Show simple item record

dc.contributor.authorWiseman, Howard M
dc.date.accessioned2019-01-18T12:31:34Z
dc.date.available2019-01-18T12:31:34Z
dc.date.issued2016
dc.identifier.issn0031-8949
dc.identifier.doi10.1088/0031-8949/91/3/033001
dc.identifier.urihttp://hdl.handle.net/10072/142369
dc.description.abstractQuantum optics did not, and could not, flourish without the laser. The present paper is not about the principles of laser construction, still less a history of how the laser was invented. Rather, it addresses the question: what are the fundamental features that distinguish laser light from thermal light? The obvious answer, 'laser light is coherent', is, I argue, so vague that it must be put aside at the start, albeit to revisit later. A more specific, quantum theoretic, version, 'laser light is in a coherent state', is simply wrong in this context: both laser light and thermal light can equally well be described by coherent states, with amplitudes that vary stochastically in space. Instead, my answer to the titular question is that four principles are needed: high directionality, monochromaticity, high brightness, and stable intensity. Combining the first three of these principles suffices to show, in a quantitative way—involving, indeed, very large dimensionless quantities (up to )—that a laser must be constructed very differently from a light bulb. This quantitative analysis is quite simple, and is easily relatable to 'coherence', yet is not to be found in any textbooks on quantum optics to my knowledge. The fourth principle is the most subtle and, perhaps surprisingly, is the only one related to coherent states in the quantum optics sense: it implies that the description in terms of coherent states is the only simple description of a laser beam. Interestingly, this leads to the (not, as it turns out, entirely new) prediction that narrowly filtered laser beams are indistinguishable from similarly filtered thermal beams. I hope that other educators find this material useful; it may contain surprises even for researchers who have been in the field longer than I have.
dc.description.peerreviewedYes
dc.languageEnglish
dc.language.isoeng
dc.publisherRoyal Swedish Academy of Sciences
dc.relation.ispartofpagefrom033001-1
dc.relation.ispartofpageto033001-10
dc.relation.ispartofissue3
dc.relation.ispartofjournalPhysica Scripta
dc.relation.ispartofvolume91
dc.subject.fieldofresearchMathematical sciences
dc.subject.fieldofresearchPhysical sciences
dc.subject.fieldofresearchOther physical sciences not elsewhere classified
dc.subject.fieldofresearchcode49
dc.subject.fieldofresearchcode51
dc.subject.fieldofresearchcode519999
dc.titleHow many principles does it take to change a light bulb...into a laser?
dc.typeJournal article
dc.type.descriptionC1 - Articles
dc.type.codeC - Journal Articles
dc.description.versionAccepted Manuscript (AM)
gro.facultyGriffith Sciences, School of Environment and Science
gro.rights.copyright© 2016 Institute of Physics Publishing. This is the author-manuscript version of this paper. Reproduced in accordance with the copyright policy of the publisher. Please refer to the journal's website for access to the definitive, published version.
gro.hasfulltextFull Text
gro.griffith.authorWiseman, Howard M.


Files in this item

This item appears in the following Collection(s)

  • Journal articles
    Contains articles published by Griffith authors in scholarly journals.

Show simple item record