Understanding the evolution of defects in high-power laser components
DOI: 10.1063/10.0002432
Understanding the evolution of defects in high-power laser components lead image
Potassium dihydrogen phosphate crystals are widely used in optical systems due to their ability to manipulate the frequencies of light. However, these crystals can incur laser-induced damage in high power systems and impact their performance. While these defects have been studied extensively, however, the mechanism of their formation is yet to be fully understood.
Li et al. observed, in real-time, how the microstructures of potassium dihydrogen phosphate crystals change when they are subject to laser irradiation under various conditions. The authors used time-resolved photoluminescence spectroscopy, which uses short laser pulses to probe the optical emissions.
They identified two defects that can interconvert under certain conditions: a phosphorus-oxygen hole center (POHC) defect, which emits at 587 nm, and potentially a phosphorus-oxygen electric center (POEC), a rarely-studied crystal defect which emits at 635 nm.
The defects occurred with different probabilities depending on the power of the laser and the quality of the crystal. At a laser fluence of 11.5 J/cm2, the probability of a phosphorus-oxygen hole center defect in a potassium dihydrogen phosphate crystal was 85.5%, while the probability of a phosphorus-oxygen electric center was about 2.4%. Furthermore, the phosphorus-oxygen hole center defect had a longer lifetime, 0.74 ns, than the phosphorus-oxygen hole center defect, which had a lifetime of 0.04 ns.
Author Xiangcao Li said the researchers plan to continue probing the mechanisms of these defects.
“The POHC and POEC defects may result from two different mechanisms and may interconvert under certain conditions,” Li said. “We will study how these two defects interconvert in the further.”
Source: “Defects of laser-irradiated KDP crystals with different fluences studied by photoluminescence spectroscopy,” by Xiangcao Li, Bao’an Liu, Chunyan Yan, Jie Ren, Chang Liu, and Xin Ju. Matter and Radiation at Extremes (2020). The article can be accessed at https://doi.org/10.1063/1.5143289 .
