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 E_th 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 E_th 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%.