OPTICAL 2ND-HARMONIC GENERATION OF (DIMETHYLAMINO)BENZONITRILE MOLECULES INCORPORATED IN THE MOLECULAR-SIEVE ALPO4-5

For (dimethylamino)benzonitrile (DMABN) in the straight Pores of the aluminophosphate molecular sieve AlPO4-5, two components of the second harmonic generation (SHG) have been found. One component of the frequency-doubled radiation is polarized parallel to the length axis (z axis, phi2 = 0-degrees) of the crystal and exhibits the maximum intensity when the excitation beam has the same polarization. The second component, however, is polarized perpendicularly to the z axis (phi2 = 90-degrees) and shows the maximum efficiency for mixed excitation (phi = 45-degrees). Obviously, different components of the hyperpolarizability tensor contribute to the resulting SHG. The reason for the different tensor elements are the two close-lying lowest excited states in DMABN having transition dipole matrix elements perpendicular to each other. In contrast to molecular sieves loaded with p-nitroaniline which arc able to mix waves of the same polarization only, for the DMABN-based materials a mixing of waves of different polarizations is observed. This is a promising property for phase-matching as a prerequisite for a technical application.