Previous analytical solutions for the far-field of a double-heterostru
cture diode laser have been restricted in scope because of several ad
hoc assumptions, which were incorporated at rather early stages of the
analysis. Based on a rigorous solution of the Helmholtz equation, it
is shown that the commonly used assumption of separability of the fiel
d distributions along the two transverse axes of a diode may be mislea
ding under certain conditions. Furthermore, the theoretical upper limi
t on the F.W.H.M. divergence angle is shown to be 65.5-degrees, which
is more realistic than the previous estimate of this parameter.