Random lasing from optical fibers with phase separated glass cores.

A novel random laser, integrating a passive optical fiber with a phase separated aluminosilicate core-silica cladding as the feedback medium, is proposed and presented. The core exhibits greatly enhanced Rayleigh scattering, therefore requiring a significantly reduced length of scattering fiber (4 m) for lasing. With a Yb-doped fiber as the gain medium, the fiber laser operates at 1050 nm with low threshold power and possesses an output that can be amplified through conventional means. Furthermore, the laser was found to have a high degree of spatial coherence, spectral broadening with increasing input power, and temporal spectral variation. The facile setup and results herein pave the way for further study and applications based on low threshold random fiber lasers.

Less than 1% quantum defect fiber lasers via ytterbium-doped multicomponent fluorosilicate optical fiber.

Two ytterbium-doped fiber lasers exhibiting quantum defects of less than 1% are demonstrated, in which pumping at wavelengths of 976.6 and 981.0 nm yielded lasing at wavelengths of 985.7 and 989.8 nm, respectively. The multicomponent fluorosilicate active optical fiber, fabricated using the molten core method, has spectral characteristics similar to those of fluoride glasses, namely short average emission wavelength and long upper state lifetime. A best-case slope efficiency of 62.1% was obtained, matching the theoretical model very well. With further fiber and laser optimization, slope efficiencies approaching the quantum limit should ultimately be possible. A reduction in the quantum defect may offer significant mitigation of issues associated with fiber heating. As such, this work can serve as a possible direction for future scaling of high-power fiber laser systems.

Additivity of the coefficient of thermal expansion in silicate optical fibers.

A model that predicts the material additivity of the thermal expansion coefficient in the binary silicate glasses most commonly used for present (GeO2-SiO2, P2O5-SiO2, B2O3-SiO2, and Al2O3-SiO2) and emerging (BaO-SiO2) optical fibers is proposed. This model is based on a derivation of the expression for the coefficient of thermal expansion in isotropic solids, and gives direct insight on the parameters that govern its additivity in silicate glasses. Furthermore, a consideration of the local structural environment of the glass system is necessary to fully describe its additivity behavior in the investigated systems. This Letter is important for better characterizing and understanding of the impact of temperature and internal stresses on the behavior of optical fibers.

Single- and few-moded lithium aluminosilicate optical fiber for athermal Brillouin strain sensing.

Results are presented toward realizing a true single-mode fiber whose Brillouin frequency shift is independent of temperature, while its dependence on strain is comparable to conventional high-silica-content single-mode fibers. Demonstrated here is a fiber with a negative thermal sensitivity dν/dT of -0.26 MHz/K and a strain sensitivity of +406 MHz/%. The suppression of the Brillouin thermal response is enabled by the large thermal expansion coefficient of the group I oxide-containing silica glass network.