| Abstract [eng] |
Since the beginning of laser era, the performance of optical components in any laser system was always determined by their threshold of resistance to radiation. Increasing the laser-induced damage threshold of optical components requires detailed understanding of the principles or mechanisms, underlying the damage in optical materials and coatings. This study focuses on cumulative and catastrophic laser induced damage in optical materials and coatings. Ultrafast spectroscopy methods allow to register spectral changes in differential absorption spectrum of the sample, which could then help to identify particles or states that are generated in the process of damage formation. For this application, a classic pump-probe experiment is adjusted to be performed on solid materials and to focus on the damage formation dynamics we usually see visually. Results conclude that monitoring of changes in differential absorption spectrum is a capable way of determining the laser induced damage threshold of a sample with great repeatability. In order to register damage earlier than a standard visual detection of light scattering from the damaged surface would, one must register probe beam reflected from the front surface of the sample. Formation of exciton can be seen in induced absorption spectrum at 𝜏 = 1𝑝𝑠 delay time before, during and after the damage occurs. Despite that, measurements’ accuracy just wasn’t sufficient to distinguish spectral accumulation of the signal that would allow to anticipate precise moment of damage occurrence. Moreover, laser induced damage thresholds of nanostructured dielectric coatings were measured and compared between different coating angles. |
