Evanescent fields

Professor Viviana Vladutescu

What Everyone Needs to Know About Evanescent Fields

Almost four hundred years ago, Newton used a prism to bend light by total internal reflection. During one experiment, he brought a convex lens into contact with the reflecting face of the prism. To his surprise, light came through the back of the prism across an area larger than the contact area between the two pieces of glass. Somehow, light was propagating a short distance beyond the plane of total internal reflection.Newton had discovered evanescent electromagnetic fields, fields that fade out exponentially within a few wavelengths.

• Document:United States Patent 5007695• Abstract:A cladded optical fiber is secured in a

slot in a substrate which is ground and polished to access the evanescent field. A thin electro-optically active layer of PLZT is deposited on the top of the fiber substrate. A pair of parallel electrodes is then deposited on top of the crystal PLZT film. An electric field distribution parallel to the electro-optical film is generated at the center of the electrode gap by applying a voltage to the electrode pair so as to effect a phase shift of the light wave propagating in the fiber.

Fiber optic phase modulator using electro-optic material in evanescent field

Schematics for 1* 2 couplers: (a) comb-drive coupler in rest state, (b) comb-drive coupler in actuated state, (c) third-

electrode coupler in rest state, and(d) third-electrode coupler in actuated state.

InP-Based Optical Waveguide MEMS SwitchesWith Evanescent Coupling Mechanism

InP-Based Optical Waveguide MEMS SwitchesWith Evanescent Coupling Mechanism