Why Does the Laser Output Power Decrease?

After the laser marking machine has been used for a period of time, the reasons for the decrease of the laser output power:

1.Whether the laser resonant cavity has changed: fine-tune the front and rear resonator lenses to make the best output spot.

2.Whether the all-trans and output diaphragm are defaced.

3.Condensation is formed on the surface of the laser bar of the laser marking machine due to the temperature difference.