Second-harmonic generation

Abstract: Titanium nitride (TiN) is a novel refractory plasmonic material which can sustain high temperatures and exhibits large optical nonlinearities, potentially opening the door for high-power nonlinear plasmonic applications. We fabricate TiN nanoantenna arrays with plasmonic resonances tunable in the range of about 950–1050 nm by changing the antenna length. We present second-harmonic (SH) spectroscopy of TiN nanoantenna arrays, which is analyzed using a nonlinear oscillator model with a wavelength-dependent second-order response from the material itself. Furthermore, characterization of the robustness upon strong laser illumination confirms that the TiN antennas are able to endure laser irradiation with high peak intensity up to 15 GW/cm2 without changing their optical properties and their physical appearance. They outperform gold antennas by one order of magnitude regarding laser power sustainability. Thus, TiN nanoantennas could serve as promising candidates for high-power/high-temperature applications suc...

Abstract: The electronic band structures for AgGaX(2) (X=S, Se, Te) chalcopyrites have been calculated using a pseudopotential total energy method. First-principles calculations of the linear and nonlinear optical properties are presented for these crystals, with the electronic band structures obtained from pseudopotential method as input. The theoretical refractive indices and nonlinear optical coefficients are in good agreement with available experimental values. The origin of the nonlinear optical effects is explained through real-space atom-cutting analysis. The contribution of the GaX(2) group (X=S, Se, Te) for second harmonic generation (SHG) effect is dominant while that of the cation Ag is negligible. In addition, the percentage contribution to the SHG coefficients from the different bonds increase with increase of the bond order.

Abstract: Linear and nonlinear [second harmonic generation (SHG)] optical functions of cubic and hexagonal BN, AlN, GaN, and InN have been studied by using the first-principles full-potential linearized augmented plane-wave method. Equilibrium lattice constants are determined from the total-energy minimization method. The calculated spectra of the second-order optical susceptibility show pronounced structures related to the two-photon resonances. In materials with heavy metals there are remarkable contributions from the single-photon transitions. Line shapes of the linear and particularly the nonlinear optical spectra of GaN and InN crystals are very sensitive to the interactions between the conduction bands and metallic d states. Studies of the nonlinear optical susceptibilities in both wurtzite and cubic crystals show high sensitivity of the SHG spectra to the changes of atomic structure.