<title>Raman amplification in As-Se fiber</title>

Abstract

ABSTRACT We have demonstrated Raman amplification in small core As-Se fiber. We observed over 20 dB of gain in a 1.1-meter length of fiber pumped by a nanosecond pulse of ~10.8 W peak power at 1.50 µm. The peak of the Raman gain was shifted by ~230 cm -1 to 1.56 µm. The Raman gain coefficient is estimated to be about 2.3 x 10 -11 m/W, over 300 times greater than that of silica. The large Raman gain coefficient coupled with the large IR transparency window of these fibers shows promise for development of As-Se Raman fiber lasers and amplifiers in the near, mid and long IR spectral regions. Keywords: Stimulated Raman Scattering, Raman Amplification, Chalcogenide Glass, As-Se 1. INTRODUCTION Stimulated Raman scattering is an important nonlinear interaction that can be exploited to make lasers and amplifiers. Currently, Raman lasers and amplifiers are available commercially in the 1.5 µm wavelength region for telecommunications applications. The use of stimulated Raman scattering allows the manufacture of lasers and amplifiers at wavelengths that are not accessible using traditional rare earth doped materials. However, for applications other than telecommunications, the multiphonon edge of silica glass limits Raman lasers and amplifiers to a wavelength less than 2 µm. In a search for materials with a large Raman gain coefficient and IR transparency beyond 2µm we have investigated chalcogenide glasses. Chalcogenide glasses are composed of one or more of the chalcogen elements, S, Se, and Te, and other elements such as Ge, As, or Sb to form stable glasses. It has been shown that chalcogenide glasses are chemically durable, possess wide glass forming regions, and can be fabricated into low-loss fiber [1]. These glasses are of interest because of their IR transparency and their potential large nonlinearities. Specifically, in this paper we report on Raman amplification in As-Se glass fibers. Figure 1 compares the Raman spectra of As-Se and silica glass. As-Se glass has a much narrower Raman line (~60 cm