The M 2 factors, beam waists and far field divergence angles of the beams of two kinds real refractive index stripe waveguide semiconductor lasers, plane ridge waveguide and plane buried waveguide lasers, are investigated by means of nonparaxial vector moment theory and plane wave spectrum. The waveguide optical modes were obtained by a semi vectorial 2-D waveguide model. The effects of waveguide structure parameters on M 2 facotor are discussed and the beam properties are compared between the two kinds of laser structures.