A high accuracy femto-/picosecond laser damage test facility dedicated to the study of optical thin films

Abstract

A laser damage test facility delivering pulses from 100 fs to 3 ps and designed to operate at 1030 nm is presented. The different details of its implementation and performances are given. The originality of this system relies the online damage detection system based on Nomarski microscopy and the use of a non-conventional energy detection method based on the utilization of a cooled CCD that offers the possibility to obtain the laser induced damage threshold (LIDT) with high accuracy. Applications of this instrument to study thin films under laser irradiation are presented. Particularly the deterministic behavior of the sub-picosecond damage is investigated in the case of fused silica and oxide films. It is demonstrated that the transition of 0-1 damage probability is very sharp and the LIDT is perfectly deterministic at few hundreds of femtoseconds. The damage process in dielectric materials being the results of electronic processes, specific information such as the material bandgap is needed for the interpretation of results and applications of scaling laws. A review of the different approaches for the estimation of the absorption gap of optical dielectric coatings is conducted and the results given by the different methods are compared and discussed. The LIDT and gap of several oxide materials are then measured with the presented instrument: Al(2)O(3), Nb(2)O(5), HfO(2), SiO(2), Ta(2)O(5), and ZrO(2). The obtained relation between the LIDT and gap at 1030 nm confirms the linear evolution of the threshold with the bandgap that exists at 800 nm, and our work expands the number of tested materials.

Electronic quantization in dielectric nanolaminates

“…Further details on the experiment can be found in Ref. [17]. For the following analysis, the respective LIDT values are normalized to the maximum of the calculated field intensity.…”

Laser damage growth with picosecond pulses

“…In the case of subpicosecond laser systems, the effect of irradiation conditions (fluence, pulse duration, wavelength, number of pulses, and environment) [1][2][3][4], design and manufacturing conditions (coating process, materials, electric-field distribution) [5,6] were thoroughly studied. Overall, it has been demonstrated that the laser damage resistance of an optic in the subpicosecond regime is both limited by its intrinsic properties (linked to its electronic structure) [7,8] and by the presence of embedded defects induced by the manufacturing process [4,9]. The densities of such embedded defects can be as high as two hundreds of defects∕cm 2 , estimated from the measurement of damage densities during rasterscan tests [10].…”

“…Laser damage experiments are carried out with the setup described in [8]. The wavelength during this experimental study is 1030 nm.…”

Laser damage measurement techniques for the femtosecond regime

“…The system is described in details in Ref. [12] and [13]. In these experiments the laser beam was focused on the entrance surface of the tested sample with an anti-reflected coating plano-convex lens.…”