RIE lag directional coupler based integrated InGaAsP/InP ring mode-locked laser

Abstract

We have demonstrated the first integrated ring mode-locked laser (MLL) with a reactive ion etch (RIE) lag coupler. The RIE lag directional coupler (RL-DC) is highly advantageous for integrated MLLs as it has an insertion loss <1 dB and can be designed to provide any coupling value. This provides the RL-DC with a much needed flexibility in large photonic systems unlike standard multimode interference (MMI) couplers, which typically provide only 3 dB power splitting.