A new type of double-heterojunction lateral current injection GaAs/AIGaAs p-i-n ridge waveguide laser is described. The device employs intrinsic materials in the active region to reduce the parasites in the laser, thereby lowering the required threshold current and increasing the quantum efficiency of the device. The use of ridge waveguide structure provides better optical confinement than the conventional lateral injection lasers and avoids the regrowth required for buried heterostructure transverse junction stripe (TJS) lasers. Two-dimensional self-consistent simulations have been carried out, using our finite-element light emitter simulator (FELES), for the purpose of proof of concept and evaluation of the device operation and performance. The results show that the device has a low threshold current, a good differential efficiency, a low capacitance (0.028 pF at zero bias), and a low dynamic resistance (< 2.3 Ω).