Abstract

Er,Yb:Glass is a unique laser gain media. Er,Yb:Glass is used for the direct generation of eyesafe 1.54 µm laser radiation. Er³⁺, when doped into a phosphate glass matrix, lasses from the ⁴I_11/2 metastable energy level to the ⁴I_15/2 ground level, utilizing a three level laseing scheme. To achieve inversion, more than half of the Er³⁺ ions must be in the metastable energy level. To obtain reasonable pumping energies, the Er³⁺ dopant concentration is usually quite low in comparison to other rare earth doped solid state lasers. As the concentration of Er³* is low and the absorption cross-section of Er³⁺ in glass is also quite low, it is very difficult to directly pump any of the Er³⁺ absorption lines. Fortunately, the transfer efficiency of energy from the ²F_5/2 level of Yb³⁺ to the ⁴I_11/2 energy level of Er³⁺ is nearly unity. Although the absorption cross-section of Yb³⁺ is similar to Er³⁺, the doping concentration of Yb³⁺ is usually more than several orders of magnitude greater than Er³⁺. The addition of Yb³⁺ to the glass matrix has a minimal effect upon the absorption at the lasing wavelength. The combination of long fluorescent lifetime and broad spectral absorption make Er,Yb:Glass an ideal media for laser diode pumping. The largest challenge to a Laser Engineer is the low thermal conductivity of the glass matrix.

© 1996 IEEE