Temperature dependent fluorescence properties and mid-infrared random lasing emission in Ho3+ and Tm3+ co-doped lead lanthanum zirconate titanate ceramics

Rare-earth ions doped fluorescence materials are attractive for numerous applications owing to the significant difference in their energy level distributions. In particular, they are commonly used in different lasers to cover different spectral regions. Consequently, laser materials with excellent properties have been introduced to improve the lasing properties of such systems. Among them, lead lanthanum zirconate titanate (PLZT) ceramics have been recently identified as promising candidates considering their excellent thermal and electrical resistance, wide broadband, and high electrooptical coefficient properties. To date, significant efforts have been devoted to enhancing the lasing performance of these materials. This includes rare-earth doping of the PLZT ceramics, specifically Tm³⁺ and Ho³⁺ ions, which have produced promising results. However, better design of lasing systems based on these materials requires a thorough understanding of the effects of temperature and ion concentration on the properties of Tm³⁺ and Ho³⁺ co-doped PLZT ceramics, which have not been fully explored in literature.

To this note, Dr. Long Xu from Southwest University, in collaboration with Dr. Caixia Xu from Chongqing Normal University, investigated the up-conversion and photoluminescence performance of Tm³⁺ and Ho³⁺ co-doped lead lanthanum zirconate titanate ceramics under different temperature conditions. Also, they explored in detail the spectrum transformation of the PLZT materials and its implications on the properties and performance in the mid-infrared lasers. The aim was to lay the foundation for the analysis of thermal stability and lasing mode competition in lasing systems. Their work is currently published in the journal, Ceramics International.

In their approach, a semiconductor laser centered at 785 nm, focused with a lens system, was used as the pumping source during the experiments. The temperature-dependent up-conversion emission peaks centered at 553 nm and 696 nm and mid-infrared photoluminescence at 2.0 µm were studied. The energy transfer between Tm³⁺ and Ho³⁺ ions was evaluated based on the suppression and enhancement of the emission peaks when doped with different concentrations of Ho³⁺ ions. Additionally, multiple narrower emission peaks in the range of 1.7 – 2.1 µm were used to achieve desirable random lasing emissions. Finally, the random lasing emission was compared to other materials to validate its properties and performance in the mid-infrared region.

The authors observed that the Ho³⁺ and Tm³⁺ co-doped PLZT ceramics materials exhibited good random lasing actions and remarkably improved fluorescence performance compared to other materials. For instance, two-photon up-conversion processes reportedly occurred at 553 nm and 696 nm at slopes of 1.75 and 1.83 for Ho³⁺ and Tm³⁺ co-doped ceramics, respectively. The multimode random lasing emission peaks were observed at 1.95 µm with a full width at maximum half of 5nm. Moreover, the reported ultrawide broadband photoluminescence spectrum proved advantageous for designing an improved Q-switch mid-infrared pulse laser. Furthermore, it was worth noting that a combination of the quadric electro-optical coefficient, pyroelectric, and photochromic effects of the PLZT materials could also lead to enhanced spectrum transformation.

In summary, the study investigated the temperature-dependent fluorescence performance and random lasing actions of Tm³⁺ and Ho³⁺ co-doped lead lanthanum zirconate titanate ceramics. The materials exhibited good fluorescence performance and multimode random lasing emission peaks that are desirable for developing mid-infrared lasers in ceramic materials. In a statement to Advances in Engineering, the authors pointed out that the results provided valuable insights that would advance the design and development of modulable lasers and optoelectrical devices.