title: Pulse-duration dependency of femtosecond laser refractive index modification in poly(methyl methacrylate).
abstract: Refractive index modification of pure poly(methyl methacrylate) (PMMA) is investigated as a function of pulse duration using femtosecond lasers at 800 and 387 nm wavelength. It is observed that at 800 nm, the refractive index is modified more efficiently as the pulse duration decreases below 100 fs, whereas at 387 nm, efficient index modification is accomplished with longer, 180 fs pulses. Results suggest that three- and two-photon absorption is responsible for modification of pure PMMA at 800 nm and 387 nm, respectively. Repeated irradiation with short pulses of low laser fluence allows control of the photomodification via incubation, thus reducing bulk damage.
authors.affiliation: The Photon Science Institute, The University of Manchester, Manchester, UK.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Baum
authors.forename: Patricia J
authors.initials: PJ
authors.lastname: Scully
authors.forename: Walter
authors.initials: W
authors.lastname: Perrie
authors.forename: David
authors.initials: D
authors.lastname: Jones
authors.forename: Riju
authors.initials: R
authors.lastname: Issac
authors.forename: Dino A
authors.initials: DA
authors.lastname: Jaroszynski