Working Thermal Stresses in AlGaAs/GaAs High-Power Laser Diode Bars Using Infrared Thermography

An interesting approach is proposed for investigating the thermal stress of AlGaAs/GaAs laser diode bars using infrared thermography. We obtained horizontal and perpendicular profiles of the working thermal stress through the active region in one emitter (emitter 5) at operating currents 0.5 and 1.0 A. The thermal stress at the center of emitter 5 is found to quickly rise to values 2.1 and 3.4 MPa under the operating currents 0.5 and 1.0 A. The thermal stress gradient in the epitaxial layer is also larger than that in the substrate. In addition, if emitter 5 operates individually, a thermal stress spike at a current of about 0.2 A appears, with a sharper rise in slope between 0.1 and 0.2 A than between 0.2 and 1.0 A. Furthermore, with regard to the properties of transient working thermal stress, the profile of the thermal crosstalk between emitters was obtained at different operating currents.