Beam shaping and power handling of an SLM system for LIPSS texturationThursday (25.06.2020) 10:50 - 11:10 Room 3
Laser Induced Surface Periodic Surface texturing is a powerful tool for creating sub-micrometric features on large surfaces in an up-scalable and industrial way . In order to control the process and reach a sufficient uniformity for some applications a careful attention must be paid to the control of the laser beam parameters like its polarization , stability and shape. A uniform beam shape is mandatory in some cases. The orientation of the polarization can be also required for reaching given functionalities and even polarization modification during the process can be desired for orientating the LIPSS patterns.
Beam shaping can be achieved with classical diffractive optical elements in order for instance to get a uniform top-hat shape. This is a robust and cos-effective solution that suffers only one drawback which is its non-reconfigurable mode of operation.
Regarding this aspect, spatial light modulators provide much more flexibility but are more limited in terms of power and energy handling. Although some demonstrations of high power handling have been made , there is not much reported regarding the use of SLM for beam shaping of ultrashort pulses.
In the current work we show the possibility to use SLM with different type of laser sources, including a femtosecond system delivering up to 1 mJ per pulses.
The SLM module was packaged in water-cooling system for enhancing its range of operation. We used a spatial light modulator from the company HoloEye. The PLUTO-2 device is a reflective LCOS PAN (Parallel Aligned Nematic)-SLM that allows for pure phase modulation. It has an array of 1920 x 1080.
In CW mode the device was tested with more than 100W at 1064nm, but for pulsed applications, with high peak powers, one needs to be careful especially if the beam diameter is very small and average power density is quite high > 50W/cm². Based on this water-cooled holder we were able to demonstrate power handling larger that 20 W average power in nanosecond regime and up to 1 mJ at 500 fs without observed degradation.
A square beam shape obtained with the SLM in femtosecond regime is shown together to the result obtained (right) when this laser beam is applied on INOX: homogeneous LIPSS over the whole laser beam was obtained.
The global system permits both polarization and beam shape control for producing homogeneous LIPSS patterns in a dynamically reconfigurable way.
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