Investigation of supercontinuum generation in specialty fibers

Abstract

Supercontinuum generation has sparked much interest in the field of nonlinear optics for over several decades, due to a broad range of applications in the medical, industrial and research fields. Particularly, supercontinuum generation with good flatness and broad spectral bandwidth in the mid-infrared region has potential applications in spectroscopy, materials processing, chemical and bio-molecular sensing, security and industry. Supercontinuum generation is achievable through the use of ultra short pulses in the femtosecond or picosecond regime and with the use of highly nonlinear fibers. A highly nonlinear fiber is one kind of specialty fiber that is not only designed for guiding light beams but also for new frequency generation. Such highly nonlinear fibers can be achieved by physical modification of its fiber structure such as a change of core and cladding geometry as well as doping additional material in fiber with high nonlinearity. When an optical pulse with high intensity passes through a highly nonlinear fiber, the dispersive effect and the optical Kerr effect take place and that can lead to the formation of a flat and broadband optical spectrum. In this report, the numerical simulation is mainly conducted for producing supercontinuum spectrum with good flatness and broad spectral bandwidth. Through the use of the model based on Nonlinear Schrodinger’s Equation (NLSE), which governs the occurrence of these nonlinear and dispersive processes, an understanding of the processes can be achieved. The NLSE is solved through the use of split-step Fourier method. In the simulation, various parameters of the fiber such as group velocity dispersion, nonlinear coefficient, fiber length as well as the parameters of input pulse such as peak power and pulse width can be changed and optimized in order to get substantial spectral broadening and good flatness.