Visualization of 1.908-$\mu$m radiation of a Tm:YLF laser using PbF$_{2}$-based ceramics doped with Ho$^{3+}$ ions

Visualization of IR radiation of a Tm:YLF laser at 1908 nm in PbF$_{2}$ ceramic samples has been investigated. Luminescence spectra of the PbF$_{2}$ samples doped with Ho$^{3+}$ exhibited bands at wavelengths of 490, 545, and 650 nm (this red band is the strongest). It is established that at, a low laser intensity, the $^{5}$I$_{5}$ and $^{5}$I$_{6}$ levels are occupied mainly due to the ion–ion energy transfer.