Speaker
Description
Besides circular polarization, which encodes a Spin Angular Momentum (SAM), Laguerre-Gaussian beams also carry Orbital Angular Momentum (OAM), amounting to ℓℏ per photon, due to an azimuthal dependence in the electric-field phase of the form exp(iℓ𝜑) [1]. As the OAM index ℓ defines a set of orthogonal modes, OAM beams found application in high-bandwidth optical data transfer [2]; their ability to exert mechanical torque has been employed in optical spanners for manipulation of micro-particles [3], and their radial intensity dependence led to improved resolution and contrast in microscopy and imaging [4-5]. Analogous to Magnetic Circular Dichroism, the intrinsic handedness of OAM beams also found spectroscopic applications, e.g. with chiral molecules [6] and magnetic materials [7-8], benefiting from extension into EUV and soft x-ray range thanks to core-level electronic resonances, sharper focusing capabilities, and the availability of intense and ultra-short OAM pulses at large-scale facilities [9] and lab-based sources [10].
I will present some recent results on the employment of OAM light beams applied to magnetic material: resonant soft x-ray Fourier Transform Holography in transmission from thin magnetic films possibly reveals enhanced contrast arising from the light structuration in intensity and in phase. I will also present a second experiment, to be performed the next future, which explores the employ of an optical Transient-Grating setup to gate the synchrotron pulses and to generate short 10-ps soft x-ray pulses with on-demand OAM charge.
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