  We suggest that coherent radiation may occur in relativistic collisionless
shocks via two-stream Weibel instabilities. The coherence amplifies the
radiation power by many orders [$\sim 10^{12}$ in Gamma-Ray Bursts (GRBs)] and
particles cool very fast before being randomized. We imply (1) GRBs accompany
strong infrared emission, (2) protons efficiently transfer energy to electrons
and (3) prompt GRBs might be the upscattered coherent radiation.
