Vertical-cavity surface-emitting laser light-current characteristic at constant internal temperature

Two continuous-wave measurement methods for the laser P-I-characteristic at a constant internal temperature are presented (constant average cavity and constant junction (active region) temperature). The methods are used to correctly quantify the temperature dependence of threshold current and differential quantum efficiency without need for pulsed measurements. It is found that the deviations between both temperatures can be as high as 5 K in a 1390-nm InP-based buried tunnel junction vertical-cavity surface-emitting laser (BTJ-VCSEL), which is the reason for the slight sublinearity of the characteristics at constant cavity temperature.