Embedded nanogratings in germanium dioxide glass induced by femtosecond laser direct writing

We report on the formation of embedded self-organized, polarization-dependent nanogratings in germanium dioxide glass induced by an 800 nm, 1 kHz femtosecond laser. Optical birefringence was observed to vary with the femtosecond laser polarization in both cases by translating the sample along and perpendicular to the laser propagation direction. Raman spectroscopy indicated that the irradiated area suffered a network distortion. Scanning electron microscopy images of the written lines reveal the formation of periodic planar nanocrack arrays that are aligned perpendicularly to the laser polarization direction after chemical etching. The influences of laser pulse energy and scanning speed on the period of the nanogratings are investigated. The embedded nanogratings in GeO2 glass may find potential applications in optical recording, waveguide fabrication, and other micro-optical devices. (C) 2014 Optical Society of America