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Laser power scaling

January 01, 1970

Power scaling of a laser is increasing its output power without changing the geometry, shape, or principle of operation. Power scalability is considered an important advantage in a laser design. This means it can increase power without changing outside features.

Usually, power scaling requires a more powerful pump source, stronger cooling, and an increase in size. It may also require reduction of the background loss in the laser resonator and, in particular, in the gain medium.

MOPA edit

The most popular way of achieving power scalability is the "MOPA" (Master Oscillator Power Amplifier) approach. The master oscillator produces a highly coherent beam, and an optical amplifier is used to increase the power of the beam while preserving its main properties. The master oscillator has no need to be powerful, and has no need to operate at high efficiency because the efficiency is determined mainly by the power amplifier. The combination of several laser amplifiers seeded by a common master oscillator is essential concept of the High Power Laser Energy Research Facility.

Inherently scalable designs edit

Disk lasers edit

 
A disk laser configuration presented in 1992 at the SPIE conference.[1]

One type of solid-state laser designed for good power scaling is the disk laser (or "active mirror"[1]). Such lasers are believed to be scalable to a power of several kilowatts from a single active element in continuous-wave operation.[2]

Amplified spontaneous emission, overheating and round-trip loss seem to be the most important processes that limit the power of disk lasers.[3] For future power scaling, the reduction of the round-trip loss and/or combining of several active elements is required.

Fiber lasers edit

Fiber lasers are another type of solid-state laser with good power scaling. The power scaling of fiber lasers is limited by Raman scattering and Brillouin scattering, and by the fact that such lasers cannot be very long. The limited length of the double-clad fibers limits the usable power of the multi-mode pump, because the pump is not absorbed efficiently in the fiber's active core. Optimization of the shape of the cladding can extend the limit of power scaling.[4][5][6][7]

Fiber disk lasers edit

The limit of power scaling of fiber lasers can be extended with lateral delivery of the pump. This is realized in so-called fiber disk lasers.[8][9][10][11] The pump in such a laser is delivered from side of a disk, made of coiled fiber with doped core. Several such disks (with a coolant between them) can be combined into a stack.

Problem of heat sink edit

The power scaling is limited by the ability to dissipate the heat. Usually, the thermal conductivity of materials designed for efficient laser action, is small compared to that of materials optimal for the heat transfer (metals, diamonds). For the efficient drain of heat from a compact device, the active medium should be a narrow slab; in order to give advantage to the amplification of light at wanted direction over the ASE, the energy and head would be withdrawn in orthogonal directions, as it is shown in figure. At low background loss (typically, at the level of 0.01 or 0.001) the heat and the light can be withdrawn in the opposite directions, allowing active elements of wide aperture. In this case, combining of several active elements is used for the power scaling.

Coherent addition and combining beams edit

 
Coherent addition of 4 fiber lasers.[12][13]

Scalability can also be achieved by combining separate laser beams. Completely independent beams cannot usually be combined to produce a beam with higher radiance than each beam has alone. Beams can only be combined if they are coherent with each other. Such beams can be combined actively or passively.

In the passive combining (or coherent addition) of lasers, only the few modes common to all of the combined lasers can be above the lasing threshold. Efficient passive combining of eight lasers has been reported. Further power scaling requires exponential growth of the gain bandwidth and/or length of the individual lasers.

Active combining implies the real-time measurement of the phase of individual lasers' output, and quick adjustment to keep them all in phase. Such adjustment can be done by adaptive optics, which is effective for suppression of phase noise at acoustic frequencies. Faster schemes based on all-optical switching are being researched.

References edit

  1. ^ a b K. Ueda; N. Uehara (1993). Chung, Y. C (ed.). "Laser-diode-pumped solid state lasers for gravitational wave antenna". Proceedings of SPIE. Frequency-Stabilized Lasers and Their Applications. 1837: 336–345. Bibcode:1993SPIE.1837..336U. doi:10.1117/12.143686. S2CID 122045469. [dead link]
  2. ^ A. Giesen; H. Hügel; A. Voss; K. Wittig; U. Brauch; H. Opower (1994). "Scalable concept for diode-pumped high-power solid-state lasers". Applied Physics B. 58 (5): 365–372. Bibcode:1994ApPhB..58..365G. doi:10.1007/BF01081875. S2CID 121158745.
  3. ^ D. Kouznetsov; J.-F.Bisson; J.Dong; K.Ueda (2006). "Surface loss limit of the power scaling of a thin-disk laser". JOSA B. 23 (6): 1074–1082. Bibcode:2006JOSAB..23.1074K. doi:10.1364/JOSAB.23.001074.
  4. ^ Kouznetsov, D.; Moloney, J.V. (2003). "Highly efficient, high-gain, short-length, and power-scalable incoherent diode slab-pumped fiber amplifier/laser". IEEE Journal of Quantum Electronics. 39 (11): 1452–1461. Bibcode:2003IJQE...39.1452K. CiteSeerX 10.1.1.196.6031. doi:10.1109/JQE.2003.818311.
  5. ^ Kouznetsov, D.; Moloney, J.V. (2003). "Efficiency of pump absorption in double-clad fiber amplifiers. 2: Broken circular symmetry". JOSA B. 39 (6): 1259–1263. Bibcode:2002JOSAB..19.1259K. doi:10.1364/JOSAB.19.001259.
  6. ^ Leproux, P.; S. Fevrier; V. Doya; P. Roy; D. Pagnoux (2003). "Modeling and optimization of double-clad fiber amplifiers using chaotic propagation of pump". Optical Fiber Technology. 7 (4): 324–339. Bibcode:2001OptFT...7..324L. doi:10.1006/ofte.2001.0361.
  7. ^ A. Liu; K. Ueda (1996). "The absorption characteristics of circular, offset, and rectangular double-clad fibers". Optics Communications. 132 (5–6): 511–518. Bibcode:1996OptCo.132..511A. doi:10.1016/0030-4018(96)00368-9.
  8. ^ K. Ueda; A. Liu (1998). "Future of High-Power Fiber Lasers". Laser Physics. 8: 774–781.
  9. ^ K. Ueda (1999). "Scaling physics of disk-type fiber lasers for kW output". 1999 IEEE LEOS Annual Meeting Conference Proceedings. LEOS'99. 12th Annual Meeting. IEEE Lasers and Electro-Optics Society 1999 Annual Meeting (Cat. No.99CH37009). Vol. 2. pp. 788–789. doi:10.1109/leos.1999.811970. ISBN 978-0-7803-5634-4. S2CID 120732530. {{cite book}}: |journal= ignored (help)
  10. ^ Ueda; Sekiguchi H.; Matsuoka Y.; Miyajima H.; H.Kan (1999). "Conceptual design of kW-class fiber-embedded disk and tube lasers". Technical Digest. CLEO/Pacific Rim '99. Pacific Rim Conference on Lasers and Electro-Optics (Cat. No.99TH8464). Vol. 2. pp. 217–218. doi:10.1109/CLEOPR.1999.811381. ISBN 978-0-7803-5661-0. S2CID 30251829. {{cite book}}: |journal= ignored (help)
  11. ^ Hamamatsu K.K. (2006). "The Fiber Disk Laser explained". Nature Photonics. sample: 14–15. doi:10.1038/nphoton.2006.6.
  12. ^ A.Shirakawa; T.Satou; T. Sekiguchi; K. Ueda (2002). "Coherent addition of fiber lasers by use of a fiber coupler". Optics Express. 10 (21): 1167–1172. Bibcode:2002OExpr..10.1167S. doi:10.1364/oe.10.001167. PMID 19451976.
  13. ^ D.Kouznetsov; J.-F. Bisson; A. Shirakawa; K. Ueda (2005). . Optical Review. 12 (6): 445–447. Bibcode:2005OptRv..12..445K. doi:10.1007/s10043-005-0445-8. S2CID 27508450. Archived from the original on 2007-09-27. Retrieved 2007-03-18.

January 01, 1970
laser, power, scaling, power, scaling, laser, increasing, output, power, without, changing, geometry, shape, principle, operation, power, scalability, considered, important, advantage, laser, design, this, means, increase, power, without, changing, outside, fe. Power scaling of a laser is increasing its output power without changing the geometry shape or principle of operation Power scalability is considered an important advantage in a laser design This means it can increase power without changing outside features Usually power scaling requires a more powerful pump source stronger cooling and an increase in size It may also require reduction of the background loss in the laser resonator and in particular in the gain medium Contents 1 MOPA 2 Inherently scalable designs 2 1 Disk lasers 2 2 Fiber lasers 2 2 1 Fiber disk lasers 3 Problem of heat sink 4 Coherent addition and combining beams 5 ReferencesMOPA editThe most popular way of achieving power scalability is the MOPA Master Oscillator Power Amplifier approach The master oscillator produces a highly coherent beam and an optical amplifier is used to increase the power of the beam while preserving its main properties The master oscillator has no need to be powerful and has no need to operate at high efficiency because the efficiency is determined mainly by the power amplifier The combination of several laser amplifiers seeded by a common master oscillator is essential concept of the High Power Laser Energy Research Facility Inherently scalable designs editDisk lasers edit nbsp A disk laser configuration presented in 1992 at the SPIE conference 1 One type of solid state laser designed for good power scaling is the disk laser or active mirror 1 Such lasers are believed to be scalable to a power of several kilowatts from a single active element in continuous wave operation 2 Amplified spontaneous emission overheating and round trip loss seem to be the most important processes that limit the power of disk lasers 3 For future power scaling the reduction of the round trip loss and or combining of several active elements is required Fiber lasers edit Fiber lasers are another type of solid state laser with good power scaling The power scaling of fiber lasers is limited by Raman scattering and Brillouin scattering and by the fact that such lasers cannot be very long The limited length of the double clad fibers limits the usable power of the multi mode pump because the pump is not absorbed efficiently in the fiber s active core Optimization of the shape of the cladding can extend the limit of power scaling 4 5 6 7 Fiber disk lasers edit The limit of power scaling of fiber lasers can be extended with lateral delivery of the pump This is realized in so called fiber disk lasers 8 9 10 11 The pump in such a laser is delivered from side of a disk made of coiled fiber with doped core Several such disks with a coolant between them can be combined into a stack Problem of heat sink editThe power scaling is limited by the ability to dissipate the heat Usually the thermal conductivity of materials designed for efficient laser action is small compared to that of materials optimal for the heat transfer metals diamonds For the efficient drain of heat from a compact device the active medium should be a narrow slab in order to give advantage to the amplification of light at wanted direction over the ASE the energy and head would be withdrawn in orthogonal directions as it is shown in figure At low background loss typically at the level of 0 01 or 0 001 the heat and the light can be withdrawn in the opposite directions allowing active elements of wide aperture In this case combining of several active elements is used for the power scaling Coherent addition and combining beams edit nbsp Coherent addition of 4 fiber lasers 12 13 Scalability can also be achieved by combining separate laser beams Completely independent beams cannot usually be combined to produce a beam with higher radiance than each beam has alone Beams can only be combined if they are coherent with each other Such beams can be combined actively or passively In the passive combining or coherent addition of lasers only the few modes common to all of the combined lasers can be above the lasing threshold Efficient passive combining of eight lasers has been reported Further power scaling requires exponential growth of the gain bandwidth and or length of the individual lasers Active combining implies the real time measurement of the phase of individual lasers output and quick adjustment to keep them all in phase Such adjustment can be done by adaptive optics which is effective for suppression of phase noise at acoustic frequencies Faster schemes based on all optical switching are being researched References edit a b K Ueda N Uehara 1993 Chung Y C ed Laser diode pumped solid state lasers for gravitational wave antenna Proceedings of SPIE Frequency Stabilized Lasers and Their Applications 1837 336 345 Bibcode 1993SPIE 1837 336U doi 10 1117 12 143686 S2CID 122045469 dead link A Giesen H Hugel A Voss K Wittig U Brauch H Opower 1994 Scalable concept for diode pumped high power solid state lasers Applied Physics B 58 5 365 372 Bibcode 1994ApPhB 58 365G doi 10 1007 BF01081875 S2CID 121158745 D Kouznetsov J F Bisson J Dong K Ueda 2006 Surface loss limit of the power scaling of a thin disk laser JOSA B 23 6 1074 1082 Bibcode 2006JOSAB 23 1074K doi 10 1364 JOSAB 23 001074 Kouznetsov D Moloney J V 2003 Highly efficient high gain short length and power scalable incoherent diode slab pumped fiber amplifier laser IEEE Journal of Quantum Electronics 39 11 1452 1461 Bibcode 2003IJQE 39 1452K CiteSeerX 10 1 1 196 6031 doi 10 1109 JQE 2003 818311 Kouznetsov D Moloney J V 2003 Efficiency of pump absorption in double clad fiber amplifiers 2 Broken circular symmetry JOSA B 39 6 1259 1263 Bibcode 2002JOSAB 19 1259K doi 10 1364 JOSAB 19 001259 Leproux P S Fevrier V Doya P Roy D Pagnoux 2003 Modeling and optimization of double clad fiber amplifiers using chaotic propagation of pump Optical Fiber Technology 7 4 324 339 Bibcode 2001OptFT 7 324L doi 10 1006 ofte 2001 0361 A Liu K Ueda 1996 The absorption characteristics of circular offset and rectangular double clad fibers Optics Communications 132 5 6 511 518 Bibcode 1996OptCo 132 511A doi 10 1016 0030 4018 96 00368 9 K Ueda A Liu 1998 Future of High Power Fiber Lasers Laser Physics 8 774 781 K Ueda 1999 Scaling physics of disk type fiber lasers for kW output 1999 IEEE LEOS Annual Meeting Conference Proceedings LEOS 99 12th Annual Meeting IEEE Lasers and Electro Optics Society 1999 Annual Meeting Cat No 99CH37009 Vol 2 pp 788 789 doi 10 1109 leos 1999 811970 ISBN 978 0 7803 5634 4 S2CID 120732530 a href Template Cite book html title Template Cite book cite book a journal ignored help Ueda Sekiguchi H Matsuoka Y Miyajima H H Kan 1999 Conceptual design of kW class fiber embedded disk and tube lasers Technical Digest CLEO Pacific Rim 99 Pacific Rim Conference on Lasers and Electro Optics Cat No 99TH8464 Vol 2 pp 217 218 doi 10 1109 CLEOPR 1999 811381 ISBN 978 0 7803 5661 0 S2CID 30251829 a href Template Cite book html title Template Cite book cite book a journal ignored help Hamamatsu K K 2006 The Fiber Disk Laser explained Nature Photonics sample 14 15 doi 10 1038 nphoton 2006 6 A Shirakawa T Satou T Sekiguchi K Ueda 2002 Coherent addition of fiber lasers by use of a fiber coupler Optics Express 10 21 1167 1172 Bibcode 2002OExpr 10 1167S doi 10 1364 oe 10 001167 PMID 19451976 D Kouznetsov J F Bisson A Shirakawa K Ueda 2005 Limits of Coherent Addition of Lasers Simple Estimate Optical Review 12 6 445 447 Bibcode 2005OptRv 12 445K doi 10 1007 s10043 005 0445 8 S2CID 27508450 Archived from the original on 2007 09 27 Retrieved 2007 03 18 Retrieved from https en wikipedia org w index php title Laser power scaling amp oldid 1191980973, wikipedia, wiki, book, books, library,

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