Beam expander

Beam expanders are optical devices that take a collimated beam of light and expand its width (or, used in reverse, reduce its width).

In laser physics they are used either as intracavity or extracavity elements. They can be telescopic in nature or prismatic. Generally prismatic beam expanders use several prisms and are known as multiple-prism beam expanders.

Telescopic beam expanders include refracting and reflective telescopes.[1] A refracting telescope commonly used is the Galilean telescope which can function as a simple beam expander for collimated light. The main advantage of the Galilean design is that it never focuses a collimated beam to a point, so effects associated with high power density such as dielectric breakdown are more avoidable than with focusing designs such as the Keplerian telescope. When used as intracavity beam expanders, in laser resonators, these telescopes provide two-dimensional beam expansion in the 20–50 range.[1]

In tunable laser resonators intracavity beam expansion usually illuminates the whole width of a diffraction grating.[2] Thus beam expansion reduces the beam divergence and enables the emission of very narrow linewidths[3] which is a desired feature for many analytical applications including laser spectroscopy.[4][5]

  1. ^ a b Duarte, F. J. (1990). "Narrow-linewidth pulsed dye Laser oscillators". In Duarte, F. J.; Hillman, L. W. (eds.). Dye Laser Principles. Academic Press. ISBN 978-0-12-222700-4.
  2. ^ Hänsch, T. W. (1972). "Repetitively pulsed tunable dye laser for high resolution spectroscopy". Applied Optics. 11 (4): 895–898. Bibcode:1972ApOpt..11..895H. doi:10.1364/AO.11.000895. PMID 20119064.
  3. ^ Cite error: The named reference Duarte_TLO was invoked but never defined (see the help page).
  4. ^ Demtröder, W. (2007). Laserspektroscopie: Grundlagen und Techniken (in German) (5th ed.). Springer. ISBN 978-3-540-33792-8.
  5. ^ Demtröder, W. (2008). Laser Spectroscopy Volume 1: Basic Principles (4th ed.). Springer. ISBN 978-3-540-73415-4.