| Abstract [eng] |
The purpose of this work was to investigate and minimize the influence of electric field distribution for high dispersion chirped mirror laser–induced damage threshold (LIDT). In this work theory of multilayer optical coating structure and parameter calculations, as well as optimization algorithms, coating breakdown models and dispersive coating structure was described. Additionally, pervious achievements and scientific publications results in the area of electric field intensity optimization of dielectric coatings and chirped mirror optical resistance are summarized. In experimental section of the work design procedure and main parameters of two Gires Tournois interferometer coatings as well as a couple of chirped mirrors are described. Coatings of tantalum pentoxide (Ta2O5) and silicon dioxide (SiO2) had several electric field intensity maxima of different amplitude. Multilayers were sputtered with IBS technology and their laser induced damage threshold (LIDT) was tested by 1-on-1 and 1000-on-1 methods with 180 fs duration pulses. LIDT measurements of GTI samples with different angles of incidence provided data for LIDT dependency on electric field intensity, and LIDT measurements of standard and electric field optimized chirped mirrors proved the fact that LIDT may be improved by electric field optimization. Optimization strategy for electric field distribution was determined from morphological and structural analysis of damage sites with optical microscope, contact profilometer and scanning electron microscope. This strategy included reallocation of electric field peaks from high refractive index material layers to low refractive index layers by minimizing electric field in high refractive index layers only. LIDT dependency on electric field intensity determined in this work is valid for both GTI type coatings and chirped mirrors having slightly more complex layer structure and electric field distribution. Although damage site structure of optimized electric field chirped mirror was not completely explained and may be addressed in future research. |
