Laser fluence and shot number dependence of laser-induced optical properties modification of transparent materials

摘要

Micro-fabrication in transparent materials by femtosecond laser-induced modification of the optical properties inside transparent materials, preferentially optical glasses, has received much attention. Ultra short laser pulses are capable of inducing these modifications without cracking or even melting the glasses. This kind of modification, which appears as darkening inside glass relates to the trapped electrons or holes at defect sites in the glass matrix. The femtosecond laser technology allows controlling and modifying the optical properties of glasses on a sub-micrometer scale. Laser fluence and laser shot number are important parameters for femtosecond laser-induced modification of glasses. This paper presents the 800 nm femtosecond laser-induced optical modification inside soda lime glasses at different laser fluence levels and laser shot numbers. Modification thresholds at different applied laser fluences and shot numbers are measured. Pulse energy accumulation model is proposed to predict the behaviour of darkened area spots with applied laser fluence and shot numbers. Our experimental results and the pulse energy accumulation model are in good agreement.