Once the pump power is actually inside the active medium, it must be converted to laser energy through whatever process the specific type of laser implements. The laser power output divided by the power into the gain medium is called the slope efficiency, η slope. Figure below shows a graph of (an arbitrary) laser output as a function of pump power input. The slope of the line in the graph is the slope efficiency. Typically, the graph is linear but in some cases it might not be. The slope efficiency can be determined by

where q defect is the quantum defect which is the energy difference between the shorter wavelength pump photons and the longer wavelength laser photons.

It is calculated by

The quantity η quantum is the quantum efficiency and is defined as the ratio of the number of photons of pump light that triggered stimulated emission divided

by the total number of input photons. This quantity is very close to 100% for most lasers but can be lower in some cases.