Enhanced sensitivity of photonic crystal slab transducers by oblique-angle layer deposition

Improving the sensitivity of guided-mode resonance sensors under oblique incidence condition

We present an investigation on the use of oblique incidence condition to enhance the sensitivity of guided-mode resonance (GMR) sensors. By adjusting the incident angle, the enhancement of GMR sensitivity in non-subwavelength regime can be obtained. The measured results show that the bulk sensitivity of the GMR sensors with period of 809 nm climbs to 177% or 292% as the incident angle increases from 15° to 25° or 35°, respectively. The same trend is also obtained for the grating period of 994 nm. Simulations based on the rigorous coupled wave analysis (RCWA) method were performed, and we also built a new slab waveguide model to describe the relationship between bulk sensitivity and the incident angle. The present investigation demonstrates a new method for enhancing the bulk sensitivity of GMR sensor. Moreover, simple fabrication techniques can be utilized since a large grating period was used.

Experimental and Theoretical Investigation of Crystallographic Orientation Dependence of Nanoscratching of Single Crystalline Copper

In the present work, we perform experiments and molecular dynamics simulations to elucidate the underlying deformation mechanisms of single crystalline copper under the load-controlled multi-passes nanoscratching using a triangular pyramidal probe. The correlation of microscopic deformation behavior of the material with macroscopically-observed machining results is revealed. Moreover, the influence of crystallographic orientation on the nanoscratching of single crystalline copper is examined. Our simulation results indicate that the plastic deformation of single crystalline Cu under the nanoscratching is exclusively governed by dislocation mechanisms. However, there is no glissile dislocation structure formed due to the probe oscillation under the load-controlled mode. Both experiments and MD simulations demonstrate that the machined surface morphologies in terms of groove depth and surface pile-up exhibit strong crystallographic orientation dependence, because of different geometries of activated slip planes cutting with free surfaces and strain hardening abilities associated with different crystallographic orientations.