{"id":2881,"date":"2024-03-04T10:14:37","date_gmt":"2024-03-04T09:14:37","guid":{"rendered":"http:\/\/s848664668.onlinehome.fr\/Wordpress\/?p=2881"},"modified":"2025-12-21T16:20:59","modified_gmt":"2025-12-21T15:20:59","slug":"laser-a-fibre-picoseconde-0-5-10-ps","status":"publish","type":"post","link":"https:\/\/www.swissrocketman.fr\/Wordpress\/?p=2881","title":{"rendered":"LASER A FIBRE PICOSECONDE 0.5-10 ps"},"content":{"rendered":"
Ce laser femtoseconde \u00e0 blocage de mode passif model\u00a0CALMAR LASERS FPL-M2UFFLUM22<\/b><\/i>, utilise un semi-conducteur \u00e0 absorption saturable SESAM (miroir 125) et comme m\u00e9dium amplificateur une fibre dop\u00e9e \u00e0 l’Ytterbium(130) qui est pomp\u00e9e par une diode laser \u00e0 970nm.(150)
\nUn des miroir du r\u00e9sonateur se compose r\u00e9seau de diffraction holographique(112) et il permet de changer la fr\u00e9quence de sortie des pulses lasers entre 1030 et 1065 nm.
\nCe module est une architecture insensible aux vibrations et aux chocs et il pr\u00e9sente une stabilit\u00e9 exceptionnelle et une fiabilit\u00e9 maximum et ceci sans aucun r\u00e9glage !
\nLa dur\u00e9e de pulse peut \u00eatre pr\u00e9cis\u00e9 \u00e0 la fabrication entre 500fs et 5ps selon l’architecture de la fibre (longueur de celle-ci).<\/h5>\n<\/div><\/section><\/div>\n
<\/div><\/div><\/div><\/div>\n
<\/div><\/div><\/div><\/div>\n
<\/div><\/div><\/div><\/div>\n
<\/div><\/div><\/div><\/div>\n
<\/div><\/div><\/div><\/div>\n
<\/div><\/div><\/div><\/div>\n
<\/div><\/div><\/div><\/div>\n
<\/div><\/div><\/div><\/div>\n

2. Le principe du mode-locking<\/strong> (verrouillage de modes)<\/h2>\n

Pour g\u00e9n\u00e9rer des impulsions femtoseconde, il faut forcer tous les modes longitudinaux<\/strong> \u00e0 osciller en phase fixe les uns avec les autres<\/strong>.<\/p>\n

Lorsque ces modes sont verrouill\u00e9s en phase<\/em>, leurs interf\u00e9rences constructives cr\u00e9ent un train d\u2019impulsions ultracourtes<\/strong> dans le temps.<\/p>\n

Visuellement :<\/p>\n

    \n
  • \n

    En domaine fr\u00e9quentiel : large spectre (plusieurs modes coh\u00e9rents)<\/p>\n<\/li>\n

  • \n

    En domaine temporel : impulsions br\u00e8ves et r\u00e9p\u00e9titives.<\/p>\n<\/li>\n<\/ul>\n

    \n

    3. Comment le verrouillage est obtenu dans un laser \u00e0 fibre Calmar<\/h2>\n

    Les lasers Calmar (comme le FPL-M2U<\/strong>) utilisent g\u00e9n\u00e9ralement un mode-locking passif<\/strong>, via un composant non lin\u00e9aire dans la fibre :<\/p>\n

    a) Absorbeur saturable<\/strong> (SA)<\/h3>\n

    Un absorbeur saturable<\/strong> (souvent un SESAM ou un mat\u00e9riau \u00e0 base de nanotubes de carbone ou graph\u00e8ne) laisse passer pr\u00e9f\u00e9rentiellement les cr\u00eates d\u2019intensit\u00e9 lumineuse :<\/p>\n

      \n
    • \n

      Faible intensit\u00e9 \u2192 absorption importante<\/p>\n<\/li>\n

    • \n

      Forte intensit\u00e9 \u2192 transmission accrue<\/p>\n<\/li>\n<\/ul>\n

      Ce m\u00e9canisme favorise la formation spontan\u00e9e d\u2019une impulsion stable, qui se renforce tour apr\u00e8s tour dans la cavit\u00e9.<\/p>\n

      b) Nonlinear Polarization Evolution (NPE)<\/strong><\/h3>\n

      Certains mod\u00e8les utilisent aussi le NPE<\/strong> :<\/p>\n

        \n
      • \n

        La polarisation de la lumi\u00e8re varie avec l\u2019intensit\u00e9 (effet Kerr)<\/p>\n<\/li>\n

      • \n

        Un polariseur intracavit\u00e9 s\u00e9lectionne les composantes de forte intensit\u00e9 \u2192 seule l\u2019impulsion survive.<\/p>\n<\/li>\n<\/ul>\n

        Dans les lasers Calmar, c\u2019est souvent NPE + fibre non lin\u00e9aire<\/strong> + isolateur\/polariseur<\/strong>.<\/p>\n

        4. \u00c9quilibre entre dispersion et non-lin\u00e9arit\u00e9<\/h2>\n

        Une impulsion femtoseconde dans la fibre subit :<\/p>\n

          \n
        • \n

          Dispersion<\/strong> (\u00e9talement temporel des fr\u00e9quences)<\/p>\n<\/li>\n

        • \n

          Auto-modulation de phase (SPM)<\/strong> due \u00e0 l\u2019indice non lin\u00e9aire n2n_2<\/span>n<\/span>2<\/span><\/span><\/span>\u200b<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/p>\n<\/li>\n<\/ul>\n

          Le laser est con\u00e7u pour que ces deux effets s\u2019\u00e9quilibrent partiellement :<\/p>\n

          Dispersion\u00a0(e\u02catalement)\u2194Non-line\u02caarite\u02ca\u00a0(compression)\\text{Dispersion (\u00e9talement)} \\leftrightarrow \\text{Non-lin\u00e9arit\u00e9 (compression)}<\/span>Dispersion\u00a0(<\/span>e<\/span>\u02ca<\/span><\/span><\/span><\/span><\/span><\/span>talement)<\/span><\/span>\u2194<\/span><\/span>Non-lin<\/span>e<\/span>\u02ca<\/span><\/span><\/span><\/span><\/span><\/span>arit<\/span>e<\/span>\u02ca<\/span><\/span><\/span><\/span><\/span><\/span>\u00a0(compression)<\/span><\/span><\/span><\/span><\/span><\/span><\/p>\n

          \u2192 Cela conduit \u00e0 la formation d\u2019un soliton optique<\/strong> stable dans la fibre.<\/p>\n

          C\u2019est ce qu\u2019on appelle un soliton mode-locked fiber laser<\/strong>.<\/p>\n

          \n

          5. R\u00e9sultat final<\/h2>\n
            \n
          • \n

            Tous les modes longitudinaux sont verrouill\u00e9s en phase (\u0394\u03c6 = constante)<\/p>\n<\/li>\n

          • \n

            Le spectre de sortie est large (plusieurs THz)<\/p>\n<\/li>\n

          • \n

            En domaine temporel : impulsions de 100 fs \u00e0 500 fs<\/strong>, \u00e0 des fr\u00e9quences de r\u00e9p\u00e9tition de ~50\u2013100 MHz<\/strong><\/p>\n<\/li>\n

          • \n

            Sortie via une fibre monomode<\/strong> (souvent PM fiber)<\/p>\n<\/li>\n<\/ul>\n<\/div><\/section><\/div>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":1,"featured_media":2884,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6],"tags":[],"class_list":["post-2881","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-lasers-a-solides"],"_links":{"self":[{"href":"https:\/\/www.swissrocketman.fr\/Wordpress\/index.php?rest_route=\/wp\/v2\/posts\/2881","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.swissrocketman.fr\/Wordpress\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.swissrocketman.fr\/Wordpress\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.swissrocketman.fr\/Wordpress\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.swissrocketman.fr\/Wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2881"}],"version-history":[{"count":13,"href":"https:\/\/www.swissrocketman.fr\/Wordpress\/index.php?rest_route=\/wp\/v2\/posts\/2881\/revisions"}],"predecessor-version":[{"id":4064,"href":"https:\/\/www.swissrocketman.fr\/Wordpress\/index.php?rest_route=\/wp\/v2\/posts\/2881\/revisions\/4064"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.swissrocketman.fr\/Wordpress\/index.php?rest_route=\/wp\/v2\/media\/2884"}],"wp:attachment":[{"href":"https:\/\/www.swissrocketman.fr\/Wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2881"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.swissrocketman.fr\/Wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2881"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.swissrocketman.fr\/Wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2881"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}