Calculations of the absorption of pump radiation in a neodymium glass active element

A model that takes into account multiple transmission of pump radiation through the active element and flashlamp followed by reemission is used to calculate the absorption of pump radiation in active elements made of various grades of neodymium phosphate and silicate glasses. An analysis is made of a practical variant of a laser illumination enclosure with a diffusely reflecting coating containing a straight tubular lamp and a cylindrical active element. Calculations are made of the contribution of the various bands and of the background absorption by the activator to the total absorption in the active element when the dimensions of the element and the neodymium concentration are varied widely. It is shown that when the neodymium concentration is increased, the absorption of exciting radiation in the active element in the 0.4–0.95 μm spectral range may reach 0.6–0.8, the contribution of the background component being 20%. This calculation technique can also be applied to glasses with several activators.