Uncoated hollow taper as a simple optical funnel for laser delivery

We propose a simple uncoated hollow taper as a novel technique for laser ra diation delivery and laser-to-optical waveguide coupling over a wide spectr al range. The principle of operation of the hollow taper is based on the ef fect 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 t he high reflectance coefficients close to 100% at the light grazing inciden ce, we obtain high laser-to-taper coupling efficiency exceeding 90% for a H e-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].