Low-loss hybrid fiber with zero dispersion wavelength shifted to 1 μm

Abstract

We propose a novel cylindrically symmetric hybrid fiber design that allows combining properties of the both fibers guiding light due to total internal reflection (low optical losses) and photonic bandgap fibers (anomalous dispersion at 1 μm). Refractive index profile of these fibers consist of the only few layers: low-index core (n core -n silica >0) surrounded with one or more high-index ring layers (n high -n core >0), a depressed layer (n depress -n silica <0) and silica cladding. Operating mode is one of the high-order modes (depending on high-index ring layers number) with intensity maximum at fiber axis. Because the other modes (including the fundamental mode LP 01 ) are guided in the high-index ring layer(s) the hybrid mode can be easily excited by splicing hybrid fiber and standard single-mode (λ~1μm) step-index fiber with appropriate mode field diameter. Moreover method of achievement of asymptotically singlemode regime of light propagation (suppression of the high-index ring layer modes) has been proposed. The main idea of it is doping narrow strong absorbing layer where hybrid mode has intensity of electric field closed to zero. Furthermore we have considered possibility to increase anomalous dispersion of the hybrid fiber (up to 100 ps/nm km) by usage more complicated refractive index profile with two high-index ring layers.In this work we have fabricated the technologically simplest hybrid fiber with the only one high-index layer. The hybrid LP 02 core mode had dispersion of 13 ps/(nm km) and optical loss of about 6 dB/km. Propagation of chirped pulses through the fabricated hybrid fiber allowed us to compress them from 8ps to 330fs.

High-Peak-Power Femtosecond Pulse Generation by Nonlinear Compression in a Yb-Doped Hybrid Fiber

“…In recent years a novel fiber type, hybrid fibers, become a very promising tools for dispersion management [13]- [15]. An appropriate choice for the refractive index profile of such fibers allows for desirable dispersion characteristics (both the dispersion and dispersion slope).…”

“…This mode, which we call a hybrid mode, propagates due to total internal reflection and has zero leakage losses; however, it has many properties that are similar to the properties of a Bragg mode of a photonic bandgap Bragg fiber [6], [7]. The first important property of the hybrid mode is the possibility of achieving anomalous dispersion in the region near 1 μm (dispersion in the range of 10-60 ps/(nm km) has previously been demonstrated near 1.064 μm [13], [14]). The second important property is that the hybrid mode can be efficiently excited by simple fusion splicing with step-index fibers when the MFD is matched to that of the fundamental mode.…”