Specialty Optical Fibers Handbook

7.6 THE CO-DOPED Er/Yb SYSTEM

Erbium-doped amplifiers require pumping in narrow wavelength bands

around 980 or 1480 nm. To extend pumping into the 1060- to 1100-nm band

and allow use of higher power pumps such as solid state lasers made from

crystals of Nd:YAG or Nd:YLF [77], Er may be ‘‘sensitized’’ by addition of

Yb. Pump wavelength from about 900 to 1100 nm may be absorbed by Yb

3þ

,

which can transfer the energy to erbium if the glass contains both dopants.

Absorption of Yb

3þ

peaks around 975 nm and populates the

2

F

5=2

level, as

shown in Fig. 7.15. Energy may transfer to the

4

I

11=2

band of erbium, from

which nonradiative relaxation populates the

4

I

13=2