Femtosecond pulse compression in a hollow-core photonic bandgap fiber by tuning its cross section N. Gonza ´lez-Baquedano a, * , N. Arzate a , I. Torres-Go ´mez a , A. Ferrando b , D.E. Ceballos-Herrera b,1 , C. Milia ´n c a Centro de Investigaciones en O ´ ptica A.C., Loma del Bosque 115, Lomas del Campestre, 37150, Leo ´n, Guanajuato, Mexico b Departamento de O ´ ptica, Universidad de Valencia, Dr. Moliner 50, Burjassot 46100, Valencia, Spain c Instituto de Instrumentacio ´n para Imagen Molecular (I3M), InterTech, Universidad Polite ´cnica de Valencia, Camino de Vera S/N 46022, Valencia, Spain Received 3 February 2012; received in revised form 5 May 2012; accepted 8 May 2012 Available online 19 May 2012 Abstract We present a numerical study of soliton pulse compression in a seven-cell hollow-core photonic bandgap fiber. We analyze the enhancement of both the compression factor and the pulse shape quality of 360 nJ femtosecond pulses at the wavelength of 800 nm by tuning the cross section size of the fiber. We use the generalized non-linear Schro ¨dinger equation in order to modeled the propagation of light pulses along the fiber. Our numerical results show that output compressed pulses can be obtained, in a propagation length of 31 cm, with a compression factor of 5.7 and pulse shape quality of 77% for a reduction of 4.5% of the cross section size of the fiber. The predicted compression factor is 3 times larger than that experimentally obtained in such propagation length of the pulse in a hollow-core photonic bandgap fiber. # 2012 Elsevier B.V. All rights reserved. MSC : 78A60; 78A25 Keywords: Hollow-core fiber; Pulse compression; Soliton 1. Introduction Non-linear optical effects in hollow-core photonic bandgap fibers (HC-PBGFs) are an active research topic [1]. These fibers allow the propagation of light in an air core and have the property that their guided modes are only permitted for a range of wavelengths that are within the photonic bandgap of the cladding. Recently, HC-PBGFs have been used to deliver and compress high-intensity pulses due to the nature of their air core, which presents low non-linearity. These characteristics make HC-PBGFs efficient non-linear tools to be used as soliton fiber compressors [2,3]. In these fibers optical pulses propagate in the anomalous group velocity dispersion (GVD) regime of the fiber, in such a way compression takes place due to an interplay between the effects of self-phase modulation (SPM) and GVD. The compression factor depends on the peak power of the pulse which, in turn, determines the soliton order [4]. www.elsevier.com/locate/photonics Available online at www.sciencedirect.com Photonics and Nanostructures – Fundamentals and Applications 10 (2012) 594–601 * Corresponding author. Tel.: þ52 477 441 4200; fax: þ52 477 441 4209. E-mail address: noegb@cio.mx (N. Gonza ´lez-Baquedano). 1 Present address: Universidad Auto ´noma de Nuevo Leo ´n, Facultad de Ciencias Fı ´sico Matema ´ticas (FCFM), CICFIM, Av. Universidad s/n, Cd. Universitaria, San Nicolas de los Garza, 66451, Nuevo Leo ´n, Me ´xico. 1569-4410/$ – see front matter # 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.photonics.2012.05.007