T. Willemsen
S. Schlichting
M. Gyamfi
M. Jupé
H. Ehlers
U. Morgner
D. Ristau

Improved LIDT values for dielectric dispersive compensating mirrors applying ternary composites

SPIE Proceedings Vol. 10014: Laser-Induced Damage in Optical Materials
Type: Zeitschriftenaufsatz (non-reviewed)
The present contribution is addressed to an improved method to fabricate dielectric dispersive compensating mirrors (CMs) with an increased laser induced damage threshold (LIDT). Layers affected by high electric field intensities are exchanged by ternary composites with higher silica content according to the refractive index steps down (RISED) concept. Taking advantage of a novel in-situ phase monitor system, it is possible to control such sensitive layers more precisely. The study is initiated by a design synthesis, to achieve optimum reflection and GDD values. Afterwards the two most suitable designs are manufactured applying an Ion Beam Sputtering (IBS) process. Both designs have similar target specifications whereby one design is using ternary composites and the other one is distinguished by a conventional high low stack. The first layers of the stack are switched applying in-situ broad band monitoring in conjunction with a forward re-optimization algorithm, which also manipulates the layers remaining for deposition at each switching event. To accomplish the demanded GDD-spectra, the last layers are controlled by a novel in-situ white light interferometer operating in the infrared spectral range. Finally the CMs are measured in a 10.000 on1 procedure according to ISO 21254 applying pulses with a duration of 130 fs at a central wavelength of 775 nm to determine the laser induced damage threshold.