Buried waveguides in glass are manufactured by irradiation with femtosecond laser double pulses. The refractive index change Δn is determined by measuring the numerical aperture NA of the waveguides and by through light microscopy. The value of Δn shows a significant dependency on the time delay Δt of the fs-laser double pulses. A Δn of up to 2×10-3 in fused silica is reached at a Δt between 400 and 800 ps. Based on the results of the double pulse experiments the initial effects of the refractive index change are discussed, taking into account thermal effects and the formation of self trapped excitons (STE) and transient color centers and their interaction with the next laser pulse.
© 2007 Optical Society of AmericaFull Article | PDF Article