Determination of the thermal lensing in a broad area semiconductor laser amplifier

We propose a simple experiment that allows to measure the thermal lens created in a semiconductor laser amplifier by current pumping of the device. In this technique, we make use of the deviation of a probe beam injected at different lateral locations due to the different local refractive index gradients. The epitaxial structure of the semiconductor laser amplifier consists of AlGaAs confinement and cladding layers and an InGaAs/GaAsP double quantum well active region. The diode is 1.3 mm long and 0.4 mm wide, and has a current injection stripe of 100 mum.