The authors report the fabrication and characterization of InGaAsP/InP rectangular ring laser photonic integration circuits based on active vertical-coupler structure by cascade reactive ion etching/inductively coupled plasma etching technology. This novel etching scheme can efficiently balance the photolithography, masking, and semiconductor etching requirements when several etching depths are demanded. For the 920 μm circumference of ring lasers with coupler length (Lc) of 300 μm, the smallest total threshold current (Ic+Id) of 75 mA is achieved. Varying threshold situation and its sensitivity to the coupling parameters predict that the performance of such devices is not dominated by the nonideal fabrication loss, even though total internal-reflection mirrors are formed by etching twice. Such successful fabrication indicates that this can be widely employed to fabricate the other photonic integrated circuit components where multilevel deep etching is required.