RESUMO
The appealing characteristics of quasi-crystalline nanostructure offer tremendous possibilities to tailor the transmission of the angular momenta. Moreover, the second harmonic generation existing in nonlinear nanostructures also exhibits remarkable potential in the fundamental and applied research areas of the angular momenta conversion. By systematically studying the general angular momenta conservation law, we show that the high-dimensional angular momenta transformation and spin-orbital coupling are realized by the nonlinear sunflower-type quasicrystals, which feature the high-fold rotational symmetry and possess an increasing degree of rotational symmetry in Fourier space. Interestingly, since the sequential Fibonacci numbers are essentially encoded in the distinctive nonlinear sunflower-type patterns, the high-fold angular momenta transformation regularly occurs at both linear and nonlinear wavelengths. The investigations of fundamental physics for the unique quasi-crystals reveal scientific importance for manipulating the angular momenta of nonlinear optical signals, which plays a key role in the promotion and development of modern physics.
RESUMO
Metal nanoparticles associated with local surface plasmon (LSP) resonance, i.e. highly confined electric field and large scattering cross-sections (σ), have been widely used to enhance the light-harvesting of solar cells toward high optoelectronic performance. However, the metal nanoparticles embedded into the solar cells suffer from parasitic ohmic loss that subsequently causes the local temperature to rise, which, in turn, reduces the photoelectric conversion efficiency and stability of solar cells. Previous studies on plasmon-enhanced solar cells have rarely considered the negative effects of metal nanoparticles' ohmic losses and temperature rise on solar cell performance optimization. Therefore, it is of great interest to alleviate the ohmic loss and temperature rise that are critical for high-performance solar cells. Herein, we propose a model to comprehensively study and optimize the performance of plasmon-enhanced perovskite solar cells (PSCs) from simultaneous optical-electrical-thermal aspects. First, the optical simulation results indicated that the geometric tuning of metal nanoparticles can make full use of the plasmonic effect and significantly improve PSCs' light absorption. The analysis showed that the embedded nanoparticles with optimal geometry in PSC devices can significantly increase the optical absorption by 17% (41%) compared to non-optimal nanostructures (devices without nanoparticles). Then, we explored the influence of the temperature-dependent carrier mobility on PSC performance from the coupled electrical and thermal studies. Our results indicated that the optimization of the geometrical parameters of metal nanoparticles can minimize energy dissipation, thereby redusing the heat loss and then lowering the local cell temperature. Interestingly, PSCs' electrical properties such as carrier transportation significantly improved. Consequently, the PSC performance improved with increment in the short-circuit current by 23% and the power conversion efficiency by 38%.
RESUMO
The nonlinear metamaterials have been shown to provide nonlinear properties with high nonlinear conversion efficiency and in a myriad of light manipulation. Here we study terahertz generation from nonlinear metasurface consisting of single layer nanoscale split-ring resonator array. The terahertz generation due to optical rectification by the second-order nonlinearity of the split-ring resonator is investigated by a time-domain implementation of the hydrodynamic model for electron dynamics in metal. The results show that the nonlinear metasurface enables us to generate broadband terahertz radiation and free from quasi-phase-matching conditions. The proposed scheme provides a new concept of broadband THz source and designing nonlinear plasmonic metamaterials.