Polarization shaping of high-order harmonics in laser-aligned molecules

Abstract

The present work reports on the generation of short-pulse coherent extreme ultraviolet radiation of controlled polarization. The proposed strategy is based on high-order harmonics generated in pre-aligned molecules. Field-free molecular alignment produced by a short linearly-polarized infrared laser pulse is used to break the isotropy of a gas medium. Driving the aligned molecules by a circularly-polarized infrared pulse allows to transfer the anisotropy of the medium to the polarization of the generated harmonic light. The ellipticity of the latter is controlled by adjusting the angular distribution of the molecules at the time they interact with the driving pulse. Extreme ultraviolet radiation produced with high degree of ellipticity (close to circular) is demonstrated.

Evidence of depolarization and ellipticity of high harmonics driven by ultrashort bichromatic circularly polarized fields

“…Remarkable progress has been achieved recently to provide tunable polarization of X-ray free-electron lasers, and to characterize the polarization state by combining different techniques 8 , 9 . Ultrashort table-top high-harmonic generation (HHG) sources have long been confined to low ellipticities 10 – 15 until recently when various schemes were shown to produce a high degree of circularity 4 , 16 – 21 . A particular scheme proposed long ago 22 , 23 stands out as a good candidate to produce intense circularly-polarized ultrashort XUV pulses and has triggered a lot of theoretical 24 – 30 and experimental work 17 , 18 , 31 , 32 .…”

Quantum path interferences in high-order harmonic generation from aligned diatomic molecules

“…This is because the properties of the emitted harmonics are strongly connected, via the electron recollision process, with the molecular structure. The majority of the studies in this research direction have been performed using aligned linear molecules in proof of principle experiments [11][12][13][14][15][16][17][18][19][20]. Such investigations are typically performed using field-free molecular alignment approaches based on pump-probe-type configurations (see for example ref.…”

Helicity-Selective Enhancement and Polarization Control of Attosecond High Harmonic Waveforms Driven by Bichromatic Circularly Polarized Laser Fields

“…Consequently, if the spectral amplitudes are unequal (i.e., a chiral spectrum), then the individual attosecond bursts become elliptically polarized, while the harmonics retain their circular polarization [45,[48][49][50]. This rather unique spectro-temporal coupling in CPHHG has recently led to a strong interest in producing chiral CPHHG spectra [45,[48][49][50][51][52], since such spectra allow for a straightforward way to generate bright highly elliptical APTs. Moreover, the high brightness and relative simplicity of collinear, bichromatic CPHHG make it an attractive alternative to more complex methods of generating highly elliptically or circularly polarized APTs [53][54][55][56][57].…”