Fabrication of 1 x 8 multimode-interference optical power splitter based on InP using CH4/H-2 reactive ion etching

1 x 8 multimode-interference (MMI) power splitters with a weakly guided rid ge structure based on an InGaAsP/InP material for 1.55 mum operations were designed and fabricated. To determine the optimum etching condition of InP in CH4/H-2 plasma for the formation of MMI power splitters. the effects of etching parameters, such as ROW rates of constituent gases, rf power, and p rocess pressure on the etch rate and surface morphology were investigated. The fabricated 3-mum-wide adjacent straight waveguides have propagation los ses of 2.91 dB/cm at 1.55 mum for transverse electric (TE) polarization. Th e device performances in terms of the thickness of the upper cladding layer were theoretically and experimentally compared. The polarization dependenc e of the MMI power splitters was investigated. For TE [transverse magnetic (TM)] polarization, the excess loss of the devices at an operating waveleng th of 1.55 mum was 1.02 dB (1.95 dB) and the splitting ratio was 0.68 dB (1 .13 dB).