Beam expander
Optical devices treating collimated light
title: "Beam expander" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["optical-devices", "laser-science"] description: "Optical devices treating collimated light" topic_path: "general/optical-devices" source: "https://en.wikipedia.org/wiki/Beam_expander" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0
::summary Optical devices treating collimated light ::
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. |last1=Duarte |first1=F. J. |author-link=F. J. Duarte |editor1-last=Duarte |editor1-first=F. J. |editor2-last=Hillman |editor2-first=L. W. |year=1990 |chapter=Narrow-linewidth pulsed dye Laser oscillators |title=Dye Laser Principles |publisher=Academic Press |isbn=978-0-12-222700-4
In tunable laser resonators intracavity beam expansion usually illuminates the whole width of a diffraction grating. |last=Hänsch |first=T. W. |author-link=Theodor W. Hänsch |year=1972 |title=Repetitively pulsed tunable dye laser for high resolution spectroscopy |journal=Applied Optics |volume=11 |issue=4 |pages=895–898 |bibcode= 1972ApOpt..11..895H |doi=10.1364/AO.11.000895 |pmid=20119064 |url=http://nbn-resolving.de/urn:nbn:de:bvb:12-bsb00059107-4|url-access=subscription}} Thus beam expansion reduces the beam divergence and enables the emission of very narrow linewidths which is a desired feature for many analytical applications including laser spectroscopy. |last=Demtröder |first=W. |author-link=Wolfgang Demtröder |year=2007 |title=Laserspektroscopie: Grundlagen und Techniken |edition=5th |publisher=Springer |isbn=978-3-540-33792-8 |language=de}} |last=Demtröder |first=W. |year=2008 |title=Laser Spectroscopy Volume 1: Basic Principles |edition=4th |publisher=Springer |isbn=978-3-540-73415-4
Multiple-prism beam expanders
::figure[src="https://upload.wikimedia.org/wikipedia/commons/8/85/Duarte's_multiple-prism_grating_laser_oscillator.png" caption="Long-pulse tunable laser oscillator utilizing a multiple-prism beam expander"] ::
|last1=Duarte |first1=Francisco J. |last2=Taylor |first2=Travis S. |last3=Costela |first3=Angel |last4=Garcia-Moreno |first4=Inmaculada |last5=Sastre |first5=Roberto |year=1998 |title=Long-pulse narrow-linewidth dispersive solid-state dye-laser oscillator |journal=Applied Optics |volume=37 |issue=18 |pages=3987–3989 |doi=10.1364/ao.37.003987 |pmid=18273368 |bibcode=1998ApOpt..37.3987D
Isaac Newton was the first to describe the use of prisms as beam expanders and in multiple-prism arrays. Multiple-prism beam expanders usually deploy two to five prisms to yield large one-dimensional beam expansion factors. Designs applicable to tunable lasers with beam expansion factors of up to 200 have been disclosed in the literature. |last=Duarte |first=F. J. |year=2015 |title= Tunable Laser Optics |url=http://www.tunablelaseroptics.com |edition= 2nd |publisher=CRC Press |isbn= 978-1-4822-4529-5 |last1=Duarte |first1=F. J. |last2=Piper |first2=J. |year=1980 |title=A double-prism beam expander for pulsed dye lasers |journal=Optics Communications |volume=35 |issue=1 |pages=100–104 |bibcode= 1980OptCo..35..100D |doi=10.1016/0030-4018(80)90368-5 |last1=Duarte |first1=F. J. |last2=Piper |first2=J. |year=1982 |title=Dispersion theory of multiple-prism beam expanders for pulsed dye lasers |journal=Optics Communications |volume=43 |issue=5|pages=303–307 |bibcode= 1982OptCo..43..303D |doi=10.1016/0030-4018(82)90216-4
Multiple-prism beam expanders and arrays can also be described using ray transfer matrices. |last1=Duarte |first1=F. J. |year=1989 |title=Ray transfer matrix analysis of multiple-prism dye laser oscillators |journal=Optical and Quantum Electronics |volume=21 |issue=1 |pages=47–54 |doi= 10.1007/BF02199466 |bibcode=1989OQEle..21...47D |s2cid=122811020 |last1=Duarte |first1=F. J. |year=1992 |title=Multiple-prism dispersion and 4×4 ray transfer matrices |journal=Optical and Quantum Electronics |volume=24 |issue=1 |pages=49–53 |doi= 10.1007/BF01234278 |bibcode=1992OQEle..24...49D |s2cid=121055172
Extra-cavity beam shaping
Extra cavity hybrid beam transformers: using a telescopic beam expander, followed by a convex lens, followed by a multiple-prism beam expander, a laser beam (with a circular cross section) can be transformed into an extremely elongated beam, in the plane of propagation, while extremely thin in the orthogonal plane. |last=Duarte |first=F. J. |year=1991 |chapter=Chapter 2 |title=High Power Dye Lasers |publisher=Springer-Verlag |isbn=978-0-387-54066-5
References
References
- Duarte, F. J.. (2000-05-01). "Newton, Prisms, and the “Opticals” of Tunable Lasers". Optics and Photonics News.
- Duarte, Frank J.. (2003). "Tunable Laser Optics". Elsevier Academic Press.
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