Intensity-varied interferometric autocorrelations for characterisations of optical nonlinearity

Abstract In this work, we present the theoretical framework and experimental setup for intensity-varied interferometric autocorrelations. This is done to resolve the manifestations of multiphoton absorption and saturation, while avoiding the complexities of analogous techniques. Our system is demonstrated with the standardised wavelength of 1550 nm, at the centre of the optical communication band, and a conventional silicon photodiode, whose bandstructure allows for multiple pathways for multiphoton absorption. With this system, we see the silicon exhibit negligible one-photon absorption, strong two-photon absorption for intensities up to 160 GW cm −2 , strong three-photon absorption for intensities between 160 and 350 GW cm −2 , and saturation for intensities above 350 GW cm −2 . Ultimately, such results suggest that the proposed theoretical framework and experimental setup are effective tools for nonlinear characterisations of multiphoton absorption and saturation.