Precise measurement of the Kerr coefficient using phase-sensitive pump-probe hyperspectral imaging

Phase-sensitive pump-probe hyperspectral imaging is a precise technique for absolute two-beam measurements of the optical Kerr coefficient ($n_2$). The irradiance profile is characterized and background effects are rejected by rastering the pump beam across the probe beam to yield a complex-valued hyperspectral image of the pump-induced nonlinear response. Information about the temporal irradiance profile is carried in the spectral response. The technique is demonstrated by measuring $n_2$ of a fused silica sample near 1 $\mu$m wavelength and benchmarked against a measurement using Z-scan [Sheik-Bahae et al., IEEE J. Quantum Electron. 26, 760-769 (1990)], the most commonly used single-beam technique. Good agreement is found when the two-beam grating effect from the Raman contribution to the nonlinearity is considered. Uncertainty contributions are described in detail and the outlook is discussed for improvements in precision.