Reflection loss of laser mode from tilted end mirror

The reflection of the lowest-order guided TE mode of a slab waveguide from a tilted end mirror is discussed. The problem is applicable to injection lasers if the slab is regarded as an effective refractive index approximation of the channel or ridge waveguide of the laser structure. For a mode width of 3 μm, 5° mirror tilt results in reflection losses in excess of 25 dB; for modes of 6-μm width, 5° mirror tilt causes reflection losses in excess of 45 dB. For small tilt angles the results of this calculation agree with those based on a Gaussian approximation of the guided mode. For larger angles, and hence higher reflection losses, the results depart significantly from the Gaussian approximation