On the steady-state population of the Tm 3F4 and Ho 5I7 manifolds in a co-doped crystalline host

The population of the Tm 3F4 and Ho 5I7 manifolds in a co-doped crystalline host has been calculated under local thermodynamic equilibrium conditions for an arbitrary excitation density. As a result, the normalized population of Ho ions vs. that of Tm ions proves to depend on the temperature and Stark sublevels but not the dopant composition. The equation for the fractional population of Tm, and Ho ions has been experimentally supported by mutilating the emission spectrum of 1%Ho:7%Tm:KYW crystal at higher pumping rates.