Microthermography of diode lasers: The impact of light propagation on image formation

We analyze the effect of propagating infrared thermal radiation within a diode laser on its thermal image taken by a thermocamera. A ray-tracing analysis shows that this effect substantially influences image formation on a spatial scale of 10 mu m, i.e., in the domain of microthermography. The main parameter affecting the thermal radiation spread in the semitransparent semiconductor structure is the free carrier concentration in the substrate, governing its absorption. Two applications are presented: a quantum dot laser and a quantum-well laser, where independent thermal models are developed using the finite element method (FEM). Our ray-tracing analysis verifies the FEM simulated temperature profiles by interlinking them to experimental temperature maps obtained through microthermography. This represents a versatile experimental method for extracting reliable bulk-temperature data from diode lasers on a microscopic scale

How to enhance a room-temperature operation of diode lasers and their arrays

A key problem to be solved during designing productive diode lasers and their lasing arrays is their proper thermal management enabling efficient high-power operation. Strictly speaking, the above demand leads to optimization of their structures to enhance lasing performance for high operation currents. It is well-known that deterioration of laser performance is mostly induced by excessive temperature increases within their volumes. In diode-laser arrays, additionally thermal crosstalk between array emitters should be taken into account. In the present paper, physics of heat-flux generation within the laser-diode volume and its extraction from it is analysed and described with the aid of our self-consistent simulation procedure. Then their thermal optimization is discussed including a proper design of a heat-flux generation within the laser volume, enhancement of its transport towards a laser heat-sink and, additionally in laser arrays, reduction of a thermal crosstalk between individual array emitters. The analysis is carried out using modern nitride edge-emitting ridge-waveguide lasers and their one-dimensional arrays as well as arsenide semiconductor disk lasers as typical examples of modern diode-laser designs. Physical processes responsible for heat-flux generation within these devices and heat-flux extraction from their volumes are analysed and an impact of some construction details on these processes is explained