Net Optical Gain Coefficients of Cu⁺ and Tm³⁺ Single-Doped and Co-Doped Germanate Glasses

Broadband tunable solid-state lasers continue to present challenges to scientists today. The gain medium is significant for realizing broadband tunable solid-state lasers. In this investigation, the optical gain performance for Tm³⁺ and Cu⁺ single-doped and co-doped germanate glasses with broadband emissions was studied via an amplified spontaneous emission (ASE) technique. It was found that the net optical gain coefficients (NOGCs) of Tm³⁺ single-doped glass were larger than those for Cu⁺ single-doped glass. When Tm³⁺ was introduced, the emission broadband width of Cu⁺-doped glass was effectively extended. Moreover, it was found that for the co-doped glass the NOGCs at the wavelengths for Tm³⁺ and Cu⁺ emissions were larger than those of Tm³⁺ and Cu⁺ single-doped glasses at the same wavelengths. In addition, the NOGC values of Tm³⁺ and Cu⁺ co-doped germanate glasses were of the same order of magnitude, and were maintained in a stable range at different wavelengths. These results indicate that the Tm³⁺ and Cu⁺ co-doped glasses studied may be a good candidate medium for broadband tunable solid-state lasers.