How to (Maybe) Measure Laser Beam Quality

The objectives of this tutorial are to introduce the most important concepts and define some of the common terms involved in laser beam quality; to review briefly some of the beam quality definitions and measurement schemes employed to date; to describe some of the problems associated with various approaches and with standardization efforts for beam quality measurement; and finally to express a few of the author’s personal prejuduces on this subject. The "Maybe" in the title of this tutorial is intended to convey that measuring, or even rigorously defining, any single all-inclusive measure of laser beam quality is still a controversial an unsettled topic—and may remain so for some time.