Dyakonov–Tamm waves guided by a phase–twist combination defect in a sculptured nematic thin film

The propagation of Dyakonov–Tamm waves guided by a phase–twist combination defect in a sculptured nematic thin film (SNTF) was studied theoretically by numerical solution of a dispersion equation. The phase defect was fixed at 180°, whereas the twist defect was kept variable as also the direction of propagation. Multiple Dyakonov–Tamm waves that differ in spatial profile, degree of localization, and phase speed were found to propagate guided by the combination defect, depending on the angle between the morphologically significant planes of the SNTF on either side of the defect as well as on the direction of propagation. The most strongly localized Dyakonov–Tamm waves turned out to be essentially confined within one structural period of the SNTF normal to the combination defect.