Laser damage resistant pits in dielectric coatings created by femtosecond laser machining

Wolfe, Justin; Qiu, Ruoyi; Stolz, Christopher J.; Thomas, Michael; Martinez, Carolyn; Ozkan, Arzu

doi:10.1117/12.836906

Cited by 6 publications

(5 citation statements)

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“…Therefore, fs laser micromachining may become a possible method of mitigation damage growth based on these unique performances. Recently, Wolfe and co-workers [17,18] successfully used the method of fs laser machining to create mitigation sites in multilayer dielectric mirror coatings. In our previous work [19], an fs laser was also used to mitigate laser damage growth sites on a fused silica surface; the effect of different fs laser machining energies and geometries of mitigation sites were explored, but further research was needed to optimize the structure of mitigation sites and remove the redeposition material.…”

Section: Introductionmentioning

confidence: 99%

Method of mitigation laser-damage growth on fused silica surface

et al. 2013

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A reliable method, combining femtosecond (fs) laser mitigation and chemical (HF) etching, has been developed to mitigate laser-damage growth sites on a fused silica surface. A rectangular mitigation site was fabricated by an fs laser with a raster scan procedure; HF etching was then used to remove the redeposition material. The results show that the mitigation site exhibits good physical qualities with a smooth bottom and edge. The damage test results show that the growth threshold of the mitigation sites increases. Furthermore, the structural characteristic of samples was measured by a photoluminescence (PL) spectrometer, and the light intensification caused by damage and mitigation sites was numerically modeled by the finite-difference time-domain (FDTD). It revealed that the removal of damaged material and structure optimization contribute to the increase of the damage growth threshold of the mitigation site.

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Section: Introductionmentioning

confidence: 99%

Method of mitigation laser-damage growth on fused silica surface

et al. 2013

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“…These mitigation structures can be created by multiple techniques including femtosecond laser machining, single crystal high-speed diamond machining, and magnetorheological finishing [5][6][7]. In fact, our earlier study of creating rationally designed features utilizing femtosecond laser machining [5] has shown an increase in the laser damage threshold, from 15 J/cm 2 to 40 J/cm 2 for light at 1064 nm, with a 3ns pulse length. However, to maximize the effort, one must have a rational means to search for an optimal mitigation structure that can routinely yield a higher laser damage threshold than the operational fluence.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, an effort has been made to create conical pits of shallower cone angles using femtosecond laser machining [5]. As a consequence of the fabrication process, the edge of the cones becomes rough with a randomly oriented serrated morphology [17].…”

Section: Waveguide Effectmentioning

confidence: 99%

“…The input pit morphology for each simulation was derived from a digitized SEM image of the cross-section of the benign pit created by femtosecond laser machining in reference [5]. The cross-sectional view of conical pit with rough edge was achieved by a dual beam focused ion beam milling technique [18].…”

Section: Waveguide Effectmentioning

confidence: 99%

“…One of the strategies is to first initiate the damage precursors at fluencies below the operational fluence and then replace the initiated damage sites with a pre-designed benign mitigation structure [5] with a much higher damage threshold. These mitigation structures can be created by multiple techniques including femtosecond laser machining, single crystal high-speed diamond machining, and magnetorheological finishing [5][6][7]. In fact, our earlier study of creating rationally designed features utilizing femtosecond laser machining [5] has shown an increase in the laser damage threshold, from 15 J/cm 2 to 40 J/cm 2 for light at 1064 nm, with a 3ns pulse length.…”

Section: Introductionmentioning

confidence: 99%

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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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