varying permittivity

[karlzr]

I read from a paper that we can generate the permittivity variation by low-frequency electro-optic modulation.
So, does anyone know, how this modulation changes the permittvity? or a link will be appreciated!

[Andy Resnick]

In acousto-optic devices, the permittivity changes due to changes in the density. Do you have a link to a specific device?

[karlzr]

In acousto-optic devices, the permittivity changes due to changes in the density. Do you have a link to a specific device?

No, I just want to know whether it is technically difficult to make it, for instance, to increase linearly or exponentially.
How to control it? is it due to the influence of external electromagnetic field or something else?