Preparation and spectral analysis of 4.3%Dy:YCa4O(BO3)3 and 5%Dy,1.25%Tb:YCa4O(BO3)3 crystals for potential use in solid state yellow lasers

Abstract

Dy:YCa₄O(BO₃)₃ (Dy:YCOB) and Dy,Tb:YCa₄O(BO₃)₃ (Dy,Tb:YCOB) single crystals with different doping ratios were grown through the Bridgman technique, and the spectroscopic properties of the crystals were investigated. The crystals were designed as a laser gain medium to generate a tunable yellow laser pumped by commercially available ∼450 nm blue laser diodes (LD). For the 5%Dy,1.25%Tb:YCOB crystal, the segregation coefficients K_eff of Dy³⁺ and Tb³⁺ ions were calculated to be 0.924 and 0.871. The phonon energy of the Dy,Tb:YCOB crystal was 935 cm⁻¹. For the pump source of a 453 nm diode laser, the absorption cross-sections σ_abs of 4.3%Dy:YCOB and 5%Dy,1.25%Tb:YCOB were 0.60 × 10⁻²¹ cm² and 0.84 × 10⁻²¹ cm², respectively. The emission cross-sections σ_em of 4.3%Dy:YCOB and 5%Dy,1.25%Tb:YCOB were 2.56 × 10⁻²¹ cm² and 5.34 × 10⁻²¹ cm², and the FWHMs of 4.3%Dy:YCOB and 5%Dy,1.25%Tb:YCOB were 8.9 nm and 13.4 nm for an emission wavelength of 584 nm. The doping trace amounts of Tb³⁺ ions will improve the yellow laser output from Dy³⁺ ions and effectively enhance the emission cross-section of yellow light. The fluorescence lifetimes were fitted to 631 μs and 802 μs for the 4.3%Dy:YCOB and 5%Dy,1.25%Tb:YCOB single crystals. These results demonstrate that the 5%Dy,1.25%Tb:YCOB crystal is a potential laser crystal with a high probability to generate a tunable yellow laser.