Third order nonlinear optical properties of phenylazo-azulene derivatives investigated by DFWM technique

Organic nonlinear optical (NLO) materials are promising candidates for development of modern technology. Combining molecular engineering and knowledge of materials sciences leads to synthesis of attractive and efficient classes of molecules that can be applied in a wide range of applications such as optoelectronic, photonic devices. For applications in nonlinear optical field, it is established that highly conjugated molecules with push-pull character leads to large nonlinearities. A number of family molecules such carbazole, azulene and so on have been synthesized in this way. We discuss in the present work cubic nonlinear optical properties of three phenylazo-azulene derivatives namely 4-hydroxylphenylazo-1-azulene, 4-aminophenylazo-1-guaiazulene and 4-acetylaminophenylazo-1-azulene. In these structures, azulene fragment acts as donor group, azo and phenyl moieties constitute a pi-conjugated bridge and acceptor character is given by different groups. The compounds were dissolved in tetrahydrofuran (THF) and their third order nonlinear optical activity investigated and determined through degenerate four wave mixing (DFWM) technique working at 532 nm wavelength in picosecond regime. Calculated susceptibility chi(3) values are compared to those of others known NLO materials reported in literature.