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The theoretical calculations presented are similar to those of other authors. The intrinsic threshold of laser diodes is computed on the basis of an electromagnetic propagation calculation. The diode properties are approximated by a sandwich structure for dielectric constant and conductivity. This model differs from the earlier ones by assuming a triangular distribution of dielectric constant and a similar one for the conductivity. In particular, however, allowance is made for a displacement of the peak of the dielectric constant relative to the maximum of inversion, a fact that should be expected from the details of the injection mechanism. The most important result of the calculation is a predicted lower threshold for the TM mode under a wide variety of conditions. This polarization is indeed found in diodes made from dislocation-free GaAs in which laser emission occurs in terms of a relatively wide homogeneous ribbonlike near field.