Digital Micromirror Devices for rapid fabrication of largearea

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

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

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 (>30 k. Hz) Schematic of a section of the digital mirror device (actual model used: Texas Instruments DLP 3000, 608 x 684 mirrors) 3

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

Sample fabrication schematic • Each laser pulse is shaped to a different pattern • The sample is continuously translated ut inp lses pu r e as l sp at las ially er pu shap lse e s d sample is continuously translated foc ob ussin jec tiv g e 5 sample movement direction array of mirrors, showing the pattern (the DMD)

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

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

Security and marking applications 3 mm 1 mm 8

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

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/L 022230/1) 10