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 (n2). The irradiance profile is characterized and background effects 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 n2 of a fused silica sample near a 1 μm wavelength and benchmarked against a measurement using Z-scan [M. Sheik-Bahae et al., IEEE J. Quantum Electron. 26, 760–769 (1990)], the most widely used single-beam technique. The two measurements are consistent 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.