title: Low bend loss waveguides enable compact, efficient 3D photonic chips.
abstract: We present a novel method to fabricate low bend loss femtosecond-laser written waveguides that exploits the differential thermal stabilities of laser induced refractive index modifications. The technique consists of a two-step process; the first involves fabricating large multimode waveguides, while the second step consists of a thermal post-annealing process, which erases the outer ring of the refractive index profile, enabling single mode operation in the C-band. By using this procedure we report waveguides with sharp bends (down to 16.6 mm radius) and high (80%) normalized throughputs. This procedure was used to fabricate an efficient 3D, photonic device known as a "pupil-remapper" with negligible bend losses for the first time. The process will also allow for complex chips, based on 10's - 100's of waveguides to be realized in a compact foot print with short fabrication times.
authors.affiliation: MQ Photonics Research Centre, Dept. of Physics and Astronomy, Macquarie University, NSW 2109, Australia. alex.arriola@mq.edu.au
authors.forename: Alexander
authors.initials: A
authors.lastname: Arriola
authors.forename: Simon
authors.initials: S
authors.lastname: Gross
authors.forename: Nemanja
authors.initials: N
authors.lastname: Jovanovic
authors.forename: Ned
authors.initials: N
authors.lastname: Charles
authors.forename: Peter G
authors.initials: PG
authors.lastname: Tuthill
authors.forename: Santiago M
authors.initials: SM
authors.lastname: Olaizola
authors.forename: Alexander
authors.initials: A
authors.lastname: Fuerbach
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Withford
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D007834:Lasers; D012031:Refractometry / Q000295:instrumentation*; D020349:Surface Plasmon Resonance / Q000295:instrumentation*