Gaussian profile laser intensification by nodular defects in mid-infrared high reflectance coatings

Wang, Ying; Zhang, Yueguang; Xu, Le; Wei-Lan, Chen; Gu, Ping

doi:10.1016/j.optcom.2007.06.046

Cited by 11 publications

(4 citation statements)

References 11 publications

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“…The height of this nodular defect is 2:3 μm, and the diameter is 1:04 μm. Therefore, previous experiments and theories that identify them as nearly equal [5][6][7][8] are one sided or idealized and are valid just for the first kind of nodule.…”

Section: Discussionmentioning

confidence: 99%

“…Nodular defects in multilayer dielectric films have been widely investigated since the 1990s [1][2][3][4][5][6][7][8][9][10][11][12][13]. Nodules are initiated by seed particles present on the substrate or deposited in the film during deposition and form a parabolic structure with the subsequent deposition of materials [1,2].…”

Section: Introductionmentioning

confidence: 99%

“…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]. Nodular defect-induced electric field enhancement can provide insight into laserinduced stress.…”

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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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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“…For the theoretical effort, we have utilized the FDTD method to quantify the electric-field distribution within the coating layers in the presence of the pre-defined defects of different shapes. This approach is motivated by the fact that laser-induced damage within thin film layers is strongly correlated with electric field intensification due to interference between incident beam and secondary waves created by the presence of thin film interfaces and coating defects [8][9][10][11]. Experimentally, we utilize femtosecond laser machining to fabricate mitigation structures suggested by the simulation work and to further examine the manufactured feature for damage resistance as well as to validate the theoretical predication.…”

Section: Introductionmentioning

confidence: 99%

Searching for optimal mitigation geometries for laser-resistant multilayer high-reflector coatings

et al. 2011

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Growing laser damage sites on multilayer high reflector coatings can limit mirror performance.One of the strategies to improve laser damage resistance is to replace the growing damage sites with pre-designed benign mitigation structures. By mitigating the weakest site on the optic, the large aperture mirror will have a laser resistance comparable to the intrinsic value of the multilayer coating. To determine the optimal mitigation geometry, the finite difference time domain method (FDTD) was used to quantify the electric-field intensification within the multilayer, at the presence of different conical pits. We find that the field intensification induced by the mitigation pit is strongly dependent on the polarization and the angle of incidence (AOI) of the incoming wave. Therefore the optimal mitigation conical pit geometry is application specific. Furthermore, our simulation also illustrates an alternative means to achieve an optimal 2 mitigation structure by matching the cone angle of the structure with the AOI of the incoming wave, except for the p-polarization wave at a range of incident angles between 30 and 45 .

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