How do changes in the Drude frequency of a material change its conductivity?

When reading how the Drude plasma frequency affects the conductivity of a material to THz waves (in this case a Si modulator) I am told that:

"In high resistivity Si, the Drude plasma frequency is below the THz range, resulting in a dielectric material response. But upon intense optical excitation, the number of charge carriers increases, moving the Drude plasma’s frequency above the THz range, resulting in bad conductivity."

I know that the optical excitation leads to the production of more free electrons, thus increasing the current (as explained in these lectures). But how is the Drude plasma frequency related to this?

How is the Drude plasma frequency related to the response/conductivity of the material to the THz signal?

I know that the Drude plasma frequency follows the equation below, but I still don’t truly understand its meaning and therefore I don’t know how it changes the material’s response to the signal.

$$omega_p= sqrt{frac{ne^2}{epsilon_0 m}}$$