  We propose a stimulated pulsed-radar collider for testing a dilaton model
with the mass of $\sim 10^{-7}$ eV as a candidate of dark energy. We have
extended formulae for stimulated resonant photon-photon scattering in a
quasi-parallel collision system by including fully asymmetric collision cases.
With a pulse energy of 100 J in the GHz-band, for instance, which is already
achieved by an existing klystron, we expect that the sensitivity can reach
gravitationally weak coupling domains, if two key technological issues are
resolved: pulse compression in time reaching the Fourier transform limit, and
single-photon counting for GHz-band photons. Such testing might extend the
present horizon of particle physics.
