In Er:YAG, Er:YSGG and Er:YLF lasers the most important are the three lowest energy levels of Er3+ ion. Transitions
between these levels decide about wavelength of generated laser radiation. In Er:YAG laser these levels are: 4I15/2
(energy: 280 cm-1), 4I13/2 (6710 cm-1), 4I11/2 (10330 cm-1) . Er:YAG has many absorption lines mainly in visual and
near infrared wavelength spectrum. This laser may generate optical radiation at two wavelengths: 1,6 μm and 2,94μm.
For the first one Er:YAG works as a three level quantum system and the for the second one it works as a four level
quantum system. In this case the top laser level is 4I11/2 and the down laser level is 4I13/2. Both the wavelength generated
and the work mode may be selected by dopant concentration.
In lasers such as Er:YAG an analysis of transitions between levels during optical radiation absorption and generation the
Boltzman distribution of energy levels occupation and thermalization effects must be taken into consideration .
Authors have developed computer software, which allows analysing transitions dynamics, laser output power/energy and
rod's temperature increase (during pulse generation) which depends on: pump properties, initial temperature, and dopant concentration.
Analysis may be carried on for monopulse generation as well as for pulse generation. This software allows simplifying
Er:YAG laser application designing.