Abstract : The direct intensity modulation of a three-guide coupled rectangular ring laser having bidirectional lasing characteristics is reported for the first time. The rectangular laser cavity consists of four low loss total internal reflection mirrors and an output coupler made out of three passive coupled waveguides. The laser is fabricated using a total cavity length of 580 μm with active section lengths of 250 μm. For both the clockwise and counterclockwise circulating directions, a lasing threshold of around 38 mA is obtained at room temperature under continuous wave operation. A maximum 3-dB modulation bandwidth of approximately 3.2 GHz is observed in both circulating directions.