Theoretical investigation of elliptical high-order harmonic generation from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msubsup> <mml:mi>H</mml:mi> <mml:mn>2</mml:mn> <mml:mo>+</mml:mo> </mml:msubsup> </mml:mrow> </mml:m

Abstract We theoretically investigate the elliptical high-order harmonic generation from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi mathvariant="normal">H</mml:mi> <mml:mn>2</mml:mn> <mml:mo>+</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> in two-color cross-linearly-polarized laser fields by numerically solving the two-dimensional time-dependent Schrödinger equation. Numerical simulations show that the crossing-angle-dependent harmonic ellipticity exhibits a prominent antisymmetric structure, which tends to disappear as the internuclear distance increases. Furthermore, ground-state electrons experience resonant transitions to the first excited state at larger internuclear distances, where the disruption of symmetric electron motion suppresses the antisymmetric structure. Additionally, a near-circularly-polarized attosecond pulse can be obtained by modulating the crossing angle.