Phase-dependent interference fringes in the wavelenght scaling of harmonic efficiency
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Künyeİlhan, Y., Bleda, E.A., Altun, Z., Topçu, T. (2014). Phase-dependent interference fringes in the wavelenght scaling of harmonic efficiency. Physical Review A. 89.5. 1-6.
We describe phase-dependent wavelength scaling of high-order harmonic generation efficiency driven by ultra-short laser fields in the mid-infrared. We employ both numerical solution of the time-dependent Schr¨odinger equation and the Strong Field Approximation to analyze the fine-scale oscillations in the harmonic yield in the context of channel-closing effects. We show, by varying the carrier-envelope phase, that the amplitude of these oscillations depend strongly on the rescattering electron trajectory counts. Furthermore, the peak positions of the oscillations vary significantly as a function of the carrier-envelope phase. Owing to its significant practical applications, we also investigate the wavelength dependence of harmonic yield in the single-cycle limit, finding that scaling near the cut-off region departs from the commonly observed λ −x behavior. For a fixed spectral range, we identify a surprisingly smooth behavior of x in λ −x as a function of the ionization potential in the single-cycle limit, which shows suppression of the oscillations in the overall wavelength-scaling. Moreover, we observe that the harmonic efficiency scales as λ −x with x = 5.2, independent from the target atom, and in reasonable agreement with the semi-classical x = 5 scaling.