Ultraviolet (UV) components are widely used in industry, and the scientific and medical research fields. However, they are known to be inefficient (due to high absorption loss of UV light), expensive, and bulky. Special ultrawide bandgap dielectric metasurface should have a high efficiency due to low absorption and can be used to control the amplitude, polarization, and phase of UV light. We demonstrate UV metalens design specifically at representative UVC (244 nm), UVB (308 nm), and UVA (375 nm) wavelength, respectively. Both one-dimensional and two-dimensional metalenses are demonstrated for light convergence. The designed metalens is composed of high-aspect-ratio aluminum nitride nanorod array, with the corresponding conversion efficiency estimated to be as high as 91.15%, 89.92%, and 79.46%. Our designed UV metalens and the method demonstrated would promote the miniaturization and high-density integration of the UV nanophotonics.
We have successfully fabricated 7-μm 155-nm-thick undercut microdisk cavities with AlN / Al0.60Ga0.40N (5.5 nm / 2.5 nm) multiple quantum wells epitaxially grown on Si substrate by metal–organic chemical vapor deposition. Upon optical pumping, whispering-gallery modes (WGMs) with wavelengths around ∼250 nm can be observed throughout the photoluminescence spectrum at room temperature, with quality factors around 500 to 1000. These cavity modes have been analyzed by theoretical calculations. Our results suggest great potentials to demonstrate WGM lasing in the UVC range from these AlGaN/AlN-on-Si microdisk cavities monolithically grown on a Si platform.