A room temperature measurement is made of the IR‐pump‐laser induced external defocusing of a Gaussian shaped probe‐beam transmitted at a fixed wavelength at the band edge of CdSxSe1−xmixed crystal (x = 0.65). From the probe‐beam expansion factor the negativ dispersive change at the band edge resulting from the excess free‐carrier concentration Ne generated by the IR‐pump‐beam via two‐photon interband absorption is calculated and compared with the value ob‐tained in a pump‐beam selfdiffraction experiment. Already at Ne = 1.3 × 1016 cm−3 a dispersive change of −Δn = 1 × 10−4 is found. Moreover, at the band edge an increase of the probe‐beam transmission is measured indicating a maximum absorptive change which is about four times smaller than k Δn. Therefore, at higher excitation levels the higher transmission signal expected will be limited by defocusing.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.