The power density of a surgical laser beam: Its meaning and measurement

This paper discusses the fundamental concepts of matter, energy, power, and power density, with specific emphasis on the power density of a laser. It points out that a laser beam does not have a single, unique value of diameter within which all of its radiation is confined. Therefore, a computation of power density requires both a value of diameter, and the value of the fraction of total power which is transmitted within that diameter. Some possible means of measuring diameter, power, and power density are presented.