Polarized spectroscopy and diode-pumped laser operation of disordered Yb:Ca$_3$Gd$_2$(BO$_3$)$_ 4$crystal

International audienceWe report on the growth, structure, polarized spectroscopy and efficient continuous-wave laser operation of an Yb 3+ -doped disordered calcium gadolinium borate crystal, Yb 3+ :Ca 3 Gd 2 (BO 3 ) 4 (Yb:GdCB). Yb:GdCB belongs to the orthorhombic class [sp. gr. Pnma , lattice parameters a = 7.1937(0) Å, b = 15.5311(3) Å, c = 8.6140(7) Å]. The structure disorder of this material originates from a random distribution of Ca 2+ and Gd 3+ |Yb 3+ cations over three non-equivalent lattice sites. This leads to broad and smooth (“glassy-like”) absorption and emission spectra at room and low temperatures. The stimulated-emission cross-section of Yb 3+ , σ SE is 0.42×10 −20 cm 2 at 1025.1 nm for light polarization E || c and the luminescence lifetime of the 2 F 5/2 state is 644 µs. Continuous-wave laser performance of the Yb:GdCB crystal was evaluated under high-power diode-pumping at 976 nm for three crystal orientations along the crystallographic axes. For an a -cut crystal, a maximum output power of 5.58 W was achieved at ∼1057 nm with a slope efficiency of 51.7% and a linear laser polarization ( E || c ). The demonstrated power scaling capabilities and broadband emission properties of Yb:GdCB indicate that it is promising for generation of sub-50 fs pulses from passively mode-locked lasers at ∼1 µm