Hi Axia,
For laser use the M3 / M5 commands are not really suitable because of their inherent delay. To resolve this issue the commands M11Px / M10Px (for Mach3) and M62Px / M63Px (for Mach4) were created to synchronize the Output# switching ON / OFF in time with the commencement of axis movement.
There is a little more explanation here;
http://hobbycncart.com/publ/cikkek/mach3_temaju_cikkek/switching_a_laser_under_mach_control/8-1-0-29Tweakie.