Optical nonlinearities of antimony thin film studied with picosecond laser pulses

In laser applications such as optical data storage and photolithography, focused spot size can be reduced beyond the diffraction limit with an optically nonlinear medium. Using the transmittive and reflective Z-scan technique with a 10 Hz, frequency doubled, Q-switched and mode-locked Nd:YAG laser, the beam shrinkage with an Sb thin film is confirmed. We infer that plasma reflection is the mechanism.