particular, by characterizing the phase-matching conditions in our experiment.