LMI Student Seminar: Intense laser interaction with micro bars

Michal Elkind, The School of Physics and Astronomy (Ishay Pomerantz lab), TAU

Intense laser interaction with micro bars

Abstract:

The interaction of an intense laser pulse with matter results in the emission of high-energy radiation in the form of MeV electrons and ions, and hard x-rays.

Many experiments showed that when the target surface is rough on the scale of the laser wavelength, the coupling of laser energy to high-energy particles increases. 

To understand this phenomenon I irradiated isolated wavelength scale targets in the form of micrometric Au bars. My results showed two forward-directed electron jets with a small opening angle, having a narrow energy spectrum in the MeV range, and a positive correlation between angle and energy, as well as  proton beams with energies exceeding 6 MeV. The latter result exceeds the proton energies emitted from flat foils when irradiated at the same conditions by a factor of three. 

Simulations show that following ionization electrons near the target’s edge stay in phase with the laser pulse, allowing the Lorentz force to guide them around the target’s edge. These electrons form attosecond duration bunches while interacting with the laser field over long distances in vacuum and accelerating to within a narrow momentum range. The simulations also revealed that energy transfer from diffracted laser fields to the electrons on both sides of the target, combined with the reduced surface area of the structure, results in a thicker electron sheath and higher ion acceleration gradients. 

Beyond the understanding of this basic aspect of how intense light interacts with matter, I will discuss how this new methodology can lead to the possibility of laser-ion acceleration in a cascaded manner from multiple irradiated targets, allowing manipulation of the ion spectrum by optical means.
 

Fan Cheng, Electrical engineering Department of Physical Electronics (Tal Carmon lab), TAU

Cascaded and Soft Microresonators

Abstract:

In this talk, I will present our recent experimental findings with respect to large arrays of coupled whispering-gallery resonators, and the optical-capillary interactions in a soft single droplet resonator.