Damage threshold investigations of high-power laser optics under atmospheric and vacuum conditions

Jensen, Lars; Jupé, Marco; Mädebach, H.; Ehlers, Henrik; Starke, K.; Ristau, Detlev; Riede, Wolfgang; Allenspacher, Paul; Schroeder, Helmut

doi:10.1117/12.696443

Cited by 24 publications

(20 citation statements)

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“…These deposits are reduced by the presence of oxygen in the atmosphere, but grow unchecked in sealed systems or under vacuum. The other observation of reduced damage resistance was associated with the absorption of water vapor by films [8]. It was hypothesized that local strain in the film induced by adsorbed water reduces their damage threshold.…”

Section: Introductionmentioning

confidence: 99%

“…Previous studies with nanosecond lasers under vacuum and sealed atmospheric conditions have shown that the useful lifetime of the optics and multiple pulse damage fluence reduced significantly for dielectric films [5][6][7][8] and bulk materials [9,10] compared to atmospheric conditions. Two explanations have been given for these observations.…”

Section: Introductionmentioning

confidence: 99%

“…In both cases, the effects of ambient gas on the laser damage threshold are more prominent in films prepared by electron-beam evaporation. When using high-density films such as those prepared by ion-assisted deposition, the deposition rate of graphite is reduced by a factor of 50 [5] and the effect of water eliminated [8].…”

Section: Introductionmentioning

confidence: 99%

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Femtosecond pulse damage thresholds of dielectric coatings in vacuum

Nguyễn¹,

Emmert²,

Schwoebel³

et al. 2011

Opt. Express

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At 10 -7 Torr, the multiple femtosecond pulse damage threshold, F(∞), is about 10% of the single pulse damage fluence F(1) for hafnia and silica films compared to about 65% and 50%, respectively, at 630 Torr. In contrast, the single-pulse damage threshold is pressure independent. The decrease of F(∞) with decreasing air pressure correlates with the water vapor and oxygen content of the ambient gas with the former having the greater effect. The decrease in F(∞) is likely associated with an accumulation of defects derived from oxygen deficiency, for example vacancies. From atmospheric air pressure to pressures of ~3x10 -6 Torr, the damage "crater" starts deterministically at the center of the beam and grows in diameter as the fluence increases. At pressure below 3x10 -6 Torr, damage is initiated at random "sites" within the exposed area in hafnia films, while the damage morphology remains deterministic in silica films. A possible explanation is that absorbing centers are created at predisposed sample sites in hafnia, for example at boundaries between crystallites, or crystalline and amorphous phases.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Femtosecond pulse damage thresholds of dielectric coatings in vacuum

Nguyễn¹,

Emmert²,

Schwoebel³

et al. 2011

Opt. Express

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“…10 For these ns pulses, the 1-on-1 and multiple-pulse LIDTs were similar in air and vacuum environments for the higher density (IBS and IAD) and also lower density (non-IAD) coatings in the case of the tests at 1064 nm, but only for the higher density (IBS and IAD) coatings in the case of the tests at 355 nm. The study attributed the ambient-vacuum LIDT similarity for the higher density coatings to their low absorption of water, making their amorphous structures free of water whether they are in air or vacuum.…”

Section: Dilemmas In Lidt Tests Of Bbhr Coatingsmentioning

confidence: 74%

“…Several specific studies [8][9][10][11] have explained vacuum-ambient LIDT differences primarily in terms of the amount of water absorbed from an ambient environment by a coating, especially one that is less dense/more porous. Two studies were for pulses in the fs regime and specific to single layers of HfO 2 and SiO 2 deposited by ion-beam sputtering (IBS), with 50 fs LIDT test laser pulses of 800-nm center wavelength and 1-kHz pulse repetition rate (PRR).…”

Section: Dilemmas In Lidt Tests Of Bbhr Coatingsmentioning

confidence: 99%

Analysis of laser damage tests on coatings designed for broad bandwidth high reflection of femtosecond pulses

et al. 2016

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Abstract. We designed an optical coating based on TiO 2 ∕SiO 2 layer pairs for broad bandwidth high reflection (BBHR) at 45-deg angle of incidence (AOI), P polarization of femtosecond (fs) laser pulses of 900-nm center wavelength, and produced the coatings in Sandia's large optics coater by reactive, ion-assisted e-beam evaporation. This paper reports on laser-induced damage threshold (LIDT) tests of these coatings. The broad HR bands of BBHR coatings pose challenges to LIDT tests. An ideal test would be in a vacuum environment appropriate to a high energy, fs-pulse, petawatt-class laser, with pulses identical to its fs pulses. Short of this would be tests over portions of the HR band using nanosecond or sub-picosecond pulses produced by tunable lasers. Such tests could, e.g., sample 10-nm-wide wavelength intervals with center wavelengths tunable over the broad HR band. Alternatively, the coating's HR band could be adjusted by means of wavelength shifts due to changing the AOI of the LIDT tests or due to the coating absorbing moisture under ambient conditions. We had LIDT tests performed on the BBHR coatings at selected AOIs to gain insight into their laser damage properties and analyze how the results of the different LIDT tests compare.

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