Applied Physics B

, Volume 80, Issue 4, pp 527–534

Fresnel diffraction model for mode-mismatched thermal lens with top-hat beam excitation

Authors

    • Institute of Optics and ElectronicsChinese Academy of Sciences
  • S. Xiong
    • Institute of Optics and ElectronicsChinese Academy of Sciences
  • Y. Zhang
    • Institute of Optics and ElectronicsChinese Academy of Sciences
Article

DOI: 10.1007/s00340-005-1744-2

Cite this article as:
Li, B., Xiong, S. & Zhang, Y. Appl. Phys. B (2005) 80: 527. doi:10.1007/s00340-005-1744-2

Abstract

A theoretical model, based on the Fresnel diffraction integral, is developed to describe the thermal lens (TL) signal in a mode-mismatched collinear configuration, which is optimized for a near field detection scheme and excitation by a cw modulated laser beam with a top-hat profile. The TL amplitudes obtained with both top-hat and Gaussian beam excitations are numerically computed and compared, and the dependence of the TL amplitude on the experimental parameters is discussed. Numerical results show that the top-hat beam TL instrument is more sensitive than the Gaussian beam TL instrument, with a potential doubling of the sensitivity. The use of the top-hat beam excitation with TL detection is a significant improvement because a top-hat beam can be easily obtained with a low-cost, wide-spectral emission white-light source. The use of incoherent light sources as the excitation sources would substantially expand the applicability of the TL technique to the general area of chemical analysis.

PACS

42.25.Fx78.20.Nv

Copyright information

© Springer-Verlag 2005