Towards a Numerical Model of Picosecond Laser-Material Interaction in Bulk Sapphire

Results of the work in the Laser4Fun project has been published as:

L. Capuano, D. de Zeeuw and G.R.B.E. Römer. Towards a Numerical Model of Picosecond Laser-Material Interaction in Bulk Sapphire. JLMN-Journal of Laser Micro/Nanoengineering Vol. 13, No. 3, 2018

Abstract

Crystalline sapphire (Al2O3) is a hard and transparent material widely used in industry. When applying IR laser wavelengths, sapphire can be laser-processed inside the bulk (sub-surface) to produce 3D structures, which can find uses, for example, in the production of microfluidic devices. Ultrashort and tightly focused laser pulses trigger several energy absorption mechanisms inside the bulk. The absorbed energy locally modifies the structure of sapphire. Existing (numerical) models of sapphire laser processing describe mainly femtosecond pulsed laser-material interaction (most of them only addressing surface processing) and, in addition, these models do not simulate the laser-induced temperatures of the lattice. Therefore, this study is aimed at a 2D-axisymmetric, time dependent, numerical model of the physics in picosecond laser-material interaction with sapphire. The physical phenomena in model include, but are not limited to: multiphoton absorption, tunneling ionization, avalanche ionization, recombination of carriers, diffusion of carriers and heat diffusion. Based on these phenomena, three quantities are calculated, namely: electron density, electron temperature and lattice temperature. The model was implemented in COMSOL Multiphysics®. It was found that, sapphire is modified by the laser radiation only if avalanche ionisation is triggered in the bulk.

Link

DOI: 10.2961/jlmn.2018.03.0005

Controlling 2D laser nano structuring over large area with double femtosecond pulses

Results of the work in the Laser4Fun project has been published as:

F. Fraggelakis, G. Mincuzzi, J. Lopez, I. Manek-Hönninger and R. Kling. Controlling 2D laser nano structuring over large area with double femtosecond pulses. Applied Surface Science, November 2018

Abstract

Laser surface texturing is an established way to introduce surface functionalities on solid surfaces. By means of femtosecond laser sources, it’s possible to texture a variety of solids such as metals, semiconductors and transparent materials, introducing features of different symmetry and size. Fabrication of laser induced periodic surface structure (LIPSS) which typically range in the near-submicron length scale can lead to strong modifications of surface wetting, tribological and optical properties. Controlling LIPSS morphology could enable us to mimic functional textures found in nature, introducing functionalities such as antireflectivity and bactericidity. Several works demonstrate the impact of polarization control and double-pulse irradiation on determining texture symmetry and size. Here we present a comprehensive study on controlling laser induced structures by double femtosecond pulse irradiation. The effect of pulse polarization and interpulse delay is elucidated and the generation of novel 2D surface morphologies is reported. A plausible interpretation of the structure formation mechanism is proposed in the frame of non-linear convection flow. A high average power industrial femtosecond laser source with a pulse duration of 350 fs operating at high repetition rate was employed for the experiments. Large areas were processed by combining different 2D morphologies generating a holographic pattern. We believe that our results provide a novel insight in controlling laser induced submicron morphology. Moreover, the presented surface texturing process is scalable in terms of processed area and cycle time and fully compatible with high repetition rates, demonstrating for the first time the feasibility to introduce double-pulse processing in an industrial environment.

Link(s)

Morphology of single picosecond pulse subsurface laser-induced modifications of sapphire and subsequent selective etching

Results of the work in the Laser4Fun project has been published as:

L. Capuano, R. Pohl, R. M. Tiggelaar, J. W. Berenschot, J. G. E. Gardeniers, and G. R. B. E. Römer, “Morphology of single picosecond pulse subsurface laser-induced modifications of sapphire and subsequent selective etching” Opt. Express26, 29283-29295 (2018)

Abstract

The effect of 1030nm single picosecond pulsed laser-induced modification of the bulk of crystalline sapphire using a combined process of laser amorphization and selective wet chemical etching is studied. Pulse durations of more than 1 picosecond are not commonly used for this subsurface process. We examine the effect of 7 picosecond pulses on the morphology of the unetched, as well as etched, single pulse modifications, showing the variation of shape and size when varying the pulse energy and the depth of processing. In addition, a qualitative analysis of the material transformation after irradiation is provided as well as an analysis of cracking phenomena. Finally, a calculated laser intensity profile inside sapphire, using the Point Spread Function (PSF), is compared to the shape of the modifications. This comparison is employed to calculate the intensity threshold leading to amorphization, which equals 2.5⋅1014 ± 0.4⋅1014 W/cm2.

Links:

DOI: 10.1364/OE.26.029283

Laser-Induced Periodic Surface Structures (LIPSS) on Polymers Processed with Picosecond Laser Pulses

Results of the work in the Laser4Fun project has been published as:

Marek Mezera, Martin van Drongelen and G.R.B.E. Römer. Laser-Induced Periodic Surface Structures (LIPSS) on Polymers Processed with Picosecond Laser Pulses, Journal of Laser Micro/Nanoengineering  Vol. 13, No. 2, 2018; doi: 10.2961/jlmn.2018.02.0010

Abstract

Based on a literature review, it was concluded that Laser-induced Periodic Surface Structures (LIPSS) on polymers are produced when applying laser sources operating either in the ultraviolet wavelength and nanosecond pulse duration, or radiation of wavelengths ranging from 265nm to 1045nm and pulse durations in the femtosecond regime. LIPSS were not reported when using pico-second laser sources. The purpose of this paper is to study whether (and if so which) LIPSS form on polymers when picosecond pulsed laser source is applied. Low Spatial Frequency LIPSS (LSFL) and High Spatial Frequency LIPSS (HSFL) have been obtained on polycarbonate and on polystyrene when applying picosecond laser pulses at a wavelength of 343nm on single spots and on processed lines. When using a wavelength of 515nm, LSFL and HSFL have been produced only on polycar-bonate, but also led to porosity of the structured area.

Links:

DOI: 10.2961/jlmn.2018.02.0010

Annual Technical Board and Supervisory Board Meeting in Bari, Italy (2018)

The 2018 Technical Board (TB) meeting and Supervisory Board (SB) meeting of the Laser4Fun project took place on October 4 and 5 in Bari, Italy. The meeting was hosted by prof. Antonio Ancona of IFN-CNR, Istituto di Fotonica e Nanotecnologie, Bari, Italy. The TB & SB discussed the progress of the project, results, management and reporting issues, as well as communication and dissemination topics. Also all Early Stage Researchers (ESRs) presented their progress and results to the SB. We were happy to conclude the project is well on track.

Technical Board (TB) meeting and Supervisory Board (SB) and all ESRs during the annual progress meeting in Bari, Italy.
Technical Board (TB) and Supervisory Board (SB) and all ESRs during the annual progress meeting in Bari, Italy.

Summer School on Laser Micro/Nanostructuring and Surface Tribology 2018

The 3rd Laser4Fun international Summer School took place from October 1st to 5th and was hosted by prof. Antonio Ancona of the IFN-CNR, Istituto di Fotonica e Nanotecnologie in Bari, Italy. The participants of the summer school were “fully-immersed” into the world of Laser Micro/Nanostructuring and Surface Tribology. Lectures and presentations by academic experts and of the participants alternated, with ample time for discussions. Topics included, but were not limited to:

  • Contact mechanics of elastic bodies, by dr. Ing. Carmine Putignano (Politecnico di Bari, Department of Mechanics, Mathematics and Management)
  • Universal lab-on-a-chip platform for complex, perfused 3D tissues generated by 3D printing – opportunities and perspectives for laser technology, by dr. Ing. Udo Klotzbach (Fraunhofer-Institut Material and Beam Technology IWS Dresden, Business Unit Manager Microtechnology)
  • Management of innovative project at Bosch: LST case study, by ing. Antonio Grimaldi and Ing. Renato Giannoccaro (Robert Bosch Group – Centro Studi Componenti per Veicoli s.p.a)
  • Cross Cultural Competences through cooperation and autonomy. Learning organization: higher education management and research administration, by dr.ssa Mariapia Circella (Physics Department, University of Bari)
  • Femtosecond laser micro-fabrication of polymeric lab-on-chip for advanced and mini-invasive diagnostics, by Udith K. Vadakkum Vadukkal (University of Bari, Italy)
  • Femtosecond laser bursts induced micro and nanostructuring on steel surface, by Giuseppe Giannuzzi (Università di Bari, Italy)
  • Contact mechanics of viscoelastic bodies, by prof. Ing. Giuseppe Carbone (PoliBa- Department of Mechanics, Mathematics and Management)
  • University of 21st century: threats and opportunities. Organizational chart: practical experiences, by dr.ssa Mariapia Circella (Physics Department, University of Bari)
Prticipants of the international School on Laser Micro/Nanostructuring and Surface Tribology 1st-5th October 2018, Bari, Italy
Prticipants of the international School on Laser Micro/Nanostructuring and Surface Tribology
1st-5th October 2018, Bari, Italy

Melissa Sikosana breaks the wall of bacteria related deaths

On September 25th, Melissa Sikosana (ESR), has been awarded 3rd place by a distinguished jury, for “breaking the wall of bacteria related deaths”, at the “Falling Walls Lab Marie Sklodowska-Curie Actions Event“. This event was organised by the European Commission in collaboration with the European Parliament and supported by the Falling Walls Foundation.

The Falling Walls Lab challenging inter-disclipinary platform that invites talent academics, professionals and entrepreneurs from around the world to present breakthrough-research work, within 3 minutes, each to an audience of industry experts & decision makers.

Patricia Reilly, ‘Deputy Chief of Staff (or Deputy Chef de Cabinet) for EU Commissioner for Education Culture, Youth and Sport’ presented the award to Melissa.

FWL-award-Sikosana-2018-2

FWL-award-Sikosana-2018-1

Jean-Michel Romano awarded for his paper at WCMNM2018

JMR_WCMNM2018_awardOn the 20th September 2018, the World Congress on Micro and Nano Manufacturing took place in Portoroz, Slovenia. Jean-Michel Romano, an Early Stage Researcher (ESR) in the Laser4Fun project, was awarded of the Honorable Mention Paper Award for his contribution entitled “Towards large area submicron surface texturing by femtosecond laser irradiation of microparticle arrays”.

The award was presented by the scientific committee chair: Dr. Irene Fassi, National Research Council (CNR), Italy; Dr. Samuel Bigot, Cardiff University, UK; and Prof. Dr. Joško Valentinčič, University of Ljubljana, Slovenia.

WCMNM2018 LogoWCMNM 2018 was jointly organised by the Multi Material Micro Manufacturing association (4M), the International Institution for Micro Manufacturing (I2M2) and the International Forum on Micro Manufacturing (IFMM).