Generation of single and double pulses using a symmetrical Mach–Zehnder interferometer employing microstructured chalcogenide fibres: numerical analysis

Abstract

In this numerical work, a Mach–Zehnder interferometer device with sample and reference arms composed of microstructured chalcogenide optical fibres with AsSe2 core and As2S5 cladding is presented to generate single and double pulses. An unchirped hyperbolic secant-shaped pulse with enough high peak power centered at 1958 nm wavelength and a continuous wave with a very weak power level at 2070 nm wavelength are simultaneously introduced into the sample arm, in which stimulated Raman scattering and strong cross-phase modulation induced by two co-propagating waves give rise to a significant phase shift for a continuous wave. In the reference arm, the continuous wave directly passes through the fibre, where the transmitted wave has a slight phase shift due to the influence of self-phase modulation. Therefore, at the output port of the configuration, the re-combined optical fields at 2070 nm wavelength have a significant phase difference. As a result, both single and double pulses caused by the optical interference at the output port are achieved by judiciously adjusting the phase difference which is mainly controlled by the peak power and temporal width of the input optical pulse, as well as the length of a microstructured optical fibre. In addition, both widths of the single pulse and spacing of the double pulses are directly dependent on the temporal width of the input pulse and the fibre length of the arm.