Multi-wavelength growth of nanosecond laser-induced surface damage on fused silica gratings

Abstract

The nanosecond laser-induced damage growth phenomenon on the exit surface of fused silica grating is investigated at 1064 nm and 355 nm separately and also simultaneously. Experiments are first carried out on damage sites on a plane fused silica sample showing two different morphologies, and a damage type is selected for ensuring the repeatability of the subsequent tests. Comparing the mono-wavelength growth results on a grating and a plane fused silica sample, the periodic surface structure is found to be an aggravating factor for damage growth. This is highly supported by calculations of the enhancement of the optical electric field intensity thanks to Finite-Difference Time-Domain simulations. Finally, the mono-wavelength results enable us to quantify a coupling occurring in the multi-wavelength configuration, which could originate from the heating of the plasma (more likely produced in the ultraviolet) preferentially by the infrared pulse. This study provides interesting results about the involvement of the surface topography in damage growth, and paves the way towards the comprehension of this phenomenon at high-energy nanosecond laser facilities where fused silica gratings are simultaneously irradiated at several wavelengths.

Molecular changes associated with spontaneous phenotypic variation of Paenibacillus polymyxa, a commonly used biocontrol agent, and temperature-dependent control of variation

“…One of the significant findings is that growth temperature is an important factor determining the degree of phenotypic variation. Though phenotypic variation helps bacteria to develop resistance for surviving under harsh environments 52 , this variation makes the bacteria less desirable as a BCA. This problem can be overcome by altering the growth temperature during mass production.…”

Dynamic behavior modeling of laser-induced damage initiated by surface defects on KDP crystals under nanosecond laser irradiation

“…Firstly, the Maxwell equations are used as governing equation to solve the electromagnetic wave propagation characteristics during the laser action 15,26 . Due to the fact that the surface defect of KDP crystal in practical engineering is far smaller than the spot size of internal optical path in large laser system, we assume that the incident light is a harmonic plane electromagnetic wave and the equations can be simplified to the Helmholtz equation, as Eq.…”

“…The main mechanisms of laser-induced damage of femtosecond pulse lasers and nanosecond pulse lasers are intrinsic ionization and defect-based heat absorption, respectively [14][15][16][17] . Because the duration of nanosecond laser damage is longer, multiple physical mechanisms like light modulation, heat absorption, fluid flow, etc.…”

Model Development for Nanosecond Laser-Induced Damage Caused by Manufacturing-Induced Defects on Potassium Dihydrogen Phosphate Crystals

“…Nevertheless, it is found that surface structures such as pits, scratches, cracks, etc., are prone to induce laser damage in KDP crystals. 15 − 17 Because of the poor physical properties of KDP materials, like soft and brittle characteristics, temperature sensitivity, high water deliquescence, etc., it is inevitable to generate defects on the surface of the crystal during single-point diamond turning (SPDT) processes. 18 , 19 Nowadays, in the course of the development of KDP crystals with excellent quality and power-handling capability, the problem of laser-induced damage has shifted from the bulk to the surface.…”