title: Heat accumulation effects in femtosecond laser-written waveguides with variable repetition rate.
abstract: High-repetition rate femtosecond lasers are shown to drive heat accumulation processes that are attractive for rapid writing of low-loss optical waveguides in transparent glasses. A novel femtosecond fiber laser system (IMRA America, FCPA muJewel) providing variable repetition rate between 0.1 and 5 MHz was used to study the relationship between heat accumulation and resulting waveguide properties in fused silica and various borosilicate glasses. Increasing repetition rate was seen to increase the waveguide diameter and decrease the waveguide loss, with waveguides written with 1-MHz repetition rate yielding ~0.2-dB/cm propagation loss in Schott AF45 glass. A finite-difference thermal diffusion model accurately tracks the waveguide diameter as cumulative heating expands the modification zone above 200-kHz repetition rate.
authors.forename: Shane
authors.initials: S
authors.lastname: Eaton
authors.forename: Haibin
authors.initials: H
authors.lastname: Zhang
authors.forename: Peter
authors.initials: P
authors.lastname: Herman
authors.forename: Fumiyo
authors.initials: F
authors.lastname: Yoshino
authors.forename: Lawrence
authors.initials: L
authors.lastname: Shah
authors.forename: James
authors.initials: J
authors.lastname: Bovatsek
authors.forename: Alan
authors.initials: A
authors.lastname: Arai