Suppressing fluctuation of chromatic dispersion and signal gain performances in a chalcogenide buffer step-index optical fiber

Abstract

Fiber-based optical parametric amplification (FOPA) has been exploited for various applications due to its broad gain bandwidths and high signal gain in many spectral bands. By extending FOPA gain bandwidth towards the mid-infrared (MIR) region, more novel applications in spectroscopy, sensing, biology and so on are expected to be realized. However, highly efficient and stable FOPA performance is not easy to be obtained. It requires optical fibers with high nonlinearity, suitable control of chromatic dispersion and pump sources to satisfy the phase-matching condition which is the key for FWM process to occur. Among non-silica glasses, chalcogenide glasses have attracted great attention due to their very broad transmission window in MIR region and very high nonlinearity. For these reasons, this work is highly motivated to control and maintain the chromatic dispersion of chalcogenide optical fibers so as to achieve and maintain high-intensity and broad FOPA signal gain bandwidths in the MIR region by using an AsSe2 step-index optical fiber and a pump source near 5.0 μm. It is realized that by adding a chalcogenide buffer layer with appropriate refractive index and diameter to the conventional step-index structure, the performances of chromatic dispersion and FOPA can be improved and their fluctuation due to the change of fiber core can be greatly suppressed. As a result, a broad signal gain bandwidth from 3 to 14 μm at about 15 dB is attainable and can be maintained although the fiber core diameter drastically fluctuated from 2 to 5 μm.