The Goos-Hänchen (GH) effects are investigated for a transverse magnetic beam totally reflected by periodic PT-symmetric photonic crystals. A dielectric layer with a real refractive index situates as a defect in the center. Both positive and negative spatial GH shifts are induced around the defect mode. The GH shifts sensitively change with the refractive index of the defect layer. More importantly, giant negative GH shift effect with big reflectance could be found and modulated by increasing the gain-loss factor in PT-symmetric systems, which could improve the detecting sensitivity of the defect. Our study may be valuable in potential applications for highly sensitive sensors.

The electronic and optical properties of three types of aluminum phosphide bilayers are examined using density functional theory. The results indicate that they all possess proper direct gaps, which exhibit a rich variety of behaviors depending on the strain. The band gaps of these aluminum phosphide bilayers could be easily tuned in the energy range from 0 eV to 1.9 eV under a wide range of biaxial strain. Additionally, band gap transitions between direct and indirect types are found when the external strain applied on them is changed from −12% to 12%. In addition, it was found that these AlP bilayers show strong light-harvesting ability for the ultraviolet light range of the solar spectrum (400–100 nm). The results obtained here indicate that these aluminum phosphide bilayers may have significant potential applications in future nanoelectric fields.

We systematically study ultraviolet laser-induced ultrafast photovoltaic effect in miscut $\mathrm{La}\mathrm{Sr}\mathrm{Al}{\mathrm{O}}_4$ single crystal wafers with different thicknesses at ambient temperature without any applied bias. An open- circuit photovoltage (PV) is obtained when the wafer is irradiated by a $248\mathrm{nm}$ laser pulse of $20\mathrm{ns}$ duration. With the decrease of crystal thickness, the peak PV increased to a maximum of $2.66\mathrm{mV}$ at $340\mathrm{\mu m}$ and then decreased to $1.3\mathrm{mV}$ at $155\mathrm{\mu m}$. Meanwhile, the 10%–90% rise time of photovoltaic responses declines gradually. The inner mechanism of the present thickness-dependent photovoltaic response is discussed.