Skip to main content
. 2014 Feb 28;4:4234. doi: 10.1038/srep04234

Figure 1. Measured spectra with unusual spectral lines.

Figure 1

(a) Only harmonic lines of order q = 4i + 1 appear in the measured HHG spectra in the spectral range of 300–600 eV for a laser peak intensity of 8 × 1015 W/cm2. (b) At a peak intensity of approximately 5 × 1014 W/cm2, the harmonic lines appear at every odd harmonic position. (c) The harmonic lines and their quarter-optical-cycle periodicity can be resolved up to ~1 keV (1.2 nm) at 0.5 bar and 8 × 1015 W/cm2. High-order Fourier components (highlighted with green dashed lines) also appear. Standard harmonics of half-optical-cycle periodicity (highlighted by blue dashed lines) are generated in regions with a lower intensity in space and/or time.