  We have extended a simple model of nonlinear diffusive shock acceleration
(Berezhko and Ellison 1999) to include the injection and acceleration of
electrons and the production of photons from bremsstrahlung, synchrotron,
inverse-Compton, and pion-decay processes. We argue that the results of this
model, which is simpler to use than more elaborate ones, offer a significant
improvement over test-particle, power-law spectra which are often used in
astrophysical applications of diffusive shock acceleration. With an
evolutionary supernova remnant (SNR) model to obtain shock parameters as
functions of ambient interstellar medium parameters and time, we predict
broad-band continuum photon emission from supernova remnants in general, and
SN1006 in particular, showing that our results compare well with the more
complete time-dependent and spherically symmetric nonlinear model of Berezhko,
Ksenofontov, and Petukhov (1999). We discuss the implications nonlinear shock
acceleration has for X-ray line emission, and use our model to describe how
ambient conditions determine the TeV/radio flux ratio, an important parameter
for gamma-ray observations of radio SNRs.
