Value for the output power

Figure E13 shows the efficiency curve of the laser: the output power as a function of the pump power. According to the preceding formula, the curve is actually linear with a slope that depends on two parameters:

• The part of the beam passing through the output mirror compared to the total losses of the cavity: to maximise the output power, these losses must be minimised.

• The ratio of the pump wavelength to the laser wavelength. This value is specific to each laser system and for this one is equal to 0.76

The slope of this line is often called the laser efficiency and in this case is equal to 63%. By using the pump power at the lasing threshold calculated previously (see the section “Power of the pump at the lasing threshold”), the output power can be calculated as 266 mW (if the maximum pump power is equal to 500 mW). This value is fairly close to what is found experimentally.