Hh. Yaffe et al., RESONANT COUPLERS ACTING AS ADD DROP FILTERS MADE WITH SILICA-ON-SILICON WAVE-GUIDE TECHNOLOGY, Journal of lightwave technology, 12(6), 1994, pp. 1010-1014
Add-drop filters are demonstrated using silica-on-silicon optical wave
guide technology. This device consists of a full directional coupler s
ubdivided by Mach-Zehnder sections. Tapering of the coupling coefficie
nts is experimentally shown to dramatically reduce the filters' sidelo
bes. Only one photolithographic step is required using the silica plan
ar waveguide technology, yielding accurate wavelength control of the f
ilters. Excellent agreement between measurement and design was achieve
d.