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Random laser

February 22, 2023

A random laser (RL) is a laser in which optical feedback is provided by scattering particles.[1] As in conventional lasers, a gain medium is required for optical amplification. However, in contrast to Fabry–Pérot cavities and distributed feedback lasers, neither reflective surfaces nor distributed periodic structures are used in RLs, as light is confined in an active region by diffusive elements that either may or may not be spatially distributed inside the gain medium.

The main principle behind a random laser is to increase the light path with disordered media; this can be done by diffusive disordered media or by using strong localization in a disordered media, with laser active background.

Random lasing has been reported from a large variety of materials, e.g. colloidal solutions of dye and scattering particles,[2] semiconductor powders,[3] optical fibers [4] and polymers.[5] Due to the output emission with low spatial coherence and laser-like energy conversion efficiency, RLs are attractive devices for energy efficient illumination applications.[6] The concept of random lasing can also be time-reversed, resulting in a random anti-laser,[7] which is a disordered medium that can perfectly absorb incoming coherent radiation.

Principles of operation

 
Schematic description of (a) Fabry Perot laser (b) DFB laser (c) RL with spatially localized feedback (d) RL with spatially distributed feedback

The principle of operation of RLs has been extensively debated and different theoretical approaches have been reported (see references in [8]). The main elements of a RL, as in conventional lasers, are amplification and feedback, where amplification is provided by the pumped gain medium and feedback by scattering particles.

Distributed feedback is the most commonly used architecture,[1][2][3][4][5] in which scattering particles are embedded and randomly distributed into the gain medium. In contrast to distributed feedback, in spatially localized feedback RLs, gain and feedback are spatially separated with gain medium confined by the scattering media, which act as feedback elements and output couplers.[9][10]

In both architectures, resonances and lasing modes exist if closed loops with an integer number of wavelengths occur. A scattering particle adds a random (unpredictable) phase contribution to the incident wave. The scattered wave propagates and is scattered again, adding more random phase contributions. If all the phase contributions in a closed loop sum to an integer multiple of 2π at a certain frequency, a frequency mode is allowed to exist at that frequency.

Emission regimes

Since first reports, two different spectral signatures have been observed from RLs. The non-resonant emission (also referred as incoherent or amplitude-only emission) characterized by a single peaked spectrum with a FWHM of few nanometers, and the resonant emission (also referred as coherent emission), characterized by multiple narrow peaks with sub-nanometer linewidths, randomly distributed in frequency.

The previous nomenclature is due to the interpretation of the phenomena,[11] as the sharp resonances with sub-nanometer linewidths observed in resonant regime suggested some kind of contribution from optical phase while the non-resonant regime is understood as amplification of scattered light with no fixed phase relation between amplified photons.

In general, the two regimes of operation are attributed to the scattering properties of the diffusive element in distributed feedback RLs: a weakly (highly) scattering medium, having a transport mean free path much greater than (comparable to) the emission wavelength produce a non-resonant (resonant) random lasing emission.

Recently it has been demonstrated that the regime of operation depends not only on the material in use but also on the pump size and shape.[10][12] This suggested that the non-resonant regime is actually consisting of a large number of narrow modes which overlap in space and frequency and are strongly coupled together, collapsing into a single peaked spectrum with narrowed FWHM compared to the gain curve and amplified spontaneous emission. In resonant regime, fewer modes are excited, they do not compete each other for gain and do not couple together.

Anderson localization

Anderson localization is a well-known phenomenon that occurs when electrons become trapped in a disordered metallic structure, and this metal goes through a phase transition from conductor to insulator.[13] These electrons are said to be Anderson-localized. The conditions for this localization are that there is a high enough density of scatterers in the metal (other electrons, spins, etc.) to cause free electrons to follow a single looped path.

The analogy between photons and electrons has encouraged the vision that photons diffusing through a scattering medium could be also considered Anderson-localized. According to this, if the Ioffe-Regel[14] criterion, describing the ratio of photon wave-vector k to mean free path (of a photon not colliding with anything) l, is met: kl < 1, then there is a probability that photons will become trapped in much the same way as electrons are observed to be trapped under Anderson localization. In this way, while the photon is trapped, the scatters may act as an optical cavity. The gain medium in which the scatterers lie will allow stimulated emission to occur. As in an ordinary laser, if the gain is greater than the losses incurred, the lasing threshold will be broken and lasing can occur.

Photons traveling in this loop will also interfere with each other. The well defined cavity length (1–10 μm) will ensure that the interference is constructive and will allow certain modes to oscillate. The competition for gain permits one mode to oscillate once the lasing threshold has been reached.

Random-laser theory

Theory, however, shows that for multiple scattering in amplifying random media Anderson localization of light does not occur at all, even though the calculation of interferences are essential to prove that fact. In contrary, so called weak localizations processes can be proven, but it is vividly discussed, whether those mechanisms play the key role in the mode statistics or not.[citation needed]

Recent studies[citation needed] show that these weak localization processes are not the governing phenomena for the onset of random lasing. Random lasing occurs for kl > 1.[citation needed] This is in agreement with experimental findings.[citation needed] Even though travelling of light on exactly "closed loops" would explain the occurrence of confined lasing spots intuitively, the question is still open whether, e.g. the stimulated emission processes are correlated with those processes.[citation needed]

The theory of "preformed cavities" is, however, not confirmed.

Typical amounts of gain medium required to exceed the lasing threshold depend heavily on the scatterer density.

Applications

This field is relatively young and as such does not have many realized applications. However, random lasers based on ZnO are promising candidates for electrically pumped UV lasers, biosensors and optical information processing. This is due to the low production cost and that the optimal temperature for substrate production has been observed to be around 500 °C for powders. This is in contrast to producing an ordinary laser crystal at temperatures exceeding 700 °C.

The use of random lasers for the study of laser action in substances that could not be produced in the form of homogeneous large crystals have also been pointed out as a potential application. Furthermore, in frequency ranges where high-reflectivity mirrors are not available (e.g., gamma-rays, x-rays), the feedback provided by an appropriate scattering medium can be used as an alternative to laser action. Many of these applications proposed prior to 2005 have already been reviewed by Noginov.[15] In 2015, Luan and co-workers highlighted some of them, with an emphasis on the ones recently demonstrated,[16] including photonic barcode, optomicrofluidics, optical batteries, cancer diagnostic, speckle-free bioimaging, on-chip random spectrometer, time-resolved microscopy/spectroscopy, sensing, friend-foe identification, etc. Furthermore, random laser is naturally endowed with two key superiorities, namely, laser-level intensity and broad-angular emissions, which are mutually exclusive in thermal light sources, light-emitting-diodes (LEDs), and typical lasers. It is believed that random laser is a promising and advance lighting source for laser illumination,[17] and speckle-free imaging.[18]

See also

References

  1. ^ a b Noginov, M. A. (2005). "Solid-State Random Lasers". Springer Series in Optical Sciences. Vol. 105. New York: Springer-Verlag. doi:10.1007/b106788. ISBN 0-387-23913-8.
  2. ^ a b Lawandy, N. M.; Balachandran, R. M.; Gomes, A. S. L.; Sauvain, E. (1994-03-31). "Laser action in strongly scattering media". Nature. Springer Science and Business Media LLC. 368 (6470): 436–438. doi:10.1038/368436a0. ISSN 0028-0836. S2CID 26987876.
  3. ^ a b Cao, H.; Zhao, Y. G.; Ong, H. C.; Ho, S. T.; Dai, J. Y.; Wu, J. Y.; Chang, R. P. H. (1998-12-21). "Ultraviolet lasing in resonators formed by scattering in semiconductor polycrystalline films". Applied Physics Letters. AIP Publishing. 73 (25): 3656–3658. doi:10.1063/1.122853. ISSN 0003-6951.
  4. ^ a b Turitsyn, Sergei K.; Babin, Sergey A.; El-Taher, Atalla E.; Harper, Paul; Churkin, Dmitriy V.; Kablukov, Sergey I.; Ania-Castañón, Juan Diego; Karalekas, Vassilis; Podivilov, Evgenii V. (2010-02-07). "Random distributed feedback fibre laser". Nature Photonics. Springer Science and Business Media LLC. 4 (4): 231–235. doi:10.1038/nphoton.2010.4. ISSN 1749-4885. S2CID 39672706.
  5. ^ a b Sznitko, Lech; Mysliwiec, Jaroslaw; Miniewicz, Andrzej (2015-04-28). "The role of polymers in random lasing". Journal of Polymer Science Part B: Polymer Physics. Wiley. 53 (14): 951–974. doi:10.1002/polb.23731. ISSN 0887-6266.
  6. ^ Redding, Brandon; Cao, Hui; Choma, Michael A. (2012-12-01). "Speckle-Free Laser Imaging with Random Laser Illumination". Optics and Photonics News. The Optical Society. 23 (12): 30. doi:10.1364/opn.23.12.000030. ISSN 1047-6938.
  7. ^ Pichler, Kevin; Kühmayer, Matthias; Böhm, Julian; Brandstötter, Andre; Ambichl, Philipp; Kuhl, Ulrich; Rotter, Stefan (2019-03-21). "Random anti-lasing through coherent perfect absorption in a disordered medium". Nature. 567 (7748): 351–355. Bibcode:2019Natur.567..351P. doi:10.1038/s41586-019-0971-3. ISSN 0028-0836. PMID 30833737. S2CID 71144725.
  8. ^ Zaitsev, Oleg; Deych, Lev (2010-01-11). "Recent developments in the theory of multimode random lasers". Journal of Optics. 12 (2): 024001. arXiv:0906.3449. doi:10.1088/2040-8978/12/2/024001. ISSN 2040-8978. S2CID 15889798.
  9. ^ Consoli, Antonio; López, Cefe (2015-11-18). "Decoupling gain and feedback in coherent random lasers: experiments and simulations". Scientific Reports. Springer Science and Business Media LLC. 5 (1): 16848. doi:10.1038/srep16848. ISSN 2045-2322. PMC 4649543. PMID 26577668. S2CID 15492855.
  10. ^ a b Consoli, Antonio; Lopez, Cefe (2016-05-10). "Emission regimes of random lasers with spatially localized feedback". Optics Express. The Optical Society. 24 (10): 10912–10920. doi:10.1364/oe.24.010912. ISSN 1094-4087. PMID 27409912.
  11. ^ H. Cao, J.Y. Xu, Y. Ling, A.L. Burin, E.W. Seeling, Xiang Liu, and R.P.H. Chang "Random lasers with coherent feedback" IEEE J. Sel. Top. Quantum Electron. 9, 1, pp. 111-119 https://doi.org/10.1109/JSTQE.2002.807975
  12. ^ Leonetti, Marco; Conti, Claudio; Lopez, Cefe (2011-09-11). "The mode-locking transition of random lasers". Nature Photonics. Springer Science and Business Media LLC. 5 (10): 615–617. arXiv:1304.3652. doi:10.1038/nphoton.2011.217. ISSN 1749-4885. S2CID 55924096.
  13. ^ Anderson, P. W. (1958-03-01). "Absence of Diffusion in Certain Random Lattices". Physical Review. American Physical Society (APS). 109 (5): 1492–1505. doi:10.1103/physrev.109.1492. ISSN 0031-899X.
  14. ^ A. F. Ioffe and A. R. Regel "Non-crystalline, amorphous, and liquid electronic semiconductors" Prog. Semicond. 4, 237–291 (1960)
  15. ^ M. A. Noginov, Solid-state random lasers, Springer, New York, 2005. (And references therein.)
  16. ^ Luan, Feng; Gu, Bobo; Gomes, Anderson S.L.; Yong, Ken-Tye; Wen, Shuangchun; Prasad, Paras N. (2015). "Lasing in nanocomposite random media". Nano Today. Elsevier BV. 10 (2): 168–192. doi:10.1016/j.nantod.2015.02.006. ISSN 1748-0132.
  17. ^ Chang, Shu-Wei; Liao, Wei-Cheng; Liao, Yu-Ming; Lin, Hung-I; Lin, Hsia-Yu; Lin, Wei-Ju; Lin, Shih-Yao; Perumal, Packiyaraj; Haider, Golam (2018-02-09). "A White Random Laser". Scientific Reports. 8 (1): 2720. Bibcode:2018NatSR...8.2720C. doi:10.1038/s41598-018-21228-w. ISSN 2045-2322. PMC 5807428. PMID 29426912.
  18. ^ Redding, Brandon; Choma, Michael A.; Cao, Hui (June 2012). "Speckle-free laser imaging using random laser illumination". Nature Photonics. 6 (6): 355–359. arXiv:1110.6860. Bibcode:2012NaPho...6..355R. doi:10.1038/nphoton.2012.90. ISSN 1749-4893. PMC 3932313. PMID 24570762.

External links

  • Journal of Optics. Special issue: nano and random lasers. February 2010 [1]

February 22, 2023
random, laser, this, article, includes, list, general, references, lacks, sufficient, corresponding, inline, citations, please, help, improve, this, article, introducing, more, precise, citations, september, 2011, learn, when, remove, this, template, message, . This article includes a list of general references but it lacks sufficient corresponding inline citations Please help to improve this article by introducing more precise citations September 2011 Learn how and when to remove this template message A random laser RL is a laser in which optical feedback is provided by scattering particles 1 As in conventional lasers a gain medium is required for optical amplification However in contrast to Fabry Perot cavities and distributed feedback lasers neither reflective surfaces nor distributed periodic structures are used in RLs as light is confined in an active region by diffusive elements that either may or may not be spatially distributed inside the gain medium The main principle behind a random laser is to increase the light path with disordered media this can be done by diffusive disordered media or by using strong localization in a disordered media with laser active background Random lasing has been reported from a large variety of materials e g colloidal solutions of dye and scattering particles 2 semiconductor powders 3 optical fibers 4 and polymers 5 Due to the output emission with low spatial coherence and laser like energy conversion efficiency RLs are attractive devices for energy efficient illumination applications 6 The concept of random lasing can also be time reversed resulting in a random anti laser 7 which is a disordered medium that can perfectly absorb incoming coherent radiation Contents 1 Principles of operation 2 Emission regimes 3 Anderson localization 4 Random laser theory 5 Applications 6 See also 7 References 8 External linksPrinciples of operation Edit Schematic description of a Fabry Perot laser b DFB laser c RL with spatially localized feedback d RL with spatially distributed feedback The principle of operation of RLs has been extensively debated and different theoretical approaches have been reported see references in 8 The main elements of a RL as in conventional lasers are amplification and feedback where amplification is provided by the pumped gain medium and feedback by scattering particles Distributed feedback is the most commonly used architecture 1 2 3 4 5 in which scattering particles are embedded and randomly distributed into the gain medium In contrast to distributed feedback in spatially localized feedback RLs gain and feedback are spatially separated with gain medium confined by the scattering media which act as feedback elements and output couplers 9 10 In both architectures resonances and lasing modes exist if closed loops with an integer number of wavelengths occur A scattering particle adds a random unpredictable phase contribution to the incident wave The scattered wave propagates and is scattered again adding more random phase contributions If all the phase contributions in a closed loop sum to an integer multiple of 2p at a certain frequency a frequency mode is allowed to exist at that frequency Emission regimes EditSince first reports two different spectral signatures have been observed from RLs The non resonant emission also referred as incoherent or amplitude only emission characterized by a single peaked spectrum with a FWHM of few nanometers and the resonant emission also referred as coherent emission characterized by multiple narrow peaks with sub nanometer linewidths randomly distributed in frequency The previous nomenclature is due to the interpretation of the phenomena 11 as the sharp resonances with sub nanometer linewidths observed in resonant regime suggested some kind of contribution from optical phase while the non resonant regime is understood as amplification of scattered light with no fixed phase relation between amplified photons In general the two regimes of operation are attributed to the scattering properties of the diffusive element in distributed feedback RLs a weakly highly scattering medium having a transport mean free path much greater than comparable to the emission wavelength produce a non resonant resonant random lasing emission Recently it has been demonstrated that the regime of operation depends not only on the material in use but also on the pump size and shape 10 12 This suggested that the non resonant regime is actually consisting of a large number of narrow modes which overlap in space and frequency and are strongly coupled together collapsing into a single peaked spectrum with narrowed FWHM compared to the gain curve and amplified spontaneous emission In resonant regime fewer modes are excited they do not compete each other for gain and do not couple together Anderson localization EditAnderson localization is a well known phenomenon that occurs when electrons become trapped in a disordered metallic structure and this metal goes through a phase transition from conductor to insulator 13 These electrons are said to be Anderson localized The conditions for this localization are that there is a high enough density of scatterers in the metal other electrons spins etc to cause free electrons to follow a single looped path The analogy between photons and electrons has encouraged the vision that photons diffusing through a scattering medium could be also considered Anderson localized According to this if the Ioffe Regel 14 criterion describing the ratio of photon wave vector k to mean free path of a photon not colliding with anything l is met kl lt 1 then there is a probability that photons will become trapped in much the same way as electrons are observed to be trapped under Anderson localization In this way while the photon is trapped the scatters may act as an optical cavity The gain medium in which the scatterers lie will allow stimulated emission to occur As in an ordinary laser if the gain is greater than the losses incurred the lasing threshold will be broken and lasing can occur Photons traveling in this loop will also interfere with each other The well defined cavity length 1 10 mm will ensure that the interference is constructive and will allow certain modes to oscillate The competition for gain permits one mode to oscillate once the lasing threshold has been reached Random laser theory EditTheory however shows that for multiple scattering in amplifying random media Anderson localization of light does not occur at all even though the calculation of interferences are essential to prove that fact In contrary so called weak localizations processes can be proven but it is vividly discussed whether those mechanisms play the key role in the mode statistics or not citation needed Recent studies citation needed show that these weak localization processes are not the governing phenomena for the onset of random lasing Random lasing occurs for kl gt 1 citation needed This is in agreement with experimental findings citation needed Even though travelling of light on exactly closed loops would explain the occurrence of confined lasing spots intuitively the question is still open whether e g the stimulated emission processes are correlated with those processes citation needed The theory of preformed cavities is however not confirmed Typical amounts of gain medium required to exceed the lasing threshold depend heavily on the scatterer density Applications EditThis field is relatively young and as such does not have many realized applications However random lasers based on ZnO are promising candidates for electrically pumped UV lasers biosensors and optical information processing This is due to the low production cost and that the optimal temperature for substrate production has been observed to be around 500 C for powders This is in contrast to producing an ordinary laser crystal at temperatures exceeding 700 C The use of random lasers for the study of laser action in substances that could not be produced in the form of homogeneous large crystals have also been pointed out as a potential application Furthermore in frequency ranges where high reflectivity mirrors are not available e g gamma rays x rays the feedback provided by an appropriate scattering medium can be used as an alternative to laser action Many of these applications proposed prior to 2005 have already been reviewed by Noginov 15 In 2015 Luan and co workers highlighted some of them with an emphasis on the ones recently demonstrated 16 including photonic barcode optomicrofluidics optical batteries cancer diagnostic speckle free bioimaging on chip random spectrometer time resolved microscopy spectroscopy sensing friend foe identification etc Furthermore random laser is naturally endowed with two key superiorities namely laser level intensity and broad angular emissions which are mutually exclusive in thermal light sources light emitting diodes LEDs and typical lasers It is believed that random laser is a promising and advance lighting source for laser illumination 17 and speckle free imaging 18 See also EditList of laser articlesReferences Edit a b Noginov M A 2005 Solid State Random Lasers Springer Series in Optical Sciences Vol 105 New York Springer Verlag doi 10 1007 b106788 ISBN 0 387 23913 8 a b Lawandy N M Balachandran R M Gomes A S L Sauvain E 1994 03 31 Laser action in strongly scattering media Nature Springer Science and Business Media LLC 368 6470 436 438 doi 10 1038 368436a0 ISSN 0028 0836 S2CID 26987876 a b Cao H Zhao Y G Ong H C Ho S T Dai J Y Wu J Y Chang R P H 1998 12 21 Ultraviolet lasing in resonators formed by scattering in semiconductor polycrystalline films Applied Physics Letters AIP Publishing 73 25 3656 3658 doi 10 1063 1 122853 ISSN 0003 6951 a b Turitsyn Sergei K Babin Sergey A El Taher Atalla E Harper Paul Churkin Dmitriy V Kablukov Sergey I Ania Castanon Juan Diego Karalekas Vassilis Podivilov Evgenii V 2010 02 07 Random distributed feedback fibre laser Nature Photonics Springer Science and Business Media LLC 4 4 231 235 doi 10 1038 nphoton 2010 4 ISSN 1749 4885 S2CID 39672706 a b Sznitko Lech Mysliwiec Jaroslaw Miniewicz Andrzej 2015 04 28 The role of polymers in random lasing Journal of Polymer Science Part B Polymer Physics Wiley 53 14 951 974 doi 10 1002 polb 23731 ISSN 0887 6266 Redding Brandon Cao Hui Choma Michael A 2012 12 01 Speckle Free Laser Imaging with Random Laser Illumination Optics and Photonics News The Optical Society 23 12 30 doi 10 1364 opn 23 12 000030 ISSN 1047 6938 Pichler Kevin Kuhmayer Matthias Bohm Julian Brandstotter Andre Ambichl Philipp Kuhl Ulrich Rotter Stefan 2019 03 21 Random anti lasing through coherent perfect absorption in a disordered medium Nature 567 7748 351 355 Bibcode 2019Natur 567 351P doi 10 1038 s41586 019 0971 3 ISSN 0028 0836 PMID 30833737 S2CID 71144725 Zaitsev Oleg Deych Lev 2010 01 11 Recent developments in the theory of multimode random lasers Journal of Optics 12 2 024001 arXiv 0906 3449 doi 10 1088 2040 8978 12 2 024001 ISSN 2040 8978 S2CID 15889798 Consoli Antonio Lopez Cefe 2015 11 18 Decoupling gain and feedback in coherent random lasers experiments and simulations Scientific Reports Springer Science and Business Media LLC 5 1 16848 doi 10 1038 srep16848 ISSN 2045 2322 PMC 4649543 PMID 26577668 S2CID 15492855 a b Consoli Antonio Lopez Cefe 2016 05 10 Emission regimes of random lasers with spatially localized feedback Optics Express The Optical Society 24 10 10912 10920 doi 10 1364 oe 24 010912 ISSN 1094 4087 PMID 27409912 H Cao J Y Xu Y Ling A L Burin E W Seeling Xiang Liu and R P H Chang Random lasers with coherent feedback IEEE J Sel Top Quantum Electron 9 1 pp 111 119 https doi org 10 1109 JSTQE 2002 807975 Leonetti Marco Conti Claudio Lopez Cefe 2011 09 11 The mode locking transition of random lasers Nature Photonics Springer Science and Business Media LLC 5 10 615 617 arXiv 1304 3652 doi 10 1038 nphoton 2011 217 ISSN 1749 4885 S2CID 55924096 Anderson P W 1958 03 01 Absence of Diffusion in Certain Random Lattices Physical Review American Physical Society APS 109 5 1492 1505 doi 10 1103 physrev 109 1492 ISSN 0031 899X A F Ioffe and A R Regel Non crystalline amorphous and liquid electronic semiconductors Prog Semicond 4 237 291 1960 M A Noginov Solid state random lasers Springer New York 2005 And references therein Luan Feng Gu Bobo Gomes Anderson S L Yong Ken Tye Wen Shuangchun Prasad Paras N 2015 Lasing in nanocomposite random media Nano Today Elsevier BV 10 2 168 192 doi 10 1016 j nantod 2015 02 006 ISSN 1748 0132 Chang Shu Wei Liao Wei Cheng Liao Yu Ming Lin Hung I Lin Hsia Yu Lin Wei Ju Lin Shih Yao Perumal Packiyaraj Haider Golam 2018 02 09 A White Random Laser Scientific Reports 8 1 2720 Bibcode 2018NatSR 8 2720C doi 10 1038 s41598 018 21228 w ISSN 2045 2322 PMC 5807428 PMID 29426912 Redding Brandon Choma Michael A Cao Hui June 2012 Speckle free laser imaging using random laser illumination Nature Photonics 6 6 355 359 arXiv 1110 6860 Bibcode 2012NaPho 6 355R doi 10 1038 nphoton 2012 90 ISSN 1749 4893 PMC 3932313 PMID 24570762 External links EditJournal of Optics Special issue nano and random lasers February 2010 1 Retrieved from https en wikipedia org w index php title Random laser amp oldid 1139760330, wikipedia, wiki, book, books, library,

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