This paper discusses the use of photoacoustic models to obtain the nonradiative relaxation time (τ) and characteristic diffusion time (τβ) for a sample showing visible absorption bands from fluorescent ion-doped low-silica calcium aluminosilicate glass. Two models allowing phase shift analyses, the thermal-expansion and thermal-diffusion models, are briefly reviewed. These models have limitations when the photoacoustic signal depends on both factors, in a coupling mechanism. An alternative model is proposed to take both thermal expansion and thermal diffusion into account with a single temperature solution for the heat-coupled differential equation. This model is simulated for absorbing samples near the thermally thick region. The model is applied to Eu–V codoped glass showing intermediate signal dependence from ω-1.0 to ω-3/2. The nonradiative time and characteristic diffusion time are derived with 33≪τ(ms)≪39, and τβ(ms)∼70 ms for the Eu-ion and 340≪τβ(ms)≪710 for the V-ion. Four absorption bands were analyzed (280, 350, 420, and 600 nm), which showed a signal dependence from ω-1.1 to ω-1.52. Absorption coefficients were derived from τβ in the range of 15≪β(cm-1)≪51, which agreed fairly well with spectrophotometer data for the same ions.