Femtosecond laser induced damage characterization of transmission volume phase gratings

Abstract

Thermal poling induced second-order nonlinearity in femtosecond-laser-modified fused silica Appl. Phys. Lett. 93, 061115 (2008) A procedure to characterize the induced damage and the incubation effects in volume transmission gratings under femtosecond laser pulse train illumination is presented. It was also developed a formalism that explains the damage processes. Our proposal was employed on glass gratings to show the effectiveness of the method and its potential to design transmission gratings with enhanced laser induced damage threshold. This procedure is able to be extended to any transmission grating composed by chemically non-uniform material, opening up new perspectives to femtosecond laser pulse shaping. V C 2014 AIP Publishing LLC.[http://dx.doi.org/10.1063/1.4892010] Diffraction gratings are essential parts of femtosecond laser systems. They are used as dispersive elements in compressors and stretchers as well as for temporal, spatial, and spectral pulse shaping, to name a few. A laser induceddamage threshold (LIDT) characterization of gratings, i.e., the highest fluence value for which no damage is produced, is a main task to determine its applicability range. In the last years, LIDT in reflection multilayer dielectric gratings [1][2][3] and in mixed metal dielectric gratings 4 has been investigated by varying the material composition of the multilayer and by proving different grating profiles. The damage dynamics were established for a wide class of gratings, but only in the reflection geometry. No research on LIDT has been reported in the transmission geometry at the present time. In this Letter, we propose a procedure to characterize the induced damage and the incubation effects, i.e., permanent material changes produced by multiple pulse accumulation mechanisms, in volume transmission gratings when implemented in a femtosecond laser system. Besides, we develop a formalism to explain the damage processes. Our approach is tested on a photopolymerizable glass grating, showing the validity of the method to design transmission gratings with enhanced LIDT.The analysis is based on the photopolymerizable glass 5-9 because the transmission gratings on this type of material have been implemented to spatial 10 and spectral 11 pulse shaping in a femtosecond laser system. We start with the grating characterization. The grating is formed by a permanent spatial modulation of the refractive index, nðxÞ ¼ n b þ n 1 ðxÞ; within the bulk of the glass. Parameter n b is the background refractive index of the insulating binder (the glass) and

Diffraction gratings: from principles to applications in high-intensity lasers

“…Transmission VPH gratings were recorded in this material with line densities in the range of 500 to 4000 lines/mm with diffraction efficiencies at 800 nm from 96% to 98%. The LIDT was measured at 0.75 TW/cm 2 for 50 fs pulse time duration at the wavelength of 800 nm, and materials appeared unaltered after one million shots at 100 kHz repetition rate [176].…”

Damage characterization in plates using singularity of scale mode shapes

“…Damage can be interpreted as a local physical abnormality of structural material or of geometric properties. [7][8][9] Detection of damage evokes the subject of structural damage identification. In most cases, structural damage detection relies on singularity analysis of structural dynamic responses.…”