Patent ID: 7951735

Claim:
An optical gain medium comprising a bulk single phase glass comprising: (a) an optically active dopant that is at least one Yb 3+ , Er 3+ , Tm 3+ , Ho 3+ , Dy 3+ , Nd 3+ , or Pr 3+ , wherein the optically active dopant has a fluorescence lifetime of at least 0.5 ms; (b) 10-30 molar % SiO 2 ; (c) 27-50 molar % RE 2 O 3 ; and (d) the balance Al 2 O 3 ; wherein RE is at least one of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu.