Proposal to generate a pair of intense independently tunable attosecond pulses from undulator radiation

We propose and numerically evaluate two schemes to generate a pair of extreme-ultraviolet monocycle pulses with gigawatt-level peak power, whose time delay and central wavelengths can be precisely controlled. The methods are based on coherent emission of radiation by an ultrarelativistic electron beam with a current profile given by a chirped sinusoid, which is generated through the interaction with a conventional broadband laser. The possibility to produce phase-locked attosecond pulses with independently tunable properties in the extreme-ultraviolet spectral region has the potential to significantly advance studies of charge dynamics in molecules of biological interests.