In this paper, we propose the low loss negative curvature fiber with circular internally tangent nested tube in elliptical cladding tubes. The leakage loss can be decreased because the elliptical cladding tubes have higher curvature at the core boundary compared to the circular cladding tubes. The circular nested tube in the elliptical cladding tubes provides an additional antiresonant reflection element to reach lower leakage loss. The simulation results show the negative curvature hollow core fiber in this paper has a low leakage loss in the spectral region from 1.3μm to 1.7μm. In particular, the leakage loss is 0.012dB/km at 1.55μm.
In this paper, the numerical aperture (NA) of photonic crystal fiber (PCF) is measured by a system with spectrometer,
and high-precision results are obtained. The spectrometer can record the light intensity of different wavelengths. It
overcomes the limitation that the traditional measurement can only measure the NA in some fixed wavelengths. We get
the NA at any wavelength in 500nm~900nm range, which is determined by light source and spectrometer. Therefore, the
parameters related with NA can be better studied, such as: the mode field area, cut-off wavelength and so on. The
characterization of PCFs can be better represented too. The measured results are compared with theoretical calculation
value, and they agree with each other very well. According to the measured NA, the mode field area of sample fiber is
calculated and compared with simulation results calculated by fast-vector-method.
The glass samples of SiO<sub>2</sub>-Al<sub>2</sub>O<sub>3</sub>-CdO-Li<sub>2</sub>O-K<sub>2</sub>O-Na<sub>2</sub>O with different Nd<sup>3+</sup>-doped concentration are prepared by high-temperature
solid-state reaction method, and test the absorption spectrums as well as emission spectrum excited at 488
nm, 532 nm and 808 nm. The third-order optical nonlinear properties of glasses samples are investigated by the z-scan
technique. With the increment of doping concentration of Nd<sup>3+</sup>, the third-order nonlinear refractive index and the
absorption index increase, so it belongs to the self-focusing and reverse saturated absorption medium. The glass samples
open a outlook of application for nonlinear optical medium and excellent luminescence materials.
The cadmium silicate glass samples of 40SiO<sub>2</sub>-14Al<sub>2</sub>O<sub>3</sub>-(40-x) CdO-2Li<sub>2</sub>O-2K<sub>2</sub>O-2Na<sub>2</sub>O-xEr<sub>2</sub>O<sub>3</sub> (x=0.15, 0.20, 0.25,
0.30, 0.35, 0.40 mol) was prepared by high-temperature solid-state reaction method, and it is pumped at 488 nm, 532 nm
and 800 nm respectively. The results indicate that the main peak wavelengths are at 547 nm, 731 nm and 1534 nm
excited at 488 nm. The relationship of the intensity between the emission light of 731 nm and Er3<sup>+</sup>-doped concentration
is nonlinear. Near-infrared light nearby 1534 nm is excited at 532 nm and 800 nm, but it is weaker at 800 nm. The glass
samples open a outlook of application for conversion luminescence materials.
Using an efficient, full-vectorial numerical simulation method, we analyze the existent conditions of the photonic bandgap (PBG), which is further demonstrated through experimental research. We utilize the method of transmission spectrum to measure the hollow-core microstructure fibers (HC-MSFs) in the visible and near infrared regions. The signal is obtained by detecting light from the end of the fiber. The experimental results indicate that there are several strong transmission bands in the near infrared region, but hardly any bandgaps in the visible region. Furthermore the attenuation in the visible wavelength is very considerable. The parameters of the HC-MSFs structure used in the measurement are the distance of nearest air holes pitch Λ (2.65μm), the diameter of air holes in the cladding d (2.10μm), and the central air core diameter (8.37μm). The spectrum positions of the bandgap in the spectrogram are 2297nm, 2406nm, and 2525nm, respectively. The repetition of the experimental results is fine.
The Stacking-capillary Method is widely used in the fabrication of the Micro-structure Fiber (MSF). We describe an improved stacking-capillary method, which can fabricate the MSF without interstitial holes. The method includes several steps. Firstly, the MSF preform is made by the stacking-capillary method; secondly, the MSF preform is put into the high temperature furnace to heat at 1600°, then the positive pressure is produced into the capillaries by adding air, every three adjacent capillary holes are expanded in the preform, and the interstitial holes are eliminated, all the capillaries are fused together, although the round capillary have changed to hexagon, the size of the prefrom does not change, and still keeps very good structure. The step of eliminating the interstitial hole can help to keep the MSF structure during drawing fiber. We get well results by the Improved Stacking-capillary Method.