Rami Arieli: "The Laser Adventure" Chapter 5 Section 3, page 5
Gain and Output Power of CW Laser

For the same laser, increasing pumping cause increase in small signal gain, but the saturation gain is unaffected, and remain equal to threshold gain (GA)th.
The output power of the laser will increase since both the small signal gain and the population inversion increases.

Increasing pumping cause the holes inside the gain curve to be filled more quickly, since the number of excited atoms is larger.

Figure 5.9 shows the influence of the input power in CW laser on the following factors:

  1. Active medium gain.
  2. Loop gain.
  3. Output power of the laser.
Figure 5.9: Gain and Output Power as a function of time for CW laser.
At time t1 the excitation mechanism is activated. As a result, the active medium gain and loop gain increase.

At time t2 the active medium gain is equal to the threshold gain, and the loop gain is equal to 1. Lasing starts, and output power of the laser start to increase.

At time t3 the input power reaches its steady state (constant input power). The active medium gain is a little above threshold, and the loop gain is a little above “1”.
Output power from the laser continues to rise, until t4, when it reaches its steady state value. Then the active medium gain is equal to the threshold gain, and the loop gain is equal to “1”.