Polarization-insensitive InGaAsP/InP vertical coupler filter with deep grating by five-step MOVPE growth

A novel fabrication technique to introduce a deep grating in a vertical cou pler filter was studied in order to realize a polarization-insensitive semi conductor optical add and drop multiplexing device with low crosstalk chara cteristics. The process of fabricating the vertical coupler filter, consist ing of InGaAsP quasi-square waveguides buried in InP and an InGaAsP/InP gra ting between the waveguides, is described. Devices with a grating having a depth of 200 nm were fabricated by a five-step metal organic vapor-phase ep itaxy (MOVPE) process accompanied by reactive ion etching (RIE) and wet etc hing. The deep grating was formed by RIE, and was realized by optimizing su rface treatment prior to MOVPE over-growth and growth conditions. The diffr action efficiency of the filter was successfully improved, and an extremely low crosstalk of - 36dB was achieved. (C) 2000 Elsevier Science B.V. All r ights reserved.