Second harmonic generation and two-photon excitation fluorescence from individual nanocrystals of pyrazoline derivatives

We measure the quadratic nonlinear optical properties, namely second harmonic generation (SHG) and two-photon excitation fluorescence (TPEF), of nanocrystals of different derivatives of pyrazoline. The derivatives of pirazoline, like for example DCNP are supposed to have high second order nonlinear susceptibility. We use a nonlinear optical microscopy setup, samples were excited with a femtosecond laser operating at 800 nm wavelength, both signals (SHG and TPEF) were measured simultaneously using a dichroic mirror and for SHG a narrow spectral bandwidth filter centered at 400 nm, respectively. The details of the used nonlinear polarimetric microscopy technique can be found in reference. We have produced the nano-size crystals using the precipitation method and estimated the average size of these nanocrystals to be 300 × 600 nm using atomic force microscopy (AFM).