9C8 - Saturable absorption of color centers in Nd3+and Nd3+-Yb3+laser glass

By saturated absorption of color centers in glass, self -switched pulses are obtained, as in glass codoped with UO2²⁺and Nd³⁺. One of the commonly used laser glasses contains 5 wt. percent Nd2O3in a glass base consisting of 72 wt. percent SiO2, 11 K2O, 8 Na2O, 1 Li2O, 5 BaO, 2 Al2O and 1 Sb2O3. The antimony is added for bubble removal in making the glass and to prevent solarization. If the antimony is left out, color centers are produced by ultraviolet light whose wavelength is shorter than 300 nm. Three broad absorption bands result, which are stable at room temperature. They are centered at 310 nm, 450 nm, and 620 nm. The stable color centers are bleached on exposure to visible or ultraviolet light of wavelength longer than 300 nm and they are completely bleached after heating to 200°C for one hour. Additional color centers are produced with room temperature decay times short enough so that they are in the glass only while the ultraviolet from the flashlamp is present. At 300°K, the short lived color centers give a 5 percent/cm at 1 μm and are responsible for saturated absorption in the laser.