Optical hole burning by superhyperfine interactions in CaF(2):Pr(3+)

Optical hole burning has been observed in the 5941-A transition of Pr(3+) in a charge-compensated tetragonal site of CaF(2) . The Pr(3+) ground state is doubly degenerate and shows a large first-order hyperfine splitting, which is clearly resolved because of the very narrow inhomogeneous linewidth of 650 MHz. The hole burning involves a new mechanism, in which optically induced spin flips of neighboring nuclei (here (19)F) shift the optical transition frequency outside its homogeneous linewidth. This mechanism was confirmed by optical rf double resonance.