1. Digital Micromirror Devices for rapid fabrication of large-area laser- ablated multicolour-grating patterns B. Mills, D. J. Heath, M. Feinaeugle, R. W. Eason Optoelectronics Research Centre, University of Southampton, UK

2. 2 Outline Introduction to digital mirror devices (DMD) Using a DMD for laser-ablation Fabrication of multi-colour surfaces Replication of a Morpho butterfly Conclusions

3. 3 Digital Mirror Device (DMD) Used in majority of projectors Array of individually controlled ~10μm width mirrors Can be used as an intensity spatial light modulator (SLM) Fast switching speed (>30kHz) Schematic of a section of the digital mirror device (actual model used: Texas Instruments DLP3000, 608 x 684 mirrors)

4. 4 Energy density on sample is 1-50J/cm 2 Energy density on DMD is ~1mJ/cm 2 Well below damage threshold of DMD due to magnification Experimental schematic

5. Sample fabrication schematic 5 Each laser pulse is shaped to a different pattern The sample is continuously translated input laser pulses  array of mirrors, showing the pattern (the DMD) focussing objective spatially-shaped laser pulses  sample is continuously translated sample movement direction 

6. Process repeated to make 2D arrays 6 direction of  stage movement After each line of letters, we start again on an adjacent line, to build up 2D arrays 50µm 10µm

7. Not letters but gratings, where each grating can have a different period 7 Each grating is 30 by 30µm and will diffract different colours of light to different angles We build up an array of 10,000s, over cm-squared regions Result is that the material surface appears to be coloured 10µm 50µm

8. Security and marking applications 8 1mm 3mm

9. Replication of a Morpho butterfly 9 Nature Fabricated SEM image Photograph 1µm 10µm 2mm

10. Conclusions Fabrication of cm-squared regions in 15 minutes (with faster stages  less than 1 minute) Diffraction-limited writing resolution Can be used to make a surface appear to be multi-coloured Applications in security / marking This work was supported under EPSRC (grant number EP/L022230/1) 10