Optimization of fluxes for Yb3+:YMgB5O10 crystal growth and intense multi-wavelength emission characteristics in spectra and laser performances

Yb3+-doped YMgB5O10 (Yb:YMB) crystals with better crystalline quality were grown successfully using the optimized flux of Li2O-B2O3-LiF instead of traditional K2O3-MoO3 flux by the top-seeded solution growth method. The systematic investigation of crystal growth, structure characteristics, polarized absorption and emission spectra, fluorescence decay curve and laser properties for Yb:YMB crystal were reported for the first time. The main spectroscopic and laser parameters, such as absorption coefficients and cross-sections, energy level schema and barycenter plot, radiative and fluorescence lifetime, emission and gain cross-sections, the minimum inversion fraction, pump saturation intensity and the minimum absorbed pump intensity have been calculated and analysed in detail. The broad absorption band (FWHM, 18.4 nm, E//Z) at around 936 nm matches very well with the emission wavelength of InGaAs laser diodes. The intense spectra anisotropy and multi-wavelength emissions characteristics make it possible to realize multi-wavelength laser operation at about 1 μm. The dual-wavelength Yb:YMB laser working at 1036 and 1062 nm with maximum output power of 3.02 W and a slope efficiency of 46.9 % was achieved, which may be a potential light source for THz generation with a large frequency difference of 7.1 THz. The results reveal that Yb:YMB is a promising multi-wavelength laser crystal.