this invention relates to high power laser systems of the type which , typically , operate at up to 500 watts of average power in the high average power mode and up to 75 joules per pulse in the high energy mode , and has a lens system which is constructed of several individual pieces in order to form an integral lens holding system that maximizes the useful lens aperture . such structures of this type , generally , allow a laser / fiber user to quickly change lenses , while simultaneously maintaining optical alignment when the lens is replaced .