Pursuing nanometer-scale nonlinear converters based on second harmonic generation (SHG) is a stimulating strategy for bio-sensing, on-chip optical circuits, and quantum information processing, but the light-conversion efficiency is still poor in such ultra-small dimensional nanostructures. Herein, we demonstrate a highly enhanced broadband frequency converter through a hybrid plasmonic–dielectric coupler, a ZnTe/ZnO single core–shell nanowire (NW) integrated with silver (Ag) nanoparticles (NPs). The NW dimension has been optimized to allow the engineering of dielectric resonances at both fundamental wave and second harmonic frequencies. Meanwhile, the localized surface plasmon resonances are excited in the regime between the Ag NPs and ZnTe/ZnO dielectric NW, as evidenced by plasmon-enhanced Raman scattering and resonant absorption. These two contributors remarkably enhance local fields and consequently support the strong broadband SHG outputs in this hybrid nanostructure by releasing stringent phase-matching conditions. The proposed nanoscale nonlinear optical converter enables the manipulation of nonlinear light–matter interactions toward the development of on-chip nanophotonic systems.

The 8 μm thick single-crystalline α-Ga₂O₃ epilayers have been heteroepitaxially grown on sapphire (0001) substrates via mist chemical vapor deposition technique. High resolution X-ray diffraction measurements show that the full-widths-at-half-maximum (FWHM) of rocking curves for the (0006) and (10-14) planes are 0.024° and 0.24°, and the corresponding densities of screw and edge dislocations are 2.24 × 10⁶ and 1.63 × 10⁹ cm^-2, respectively, indicative of high single crystallinity. The out-of-plane and in-plane epitaxial relationships are [0001] α-Ga₂O₃//[0001] α-Al₂O₃ and [11-20] α-Ga₂O₃//[11-20] α-Al₂O₃, respectively. The lateral domain size is in micron scale and the indirect bandgap is determined as 5.03 eV by transmittance spectra. Raman measurement indicates that the lattice-mismatch induced compressive residual strain cannot be ruled out despite the large thickness of the α-Ga₂O₃ epilayer. The achieved high quality α-Ga₂O₃ may provide an alternative material platform for developing high performance power devices and solar-blind photodetectors.

Solar-blind photodetectors are of great interest to a wide range of industrial, civil, environmental, and biological applications. As one of the emerging ultrawide-bandgap semiconductors, gallium oxide (Ga2O3) exhibits unique advantages over other wide-bandgap semiconductors, especially in developing high-performance solar-blind photodetectors. This paper comprehensively reviews the latest progresses of solar-blind photodetectors based on Ga2O3 materials in various forms of bulk single crystal, epitaxial films, nanostructures, and their ternary alloys. The basic working principles of photodetectors and the fundamental properties and synthesis of Ga2O3, as well as device processing developments, have been briefly summarized. A special focus is to address the physical mechanism for commonly observed huge photoconductive gains. Benefitting from the rapid development in material epitaxy and device processes, Ga2O3-based solar-blind detectors represent to date one of the most prospective solutions for UV detection technology towards versatile applications.