Reduction in fiber damage thresholds due to static fatigue
Damage mechanisms may occur during the transmission of Q-switched, Nd/YAG laser pulses through fused silica fibers. Fiber end-face characteristics, laser characteristics, and aspects of the laser-to-fiber injection typically determine dominant damage mechanisms. However, an additional damage process has been observed at internal sites where fibers were experiencing significant local stresses due to fixturing or bends in the fiber path. A transmission reduction prior to damage was typically not measurable at these sites. Damage would not always occur during initial testing, but sometimes occurred later in time at laser levels that previously had been transmitted without damage. In these cases the time at stress appeared to be more important than the number of transmitted shots prior to damage. A possible relation between internal damage thresholds at stressed sites and the total time under stress is suggested by the fact that silica fibers experience static fatigue processes. These processes involve the slow growth of local defects under tensile stress at rates that depend upon environmental conditions. Defects reaching sufficient size and having appropriate location could be sites for reduced laser-induced damage thresholds. The present work looks into the possibility that static fatigue processes can affect damage thresholds. The experiments used a laser injection and fiber routing configuration that produced significantly elevated fluences within fiber core regions under tensile stress. In order to establish initial strength and fatigue properties for these fibers, a number of samples were used to generate time-to-failure data at various stress levels. Other fiber samples were subjected to conditions that greatly accelerated fatigue processes. Internal damage thresholds were then measured in these fibers and compared to thresholds measured in fresh fibers. Conclusive comparisons were frustrated by sample-to-sample and lot-to-lot variations in fiber defects.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 10107913
- Report Number(s):
- SAND--94-2617C; CONF-9410155--1; ON: DE95004778
- Country of Publication:
- United States
- Language:
- English
Similar Records
Laser-induced damage studies on step-index multimode fibers
Laser-induced damage studies on step-index, multimode fibers