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  26. %%% article in English
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  39. \title{Âèçóàëèçàöèÿ èçî÷àñòîòíûõ êîíòóðîâ ñèëüíî ëîêàëèçîâàííûõ âîëíîâîäíûõ ìîä â ïëàíàðíûõ äèýëåêòðè÷åñêèõ ñòðóêòóðàõ}
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  41. \rtitle{Âèçóàëèçàöèÿ èçî÷àñòîòíûõ êîíòóðîâ\dots}
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  43. \sodtitle{Âèçóàëèçàöèÿ èçî÷àñòîòíûõ êîíòóðîâ ñèëüíî ëîêàëèçîâàííûõ âîëíîâîäíûõ ìîä â ïëàíàðíûõ äèýëåêòðè÷åñêèõ ñòðóêòóðàõ}
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  45. %% authors and affiliation
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  48. \author{%
  49. Ä.\,Â.\,Ïåðìÿêîâ$^{a}$ \thanks{e-mail: d.permyakov@metalab.ifmo.ru},
  50. È.\,Ñ.\,Ñèíåâ$^{a}$
  51. Ñ.\,Ê.\,Ñû÷åâ$^{a}$
  52. A.\,C.\,Ãóäîâñêèõ$^{b}$
  53. À.\,À.\,Áîãäàíîâ$^{a}$
  54. À.\,Â.\,Ëàâðèíåíêî$^{a,c}$
  55. è À.\,Ê.\,Ñàìóñåâ$^{a}$
  56. }
  57. % author(s) - for colontitle (at the top of the page)
  58. %\rauthor{Ä.\,Â.\,Ïåðìÿêîâ, È.\,Ñ.\,Ñèíåâ, Ñ.\,Ê.\,Ñû÷åâ, À.\,À.\,Áîãäàíîâ, À.\,Â.\,Ëàâðèíåíêî and À.\,Ê.\,Ñàìóñåâ}
  59. \rauthor{Ä.\,Â.\,Ïåðìÿêîâ, È.\,Ñ.\,Ñèíåâ, Ñ.\,Ê.\,Ñû÷åâ è äð.}
  60. % author(s) - for table of contents
  61. \sodauthor{Ïåðìÿêîâ, Ñèíåâ, Ñû÷åâ, Ãóäîâñêèõ, Áîãäàíîâ, Ëàâðèíåíêî, Ñàìóñåâ}
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  63. \address{%
  64. $^a$ Óíèâåðñèòåò ÈÒÌÎ, 199034, Ñàíêò-Ïåòåðáóðã, Ðîññèÿ\\
  65. $^b$ Ñàíêò-Ïåòåðáóðãñêèé Àêàäåìè÷åñêèé óíèâåðñèòåò ÐÀÍ, 194021, Ñàíêò-Ïåòåðáóðã, Ðîññèÿ\\
  66. $^c$ DTU Fotonik, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
  67. }
  68. %%% dates of submition & resubmition (if submitted once, second argument is *)
  69. \dates{\today}{*}
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  71. %% Abstract
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  73. \abstract{
  74. Ïðåäëîæåíà ýêñïåðèìåíòàëüíàÿ ìåòîäèêà èçó÷åíèÿ äèñïåðñèîííûõ ñâîéñòâ îïòè÷åñêèõ ïîâåðõíîñòíûõ è âîëíîâîäíûõ ìîä â ïëàíàðíûõ ñòðóêòóðàõ. Ýêñïåðèìåíòàëüíàÿ óñòàíîâêà ïðåäñòàâëÿåò ñîáîé ìèêðîñêîï ñ âûñîêîàïåðòóðíûì îáúåêòèâîì è ëèíçîé òâåðäîé èììåðñèè â ôîðìå ïîëóñôåðû èç ñåëåíèäà öèíêà, ïðèâîäèìîé â êîíòàêò ñ ïîâåðõíîñòüþ îáðàçöà. Ïðè ýòîì ðåãèñòðàöèÿ îòðàæåíèÿ îò îáðàçöà ïðîâîäèòñÿ â çàäíåé ôîêàëüíîé ïëîñêîñòè ñèñòåìû. Òàêàÿ êîíôèãóðàöèÿ ïîçâîëÿåò èññëåäîâàòü â âèäèìîì è áëèæíåì èíôðàêðàñíîì ñïåêòðàëüíîì äèàïàçîíàõ ñèëüíî ëîêàëèçîâàííûå ñîñòîÿíèÿ ñ ýôôåêòèâíûì ïîêàçàòåëåì ïðåëîìëåíèÿ äî 2.25 â âèäèìîì è áëèæíåì èíôðàêðàñíîì ñïåêòðàëüíûõ äèàïàçîíàõ.
  75. Íà ïðèìåðå òîíêîãî ñëîÿ êðåìíèÿ, íàíåñåííîãî íà ñòåêëÿííóþ ïîäëîæêó, ïðîäåìîíñòðèðîâàíà âîçìîæíîñòü âèçóàëèçàöèè èçî÷àñòîòíûõ êîíòóðîâ ñ ïîëÿðèçàöèîííûì ðàçðåøåíèåì è âîññòàíîâëåíèÿ äèñïåðñèè ìîä âîëíîâîäà â çàâèñèìîñòè îò íàïðàâëåíèÿ èõ ðàñïðîñòðàíåíèÿ.
  76. }
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  78. %% main part of the manuscript
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  80. \begin{document}
  81. \maketitle
  82. %\section{Ââåäåíèå}
  83. Ïëàíàðíûå ôîòîííûå ñòðóêòóðû ñîñòàâëÿþò îñíîâó ñîâðåìåííîé îïòîýëåêòðîíèêè. Ê èõ ÷èñëó îòíîñÿòñÿ äèôðàêöèîííûå ðåøåòêè, ðàçëè÷íûå ôîòîííî-êðèñòàëëè÷åñêèå ïëàñòèíû, ìåìáðàíû, âîëíîâîäíûå ñòðóêòóðû è ìåòàïîâåðõíîñòè -- äâóìåðíûé àíàëîã ìåòàìàòåðèàëîâ~\cite{tamir2013guided,haus1984waves,bonaccorso2010graphene,ebeling2012integrated}. Îñíîâíîé õàðàêòåðèñòèêîé òàêèõ ñòðóêòóð ÿâëÿåòñÿ ñïåêòð èõ ñîáñòâåííûõ ìîä, êîòîðûé â îáùåì ñëó÷àå ñîñòîèò èç âîëíîâîäíûõ, ïîâåðõíîñòíûõ è ðåçîíàíñíûõ ñîñòîÿíèé (óòåêàþùèõ ìîä). Ðåçîíàíñíûå ñîñòîÿíèÿ ìîãóò áûòü èññëåäîâàíû â ýêñïåðèìåíòàõ ïî èçìåðåíèþ ñïåêòðîâ ïðîïóñêàíèÿ~\cite{lousse2004angular}, îòðàæåíèÿ~\cite{liu1998high}, ïîãëîùåíèÿ~\cite{christ2003waveguide} èëè ëþìèíåñöåíöèè~\cite{ganesh2007enhanced}. Âîëíîâîäíûå è ïîâåðõíîñòíûå ìîäû \footnote{Äëÿ êðàòêîñòè äëÿ âîëíîâîäíûõ è ïîâåðõíîñòíûõ ìîä ìû áóäåì èñïîëüçîâàòü òåðìèí ëîêàëèçîâàííûå ñîñòîÿíèÿ.} â òàêèõ ýêñïåðèìåíòàõ ñåáÿ íå îáíàðóæèâàþò, òàê êàê èõ äèñïåðñèîííûå êðèâûå ëåæàò íèæå ñâåòîâîé ëèíèè. Ïîýòîìó äëÿ èõ âîçáóæäåíèÿ èñïîëüçóþòñÿ ïðèçìû ñ âûñîêèì ïîêàçàòåëåì ïðåëîìëåíèÿ, äèôðàêöèîííûå ðåøåòêè, ðåçîíàíñíûå îïòè÷åñêèå àíòåííû èëè øåðîõîâàòîñòè~\cite{maier2007plasmonics}.
  84. Àíèçîòðîïèÿ ïëàíàðíûõ ôîòîííûõ ñòðóêòóð ïðèâîäèò ê çàâèñèìîñòè äèñïåðñèè ëîêàëèçîâàííûõ ñîñòîÿíèé îò íàïðàâëåíèÿ èõ ðàñïðîñòðàíåíèÿ. Ýòî ïîçâîëÿåò ðåàëèçîâàòü íåîáû÷íûå ðåæèìû ðàñïðîñòðàíåíèÿ âîëí, íàïðèìåð, êàíàëèðîâàíèå, îòðèöàòåëüíîå ïðåëîìëåíèå èëè îäíîíàïðàâëåííîå ðàñïðîñòðàíåíèå~\cite{high2015visible,takayama2017photonics}. Ýòè ýôôåêòû ìîæíî íàãëÿäíî îáúÿñíèòü â òåðìèíàõ èçî÷àñòîòíûõ êîíòóðîâ, òàê êàê îíè îïðåäåëÿþò çàâèñèìîñòü ãðóïïîâîé ñêîðîñòè âîëíû $\mathbf{v}_{\text{g}}=\nabla_\mathbf{k}\omega$ îò íàïðàâëåíèÿ ðàñïðîñòðàíåíèÿ è, êàê ñëåäñòâèå, ôîðìó âîëíîâûõ ôðîíòîâ. Ïîýòîìó, âàæíîé çàäà÷åé ýêñïåðèìåíòàëüíîé îïòèêè ÿâëÿåòñÿ âèçóàëèçàöèÿ èçî÷àñòîòíûõ êîíòóðîâ ñîñòîÿíèé, âîçáóæäàåìûõ â òàêèõ ñòðóêòóðàõ.
  85. Îäíèì èç âîçìîæíûõ ðåøåíèé ÿâëÿåòñÿ èñïîëüçîâàíèå ìåòîäà ìèêðîñêîïèè çàäíåé ôîêàëüíîé ïëîñêîñòè (òàêæå íàçûâàåìîé Ôóðüå-ìèêðîñêîïèåé). Ðåãèñòðàöèÿ ñèãíàëà â çàäíåé ôîêàëüíîé ïëîñêîñòè îïòè÷åñêîé ñèñòåìû ïîçâîëÿåò âèçóàëèçèðîâàòü äèàãðàììû íàïðàâëåííîñòè èçëó÷åíèÿ îäèíî÷íûõ èñòî÷íèêîâ~\cite{zhang2014back} è õàðàêòåðèçîâàòü çîííóþ ñòðóêòóðó ôîòîííûõ êðèñòàëëîâ~\cite{wagner2012back}. Ïðè èñïîëüçîâàíèè èììåðñèîííûõ îáúåêòèâîâ ñòàíîâèòñÿ âîçìîæíûì íàáëþäàòü è äèàãðàììû íàïðàâëåííîñòè ëîêàëèçîâàííûõ ñîñòîÿíèé, íàõîäÿùèõñÿ ïîä ñâåòîâûì êîíóñîì âîçäóõà.  ÷àñòíîñòè, ìåòîä ìèêðîñêîïèè çàäíåé ôîêàëüíîé ïëîñêîñòè áûë óñïåøíî ïðèìåíåí â óñòàíîâêå ìèêðîñêîïèè óòå÷êè èçëó÷åíèÿ äëÿ íàáëþäåíèÿ äèàãðàìì íàïðàâëåííîñòè ïîâåðõíîñòíûõ ïëàçìîí-ïîëÿðèòîíîâ, âîçáóæäàåìûõ äåôåêòàìè íà òîíêèõ ïëåíêàõ ìåòàëëà~\cite{drezet2008leakage,sinev2017chirality}. Îäíàêî, â ýòîì ñëó÷àå ìàêñèìàëüíûé âîëíîâîé âåêòîð íàáëþäàåìûõ ïîâåðõíîñòíûõ âîëí îãðàíè÷åí ÷èñëîâîé àïåðòóðîé èñïîëüçóåìîãî èììåðñèîííîãî îáúåêòèâà, à ÷àùå - ïîêàçàòåëåì ïðåëîìëåíèÿ ïîäëîæêè, ÷åðåç êîòîðóþ ïðîèñõîäèò óòå÷êà èçëó÷åíèÿ.  ðåçóëüòàòå, ïîäîáíûå óñòàíîâêè íå ïîçâîëÿþò ïîëó÷àòü èíôîðìàöèþ î ëîêàëèçîâàííûõ ìîäàõ ñ âîëíîâûì âåêòîðîì âûøå (1.4-1.6)$k_0$, ãäå $k_0$ - âîëíîâîé âåêòîð ñâåòà â âàêóóìå.
  86. Äëÿ íàáëþäåíèÿ ñîñòîÿíèé ñ ñèëüíîé ëîêàëèçàöèåé (òî åñòü, ñ áîëüøèìè âîëíîâûìè âåêòîðàìè â ïëîñêîñòè ñòðóêòóðû) ìîæåò áûòü òàêæå èñïîëüçîâàí ìåòîä ñêàíèðóþùåé áëèæíåïîëüíîé ìèêðîñêîïèè~\cite{lin2013polarization,permyakov2014mapping}, êîòîðûé, îäíàêî, ãîðàçäî áîëåå ñëîæåí òåõíè÷åñêè.
  87. Óâåëè÷åíèå ýôôåêòèâíîé ÷èñëîâîé àïåðòóðû îïòè÷åñêîé ñèñòåìû âîçìîæíî çà ñ÷åò èñïîëüçîâàíèÿ òàê íàçûâàåìûõ ëèíç òâåðäîé èììåðñèè~\cite{mansfield1990solid}. Òàêàÿ ëèíçà ïðåäñòàâëÿåò ñîáîé ýëåìåíò èç ïðîçðà÷íîãî ìàòåðèàëà, îáû÷íî èìåþùèé ôîðìó ïîëóñôåðû, êîòîðûé ïîìåùàåòñÿ ìåæäó îáúåêòèâîì è èññëåäóåìûì îáðàçöîì è ïðèâîäèòñÿ â êîíòàêò ñ ïîâåðõíîñòüþ ïîñëåäíåãî, êàê ïðîèëëþñòðèðîâàíî íà Ðèñ.~\ref{FigExpSetupAndSample}. Ïðè èñïîëüçîâàíèè ñ îáû÷íûì ñóõèì îáúåêòèâîì ëèíçà ìîæåò óâåëè÷èâàòü ýôôåêòèâíóþ ÷èñëîâóþ àïåðòóðó ñèñòåìû â $n$ ðàç, ãäå $n$ - ïîêàçàòåëü ïðåëîìëåíèÿ ìàòåðèàëà ëèíçû. Èäåÿ èñïîëüçîâàíèÿ òàêèõ ýëåìåíòîâ â ñèñòåìàõ ìèêðîñêîïèè áûëà âïåðâûå ïðåäëîæåíà â ðàáîòå~\cite{mansfield1990solid}. Ñ òåõ ïîð ëèíçû òâåðäîé èììåðñèè ïîëó÷èëè øèðîêîå ïðèìåíåíèå â ìèêðîñêîïèè.  ïåðâóþ î÷åðåäü, îíè èñïîëüçóþòñÿ êàê óñòðîéñòâà äëÿ óëó÷øåíèÿ ôîêóñèðîâêè ñâåòîâûõ ïó÷êîâ äëÿ ïðèëîæåíèé â ëàçåðíîé ëèòîãðàôèè~\cite{ghislain1999near} è ôîðìèðîâàíèè èçîáðàæåíèé ñî ñâåðõâûñîêèì ïðîñòðàíñòâåííûì ðàçðåøåíèåì~\cite{wu1999realization,mason2010enhanced,wang2011wide}, à òàêæå äëÿ íàáëþäåíèÿ ëþìèíåñöåíöèè îäèíî÷íûõ èñòî÷íèêîâ â ãåîìåòðèè ïîëíîãî âíóòðåííåãî îòðàæåíèÿ (ÏÂÎ)~\cite{wrigge2007efficient,rezus2012single}. Êðîìå òîãî, áûëî ïðåäëîæåíî èñïîëüçîâàòü ëèíçû òâåðäîé èììåðñèè â ñèñòåìàõ ìèêðîñêîïèè çàäíåé ôîêàëüíîé ïëîñêîñòè~\cite{zhang2004wide}, ÷òî ïîçâîëèëî íàáëþäàòü äèàãðàììû íàïðàâëåííîñòè ïîâåðõíîñòíûõ ïëàçìîí-ïîëÿðèòîíîâ, âîçáóæäàåìûõ íà ãðàíèöå òîíêèõ ìåòàëëè÷åñêèõ ïëåíîê, îäíàêî ÷èñëîâàÿ àïåðòóðà òàêèõ ñèñòåì îñòàâàëàñü ñðàâíèòåëüíî íåáîëüøîé.
  88.  íàøåé ðàáîòå ìû ïðåäëàãàåì èñïîëüçîâàòü àíàëîãè÷íóþ ñõåìó, ñîâìåùàþùóþ ìèêðîñêîïèþ çàäíåé ôîêàëüíîé ïëîñêîñòè è òâåðäóþ èììåðñèþ, äëÿ âèçóàëèçàöèè èçî÷àñòîòíûõ êîíòóðîâ ëîêàëèçîâàííûõ ìîä, âîçáóæäàåìûõ â ïëàíàðíûõ âîëíîâîäàõ è ìåòàïîâåðõíîñòÿõ. Áëàãîäàðÿ èñïîëüçîâàíèþ ìèíèàòþðíîé (äèàìåòð 3~ìì) ëèíçû èç ZnSe ($n_{ZnSe}=2.54$ ïðè $\lambda=700$~íì~\cite{Marple1964znse}) â ïðåäëîæåííîé ñõåìå äîñòèãàåòñÿ áîëüøàÿ ýôôåêòèâíàÿ ÷èñëîâàÿ àïåðòóðà (îêîëî 2.25 â çàâèñèìîñòè îò äèàïàçîíà ÷àñòîò, â êîòîðîì ïðîâîäÿòñÿ èçìåðåíèÿ), ïîçâîëÿþùàÿ ïîëó÷àòü èíôîðìàöèþ î ìîäàõ ñ âûñîêèì ýôôåêòèâíûì ïîêàçàòåëåì ïðåëîìëåíèÿ. Âàæíîé îñîáåííîñòüþ óñòàíîâêè ÿâëÿåòñÿ âîçìîæíîñòü õàðàêòåðèçàöèè äèñïåðñèè ïîâåðõíîñòíûõ âîëí â çàâèñèìîñòè îò íàïðàâëåíèÿ ðàñïðîñòðàíåíèÿ. Ìû äåìîíñòðèðóåì ôóíêöèîíàëüíîñòü ðàçðàáîòàííîé íàìè óñòàíîâêè íà ïðèìåðå âîëíîâîäà èç àìîðôíîãî êðåìíèÿ. Ìû âèçóàëèçèðóåì èçî÷àñòîòíûå êîíòóðû âîëíîâîäíûõ ìîä â òàêîé ñèñòåìå ñ ïîëÿðèçàöèîííûì ðàçðåøåíèåì è èç ïîëó÷åííûõ äàííûõ âîññòàíàâëèâàåì èõ çàêîíû äèñïåðñèè.
  89. \begin{figure}[t]\centering
  90. \includegraphics[width=0.9\linewidth]{FigExpSetup}
  91. \caption{
  92. \label{FigExpSetupAndSample}
  93. Ðèñ.~\ref{FigExpSetupAndSample}.
  94. (à)~Îáùàÿ ñõåìà ýêñïåðèìåíòàëüíîé óñòàíîâêè äëÿ íàáëþäåíèÿ ïîâåðõíîñòíûõ âîëí.
  95. (á)~Ñõåìàòè÷íîå ïðåäñòàâëåíèå îáðàçöà, ïðèâåäåííîãî â êîíòàêò ZnSe ïðèçìîé. Âåëè÷èíà âîçäóøíîãî çàçîðà $h_{air}$ ìîæåò âàðüèðîâàòüñÿ ñ ïîìîùüþ ïüåçîïîçèöèîíåðà â äèàïàçîíå îò íåñêîëüêèõ ìêì äî $\approx$20~íì. Ñèñòåìà íàñòðàèâàåòñÿ òàêèì îáðàçîì, ÷òîáû ôîêóñ îáúåêòèâà íàõîäèëñÿ â öåíòðå ïëîñêîé ÷àñòè ïîëóñôåðè÷åñêîé ëèíçû.
  96. (â)~Ñõåìà, èëëþñòðèðóþùàÿ ðàñïðåäåëåíèå ïîëÿðèçàöèè âîçáóæäàþùåãî èçëó÷åíèÿ â çàäíåé ôîêàëüíîé ïëîñêîñòè îáúåêòèâà äëÿ ëèíåéíîé ïîëÿðèçàöèè ïó÷êà çàñâåòêè. Ðàçíûå òî÷êè â çàäíåé ôîêàëüíîé ïëîñêîñòè ñîîòâåòñòâóþò ðàçíûì óãëàì ïàäåíèÿ ëó÷åé íà îáðàçåö.
  97. }
  98. \end{figure}
  99. \section{Ìåòîäû}
  100. \begin{figure*}[t]\centering
  101. \includegraphics[width=0.8\linewidth]{FigGaps}
  102. \caption{
  103. \label{FigGaps}
  104. Ðèñ.~\ref{FigGaps}.
  105. Âåðõíèé ðÿä: èçîáðàæåíèÿ îòðàæåíèÿ îò ïëîñêîé ãðàíèöû ëèíçû òâåðäîé èììåðñèè â çàäíåé ôîêàëüíîé ïëîñêîñòè îïòè÷åñêîé ñèñòåìû äëÿ ðàçëè÷íûõ âåëè÷èí âîçäóøíîãî çàçîðà ìåæäó ëèíçîé è ïëàíàðíûì êðåìíèåâûì âîëíîâîäîì. Äëèíà âîëíû âîçáóæäåíèÿ $\lambda=700$~íì, ïîëÿðèçàöèÿ îòìå÷åíà ñòðåëêîé íà ðèñóíêå (à).
  106. Íèæíèé ðÿä: ÷èñëåííûé ðàñ÷åò îòðàæåíèÿ îò ñëîèñòîé ñòðóêòóðû (ZnSe/âîçäóøíûé çàçîð/Si âîëíîâîä/êâàðöåâàÿ ïîäëîæêà), ïðåäñòàâëåííûé â îñÿõ âîëíîâûõ âåêòîðîâ âîëíû, ïàäàþùåé èç ZnSe.}
  107. \end{figure*}
  108. Ñõåìà ýêñïåðèìåíòàëüíîé óñòàíîâêè ïðåäñòàâëåíà íà Ðèñ.~\ref{FigExpSetupAndSample}à. Ñèñòåìà ñî÷åòàåò â ñåáå âûñîêîàïåðòóðíûé îáúåêòèâ ñ äëèííûì ðàáî÷èì îòðåçêîì (Mitutoyo, M Plan Apo HR, 100$\times$, 0.9~NA) è ïîëóñôåðè÷åñêóþ ëèíçó èç ZnSe ìàëîãî ðàçìåðà (äèàìåòð îñíîâàíèÿ 3~ìì). Çà ñ÷åò ýòîãî ñòàíîâèòñÿ âîçìîæíûì ôîêóñèðîâàòü ñâåò íà ïëîñêîé ïîâåðõíîñòè ëèíçû, ÷òî ïîçâîëÿåò ïðîâîäèòü èçìåðåíèÿ îòðàæåíèÿ â ãåîìåòðèè íàðóøåííîãî ÏÂÎ. Ýôôåêòèâíàÿ ÷èñëîâàÿ àïåðòóðà ñèñòåìû ïðè ýòîì âîçðàñòàåò îòíîñèòåëüíî ÷èñëîâîé àïåðòóðû èñïîëüçóåìîãî îáúåêòèâà ïðîïîðöèîíàëüíî ïîêàçàòåëþ ïðåëîìëåíèÿ ZnSe ïîëóñôåðû.  íàøåì ñëó÷àå ýòà âåëè÷èíà ñîñòàâèëà ïðèáëèçèòåëüíî 2.25.
  109. Âàæíûì ïàðàìåòðîì, îïðåäåëÿþùèì ýôôåêòèâíîñòü âîçáóæäåíèÿ (ñèëó ñâÿçè) ìîä îáðàçöà, íàáëþäàåìûõ â ãåîìåòðèè íàðóøåííîãî ÏÂÎ, ÿâëÿåòñÿ âåëè÷èíà âîçäóøíîãî çàçîðà ìåæäó ëèíçîé òâåðäîé èììåðñèè è îáðàçöîì.  ýêñïåðèìåíòå îíà èçìåíÿëàñü ñ ïîìîùüþ ïüåçîïîäâèæêè, ïðèæèìàþùåé îáðàçåö ê ëèíçå (Ðèñ.~\ref{FigExpSetupAndSample}à). Áëàãîäàðÿ ýòîìó, âîçäóøíûé çàçîð êîíòðîëèðîâàëñÿ ñ âûñîêîé òî÷íîñòüþ, è â óñëîâèÿõ ìàêñèìàëüíîãî ïðèæàòèÿ îáðàçöà ê ïðèçìå äîñòèãàë âåëè÷èíû ïîðÿäêà 20~íì, ÷òî îïðåäåëÿëîñü ïóòåì ñðàâíåíèÿ ýêñïåðèìåíòàëüíûõ êàðò îòðàæåíèÿ ñ ÷èñëåííûì ìîäåëèðîâàíèåì.
  110. Äëÿ èññëåäîâàíèÿ çàâèñèìîñòè ôîðìû èçî÷àñòîòíûõ êîíòóðîâ îò äëèíû âîëíû âîçáóæäàþùåãî ïó÷êà ìû èñïîëüçîâàëè èñòî÷íèê ëàçåðíîãî ñóïåðêîíòèíóóìà (Fianium WhiteLase SC400-6), ñîïðÿæåííûé ñ àêóñòîîïòè÷åñêèì ôèëüòðîì Fianium AOTF. Ýòà ñèñòåìà ïîçâîëÿåò ïîëó÷àòü óçêîñïåêòðàëüíûé ëàçåðíûé ïó÷îê ñ ïåðåñòðàèâàåìîé äëèíîé âîëíû â äèàïàçîíå 600-1050 íì, êîòîðûé çàâîäèëñÿ â îïòè÷åñêóþ ñõåìó ÷åðåç íåïîëÿðèçóþùèé äåëèòåëü ïó÷êà (Ðèñ.~\ref{FigExpSetupAndSample}à). ×òîáû îáåñïå÷èòü ñèììåòðè÷íîå ðàñïðåäåëåíèå èíòåíñèâíîñòè ïó÷êà â ïëîñêîñòè âõîäíîãî çðà÷êà îáúåêòèâà, ëàçåðíûé ïó÷îê ïîäâåðãàëñÿ äîïîëíèòåëüíîé ïðîñòðàíñòâåííîé ôèëüòðàöèè ÷åðåç îäíîìîäîâîå îïòè÷åñêîå âîëîêíî. Ñâåò, îòðàæåííûé îò ïëîñêîé ïîâåðõíîñòè èììåðñèîííîé ëèíçû, ðåãèñòðèðîâàëñÿ â êàíàëå ñáîðà îäíîâðåìåííî â ïëîñêîñòè ðåàëüíîãî èçîáðàæåíèÿ è â ïëîñêîñòè, ñîïðÿæåííîé ñ çàäíåé ôîêàëüíîé ïëîñêîñòüþ îáúåêòèâà.
  111. Íà Ðèñ.~\ref{FigGaps} ïðèâåäåíû ïðèìåðû èçîáðàæåíèé çàäíåé ôîêàëüíîé ïëîñêîñòè ñèñòåìû ïðè äëÿ ðàçëè÷íûõ âåëè÷èí âîçäóøíûõ çàçîðîâ ìåæäó ëèíçîé è ïëàíàðíûì êðåìíèåâûì âîëíîâîäîì (210~íì àìîðôíîãî êðåìíèÿ íà ïîäëîæêå èç ïëàâëåíîãî êâàðöà).
  112. Ïðè ïðèáëèæåíèè âîëíîâîäà ê ëèíçå ðàñïðåäåëåíèå èíòåíñèâíîñòè îòðàæåíèÿ â çàäíåé ôîêàëüíîé ïëîñêîñòè ìåíÿåòñÿ. Íà áîëüøîì óäàëåíèè íàáëþäàåòñÿ îáû÷íàÿ êàðòèíà íåâîçìóùåííîãî ÏÂÎ, ïðåäñòàâëÿþùàÿ ñîáîé êîëüöî ñ âíóòðåííèì ðàäèóñîì, ñîîòâåòñòâóþùèì âîëíîâîìó âåêòîðó ñâåòà â âîçäóõå (Ðèñ.~\ref{FigGaps}a). Çàòåì, íà ðàññòîÿíèÿõ ïîðÿäêà íåñêîëüêèõ ìèêðîí â îáëàñòè âíóòðè êîëüöà ÏÂÎ èç-çà èíòåðôåðåíöèè â çàçîðå ìåæäó ëèíçîé è îáðàçöîì íà÷èíàþò íàáëþäàòüñÿ êîëüöà Íüþòîíà (Ðèñ.~\ref{FigGaps}b). Ïðè äàëüíåéøåì óìåíüøåíèè ðàññòîÿíèÿ ïðîÿâëÿåòñÿ ðåæèì íàðóøåííîãî ÏÂÎ, â êîòîðîì íàáëþäàþòñÿ âîëíîâîäíûå ìîäû ñòðóêòóðû (Ðèñ.~\ref{FigGaps}c). Íàêîíåö, íà ðàññòîÿíèÿõ ïîðÿäêà íåñêîëüêèõ äåñÿòêîâ íàíîìåòðîâ âèäíî êîëüöî, ñîîòâåòñòâóþùåå ïîëíîìó âíóòðåííåìó îòðàæåíèþ ìåæäó ZnSe è ïîäëîæêîé (Ðèñ.~\ref{FigGaps}d).
  113. Äëÿ ìîäåëèðîâàíèÿ íàáëþäàåìûõ êàðò îòðàæåíèÿ â çàäíåé ôîêàëüíîé ïëîñêîñòè îïòè÷åñêîé ñèñòåìû ìû èñïîëüçîâàëè ìåòîä ìàòðèö ïåðåíîñà~\cite{abeles1950investigations}.
  114. Ðàñ÷åò ïðîèçâîäèëñÿ îòäåëüíî äëÿ TE-, è TM-ïîëÿðèçîâàííûõ ìîä. Èòîãîâûå êàðòû áûëè ïîëó÷åíû èç ôîðìóëû (1). Ñðàâíåíèå ðåçóëüòàòîâ ìîäåëèðîâàíèÿ äëÿ ïëàíàðíîãî êðåìíèåâîãî âîëíîâîäà (íèæíèé ðÿä Ðèñ.~\ref{FigGaps}) ñ ýêñïåðèìåíòàëüíûìè êàðòèíàìè îòðàæåíèÿ ïîêàçûâàåò îòëè÷íîå ñîîòâåòñòâèå.
  115. \begin{figure}[t]\centering
  116. \includegraphics[width=0.9\linewidth]{FigLambda}
  117. \caption{
  118. \label{FigLambda}
  119. Ðèñ.~\ref{FigLambda}.
  120. Ðàñïðåäåëåíèÿ èíòåíñèâíîñòè îòðàæåíèÿ îò ïëàíàðíîãî êðåìíèåâîãî âîëíîâîäà â çàäíåé ôîêàëüíîé ïëîñêîñòè ñèñòåìû ñ ëèíçîé òâåðäîé èììåðñèè, ïîëó÷åííûå ïðè ôèêñèðîâàííîì âîçäóøíîì çàçîðå ($h_{air}\approx140$~íì) ìåæäó ëèíçîé è îáðàçöîì íà ðàçëè÷íûõ äëèíàõ âîëí. Ïîëÿðèçàöèÿ âîçáóæäàþùåãî èçëó÷åíèÿ îòìå÷åíà ñòðåëêîé íà ïàíåëè (a).
  121. }
  122. \end{figure}
  123. \section{Âîññòàíîâëåíèå äèñïåðñèè âîëíîâîäíûõ ìîä}
  124. Áëàãîäàðÿ òîìó, ÷òî ïðè èçìåðåíèÿõ èñïîëüçîâàëñÿ ëèíåéíî ïîëÿðèçîâàííûé ñâåò, â êàðòàõ îòðàæåíèÿ â çàâèñèìîñòè îò äëèíû âîëíû íàáëþäàëèñü è TE-, è TM-ïîëÿðèçîâàííûå ìîäû (Ðèñ.~\ref{FigLambda}).  ïðîñòåéøåì ñëó÷àå ïëàíàðíîãî âîëíîâîäà äèñïåðñèÿ âîëíîâîäíûõ ìîä íå çàâèñèò îò íàïðàâëåíèÿ èõ ðàñïðîñòðàíåíèÿ, ïîýòîìó èíôîðìàöèþ î íåé ìîæíî ëåãêî èçâëå÷ü èç èçìåðåííûõ êàðòèí îòðàæåíèÿ, ïðîèçâåäÿ ñâåðòêó ðàñïðåäåëåíèÿ ñèãíàëà â çàäíåé ôîêàëüíîé ïëîñêîñòè ñ ôóíêöèåé ðàñïðåäåëåíèÿ ïîëÿðèçàöèè ïàäàþùåé âîëíû. Ôóíêöèÿ ðàñïðåäåëåíèÿ ïîëÿðèçàöèè $\ket{P}$ äëÿ ëèíåéíî ïîëÿðèçîâàííîãî ïó÷êà èìååò ïðîñòóþ ôîðìó
  125. \begin{equation}
  126. \ket{P} = \sin^2(\varphi)\ket{TE} + \cos^2(\varphi)\ket{TM},
  127. \end{equation}
  128. ãäå $\varphi$ - óãîë ìåæäó íàïðàâëåíèåì ïîëÿðèçàöèè ïàðàëëåëüíîãî ïó÷êà çàñâåòêè è ðàäèóñ-âåêòîðîì äàííîé òî÷êè â çàäíåé ôîêàëüíîé ïëîñêîñòè ñèñòåìû. Ýòà çàâèñèìîñòü ïðîèëëþñòðèðîâàíà íà Ðèñ.~\ref{FigExpSetupAndSample}c. Äëÿ íàèáîëåå íàãëÿäíîãî ïðåäñòàâëåíèÿ äèñïåðñèîííûõ êðèâûõ ìû èñïîëüçîâàëè ñëåäóþùåå ïðåîáðàçîâàíèå èçìåðÿåìîãî ñèãíàëà îòðàæåíèÿ $I(\omega,k,\varphi)$:
  129. \begin{equation}
  130. F(\omega, k) = 4\frac{\int_0^{2\pi} I(\omega,k,\varphi) \cos^2(\varphi) \text{d}\varphi}{\int_0^{2\pi} I(\omega,k,\varphi)\text{d}\varphi} - 2.
  131. \end{equation}
  132.  ýòîì ñëó÷àå $F(\omega,k)=0$ ñîîòâåòñòâóåò îòñóòñòâèþ ìîäóëÿöèè ñèãíàëà îòðàæåíèÿ îò óãëà, $F(\omega,k)=1$ ñîîòâåòñòâóåò âîçáóæäåíèþ TM-ïîëÿðèçîâàííîé ìîäû, $F(\omega,k)=-1$ - âîçáóæäåíèþ TE-ïîëÿðèçîâàííîé ìîäû. Ðåçóëüòàòû îáðàáîòêè ýêñïåðèìåíòàëüíûõ äàííûõ îòðàæåíèÿ â çàâèñèìîñòè îò äëèíû âîëíû ïðåäñòàâëåíû íà Ðèñ.~\ref{FigModeMaps}a. ×òîáû âîññòàíîâèòü ñîîòâåòñòâèå ìåæäó íàáëþäàåìûìè ïðîâàëàìè â êàðòàõ îòðàæåíèÿ è ìîäàìè ïëàíàðíîãî âîëíîâîäà, àíàëîãè÷íûì îáðàçîì áûëè îáðàáîòàíû è äàííûå ÷èñëåííîãî ìîäåëèðîâàíèÿ îòðàæåíèÿ. Ðåçóëüòàò îáðàáîòêè ïðèâåäåí íà Ðèñ.~\ref{FigModeMaps}b è ïîêàçûâàåò õîðîøåå ñîîòâåòñòâèå ñ èçìåðåííûìè äàííûìè.  èññëåäóåìîì ñïåêòðàëüíîì äèàïàçîíå êàê â ýêñïåðèìåíòàëüíîé, òàê è â ÷èñëåííîé êàðòàõ $F(\omega, k)$ ÿðêî ïðîÿâëÿþòñÿ äâå âîëíîâîäíûå ìîäû ñ ðàçëè÷íûìè ïîëÿðèçàöèÿìè. Àíàëèòè÷åñêîå ìîäåëèðîâàíèå òàêæå ïîçâîëÿåò îïðåäåëèòü èíäåêñû íàáëþäàåìûõ âîëíîâîäíûõ ìîä, êîòîðûå îáîçíà÷åíû íà Ðèñ.~\ref{FigModeMaps} ïóíêòèðíûìè ëèíèÿìè. Íåáîëüøîå îòëè÷èå ýêñïåðèìåíòàëüíûõ çíà÷åíèé $F(\omega, k)$ îò íóëÿ â îáëàñòè âîëíîâûõ âåêòîðîâ âûøå $1.5k_0$ ñâÿçàíî ñ íåáîëüøîé àíèçîòðîïèåé ðàñïðåäåëåíèÿ èíòåíñèâíîñòè â ïó÷êå çàñâåòêè ïîñëå ïðîñòðàíñòâåííîé ôèëüòðàöèè îïòè÷åñêèì âîëîêíîì. Êðîìå òîãî, îñöèëëÿöèè, íàáëþäàåìûå â âîññòàíîâëåííîì ñèãíàëå íà íèçêî÷àñòîòíîé TM ìîäå, ñâÿçàíû ñ õðîìàòè÷åñêèìè àáåððàöèÿìè îáúåêòèâà, êîòîðûå âîçðàñòàþò ïî ìåðå óäàëåíèÿ îò åãî ðàáî÷åãî ñïåêòðàëüíîãî äèàïàçîíà (400-800~íì).
  133. \begin{figure}[t]\centering
  134. \includegraphics[width=1.0\linewidth]{FigModeMaps}
  135. \caption{
  136. \label{FigModeMaps}
  137. Ðèñ.~\ref{FigModeMaps}.
  138. Äèñïåðñèîííûå çàâèñèìîñòè TE è TM ìîä ïëàíàðíîãî êðåìíèåâîãî âîëíîâîäà, âîññòàíîâëåííûå èç êàðò îòðàæåíèÿ â ïðîñòðàíñòâå âîëíîâûõ âåêòîðîâ èç ýêñïåðèìåíòàëüíûõ äàííûõ (a) è èç ðåçóëüòàòîâ ÷èñëåííîãî ìîäåëèðîâàíèÿ ìåòîäîì ìàòðèö ïåðåíîñà (b) äëÿ âåëè÷èíû âîçäóøíîãî çàçîðà 140~íì.
  139. }
  140. \end{figure}
  141. \section{Çàêëþ÷åíèå}
  142. Òàêèì îáðàçîì, â íàøåé ðàáîòå ìû ïðîäåìîíñòðèðîâàëè âîçìîæíîñòè óñòàíîâêè ìèêðîñêîïèè çàäíåé ôîêàëüíîé ïëîñêîñòè, â êîòîðîé â êà÷åñòâå îñíîâíîãî îïòè÷åñêîãî ýëåìåíòà âûñòóïàåò âûñîêîàïåðòóðíûé îáúåêòèâ, ñîâìåùåííûé ñ ëèíçîé òâåðäîé èììåðñèè, äëÿ âèçóàëèçàöèè èçî÷àñòîòíûõ êîíòóðîâ ëîêàëèçîâàííûõ ñîñòîÿíèé â ïëàíàðíûõ ñòðóêòóðàõ.  îòëè÷èå îò ñòàíäàðòíûõ ìåòîäîâ íàáëþäåíèÿ ïîâåðõíîñòíûõ âîëí ìåòîäîì ñïåêòðîñêîïèè îòðàæåíèÿ â ãåîìåòðèè íàðóøåííîãî ïîëíîãî âíóòðåííåãî îòðàæåíèÿ, òàêàÿ óñòàíîâêà ïîçâîëÿåò îäíîâðåìåííî ïîëó÷àòü èíôîðìàöèþ î õàðàêòåðèñòèêàõ ïîâåðõíîñòíûõ ñîñòîÿíèé èëè âîëíîâîäíûõ ìîä, ðàñïðîñòðàíÿþùèõñÿ âî âñåõ íàïðàâëåíèÿõ. Ïðè ýòîì ýôôåêòèâíûå ïîêàçàòåëè ïðåëîìëåíèÿ íàáëþäàåìûõ ëîêàëèçîâàííûõ ñîñòîÿíèé ìîãóò äîñòèãàòü çíà÷åíèé 2.25 â âèäèìîì ñïåêòðàëüíîì äèàïàçîíå ïðè èñïîëüçîâàíèè ëèíçû èç ñåëåíèäà öèíêà, ÷òî äàåò ðåøàþùåå ïðåèìóùåñòâî â ñðàâíåíèè ñ ñèñòåìàìè ñ æèäêîé èììåðñèåé. Ðàçðàáîòàííàÿ óñòàíîâêà ïðåäëàãàåòñÿ êàê óíèâåðñàëüíûé èíñòðóìåíò äëÿ ýêñïåðèìåíòàëüíîé õàðàêòåðèçàöèè ëîêàëèçîâàííûõ ñîñòîÿíèé â áóðíî ðàçâèâàþùåìñÿ íàïðàâëåíèè ïëàíàðíîé ôîòîíèêè è ìåòàïîâåðõíîñòåé.
  143. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  144. %% Acknowledgements
  145. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  146. Ýêñïåðèìåíòàëüíûå èçìåðåíèÿ áûëè âûïîëíåíû ïðè ôèíàíñîâîé ïîääåðæêå Ðîññèéñêîãî íàó÷íîãî ôîíäà (ãðàíò \# 15-12-20028). ×èñëåííûé ðàñ÷åò áûë âûïîëíåí ïðè ôèíàíñîâîé ïîääåðæêå ÐÔÔÈ (ãðàíò \#17-02-01234).
  147. %Ðàáîòû áûëè âûïîëíåíû ïðè ôèíàíñîâîé ïîääåðæêå Ðîññèéñêîãî íàó÷íîãî ôîíäà (ãðàíò \# 15-12-20028).
  148. %Àâòîðû âûðàæàþò áëàãîäàðíîñòü Èâàíó Ìóõèíó çà ïðåäîñòàâëåíèå îáðàçöîâ ïëàíàðíûõ êðåìíèåâûõ âîëíîâîäîâ.
  149. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  150. %% References
  151. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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