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A Novel Method for Characterizing Laser Beams Diverging with High Numerical Apertures (NA) by Means of Optical Fibre Tips
H. Buse, S. Ernst, R.M. Parkin and H. Kreitlow

It is especially necessary in the field of laser direct writing lithography to gain exact knowledge about the shape and characteristics of the utilized laser beam, whilst a homogeneous power distribution is an essential parameter for sufficient and reproducible results in surface structuring. A novel method is presented to characterize the power distribution of a focused laser beam by scanning its cross-sectional plane with an optical fibre tip that is commonly used for scanning near field optical microscopy (SNOM). This novel method is capable of characterizing laser beams diverging from very small focal apertures with a high resolution. This method can improve the research and development (R&D) of either an academic institute or a player in the optical industry regarding such things as the development of the next generation of optical storage. In contrast to the established profiling techniques and commercial products, the field of application includes the characterization of beams diverging from the lenses of DVD or BluRay© devices with numerical apertures (NA) in the range of 0.6 up to 0.85. Laser beams emerging from modified optical pickup units (OPU) have been successfully characterized using this novel method.

Keywords: Laser beam, numerical aperture (NA), optical fibre tips, near field, far field, focus, focal plane

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