Optimization of the volume ablation rate for metals at different laser pulse-durations from ps to fs

Ultra short laser pulses in the ps or fs regime are used, when high requirements concerning machining quality are demanded. However, beside the quality also the process efficiency denotes a key factor for the successful transfer of this technology into real industrial applications. Based on the ablation law, holding for ultra short pulses with moderate fluences, it has been shown that the volume ablation rate can be maximized with an optimum setting of the laser parameters. The value of this maximum depends on the threshold fluence and the energy penetration depth. Both measures themselves depend on the pulse duration. For metals the dependence of the threshold fluence is well known, it stays almost constant for pulse durations up to about 10 ps and begin then to slightly increase with the pulse duration. The contrary behavior is observed for the energy penetration depth, it decreases over the whole range when the pulse duration is raised from 500 fs to 50 ps. In this paper we will show that the maximum ablation rate can therefore be increased by a factor of 1.5 to 2 when the pulse duration is reduced from 10 ps down to 500 fs.

[1]  J. Bonse,et al.  Ultrashort-pulse laser ablation of indium phosphide in air , 2001 .

[2]  Wolfgang Schulz,et al.  Laser machining by short and ultrashort pulses, state of the art , 2002 .

[3]  Beat Neuenschwander,et al.  Laser microstructuring and processing in printing industry , 2011, CLEO: 2011 - Laser Science to Photonic Applications.

[4]  Michael F. Becker,et al.  Laser-induced damage on single-crystal metal surfaces , 1988 .

[5]  Vitali I. Konov,et al.  Micromachining with ultrashort laser pulses: from basic understanding to technical applications , 2003, Advanced Laser Technologies.

[6]  Andreas Ruf,et al.  Fundamental aspects in machining of metals with short and ultrashort laser pulses , 2004, SPIE LASE.

[7]  Boris N. Chichkov,et al.  Short-pulse laser ablation of solid targets , 1996 .

[8]  Reinhart Poprawe,et al.  1100 W Yb:YAG femtosecond Innoslab amplifier , 2011, LASE.

[9]  Beat Neuenschwander,et al.  Processing of industrially relevant non metals with laser pulses in the range between 10ps and 50ps , 2011 .

[10]  Beat Neuenschwander,et al.  Processing of dielectric materials and metals with PS laserpulses , 2010 .

[11]  Gerard M. O'Connor,et al.  Ablation thresholds in ultrafast laser micromachining of common metals in air , 2003, SPIE OPTO-Ireland.

[12]  Baerbel Rethfeld,et al.  Theory of ultrashort laser pulse interaction with a metal , 1997, Other Conferences.

[13]  T. Glynn,et al.  The effect of damage accumulation behaviour on ablation thresholds and damage morphology in ultrafast laser micro-machining of common metals in air , 2004 .

[14]  A. Tünnermann,et al.  Femtosecond, picosecond and nanosecond laser ablation of solids , 1996 .

[15]  M. Gedvilas,et al.  Use of High Repetition Rate and High Power Lasers in Microfabrication: How to Keep the Efficiency High? , 2009 .

[16]  Valerio Romano,et al.  Processing of metals with ps-laser pulses in the range between 10ps and 100ps , 2011, LASE.

[17]  A. Semerok,et al.  Femtosecond and picosecond laser microablation: ablation efficiency and laser microplasma expansion , 1999 .

[18]  H. Hoffmann,et al.  Compact diode-pumped 1.1 kW Yb:YAG Innoslab femtosecond amplifier. , 2010, Optics letters.

[19]  B. Neuenschwander,et al.  Influence of the Pulse Duration in the ps-Regime on the Ablation Efficiency of Metals , 2011 .

[20]  François Salin,et al.  High-power all fiber picosecond sources from IR to UV , 2011, LASE.

[21]  Boris N. Chichkov,et al.  Precise laser ablation with ultrashort pulses , 1997 .

[22]  P. A. Atanasov,et al.  Ablation of metals by ultrashort laser pulses , 2004 .

[23]  Razvan Stoian,et al.  Ultrashort-laser-pulse damage threshold of transparent materials and the role of incubation , 1999 .

[24]  P. Balling,et al.  Short-pulse ablation rates and the two-temperature model , 2007 .

[25]  Pascal Deladurantaye,et al.  Material micromachining using bursts of high repetition rate picosecond pulses from a fiber laser source , 2011, LASE.

[26]  Dietmar Kracht,et al.  All-fiber based amplification of 40 ps pulses from a gain-switched laser diode. , 2011, Optics express.

[27]  B. Chimier,et al.  Surface Ablation of Dielectrics with sub-10 fs to 300 fs Laser Pulses: Crater Depth and Diameter, and Efficiency as a Function of Laser Intensity , 2010 .

[28]  Eric Audouard,et al.  Pulse width and energy influence on laser micromachining of metals in a range of 100 fs to 5 ps , 2005 .