Quantum path selection in high-order harmonic generation from aligned molecules.

Area of Science:

• Quantum optics
• Molecular physics
• Attosecond science

Background:

• High-order harmonic generation (HHG) is a key process for generating extreme ultraviolet (XUV) light.
• Controlling HHG in molecules offers unique pathways for light generation compared to atoms.

Purpose of the Study:

• To theoretically investigate HHG from aligned N2 molecules driven by two-color, circularly polarized laser pulses.
• To explore the selection of quantum pathways and its impact on XUV supercontinuum generation.
• To demonstrate control over attosecond pulse generation and intensity ratios.

Main Methods:

• Theoretical investigation of high-order harmonic generation.
• Utilizing aligned N2 molecules as the medium.
• Employing a driving field composed of two-color circularly polarized laser pulses.

Main Results:

• Demonstrated selection of either long or short quantum paths in N2 molecules by adjusting molecular alignment angles.
• Observed an ultrabroad and smooth XUV supercontinuum due to single quantum path selection.
• Achieved generation of isolated attosecond pulses.
• Showed control over the intensity ratio of attosecond pulses via molecular alignment.

Conclusions:

• Aligned N2 molecules combined with waveform-controlled laser fields enable selective quantum path contributions to HHG.
• This selectivity leads to the generation of isolated attosecond pulses and ultrabroad XUV supercontinua.
• The ability to control attosecond pulse characteristics opens possibilities for advanced attosecond pump-probe techniques.