A roadmap for laser optimization of Yb:Ca₃(NbGa)₅O₁₂-CNGG-type single crystal garnets

Abstract

Lasing-relevant processing and physical properties of Yb-doped Ca3(NbGa)5O12-CNGG-type disordered garnet crystals are discussed. Future directions for Yb3+ bandwidth and laser performance improvements are foreseen.

Growth of 60 mm-diameter Yb:CNGG single crystals with disordered coordination structure for high-energy laser systems

“…These obtained results were superior to the previously reported values for CNGG crystals (55.08′′). 15 Furthermore, the quality of our Yb:CNGG crystal was also comparable to large-sized garnet crystals, such as Yb:YAG (approximately 36.00′′), 27 Yb:GGG (37.00′′), 28 and Yb:GAGG (43.34′′), 29 which further confirms the importance of optimizing the temperature field during high-quality crystal growth, especially if the goal is to grow large-sized crystals.…”

“…Such a disordered coordination structure results in an abundance of Yb 3+ ions in the local coordination environment. 15,[23][24][25] XRPD analysis was employed to investigate the crystalline phase of the as-grown Yb:CNGG crystal. As depicted in Fig.…”

“…The Yb doping concentration was determined to be 1.12 at% with a segregation coefficient of 0.93, which is slightly lower than the literature value of 1.12. 15 Furthermore, the chemical formula of the bulk crystal was Yb 0.032 Ca 2.855 -Nb 1.611 Ga 3.379 O 12 , which was consistent with the refined result (Yb 0.033 Ca 2.855 Nb 1.665 Ga 3.045 O 12 ), but exhibited a slight compositional deviation from previously reported highly doped Yb:CNGG crystals (Yb 0.475 Ca 2.514 Nb 1.269 Ga 3.505 O 12 ). 14 Specifically, the content of Nb 5+ ions in our as-grown Yb: CNGG was more similar to the stoichiometric ratio than to that of the highly doped Yb:CNGG crystal.…”

“…Previous crystal growth on Yb:CNGG was typically concentrated in a size less than Φ30 mm, [12][13][14] and numerous studies were performed to examine the local coordination structure, spectral broadening mechanisms, continuous-wave lasers, and ultrafast lasers. 13,15,16 However, the crystal size of the laser gain media applied in the amplification systems of high-energy lasers typically necessitates a diameter of Φ50 mm or larger, thereby creating an urgent demand for the growth of large-sized Yb:CNGG crystals with high quality.…”

Buried Depressed-Cladding Waveguides Inscribed in Nd3+ and Yb3+ Doped CLNGG Laser Crystals by Picosecond-Laser Beam Writing

“…CaCO 3 (99.95% purity), Li 2 CO 3 (99.998 purity), Nb 2 O 5 (99.9985% purity), Ga 2 O 3 , Nd 2 O 3 , and Yb 2 O 3 (of 5N purity) were used as raw materials. Considering that Nd 3+ and Yb 3+ dopant ions replace Ca 2+ ions in the CLNGG host matrix and the values of the effective segregation coefficients (k eff ) of Nd 3+ and Yb 3+ in the CLNGG crystal are 0.55 [7] and 0.91 [17], respectively, the chemical compositions of the starting materials were established to be 1.28-at.% Nd:CLNGG and 8-at.% Yb:CLNGG, respectively. The raw materials were weighed according to the chemical equations:…”