Two-photon, three-photon, and four-photon near-infrared quantum cutting luminescence of an Er³⁺ activator in tellurium glass phosphor.

Multiphoton near-IR downconversion quantum cutting luminescence of Er³⁺-ion-doped tellurium glass is studied. We find that the excitation spectra of 1532.0 nm IR light and 550.0 nm visible light are very similar in wave shape and peak wavelength. When the concentration of Er³⁺ ions is increased from 0.5% to 3.2%, we observe that both the IR luminescence and excitation intensity of the samples are increased by a factor of 1.80-5.49, with a concomitant decrease in both visible luminescence and excitation intensity by a factor of 0.87-1.91. Therefore, we conclude that the present phenomenon is a multiphoton near-IR quantum cutting luminescence phenomenon. We also find that the near-IR quantum cutting efficiency up-limits of the I_9/24, F_9/24, S_3/24, and H_11/22 states are respectively 157%, 138%, 193%, and 192% for Er³⁺(3.2%):tellurium glass and 175%, 154%, 233%, and 233% for Er³⁺(5.0%):tellurium glass.