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arXiv · 1709.00397

Strong-field approximation in a rotating frame: High-order harmonic emission from p states in bicircular fields

Emilio Pisanty·Álvaro Jiménez-Galán
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Abstract

High-order harmonic generation with bicircular fields - the combination of counter-rotating circularly polarized pulses at different frequencies - results in a series of short-wavelength XUV harmonics with alternating circular polarizations, and experiments show that there is an asymmetry in the emission between the two helicities: a slight one in helium, and a larger one in neon and argon, where the emission is carried out by p-shell electrons. Here we analyze this asymmetry by switching to a rotating frame in which the field is linearly polarized; this induces an effective magnetic field which lowers the ionization potential of the $p_+$ orbital that co-rotates with the lower-frequency driver, enhancing its harmonic emission and the overall helicity of the generated harmonics, while also introducing nontrivial effects from the transformation to a non-inertial frame in complex time. In addition, this analysis directly relates the small asymmetry produced by s-shell emission to the imaginary part of the recollision velocity in the standard strong-field-approximation formalism.

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Emilio Pisanty, Álvaro Jiménez-Galán. 2017-09-01. Strong-field approximation in a rotating frame: High-order harmonic emission from p states in bicircular fields. https://doi.org/10.1103/physreva.96.063401

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