WO1997008792A1 - Multiple pass optical system - Google Patents

Multiple pass optical system Download PDF

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Publication number
WO1997008792A1
WO1997008792A1 PCT/GB1996/002085 GB9602085W WO9708792A1 WO 1997008792 A1 WO1997008792 A1 WO 1997008792A1 GB 9602085 W GB9602085 W GB 9602085W WO 9708792 A1 WO9708792 A1 WO 9708792A1
Authority
WO
WIPO (PCT)
Prior art keywords
optical elements
elements
refractive
optical system
multiple pass
Prior art date
Application number
PCT/GB1996/002085
Other languages
French (fr)
Inventor
James Martin David Lister
Ian Norman Ross
Original Assignee
Council For The Central Laboratory Of The Research Councils
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Council For The Central Laboratory Of The Research Councils filed Critical Council For The Central Laboratory Of The Research Councils
Publication of WO1997008792A1 publication Critical patent/WO1997008792A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/23—Arrangements of two or more lasers not provided for in groups H01S3/02 - H01S3/22, e.g. tandem arrangements of separate active media
    • H01S3/2308—Amplifier arrangements, e.g. MOPA
    • H01S3/2325—Multi-pass amplifiers, e.g. regenerative amplifiers
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B17/00—Systems with reflecting surfaces, with or without refracting elements
    • G02B17/004—Systems comprising a plurality of reflections between two or more surfaces, e.g. cells, resonators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/094038—End pumping

Definitions

  • the present invention relates to a multiple pass optical system and particularly but not exclusively to a multi-pass laser amplifier.
  • a beam of light be it ultraviolet, optical or infrared
  • Known multi-pass optical systems generally rely on multiple mirrors requiring very careful alignment and are consequently costly, highly complex, permit only narrow bandwidth operation and can be unreliable as a result of the system sensitivity to alignment of the many optical elements.
  • the present invention seeks to overcome the disadvantages with known systems and to provide a simple but effective multiple pass optical system capable of operating with both narrow and broad bandwidths.
  • the present invention provides a multiple pass optical system comprising an opposing pair of reflective optical elements and first and second refractive optical elements located between the reflective optical elements and arranged to direct a beam of light along at least two paths having a common point of intersection, each ofthe paths describing a different azimuth angle with respect to a plane of symmetry containing the axis of the optical system.
  • a beam of light may pass repeatedly through the same spatial point in the optical system along various paths with the light following any one ofthe paths remaining substantially uncoupled from the light following any other of the paths.
  • an amplifier is provided at the common point of intersection.
  • the amplifier may be endpumped by directing pump beams along the optical axis from either end of the system.
  • the reflective optical elements are plane mirrors positioned substantially pe ⁇ endicular to the optical axis ofthe system.
  • the refractive optical elements are double biprism devices.
  • Figure 2 is a perspective beam diagram for an eight pass amplifier in accordance with the present invention.
  • Figure 3 shows in section the eight pass amplifier of Figure 2.
  • the multiple pass optical system shown in Figure 1 includes only two reflecting optical elements 10, 11 at opposing ends ofthe system. No additional reflecting optical elements are required.
  • the reflecting optical elements 10, 11, which preferably are plane mirrors, are parallel to one another and normal to the axis X of the system.
  • the multiple pass optical system also includes two refractive optical elements 12, 13 located between the two mirrors 10, 11 and either side of a common point of intersection Z of the beam path through the system.
  • the two optical elements 12, 13 are purely refractive, have no optical power and are based on the biprism. Where the optical system is being used in combination with an amplifier 14, the amplifier 14 is positioned at the point of intersection Z of the beam paths.
  • the refractive optical elements 12, 13 or biprism elements determine the beam path through the optical system and hence the number of passes through the point of intersection Z between the input and output of the optical system.
  • the biprism elements 12, 13 are arranged so that the beam path does not pass through the axis X ofthe optical system except at the common point of intersection Z.
  • each of the refractive optical elements 12, 13 is a double biprism.
  • the double biprism consists of an orthogonal pair of biprisms having equal angles.
  • the pair of biprisms may be made as a low aspect-ratio pyramid, as two biprisms on opposite faces of the optical element or as four half size biprisms.
  • the double biprisms are positioned either side of the point of intersection Z, within the two mirrors 10, 11, and are mutually orientated azimuthally at 45°.
  • the beam is refracted by the double biprism 12 and is then reflected by the plane mirror 10 to point A which is in the next quadrant ofthe double biprism 12 but is equidistant from the axis X.
  • the beam is again refracted and passes through the amplifier 14 to an equivalent point A on the second of the double biprisms 13.
  • All of the paths followed by the beam between the double biprisms 12, 13 and the point of intersection Z are at a fixed angle to the optical axis X of the system and in consequence the paths lie on the surface of a cone the apex of which is the intersection Z.
  • the points of intersection of the beam with each of the double biprisms describe the apexes of an octagon.
  • the input beam In and the output beam Out are introduced into and emerged from the optical system respectively via a corridor 15 through the second of the double biprisms 13.
  • the corridor 15 is provided by removing an edge portion from the double biprism 13.
  • the resultant output beam is substantially decoupled from the input beam.
  • Figures 2 and 3 the input and output beams In, Out are shown reflected off one of the end mirrors 11.
  • each refractive optical element consists of two double biprisms with all equal angles, mutually orientated at 45°.
  • Each pair of double biprisms has a relative orientation of 22.5°.
  • the numbers of passes in each case may also be doubled by retroreflection.
  • optical system may be operated over a broad range of beam widths.
  • the beam path through the optical system at no time extends along the axis X and only intersects the axis at the common point of intersection Z.
  • an amplifier located at the point of intersection Z can be pumped 16 from both ends through central holes provided in the optical elements of the system, as shown in Figures 2 and 3.
  • a titanium sapphire amplifier 14 is positioned at the point of intersection Z of the beam path.
  • Each ray in this diagram represents two routes between the optical elements and the amplifier 14.
  • the pump beams 16 for the amplifier are shown along the axis of the optical system.
  • this optical system may also be used with flashpumped amplifiers such as a Nd:glass amplifier as well as laser pumped amplifiers like the Ti.sapphire amplifier mentioned above.
  • flashpumped amplifiers such as a Nd:glass amplifier
  • laser pumped amplifiers like the Ti.sapphire amplifier mentioned above.
  • Alternative arrangements of the optical system and in particular different optical elements are envisaged.
  • programmable refractive arrays may be employed and/or alternative refractive elements.
  • the optical elements are arranged so that the beam paths in different passes are angularly multiplexed and spatially overlapped in one plane.

Abstract

A multiple pass optical system has two plane mirrors (10, 11) opposing one another with two biprism elements (12, 13) located in between. The biprism elements (12, 13) are arranged to define in combination with the plane mirrors (10, 11) a plurality of beam paths having a common point of intersection (2). In this way with a minimum number of optical elements a system is provided with angularly multiplexed beam paths which spatially overlap in one plane.

Description

MULTIPLE PASS OPTICAL SYSTEM
The present invention relates to a multiple pass optical system and particularly but not exclusively to a multi-pass laser amplifier. There a number of situations in which it is desirable to pass a beam of light, be it ultraviolet, optical or infrared, through a given device many times and by so doing greatly reduce the cost of the system and increase the space efficiency. In order to do so, however, any tendency for the beam on different passes to become coupled must be minimised. Known multi-pass optical systems generally rely on multiple mirrors requiring very careful alignment and are consequently costly, highly complex, permit only narrow bandwidth operation and can be unreliable as a result of the system sensitivity to alignment of the many optical elements.
The present invention seeks to overcome the disadvantages with known systems and to provide a simple but effective multiple pass optical system capable of operating with both narrow and broad bandwidths. The present invention provides a multiple pass optical system comprising an opposing pair of reflective optical elements and first and second refractive optical elements located between the reflective optical elements and arranged to direct a beam of light along at least two paths having a common point of intersection, each ofthe paths describing a different azimuth angle with respect to a plane of symmetry containing the axis of the optical system.
In this way, with the present invention a beam of light may pass repeatedly through the same spatial point in the optical system along various paths with the light following any one ofthe paths remaining substantially uncoupled from the light following any other of the paths. Preferably, an amplifier is provided at the common point of intersection. Also the amplifier may be endpumped by directing pump beams along the optical axis from either end of the system. Ideally, the reflective optical elements are plane mirrors positioned substantially peφendicular to the optical axis ofthe system. Also, preferably the refractive optical elements are double biprism devices. Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of a multiple pass optical system in accordance with the present invention;
Figure 2 is a perspective beam diagram for an eight pass amplifier in accordance with the present invention; and Figure 3 shows in section the eight pass amplifier of Figure 2.
The multiple pass optical system shown in Figure 1 includes only two reflecting optical elements 10, 11 at opposing ends ofthe system. No additional reflecting optical elements are required. The reflecting optical elements 10, 11, which preferably are plane mirrors, are parallel to one another and normal to the axis X of the system. The multiple pass optical system also includes two refractive optical elements 12, 13 located between the two mirrors 10, 11 and either side of a common point of intersection Z of the beam path through the system. The two optical elements 12, 13 are purely refractive, have no optical power and are based on the biprism. Where the optical system is being used in combination with an amplifier 14, the amplifier 14 is positioned at the point of intersection Z of the beam paths.
The refractive optical elements 12, 13 or biprism elements determine the beam path through the optical system and hence the number of passes through the point of intersection Z between the input and output of the optical system. The biprism elements 12, 13 are arranged so that the beam path does not pass through the axis X ofthe optical system except at the common point of intersection Z.
In Figure 2 the beam path through an eight pass amplifier is shown. To achieve eight passes through the point of intersection Z, each of the refractive optical elements 12, 13 is a double biprism. The double biprism consists of an orthogonal pair of biprisms having equal angles. The pair of biprisms may be made as a low aspect-ratio pyramid, as two biprisms on opposite faces of the optical element or as four half size biprisms. The double biprisms are positioned either side of the point of intersection Z, within the two mirrors 10, 11, and are mutually orientated azimuthally at 45°. A beam In which enters the optical system and passes through the point of intersection Z, at which an amplifier 14 is located, meets the first of the double biprisms 12 at a point H on the double biprism. The beam is refracted by the double biprism 12 and is then reflected by the plane mirror 10 to point A which is in the next quadrant ofthe double biprism 12 but is equidistant from the axis X. The beam is again refracted and passes through the amplifier 14 to an equivalent point A on the second of the double biprisms 13. A similar route is now followed by the beam via the plane mirror 11 , to a point B in an adjacent quadrant of the second of the double biprisms 13 and thence via the amplifier to a point B marked in dotted lines on the first of the double biprisms 12 at an orientation of 90° to point H. This beam path continues in the same manner until after eight passes through the amplifier 14 the beam arrives at a position from which further refraction and reflection would result in the beam rejoining the original path to point H on the first double biprism 12.
All of the paths followed by the beam between the double biprisms 12, 13 and the point of intersection Z are at a fixed angle to the optical axis X of the system and in consequence the paths lie on the surface of a cone the apex of which is the intersection Z. The points of intersection of the beam with each of the double biprisms describe the apexes of an octagon.
The input beam In and the output beam Out are introduced into and emerged from the optical system respectively via a corridor 15 through the second of the double biprisms 13. In its simplest form the corridor 15 is provided by removing an edge portion from the double biprism 13. The resultant output beam is substantially decoupled from the input beam. In Figures 2 and 3 the input and output beams In, Out are shown reflected off one of the end mirrors 11.
By appropriate selection ofthe refractive optical elements 12, 13 different numbers of passes through the optical system may be achieved. For example, for a sixteen pass system, each refractive optical element consists of two double biprisms with all equal angles, mutually orientated at 45°. Each pair of double biprisms has a relative orientation of 22.5°. The numbers of passes in each case may also be doubled by retroreflection. With the optical system described the alignment of the two end mirrors is straightforward and the only critical adjustment is the tilt of the mirrors. It will be apparent that the number of optical elements has been reduced in comparison to conventional systems and the number of mirrors, in particular, minimised. This enables a more efficient use of space and maximises the bandwidth with which the system can be operated.
Furthermore the optical system may be operated over a broad range of beam widths.
In addition, unlike known systems, the beam path through the optical system at no time extends along the axis X and only intersects the axis at the common point of intersection Z. This means that an amplifier located at the point of intersection Z can be pumped 16 from both ends through central holes provided in the optical elements of the system, as shown in Figures 2 and 3.
In Figure 3 a titanium sapphire amplifier 14 is positioned at the point of intersection Z of the beam path. Each ray in this diagram represents two routes between the optical elements and the amplifier 14. The pump beams 16 for the amplifier are shown along the axis of the optical system. Unlike other known systems this optical system may also be used with flashpumped amplifiers such as a Nd:glass amplifier as well as laser pumped amplifiers like the Ti.sapphire amplifier mentioned above. Alternative arrangements of the optical system and in particular different optical elements are envisaged. For, example, instead of biprisms programmable refractive arrays may be employed and/or alternative refractive elements. In all cases, however, the optical elements are arranged so that the beam paths in different passes are angularly multiplexed and spatially overlapped in one plane.

Claims

1. A multiple pass optical system comprising an opposing pair of reflective optical elements and first and second refractive optical elements located between the reflective optical elements and arranged to direct a beam of light along at least two paths having a common point of intersection, each ofthe paths describing a different azimuth angle with respect to a plane of symmetry containing the axis ofthe optical system.
2. A multiple pass optical system comprising first and second refractive optical elements positioned either side of a common point of intersection of beam paths and only two reflective optical elements located outside of the first and second refractive optical elements and opposing each other, each of the refractive optical elements having a plurality of refractive sectors with each sector defining in combination with one of the reflective optical elements a respective beam path, with the beam paths of all the sectors of each of the refractive optical elements lying on the surface of a cone the apex of which is the common point of intersection.
3. A multiple pass optical system as claimed in either of claims 1 or 2, wherein the reflective optical elements are plane mirrors arranged normal to the optical axis of the system.
4. A multiple pass optical system as claimed in any one of claims 1 to 3, wherein the first and second refractive optical elements are purely refractive.
5. A multiple pass optical system as claimed in claim 4, wherein the first and second refractive optical elements are first and second biprism elements.
6. A multiple pass optical system as claimed in claim 5, wherein each of the first and second biprism elements comprises an orthogonal pair of biprisms having equal angles, with the first and second biprism elements being mutually orientated azimuthally at 45° thereby defining eight substantially uncoupled beam path passes through the system.
7. A multiple pass optical system as claimed in any one of claims
1 to 6, wherein there is further provided an output corridor through the second refractive optical element in the form of a cut away portion.
8. A multiple pass optical system as claimed in any one of claims
1 to 7, wherein there is further provided an amplifier at the common point of intersection.
9. A multiple pass optical system as claimed in claim 8, wherein apertures are provided in the reflective optical elements and the refractive optical elements along the optical axis of the system whereby pump beams may be directed along the optical axis of the system to the amplifier.
PCT/GB1996/002085 1995-08-31 1996-08-27 Multiple pass optical system WO1997008792A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB9517755.6A GB9517755D0 (en) 1995-08-31 1995-08-31 Multiple pass optical system
GB9517755.6 1995-08-31

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WO1997008792A1 true WO1997008792A1 (en) 1997-03-06

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Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2315549A (en) * 1996-07-23 1998-02-04 Thomson Csf Measuring the alignment of a laser amplification system
EP1059708A1 (en) * 1998-11-10 2000-12-13 Tokyo Denshi Kabushiki Kaisha Apparatus for photoreaction
US6771683B2 (en) * 2000-10-26 2004-08-03 Coherent, Inc. Intra-cavity beam homogenizer resonator
US7630424B2 (en) 2005-11-01 2009-12-08 Cymer, Inc. Laser system
US7643529B2 (en) 2005-11-01 2010-01-05 Cymer, Inc. Laser system
US7715459B2 (en) 2005-11-01 2010-05-11 Cymer, Inc. Laser system
US7746913B2 (en) 2005-11-01 2010-06-29 Cymer, Inc. Laser system
US7778302B2 (en) 2005-11-01 2010-08-17 Cymer, Inc. Laser system
US7822092B2 (en) 2005-11-01 2010-10-26 Cymer, Inc. Laser system
US7885309B2 (en) 2005-11-01 2011-02-08 Cymer, Inc. Laser system
US7920616B2 (en) 2005-11-01 2011-04-05 Cymer, Inc. Laser system
US7999915B2 (en) 2005-11-01 2011-08-16 Cymer, Inc. Laser system
CN112018589A (en) * 2019-05-28 2020-12-01 天津凯普林激光科技有限公司 Laser amplification device and laser amplification method
WO2022084233A1 (en) * 2020-10-23 2022-04-28 Coherent Kaiserslautern GmbH Multipass laser amplifier and no-optical-power beam steering element

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DE3036656A1 (en) * 1980-09-29 1982-05-13 Siemens AG, 1000 Berlin und 8000 München Combined lens and reflector system - for multi:path spectroscopic or photochemical processes with low absorption gases

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Title
MING LAI ET AL: "TRANSVERSELY PUMPED 11-PASS AMPLIFIER FOR FEMTOSECOND OPTICAL PULSES", APPLIED OPTICS, vol. 30, no. 30, 20 October 1991 (1991-10-20), pages 4365 - 4367, XP000235547 *
OLSON T E ET AL: "MULTIPASS DIODE-PUMPED ND:YAG OPTICAL AMPLIFIERS AT 1.06 MUM AND 1.32 MUM", IEEE PHOTONICS TECHNOLOGY LETTERS, vol. 6, no. 5, 1 May 1994 (1994-05-01), pages 605 - 608, XP000446972 *
PLAESSMANN H ET AL: "Multipass diode-pumped solid-state optical amplifier", OPTICS LETTERS, 1 SEPT. 1993, USA, vol. 18, no. 17, ISSN 0146-9592, pages 1420 - 1422, XP000388158 *

Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2315549A (en) * 1996-07-23 1998-02-04 Thomson Csf Measuring the alignment of a laser amplification system
GB2315549B (en) * 1996-07-23 2000-06-14 Thomson Csf A device to measure the alignment of a laser amplification system
EP1059708A1 (en) * 1998-11-10 2000-12-13 Tokyo Denshi Kabushiki Kaisha Apparatus for photoreaction
EP1059708A4 (en) * 1998-11-10 2005-05-25 Idx Technologies Kk Apparatus for photoreaction
US6771683B2 (en) * 2000-10-26 2004-08-03 Coherent, Inc. Intra-cavity beam homogenizer resonator
US7822092B2 (en) 2005-11-01 2010-10-26 Cymer, Inc. Laser system
US7920616B2 (en) 2005-11-01 2011-04-05 Cymer, Inc. Laser system
US7715459B2 (en) 2005-11-01 2010-05-11 Cymer, Inc. Laser system
US7746913B2 (en) 2005-11-01 2010-06-29 Cymer, Inc. Laser system
US7778302B2 (en) 2005-11-01 2010-08-17 Cymer, Inc. Laser system
US7630424B2 (en) 2005-11-01 2009-12-08 Cymer, Inc. Laser system
US7885309B2 (en) 2005-11-01 2011-02-08 Cymer, Inc. Laser system
US7643529B2 (en) 2005-11-01 2010-01-05 Cymer, Inc. Laser system
US7999915B2 (en) 2005-11-01 2011-08-16 Cymer, Inc. Laser system
US8144740B1 (en) 2005-11-01 2012-03-27 Cymer, Inc. Laser system
US8170078B2 (en) 2005-11-01 2012-05-01 Cymer, Inc. Laser system
US8908735B2 (en) 2005-11-01 2014-12-09 Cymer, Llc Laser system
CN112018589A (en) * 2019-05-28 2020-12-01 天津凯普林激光科技有限公司 Laser amplification device and laser amplification method
CN112018589B (en) * 2019-05-28 2021-07-13 天津凯普林激光科技有限公司 Laser amplification device and laser amplification method
WO2022084233A1 (en) * 2020-10-23 2022-04-28 Coherent Kaiserslautern GmbH Multipass laser amplifier and no-optical-power beam steering element

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