title: Femtosecond laser writing of optical edge filters in fused silica optical waveguides.
abstract: The positional alignment of femtosecond laser written Bragg grating waveguides within standard and coreless optical fiber has been exploited to vary symmetry and open strong optical coupling to a high density of asymmetric cladding modes. This coupling was further intensified with tight focusing of the laser pulses through an oil-immersion lens to control mode size against an asymmetric refractive index profile. By extending this Bragg grating waveguide writing into bulk fused silica glass, strong coupling to a continuum of radiation-like modes facilitated a significant broadening to over hundreds of nanometers bandwidth that blended into the narrow Bragg resonance to form into a strongly isolating (43 dB) optical edge filter. This Bragg resonance defined exceptionally steep edge slopes of 136 dB/nm and 185 dB/nm for unpolarized and linearly polarized light, respectively, that were tunable through the 1450 nm to 1550 nm telecommunication band.
authors.affiliation: Institute for Optical Sciences, and the Department of Electrical and Computer Engineering, University of Toronto, 10 Kings College Rd., Toronto, Ontario, M5S 3G4, Canada. j.grenier@utoronto.ca
authors.forename: Jason R
authors.initials: JR
authors.lastname: Grenier
authors.forename: Luís A
authors.initials: LA
authors.lastname: Fernandes
authors.forename: Peter R
authors.initials: PR
authors.lastname: Herman
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D005374:Filtration / Q000295:instrumentation*; D007834:Lasers; D012031:Refractometry / Q000295:instrumentation*; D012822:Silicon Dioxide / Q000737:chemistry* / Q000528:radiation effects*; D013499:Surface Properties / Q000528:radiation effects
chemical_list: D012822:Silicon Dioxide