Two-Way Coupled Thermal-Electric Simulation of a Packaged Laserdiode using Reduced Order Models

Laser diodes have many applications in different areas of research and technology and underly different working principles. Semiconductor Lasers are of most importance as they can be produced using established semiconductor manufacturing processes. A Quantum Well (QW) Laser Diode is used in this report as a powerful light source for automotive LIDAR applications. Especially the extended automotive environment conditions require a special selection of elements and materials and require specific cooling solutions. In order to evaluate a LIDAR system with its high power densities the Laser diode is simulated both electrically and thermally to find crucial elements that are electrical and thermal bottlenecks. The electrical System is analyzed with Ansys Maxwell and the thermal system with Ansys Mechanical and they are both coupled through a transient Ansys TwinBuilder simulation. Both systems comprise the same geometry, a fourfold bonded edge emitting QW Laser with connection pads in a molded package. Each of the four Lasers on a single chip can be addressed separately and is connected through a gold bond wire and a copper pin. In order to obtain 2-way coupling, electrical losses from the Maxwell simulation are coupled into a transient thermal simulation using Mechanical. The resulting temperatures are then fed back into the electrical simulation, where the conductive copper has been assumed to be temperature dependent, and thus, also the losses are temperature dependent. Each simulation in either Maxwell and Mechanical requires a separate FEM simulation to obtain the losses or the temperatures. To obtain coupling in this way would require a very long simulation time for a two-way coupling scheme. In order to speed up the process the electrical simulation is transformed into reduced order model (ROM) using a functional mockup unit comprising a sufficiently large input parameter space and a thermal LTI ROM system using all separate loss inputs. For each parameter combination in both Maxwell and Mechanical a complete FEM simulation must be run. But once the data is available, the ROMs are created and a transient simulation in TwinBuilder can be run with significant reduction of simulation time. We present simulation results of this system using only ROMs, compared to full FEM simulations and discuss the advantages and implications of using only ROMs.