Spatial Coherency of Light and Nonlinear Optical Properties of Colloidal Gold Studied by CW Z-Scan Technique

Roman V. Gamernyk, Mykola V. Periv, Serhiy Z. Malynych and Oleksandr S. Zaichenko


Nonlinear refraction and absorption of a suspension of Au nanoparticles was studied by CW Z-scan at near-resonant excitation. Spatial coherency and self-interference of the laser beam results in the emerging of ring-like interference pattern observed at the plane of the detector. The number of the interference fringes and their diameter depends on volume fraction of the nanoparticles and laser fluence at focal point. Periodical light intensity distribution across the laser beam causes modulation in the output signal that should be considered for the correct interpretation of Z-scan data.