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

Abstract

Micro-fabrication in transparent materials byfemtosecond laser-induced modification of the optical propertiesinside transparent materials, preferentially optical glasses, hasreceived much attention. Ultra short laser pulses are capable ofinducing these modifications without cracking or even melting theglasses. This kind of modification, which appears as darkeninginside glass relates to the trapped electrons or holes at defectsites in the glass matrix. The femtosecond laser technology allowscontrolling and modifying the optical properties of glasses on asub-micrometer scale. Laser fluence and laser shot number areimportant parameters for femtosecond laser-induced modification ofglasses. This paper presents the 800 nm femtosecond laser-inducedoptical modification inside soda lime glasses at different laserfluence levels and laser shot numbers. Modification thresholds atdifferent applied laser fluences and shot numbers are measured.Pulse energy accumulation model is proposed to predict thebehaviour of darkened area spots with applied laser fluence andshot numbers. Our experimental results and the pulse energyaccumulation model are in good agreement.