Applied Physics B

, Volume 70, Issue 4, pp 593–599

A ray-optic, Monte Carlo, description of a Gaussian beam waist – applied to reverse saturable absorption

  • P.K. Milsom

DOI: 10.1007/s003400050867

Cite this article as:
Milsom, P. Appl Phys B (2000) 70: 593. doi:10.1007/s003400050867


The intensity distribution in a Gaussian beam is represented by a bundle of rays in which each ray has a random pointing error. The ray bundle is allowed to pass through a simple lens using the usual geometrical optics formulae and it is shown that the position of the focused beam waist agrees exactly with the usual Gaussian mode analysis. The interaction of the beam waist with a reverse saturable absorber (silicon napthalocyanaine) is modelled using a Monte Carlo method and a null absorption coefficient is introduced to increase the speed of the calculation. An f/5 geometry is considered and it is shown that the results from the ray model agree well with those obtained from standard split-step beam propagation techniques.

PACS: 42.25.Bs; 42.65; 42.55Ah

Copyright information

© Springer-Verlag 2000

Authors and Affiliations

  • P.K. Milsom
    • 1
  1. 1.DERA, St. Andrews Road, Great Malvern WR14 3PS, UK (Fax: +44-1684/896-940, E-mail: