  We have used electro-reflectance measurements to study charge-density-wave
(CDW) polarization dynamics at voltages near the CDW depinning onset (Von) in
the quasi-one-dimensional conductor K0.3MoO3 ("blue bronze"). For low voltages,
where the phase-slip rate is low, it is expected that the polarization
relaxation time should be inversely proportional to the CDW diffusion constant,
which is expected to diverge at Von. At T=78 K, we observe saturation of the
relaxation time at low voltages, suggesting that we are in the low phase-slip
limit and allowing us to estimate the non-critical value of the CDW diffusion
constant D=0.02cm2/s, consistent with the measured phason velocity. At other
temperatures, the relaxation time increases with decreasing volage even at the
lowest voltages we could measure. In no case do we observe the expected
"critical speeding up", setting an upper limit on the critical region of (V/Von
-1)crit < 0.06.
