Uncoated hollow taper as a simple optical funnel for laser delivery

We propose a simple uncoated hollow taper as a novel technique for laser radiation delivery and laser-to-optical waveguide coupling over a wide spectral range. The principle of operation of the hollow taper is based on the effect of light at grazing incidence. An uncoated Pyrex-glass hollow taper is used for direct launching, without any intermediate focusing elements, of laser radiation including from powerful lasers into the taper. Because of the high reflectance coefficients close to 100% at the light grazing incidence, we obtain high laser-to-taper coupling efficiency exceeding 90% for a He-Ne laser (lambda=632.8 nm) and 80% for a Er:YAG laser (lambda=2.94 mu m). (C) 1999 American Institute of Physics. [S0034-6748(99)02310-2].