Laser-induced damage of F-SiO<sub>2</sub> protected fluoride-based AR coatings on subsurface-damage-free CaF<sub>2</sub> at 193 nm

Wang, Jue; Cox, Gerald P.; D'lallo, Michael J.; VanKerkhove, Steven; Oudard, Jean Francois

doi:10.1117/12.2243783

Cited by 5 publications

(2 citation statements)

References 3 publications

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“…where Eqs. (12) and (13) are the boundary and initial conditions, respectively. C p , ρ, and k are isobarically heat capacity, density, and thermal conductivity, respectively.…”

Section: Thermo-mechanical Coupling Fea Model Of Laser Induced Damagementioning

confidence: 99%

Nanosecond laser-induced surface damage and its mechanism of CaF2 optical window at 248 nm KrF excimer laser

Dou

Hong³

et al. 2020

Sci Rep

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Calcium fluoride (CaF 2) crystals is a kind of important optical material for ultraviolet (UV) and deepultraviolet (DUV) lithography and high-power laser-related applications. However, its laser-induced damage threshold (LIDT) directly affects the laser power, so that the above-mentioned applications could be limited. Therefore, the research on the damage characteristics and laser damage resistance of caf 2 crystals is urgent. A 3D Finite-Difference Time-Domain (FDTD) method with Maxwell spinor equation is used, and the results show that the electric field intensity of rear surface is larger than that of front surface, which causes a lower threshold and is consistent with the experimental observations. And a thermo-mechanical coupled finite element model (FEM) of CaF 2 with ce 2 o 3 impurities, which are introduced by polishing process, has semiquantitatively described the damage mechanism of CaF 2 by 248 nm-excimer laser. Due to the large band gap energy (12.1 eV), high transmission at UV range, very low value of nonlinear refractive index, good optical isotropy and excellent chemical stability 1-5 , CaF 2 optical window materials have been widely used. The results of surface damage of different types of CaF 2 materials induced by different laser parameters showed that the damage behavior was closely dependent on the materials characteristics as well as laser parameters 6-13. Among the works of ultraviolet excimer laser damage of ultraviolet windows, fused silica has been reported mostly 14-24. In contrast, the reports on fluoride windows are relatively few, and most of the studies were just focused on the damage of fluoride films. Only a few reports are limited to the laser damage of single fluoride windows at 1064 nm wavelength 25 , and most of them were concerned with the damage caused by the fundamental 1064 nm laser and triple frequency 355 nm ultraviolet laser. There are few publications about the damage caused by shorter wavelength excimer laser, such as 248 nm laser. Because ultraviolet excimer lasers present favorable characteristics such as high photon energy, high coupling efficiency as well as high peak power 26-30 , they are expected to be widely used in precision laser machining and military area. This research will provide great significance in deeply understanding the interaction between ultraviolet laser and material, offer important reference in laser precision machining and laser attack-defense field, and also provide theoretical basis for the anti-laser damage ability of optical components. Based on the self-developed PLD-50 excimer laser, a set of LIDT testing system was established. The CaF 2 samples were divided into 2 groups, one group was highly polished, and the other one was roughly polished. First, the structural defects from polishing the CaF 2 crystal were characterized with fluorescence spectroscopy. Second, the samples were irradiated in a 1-on-1 mode with increasing energy density. Afterwards, the surface fragmentation and damage characteristics of CaF 2 crystals were analyzed vi...

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“…where Eqs. (12) and (13) are the boundary and initial conditions, respectively. C p , ρ, and k are isobarically heat capacity, density, and thermal conductivity, respectively.…”

Section: Thermo-mechanical Coupling Fea Model Of Laser Induced Damagementioning

confidence: 99%

Nanosecond laser-induced surface damage and its mechanism of CaF2 optical window at 248 nm KrF excimer laser

Dou

Hong³

et al. 2020

Sci Rep

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“…SSD-free CaF2 surface, obtained by uniting mechanical polishing and chemical etching, increases laser damage resistance [5]. Laser durable grade CaF2 crystal shows superior laser damage resistant in comparison to ArF laser grade CaF2 [6]. Several generations of protective coating for calcium fluoride (PCCF, and PCCFxi) further extend the lifetime of CaF2 Laser Optics [7].…”

Section: Laser and Plasma Colorationmentioning

confidence: 99%

Surface and bulk damage resistance of calcium fluoride optics assessed by x-ray induced color centers

Wang

Piche

Fanning

2023

Components and Packaging for Laser Systems IX

Self Cite

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A rhodium-emitted X-ray with a photon energy at 20 KeV was employed to irradiate CaF2 with different surface finishing. Color centers associated with the irradiation damage were determined by spectral measurements. The depth distribution of the color centers was calculated and confirmed in a wedge spot generated by magnetorheological finishing. The results suggest that the color center formation is directly associated with the damage resistance of the optics. Laser durable grade CaF2 demonstrates higher damage resistance to the X-ray irradiation when compared to excimer ArF laser grade CaF2. Subsurface-damage-free CaF2 surfaces further enhance the damage resistance.

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Nanosecond laser-induced surface damage and material failure mechanism of single crystal CaF2 (111) at 355 nm

Kang

Han

et al. 2019

Applied Surface Science

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Laser-induced damage of F-SiO₂ protected fluoride-based AR coatings on subsurface-damage-free CaF₂ at 193 nm

Cited by 5 publications

References 3 publications

Nanosecond laser-induced surface damage and its mechanism of CaF2 optical window at 248 nm KrF excimer laser

Nanosecond laser-induced surface damage and its mechanism of CaF2 optical window at 248 nm KrF excimer laser

Surface and bulk damage resistance of calcium fluoride optics assessed by x-ray induced color centers

Nanosecond laser-induced surface damage and material failure mechanism of single crystal CaF2 (111) at 355 nm

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Laser-induced damage of F-SiO2 protected fluoride-based AR coatings on subsurface-damage-free CaF2 at 193 nm

Cited by 5 publications

References 3 publications

Nanosecond laser-induced surface damage and its mechanism of CaF2 optical window at 248 nm KrF excimer laser

Nanosecond laser-induced surface damage and its mechanism of CaF2 optical window at 248 nm KrF excimer laser

Surface and bulk damage resistance of calcium fluoride optics assessed by x-ray induced color centers

Nanosecond laser-induced surface damage and material failure mechanism of single crystal CaF2 (111) at 355 nm

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Laser-induced damage of F-SiO₂ protected fluoride-based AR coatings on subsurface-damage-free CaF₂ at 193 nm

Nanosecond laser-induced surface damage and material failure mechanism of single crystal CaF2 (111) at 355 nm