Nonlinear optical properties of polar merocyanine J-aggregates

The multipurpose nonlinear optical microscope was applied to elucidate the structure of J-aggregate assembly (JA) of merocyanine dye (MD) in the monol ayer. It was revealed that the two-dimensional cigar-shaped JA with noncent ro-symmetric arrangement of MD along the assembly plane was formed, with th e polar axis inclining by about 30 degrees from the long axis of the assemb ly. The second harmonic generation (SHG) of the MD monolayer was first meas ured as a function of the fundamental wavelength and the resonant SHG spect rum was observed at the J-band.