Patent ID: 7215457

Claim:
A Fabry-Perot etalon filter, the filter comprising: a first partially reflecting mirror; a spacer adjacent the first partially reflecting mirror, wherein the spacer is between the first partially reflecting mirror and a second partially reflecting mirror; an ion conduction layer formed on the spacer; an ion insertion layer that has a dielectric constant and that is adjacent to the ion conduction layer; and a controller that applies an electric field across the ion conduction layer and the ion insertion layer, wherein the applied electric field inserts ions from the ion conduction layer into the ion insertion layer while not substantially altering the transmissivity; wherein: the dielectric constant of the ion insertion layer changes in response to the electric field and modulates a light beam entering the filter; the dielectric constant has a real portion and an imaginary portion; during insertion of the ions into the insertion layer, the real portion changes from a first value to a second value and the imaginary portion changes from a third value to a fourth value; and the absolute value of the difference between the second value and the first value is less than the absolute value of the difference between the fourth value and the third value.