Spectroscopic peculiarities of CsCaI3:Tm2+ single crystals examined through one-photon and excited state excitation spectroscopy

Highlights: • Excited state excitation spectra are presented for Tm²⁺ in CsCaI₃. • The 4f¹²5d¹ → 4f¹³ luminescence was analyzed in the function of temperature. • Activation energy of 4f¹²5d¹ → 4f¹³ luminescence quenching was estimated. • A high value of ²F_5/2 → ²F_7/2 emission cross-section was determined. The CsCaI₃ single crystals doped with Tm²⁺ were grown by Bridgman technique. Divalent thulium luminescence related to the 4f¹³-4f¹³ intra-configurational and 4f¹²5d¹-4f¹³ inter-configurational transitions were analyzed as a function of temperature. Excited state excitation spectroscopy has been applied within a wide spectral range to examine peculiarities of transitions between different 4f¹²5d¹ excited states of Tm²⁺. This two-color excitation experiment was useful to assess d-d photon-absorption processes that are relevant to observed up-conversion phenomena attributed to effective anti-Stokes green luminescence around 550 nm. Furthermore, activation energy of 4f¹²5d¹ → 4f¹³ luminescence quenching was estimated and high value of ²F_5/2 → ²F_7/2 emission cross-section was determined in CsCaI₃:Tm²⁺. Our spectroscopic study was performed to complement and verify the previous investigation in this field.