&lt;title&gt;Effect of SiO2 overcoat thickness on laser damage morphology of HfO2/SiO2 Brewster's angle polarizers at 1064 nm&lt;/title&gt;

Stolz, Christopher J.; Génin, François Y.; Reitter, T.A.; Molau, N.E.; Bevis, Ron P.; Gunten, Marc K. Von; Smith, Douglas J.; Anzellotti, J. F.

doi:10.1117/12.274272

Cited by 36 publications

(16 citation statements)

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“…(5), the physical parameters used in the calculation are listed in Table 1 [20] . Obtaining the numerical results is easy.…”

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confidence: 99%

Thermomechanical analysis of nodule damage in HfO2/SiO2 multilayer coatings

Shan¹,

He²,

Wei³

et al. 2011

中国光学快报

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Samples with nodular defects grown from gold nanoparticles are prepared, and laser-induced damage tests are conducted on them. Nodular defects, which are in critical state of damage, are cross-sectioned by focusing on the ion beam and by imaging using a field emission scanning electron microscope. The crosssectional profile shows that cracks are generated and propagated along the nodular boundaries and the HfO2/SiO2 interface, or are even melted. The thermomechanical process induced by the heated seed region is analyzed based on the calculations of temperature increase and thermal stress. The numerical results give the critical temperature of the seed region and the thermal stress for crack generation, irradiated with threshold fluence. The numerical results are in good agreement with the experimental ones.OCIS Nodular defect, a typical defect in multilayer coatings, largely limits the improvement of the laser-induced damage threshold (LIDT) in the nanosecond regime and thus has been widely investigated. Electric field enhancement in the nodule, induced by the microlens effect of the dome structure of nodular defects, is an important factor in reducing the LIDT [1−5] . Recently, Liu et al. has examined the relationship between the structure feature of the nodular defect and the resistance of laserinduced damage (LID) [6−8] . Some simple thermal stress simulations and a simple thermo-mechanical model had been developed to understand the damage mechanism of the nodular defect [9−11] . The critical condition of crack generation regarded as a damage criterion and the corresponding LIDT were given based on the average temperature of the seed zone. However, the critical temperature of crack generation, the distribution of thermal stress, and the position of crack generation remain to be elucidated.Our previous work focused on investigating the characteristics and the electric field enhancement of nodular defects [12] . The geometric characteristics of nodular defect were determined by the seed. The height of the nodular dome and the continuity of the nodular boundary mainly determine the LIDT. The strong absorptive seed and microlens effect of the nodule play important roles in the LID of the nodule.In this letter, samples with nodular defects grown from gold nanoparticles were prepared, LID tests were performed. The thermomechanical process induced by the heated seed zone was analyzed. The morphology of a critically damaged nodule was analyzed with a double-beam microscope (Auriga, Zeiss, Germang) which combines the functions of the focused ion beam and the field emission scanning electron microscope (FESEM).The preparation of the samples, which are multilayer coatings with gold nanoparticles deposited on the surface of the substrate, and the details of the LID tests have been described in Ref. [12]. The total thickness of the coatings is about 4.0 µm, and the films are deposited by electron beam evaporation. The reflection coefficient of these samples is about 99% at 1 064 nm. The morphologies of nodule ejection ...

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“…(5), the physical parameters used in the calculation are listed in Table 1 [20] . Obtaining the numerical results is easy.…”

mentioning

confidence: 99%

Thermomechanical analysis of nodule damage in HfO2/SiO2 multilayer coatings

Shan¹,

He²,

Wei³

et al. 2011

中国光学快报

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“…Polarizer coatings tend to be highly optimized designs so it is impossible to determine the use of an overcoat by whether the number of layers is odd or even so unfortunately the only available overcoat information was the data provided by participant K. Overcoat thicknesses have been determined to have a significant impact on the laser resistance of Brewster angle plate polarizers at "S" polarization, however, this remains an unanswered question at "P" polarization. 12 …”

Section: Resultsmentioning

confidence: 99%

Brewster Angle Polarizing Beamsplitter Laser Damage Competition: P polarization

Stolz

Runkel²

2012

SPIE Proceedings

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Brewster angle plate polarizing beamsplitters play a critical role in splitting and combining beams within high power laser systems. A laser damage competition of polarizer beamsplitter coatings creates the opportunity to survey the current laser resistance these coatings within private industry, governmental institutions, and universities by a direct comparison of samples tested under identical conditions. The requirements of the coatings are a minimum transmission of 95% at "P" polarization and minimum reflection of 99% at "S" polarization at 1064 nm and 56.4 degrees angle of incidence. The choice of coating materials, design, and deposition method were left to the participant. Laser damage testing was performed according to the ISO 11254 standard utilizing a 1064 nm wavelength laser with a 10 ns pulse length operating at a repetition rate of 20 Hz. A double blind test assured sample and submitter anonymity so only a summary of the results are presented. In addition to the laser resistance results, details of cleaning methods, deposition processes, coating materials and layer count, and spectral results are also shared. Because of the large number of samples that were submitted, damage testing was conducted at "P" polarization only with "S" polarization damage testing reserved for next year on these submitted samples. Also the samples were only tested in the forward propagating direction; specifically samples were irradiated from air as the incident medium, through the thin film, and then through the substrate. In summary, a 6:1 difference existed for "P" polarization damage fluences amongst all of the competitors with the dominate variables that impacted the laser resistance being the deposition materials, deposition process, and cleaning method.

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“…They represent the type of damage that most limits the functional threshold of the high reflectors, and particularly polarizers. 25,27 The recent development effort of NIF polarizers focused on eliminating the cause of delamination. Other research conducted in parallel with this study also showed that the electric field distribution in the multilayer stack (which can vary with thin film design or beam incidence angle) can strongly influence the damage morphology.…”

Section: Delaminatesmentioning

confidence: 99%

“…reducing the optical absorption), [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] optimizing and controlling the thin film design and spectral performance. 1,24,25 However, as designers are pushing the peak operating fluence of the laser to levels where defects can easily induce damage, it has become important to acknowledge that the production of large-area defect-free optics is not possible with the current technology. On the other hand, it has been observed on existing systems such as the Nova laser at LLNL and the Omega laser at the University of Rochester that damaged optics can often still operate without critical loss of performance.…”

Section: Introductionmentioning

confidence: 99%

<title>Growth of laser-induced damage during repetitive illumination of HfO2/SiO2 multilayer mirror and polarizer coatings</title>

1997

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Lawrence Livermore National Laboratory, Laser Materials Department, Livermore, California 94550. ABSTRACTAs designers want to increase the peak fluence of high power laser, it becomes necessary to tolerate some damage on mirrors and polarizers. To quantify how the different types of damage morphologies initiate and grow during repetitive illumination, hafnia-silica multilayer mirror and polarizer coatings were laser damage tested. The coatings were prepared by e-beam evaporation and irradiated with a 3-ns-pulse at 1064 nm.The morphology of laser-induced damage was recorded after each shot to determine the types of damage that cause massive unstable failure and lower the optic's functional damage threshold. The results of the tests were summarized on damage stability maps plotting the average damage size as a function of the number of shots for fluences ranging from 10 to 40 J/cm The results show that the delaminate damage morphology should be prevented. This knowledge has allowed coatings development efforts to focus on eliminating the origin of such damage morphology.

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<title>Effect of SiO2 overcoat thickness on laser damage morphology of HfO2/SiO2 Brewster's angle polarizers at 1064 nm</title>

Cited by 36 publications

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Thermomechanical analysis of nodule damage in HfO2/SiO2 multilayer coatings

Thermomechanical analysis of nodule damage in HfO2/SiO2 multilayer coatings

Brewster Angle Polarizing Beamsplitter Laser Damage Competition: P polarization

<title>Growth of laser-induced damage during repetitive illumination of HfO2/SiO2 multilayer mirror and polarizer coatings</title>

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