Characterization and preparation of focused laser beams

Martin Kauert; Martin Frenz; Jaroslav Ricka

doi:10.1117/1.2835692

1 January 2008 Characterization and preparation of focused laser beams

Martin Kauert, Martin Frenz, Jaroslav Ricka

Author Affiliations +

Optical Engineering, Vol. 47, Issue 1, 014201 (January 2008). https://doi.org/10.1117/1.2835692

Abstract

We discuss the possibilities of a far-field beam profiling technique for the determination of the near-focal profiles of laser beams focused beyond the paraxial approximation. The analysis is based on the rigorous vectorial Fourier synthesis of the fields and includes polarization effects. The wave-vector distribution can be calculated either a priori using the radius of the impinging laser beam and the data of the objective, or by obtaining its parameters from profiling at different z positions far behind the objective. For such measurements we designed a profiling system suitable for in situ application in microscopy. The device consists of a fiber optic taper bonded onto the chip of a CMOS camera, allowing taking pictures in the working medium in planes sufficiently close to the focus. The near-focal profiles obtained by these two approaches show good agreement, but only if the measured effective numerical aperture NA_eff is used. We have further readdressed the effect of filling the objective pupil on the near-focal fields. The small improvement in focusing by the commonly practiced overfilling is hardly worth the significant loss of power. Moreover, overfilling above an optimal beam radius a_opt results in an increase of aberrations when focusing through an optical interface.

©(2008) Society of Photo-Optical Instrumentation Engineers (SPIE)

Citation Download Citation

Martin Kauert, Martin Frenz, and Jaroslav Ricka "Characterization and preparation of focused laser beams," Optical Engineering 47(1), 014201 (1 January 2008). https://doi.org/10.1117/1.2835692

Published: 1 January 2008

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