Refractive and diffractive laser beam shaping optics

Umhofer, Udo; Jäger, Erwin; Bischoff, Christian

doi:10.1002/latj.201190020

Cited by 16 publications

(7 citation statements)

References 2 publications

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“…Two types of optical elements are used in field mapping solutions, i.e., refractive optic elements (ROEs) and diffractive optic elements (DOEs). DOEs are typically thin and light weight and therefore the diffractive field mapping has a lower resistance to laser light and can also lead to energy losses [28]. At the same time, small optical elements allow compact beam shapers to be designed that are very suitable for integration in relatively small laser processing systems.…”

Section: Laser Beam Shaping Technologymentioning

confidence: 99%

“…The other field mapping solution employs ROEs to deflect each pixel on an input plane at a specific angle and, thus, creating a given profile at the image plane [28,30]. Some advantages of the refractive field mapping are its high transmission efficiency, a relatively simple design that make them easier to manufacture and also ROE based shaper are easier to integrate into existing laser processing systems [31].…”

Section: Laser Beam Shaping Technologymentioning

confidence: 99%

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Effects of Top-hat Laser Beam Processing and Scanning Strategies in Laser Micro-Structuring

Penchev

Henrottin³

et al. 2020

Micromachines

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The uniform energy distribution of top-hat laser beams is a very attractive property that can offer some advantages compared to Gaussian beams. Especially, the desired intensity distribution can be achieved at the laser spot through energy redistribution across the beam spatial profile and, thus, to minimize and even eliminate some inherent shortcomings in laser micro-processing. This paper reports an empirical study that investigates the effects of top-hat beam processing in micro-structuring and compares the results with those obtainable with a conventional Gaussian beam. In particular, a refractive field mapping beam shaper was used to obtain a top-hat profile and the effects of different scanning strategies, pulse energy settings, and accumulated fluence, i.e., hatch and pulse distances, were investigated. In general, the top-hat laser processing led to improvements in surface and structuring quality. Especially, the taper angle was reduced while the surface roughness and edge definition were also improved compared to structures produced with Gaussian beams. A further decrease of the taper angle was achieved by combining hatching with some outlining beam passes. The scanning strategies with only outlining beam passes led to very high ablation rates but in expense of structuring quality. Improvements in surface roughness were obtained with a wide range of pulse energies and pulse and hatch distances when top-hat laser processing was used.

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Section: Laser Beam Shaping Technologymentioning

confidence: 99%

Section: Laser Beam Shaping Technologymentioning

confidence: 99%

Effects of Top-hat Laser Beam Processing and Scanning Strategies in Laser Micro-Structuring

Penchev

Henrottin³

et al. 2020

Micromachines

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“…Beam shaping by diffractive or refractive optics can produce arbitrary intensity distributions in a plane of interest, which can also be the focal plane of a laser. 71 However, the z-location of the optical elements is again critical, and combining this technique with beam scanning is impossible. Moreover, intensity peaks ("hot spots") are usually located in front or behind of the plane with the desired intensity distribution, which compromises plasma-mediated cutting in a well-defined plane.…”

Section: Implementation Of Focus Shaping Into Clinical Systemsmentioning

confidence: 99%

Optical Vortex Beam for Gentle and Ultraprecise Intrastromal Corneal Dissection in Refractive Surgery

Freidank

Vogel

Linz

2020

Trans. Vis. Sci. Tech.

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We introduce a novel focus shaping concept for intrastromal corneal dissection that facilitates cleavage along corneal lamellae, and we analyze laser-tissue interactions governing cutting effectiveness and mechanical side effects. Methods: Focus shaping was achieved by a spiral phase plate that converts an incident Gaussian beam into a Laguerre-Gaussian beam with a helical phase. Such vortex beams have zero intensity at their center, are propagation invariant, and possess a ring focus equal in length to the Gaussian focus but with a larger diameter. Cutting precision and the required absorbed energy for flap dissection were compared for Gaussian and vortex beams on ex vivo porcine corneal specimens at pulse durations between 480 fs and 9 ps. Cutting quality and bubble formation were characterized by scanning electron microscopy and macro photography. Results: With the vortex beam, the cuts were much smoother. Bubble formation was markedly reduced because cutting can be performed close to the bubble threshold, whereas with the Gaussian beam energies well above threshold are needed. Although the incident energy at the flap dissection threshold was slightly larger for the vortex beam, the absorbed energy was much smaller and contributed more effectively to cutting. This reduced plasma-induced pressure more than sevenfold. Conclusions: The vortex beam approach for corneal dissection is a simple, versatile, and cost-effective way of improving the precision of refractive surgery while reducing bubble formation and pressure-related mechanical side effects. Translational Relevance: Phase plates for propagation invariant vortex beams are easily implemented in the beam path of next-generation clinical devices.

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“…[1][2][3] Especially, when lasers are used to ablate materials or illuminate photomasks in manufacturing processes, it is often desirable to have a uniform intensity distribution over the cross-section of the beam. [4][5][6] Extensive efforts have been made to develop essential design and fabrication techniques to meet this need. [7,8] In general, designing a beam-shaping system needs to consider two steps, i.e., a phase profile φ(x, y) needed to yield some target intensity profile and an optical element that can generate the desired phase profile.…”

Section: Doi: 101002/adom201800961mentioning

confidence: 99%

Liquid Crystal Pancharatnam–Berry Micro‐Optical Elements for Laser Beam Shaping

Jiang

Feng

et al. 2018

Advanced Optical Materials

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Shaping the intensity profile of a laser beam is desired by various industrial applications. In this paper, a new approach is presented to design and fabricate liquid crystal (LC) micro‐optical elements (MOEs) with engineered Pancharatnam–Berry (PB) phases for beam shaping. By generalizing the Snell's law for spatially variant PB phases, molecular orientation patterns are designed for the liquid crystal MOEs to shape a Gaussian laser beam into flattop intensity profiles with circular and square cross‐sections, with the β parameter varied from 4 to 42. It is demonstrated that such liquid crystal beam shaping MOEs can be fabricated with high throughput and high resolution by using a photopatterning technique based on plasmonic metamasks and that they produce excellent beam quality, no zero‐order light leakage with a beam size from 10 to 600 µm. As the plasmonic metamasks allow for encoding arbitrary molecular orientations, i.e., arbitrary geometric phase profiles, the approaches presented here are widely applicable to large‐scale manufacturing of liquid crystal MOEs for any beam shapes.

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Refractive and diffractive laser beam shaping optics

Cited by 16 publications

References 2 publications

Effects of Top-hat Laser Beam Processing and Scanning Strategies in Laser Micro-Structuring

Effects of Top-hat Laser Beam Processing and Scanning Strategies in Laser Micro-Structuring

Optical Vortex Beam for Gentle and Ultraprecise Intrastromal Corneal Dissection in Refractive Surgery

Liquid Crystal Pancharatnam–Berry Micro‐Optical Elements for Laser Beam Shaping

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