Isolated Circularly Polarized Attosecond Pulses

Two techniques for the efficient production of circularly polarized high harmonics have been demonstrated in the Kapteyn-Murnane group at JILA, leading to the generation and reconstruction of some of the most complex coherent light fields ever produced. Our theoretical analysis of these experiments has further given rise to the proposal of schemes for the production of isolated attosecond pulses of pure circular polarization (see Figure). In a set-up with two noncollinear, counter-rotating circularly polarized pulses the isolation can be either achieved by restricting the driver pulse duration to a few cycles or by temporally delaying the two crossed driver pulses. The isolation of an attosecond pulse with full control over the polarization state has been recently demonstrated in the experiment by our collaborators - in collaboration with M. Murnane and H. Kapteyn (JILA), L. Plaja and I. Sola (Universidad Salamanca, Spain) and M.-C. Chen (National Taiwan University).

P.-C. Huang et al., Nat. Photon. 12, 349 (2018)
C. Hernandez-Garcia et al., Phys. Rev. A 93, 043855 (2016)
C. Chen et al., Science Adv. 2, E1501333 (2016)
T. Fan et al., Proc. Nat. Acad. Sci. 112, 14206 (2015)
D.D. Hickstein et al., Nat. Photon. 9, 743 (2015)

JILA research highlights: A Collaborative Mastery of X-Rays

Towards Zeptosecond X-ray Waveforms

The Kapteyn-Murnane group at JILA has demonstrated the generation of bright coherent keV X-rays from a table-top mid-infrared laser source using the process of high harmonic generation. In this process the energy of more than 5000 mid-infrared photons is converted into the energy of one X-ray photon. We have shown theoretically that the temporal structure of these high harmonic pulses differs from those generated with near-infrared pulses. In particular, we have found that, although the total width of the X-ray bursts spans femtoseconds, the pulse exhibits a sub-attosecond (1 as = 10-18 s) structure due to the interference of high harmonic emission from multiple rescatterings of the electron wave packet with the ion - in collaboration with L. Plaja (Universidad Salamanca, Spain) and M. Murnane and H. Kapteyn (JILA).

C. Hernandez-Garcia et al., Phys. Rev. Lett. 111, 033002 (2013)
T. Popmintchev et al., Science 91, 1287 (2012)

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JILA research highlights: X-ray Visionaries, Life in the Fast Lane