  The measurement of the hole density in the ferromagnetic semiconductor
Ga$_{1-x}$Mn$_{x}$As is notoriously difficult using standard transport
techniques due to the dominance of the anomalous Hall effect. Here, we report
the first spectroscopic measurement of the hole density in four
Ga$_{1-x}$Mn$_{x}$As samples ($x=0, 0.038, 0.061, 0.083$) at room temperature
using Raman scattering intensity analysis of the coupled plasmon-LO-phonon mode
and the unscreened LO phonon. The unscreened LO phonon frequency linearly
decreases as the Mn concentration increases up to 8.3%. The hole density
determined from the Raman scattering shows a monotonic increase with increasing
$x$ for $x\leq0.083$, exhibiting a direct correlation to the observed $T_c$.
The optical technique reported here provides an unambiguous means of
determining the hole density in this important new class of ``spintronic''
semiconductor materials.
