Optik - International Journal for Light and Electron Optics 227 (2021) 166093 Available online 2 December 2020 0030-4026/© 2020 Elsevier GmbH. All rights reserved. Original research article Coupled propagation of two beams in cubic quintic nonlinear medium Ram Krishna Sarkar *, Manoj Kumar Dutta Department of Physics, Birla Institute of Technology (Mesra), Off-Campus Deoghar, Jasidih, Deoghar, 814142, India A R T I C L E INFO Keywords: Spatial soliton pair Breather pair Cubic quantic nonlinear medium ABSTRACT In this paper, coupled propagation of two beams in cubic quintic nonlinear medium has been investigated. We have presented a complete understanding of spatial soliton pair formation, breather pair formation and their existence curves, for different coupling coeffcients and also for different beam width of the co-propagating beams. 1. Introduction Cubic quintic nonlinear medium has immersed a lot of interest [1–10] due to very fast time response, saturating kind of nonlin- earity, negligible multi-photon absorption and low linear loss. Cubic quintic Schr¨ odinger equation has also attracted growing importance [11–15] due to correct model to explicate the propagation of envelope of light pulse in double doped optical fber [16] and for the dynamics of induced modulational instability [17]. Kerr medium is the appearance of low nonlinear coeffcients and most of the research interest on solitons is usually restricted to Kerr medium. However, higher order nonlinearities become important at moderate intensities in materials with high nonlinear susceptibilities. The refractive index in the cubic quintic nonlinear medium is defned by; n=n 0 +n 2 E 2 +n 4 E 4 +– – – –, where, n 2 = 3χ (3) /(8n 0 ) and n 4 = 5χ (5) /(32n 0 ). χ (3) , χ (5) being the components of corresponding nonlinear dielectric tensors and n 0 being the linear refractive index coeffcient. In general, n 2 and n 4 are having same sign, but, sign of n 2 and n 4 may also be opposite. If sign of n 2 and n 4 are opposite, then new interesting phenomena may come out. Coupled spatial soliton pairs in nonlinear media are vital in all-optical switching devices [18–22], and therefore, such pairing has always been discussed in many research papers [23–30]. Recently, quadratic-cubic nonlinearity has also engrossed growing signifcance [31–34]. Very recent studies in this feld are reported in the references [35–39]. In the present paper, we have extended the work of reference [30] to provide thorough understanding of coupled propagation including formation of spatial soliton pairs, breather pairs and their existence curves for different coupling coeffcients, and also for different beam width of the co-propagating beams. 2. Mathematical model and numerical analysis The intensity distributions of two Gaussian beams along the propagation distance could in general be expressed as; E 2 1 = E 2 01 f 2 1 exp {   r 2 / r 2 1 f 2 1 )} (1) * Corresponding author. E-mail address: ramkrishnabit@gmail.com (R.K. Sarkar). Contents lists available at ScienceDirect Optik journal homepage: www.elsevier.com/locate/ijleo https://doi.org/10.1016/j.ijleo.2020.166093 Received 9 November 2020; Received in revised form 30 November 2020; Accepted 30 November 2020