GHz burst mode femtosecond laser processing for improving resolution of two-photon polymerization

This study examines two-photon polymerization (TPP) of SU-8 using GHz burst pulses of green wavelength fs laser by both experimental and simulation approaches. We show that by using the GHz burst pulses with an intra-pulse number of P = 10, the polymerization threshold energy of intra-pulses is 60% smaller than that of the conventional single-pulse mode and the TPP resolution is improved by 37%. The simulation results reveal that the fabrication of smaller polymerized structures with a lower threshold energy could be originated from the accumulation of thermal energy during irradiation of the subsequent intra-pulses in the GHz burst.