Fig. 1. Schematic diagram of the XPAL configuration.

Fig. 2. Four-level system of XPAL.

Fig. 3. Flow diagram of iterative operation.

Fig. 4. Temperature and output laser power as functions of time in an XPAL under single long-time pulse pumping.

Fig. 5. Schematic diagram of the temperature distribution in the cell after the pump light is turned on for 8 ms.

Fig. 6. (a) Relationship between the output laser power and time under different initial temperature conditions; (b) peak optical–optical efficiency of laser at different initial temperatures.

Fig. 7. Power and temperature as functions of time in a multi-pulse XPAL with a rectangular shape pump light. (a) Turn on the pump light again when the temperature rise drops to $1/3$ of its maximum; (b) turn on the pump light again when the temperature rise drops to $1/2.5$ of its maximum; (c) turn on the pump light again when the temperature rise drops to $1/2$ of its maximum.

Fig. 8. Graphical representation of the data in Table 2.

Fig. 9. Power and temperature as functions of time in a multi-pulse XPAL with different initial temperatures. All the pump light is turned on again when the temperature rise drops to $1/2$ of its maximum. (a) $T_{0}=410$  K; (b) $T_{0}=420$  K; (c) $T_{0}=430$  K; (d) $T_{0}=440$  K.

Fig. 10. Graphical representation of the data in Table 3.

Table 1. Parameters in the simulation.

Table 2. Data for the multi-pulse XPAL at $T_{0}=410$  K in Figure 7.

Table 3. Data for the multi-pulse XPAL with different $T_{0}$ in Figure 9.