The pumping laser diode

This section describes how a laser is built and the different components that are used.

The box of the diode laser is illustrated in Figure E7. The insert shows the diode itself and the rectangular by emitting surface, which is placed on a vertical stand inside the box. The box also contains a Peltier element to regulate the temperature and it is mounted on a metallic radiator to evacuate the heat that is created by the operation of the diode. An electrical current of 1 A at 2 V needs to be injected into the system so that the diode will emit 500 mW at 808 nm.

Figure E7 also shows all the electric wires needed to control the current injected into the diode and its temperature.

Temperature control is important because the wavelength of the laser varies by about 0.3 nm per °C. The heating of the junction of the diode depends on the current injected so the spectrum can easily vary by more than 1 nm. This has to be taken into account because the absorption spectrum of Nd:YAG is centred around 808 nm with a width of the order of nm so a slight change in wavelength will result in a decrease in absorption (the pump photons will no longer correspond to the pump transition) and consequently a decrease in the effective gain.