The effect of strain induced from die bonding on the optical guiding of a ridge-waveguide laser is examined. Measurements of the strain in a p-down-mounted InP-based diode laser with fits to polarization-resolved photoluminescence are used to compute the resulting photoelastic effect in a ridge waveguide. The strain is found to alter the refractive indices in the material sufficiently in the waveguide to change the mode and reduce the optical confinement. In the far field the beam is calculated to be made narrow and asymmetric by the die-bonding strain.