To generate, measure and apply flying Electromagnetic Tori
Abstract
Aim: To generate, measure and apply flying Electromagnetic Tori, and thereby to demonstrate a new field structure for electromagnetic radiation. Abstract: In 1989 a solution to MaxwellÕs equations was found that can be pictured as a Òflying torusÓ or Òflying doughnutÓ Ð a field structure quite unlike a conventional electromagnetic wave. The proposal concerns generation, measurement, and interaction between flying tori and matter. Electromagnetic radiation is created by moving charges, and the coherent control is a technology for moving charge in a controlled manner. The current flow reversing as the relative phase between a fundamental and its second harmonic controls interfering photoelectrons. Currents produced in this way are used to generate conventional THz radiation in semiconductors or gas breakdown. However, coherent control has only been demonstrated for conventional laser beams. We will produce flying tori using vector beams -- laser beams whose polarization state is a function of the position across the beam profile. We will transform a standard Gaussian beam into a vector beam by passing it through a q-plate -- a device with a locally oriented liquid-crystal film sandwiched between conducting (but transparent in the wavelength region of operation). With a q-plate, we can create any predetermined polarization pattern across the beam profile. We will use azimuthal polarization and at each angle around the profile of the laser beam, we can select a direction for the current using the principles of coherent control. We will drive a current that is tangential to the beam at all angles and that has the same handedness. Looking at the beam as a whole, in this way we will have created a ring current and therefore we should expect a solenoidal field, just as we would expect with a current loop. In addition to its obvious fundamental significance this field structure is important because the magnetic field will be strongest at the center where both the current and electric field are zero. Such an unusual structure implies that we will be able to address magnetic transitions un-encumbered by the electric transitions that often mask them. If the current were static, then the magnetic field would be locked to the surface, but it will not be static. If we had used linear polarization, then we would have exactly the conditions for THz generation with dephasing of the electron terminating its coherent motion. Thus, also for the ring current case, the current is launched by the pulse and it is terminated by dephasing creating a flying THz torus. In this proposal we will concentrate on gases and build on the intimate connection between THz radiation and flying tori to provide us with well-developed measurement methods that can be adapted to this new situation. We also adapt the methods of strong field atomic physics to simulate and measure both low density and high density gas breakdown plasmas. For the high density case we will measure the strength of the emitter electromagnetic pulse by segmenting the beam and measuring the THz electric field locally.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 29, 2019
- Source ID
- W911NF1910211
Entities
People
- Paul Corkum
Organizations
- Army Contracting Command
- National Research Council Canada
- United States Army