Contents lists available at ScienceDirect Optics and Laser Technology journal homepage: www.elsevier.com/locate/optlastec Multi-channel photonic bandgap engineering in hyperbolic graded index materials embedded one-dimensional photonic crystals Bipin K. Singh a,b,⁎ , Vaishali Bambole a , Vipul Rastogi b , Praveen C. Pandey c a Department of Physics, University of Mumbai, Mumbai 400 032, India b Department of Physics, Indian Institute of Technology Roorkee, 247667, India c Department of Physics, Indian Institute of Technology (BHU), Varanasi 221005, India HIGHLIGHTS • Structuring of hyperbolic graded index materials in the form of 1-D PC have investigated. • Study the efect of graded materials on multi-channel PBG sensing performances. • Number of PBG sensing channels increases with increasing the layer thickness. • Operational frequencies of PBG channels can be tuned by changing grading parameters. • Proposed GPCs can be implemented to design multi-channel PBG sensors/flters. ARTICLE INFO Keywords: Graded photonic crystals Photonic band gap Refectors Muti-channel PBG sensors ABSTRACT Engineering of multi-channel photonic band gap sensing consequences has been demonstrated in hyperbolic graded index materials embedded one-dimensional (1-D) photonic crystal (PC) in the frequency 150–850 THz region. The multi-channel photonic band gap sensing properties have been investigated by taking into account the refection and photonic band gap (PBG) spectra of the proposed PC structures. For quarter-wave stacking, we obtain single optical refection band for band region 646.8 – 434.3 THz with the constituted normal layer refractive index 1.5. Band regions and bandwidths of the single PBG channel can be modulated by changing the refractive index of the constituted normal layer and grading parameter of the hyperbolic graded layer. The number of photonic bands increases with increasing the layer thickness of the GPC structures and leads to work as multi-channel PBG sensors. The operation frequency of the multi-channel PBG sensors can also be tuned by changing the constituted normal layer and grading parameter of the hyperbolic graded layer. These properties lead to design the tunable multi-channel optical sensors/flters engineering. Moreover, the demonstration of the refection phase shift, group velocity, group delay, and electric feld distributions shows the efect of hyperbolic graded index materials on the propagation of light in 1-D PCs. With the engineering of tunable PBGs and structure controllability, hyperbolic graded index materials embedded 1-D PCs provide a promising way to fabricate tunable optical refectors and multi-channel optical sensors/flters for future optical devices. 1. Introduction The importance of light trapping and controlling for diferent pho- tonic application prospects has been extensively motivated the en- gineering of photonic crystal (PC) structures [1–3],[4]. Various struc- tural confgurations and engineering have been investigated to control and trap light in PC structures and to improve the performance of photonic devices [5,6,7,8,9,10]. From diferent structural confgura- tions and perspectives, the concept of graded index optics in PC structures is quite a new strategy and has been extensively attracted the attention of researcher aimed at enhancing their performance to control and manipulate the propagation of light and engineering of photonic band gap (PBG). The diferent employed versions of the graded index medium in PC structures are known as a graded photonic crystal (GPC). Diferent GPCs have been designed with the gradual variations of re- fractive index, lattice parameters, and flling factor along with the ra- dial or axial direction [11–14],[15]. The change in optical and struc- tural parameters of GPCs enhances their ability to control, confne, and https://doi.org/10.1016/j.optlastec.2020.106293 Received 24 December 2019; Received in revised form 17 March 2020; Accepted 16 April 2020 ⁎ Corresponding author at: Department of Physics, University of Mumbai, Mumbai 400 032, India. E-mail address: b_singh@ph.iitr.ac.in (B.K. Singh). Optics and Laser Technology 129 (2020) 106293 Available online 29 April 2020 0030-3992/ © 2020 Elsevier Ltd. All rights reserved. T