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In recent years, the investigation of the quantum features of the radiation generated by the nondegenerate three-level cascade laser when $\gamma=\Gamma$ and $\theta=0$ has attracted interest. These studies are usually confined to the steady state case [@pra74043816; @pra77013815] or numerical solution for selected parameters [@pra72022305; @pra77062308]. However, in this article, upon using the rate of dephasing and deviation of the phase fluctuation as a probe, the evolution of the entanglement is studied when $\Omega=0$.

![\[fig1\] Plots of the time evolution of the smallest eigenvalue ($V_{s}$) of the cavity radiation for $\kappa = 0.5$, $\theta=0$, $A=10$, $\Omega=0$ and different values of $\gamma/\Gamma$.](pe2.eps){height="6.5cm"}

![\[fig2\] Plots of the time evolution of the smallest eigenvalue ($V_{s}$) of the cavity radiation for $\kappa = 0.5$, $\theta=0.25$, $A=10$, $\Omega=0$ and different values of $\gamma/\Gamma$.](pe1.eps){height="6.5cm"}

![\[fig3\] Plots of the time evolution of the smallest eigenvalue ($V_{s}$) of the cavity radiation for $\kappa = 0.5$, $\gamma=0.75\Gamma$, $A=10$, $\Omega=0$ and different values of $\theta$.](pe3.eps){height="6.5cm"}

![\[fig4\] Plots of the time evolution of the smallest eigenvalue ($V_{s}$) of the cavity radiation for $\kappa = 0.5$, $\theta=0.25$, $\gamma=0.75\Gamma$, $\Omega=0$ and different values of $A$.](pe4.eps){height="6.5cm"}

As clearly shown in Figs. \[fig1\], \[fig2\], \[fig3\] and \[fig4\], the degree of entanglement exhibits damping oscillatory 