Search

Higher-order-mode (HOM) fibers guiding light in large-effective-area (Aeff) Bessel-like modes have recently generated great interest for high-power laser applications. A polarization-maintaining (PM) version of HOM fibers can afford the added possibility of coherent beam combination, improved material processing, and polarization multiplexing of high-power fiber lasers. We report a PM-HOM fiber for guiding Bessel-like modes with Aeff ranging from 1200-2800 μm2. The fiber modes exhibit a birefringence value that compares well with that of a conventional single-mode PM fiber (2×10-4), and exhibit a polarization extinction ratio ranging from 13-23 dB over meter-long fiber lengths, practical for amplifier systems. This fiber presents a unique platform for next-generation high-power fiber systems, as well as for the fundamental studies on deterministically polarized Bessel-like modes in fibers.

We demonstrated high-power broadband Yb-free clad-pumped erbium-doped fiber amplifier (EDFA) using commercial available low-cost 976 nm multimode diodes. An output power +33 dBm with less than ±1 dB natural gain flatness over a gain bandwidth of 33 nm (1570.3–1603.3 nm) was obtained using a new double-clad erbium-doped fiber which has a large core diameter of 17 μm and low NA of 0.11. The saturated output power, net gain, noise figure, and optical power conversion efficiency of the clad-pumped EDFA were characterized, and system impact of LP11 mode and four-wave-mixing nonlinearity were also evaluated.

A frequency comb is generated with a chromium-doped forsterite femtosecond laser, spectrally broadened in a dispersion-shifted highly nonlinear fiber, and stabilized. The resultant evenly spaced comb of frequencies ranges from 1.1 to beyond 1.8 microm. The frequency comb was referenced simultaneously to the National Institute of Standards and Technology's optical frequency standard based on neutral calcium and to a hydrogen maser that is calibrated by a cesium atomic fountain clock. With this comb we measured two frequency references in the telecommunications band: one half of the frequency of the d/f crossover transition in 87Rb at 780 nm, and the methane v2 + 2v3 R(8) line at 1315 nm.

Dispersion properties of novel, tapered, air-silica microstructure fibers are measured between 1.3 and 1.65 microm by white-light interferometry. Dispersion values (beta2) of -181 and -152 ps2/km were obtained for 2.2- and 3-microm core sizes, respectively, at lambda = 1.55 microm.