{"id":1552,"date":"2021-04-20T12:19:23","date_gmt":"2021-04-20T09:19:23","guid":{"rendered":"https:\/\/sites.uef.fi\/photonics\/?page_id=1552"},"modified":"2025-08-13T13:16:51","modified_gmt":"2025-08-13T10:16:51","slug":"coherence-photonics","status":"publish","type":"page","link":"https:\/\/sites.uef.fi\/photonics\/coherence-photonics\/","title":{"rendered":"Coherence photonics"},"content":{"rendered":"\n<p>We are constantly looking for talented and highly motivated applicants to join our research on coherence photonics. Contact person <a href=\"https:\/\/uefconnect.uef.fi\/en\/person\/tero.setala\/\">Prof. Tero Set\u00e4l\u00e4<\/a>.<\/p>\n\n\n\t<div id=\"accordion-block_7c57269587523eaa58816343ded025e6\" class=\"accordions\">\n\t\t\t\t\t<div class=\"accordion accordion-js\">\n\t\t\t\t<button class=\"accordion__button\" aria-controls=\"content-6037\" aria-expanded=\"false\" id=\"accordion-control-6037\">\n\t\t\t\t\t<h3 class=\"accordion__heading\" >\n\t\t\t\t\t\tThree-dimensional polarization states\t\t\t\t\t<\/h3>\n\t\t\t\t<\/button>\n\t\t\t\t<div class=\"accordion__content\" role=\"region\" aria-labelledby=\"accordion-control-6037\" aria-hidden=\"true\" id=\"content-6037\">\n\t\t\t\t\t<p>The growing interest towards ever more sophisticated optical systems in modern photonics has invoked the need for a full three-dimensional (3D) polarization treatment of light. For such genuinely 3D polarization states the local electric field evolves in three orthogonal directions in space. Light of this type is encountered, e.g., in optical near fields, tightly focused beams, and complex-structured electromagnetic radiation. Our research on random 3D optical fields has led to several discoveries concerning their polarimetric and dimensional structures, nonregular and anisotropic properties, as well as spin angular momentum characteristics, entailing new physical insights and notions about polarization of random light and with applications in high-numerical-aperture and nanophotonic systems. The research contains collaboration with the University of Zaragoza (Spain) as well as Shandong Normal University and Soochow University (China).<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-4384 alignleft\" src=\"https:\/\/sites.uef.fi\/photonics\/wp-content\/uploads\/sites\/150\/2022\/02\/research-coherence-three-dimensional-polarizations-states1.png\" alt=\"\" width=\"323\" height=\"342\" srcset=\"https:\/\/sites.uef.fi\/photonics\/wp-content\/uploads\/sites\/150\/2022\/02\/research-coherence-three-dimensional-polarizations-states1.png 380w, https:\/\/sites.uef.fi\/photonics\/wp-content\/uploads\/sites\/150\/2022\/02\/research-coherence-three-dimensional-polarizations-states1-284x300.png 284w\" sizes=\"auto, (max-width: 323px) 100vw, 323px\" \/><br \/>\n<em>Distribution of the polarimetric dimension\u00a0D\u00a0in the focal plane of a tightly focused, partially polarized beam with the degree of polarization a) 0, b) 0.3, c) 0.6, and d) 0.9. Inside the dashed circle the intensity is larger than 10 % of its maximum value (from [7]).<\/em><\/p>\n<p><b>Contact persons:<br \/>\n<\/b>Asst. Prof.\u00a0<a href=\"https:\/\/uefconnect.uef.fi\/en\/person\/andreas.norrman\/\">Andreas Norrman<\/a><br \/>\nProf.\u00a0<a href=\"https:\/\/uefconnect.uef.fi\/en\/person\/tero.setala\/\">Tero Set\u00e4l\u00e4<\/a><br \/>\nProf.\u00a0<a href=\"https:\/\/uefconnect.uef.fi\/en\/person\/ari.friberg\/\">Ari T. Friberg<\/a><\/p>\n<ol>\n<li>A. Norrman, A. T. Friberg, J. J. Gil, and T. Set\u00e4l\u00e4, \u201cDimensionality of random light fields\u201d,\u00a0<em>J. Eur. Opt. Soc.-Rapid Publ<\/em>.\u00a0<strong>13<\/strong>, 36 (2017).<\/li>\n<li>J. J. Gil, A. Norrman, A. T. Friberg, and T. Set\u00e4l\u00e4, \u201cPolarimetric purity and the concept of degree of polarization\u201d,\u00a0<em>Phys. Rev. A\u00a0<\/em><strong>97<\/strong>, 023838 (2018).<\/li>\n<li>J. J. Gil, A. Norrman, A. T. Friberg, and T. Set\u00e4l\u00e4, \u201cNonregularity of three-dimensional polarization states\u201d,\u00a0<em>Opt. Lett.<\/em>\u00a0<strong>43<\/strong>, 4611 (2018).<\/li>\n<li>A. Norrman, J. J. Gil, A. T. Friberg, and T. Set\u00e4l\u00e4, \u201cPolarimetric nonregularity of evanescent waves\u201d,\u00a0<em>Opt. Lett<\/em>.\u00a0<strong>44<\/strong>, 216 (2019).<\/li>\n<li>J. J. Gil, A. Norrman, A. T. Friberg, and T. Set\u00e4l\u00e4, \u201cIntensity and spin anisotropy of three-dimensional polarization states\u201d,\u00a0<em>Opt. Lett<\/em>.\u00a0<strong>44<\/strong>, 3578 (2019).<\/li>\n<li>J. J. Gil, I. San Jos\u00e9, A. Norrman, A. T. Friberg, and T. Set\u00e4l\u00e4, \u201cSets of orthogonal three-dimensional polarization states and their physical interpretation\u201d,\u00a0<em>Phys. Rev. A<\/em>\u00a0<strong>100<\/strong>, 033824 (2019).<\/li>\n<li>Y. Chen, F. Wang, Z. Dong, Y. Cai, A. Norrman, J. J. Gil, A. T. Friberg, and T. Set\u00e4l\u00e4, \u201cPolarimetric dimension and nonregularity of tightly focused light beams\u201d,\u00a0<em>Phys. Rev. A<\/em>\u00a0<strong>101<\/strong>, 053825 (2020).<\/li>\n<li>J. J. Gil, A. Norrman, A. T. Friberg, and T. Set\u00e4l\u00e4, \u201cEffect of polarimetric nonregularity on the spin of three-dimensional polarization states\u201d,\u00a0<em>New J. Phys.<\/em>\u00a0<strong>23<\/strong>, 063059 (2021).<\/li>\n<li>Y. Chen, F. Wang, Z. Dong, Y. Cai, A. Norrman, J. J. Gil, A. T. Friberg, and T. Set\u00e4l\u00e4, \u201cStructure of transverse spin in focused random light\u201d,\u00a0<em>Phys. Rev. A<\/em>\u00a0<strong>104<\/strong>, 013516 (2021).<\/li>\n<\/ol>\n\t\t\t\t<\/div>\n\t\t\t<\/div>\n\t\t\t<\/div>\n\t\n\n\t<div id=\"accordion-block_f1146552080d3450f5a0596f6cb389a2\" class=\"accordions\">\n\t\t\t\t\t<div class=\"accordion accordion-js\">\n\t\t\t\t<button class=\"accordion__button\" aria-controls=\"content-6293\" aria-expanded=\"false\" id=\"accordion-control-6293\">\n\t\t\t\t\t<h3 class=\"accordion__heading\" >\n\t\t\t\t\t\tNanoscale interactions\t\t\t\t\t<\/h3>\n\t\t\t\t<\/button>\n\t\t\t\t<div class=\"accordion__content\" role=\"region\" aria-labelledby=\"accordion-control-6293\" aria-hidden=\"true\" id=\"content-6293\">\n\t\t\t\t\t<p><strong><em>Optical near fields:<\/em><\/strong>\u00a0The manipulation and utilization of optical near fields at subwavelength dimensions play a vital role in nanophotonics. The celebrated surface plasmon polariton (SPP), in particular, has even triggered the rise of plasmonics as an own separate field covering multidisciplinary science and engineering. To date, however, most near-field investigations have concerned monochromatic and thus fully coherent fields, while in practice thermal effects, surface roughness, material impurities, and source fluctuations inevitably render the near field partially coherent. The rigorous assessment of coherence in such random optical near fields lies in our research focus. On the other hand, there is now a solid recognition that coherence also provides a novel and versatile degree of freedom to control the physical properties of optical near fields. In this context, our recently established notion of plasmon coherence engineering enables one to design polychromatic, complex-structured SPP fields of controlled state of coherence, endowed with nontrivial and flexible intensity, polarization, energy flow, and angular momentum distributions. The research in this emerging branch of nanophotonics \u2013 statistical plasmonics \u2013 is operated in close collaboration with Dalhousie University (Canada) and Soochow University (China).<\/p>\n<p><b>Contact persons:<br \/>\n<\/b>Asst. Prof.\u00a0<a href=\"https:\/\/uefconnect.uef.fi\/en\/person\/andreas.norrman\/\">Andreas Norrman<\/a><br \/>\nProf.\u00a0<a href=\"https:\/\/uefconnect.uef.fi\/en\/person\/tero.setala\/\">Tero Set\u00e4l\u00e4<\/a><br \/>\nProf.\u00a0<a href=\"https:\/\/uefconnect.uef.fi\/en\/person\/ari.friberg\/\">Ari T. Friberg<\/a><\/p>\n<ol>\n<li>A. Norrman, T. Set\u00e4l\u00e4, and A. T. Friberg, \u201cPartial spatial coherence and partial polarization in random evanescent fields on lossless interfaces\u201d,\u00a0<em>J. Opt. Soc. Am. A<\/em>\u00a0<strong>28<\/strong>, 391 (2011).<\/li>\n<li>A. Norrman, T. Set\u00e4l\u00e4, and A. T. Friberg, \u201cPartial coherence and polarization of a two-mode surface-plasmon polariton field at a metallic nanoslab\u201d,\u00a0<em>Opt. Express<\/em>\u00a0<strong>23<\/strong>, 20696 (2015).<\/li>\n<li>A. Norrman, T. Set\u00e4l\u00e4, and A. T. Friberg, \u201cGeneration and electromagnetic coherence of unpolarized three-component light fields\u201d,\u00a0<em>Opt. Lett<\/em>.\u00a0<strong>40<\/strong>, 5216 (2015).<\/li>\n<li>A. Norrman, S. A. Ponomarenko, and A. T. Friberg, \u201cPartially coherent surface plasmon polaritons\u201d,\u00a0<em>EPL\u00a0<\/em><strong>116<\/strong>, 64001 (2016).<\/li>\n<li>Y. Chen, A. Norrman, S. A. Ponomarenko, and A. T. Friberg, \u201cPlasmon coherence determination from nanoscattering\u201d,\u00a0<em>Opt. Lett.\u00a0<\/em><strong>42<\/strong>, 3279 (2017).<\/li>\n<li>Y. Chen, A. Norrman, S. A. Ponomarenko, and A. T. Friberg, \u201cPartially coherent axiconic surface plasmon polariton fields\u201d,\u00a0<em>Phys. Rev. A\u00a0<\/em><strong>97<\/strong>, 041801(R) (2018).<\/li>\n<li>Y. Chen, A. Norrman, S. A. Ponomarenko, and A. T. Friberg, \u201cCoherence lattices in surface plasmon polariton fields\u201d,\u00a0<em>Opt. Lett.\u00a0<\/em><strong>43<\/strong>, 3429 (2018).<\/li>\n<li>Y. Chen, A. Norrman, S. A. Ponomarenko, and A. T. Friberg, \u201cPartially coherent surface plasmon polariton vortex fields\u201d,\u00a0<em>Phys. Rev. A\u00a0<\/em><strong>100<\/strong>, 053833 (2019).<\/li>\n<li>Y. Chen, A. Norrman, S. A. Ponomarenko, and A. T. Friberg, \u201cOptical coherence and electromagnetic surface waves\u201d (invited review),\u00a0<em>Prog. Optics\u00a0<\/em><strong>65<\/strong>, 105 (2020).<\/li>\n<li>Y. Chen, A. Norrman, S. A. Ponomarenko, and A. T. Friberg, \u201cSpin density in partially coherent surface-plasmon-polariton vortex fields\u201d,\u00a0<em>Phys. Rev. A<\/em>\u00a0<strong>103<\/strong>, 063511 (2021).<\/li>\n<\/ol>\n<p><strong><em>Nanoprobe measurements:<\/em><\/strong>\u00a0Characterization of highly nonparaxial fields is vital in many situations of nanophotonics but for which the traditional beam-field methods are not applicable. A route to extract information of such fields is to employ scattering nanoparticles to mediate local information at the particles to the far-zone where the traditional methods can be used. This resembles the idea of scanning near-field optical microscopy (SNOM) where the near-field intensity is usually of interest. Our goal instead is to measure the polarization and coherence properties of light fields by using nanoscatterers. Earlier we have demonstrated polarization-state detection with a single scatterer and very recently the probing of spatial coherence using two particles in the contexts of both scalar and vectorial light beams. Currently, we are developing nanoprobe measurement techniques for completely general three-component fields.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-4452\" src=\"https:\/\/sites.uef.fi\/photonics\/wp-content\/uploads\/sites\/150\/2022\/02\/research-coherence-nanoscale-interactions1-1.png\" alt=\"\" width=\"245\" height=\"175\" \/><\/p>\n<p><em>Principle of a nanoscattering measurement of spatial (two-point) coherence (from [3]).<\/em><\/p>\n<p><strong>Contact persons:<\/strong><b><br \/>\n<\/b>Asst. Prof.\u00a0<a href=\"https:\/\/uefconnect.uef.fi\/en\/person\/andreas.norrman\/\">Andreas Norrman<\/a><br \/>\nProf.\u00a0<a href=\"https:\/\/uefconnect.uef.fi\/en\/person\/tero.setala\/\">Tero Set\u00e4l\u00e4<\/a><br \/>\nProf.\u00a0<a href=\"https:\/\/uefconnect.uef.fi\/en\/person\/ari.friberg\/\">Ari T. Friberg<\/a><\/p>\n<ol>\n<li>L.-P. Lepp\u00e4nen, K. Saastamoinen, J. Lehtolahti, A. T. Friberg, and T. Set\u00e4l\u00e4, \u201cDetection of partial polarization of light beams with dipolar nanocubes\u201d,\u00a0<em>Opt. Express<\/em>\u00a0<strong>24<\/strong>, 1472 (2016).<\/li>\n<li>K. Saastamoinen, L.-P. Lepp\u00e4nen, I. Vartiainen, A. T. Friberg, and T. Set\u00e4l\u00e4, \u201cSpatial coherence of light measured by nanoscattering\u201d,\u00a0<em>Optica<\/em>\u00a0<strong>5<\/strong>, 67 (2018).<\/li>\n<li>K. Saastamoinen, H. Partanen, A. T. Friberg, and T. Set\u00e4l\u00e4, \u201cProbing the electromagnetic degree of coherence of light beams with nanoscatterers\u201d,\u00a0<em>ACS Photonics<\/em>\u00a0<strong>7<\/strong>, 1030 (2020).<\/li>\n<\/ol>\n<p>&nbsp;<\/p>\n\t\t\t\t<\/div>\n\t\t\t<\/div>\n\t\t\t<\/div>\n\t\n\n\t<div id=\"accordion-block_606e5da10afeeed2c70ff563cda47720\" class=\"accordions\">\n\t\t\t\t\t<div class=\"accordion accordion-js\">\n\t\t\t\t<button class=\"accordion__button\" aria-controls=\"content-7636\" aria-expanded=\"false\" id=\"accordion-control-7636\">\n\t\t\t\t\t<h3 class=\"accordion__heading\" >\n\t\t\t\t\t\tFundamental concepts\t\t\t\t\t<\/h3>\n\t\t\t\t<\/button>\n\t\t\t\t<div class=\"accordion__content\" role=\"region\" aria-labelledby=\"accordion-control-7636\" aria-hidden=\"true\" id=\"content-7636\">\n\t\t\t\t\t<p><strong><em>Vector-field coherence:<\/em><\/strong>\u00a0The foundations of coherence theory of random vectorial light fields and the development of various interferometric schemes to measure such vector-light coherence form a long-standing, major research theme at our center. Over the years we have extended several results of scalar light fields into the domain of electromagnetic optics providing new insights into the physical interpretation of coherence in vectorial light beams and its interplay with the polarization characteristics. Among the most important results is the consistent formulation of the degree of coherence for vector-light fields and the measurement of the so-called polarization time in terms of two photon absorption. Very recent steps include, e.g., the development of ghost polarimetry and phase-contrast imaging, as well as the introduction of new techniques for measuring spectral and temporal coherence in stationary light. This subtopic contains collaboration with the University of Miami (USA), University of Groningen (The Netherlands), Technical University of Darmstadt (Germany), Tampere University (Finland), and Aalto University (Finland).<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-4366\" src=\"https:\/\/sites.uef.fi\/photonics\/wp-content\/uploads\/sites\/150\/2022\/02\/research-coherence-fundamental-concepts1.png\" alt=\"\" width=\"1358\" height=\"418\" srcset=\"https:\/\/sites.uef.fi\/photonics\/wp-content\/uploads\/sites\/150\/2022\/02\/research-coherence-fundamental-concepts1.png 1358w, https:\/\/sites.uef.fi\/photonics\/wp-content\/uploads\/sites\/150\/2022\/02\/research-coherence-fundamental-concepts1-300x92.png 300w, https:\/\/sites.uef.fi\/photonics\/wp-content\/uploads\/sites\/150\/2022\/02\/research-coherence-fundamental-concepts1-1024x315.png 1024w, https:\/\/sites.uef.fi\/photonics\/wp-content\/uploads\/sites\/150\/2022\/02\/research-coherence-fundamental-concepts1-768x236.png 768w\" sizes=\"auto, (max-width: 1358px) 100vw, 1358px\" \/><\/p>\n<p><em><strong>Left:<\/strong>\u00a0Illustration of the polarization-state evolution on the Poincar\u00e8 sphere and the polarization-sensitive Michelson interferometer employed in the measurement of polarization time in terms of two-photon absorption (from [2]).<strong>\u00a0Right:<\/strong>\u00a0Setup for measuring the spectral coherence Stokes parameters of a partially polarized light beam (from [5], cover picture).<\/em><\/p>\n<p><strong><em>Geometric phase:<\/em><\/strong>\u00a0The Pancharatnam-Berry phase is an additional phase contribution that a light beam acquires when its polarization state undergoes a cyclic in-phase evolution. Besides of its fundamental importance in optics and physics in general, the functionality of some novel optical elements is based on its emergence. Such elements can perform, e.g., focusing of light beams and more sophisticated operations such as generation of various helical beams by utilizing a form of spin-orbit coupling. In our works, we have demonstrated theoretically and experimentally that the geometric phase appears also in both spatial and temporal interference patterns of vectorial beams with different polarization states. This is a completely new context for the geometric phase and its consideration is expected to be important in controlled two-beam interference. This topic contains collaboration with Aalto University (Finland).<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-4372\" src=\"https:\/\/sites.uef.fi\/photonics\/wp-content\/uploads\/sites\/150\/2022\/02\/research-coherence-fundamental-concepts2.png\" alt=\"\" width=\"327\" height=\"215\" srcset=\"https:\/\/sites.uef.fi\/photonics\/wp-content\/uploads\/sites\/150\/2022\/02\/research-coherence-fundamental-concepts2.png 787w, https:\/\/sites.uef.fi\/photonics\/wp-content\/uploads\/sites\/150\/2022\/02\/research-coherence-fundamental-concepts2-300x197.png 300w, https:\/\/sites.uef.fi\/photonics\/wp-content\/uploads\/sites\/150\/2022\/02\/research-coherence-fundamental-concepts2-768x505.png 768w\" sizes=\"auto, (max-width: 327px) 100vw, 327px\" \/><\/p>\n<p><em>Experimental setup used for studying the geometric phase in Young\u2019s two-pinhole interference (from [1]).<\/em><\/p>\n<p><strong>Contact persons:<br \/>\n<\/strong><\/p>\n<p>Prof.\u00a0<a href=\"https:\/\/uefconnect.uef.fi\/en\/person\/tero.setala\/\">Tero Set\u00e4l\u00e4<\/a><br \/>\nProf. <a href=\"https:\/\/uefconnect.uef.fi\/en\/person\/ari.friberg\/\">Ari T. Friberg<\/a><br \/>\nAsst. Prof. <a href=\"https:\/\/uefconnect.uef.fi\/en\/person\/andreas.norrman\/\">Andreas Norrman<\/a><br \/>\nAssoc. Prof.\u00a0<a href=\"https:\/\/uefconnect.uef.fi\/en\/person\/tommi.hakala\/\">Tommi Hakala<\/a><br \/>\nDr.\u00a0<a href=\"https:\/\/uefconnect.uef.fi\/en\/person\/atri.halder\/\">Atri Halder<\/a><br \/>\nDr.\u00a0<a href=\"https:\/\/uefconnect.uef.fi\/en\/person\/kimmo.saastamoinen\/\">Kimmo Saastamoinen<\/a><\/p>\n<ol>\n<li>A. T. Friberg and T. Set\u00e4l\u00e4, \u201cElectromagnetic theory of optical coherence [Invited]\u201d,\u00a0<em>J. Opt. Soc. Am. A<\/em>\u00a0<strong>33<\/strong>, 2431 (2016).<\/li>\n<li>A. Shevchenko, M. Roussey, A. T. Friberg, and T. Set\u00e4l\u00e4, \u201cPolarization time of unpolarized light\u201d,\u00a0<em>Optica<\/em>\u00a0<strong>4<\/strong>, 64 (2017).<\/li>\n<li>H. Partanen, B. J. Hoenders, A. T. Friberg, and T. Set\u00e4l\u00e4, \u201cYoung\u2019s interference experiment with electromagnetic narrowband light\u201d,\u00a0<em>J. Opt. Soc. Am. A<\/em>\u00a0<strong>35<\/strong>, 1379 (2018); \u201cEditor\u2019s pick\u201d.<\/li>\n<li>A. Hannonen, B. J. Hoenders, W. Els\u00e4sser, A. T. Friberg, and T. Set\u00e4l\u00e4, \u201cGhost polarimetry using Stokes correlations\u201d,\u00a0<em>J. Opt. Soc. Am. A<\/em>\u00a0<strong>37<\/strong>, 714 (2020).<\/li>\n<li>A. Hannonen, A. Shevchenko, A. T. Friberg, and T. Set\u00e4l\u00e4, \u201cTemporal phase-contrast ghost imaging\u201d,\u00a0<em>Phys. Rev. A<\/em>\u00a0<strong>102<\/strong>, 063524 (2020).<\/li>\n<li>H. Partanen, A. T. Friberg, T. Set\u00e4l\u00e4, and J. Turunen, \u201cSpectral measurement of coherence Stokes parameters of random light beams\u201d,\u00a0<em>Phot. Res.<\/em>\u00a0<strong>7<\/strong>, 669 (2019). Cover article of Vol. 7, Issue 6, June 2019.<\/li>\n<li>A. Hannonen, H. Partanen, J. Tervo, T. Set\u00e4l\u00e4, and A. T. Friberg, \u201cPancharatnam-Berry phase in electromagnetic double-pinhole interference\u201d,\u00a0<em>Phys. Rev. A<\/em>\u00a0<strong>99<\/strong>, 053826 (2019).<\/li>\n<li>A. Hannonen, K. Saastamoinen, L.-P. Lepp\u00e4nen, M. Koivurova, A. Shevchenko, A. T. Friberg, and T. Set\u00e4l\u00e4, \u201cPancharatnam-Berry phase in polarization beating of optical beams\u201d,\u00a0<em>New J. Phys.<\/em>\u00a0<strong>21<\/strong>, 083030 (2019).<\/li>\n<li>A. Halder, H. Partanen, A. Leinonen, M. Koivurova, T. K. Hakala, T. Set\u00e4l\u00e4, J. Turunen, and A. T. Friberg, \u201cMirror-based scanning wavefront-folding interferometer for universal coherence measurements\u201d,\u00a0<em>Opt. Lett<\/em>.\u00a0<strong>45<\/strong>, 4260 (2020).<\/li>\n<li>A. Hannonen, H. Partanen, A. Leinonen, J. Heikkinen, T. K. Hakala, A. T. Friberg, and T. Set\u00e4l\u00e4, \u201cMeasurement of the Pancharatnam-Berry phase in two-beam interference\u201d,\u00a0<em>Optica<\/em>\u00a0<strong>7<\/strong>, 1435 (2020).<\/li>\n<li>J. Laatikainen, A. T. Friberg, O. Korotkova, and T. Set\u00e4l\u00e4, \u201cPoincar\u00e9 sphere of electromagnetic spatial coherence\u201d,\u00a0<em>Opt. Lett<\/em>.\u00a0<strong>46<\/strong>, 2143 (2021).<\/li>\n<li>A. Halder, A. Norrman, and A. T. Friberg, \u201cPoincar\u00e9 sphere representation of scalar two-beam interference under spatial unitary transformations\u201d,\u00a0<em>Opt. Lett.<\/em>\u00a0<strong>46<\/strong>, 5619 (2021).<\/li>\n<\/ol>\n\t\t\t\t<\/div>\n\t\t\t<\/div>\n\t\t\t<\/div>\n\t\n\n\t<div id=\"accordion-block_2f8c5e798238adb57f538ea931fdf167\" class=\"accordions\">\n\t\t\t\t\t<div class=\"accordion accordion-js\">\n\t\t\t\t<button class=\"accordion__button\" aria-controls=\"content-1493\" aria-expanded=\"false\" id=\"accordion-control-1493\">\n\t\t\t\t\t<h3 class=\"accordion__heading\" >\n\t\t\t\t\t\tGain assisted topological nanophotonics\t\t\t\t\t<\/h3>\n\t\t\t\t<\/button>\n\t\t\t\t<div class=\"accordion__content\" role=\"region\" aria-labelledby=\"accordion-control-1493\" aria-hidden=\"true\" id=\"content-1493\">\n\t\t\t\t\t<p>Our recent efforts focus on combining our expertise and recent findings in contexts of lasing in nanophotonic lattices, geometry, and topology. We aim to realize coherent nanoscale light sources with novel topological properties. The goal is to establish a thorough, solid connection between three crucial concepts, namely 1) the geometry of the lattice 2) the related topology, and 3) polarization and topological properties of the produced coherent nanoscale light fields. The project has the potential to provide fundamental understanding on the topology of nanoscale lasing phenomena, and, in the long term, to provide technological applications.<\/p>\n<p>In addition to various connections in Finland, the research contains collaboration with the Fudan University (China) as well as Iowa State University\/Ames Laboratory (USA).<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-5144 size-medium\" src=\"https:\/\/sites.uef.fi\/photonics\/wp-content\/uploads\/sites\/150\/2022\/03\/research-coherence-gain-assisted1-295x300.png\" alt=\"\" width=\"295\" height=\"300\" srcset=\"https:\/\/sites.uef.fi\/photonics\/wp-content\/uploads\/sites\/150\/2022\/03\/research-coherence-gain-assisted1-295x300.png 295w, https:\/\/sites.uef.fi\/photonics\/wp-content\/uploads\/sites\/150\/2022\/03\/research-coherence-gain-assisted1.png 450w\" sizes=\"auto, (max-width: 295px) 100vw, 295px\" \/><br \/>\nTopologically non-trivial lasing signal from a plasmonic lattice has been recently realized in our experiments [1].<\/p>\n<p><strong>Contact person:<\/strong><br \/>\nAssoc. Prof.\u00a0<a href=\"https:\/\/uefconnect.uef.fi\/en\/person\/tommi.hakala\/\">Tommi Hakala<\/a><\/p>\n<p><strong>References<\/strong><\/p>\n<ol>\n<li>B. O. Asamoah, M. Necada, W, Liu, J. Heikkinen, S. Mohamed, A. Halder, H. Rekola, M. Koivurova, A. I. V\u00e4kev\u00e4inen, P. T\u00f6rm\u00e4, J. Turunen, T. Set\u00e4l\u00e4, A. T. Friberg, L. Shi, and T. K. Hakala, \u201cTransition from bright mode to bound state in continuum lasing in plasmonic lattices\u201d, submitted.<\/li>\n<li>S. Mohamed, J Wang, H. Rekola, J. Heikkinen, B. O. Asamoah, L. Shi, and T. K. Hakala, \u201cControlling topology and polarization state of lasing photonic bound states in continuum\u201d, accepted for publication in\u00a0<em>Laser Photonics Rev.<\/em>, (2022).<\/li>\n<li>R. Heilmann, G. Salerno, J. Cuerda, T. K. Hakala, and P. To\u0308rma\u0308, \u201cQuasi-BIC mode lasing in a quadrumer plasmonic lattice\u201d,\u00a0<a href=\"https:\/\/pubs.acs.org\/doi\/full\/10.1021\/acsphotonics.1c01416\"><em>ACS Photonics<\/em>\u00a0<strong>9<\/strong>, 224<\/a>\u00a0(2022).<\/li>\n<li>S. Droulias, S. Mohamed, H. Rekola, T. K. Hakala, C. M. Soukoulis, and T. Koschny, \u201cExperimental demonstration of dark-state metasurface laser with controllable radiative coupling\u201d, accepted for publication in\u00a0<em>Adv. Opt. Mater.<\/em>\u00a0(2022).<\/li>\n<\/ol>\n\t\t\t\t<\/div>\n\t\t\t<\/div>\n\t\t\t<\/div>\n\t","protected":false},"excerpt":{"rendered":"<p>We are constantly looking for talented and highly motivated applicants to join our research on coherence photonics. Contact person Prof. Tero Set\u00e4l\u00e4.<\/p>\n","protected":false},"author":243,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"class_list":["post-1552","page","type-page","status-publish","hentry"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.1.1 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Coherence photonics - Center for Photonics Sciences<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/sites.uef.fi\/photonics\/coherence-photonics\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Coherence photonics - Center for Photonics Sciences\" \/>\n<meta property=\"og:description\" content=\"We are constantly looking for talented and highly motivated applicants to join our research on coherence photonics. 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