Yb³⁺–Er³⁺–codoped phosphate glasses have been studied in the context of research for eye-safe laser source near 1540 nm, wavelength corresponding to the ⁴I_13/2→⁴I_15/2 Er³⁺– transition. Undoped and doped glasses of the composition La₂O₃–Li₂O–P₂O₅ have been synthesised. Absorption from both the ²F_7/2 Yb³⁺–ground state and the ⁴I_15/2 Er³⁺–ground state, excited state absorption ⁴I_13/2→⁴I_9/2 Er³⁺–transition, emission spectra, decay time measurements and Raman scattering have been investigated by using laser spectroscopic techniques. The Judd-Ofelt intensity parameters Ω_t (t = 2, 4, 6) for Er³⁺ have been calculated in order to determine the radiative lifetimes, the branching ratios of the transitions and the line strength of the excited state absorption ⁴I_13/2→⁴I_9/2. A thermal conductivity measurement has also been realised. In this paper, the Mayn spectroscopic properties of Yb³⁺–Er³⁺–codoped LaLiP₄O₁₂ will be discussed and compared with other Yb³⁺–Er³⁺–codoped phosphate glasses.