Evidence of the primary-color photoluminescence in ion (H,H,C) irradiated and thermal annealed SrTiO3

We have measured photoluminescence (PL) spectrum of (1) thermal-annealed SrTiO₃/Si thin film and undoped SrTiO₃ single crystal; (2) SrTiO₃ single crystal irradiated by high energy (3 MeV) proton, deuterium, and He ion beams and (3) SrTiO₃ single crystal irradiated by low energy (60 keV) H⁺ and C⁻ ions. Two PL emissions are induced in (1) and (2) at visible frequencies 3 and 2.45 eV, while another PL peak is induced at 2 eV in (3). When compared with our previous PL experiments on high-temperature annealed SrTiO₃/SiO₂/Si thin film and 3 MeV proton (H⁺) irradiated STO single crystal, these results confirm that the three PL emissions with blue (3 eV), green (2.45 eV), and red-orange (2 eV) frequencies originate indeed from SrTiO₃. These primary-color PL effect induced at room-temperature makes STO a strong candidate material for future oxide-based optoelectronic application.     

Minimum orders of eulerian oriented digraphs with given diameter

A digraph D is oriented if it does not contain 2-cycles.If an oriented digraph D has a directed eulerian path,it is an oriented eulerian digraph.In this paper,when an oriented eulerian digraph D has minimum out-degree 2 and a diameter d,we find the minimum order of D.In addition,when D is 2-regular with diameter 4m(m ≥ 2),we classify the extremal cases.     

Nanoporous niobium oxide for label-free detection of DNA hybridization events

We found that DNA probes can be immobilized on anodically prepared porous niobium oxide without a chemical modification of both the DNA probes and the substrate. By using the porous niobium oxide with a positive surface charge, DNA hybridization events are detected on the basis of the blue-shift of a maximum absorption peak in UV-vis-NIR spectroscopy. The blue-shift is ascribed to the change of surface charge upon single- or double-stranded DNA. The method does not require a label and shows high sensitivity with the detection limit of the concentration of 1nM.     

Wafer-Scale Manufacturing of Near-Infrared Metalenses

Metalenses have revolutionized optical technologies with their superior ability to manipulate light and the potential to replace conventional, bulky optical components. However, their commercialization is hindered by limitations in conventional manufacturing techniques, such as small patterning areas, low throughput, and high cost. In this study, two methods are introduced for scalable and wafer-scale manufacturing of metalenses operating in the near-infrared region, aimed at overcoming the abovementioned challenges. The first type of metalens is polarization-independent and constructed using hydrogenated amorphous silicon cylindrical structures fabricated through direct photolithography. This metalens has a diameter of 1 cm and numerical aperture (NA) of 0.53. The focusing efficiency is confirmed at a 940 nm wavelength, and the focal spot profile approaches the diffraction limit. The second metalens is polarization-dependent and fabricated using silicon nanoparticle-embedded-resin rectangular structures through a cost-effective nanoimprinting method. This process can produce metalenses with a diameter of 5 mm and an NA of 0.53. Both types of metalenses demonstrate high-resolution capabilities when imaging a 1951 USAF resolution test target and bioimaging. This research offers innovative pathways for the mass production and large-scale fabrication of metalenses. It is believed that the work will accelerate the industrialization of metalenses, fostering further advances in optical technology.