Transcript Evanescent fields

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.
Fiber optic phase modulator using
electro-optic material in evanescent field
• 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 electrooptically 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.
InP-Based Optical Waveguide MEMS Switches
With Evanescent Coupling Mechanism
Schematics for 1* 2 couplers: (a) comb-drive coupler in rest
state, (b) comb-drive coupler in actuated state, (c) thirdelectrode coupler in rest state, and
(d) third-electrode coupler in actuated state.
InP-Based Optical Waveguide MEMS Switches
With Evanescent Coupling Mechanism