&lt;title&gt;Failure characterization of nodular defects in multilayer dielectric coatings&lt;/title&gt;

Sawicki, R.; Shang, C. C.; Swatloski, T. L.

doi:10.1117/12.213718

Cited by 13 publications

(8 citation statements)

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“…23 More elaborate calculations taking into account the electric field enhancements by nodular defects 24,25 have also been performed. However, these more sophisticated calculations only apply to normal incidence.…”

Section: Electric Field Distribution In a Perfect Multilayermentioning

confidence: 99%

<title>Effect of electric field distribution on the morphologies of laser-induced damage in hafnia-silica multilayer polarizers</title>

et al. 1997

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Hafnia-silica multilayer polarizers were deposited by e-beam evaporation onto BK7 glass substrates. The polarizers were designed to operate at a wavelength of 1064 nm at Brewster's angle (56°). The polarizers were tested with a 3-ns laser pulse at 45°, 56°, and 65° incidence angle in order to vary the electric field distribution in the multilayer, study their effects on the damage morphology, and investigate the possible advantages of off-use angle laser conditioning. The morphology of the laser-induced damage was characterized by optical and scanning electron microscopy. Four distinct damage morphologies (pit, flat bottom pit, scald, and outer layer delamination) were observed.These damage morphologies were found to depend strongly on the angle of incidence of the laser beam. In particular, massive delamination observed at 45° and 56° incidence, did not occur at 65°. Instead, large and deep pits were found at 65°. The electric field distribution, the temperature rise and the change in stress in the multilayer were calculated to attempt to better understand the relationship between damage morphology, electric field peak locations, and maximum thermal stress gradients. The calculations showed a two-fold increase in stress change in the hafnia top layers depending on the incidence angle. The stress gradient in the first hafnia-silica interface was found to be highest for 45°, 56°, and 65°, respectively. Finally, the maximum stress was deeper in the multilayer at 65°. Although the limitations of such simple thermal mechanical model are obvious, the results can explain that outer layer delamination is more likely at 45° and 56° than 65° and that damage sites are expected to be deeper at 65°.

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Section: Electric Field Distribution In a Perfect Multilayermentioning

confidence: 99%

<title>Effect of electric field distribution on the morphologies of laser-induced damage in hafnia-silica multilayer polarizers</title>

et al. 1997

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“…Laser damage in thin films has consistently been associated with the presence of these nodular defects [3,4]. A simple parabolic model similar to the nodule geometry is widely used by researchers [5][6][7][8][9][10]. Electric field enhancements induced by nodular defects with different sizes, depths, and shapes have been studied based on this simple model [5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

“…Nodular ejection happens when the thermal-induced stress caused by the electric field exceeds the yield stress of the film surface. A simple simulation about stress was presented based on the simple model [9,10]. An atomic force microscope [11], scanning electron microscope (SEM) [12], and photothermal microscope [13] have been used to characterize nodules before and after laser irradiation, and a correlation was observed between nodule height and geometries with the damage sensitivity [11,12].…”

Section: Introductionmentioning

confidence: 99%

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Further investigation of the characteristics of nodular defects

Liu

Zhao

et al. 2010

Appl. Opt.

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To increase the understanding of the damage sensitivity of nodular defects and provide exact evidence for theoretical study, the structures and the damage behavior of nodular defects in electron-beam deposited mirrors of HfO 2 =SiO 2 are systemically investigated with a double-beam microscope (focused ion beam, scanning electron microscope). Nodular defects are classified into two kinds. In one kind the boundaries between nodules and the surrounding layers have become continuous for the last deposited materials, and in the other there are discontinuous boundaries between nodules and the surrounding layers. Nodular defects of the first kind typically have low domes, and the second have high domes. Laser damage experiments show that nodular defects of the first kind usually have a high laser resistance, and the laser-induced damage thresholds are limited in the second class of nodules. The dominant parameter of nodular defects related to damage is the height of the nodular defect.

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“…Indeed, the jEj 2 distribution determines the spatial distribution of the absorbed laser energy in the area surrounding a nodule, knowledge of which is an important precondition to understanding the subsequent complex processes of temperature distribution, stress response and mechanical damage. 19 Without clear knowledge of the jEj 2 distributions and of how those distributions affect the damage behavior of nodules, it is impossible to gain a true understanding of the thermomechanical damage process of nodules. The reason why previous studies failed to find a dependence of nodular damage on jEj 2 distributions is easy to explain.…”

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confidence: 99%

The effect of an electric field on the thermomechanical damage of nodular defects in dielectric multilayer coatings irradiated by nanosecond laser pulses

et al. 2013

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Thermomechanical damage of nodules in dielectric multilayer coatings that are irradiated by nanosecond laser pulses has been interpreted with respect to mechanical properties and electric-field enhancement. However, the effect of electric-field enhancement in nodular damage, especially the influence of electric-field distributions, has never been directly demonstrated through experimental results, which prevents the achievement of a clear understanding of the damage process of nodular defects. Here, a systematic and comparative study was designed to reveal how electric-field distributions affect the damage behavior of nodules. To obtain reliable results, two series of artificial nodules with different geometries and film absorption characteristics were prepared from monodisperse silica microspheres. After establishing simplified geometrical models of the nodules, the electric-field enhancement was simulated using a three-dimensional finite-difference time-domain code. Then, the damage morphologies of the artificial nodules were directly compared with the simulated electric-field intensity profiles. For both series of nodules, the damage morphologies reproduced our simulated electric-field intensity distributions very well. These results indicated that the electric-field distribution was actually a bridge that connected the nodular mechanical properties to the final thermomechanical damage. Understanding of the damage mechanism of nodules was deepened by obtaining data on the influence of electric-field distributions on the damage behavior of nodules.

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<title>Failure characterization of nodular defects in multilayer dielectric coatings</title>

Abstract: Thisisrpreprintofrpinteuded for publication ina journalorpmceedings. Since changes may be made before publication, this preprint is made available with the understandmg titat it will not be cited or reproduced without the permission of the author.

Cited by 13 publications

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<title>Effect of electric field distribution on the morphologies of laser-induced damage in hafnia-silica multilayer polarizers</title>

<title>Effect of electric field distribution on the morphologies of laser-induced damage in hafnia-silica multilayer polarizers</title>

Further investigation of the characteristics of nodular defects

The effect of an electric field on the thermomechanical damage of nodular defects in dielectric multilayer coatings irradiated by nanosecond laser pulses

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