Two-port InGaAsP/InP square resonator microlasers with a side length of 20 mm have been fabricated by the planar technology process, which have two 1 mm-wide output ports connected to the vertices of the square resonator. Continuous-wave electrically injected microsquare lasers have been realised at room temperature with mode Q-factors of 1.75 × 10 4 at the threshold current.Introduction: Microcavity lasers fabricated by planar technology processes are potential light sources in photonic integrated circuits. Microdisc lasers have attracted a great deal of attention in the past two decades owing to their low threshold and small cavity volume. To obtain directional emission and high power output, various schemes of deformed circular cavities were proposed, such as quadrupolar shaped cylinder laser [1], spiral-shaped micropillars [2], stadiumshaped polymer microlasers [3], and limaçon-shaped chaotic microcavity [4]. In addition, square resonators were also investigated for possible device applications too [5][6][7], and directional emission square resonator microlasers were fabricated with an output waveguide connected to the mid-point of one side of the resonator [8,9].In this Letter, we report the lasing characteristics of InGaAsP/InP square resonator microlasers with two output waveguides connected to the vertices of the square resonator, which can be used to build twodimensional blocks in photonic circuits for optical signal processing.