Beam expander: Difference between revisions
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'''Beam expanders''' are used in [[laser physics]] 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. |
'''Beam expanders''' are used in [[laser physics]] 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. |
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Telescopic beam expanders include [[refracting_telescope|refracting]] and [[reflective telescope]]s.<ref name="Duarte_DLP"> |
Telescopic beam expanders include [[refracting_telescope|refracting]] and [[reflective telescope]]s.<ref name="Duarte_DLP"> |
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{{cite book |
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|last1=Duarte |first1=F. J. |authorlink=F. J. Duarte |
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|editor1-last=Duarte |editor1-first=F. J. |
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|editor2-last=Hillman |editor2-first=L. W. |
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|year=1990 |
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|chapter=Narrow-linewidth pulsed dye Laser oscillators |
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|title=Dye Laser Principles |
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|publisher=[[Academic Press]] |
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|isbn=0-12-222700-X |
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}}</ref> A refracting telescope commonly used is the [[Refracting_telescope#Galileo's telescope|Galilean telescope]] which can function as a simple beam expander for [[collimated]] light. When used as intracavity beam expanders, in laser resonators, these telescopes provide two-dimensional beam expansion in the 20–50 range.<ref name="Duarte_DLP"/> |
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In [[tunable laser]] resonators intracavity beam expansion usually illuminates the whole width of a [[diffraction grating]].<ref> |
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In [[tunable laser]] resonators intracavity beam expansion usually illuminates the whole width of a [[diffraction grating]].<ref>[[Theodor W. Hänsch|T. W. Hänsch]], Repetitively pulsed tunable dye laser for high resolution spectroscopy, ''Appl. Opt.'' '''11''', 895-898 (1972).</ref> Thus beam expansion reduces the beam divergence and enables the emission of very narrow linewidths<ref name="Duarte_TLO"/> which is a desired feature for many analytical applications including laser spectroscopy.<ref>[[W. Demtröder]], ''Laserspektroscopie: Grundlagen und Techniken'', 5th Ed. (Springer, Berlin, 2007) Chapter 5.</ref><ref>W. Demtröder, ''Laser Spectroscopy: Basic Principles'', 4th Ed. (Springer, Berlin, 2008). </ref> |
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{{cite journal |
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|last=Hänsch |first=T. W. |authorlink=Theodor W. Hänsch |
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|year=1972 |
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|title=Repetitively pulsed tunable dye laser for high resolution spectroscopy |
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|journal=[[Applied Optics]] |
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|volume=11 |issue= |pages=895-898 |
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|arxiv= |
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|bibcode= |
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|doi= |
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}}</ref> Thus beam expansion reduces the beam divergence and enables the emission of very narrow linewidths<ref name="Duarte_TLO"/> which is a desired feature for many analytical applications including laser spectroscopy.<ref> |
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{{cite book |
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|last=Demtröder |first=W. |authorlink=Wolfgang Demtröder |
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|year=2007 |
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|title=Laserspektroscopie: Grundlagen und Techniken |
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|edition=5th |
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|publisher=[[Springer (publisher)|Springer]] |
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|isbn= |
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}} {{De icon}}</ref><ref> |
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{{cite book |
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|last=Demtröder |first=W. |
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|year=2008 |
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|title=Laser Spectroscopy: Basic Principles |
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|edition=4th |
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|publisher=[[Springer (publisher)|Springer]] |
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|isbn= |
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}}</ref> |
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== Multiple-prism beam expanders == |
== Multiple-prism beam expanders == |
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Revision as of 01:47, 11 September 2011
Beam expanders are used in laser physics 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. 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]
Multiple-prism beam expanders
Multiple-prism beam expanders usually deploy two to five prism 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.[3] Initially multiple-prism grating configurations were introduced in narrow-linewidth liquid dye lasers[1][6] but eventually were also adopted in gas, solid-state, and diode laser designs.[3] The generalized mathematical description of multiple-prism beam expanders, introduced by Duarte,[7] is known as the multiple-prism dispersion theory.[1][3]
Multiple-prism beam expanders and arrays can also be described using ray transfer matrices.[8] The multiple-prism dispersion theory is also available in 4 X 4 matrix form.[3][9] These matrix equations are applicable either to prism pulse compressors or multiple-prism beam expanders.[3]
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.[3][10] The resulting one-dimensional (or line) illumination eliminates the need of point-by-point scanning and has become important for applications such as N-slit interferometry, microdensitometry and microscopy.
See also
- Multiple-prism dispersion theory
- Multiple-prism grating laser oscillators
- N-Slit interferometer
- Ray transfer matrix analysis
References
- ^ a b c d Duarte, F. J. (1990). "Narrow-linewidth pulsed dye Laser oscillators". In Duarte, F. J.; Hillman, L. W. (eds.). Dye Laser Principles. Academic Press. ISBN 0-12-222700-X.
- ^ Hänsch, T. W. (1972). "Repetitively pulsed tunable dye laser for high resolution spectroscopy". Applied Optics. 11: 895–898.
- ^ a b c d e f g F. J. Duarte, Tunable Laser Optics (Elsevier-Academic, New York, 2003) ISBN 0-12-222696-8.
- ^ Demtröder, W. (2007). Laserspektroscopie: Grundlagen und Techniken (5th ed.). Springer. Template:De icon
- ^ Demtröder, W. (2008). Laser Spectroscopy: Basic Principles (4th ed.). Springer.
- ^ F. J. Duarte and J. A. Piper, A double-prism beam expander for pulsed dye lasers, Opt. Commun. 35, 100-104 (1980).
- ^ F. J. Duarte and J. A. Piper, Dispersion theory of multiple-prism beam expanders for pulsed dye lasers, Opt. Commun. 43, 303–307 (1982).
- ^ F. J. Duarte, Ray transfer matrix analysis of multiple-prism dye laser oscillators, Opt. Quantum Electron. 21, 47-54 (1989).
- ^ F. J. Duarte, Multiple-prism dispersion and 4 x 4 ray transfer matrices, Opt. Quantum Electron. 24, 49-53 (1992).
- ^ F. J. Duarte, in High Power Dye Lasers (Springer-Verlag, Berlin,1991) Chapter 2.
External links
- References on prism arrays and prism beam expanders.
- Schematics of practical multiple-prism arrangements.
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