Tunable twin guide laser diodes with high output efficiency fabricated by an improved reactive ion etching technique

Abstract

An InGaAsP/InP buried heterostructure (BH) tunable twin guide (TTG) laser diode with low threshold current, high output efficiency (over 0.25 W A −1 ) and a tuning range around 2.5 nm has been developed. Since BH laser diodes are highly sensitive to the waveguide quality we have improved the dry etching technique for the definition of the ridge in order to enhance the laser performance. Within the developed reactive ion etching (RIE) procedure a CH 4 /H 2 plasma with optimized composition has been used alternating with short O 2 plasma steps to remove remaining hydrocarbon polymer contamination deposited during the CH 4 /H 2 cycles. The first TTG laser diodes fabricated with this process exhibit up to 30% improved output efficiencies as compared to former devices, and show almost no degradation effects during high temperature lifetime stress.