Journal article
(Online publication)


Practical Aspects of Surface Generated Third Harmonic for Highly Precise Beam-workpiece Alignment


Publication Details
Author(s): Cvecek K, Strauß J, Alexeev I, Miyamoto I, Schmidt M
Publisher: Japan Laser Processing Society (JLPS)
Publication year: 2013
Volume: 8
Journal issue: 3
Pages range: 201-205
ISSN: 1880-0688
Language: English

Abstract

Precise beam-workpiece alignment is highly important in laser processing. Though many methods exist for this task few allow high-precision measurements using the processing laser itself. One such method detects the laser’s backreflection from the workpiece’s surface using a confocal setup and yields ideally an accuracy of about 10% of the Rayleigh length of the focused beam. Nevertheless, under certain conditions the accuracy of this method may suffer from a mismatch of beam divergences between laser and confocal detection optics. This becomes important when transparent materials are processed in three dimensions using optics with very high numerical apertures or if expensive materials or samples have to be processed where any misalignment would be costly. A possible solution to this is surface based third harmonic generation that allows for absolute surface detection while having the same accuracy as the confocal method. However, this method requires a complex setup while exhibiting low conversion efficiency. Both reasons make a proper alignment of this measurement scheme difficult. Herein we present results showing a clear conversion efficiency dependence on the reflection coefficient of the generating interface for a number of material combinations. This makes the selection of suitable materials more straightforward and reduces the alignment effort. The highest conversion efficiency was achieved for air/silicon which exhibits the highest reflection coefficient of the investigated materials.



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How to cite
APA: Cvecek, K., Strauß, J., Alexeev, I., Miyamoto, I., & Schmidt, M. (2013). Practical Aspects of Surface Generated Third Harmonic for Highly Precise Beam-workpiece Alignment. Journal of Laser Micro Nanoengineering, 8(3), 201-205. https://dx.doi.org/10.2961/jlmn.2013.03.0003

MLA: Cvecek, Kristian, et al. "Practical Aspects of Surface Generated Third Harmonic for Highly Precise Beam-workpiece Alignment." Journal of Laser Micro Nanoengineering 8.3 (2013): 201-205.

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