Precise Laser Ablation with Ultra-Short Pulses

Momma, C.; Nolte, Stefan; Chichkov, Boris N.; Tünnermann, A.; Alvensleben, F. von

doi:10.1109/cleoe.1996.562552

Cited by 6 publications

(9 citation statements)

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“…Micro-engineering of products, devices and systems has been a growing field of research demanding new, innovative fabrication processes for nano/micro manufacturing of a wide range of materials [1]. Laser ablation or irradiation based micro-machining of basic geometric features on a variety of solid materials has been investigated by many researchers [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Lasers are usually categorized as two groups: continuous wave (c.w.)…”

Section: Introductionmentioning

confidence: 99%

Laser Micro-Machining of Spherical and Elliptical 3-D Objects Using Hole Area Modulation Method

Lee

̈zel

2007

ASME 2007 International Manufacturing Science and Engineering Conference

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Laser micromachining has the capability to fabricate very small and basic 2.5-D geometric features on a range of materials in the form of laser ablation or irradiation. Short pulsed lasers that can achieve wide range of wavelengths in the form of harmonics of infrared laser beam at 1064 nm wavelength have been a very effective micro-machining tool used for hole drilling, cutting, scribing, trimming and marking. A review of laser processing of materials is given in this paper. Direct laser ablation can be performed by controlling laser beam properties such as laser energy, intensity, pulse duration and wavelength in micro-machining 3-D geometric features. However, this method requires additional capabilities for a typical laser beam generating and delivery system. When the laser beam properties cannot be altered, Hole Area Modulation (HAM) method becomes alternative solution by controlling the density of the holes and the step size in a mask to improve the accuracy of the 3-D geometric feature. In this paper, we perform modeling, planning and simulation of laser micromachining with hole area modulation method to produce spherical and elliptical objects 3-D geometrical features that are typical for aspheric and or refractive micro-lenses. A computational methodology is developed to design a mask with varying density and diameter of the holes. The masks are created using micro-drilling and utilized in laser micromachining of 3-D objects on polycarbonate polymer substrates.

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Section: Introductionmentioning

confidence: 99%

Laser Micro-Machining of Spherical and Elliptical 3-D Objects Using Hole Area Modulation Method

Lee

̈zel

2007

ASME 2007 International Manufacturing Science and Engineering Conference

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“…There are two separate ablation phases, namely the "gentle" ablation phase and the "strong" ablation phase, therefore there are two different ablation rates [147]. Whilst operating in the "gentle" ablation phase in a low fluence regime (Fo < 1 J/cm 2 ), the energy of the laser pulses is mainly absorbed by free electrons, due to the inverse Bremsstrahlung ( Figure 5.36) [147]. The ablation rate is low and dependant on the optical penetration depth, a" , where a is the absorption coefficient of the material at the laser wavelength [145].…”

Section: Effect Of Laser Fluencementioning

confidence: 99%

“…Therefore, the heat conduction can be neglected, minimizing the effect of a heat-affected zone (HAZ) around the ablated feature. Also, since the thermal losses are absent, the hole can be drilled with much lower laser fluences [147].…”

Section: Effect Of Laser Fluencementioning

confidence: 99%

“…Therefore, the advantages of an ultrafast femtosecond pulsed laser over a longer pulsed laser such as a pico-or nanosecond pulsed laser are: very rapid creation of vapor and plasma phases, negligible heat conduction (minimal HAZ) and the absence of a liquid phase, allowing for better control and higher reproducibility of the ablation process [147].…”

Section: Effect Of Pulse Widthmentioning

confidence: 99%

“…Schematic of a shortpulse laser ablation in low fluence regime[147].For low laser fluences (Fo < 1 J/cm ), the ablation depth per pulse is given by:…”

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Sub-micromachining using femtosecond pulse laser interference phenomenon

Ho¹

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This research work sets out to achieve submicromachining capabilities on the femtosecond pulse laser which surpasses the conventional laser micromachining method of using the direct laser beam to machine. The aim is to achieve laser ablated features of 200nm and below with this novel research concept. With ultrafast pulse lasers such as the femtosecond pulse laser, subspot size micromachining is possible because of their precise threshold value. However, the sub-spot size ablation mechanism has reached its lowest limit when it hit the 1/1 Oth of the laser focal spot size range. Up to now, the smallest laser micromachined feature reported is 200nm in diameter, or approximately 8% of the original laser spot size of 2.5um. The aim of this research work is to break through this limit and obtain submicron features of below 200nm with the femtosecond pulse laser. To achieve this, a novel concept of using the phenomenon of femtosecond pulse laser interference to machine is proposed. The laser beam from the femtosecond pulse laser is first interfered to obtain a circular interference beam. The central bright fringe from the generated interference pattern which has a sharper beam profile is then used to machine. With this method, the effective ablation spot size is reduced, subsequently reducing the size of the feature size it ablates. One of the attractive characteristics of ultrafast pulse lasers is its precise threshold value. It is this feature which enables the ablation of sub-spot size features on these lasers. And by applying this same concept, only a fraction (a part of the central bright fringe) of the interfered beam within which the fluence is greater than the threshold of the material, can be made to machine.

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Space-resolved light emitting and lasing behaviors of crystalline perovskites upon femtosecond laser ablation

Rajan

Huang

et al. 2023

Materials Today Physics

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Precise Laser Ablation with Ultra-Short Pulses

Abstract: C Momma, S Nolfe, B Chichkov. A Tunnermann, F von Alvensleben Laser Zentrum Hannover e. V I Hollerithallee 8, 30419 Hannover Tel.: (i49) 511 2788-0, F a : (+49) 511 2788-100

Cited by 6 publications

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Laser Micro-Machining of Spherical and Elliptical 3-D Objects Using Hole Area Modulation Method

Laser Micro-Machining of Spherical and Elliptical 3-D Objects Using Hole Area Modulation Method

Sub-micromachining using femtosecond pulse laser interference phenomenon

Space-resolved light emitting and lasing behaviors of crystalline perovskites upon femtosecond laser ablation

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