Temperature dependence 

The threshold current and slope efficiency depend on temperature.  This relationship is much weaker than the one observed in interband devices at similar wavelengths. Shown below are a set of power versus current curves taken from a device l = 5 µm at various temperatures. In general, the device has a maximum operation temperature which, depending on the design and wavelength, can be up to a maximum of 400K. As maximum power and sometimes slope efficiencies can both increase with decreasing temperature, it is usually advisable to cool the device with a Peltier element. Alpes Lasers sells a special Peltier cooled housings (LLH and HHL) dedicated to driving QCLs.


This power curve shows an example of 
a Fabry-Pérot laser power evolution as 
the submount temperature is increased 
from -30°C to +50°C
(click on picture to enlarge)