A. K. Oskuei
S. Baur
L. Emmert
M. Jupé
T. Willemsen
M. Steinecke
L. O. Jensen
D. Ristau
W. Rudolph

Femtosecond laser-induced modifications of frequency tripling mirrors

SPIE Proceedings Vol. 10805: Laser-Induced Damage in Optical Materials 2018: 50th Anniversary Conference
Type: Zeitschriftenaufsatz (non-reviewed)
We have studied laser induced material modication in a frequency tripling mirror (FTM) consisting of alternating hafnia and silica layers. The third-harmonic signal generated by a train of femtosecond laser pulses (791 nm, 55 fs, 110 MHz) drops over time until it reaches about 20\% of the initial value. From the observed changes in reection and transmission of the mirror a refractive index change of 0:07 was estimated, which occurs in the layer with the highest eld enhancement. This index change triggers a drop in the eld enhancement, which reduces the eciency of nonlinear optical processes. The estimated value of n allowed us to explain the 80\% reduction in conversion eciency and as well as an observed decrease in two-photon absorption.