title: CO2 laser induced refractive index changes in optical polymers.
abstract: We study the infrared photosensitivity properties of two optical polymer materials, benzocyclobutene (BCB) and epoxy OPTOCAST 3505, with a 10.6 μm CO2 laser. We discover that the CO2 laser radiation can lower the refractive index of BCB by as much as 5.5 × 10(-3), while inducing no measurable index change in the epoxy. As confirmed by Fourier transform infrared spectroscopy, the observed index change in BCB can be attributed to photothermal modification of chemical bonds in the material by the CO2 laser radiation. Our findings open up a new possibility of processing polymer materials with a CO2 laser, which could be further developed for application in the areas of post-processing and direct-writing of polymer waveguide devices.
authors.affiliation: Department of Electronic Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Hong Kong, China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Liu
authors.forename: Kin Seng
authors.initials: KS
authors.lastname: Chiang
authors.forename: Laurence
authors.initials: L
authors.lastname: Reekie
authors.forename: Yuk Tak
authors.initials: YT
authors.lastname: Chow
mesh_terms: D054020:Lasers, Gas; D008422:Materials Testing; D011108:Polymers / Q000737:chemistry* / Q000528:radiation effects*; D012031:Refractometry / Q000379:methods*
chemical_list: D011108:Polymers