•In this paper, we propose a novel multi-orbital-angular-momentum multi-ring micro-structured fiber (MOMRMF) firstly. Due to taking advantage of the micro-structured fiber properties, the refractive index difference between ring core and cladding can be huge without doped material. This opens a window for designing OAM fiber supporting modes with higher topological charges.•In our design, each ring can support 36 modes. What's more, the effective refractive index (neff) differences between the adjacent eigenmodes are all larger than 10−3, which is never achieved in previous works. That means our fiber can avoid inter-mode crosstalk effectively.•Under the fiber diameter is 125 μm, this compact multi-core fiber has 19 ring cores. To avoid the inter-ring crosstalk, we utilize the air holes to suppress the overlap integral of electric field distribution between adjacent ring cores. Plus, we analyze the effects versus different air holes diameters. According to simulation result, the suppressing performance is better than the fibers with trench-assisted.•To fabricate this fiber, we give our fiber design strategy in detail. We can just apply the simple stacking method to make the fiber preform.In this paper, a novel multi-orbital-angular-momentum multi-ring micro-structured fiber (MOMRMF) is proposed for the first time. This compact MOMRMF is presented with 19 rings, each ring supporting 36 modes (34 of them are OAM ones i.e., 684 channels in total) over the whole C wavelength band (1520–1580 nm). Due to the large refractive index difference between silica and air, the effective refractive index (neff) differences between the adjacent eigenmodes are all larger than 10−3, which is practically impossible to gain in other traditional high-density OAM fibers fabricated by modified chemical vapor deposition (MCVD) method. Compared with the trench-assisted multi-OAM multi-ring fiber (TA-MOMRF), the lower-level inter-ring crosstalk in the designed MOMRMF also can be achieved by the air hole-assisted. It is believed that both the high-density and low-level crosstalk make such a fiber of great potential in the space-division multiplexing (SDM) system.

For the first time, the fundamental mode of a dual-mode photonic crystal fiber (PCF) is suppressed by the index-matching between the core and cladding modes. The PCF designed proposes a new solution of selective excitation of second-order modes. The simulation results demonstrate that the confinement loss of the fundamental mode is higher than 1 dB/m, while the second-order modes are lower than 10−4 dB/m in the C+L waveband. The high feasibility and low wavelength dependence make the fiber of great potential in the mode-division multiplexing (MDM) transmission.

We present an elliptical core D-shaped photonic crystal fiber-based plasmonic sensor, and the coupling characters for different refractive index of detected analyte are investigated by finite element method. It is found that the sensitivity depends strongly on the slope of the phase difference at resonant wavelength for phase interrogation, and the sensitivity can be up to 2.2 × 105 deg/RIU/cm when the sensor works close up to the upper detection limit of analyte refractive index of 1.373. Based on our discussion, the higher sensitivity always associates with narrower dynamic sensing range. As a comparison, wavelength interrogation has been included in the paper, and it offers wider dynamic sensing range and higher upper detection limit but much lower sensitivity. Overall, the resonances of different order plasmonic modes and core mode play essential role in both schemes.

Yb2+, Yb3+ co-doped silica glasses were prepared by solid state reaction under vacuum condition for the first time. The luminescence properties of Yb2+-doped silica glass were investigated. There are four strong absorption bands in the Ultraviolet (UV) light region due to the 4f14–4f135d1 transition of the Yb2+ ions. The main emission wavelength of the Yb2+-doped silica glass was around 530 nm by the excited wavelength of 398 nm. The full width at half maximum (FWHM) of the excitation and emission bands were 137 nm, 165 nm respectively. The results suggest the Yb2+-doped silica glasses may be the potential medium for white light sources based on near UV LED chip.Highlight► We first fabricated Yb2+/Yb3+ co-doped silica glass under vacuum condition. ► The main emission peak around 530 nm was obtained under excited UV wavelength. ► The wide excitation and emission bands of 173 m and 162 nm were achieved.