title: Selective suppression of high-order harmonics within phase-matched spectral regions.
abstract: Phase matching in high-harmonic generation leads to enhancement of multiple harmonics. It is sometimes desired to control the spectral structure within the phase-matched spectral region. We propose a scheme for selective suppression of high-order harmonics within the phase-matched spectral region while weakly influencing the other harmonics. The method is based on addition of phase-mismatched segments within a phase-matched medium. We demonstrate the method numerically in two examples. First, we show that one phase-mismatched segment can significantly suppress harmonic orders 9, 15, and 21. Second, we show that two phase-mismatched segments can efficiently suppress circularly polarized harmonics with one helicity over the other when driven by a bi-circular field. The new method may be useful for various applications, including the generation of highly helical bright attosecond pulses.
authors.forename: Gavriel
authors.initials: G
authors.lastname: Lerner
authors.forename: Tzvi
authors.initials: T
authors.lastname: Diskin
authors.forename: Ofer
authors.initials: O
authors.lastname: Neufeld
authors.forename: Ofer
authors.initials: O
authors.lastname: Kfir
authors.forename: Oren
authors.initials: O
authors.lastname: Cohen