Mid-infrared soliton self-frequency shift using ultra-low pump pulse energy

Abstract

Mid-infrared (MIR) fiber based optical sources, such as wavelength converters that are based on soliton-self frequency shift (SSFS), parametric processes or supercontinuum sources are attractive for their compactness and mechanical stability [1] – [3] . Of particular interest, wavelength converters based on SSFS can generate widely tunable, high quality ultrashort pulses from a dispersion engineered nonlinear fiber paired with a suitable pulsed source [4] . There have been a few reports of SSFS in silica [5] , fluoride [6] and tellurite [7] fibers. Among soft glass fibers, chalcogenide (ChG) fibers (e.g As 2 Se 3 , As 2 S 3 ) are particularly attractive for SSFS in the MIR due to their compatibility with this spectral range as well as their high optical nonlinearity. In addition, the tapering of a ChG fiber down into a microwire provides an enhanced nonlinear optical effect, thus allowing low pump power operation from a compact device. In the past, Cheng et al. reported SSFS tunable in the spectral range of 2.98-3.41 μm (12.7 THz) in AsSe 2 fibers from pulses with an energy of 1.8 nJ [8] . In this work, we report SSFS that is widely tunable within the spectral range of 2.03-2.60 μm (39.2 THz) from a pump pulse energy as low as 64 pJ. Such a frequency detuning is realized from dispersion engineering of an As 2 S 3 microtaper. To the best of our knowledge, this is the lowest pump energy ever used to obtain wideband SSFS.