Nanoprocessing of glass and PMMA by means of near-infrared sub-15 femtosecond laser pulses

摘要

A near infrared sub-15 femtosecond laser scanning microscope was employed for structuring of bulk colored glass and polymethylmethacrylate (PMMA). The 400-mW Ti-Sapphire laser operates at 85 MHz with an M-shaped emission spectrum with maxima at 770 nm and 827 nm. Using a high numerical aperture objective light intensity of about 7 TW/cm2 at the focal plane can be reached. For PMMA a mean power of less than 17 mW, which corresponds to a pulse energy of 0.2 nJ, was sufficient for ablating material. Holes of a diameter of less than 170 nm were produced. Two-photon fluorescence measurements, which can be performed with the same microscope, reveal an extension of the focus length in the specimen, which is most likely caused by self-focusing effects. By applying the same power, the refractive index of the glass could be changed. Islands at the glass surface of a size of less than 100 nm have been produced.