Several questions seem to keep popping up over and over again.
All of Power Technology's systems are linearly polarized. The thickness can be changed to meet your needs. If the system you are building is intended for viewing by the human eye, 635nm will appear approximately 5 times brighter than 670nm at the same output power. Because of their apparent brightness, these systems are widely used in medical applications where only a small amount of laser radiation can be pointed into the human eye. For circular beams, the diameter is between 1mm and 4mm depending on the optics.