טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentGad Raanan
SubjectMagnetically Induced Transparency in Classical Magnetized
Plasma
DepartmentDepartment of Physics
Supervisors Professor Emeritus Amiram Ron
Dr. Amnon Fisher
Full Thesis textFull thesis text - English Version


Abstract

Magnetically induced transparency (MIT) in plasma is a classical analog to electromagnetically induced transparency (EIT) in atomic systems. Transmission of radiation through longitudinally magnetized plasma is obtained by applying an additional transverse spatial periodic magnetic field. The transverse-periodic magnetic field uncouples the right-hand electromagnetic wave from interacting with plasma electrons, rendering the plasma bandstop transparent.

Quantum EIT occurs when two radiation fields, usually a weak ’probe’ and a strong ’pump’, excite two atomic levels to a common upper level, creating coherent population trapping. This coherent superposition in the atomic system reduces absorption and changes the dispersion. EIT appears as sharp resonance, while at the same time the pulsed probe is slowed down and the group-velocity is of the order of tens of meters per second. Moreover, the probe signal can be stored and retrieved after hundreds of microseconds by switching the pump off and on, respectively. These phenomena of quantal origin are being investigated for more than two decades.

MIT in cold magnetized plasma is a result of the collective behavior of the plasma electrons. Initially, the plasma electrons immersed in the longitudinal magnetic field experience a force causing them to spiral around the magnetic field guiding centers. The probe wave cannot propagate since its energy is transferred to the electrons kinetic energy, and total absorption is observed. This is the well known cyclotron absorption of right-hand circularly polarized (RHCP) wave. An additional magnetic field of a helical wiggler, couples the probe electromagnetic (EM) field through longitudinal plasma oscillations eliminating electron cyclotron absorption. These longitudinally oscillating electrons transfer their kinetic energy back to the EM wave. This process propagates along the longitudinal magnetic field and the plasma axis until the EM wave emerges from the plasma. Electrons oscillating longitudinally and collectively cause the probe wave to propagate rendering the opaque medium transparent.

In the present work we demonstrate experimentally, for the first time, magnetically induced transparency in classical plasma. We show that opaque cold magnetized plasma becomes transparent by adding a one dimensional transverse, time-independent, spatially periodic magnetic field of a wiggler. We extended the theory and show that the MIT bandpass occurs at the plasma rather than at the cyclotron frequency, in contradiction to previous theories. Our experiments confirm this prediction and the existence of this classical analog to atomic EIT, and clear the way to slow-light, non-diffraction and storage under MIT conditions.