Tapered Waveguide Structure Research Articles

Grating coupler acceptance design utilizing a tapered waveguide structure

A tapered waveguide film was deposited on a substrate with a grating structure resulting in a hybridthin-film waveguide coupler that could be designed for a broader or narrower acceptance for wavelength or incidence angle. The optimized couplers were designed and fabricated. The couplers were found to be as efficient as traditional grating couplers but with much broader acceptance. The maximum broadening was calculated to be a coupling FWHM of 2° (or 12 nm) and was confirmed experimentally. This is 4.3 times the acceptance of an identical untapered structure.

Tapered InP/InGaAsP waveguide structure for efficient fibre-chip coupling

A novel passive InP/InGaAsP waveguide structure for lowloss coupling of monomode fibres to semiconductor devices having waveguides with small elliptical modes has been fabricated. The device consists of a fibre-matched waveguide, a tapered waveguide structure for the necessary mode transformation, and a small spot waveguide. The transformation of the fibre mode into a mode with a spot of 2.0 μm lateral and 1.5 μm vertical extension (FWHM) is demonstrated. Nearly polarisation independent transmission losses, as low as 4.9dB, are measured for uncoated devices with a 900 μm long tapered section.