Wavelength-flattened fused couplers

A technique is reported for the fabrication of fused couplers, which yields devices having splitting ratios substantially independent of wavelength. A low-loss, stable, single-mode 2×2 port coupler has been fabricated using this technique. The coupler has 50/50% coupling at both 1.3 and 1.52 μm and 50% ± 9% coupling over the wavelength range 1.23 to 1.57 μm.