Pyroelectric gap solitons in photorefractive optical lattices

The present research work examines the existence and characteristics of spatially confined optical gap solitons in a photonic lattice embedded in pyroelectric photorefractive crystal having a finite pyroelectric coefficient. The Floquet-Bloch theory is used to analyze the uniform lattice and derive the photonic lattice band structure. In the photonic band gaps, which are typically opaque to light transmission, the photorefractive nonlinearity permits the formation of solitons. The paraxial Helmholtz equation is solved using Bloch wave solution, and double hump, symmetric and asymmetric multi-hump soliton states were found to exist in first finite band gap and symmetric and asymmetric multi-hump soliton states were found to exist in second finite band gap. Our study reveals that soliton width and intensity depend on the propagation constant or the wave vector of the gap soliton lying within the band gap. Additionally, the Vakhitov-Kolokolov (VK) criterion and numerical techniques are used to analyze the stability of the spatial gap solitons against small perturbations. We further undertake direct propagation simulations for each type of soliton to confirm the linear stability analysis. Our investigations have potential practical applications in optical interconnects, optical networks, optical waveguides among others.