Growth, spectroscopy and 2 μm laser operation of monoclinic Tm3+:ZnWO4 crystal

• Published in: Optical materials 2024-11, Vol.157, p.116039, Article 116039
• Main Authors: Zin Elabedine, Ghassen, Subbotin, Kirill, Loiko, Pavel, Pan, Zhongben, Eremeev, Kirill, Zimina, Yulia, Didenko, Yana, Pavlov, Sergei, Titov, Anatoly, Dunina, Elena, Fomicheva, Liudmila, Kornienko, Aleksey, Braud, Alain, Solé, Rosa Maria, Aguiló, Magdalena, Díaz, Francesc, Chen, Weidong, Volkov, Pavel, Petrov, Valentin, Mateos, Xavier
• Format: Article
• Language: English
• Subjects: Judd-ofelt theory; Laser materials; Luminescence; Optical spectroscopy; Solid-state lasers; Thulium ions
• ISSN: 0925-3467
• DOI: 10.1016/j.optmat.2024.116039

We report on the crystal growth, polarized spectroscopy, and laser operation of monoclinic Tm3+, Na+(Li+) codoped zinc monotungstate (ZnWO4) crystals. The Li+ codoping with an optimized Tm/Li ratio enables almost complete local charge compensation leading to better crystal quality, higher Tm segregation coefficient, and longer luminescence lifetime and ultimately the demonstration of laser operation. The modified Judd-Ofelt theory was employed to calculate the Tm3+ transition probabilities yielding a radiative lifetime of the 3F4 state of 2.59 ms. The corresponding intensity parameters are Ω2 = 5.194, Ω4 = 0.658, Ω6 = 0.471 [10−20 cm2] and α = 0.110 [10−4 cm]. Tm,Li:ZnWO4 features strongly polarized emission spectra extending beyond 2 μm owing to a large total Stark splitting of the ground-state, ΔE (3H6) = 644 cm−1. The stimulated-emission cross-section in this spectral range reaches 0.47 × 10−20 cm2 at 2015 nm for light polarization E || Np. The continuous-wave Tm,Li:ZnWO4 laser generated 282 mW at 1.98 μm with a slope efficiency of 14.7 %, and laser emission at 2.03 μm was also achieved. •Czochralski growth of monoclinic Tm3+, Na+(Li+) codoped zinc monotungstate (ZnWO4).•Li + codoping provides higher Tm3+ segregation and longer luminescence lifetime.•Tm,Li:ZnWO4 features strongly polarized emission spectra extending beyond 2 μm.•The stimulated-emission cross-section is 0.47 × 10−20 cm2 at 2015 nm.•First continuous-wave laser operation of Tm,Li:ZnWO4 crystal at 2 μm is demonstrated.