Degradation and restoration of dielectric-coated cavity mirrors in the NIJI-IV FEL

Yamada, Ken‐ichi; Yamazaki, Tetsuo; Sei, N.; Shimizu, Takashi; Suzuki, Ryoichi; Ohdaira, Toshiyuki; Kawai, Masayuki; Yokoyama, Minoru; Hamada, Shinji; Saeki, Kazuhiko; Nishimura, Eiichi; Mikado, T.; Noguchi, Toshihiko; Sugiyama, Shigeo; Chiwaki, M.; Ohgaki, Hideaki; Tomimasu, T.

doi:10.1016/0168-9002(94)01340-3

Cited by 21 publications

(11 citation statements)

References 7 publications

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“…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%

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%

Femtosecond pulse damage thresholds of dielectric coatings in vacuum

Nguyễn¹,

Emmert²,

Schwoebel³

et al. 2011

Opt. Express

View full text Add to dashboard Cite

show abstract

“…Previous studies of damage behavior by ns-laser pulses under vacuum and in sealed cavities have shown that the lifetime of optics is reduced [2,3,4,5,6] . In these cases, the mechanism for damage was the slow accumulation of graphitic layers from a background of organic vapors.…”

Section: Discussionmentioning

confidence: 99%

“…Previous work with bulk materials (fused-quartz [2] and BK7 [3] ) and dielectric coatings (SiO 2 [4] , HfO 2 , Ta 2 O 5 [5] , MgF 2 and CaF 2 [6] ) under vacuum or sealed atmospheric conditions with nanosecond irradiation showed a change in performance often as a form of optical damage at lower fluence or a reduction in the useful lifetime of the optics. For those mentioned materials the failure was ascribed to the accumulation of absorbing, graphitic layers created by photolytic cracking of organic compounds from aromatic hydrocarbon controlled deposits.…”

Section: Introductionmentioning

confidence: 98%

Studies of femtosecond laser induced damage of HfO 2 thin film in atmospheric and vacuum environments

et al. 2009

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The single pulse femtosecond laser induced damage threshold (LIDT) of hafnia and silica films is not affected by the ambient gas pressure. In vacuum, the multiple pulse LIDT drops to ~10% (~10%) of its atmospheric value for hafnia (silica). The water vapor content of the ambient gas was found to control the change in the LIDT. The LIDT of bulk fused silica surfaces did now show any dependence on the ambient gas pressure. Hydrocarbons (toluene) did not change the multiple pulse LIDT for Hafnia films

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“…Previous work with nanosecond pulses showed a reduction in the useful lifetime of the optics as well as a lower damage fluence for S-on-1 tests compared with atmospheric conditions for bulk materials (fused-quartz [1] and BK7 [2]) as well as dielectric coatings (SiO 2 [3], HfO 2 , Ta 2 O 5 [4], MgF 2 and CaF 2 [5]) under vacuum or sealed atmospheric conditions. Two possible mechanisms were discussed to explain this change in performance: contamination by organic residues [1][2][3][4][5] and desorption of water [6]. The former occurs as a result an accumulation of absorbing, graphitic layers.…”

Section: Introductionmentioning

confidence: 98%

The vacuum effect of femtosecond LIDT measurements on dielectric films

et al. 2010

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At ~10 -7 Torr, the multiple femtosecond pulse LIDT, F( ), is about 10% of the single pulse damage fluence for hafnia and silica films compared to ~75% at 630 Torr. The 1-on-1 LIDT is pressure independent. The decrease of F( ) is related to the water vapor and oxygen content of the ambient gas with the former having the largest effect. The decrease of F( ) is associated with a change in damage morphology. In air, the damage "crater" starts at the center of the beam and grow in diameter as the fluence increases. In contrast, the damage starts at random "sites" within the exposed area under vacuum. Absorbing centers are created by the removal of oxygen from predisposed sites (for example grain boundaries) on the film surfaces, producing absorbing states.

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Degradation and restoration of dielectric-coated cavity mirrors in the NIJI-IV FEL

Cited by 21 publications

References 7 publications

Femtosecond pulse damage thresholds of dielectric coatings in vacuum

Femtosecond pulse damage thresholds of dielectric coatings in vacuum

Studies of femtosecond laser induced damage of HfO 2 thin film in atmospheric and vacuum environments

The vacuum effect of femtosecond LIDT measurements on dielectric films

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