title: Lensed-taper launching coupler for small-bore, infrared hollow fibers.
abstract: A new type of launching coupler for small-bore, hollow fibers, consisting of a lens and a tapered hollow waveguide, is proposed to increase the alignment tolerance between an input laser beam and small bore fibers. First, we designed the structural dimensions of the coupler by using a ray-tracing method. Then, a series of experiments employing tapered hollow waveguides made of Pyrex glass was performed to investigate the effectiveness of the new coupler. It is shown that the coupler has a high efficiency with attenuation of around 0.5 dB, especially when the inside of the taper section is coated with a polymer and silver film. In addition, we also show that the coupler has great tolerance for the transverse displacement of a waveguide axis, which gives a 0.1-dB loss increase for a 300-mum displacement.
authors.forename: Y
authors.initials: Y
authors.lastname: Matsuura
authors.forename: H
authors.initials: H
authors.lastname: Hiraga
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
authors.forename: Y
authors.initials: Y
authors.lastname: Kato
authors.forename: M
authors.initials: M
authors.lastname: Miyagi
authors.forename: S
authors.initials: S
authors.lastname: Abe
authors.forename: S
authors.initials: S
authors.lastname: Onodera