Electrically controlled lateral shift of the reflected optical beams from a nanocomposite structurally chiral medium Simin Shirin 1 , Amir Madani 1 and Samad Roshan Entezar 2 1 Department of Laser and Optical Engineering, University of Bonab, Bonab, Iran 2 Faculty of Physics, University of Tabriz, Tabriz, Iran E-mail: a-madani@ubonab.ac.ir Received 26 May 2020, revised 23 July 2020 Accepted for publication 3 August 2020 Published 12 August 2020 Abstract In this paper, we theoretically investigate the influence of an external electric field on the lateral shifts of the reflected right-handed circularly polarized beam from a nanocomposite slab at the edge wavelengths of the photonic bandgaps of the structure. The nanocomposite slab is a non-dissipative dielectric chiral material with the randomly dispersed silver nanoparticles inside it. We show that the increase of the applied electric field results in the decrease of the positive lateral shift at the lower edge of the Bragg gap, while the negative lateral shift at the upper edge of the Bragg gap increases by increasing the applied field. Moreover, we show that the impact of the applied voltage is more noticeable at larger incident angles for both the lower and upper edge wavelengths of the Bragg gap. Also, it is shown that the tilt angle of the chiral structure and the slab thickness have considerable effects on the controlling behavior of the externally applied voltage. Finally, we investigate the effect of the filling fraction of nanoparticles and show that the inclusion of the nanoparticles can change the influence of the applied voltage on the lateral shift of the reflected beams. Keywords: Nanocomposite, lateral shift, structurally chiral medium, optical beam (Some figures may appear in colour only in the online journal) 1. Introduction Nonspecular reflection phenomena express that the optical beams don’t always follow the well-known Snell law and Fresnel formula. They will shift from the position predicted by the geometrical optics when impinging at the boundary of two different media under total internal reflection. This opti- cal phenomenon, which is defined as the Goos-Hanchen (GH) effect, was observed experimentally by Goos and Hanchen for the first time in 1947 [1] and afterward was explained theoretically by Artmann in 1948 [2]. Later, the study of the lateral shift has been generalized to the partial reflection and transmission [3–5]. The investigations showed that the GH effect might have potential applications in optical sensors [6–9] optical switching [10], detection of chemical vapors [11], polarizers [12], lasers [13], filters [14] and integrated optics [15]. The major positive and negative GH shifts for both transmitted and reflected beams were reported in the multilayer structures [16–19], photonic crystals [20–22], left- handed materials [23–26], antiferromagnet [27], metamater- ials [28, 29], nonabsorbent or absorbing media [30–32], photonic-magnonic crystals [33]. The tunability and switch- ing properties of the lateral shift are very significant in the application of the GH effect and have been investigated extensively by several researchers. Wang et al studied the adjustability of the lateral shift using a coherent driving field in two-level atoms [34]. Fan et al reported the tunability of the lateral shift in the THz region for graphene-based systems [35]. Also, the ability to adjust the GH shift by tuning the chemical potential of graphene on a photonic crystal con- taining graphene monolayers has been theoretically investi- gated [36]. Matthews et al investigated the tunable GH shift for two-dimensional photonic crystals [37]. Luo et al have studied the control of the lateral shift by adjusting an external Physica Scripta Phys. Scr. 95 (2020) 095504 (10pp) https://doi.org/10.1088/1402-4896/ababc5 0031-8949/20/095504+10$33.00 © 2020 IOP Publishing Ltd Printed in the UK 1