Test of high power laser diode protection circuitry designed and built by science research laboratories

Original publisher: Adelphi, MD : Army Research Laboratory, [2008] OCLC Number: (OCoLC)419364104 Subject: High power lasers. Excerpt: ... The input current, diode voltage, and temperature readings for LD41860 are shown below ( figure 8 ). As the diode degrades, the voltage increases slightly, if at all. At a constant current this indicates a slight increase in resistivity. As the optical power fell, diode temperature increased. This is a result of a larger portion of the input power being converted into heat instead of photons. LD41860 has an anomalous rise in cathode temperature at 600 hrs. Figure 8. LD41860 ( unprotected ) current, voltage, anode temperature, cathode temperature. Oddly, drops in optical power were not always coincident with faults. In order to capture the 7 transient parts of the monitored signals, we used a digital oscilloscope, triggered with the fault signal, and programmed to store the diode voltage and optical power just before and after faults. Most of the faults seemed to be spurious fluctuations in the diode voltage due to external factors, e.g., other devices being plugged into the power strip. In one particular fault, the optical power oscillated, rather than simply dropping ( figure 9 ). Figure 9. Digital fault pulse ( green ), diode voltage ( red ), and optical power ( blue ). 7 Tektronix TDS 5100. 7