Multiplex method for the measurement of nonlinear susceptibility spectrum applied to third-harmonic generation in a polydiacetylene

Broadband near-infrared pulse generated from NOPA (non-collinear optical parametric amplifier) was used for measurement of the spectrum of susceptibility of the third harmonic generation (THG). Corrections for the effects of absorption and refractive index, contribution of non-degenerate third-order nonlinearity, and THG by air, were properly addressed. ultiplex method was applied to a polydiacetylene, poly[5,7-dodecadiyn-1,12-diol-bis(n-butoxylcarbonyl-methyl-urethane)] (4BCMU) in red phase resulting in a good agreement with theoretical prediction.