In order to find and study the nonlinear optical materials with large third-order optical nonlinearities to fabricate optical devices

the third-order optical nonlinearities and dynamic responses of two kinds of squaraine derivatives were measured using femtosecond Degenerate Four-wave Mixing (DFWM) technique at 800 nm. The second-order hyperpolarizabilities of squaraine derivatives are as large as 10

-31

esu

and the response time is shorter than the experimental time resolution of laser. It is clarified that the squaraine derivatives both have large third-order optical nonlinearities and fast optical response under off-resonant conditions

which indicates that the squaraine derivatives have potential applications in nonlinear optics.