Nonlinear refractive index n2 is the material parameter, which is used to describe the strength of phenomena caused by third-order nonlinearity, so measuring it accurately is one of the key tasks of nonlinear optics. Several techniques to estimate n2 of the PCF have been demonstrated, but for example Z-scan is not suitable for any type optical fibers, because this method only allows to estimate n2 of the material preform of the PCF. Other methods, such as four-wave mixing, self-phase modulation, cross-phase modulation allow qualitatively good estimation of n2 only when pump wavelength is close to the zero dispersion wavelength (ZDW) of the optical fiber. In this paper, we present a new method of polarization-maintaining photonic crystal fiber nonlinear refractive index measurement using phase shift between orthogonal polarization modes.
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