One of the most promising areas of research at the moment is the development of optical frequency summation and doubling systems, which use nonlinear crystals as an active element. Gallium phosphide (GaP) in the form of nanowires, which have a high dielectric constant and are transparent in the visible and infrared regions, can be used as a promising material for these elements. These crystals can be easily integrated into modern photonics systems due to their unique shape. In this study, we investigated the process of second harmonic generation in GaP nanowires, depending on their geometric parameters and the direction of incident radiation. We found the conditions that provide the highest efficiency of the generation process along the axis of the crystal. The possibility of the propagation of the second harmonic along the nanowire axis in air is demonstrated for specific parameters of the system — the diameter and angle of radiation. An increase in diameter leads to a reduction in the difference between the actual optimal direction and the predicted one, as the size- related characteristics of the filamentous nanocrystal tend to become more volumetric with increasing diameter. Results can be used to create various nanophotonic devices.
Funtikova et al. (2025) studied this question.