A method of phase retrieval from the experimental modulus |χ(3)| spectra of third-order nonlinear optical susceptibility is presented on the basis of the maximum-entropy model. This method enables one to derive the real and the imaginary parts of χ(3) without using the nonlinear Kramers-Kronig calculation, which is usually hazardous in nonlinear optical spectroscopy because of the limited range of measurements. Theoretical and experimental modulus spectra of polysilane are analyzed. The results from the experimental modulus are compared with the Kramers-Kronig calculations as well as with the measured phase values. It is also shown how the method can be optimized to reduce the distortions that result from noise in the calculated spectra.
© 1996 Optical Society of America
E. M. Vartiainen, K.-E. Peiponen, H. Kishida, and T. Koda, "Phase retrieval in nonlinear optical spectroscopy by the maximum-entropy method: an application to the |χ(3)| spectra of polysilane," J. Opt. Soc. Am. B 13, 2106-2114 (1996)