טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentMoshe Shuker
SubjectDecay Processes in EIT Medium
DepartmentDepartment of Physics
Supervisors Professor Emeritus Ron Amiram
Full Professor Nir Davidson
Full Thesis textFull thesis text - English Version


Abstract

Electromagnetically induced transparency (EIT) occurs when two nearly resonant light fields excite two ground-state sub-levels to a single upper level. The simultaneous interaction of the two light fields traps the atom in a coherent super-position of the ground-state and prevents its excitation to the upper level. This allows the light beam to pass the medium, which otherwise would have been completely opaque - i.e. transparency induced by an electromagnetic field. A striking feature of this phenomenon is that the induced transparency is extremely sensitive to the frequency difference of the light fields, resulting in ultra-narrow spectroscopic features (EIT lines) along with strong dispersion (as dictated from the Kramers-Kronig relations). The combination of these two properties, and the strong light-matter interaction, made the EIT medium attractive for several light-matter manipulation techniques: advanced metrology applications can be implemented (frequency standards, magnetometers), strong non-linear interaction can be achieved even at low light levels, light pulses can be slowed to low group velocities, and light can be coherently converted to atomic excitations and vice-versa (storage of light). In this thesis we study the physical processes that govern the spectral width of EIT resonances in room temperature vapor. Inherent and effective decay mechanisms of the ground state coherence usually pose the lower limit for the possible EIT line-width. Initially, we carefully study the depopulation and decohernece rates within the ground-state sub-levels of 87Rb vapor, and find the dominant physical processes that govern the decay of the coherence. After that we focus our efforts on evaluating the EIT line broadening caused by the thermal motion of the atoms in the vapor, and show that the thermal velocity, as well as the velocity-changing collisions, determines the overall line-width. Finally we study the effect of atomic diffusion by means of storage of light. We find that careful control of the optical phases may reduce the deteriorating effects of diffusion.