Localized CO_2 laser damage repair of fused silica optics

Mendez, Enrique; Nowak, K.; Baker, H. J.; Villarreal, Francisco; Hall, D. R.

doi:10.1364/ao.45.005358

Cited by 98 publications

(54 citation statements)

References 16 publications

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“…The operation of large aperture, high fluence laser systems such as the National Ignition Facility, depend on an effective remanufacturing or 'recycling' strategy to maximize the lifetime of high cost optics prone to damage [1][2][3][4]. In particular, the fused silica optics used as focusing elements are generally quite thick (~4cm), and must be produced from high-quality, inclusion-free SiO 2 , making these elements relatively expensive and of highest interest in terms of damage repair and recycling.…”

Section: Introductionmentioning

confidence: 99%

“…However, such an operation is currently impractical given the high-grade finish that accompanies a new optic, and alternatives involving some acceptable modification of the damaged region must be pursued. Recently, CO 2 laser damage mitigation has been shown to repair and arrest the growth of damage sites created from 351nm pulses [1][2][3][4]. Because the region of the optical surface that was once damaged then becomes transformed into a region different from the original pristine material, limits must be placed on this transformation in terms of laser operation.…”

Section: Introductionmentioning

confidence: 99%

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Downstream intensification effects associated with CO 2 laser mitigation of fused silica

et al. 2007

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Mitigation of 351nm laser-induced damage sites on fused silica exit surfaces by selective CO 2 treatment has been shown to effectively arrest the exponential growth responsible for limiting the lifetime of optics in high-fluence laser systems. However, the perturbation to the optical surface profile following the mitigation process introduces phase contrast to the beam, causing some amount of downstream intensification with the potential to damage downstream optics. Control of the laser treatment process and measurement of the associated phase modulation is essential to preventing downstream 'fratricide' in damage-mitigated optical systems. In this work we present measurements of the surface morphology, intensification patterns and damage associated with various CO 2 mitigation treatments on fused silica surfaces. Specifically, two components of intensification pattern, one on-axis and another off-axis can lead to damage of downstream optics and are related to rims around the ablation pit left from the mitigation process. It is shown that control of the rim structure around the edge of typical mitigation sites is crucial in preventing damage to downstream optics.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Downstream intensification effects associated with CO 2 laser mitigation of fused silica

et al. 2007

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“…Below the silica ablation threshold, the heat penetration depth (1D) is smaller than the laser spot diameter and the surface temperature is kept down by the pulse energy for short pulse widths. For longer pulses; on the contrary, the penetration depth is increased along both radial and axial direction with larger heated spot radius [22]. When the pulsed CO 2 laser exposed on SiO 2 surface, the energy dissipated in several µm depth and the surface of glass melts and gets into fluidic phase and it turns into solid when the exposure is over.…”

Section: Co 2 Laser-silica Interactionmentioning

confidence: 99%

CO2 laser polishing of conical shaped optical fiber deflectors

2017

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have been proposed and several types are currently used for tissue ablation. The types of deflector shapes are bare, sidefiring and radial. Bare fiber optic deflectors (basic deflector geometry) transmit the laser energy in the same direction along the fiber. Side-firing optical fiber optical deflectors transmit laser light perpendicular to the fiber axis through specific direction and they are widely used in many medical applications, especially in the prostate tumor ablation [1]. One of the most popular deflector types is radial design. Radial fiber optic deflectors with conically shaped optical fiber end transmit the laser energy radially and the laser energy is homogeneously distributed into a ring-shaped beam. These deflectors are especially used in endovenous laser ablation (EVLA) [2]. Unlike other cone-shaped fiber optical probes [3][4][5][6][7] used for various applications, EVLA operation needs μm-scale, multimode (MM) optical fibers and specific cone-angle values to fulfill the EVLA operation requirements. Thus, multi-mode, larger NA and μm-scale optical fibers are preferred in the operations. The homogeneous, ring-shaped laser energy distribution can be achieved with large cone angles which are detailed in this study. It allows a perfect irradiation of vein walls and their ablation. Among existent fiber processing methods such as chemical, FIB [3][4][5], mechanical polishing method is the best candidate to obtain such desired cone-angles. Furthermore, mechanical polishing process is applicable for mass-production of conical shaped optical fibers used in EVLA operation. In the mechanical polishing process, the deflector geometry is first formed with rough lapping film, then, the surface roughness of the deflector is gradually smoothed by polishing with smoother lapping films [8]. This process is composed of several steps to obtain high quality surface structures and a well-prepared fiber deflector surface eliminates the optical losses such as scattering and back reflection. However, the mechanical fining Abstract A novel method for polishing conical shaped optical fiber deflectors by modulated CO 2 laser exposure is reported. The conical shaped fiber deflector geometry was first formed with rough mechanical polishing, then it was exposed to modulated CO 2 laser operating with wavelength at 10.6 µm to achieve fine polish surfaces. The motivation of this work is to demonstrate that the modulated CO 2 laser exposure approach allows a fiber surface roughness at a nanometer scale without modifying the conical shape of the fiber deflector. The average surface roughness of mechanically polished fiber deflectors with 30 and 9 µm lapping films was smoothed down to 20.4 and 4.07 nm, respectively, after CO 2 laser polishing process. By combining mechanical and laser polishing techniques, fabrication of conical shaped optical fiber deflectors takes less time and it becomes laborer independent and easy to apply.

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“…The video shows that a large fraction of the glass is ablated during the first few rotations of the fibre. The temperature of the irradiated zones then drops below the evaporation temperature of silica glass (2700°C [13]) because the fibre is no longer in the direct path of a focused Gaussian beam. At this point, the process is dominated by laser polishing of the fibre end-face surface.…”

Section: Approachmentioning

confidence: 99%

“…In addition to controlled shaping of silica glass through ablation, the CO 2 laser can also be used for polishing [10][11][12][13] resulting in ultralow scattering loss and increasing the laser damage resistance of surfaces [13][14][15]. CO 2 laser polishing promises a non-contact approach with fast preparation times and high quality surface finishes for silica glass fibres.…”

Section: Introductionmentioning

confidence: 99%

High precision 96 µm CO_2 laser end-face processing of optical fibres

Boyd¹,

Rees²,

Simakov³

et al. 2015

Opt. Express

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Reproducible, precise cleaving of optical fibres is of great importance to the fibre laser and telecommunications industries. We present a novel approach to the end-face processing of optical fibres using a 9.6 µm CO 2 laser to produce flat, smooth and symmetric fibre end-face profiles with no rounding or melting at the edges of the fibre. As a demonstration, precision cleaving of a 400 µm diameter optical fibre is reported. For this fibre a topographical profile height of <400 nm (0.06°) and a reproducibility better than 200 nm (0.03°) was achieved. To the best of our knowledge this is the first demonstration of a CO 2 process that has generated a fibre endface topography substantially smaller than a typical mechanical cleave. Highlighting the flexibility of this system, we have also demonstrated the generation of near arbitrary fiber end-face profiles such as discrete phase steps and non-spherical surface profiles.

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Localized CO_2 laser damage repair of fused silica optics

Cited by 98 publications

References 16 publications

Downstream intensification effects associated with CO 2 laser mitigation of fused silica

Downstream intensification effects associated with CO 2 laser mitigation of fused silica

CO2 laser polishing of conical shaped optical fiber deflectors

High precision 96 µm CO_2 laser end-face processing of optical fibres

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