Yanjun Li 교수

Here, we demonstrate a microwave (MW) cavity interference enhancement method to image nano-defects on the surface of metal waveguide. The MW cavity interference system mainly consisted of a MW coaxial resonant cavity with a nano-probe. The MW signals have been evenly divided into two channels. One was the reference signal inputted into the MW waveguide and coupled into the MW cavity via the probe. Also, the coupling strength depends on the distance between the probe and the MW waveguide. Another

A Michelson-type large core optical fiber sensor has been developed, which is designed based on the optical carrier-based microwave interferometry technique, and fabricated by using two pieces of 200-μm diameter fused silica core fiber as two arms of the Michelson interferometer. The interference fringe pattern caused by the optical path difference of the two arms is interrogated in the microwave domain, where the fringe visibility of 40 dB has easily been obtained. The strain sensing at both ro

We report a new method to measure the CO(2)-laser-irradiation-induced refractive index modulation in the core of a single-mode optical fiber for the purpose of design and fabrication of long-period fiber gratings (LPFGs) without applying tension. Using an optical fiber Fabry-Perot interferometer, the laser-induced axial refractive index perturbation was measured. We found that the CO(2)-laser-irradiation-induced refractive index change in the fiber core had a negative value and that the magnitud

Abstract Starburst materials, 1,3,5-tris[3,5-bis(pyrid-4-yl)phenyl]benzene (1a) and 1,3,5-tris[3,5-bis(pyrid-3-yl)phenyl]benzene (1b) were designed and synthesized. By using fac-tris(2-phenylpyridyl)iridium(III) [Ir(ppy)3] as a green emitter and 1 as an electron-transporting material, a green OLED was fabricated. The OLED exhibited a maximum power efficiency (PE) of 96 lm W−1 with an external quantum efficiency (EQE) of 23% at 2.1 cd m−2, and a PE of 75 lm W−1 with an EQE of 23% at 100 cd m−2.

Abstract A series of novel phenanthroline derivatives (Phens) have been synthesized and their application to organic light-emitting devices (OLEDs) as an electron-transport layer was investigated. The OLEDs with a structure of ITO/α-NPD/Alq3/Phen/LiF/Al exhibited remarkable performances and lower operating voltages compared to Alq3-based device, indicating that Phens posses favorable electron-transport properties.

Abstract Proportion-integral-derivative (PID) closed-loop frequency-locking (CLFL) technology has been demonstrated to improve the magnetic field sensitivity of spin-based sensors based on the nitrogen-vacancy (NV) color centers in diamond. First, we analyse the undulation effect of the fluorescence quantum yield of NV centers with a magnetic field. The valley value of the magnetic resonance spectrum have been differential into a zero to insensitive to intensity fluctuations of fluorescence quan

Abstract Anti-relaxation surface coatings can reduce collisions between alkali-metal atoms and cell walls, thereby prolonging the spin-polarization lifetime of alkali-metal atoms. This phenomenon can considerably improve the performance of quantum sensors. Researchers have focused on the surface topography and composition of anti-relaxation coatings in alkali-metal vapor cells and on methods that provide an increase in the relaxation time of alkali metals. We proposed a novel method to character

Abstract Contrast and linewidth, which depend on the microwave (MW) and light powers, are critical for optimizing magnetometer sensitivity based on high-density nitrogen vacancy (NV) centers in diamond. Therefore, the tradeoff between laser and MW powers can be adjusted to optimize the contrast and linewidth extracted from the magnetic resonance. In this paper, we developed a pulsed electron spin resonance (ESR) measurement to enhance the magnetic field sensitivity of an NV magnetic sensor with

The adsorption and bonding properties of hydroxyl species on metal oxide semiconductor surfaces and interfaces are important for the understanding of catalytic reactions. Surface charge distribution and polaron formation are also affected by hydroxyl species. In this work, we combined atomic force microscopy and Kelvin probe force microscopy techniques to distinguish H2O and hydroxyl (OHt at titanium rows and OHb at bridging oxygen rows) on the rutile TiO2(110) surface at 78 K. We achieved the m

The charge state of noble metal atoms on a semiconductor surface is an important factor in surface catalysis. In this study, Au atoms were deposited on the rutile TiO₂(110) surface to characterize its charge properties using atomic force microscopy with Kelvin probe force microscopy at 78 K. Au single atoms, dimers, and trimers at different sites on the surface were investigated. Positively charged Au atoms were verified at oxygen sites, while negatively charged Au atoms were found ne

Studies of the physics underlying carrier transport characteristics and band bending of semiconductors are critical for developing new types of devices. In this work, we investigated the physical properties of Co ring-like cluster (RC) reconstruction with a low Co coverage on a Si(111)-7 × 7 surface at atomic resolution by atomic force microscopy/Kelvin probe force microscopy at 78 K. We compared the applied bias dependence of frequency shift between two types of structure: Si(111)-7 × 7 and Co-

An all-fiber device using single mode fiber with graded-index multimode fiber to fabricate a collimator is investigated. This device has advantages of small size, low splicing loss and ease of fabrication, and it could substitute bulky GRIN lens. Experiments show that it has the best collimating effect when the length of graded-index fiber is between 305 μm and 315 μm.