Field-Teleportation Technique for Simulation of an Optical Scattering from Defects in 2D-Periodic Structures

Field-teleportation approach has been successfully applied for modeling of optical scattering from nanodefects buried in semiconductor periodic structures. The essence of technique, called Field Teleportation, is to invoke the principle of equivalent sources (Schelkunoff\´s currents) using FDTD\´s discrete definition of the curl to copy any field propagating in one domain to finite region of another domain [1]. Here an approach to teleport a time- domain field into FDTD domain has been successfully tested for realistic defect scattering problem. The teleported field is used in FDTD to illuminate a scattering defect introduced into the test region and the time- domain scattered signal has been transformed into frequency domain as induced equivalent surface currents. Having these currents, calculation of the far-field scattering becomes a trivial procedure. Two typical extreme defects for 2D periodic line structure are reported. The first type of defect is a short of two lines ("Bridge defect") and the second is a total break of the line ("Gap defect"). Modelling results show that magnitude of the optical scattering from the Bridge defect in silicon trench structure having 130 nm pitch and 65 nm line width corresponds approximately to that of a 150 nm polystyrene latex (PSL) sphere, suggesting a high probability of detection if it can be isolated from background noise. Since the defect scattering spreads over wide solid angle, the dark-field detection is the best scheme.