Micro-joule level visible supercontinuum generation in seven-core photonic crystal fibers pumped by a 515 nm laser.

A visible supercontinuum (SC) with high energy is of vital importance to applications in remote sensing and hyperspectral light detection and ranging. A fiber laser with a wavelength of 1030 nm is frequency doubled through a LBO (LiB3O5) crystal, and a high-energy 515 nm laser is obtained after wavelength conversion. Two kinds of seven-core photonic crystal fibers (PCFs) are used in this Letter. One is a uniform seven-core PCF (USC-PCF), and the other is a tapered seven-core PCF (TSC-PCF). Pumped by a 515 nm laser with a pulse width in nanosecond level, an SC covering 400 to 900 nm is efficiently generated in both PCFs. A maximum energy of 4.24 µJ is obtained in a USC-PCF. To prevent fiber damage of the coupling fiber end, the TSC-PCF which contains a transition fiber and a meters-long small core fiber is fabricated. One end of the transition fiber possesses a larger core diameter, and the pump laser can be coupled into the TSC-PCF without fiber damage. The meters-long small core fiber has the same core size with a USC-PCF and is utilized as the nonlinear medium to generate an SC. The dispersive wave in the short wavelength band is excited when more energy is shed into a fiber anomalous dispersion region. Up to 15th-order Raman peaks are observed during the SC evolution process.

Selective doping of Ni2+ in highly transparent glass-ceramics containing nano-spinels ZnGa2O4 and Zn1+x Ga2-2x Ge x O4 for broadband near-infrared fiber amplifiers.

Selective doping of Ni2+ in octahedral sites provided by nanocrystals embedded in glass-ceramics (GCs) is crucial to the enhancement of broadband near-infrared (NIR) emission. In this work, a NIR emission with a full-width-at-half-maximum (FWHM) of 288 nm is first reported from ZnGa2O4: Ni2+ nano-spinels embedded GCs with excellent transparency. A comparison is made of the NIR luminescence properties of Ni2+ doped GCs containing ZnGa2O4, germanium-substituted ZnGa2O4 nano-spinels (Zn1+x Ga2-2x Ge x O4), and Zn2GeO4/Li2Ge4O9 composite nanocrystals that are free of Ga3+. The results show that ZnGa2O4: Ni2+ GCs exhibit a significantly enhanced NIR emission. The incorporation of the nucleating agent TiO2 is favored in terms of the increased luminescence intensity and prolonged lifetime. The possible causes for the enhancement effect are identified from the crystal structure/defects viewpoint. The newly developed GCs incorporate good reproducibility to allow for a tolerance of thermal treatment temperature and hence hold great potential of fiberization via the recently proposed "melt-in-tube" method. They can be considered as promising candidates for broadband fiber amplifiers.