If the laser output window mirror is polluted, how to deal with it? And whether can wipe it with cotton swabs?

Wiping with cotton swabs will damage the output window mirror. If the front mirror is only attached a small number of particles, and the coating of the mirror has not burnt, then try to use nitrogen with a purity of 99.95% to wipe the mirror. It is do necessary to unplug the power supply before doing it.