Effects of few optical cycles approximation to spectral broadening generated in two-zero dispersion wavelengths fibers

Abstract

It is both experimentally and numerically confirmed that Supercontinuum can be generated by pumping a few-tens-femtoseconds short pulse in anomalous dispersion region of a two zero-dispersion wavelengths (ZDW) fiber, such as, photonic crystal fiber. In numerical method, a well-known slowly varying envelope approximation (SVEA) has always been used to illustrate how the short pulse expands to a broadband spectrum in two-ZDWs fiber. But, the limit of SVEA is that it can only be applied for the short pulse, which its temporal envelope changes slowly comparing with its optical cycle. However, a few optical cycles short pulse is not fit with the condition of the SVEA approximation. In this report, another model, namely slowly evolving wave approximation (SEWA), is applied for numerical demonstration of supercontinuum generated by pumping the few optical cycles short pulse in two-ZDWs fiber. According to our simulation, under SEWA the final spectral width of the very short input pulse in the two-ZDWs fiber is between about 500 - 2000 nm, even the center wavelength of input pulse is near second-ZDW of fiber. Moreover, other effects of these two approximations since the center wavelength of the very short input pulse is close to both upper and lower ZDWs of the fiber in the same fiber’s length are also compared in our presentation.