Sol–gel-processed hybrid silica-PDMS layers for the optics of high-power laser flux systems

Abstract

International audienceThe laser-induced damage of optical components of high-power laser systems such as the National Ignition Facility (NIF) (Murray, Proc SPIE 3492:1–10, 1998) and Laser MegaJoule (LMJ) (André, Fusion Eng Des 44:43–49, 1999) can have a significant impact on the operating costs of these laser systems since optimal shaping to carry out ignition is required. Laser-induced damage (LID) of fused silica appears on the exit surface, mostly at 3ω, and tends to grow exponentially with each laser shot. This damage affects the performance of optical components and limits their lifetime. The damage is due to thermal explosions of microdefects or microabsorbers, and these explosions emit a plasma that generates shock waves introducing cracks that increase the damage. This paper, thus proposes the deposit of an elastic layer on the exit surface to mitigate the shock waves and thereby decrease the extent of the damage volume. To this end, we have developed a mendable sol–gel-processed hybrid inorganic–organic layer. The hybrid layer is a nanocomposite made of silica and polydimethylsiloxane (PDMS). Their resultant mechanical properties can be tuned by adjusting the elastomer/silica ratio and catalysis conditions. The synthesis used to create these layers was investigated with an infrared spectrometer. The optical quality of the hybrid layers was checked by UV/visible/NIR spectrophotometry and thickness uniformity were mapped via reflectometry. Young’s modulus, Poison’s ratio, and the hardness have been measured in order to characterize the mechanical properties of these layers. The surface acoustic waves technique was used to determine Young’s modulus and Poison’s ratio of an optical layer obtained by a sol–gel process. The hardness has been measured with a homemade indenter. The results of first measurements of laser damage made with an excimer laser at 351 and 353 nm demonstrated a reduction of the laser-induced damage threshold with the PDMS/silica ratio

Aggregation-induced heterogeneities in the emission of upconverting nanoparticles at the submicron scale unfolded by hyperspectral microscopy

“…S6-ESI †). The similar emission proles show that, unlike other features such as hydrophobicity, mechanical properties and refractive index that can be tuned by changing the inorganic M x O y constituents, [62][63][64] the upconversion process is quite insensitive to the metal M used in the hybrid. This is an important point for the usage of these materials since it means that the emission properties will remain invariable; meanwhile other properties can be adjusted by modifying the hybrid's composition.…”

Surface Modification of ZrO2 Nanoparticles with TEOS to Prepare Transparent ZrO2@SiO2-PDMS Nanocomposite Films with Adjustable Refractive Indices

“…Since PDMS is a hydrophobic polymer matrix with a high molecular weight, surface modification is required for ZrO 2 NPs, which have COO − groups on the surface, to prevent the agglomeration of NPs in the PDMS matrix. ZrO 2 @SiO 2 NPs can form chemical affinity with PDMS through the formation of bonds between the surficial Si–OH groups of NPs and PDMS chains [ 53 , 54 , 55 ]. Dispersion of ZrO 2 @SiO 2 NPs in the PDMS matrix can be improved as the surfaces of the NPs are subjected to greater modification by the SiO 2 layer.…”

Non-destructive characterization of surfaces and thin coatings using a large-bandwidth interdigital transducer

“…However, for highly attenuating samples such as PDMS, 6,30 200 pm SAW displacements may not be sufficient for propagation over several centimeters and the SNR issue could become vital. For this reason, we studied an adapted chirped excitation in the same 20-125 MHz frequency range.…”

“…In other studies, Young's modulus and the residual stresses could be measured. [4][5][6]30 Several methods exist to determine the phase velocity dispersion from the normal displacements obtained by means of an interferometer. In our case, we chose the Slant Stack transform.…”