1.55 μm AlGaInAs/InP quantum well lasers with low beam divergence are theoretically designed and experimentally fabricated. An asymmetrical mode expand layer (MEL) was inserted in lower cladding to expand near field intensity distribution and decrease internal loss. Simulation results showed that the use of MEL won’t influence the laser performance negatively but dramatically decrease the vertical beam divergence at the cost of slightly increase of threshold current. And the experiment results showed high agreement to it. With a 4 μm-wide and 1000 μm-long ridge waveguide laser with MEL, the threshold current and output power of single facet without coating is 56 mA and 17.38 mw@120 mA, and the slope efficiency is 0.272 W/A. The vertical beam divergence is 29.6° and decreases about 35.3% compared to that of typical lasers.