Broad-band emission from chromium doped germanium garnets

By varying the composition of a series of germanium garnets, it is possible to change the lattice constant of the structure over a wide range, and thus the crystal field. Three Cr-doped germanium garnets (Ca
3
Al
2
Ge
3
O
12
, CaY
2
Mg
2
Ge
3
O
12
, and MgY
2
Mg
2
Ge
3
O
12
) have been grown as single crystals. Spectroscopic results show that in these garnets the broad-band emission at room temperature is so strong that it totally dominates the
R
-line emission. The spectral region covered by emission from these crystals is from 700 nm to more than 1 μm. The room-temperature lifetimes range from 50 to 290μs.