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50 Ans De Découvertes n°21 octobre 2010 Société Française de Physique www.sfpnet.fr www.refl etsdelaphysique.fr Revue de la Le laser 50 ans de découvertes N° 927 LeOctobre 2010 Bup Physique Chimie UNION DES PROFESSEURS DE PHYSIQUE ET DE CHIMIE 42, rue Saint-Jacques - 75005 PARIS www.udppc.asso.fr Éditorial L’UdPPC et la SFP célèbrent ensemble le cinquantenaire de la découverte du laser Le Laser a 50 ans. Suite à la première démonstration d’un effet laser par Theodore Maiman en mai 1960, et en dépit de prédictions hâtives (« le laser, une solution à la recherche de son problème »), les lasers ont connu un développement exponentiel : les sources se sont multipliées dans tous les domaines de longueur d’onde, de l’infrarouge lointain aux rayons X durs, établissant des records de monochromaticité, cohérence spatiale et pureté spectrale, de durée ultra-courte d’impulsions lumineuses, de puissance, d’énergie… Leurs applications ont été multiples en recherche fondamentale (physique, chimie, etc.), dans l’industrie, dans les télécommunications, en métrologie, en biologie et médecine… À cause de ces nombreuses applications, le laser est devenu un élément de notre vie quotidienne. En tant que source lumineuse quasi idéale, il a aussi révolutionné l’enseignement des sciences physiques et de l’optique. Pour célébrer les 50 ans du laser, présenter les récentes avancées et décrire son impact dans les sciences physiques et ses nombreuses applications dans les autres disciplines, la Société française de physique et l’Union des professeurs de physique et de chimie ont uni leurs forces pour publier un numéro spécial commun de leurs revues respectives, Refl ets de la physique et Le Bulletin de l’Union des Professeurs de physique et de chimie. La lecture de son sommaire montre la diversité des thèmes abordés. Il faut souligner que la présente publication s’inscrit dans un ensemble d’initiatives communes prises par nos deux sociétés depuis de nombreuses années. En juin 2005, à l’occasion de l’Année mondiale de la physique, la SFP et l’UdPPC avaient publié en commun un numéro hors série du Bup et du Bulletin de la Société française de physique, ancêtre des Refl ets de la physique. Ce numéro mettait en relief quelques-uns des champs d’activité des physiciens d’aujourd’hui et leurs liens avec les disciplines les plus diverses. Édouard Brézin, alors vice-président de la SFP, soulignait dans la préface que cette publication témoignait de « la vitalité de la physique contemporaine, la diversité de ses objets d’étude, la richesse de ses contacts avec d’autres disciplines ». Madeleine Sonneville, présidente de l’UdPPC, soulignait de son côté, « l’importance de tels documents pour la culture scientifi que des professeurs ». Si cette publication commune était une « première » dans le domaine éditorial, elle ne représentait pas la première action commune des deux associations. Les lecteurs assidus de nos bulletins se rappellent sûrement qu’en 1986 avait pris naissance une commission mixte UdPPC-SFP sur l’enseignement. Elle a poursuivi ses travaux pendant de longues années, mais fut surtout le lieu d’élaboration du projet des Olympiades de Physique France. Celui-ci vit le jour en septembre 1991, lors du congrès général de la SFP à Caen. Les deux sociétés, cofondatrices des Olympiades, en sont aussi les coorganisatrices, et les deux revues se font chaque année l’écho du concours. Au-delà de cet exemple, notre volonté de collaboration est constamment réaffi rmée et elle trouve en particulier à s’illustrer par des échanges réguliers entre les associations, par des articles publiés en commun et aussi (trop souvent, malheureusement…) chaque fois que sont malmenées les conditions faites à l’enseignement des sciences au lycée. Nos remerciements s’adressent à tous les auteurs qui ont accepté de contribuer, et aux équipes de rédaction qui se sont coordonnées pour mener à bien ce projet ambitieux, afi n d’aboutir à ce beau numéro que nous sommes heureux de vous présenter et qui devrait faire référence. Micheline Izbicki Martial Ducloy Présidente de l’UdPPC Président de la SFP 2 Refl ets de la Physique n° 21 / Le Bup n° 927 Sommaire 2 Éditorial Micheline Izbicki et Martial Ducloy 4 Le laser : 50 ans de dialogue entre science et applications Fabien Bretenaker 6 Glossaire et bibliographie Histoire et principe des lasers 10 Souvenirs de la genèse du laser Charles H. Townes 12 Le laser : principe de fonctionnement p. 9 Catherine Schwob et Lucile Julien Le laser, 50 ans de découvertes 18 Les différents lasers : un tour d’horizon Sébastien Forget, Isabelle Robert-Philip et Philippe Balcou Les lasers de l’extrême 26 Les nanolasers, vers une nouvelle physique des lasers ? Izo Abram, Alexios Beveratos et Isabelle Robert-Philip 30 Sources cohérentes de laboratoire dans l’extrême ultraviolet Thierry Ruchon, Pascal Salières, Philippe Zeitoun et Stéphane Sebban 35 La fusion thermonucléaire par laser Michel Decroisette p. 25 Mesures de grande précision 42 Des lasers à impulsions femtosecondes pour mesurer les fréquences Anne Amy-Klein 46 Atomes froids : réseaux optiques et horloges Michèle Leduc et Pierre Lemonde 53 Le laser : un outil de choix pour l’interférométrie atomique Arnaud Landragin et Franck Pereira Dos Santos Quelques exemples d’application des lasers 60 La cohérence de la lumière et l’imagerie des tissus du corps humain A. Claude Boccara p. 41 65 Applications médicales du laser Serge Mordon 70 Des lasers pour les télécommunications optiques par fi bres Mehdi Alouini 76 Les lidars atmosphériques Jean-Pierre Cariou et Laurent Sauvage 83 Deux exemples d’applications industrielles des lasers Philippe Aubourg, François Fariaut, Patrick Mauchien et François Salin 89 Faire de la physique autour des fontaines lasers Sébastien Forget, Christophe Daussy et Paul-Éric Pottie p. 59 REFLETS DE LA PHYSIQUE LE BUP PHYSIQUE-CHIMIE POUR CE NUMÉRO Directeur de la publication : Mohamed DAOUD Directeur de la publication : Micheline IZBICKI Responsable scientifique : Fabien BRETENAKER Rédacteur en chef : Charles de NOVION Rédacteur en chef : Gérard DUPUIS Secrétaire de rédaction : Catherine FRANÇOIS Comité de rédaction : P. BASSEREAU - M. BELAKHOVSKY - Comité de rédaction : G. BOUYRIE - L. DETTWILLER - Graphiste : [email protected] F. CASOLI - A. DAVAILLE - É. GUYON - P. HENNEQUIN - J.-P. HULIN - D. LAUNER - B. VELAY - J. WINTHER Imprimé en France par SPEI – 54425 Pulnoy Laser accordable : S. LABROSSE - G. LANDA - R. LEHOUCQ - J. MARGUERON - V. MOSSER - Service publicité : [email protected] Dépôt légal : 4e trimestre 2010 S. REMY - C. SÉBENNE - J. TEIXEIRA - J. VANNIMENUS - C. YÈCHE Serveur : www.udppc.asso.fr Édité à 7500 exemplaires superposition Service publicité : [email protected] Numéro commission paritaire : 0110G85858 © SFP / UdPPC de poses sur Serveur : www.refletsdelaphysique.fr ISSN : 1770-1368. Prix du numéro : 10 €. ISSN : 1953-793X – e-ISSN : 2102-1777 Publication mensuelle - 104e année la même image 5 numéros par an Annonceurs : (LCFIO, Orsay). Dunod (p. 17), Yenista (p. 52), Laser Quantum Société Française de Physique Union des professeurs de physique et de chimie (p. 52), Quantel (p. 52), TEEM Photonics (p. 64), © CNRS Photothèque / 33, rue Croulebarbe, 75013 Paris 42, rue Saint-Jacques, 75005 Paris Alphanov (p. 88), CNRS/LCMI (p. 88), Kircheim EQUILBEY Serge. www.sfpnet.fr www.udppc.asso.fr optique (p. 88). Refl ets de la Physique n° 21 / Le Bup n° 927 3 Le laser : 50 ans de dialogue entre science et applications Un des objectifs de nos deux revues, Refl ets de la physique et Le Bup physique-chimie, est de présenter à leurs lecteurs les avancées récentes de la recherche en sciences de la matière. En cette année 2010, anniversaire des 50 ans de la découverte du laser, l’UdPPC et la SFP ont pris la décision de réaliser en commun ce numéro spécial sur le laser. Fabien Bretenaker, directeur de recherche au CNRS et professeur chargé de cours à l’École polytechnique, a accepté Il y a cinquante ans, Ted Maiman mettait au point le premier d’en prendre la direction scientifi que. Il nous présente « MASER optique », qui sera ensuite rebaptisé « LASER ». Après ici l’organisation de ce numéro commun, qui comprend la découverte du maser dans le domaine micro-ondes par Townes quinze articles scientifi ques, répartis en quatre parties. en 1954, plusieurs équipes de physiciens s’étaient lancées dans la Après un rappel des notions de base sur le laser, on y traite quête de ce Graal. Charles Townes lui-même a accepté de nous de certaines des avancées les plus récentes, aussi bien en livrer ses souvenirs de cette épopée. Cela constitue le premier recherche fondamentale que dans les applications. article de ce numéro spécial, commun aux Refl ets de la physique et Nous le remercions pour avoir mené à bien ce projet. au Bulletin de l’Union des Professeurs de physique et de chimie. Un grand merci également à Jean-Pierre Hulin, à qui l’on doit une analyse approfondie des articles, et à Catherine François Initialement simple objet de curiosité pour les physiciens, le laser et Laetitia Morin, qui se sont chargées avec enthousiasme et est, cinquante ans plus tard, tellement présent dans notre quotidien compétence de son édition et de sa mise en forme. que nous ne le remarquons quasiment plus. Au même titre que le transistor, il peut être considéré comme une des réussites majeures Gérard Dupuis Charles de Novion de la physique du XX e siècle, dont se sont emparés tous les domaines Rédacteur en chef du Bup physique-chimie Rédacteur en chef de Refl ets de la physique de la recherche et de l’innovation. Faire un tour d’horizon un tant soit peu exhaustif de ce domaine est devenu impossible. Aussi avons-nous choisi ici de nous limiter, en faisant appel à la plume de plusieurs des meilleurs spécialistes, à quelques exemples regroupés en quatre parties.
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