On 13 February 2014, the award winner was selected for the Dissertationspreis Adlershof 2013: Martin Hempel has prevailed against two other nominees and in the unanimous opinion of the jury his doctoral thesis "Defect Mechanisms in Diode Lasers under High Optical Load: The Catastrophic Optical Damage" presented best in the final decision.
Martin Hempel had already discovered his enthusiasm for researching novel semiconductor lasers as a graduate student and, as a doctoral student at MBI, investigated the ultimate performance limits of these universally applicable lasers. Here, Hempel dealt in particular with the so-called Catastrophic Optical Damage (COD). This refers to the destruction of semiconductor diode lasers at high optical intensities. In this case, a volume of about 1 micron3 of the laser material is heated by absorbed laser light within 1 ns until melting at ≈1600°C. As a result, the defect (COD) spreads in the laser at a speed of around 90 km / h. Within a few μs, this destroys the entire laser whose volume is about 1000 times greater than the starting point of the defect. In his work Hempel was able to track the COD spat-temporally during its formation. This brought new insights into the physical mechanisms of the process. The close cooperation with manufacturers of semiconductor lasers now enables a targeted improvement of the components, as their weak points in high-performance operation can now be identified quickly and clearly.
