Fig. 2: High harmonic generation in the perturbative multi-pulse (MP) regime. | Nature Communications

Fig. 2: High harmonic generation in the perturbative multi-pulse (MP) regime.

From: Generation of even and odd high harmonics in resonant metasurfaces using single and multiple ultra-intense laser pulses

Fig. 2

a Simplified schematic of the high harmonic generation (HHG) detection setup, with the detection arm represented by either a spectrometer or a back focal plane (BFP) imager. b MP-HHG spectra of the resonant sample at \({I}_{{\rm{MIR}}}=80\,{\rm{GW}}\,{{\rm{cm}}}^{-2}\). The N = 8 harmonic is not observed due to the onset of indirect interband transitions in GaP. The arrows indicate the predicted HHG wavelengths. c Polarization dependence of H5 shows two orders of magnitude contrast between the resonant (horizontal) and non-resonant (vertical) MIR polarizations with \({I}_{{\rm{MIR}}}=100\,{\rm{GW}}\,{{\rm{cm}}}^{-2}\). d Linear polarization of the odd-order (H7: green dots) and elliptic polarization of the even-order (H6: orange circles) harmonics. Dashed lines: MIR laser pulse polarization (\({I}_{{\rm{MIR}}}=80\,{\rm{GW}}\,{{\rm{cm}}}^{-2}\)). e Solid lines: HHG intensity as a function of the pump intensity for the N = 4 (dark red), N = 5 (red), N = 6 (orange), N = 7 (green), and N = 9 (blue) orders. Dashed lines: corresponding guide-to-the-eye power laws, \({I}^{(N)} \sim {I}_{{\rm{MIR}}}^{N}\).

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