Australian Optical Society

Thermal Modeling of Laser Removal of Optics and Photonics Mountants

D M Kane and D Hirschausen

Dept. of Physics, Macquarie University, Sydney, NSW 2109

Tel: (02) 9850 8907

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Waxes and thermo-polymers are commonly used to mount optical and photonic materials for polishing and singularisation. After demounting, residual wax/thermo-polymer can adhere to the component surface, frequently in the form of particles. Dry, UV-pulsed laser cleaning has been demonstrated to effectively remove paraffin wax particles, prepared on a glass surface using an atomizing technique [1, 2]. This is in keeping with the current belief in the laser cleaning research field that “any laser can be used to remove hydrocarbons”. It is in contrast with experimental results obtained using photonic components, sourced from photonic device production lines, where it is found that some of the mountant residue in the form of particles cannot be laser removed before the threshold for optical damage is reached.

Thermal modeling of the laser removal process has enabled these differing results to be reconciled. The model is based on removal of the paraffin wax/thermo-polymer by vaporization. Good agreement between the theoretically predicted critical fluence for single laser pulse removal of dome-shaped particles and that measured experimentally (~200mJ/cm2) is obtained. Different geometries and relative thermal properties of the “contaminant” and “surface” lead to cases where laser removal of the contaminant is not readily achievable. Thus, determining the reasons for the significantly differing laser cleaning results is of importance. Also, suggestions for the modification of the techniques recommended for the use of the mountant materials to facilitate ease of residue removal after use are proposed.

References

  1. Dry Laser Cleaning of Hydrocarbons from Glass Substrates Using KrF Excimer, D Hirschausen and D M Kane, ACOLS 2001, Brisbane, p100, M10, (2001).
  2. Laser Removal of Paraffin Wax from Glass Surfaces, D Hirschausen and D M Kane, submitted to Journal of Applied Physics.