Uncladded InGaAsP/InP rib waveguides with integratedthickness tapers forefficient fibre-chip butt coupling

Abstract

The thickness of the waveguide core of uncladded InGaAsP/InP rib waveguides is tapered to fabricate new spot-size transformers without epitaxial regrowth or etching of deep grooves. The coupling loss for flat-end fibres is reduced by 7 dB at alignment tolerances of > ±2 µm for 1 dB excess loss.