Why is laser amplification research important

Gain and lasing without inversion in mercury at 253.7 nm and 185 nm

Project
Subject area optics, quantum optics, physics of atoms, molecules and plasmas
Funding Funding from 2012 to 2016
German Research Foundation (DFG) - project number 210427195
The construction of continuously working lasers in the UV and VUV range is a major challenge because of the shorter lifetimes of the laser levels involved in the process. One way out is the method of "lasing without inversion", ie generating a laser process without population inversion. This term hides a coherent mechanism in which the atoms are pumped into a coherent state in such a way that the absorption of the laser wavelength is prevented. A small number of atoms in the upper laser state is enough to operate the laser above the threshold. Previous experiments on this method were limited to 3-level systems in Λ or V configuration and really demonstrated the functional principle without to use the potential of the method, ie no shorter-wave radiation was generated than had to be used in the experiment to establish the coherence. We propose to use four atomic levels in mercury to generate UV radiation for the first time by “lasing without inversion” at 253.7 nm and 185 nm. By expanding to the 4-level system and a clever geometric selection of the directions of propagation of the lasers, the Doppler effect can also be compensated, so that the use of a simple mercury cell is possible. In addition, this ensures that laser amplification only takes place in a well-defined direction. This is important because it enables coherent radiation to be generated even if no suitable mirror materials exist for the short-wave radiation. A transfer to other atomic systems with even shorter-wave transitions is possible.
DFG procedure