Spectral modulation of high-order harmonic generation from prealigned CO_2 molecules

Abstract

We demonstrate experimentally that prealigned molecules produce observable spectral redshift or blueshift on the high-order harmonic generation. We distinguish two effects of molecular alignment on the phase modulation of the harmonics; one is from the gradient of alignment degree and the other is the plasma density varied by the molecular alignment. The finding provides an insight on the spectral distribution of molecular harmonics and a method of fine-tuning the harmonic spectrum.