  We study the Raman response, for $B_{1g}$ and $B_{2g}$ light-polarization
symmetries, of the charge density wave phase appearing in the underdoped region
of cuprate superconductors. We show that the $B_{2g}$ response provides a
distinctive signature of the charge order, independently of the details of the
electronic structure and from the concomitant presence of a pseudogap, in sharp
contrast with the behavior of the $B_{1g}$ response. This well accounts for the
Raman experimental results. We then clearly identify a charge density wave
energy scale, and show that its doping dependence is eventually driven by the
monotonic behavior of the pesudogap. This has also been pointed out in Raman
experiments, and it is suggestive of a pseudogap ruling the multiple energy
scales of the exotic phases appearing in the cuprate phase diagram.
