Mathematics and Computers in Simulation 69 (2005) 378–388 Optical solitons in a few-cycle regime: Breakdown of slow-envelope approximation Herv´ e Leblond a, ∗ , F. Sanchez a , I.V. Mel’nikov b,c, 1 , D. Mihalache d,e a Laboratoire P.O.M.A., U.M.R., C.N.R.S. 6136, Universit´ e d’Angers, 2 blvd. Lavoisier, 49045 Angers Cedex 01, France b The E.S. Rogers Sr Department of Electrical and Computer Engineering, University of Toronto, 10 King’s College Road, Toronto, Ont., Canada M5S 3G4 c A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences, ul. Vavilova 38, Moscow 119991, Russian Federation d Department of Theoretical Physics, Institute of Atomic Physics, P.O. Box MG-6, Bucharest, Romania e Institut f ¨ ur Festk¨ orpertheorie und Theoretische Optik der Friedrich Schiller-Universit¨ at Jena, Max-Wien-Platz 1, D-07743 Jena, Germany Available online 9 March 2005 Abstract The propagation of few-cycles optical pulses in a collection of two-level atoms is investigated beyond the tra- ditional slowly varying envelope approximation. It is shown that in certain conditions, a femtosecond pulse can evolve into a stable spatiotemporal optical soliton. © 2005 IMACS. Published by Elsevier B.V. All rights reserved. Keywords: Optical pulses; Few-cycle; Optical solitons; Spatiotemporal optical solitons 1. Introduction The recent progress in the development of solid-state mode-locked lasers has resulted in the generation of two-cycle optical pulses [1]. Subsequently, such short pulses have been widely exploited to generate a ∗ Corresponding author. Tel.: +33 241735386; fax: +33 241735216. E-mail addresses: herve.leblond@univ-angers.fr (H. Leblond), igor.melnikov@utoronto.ca (I.V. Mel’nikov). 1 Tel.: +1 416 9465524; fax: +1 416 9713020. 0378-4754/$30.00 © 2005 IMACS. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.matcom.2005.01.011