Weinan Li

Host dependence of spectroscopic properties of Dy 3+ - doped and Dy 3+ , Tm 3+ -codped Ge-Ga-S-CdI 2 chalcohalide glasses

Two serial Dy(3+)-doped and Dy(3+), Tm(3+)-codoped (100-x)(0.8GeS(2).0.2Ga(2)S(3)).xCdI(2) (0<or=x<or=20) chalcohalide glasses were prepared and characterized. By analyzing the absorption and emission measurements of the two serial chalcohalide glasses with the Judd-Ofelt analysis, we were able to calculate its Judd-Ofelt strength parameters Omega t (t = 2, 4, 6), transition probabilities, exited state lifetimes, branching ratios, and emission cross-sections. In the Dy(3+)-doped glasses, increase of CdI(2) had positive effect up to 1330 nm fluorescence and the emission cross section (sigma emi) was estimated to be 4.19 x 10(-20)cm(2) for the 0.2 wt% Dy(3+)-doped 64 GeS(2).16 Ga(2)S(3).20 CdI(2) glass. In the Dy(3+), Tm(3+)-codoped glasses, increase of CdI(2) diminished the amount of ethane-like units [S(3)(Ga)Ge-Ge(Ga)S(3)], improved the Tm(3+): 3F 4-->Dy(3+): 6H 11/2 energy transfer efficiency and intensified the mid-infrared emissions. The emission cross sections (sigma emi) of the 2900 and 4300 nm fluorescences were estimated to be 1.68 x 10(-20) and 1.20 x 10(-20)cm(2) respectively for the 0.2 wt% Dy(3+) and 0.5 wt% Tm(3+) codoped 64 GeS(2).16 Ga(2)S(3).20 CdI(2) glass. These novel chalcohalide glasses are promising candidate materials for fiber-amplifiers and mid-infrared laser devices.

Broad-spectrum and long-lifetime emissions of Nd3+ ions in lead fluorosilicate glass.

A novel Nd(3+)-doped lead fluorosilicate glass (NPS glass) is prepared by a two-step melting process. Based on the absorption spectrum a Judd-Ofelt theory analysis is made. The emission line width of NPS glass is 44.2 nm. The fluorescence decay lifetime of the (4)F(3/2) level is 586+/-20 microsec, and the stimulated emission cross-section is 0.87x10(-20)cm(2)at 1056 nm. A laser oscillation is occurred at 1062 nm when pumped by 808 nm Diode Laser. The slope efficiency is 23.7% with a 415 mJ threshold. It is supposed that NPS glass is a good candidate for using in ultra-short pulse generation and amplification by the broad emission bandwidth and long fluorescence lifetime.

High birefringent rhombic-hole photonic crystal fibers

High birefringence induced by rhombic air-hole photonic crystal fibers (PCFs) is numerically analyzed by using the finite-element method. The birefringence of a few kinds of PCFs was investigated with different parameters related to rhombic holes, including the rhombic-hole shape, size, and spacing. It was found that the birefringence of the proposed rhombic-hole PCF in this study is relatively larger than that of an elliptical-hole PCF with the same air-filling fraction (f=0.0375) when the ratio of the rhombic-hole diagonal length is equal to the elliptical-hole ellipticity.

Analysis of birefringent and dispersive properties of photonic crystal fibers

Two types of high birefringence photonic crystal fiber (PCF) which import four or six big circular air holes near the elliptical-hole are proposed. Their birefringent and dispersive properties are analyzed by full-vector finite-element method (FEM). Numerical analysis demonstrates that importing the big circular hole near the center of elliptical-hole PCFs can achieve a high birefringence. When the ratio (d/Λ) of diameter to hole spacing is larger than 0.8, the proposed two types of PCF have a larger birefringence than that of sole elliptical air hole ones. When the ratio d/Λ is equal to 0.95, the birefringences of these two types PCF can be as high as 4.27×10(-3) and 5.09×10(-3) at the wavelength of 1.55 μm, respectively. Besides, PCF with the four big circular air holes has a large negative dispersion at the long wavelength in x-polarized mode, which indicates a potential in single-polarized mode dispersion compensation.

Evolutionary mechanism of the defects in the fluoride-containing phosphate based glasses induced by gamma radiation

In the laser driven inertial confinement fusion (ICF) experimental target chamber, like the 3ω (351 nm) laser irradiation, the irradiation of gamma ray and X-rays, will also cause the formation and increase of various defects in the investigated series of fluoride-containing phosphate based glasses that have potential use in novel high performance color separation optics. The induced defects contribute to the increase of absorption in the UV region, which will make the UV performance of these laser glasses deteriorated. Some of the induced defects can be bleached to some extent through the subsequent thermal treatment process, resulting from the release and capture of the electrons in conduction band. Through the gamma radiation and post-heat treatment experiments, a general model of the evolutionary mechanism of the defects in these fluoride-containing phosphate based glasses was proposed.

Fabrication and characterization of carbon/oxygen-implanted waveguides in Nd3+-doped phosphate glasses

Abstract. Optical planar waveguides in Nd3+-doped phosphate glasses are fabricated by a 6.0-MeV carbon ion implantation with a dose of 6.0×1014 ions/cm2 and a 6.0-MeV oxygen ion implantation at a fluence of 6.0×1014 ions/cm2, respectively. The guided modes and the corresponding effective refractive indices were measured by a modal 2010 prism coupler. The refractive index profiles of the waveguides were analyzed based on the stopping and range of ions in matter and the RCM reflectivity calculation method. The near-field light intensity distributions were measured and simulated by an end-face coupling method and a finite-difference beam propagation method, respectively. The comparison of optical properties between the carbon-implanted waveguide and the oxygen-implanted waveguide was carried out. The microluminescence and Raman spectroscopy investigations reveal that fluorescent properties of Nd3+ ions and glass microstructure are well preserved in the waveguide region, which suggests that the carbon/oxygen-implanted waveguide is a good candidate for integrated photonic devices.

Fabrication and characterization of Yb3+-doped gain-guided index-antiguided fiber with D-shaped inner cladding

Yb3+doped gain-guided index-antiguided fibers based on phosphate glasses are drawn using the rod-in-tube technique. These fibers have a circular core with 200 μm diameter and a D-shaped inner cladding with a 630/480 μm diameter for the longer/shorter axis. The negative index profile is present in these fibers, in which the core index of refraction is 0.019% lower than that of the inner cladding. Moreover, their laser amplifier characteristics are experimentally demonstrated, and the method of further improvement in laser performance is suggested.

4.62 kW excellent beam quality laser output with a low-loss Yb/Ce co-doped fiber fabricated by chelate gas phase deposition technique

A high-power Yb/Ce co-doped double-clad fiber with low optical loss was successfully fabricated by an optimized chelate gas phase deposition technique. It exhibits a nearly homogenous distribution of Al, Ce and Yb ions in the fiber core region, which reduce the clustering. The core attenuation at 1080 nm and 1383 nm are 12 dB/km and 46 dB/km, respectively, indicating high optical performance with a low optical loss. The amplifier stage with this fiber delivers 4.62 kW excellent beam quality (M2 = 1.67) laser output with a slope efficiency of 80.3%. The experimental results show that the chelate gas phase deposition technique is a prospective method to fabricate a Yb/Ce co-doped fiber with low optical loss, which is beneficial for acquiring multi-kilowatt continuous-wave fiber laser with excellent beam quality.

Ytterbium-doped double-cladding fiber with 3.5 kW output power, fabricated by chelate gas phase deposition technique

A ytterbium-doped double-cladding fiber was successfully fabricated by a chelate gas phase deposited technique. The measurement results of dopant concentration distribution and refractive index of preform indicate that radial and longitudinal homogeneity could be controlled perfectly with this technique. The absorption coefficients of fiber are 0.39 dB/m at 915nm and 1.02 dB/m at 976nm respectively. Using this fiber as the laser amplifier stage, 3592W output power at 1080nm with 72.5% slope efficiency was obtained with end-pump technique, which is close to the test results of Nufern commercial fiber. The results demonstrate that the chelate gas phase deposition technique is a relatively promising technique for high quality gain fiber fabrication.

Optimization effect of annealing treatment on oxygen-implanted Nd:CNGG waveguides

Neodymium-doped calcium niobium gallium garnet (Nd:CNGG) waveguide operated at 632.8 nm is demonstrated by the 3.0-MeV oxygen-ion implantation with a fluence of 6.0 × 1014 ions/cm2. The annealing treatment at 300∘C for 45 min is carried out to optimize the waveguide quality. The dark-mode spectra are measured by the m-line technique. The refractive index profiles are calculated from the effective refractive indices of the waveguide modes. The near-field intensity distributions are simulated based on the reconstructed refractive index profiles. The annealing treatment process could effectively remove unwanted defects and optimize the waveguide quality. The optical properties of the annealed waveguide are better than that of the as-implanted waveguide.