Investigation of the efficiency of luminescence optical filters made of activated quartz glass in neodymium laser applications
A study was made of the efficiency of a luminescence optical filter made of glass activated with divalent europium ions. This filter was used in a neodymium glass laser. An improved variant was developed for calculating the filter efficiency, which made it possible to determine the filter-induced relative change in the threshold pump power Eth and in the energy of the output radiation from the spectral characteristics of the filter–active medium system and from the excitation conditions. A satisfactory agreement was achieved between calculated and measured values of these quantities. The use of such a filter in neodymium lasers containing GLS glasses of types 21, 22, 23, and 24 and KGSS7 glass reduced Eth sometimes by a factor of 1.5–2, which made it possible to enhance the laser efficiency by a factor of 1.7 (to 2.5%). In an ideal case of total transfer of the energy absorbed by the filter to the active element the laser efficiency could rise to 4%.