title: Broadband directional couplers fabricated in bulk glass with high repetition rate femtosecond laser pulses.
abstract: A femtosecond fiber laser was applied to fabricate broadband directional couplers inside bulk glass for general power splitting application in the 1250 to 1650-nm wavelength telecom spectrum. The broadband response was optimized over the 400-nm bandwidth by tailoring the coupling strength and the waveguide interaction length to balance the differing wavelength dependence of the straight interaction and bent transition regions. High spatial finesse of the femtosecond-laser writing technique enabled close placement (approxiamtely 6 microm) of adjacent waveguides that underpinned the wavelength-flattened broadband response at any coupling ratio in the 0% to 100% range. The spectral responses were well-represented by coupled mode theory, permitting simple design and implementation of broadband couplers for bulk 3D optical circuit integration.
authors.affiliation: Edward S Rogers Department of Electrical and Computer Engineering, Institute for Optical Sciences, University of Toronto, Toronto, ON, Canada. weijen.chen@utoronto.ca
authors.forename: Wei-Jen
authors.initials: WJ
authors.lastname: Chen
authors.forename: Shane M
authors.initials: SM
authors.lastname: Eaton
authors.forename: Haibin
authors.initials: H
authors.lastname: Zhang
authors.forename: Peter R
authors.initials: PR
authors.lastname: Herman
mesh_terms: D003198:Computer Simulation; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005898:Glass / Q000737:chemistry*; D007834:Lasers; D008027:Light; D008420:Manufactured Materials / Q000528:radiation effects*; D008422:Materials Testing; D008962:Models, Theoretical; D055095:Optics and Photonics / Q000295:instrumentation*; D012031:Refractometry / Q000295:instrumentation*; D012542:Scattering, Radiation