Coupling to high-index waveguides via tapered microstructured optical fibre
A novel method of coupling to high-index, small mode-field diameter, waveguides using free-standing tapered ‘grapefruit’ microstructured optical fibre pigtails with mode fields down to 1 µm is presented. 0.15 dB mode mismatch loss with chalcogenide rib waveguides is demonstrated, a reduction of more than 5 from high NA fibre, and it is shown that they can be used to butt-couple to silicon nanowires.