Editing Laser (section)

=== Exotic media ===

The pursuit of a high-quantum-energy laser using transitions between [[Nuclear isomer|isomeric states]] of an [[atomic nucleus]] has been the subject of wide-ranging academic research since the early 1970s.  Much of this is summarized in three review articles.<ref>{{cite journal |last1=Baldwin |first1=G.C. |last2=Solem |first2=J.C. |last3=Gol'danskii |first3=V. I.|year=1981 |title=Approaches to the development of gamma-ray lasers |journal=Reviews of Modern Physics |volume=53 |issue=4 |pages=687–744 |bibcode = 1981RvMP...53..687B |doi = 10.1103/RevModPhys.53.687}}</ref><ref>{{cite journal |last1=Baldwin |first1=G.C. |last2=Solem |first2=J.C. |year=1995 |title=Recent proposals for gamma-ray lasers |journal=Laser Physics |volume=5 |issue=2 |pages=231–239}}</ref><ref>{{cite journal |last1=Baldwin |first1=G.C. |last2=Solem |first2=J.C. |year=1997 |title=Recoilless gamma-ray lasers |journal=Reviews of Modern Physics |volume=69 |issue=4 |pages=1085–1117 |bibcode=1997RvMP...69.1085B|doi=10.1103/RevModPhys.69.1085 |url=https://zenodo.org/record/1233965 |access-date=June 13, 2019 |archive-date=July 28, 2019 |archive-url=https://web.archive.org/web/20190728114208/https://zenodo.org/record/1233965 |url-status=live}}</ref> This research has been international in scope but mainly based in the former Soviet Union and the United States.  While many scientists remain optimistic that a breakthrough is near, an operational [[gamma-ray laser]] is yet to be realized.<ref>{{cite journal |last1=Baldwin |first1=G.C. |last2=Solem |first2=J.C. |year=1982 |title=Is the time ripe? Or must we wait so long for breakthroughs?|journal=Laser Focus |volume=18 |issue=6 |pages=6&8}}</ref>

{{Anchor|multiphoton2016-01-30}}Some of the early studies were directed toward short pulses of neutrons exciting the upper isomer state in a solid so the gamma-ray transition could benefit from the line-narrowing of [[Mössbauer effect]].<ref>{{cite journal |last=Solem |first=J.C. |year=1979 |title=On the feasibility of an impulsively driven gamma-ray laser |journal=Los Alamos Scientific Laboratory Report LA-7898 |doi=10.2172/6010532 |osti=6010532}}</ref>{{Page missing|date=January 2024}}<ref>{{cite journal |last1=Baldwin |first1=G.C. |last2=Solem |first2=J.C.|year=1979 |title=Maximum density and capture rates of neutrons moderated from a pulsed source |journal=Nuclear Science & Engineering |volume=72 |issue=3 |pages=281–289 |url=http://www.ans.org/pubs/journals/nse/a_20384|doi=10.13182/NSE79-A20384 |bibcode=1979NSE....72..281B |access-date=January 13, 2016 |archive-date=February 7, 2016 |archive-url=https://web.archive.org/web/20160207090745/http://www.ans.org/pubs/journals/nse/a_20384 |url-status=live}}</ref> In conjunction, several advantages were expected from two-stage pumping of a three-level system.<ref>{{cite journal |last1=Baldwin |first1=G.C. |last2=Solem |first2=J.C. |year=1980|title=Two-stage pumping of three-level Mössbauer gamma-ray lasers |journal=Journal of Applied Physics |volume=51 |issue=5 |pages=2372–2380 |bibcode = 1980JAP....51.2372B |doi = 10.1063/1.328007}}</ref> It was conjectured that the nucleus of an atom embedded in the near field of a laser-driven coherently-oscillating electron cloud would experience a larger dipole field than that of the driving laser.<ref>{{cite conference |last=Solem |first=J.C. |title=AIP Conference Proceedings |year=1986 |chapter=Interlevel transfer mechanisms and their application to grasers |conference=Proceedings of Advances in Laser Science-I, First International Laser Science Conference, Dallas, TX 1985 (American Institute of Physics, Optical Science and Engineering, Series 6) |volume=146 |pages=22–25 |doi=10.1063/1.35861 |bibcode=1986AIPC..146...22S |chapter-url=https://digital.library.unt.edu/ark:/67531/metadc1105924/ |access-date=November 27, 2018 |archive-date=November 27, 2018 |archive-url=https://web.archive.org/web/20181127110611/https://digital.library.unt.edu/ark:/67531/metadc1105924/ |url-status=live}}</ref><ref>{{cite conference |last1=Biedenharn |first1=L.C. |last2=Boyer |first2=K. |last3=Solem |first3=J.C. |title=AIP Conference Proceedings |year=1986 |chapter=Possibility of grasing by laser-driven nuclear excitation |conference=Proceedings of AIP Advances in Laser Science-I, Dallas, TX, November 18–22, 1985 |volume=146 |pages=50–51|doi=10.1063/1.35928|bibcode=1986AIPC..146...50B}}</ref> Furthermore, the nonlinearity of the oscillating cloud would produce both spatial and temporal harmonics, so nuclear transitions of higher multipolarity could also be driven at multiples of the laser frequency.<ref>{{cite conference |last1=Rinker |first1=G.A. |last2=Solem |first2=J.C. |last3=Biedenharn |first3=L.C. |editor1-first=Randy C |editor1-last=Jones |title=Calculation of harmonic radiation and nuclear coupling arising from atoms in strong laser fields |book-title=Proc. SPIE 0875, Short and Ultrashort Wavelength Lasers |conference=1988 Los Angeles Symposium: O-E/LASE '88, 1988, Los Angeles, CA, United States |date=April 27, 1988 |publisher=International Society for Optics and Photonics |volume=146 |pages=92–101 |doi=10.1117/12.943887 |series=Short and Ultrashort Wavelength Lasers}}</ref><ref>{{cite journal |last1=Rinker |first1=G. A. |last2=Solem |first2=J.C. |last3=Biedenharn |first3=L.C. |year=1987 |title=Nuclear interlevel transfer driven by collective outer shell electron excitations |journal=Proceedings of the Second International Laser Science Conference, Seattle, WA (Advances in Laser Science-II) |editor=Lapp, M. |editor2=Stwalley, W.C. |editor3=Kenney-Wallace G.A. |publisher=American Institute of Physics |location=New York |volume=160 |pages=75–86 |oclc=16971600}}</ref><ref>{{cite journal |last=Solem |first=J.C. |year=1988 |title=Theorem relating spatial and temporal harmonics for nuclear interlevel transfer driven by collective electronic oscillation |journal=Journal of Quantitative Spectroscopy and Radiative Transfer |volume=40 |issue=6 |pages=713–715 |url=https://zenodo.org/record/1253954 |bibcode=1988JQSRT..40..713S |doi=10.1016/0022-4073(88)90067-2 |access-date=September 8, 2019 |archive-date=March 18, 2020 |archive-url=https://web.archive.org/web/20200318062519/https://zenodo.org/record/1253954 |url-status=live}}</ref><ref>{{cite journal |last1=Solem |first1=J.C. |last2=Biedenharn |first2=L.C. |year=1987 |title=Primer on coupling collective electronic oscillations to nuclei |journal=Los Alamos National Laboratory Report LA-10878 |url=http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/19/009/19009581.pdf |bibcode=1987pcce.rept.....S |page=1 |access-date=January 13, 2016 |archive-date=March 4, 2016 |archive-url=https://web.archive.org/web/20160304060942/http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/19/009/19009581.pdf |url-status=live}}</ref><ref>{{cite journal |last1=Solem |first1=J.C. |last2=Biedenharn |first2=L.C.|year=1988|title=Laser coupling to nuclei via collective electronic oscillations: A simple heuristic model study |journal=Journal of Quantitative Spectroscopy and Radiative Transfer |volume=40 |issue=6 |pages=707–712 |bibcode = 1988JQSRT..40..707S |doi = 10.1016/0022-4073(88)90066-0 }}</ref><ref>{{cite conference |last1=Boyer |first1=K. |last2=Java |first2=H. |last3=Luk |first3=T.S.|last4=McIntyre |first4=I.A.|last5=McPherson |first5=A.|last6=Rosman |first6=R.|last7=Solem |first7=J.C.|last8=Rhodes |first8=C.K. |last9=Szöke |first9=A. |year=1987 |title=Discussion of the role of many-electron motions in multiphoton ionization and excitation |book-title=Proceedings of International Conference on Multiphoton Processes (ICOMP) IV, July 13–17, 1987, Boulder, CA |editor=Smith, S. |editor2=Knight, P. |publisher=Cambridge University Press |location=Cambridge, England |pages=58 |osti=10147730}}</ref><ref>{{cite journal |last1=Biedenharn |first1=L.C. |last2=Rinker |first2=G.A. |last3=Solem |first3=J.C. |year=1989 |title=A solvable approximate model for the response of atoms subjected to strong oscillatory electric fields |journal=Journal of the Optical Society of America B|volume=6 |issue=2 |pages=221–227 |bibcode=1989JOSAB...6..221B|doi=10.1364/JOSAB.6.000221 |url=https://zenodo.org/record/1235650 |access-date=June 13, 2019 |archive-date=March 21, 2020 |archive-url=https://web.archive.org/web/20200321181221/https://zenodo.org/record/1235650 |url-status=live}}</ref>

In September 2007, the [[BBC News]] reported that there was speculation about the possibility of using [[positronium]] [[annihilation]] to drive a very powerful [[gamma ray]] laser.<ref name="Fildes">{{cite news |url=http://news.bbc.co.uk/2/hi/science/nature/6991030.stm |title=Mirror particles form new matter |first=Jonathan |last=Fildes |date=September 12, 2007 |work=BBC News |access-date=May 22, 2008 |archive-date=April 21, 2009 |archive-url=https://web.archive.org/web/20090421143709/http://news.bbc.co.uk/2/hi/science/nature/6991030.stm |url-status=live}}</ref> David Cassidy of the [[University of California, Riverside]] proposed that a single such laser could be used to ignite a [[nuclear fusion]] reaction, replacing the banks of hundreds of lasers currently employed in [[inertial confinement fusion]] experiments.<ref name="Fildes" />

Space-based [[X-ray laser]]s pumped by nuclear explosions have also been proposed as antimissile weapons.<ref>{{cite journal |first=Jeff |last=Hecht |title=The history of the x-ray laser |journal=Optics and Photonics News |volume=19 |issue=5 |date=May 2008 |pages=26–33 |doi=10.1364/opn.19.5.000026|bibcode = 2008OptPN..19R..26H}}</ref><ref>{{cite magazine |first=Clarence A. |last=Robinson |title=Advance made on high-energy laser |magazine=Aviation Week & Space Technology |date=February 23, 1981 |pages=25–27}}</ref> Such devices would be one-shot weapons.

Living cells have been used to produce laser light.<ref>{{cite news |url=https://www.bbc.co.uk/news/science-environment-13725719 |title=Laser is produced by a living cell |first=Jason |last=Palmer |date=June 13, 2011 |newspaper=BBC News |access-date=June 13, 2011 |archive-date=June 13, 2011 |archive-url=https://web.archive.org/web/20110613112054/http://www.bbc.co.uk/news/science-environment-13725719 |url-status=live}}</ref><ref>{{cite journal |title=Single-cell biological lasers |author1=Malte C. Gather |author2=Seok Hyun Yun |name-list-style=amp |date=June 12, 2011 |journal=Nature Photonics |doi=10.1038/nphoton.2011.99 |volume=5 |issue=7 |pages=406–410|bibcode=2011NaPho...5..406G}}</ref> The cells were genetically engineered to produce [[green fluorescent protein]], which served as the laser's gain medium. The cells were then placed between two 20-micrometer-wide mirrors, which acted as the laser cavity. When the cell was illuminated with blue light, it emitted intensely directed green laser light.