Dispersion of the nonlinear refractive index in photonic bandgap waveguides

In this paper, we experimentally determine, the dispersion of the nonlinear refractive index near the photonic bandgap of a 21 mm short sample of hollow-core photonic-crystal fiber. For the wavelength dependent measurement, the initially broad laser spectrum near the photonic bandgap edge (1520-1550 nm) is divided into smaller spectral intervals by means of a tunable Fabry-Perot filter. The measurement is based on ReBuS technique, where the nonlinear refractive index of the waveguide under test is measured by referencing its value to the nonlinearity of a bulk sample with well- known nonlinear optical properties.