Dynamic diffractive optical transform

• US 20050017925A1
• Filed: 08/09/2004
• Published: 01/27/2005
• Est. Priority Date: 01/11/1995
• Status: Active Grant

• Current Assignee: William Arthur Birdwell
• Original Assignee: William Arthur Birdwell
• Inventors: Birdwell, William A.
• Granted Patent: US 7,009,581 B2
• Time in Patent Office: Days
• US Class Current: 345/48
• CPC Class Codes: G02F 1/292 by controlled diffraction or phased-array beam steering controlled diffraction for optical switching G02F1/31
• CPC Class Codes: G02F 1/31 Digital deflection, i.e. optical switchingG02F1/33 takes precedence
• CPC Class Codes: G03H 2222/32 Unpolarised light
• CPC Class Codes: G03H 2225/32 Phase only

Abstract

A dynamic diffractive optical transform. An electric field pattern is created across a body of material, the material being characterized in that it has an optical transmission property which varies in response to of an electric potential applied across a portion thereof. The electric field pattern is created such that the resulting profile of the transmission property is an arbitrary shape which produces a desired diffraction pattern that may not be physically realizable in conventional refractive optics or is a Fresnel lens-like construct derived from a refractive optical element. This is done by selectively applying electric potentials to transparent electrode pairs having liquid crystal material therebetween and preferably relatively small proportions in relation to the relevant wavelength of light, so as to create variations in phase delay that are aperiodic, have other than fifty percent spatial duty factor or have multiple levels of phase delay. The transform is embodied in an optical scanner, an adaptive lens, and an optical switch.

Claims

1. An optical switch, comprising:

a first port, having;

a body of material having a first surface and a second surface, said second surface being non-orthogonal to said first surface, said material being characterized in that it produces a phase delay which varies in response to an electric potential applied across a portion of said material,

a plurality of substantially-transparent electrodes disposed adjacent said first surface of said material, said electrodes being arranged in a predetermined pattern and having predetermined respective sizes and spacings with respect to at least one dimension x,

at least one substantially-transparent electrode disposed adjacent said second surface of said material in predetermined relation to said electrodes disposed adjacent said first surface, and

control means, connected to said electrodes disposed adjacent said first surface and at least said one electrode disposed adjacent said second surface so that said material is effectively partitioned into a plurality of diffractive optic components, each said component corresponding to one or more of said electrodes disposed adjacent said first surface, for applying selected electric potentials to respective said electrodes adjacent said first surface relative to an electrode adjacent said second surface so as to cause said phase delay to vary with respect to said dimension x substantially as follows;

D(x)=D₀(x)+F(x)(mod D_max)

where

D(x)=phase delay with respect to said dimension x in response to said control means,

D₀(x)=phase delay in the absence of any electric field with respect to said dimension x,

F(x)=a selected variation in phase delay with respect to said dimension x,

D_max) a predetermined maximum permissible value of phase delay, greater than zero and less than the maximum value of F(x), over a first predetermined range of x,

where D(x)−

D₀(x)=0 at some point over a second predetermined range of x and F(x) (mod D_max)) is aperiodic, has a selectable spatial duty factor or has more than one non-zero value over said first predetermined range of x, and

a second port having a surface disposed in spaced, non-orthogonal relation to said first and second surfaces of said first port so that light may be coupled between said first port and said second port, said control means including means for mapping an optical wavefront pattern illuminating said first port to a predetermined wavefront pattern at said second port.

2. The optical switch of claim 1, wherein said body of material comprises liquid crystal material, said electrodes are disposed on respective substantially-flat transparent substrates substantially parallel to one another, said first electrodes comprise at least one array of elongate, substantially-parallel strips which have predetermined width and predetermined spacing and extend in a dimension perpendicular to said x dimension, and said second port comprises a plurality of predetermined regions disposed along said dimension x on said third surface, said control means including means for coupling light between one or more selected regions disposed along said dimension x on a surface of said first port and respective said regions on said third surface.

3. The switch of claim 2, wherein said second port is substantially identical to said first port.

4. The switch of claim 2, further comprising:

polarization component separation means, disposed adjacent said first port, for receiving a light beam, separating said light beam into a first component having a first, predetermined polarization and a second component having a second polarization orthogonal to the polarization of said first component, altering the polarization of said second component so as to be substantially the same as said predetermined polarization of said first component, and directing said first and second components through said first port in substantially parallel relation to one another, and

a plurality of polarization component combining means, disposed adjacent said second port along said dimension x, for receiving said first component and said second component, altering the polarization of said first or second component so that the respective polarizations of said first component and said second component bear the same relationship as they did prior to alteration of the polarization of said second component by said polarization component separation means, and recombining said first and second components into a single light beam.

5. The switch of claim 1, wherein D_max=2π

radians.

6. The switch of claim 1, wherein said control means includes means for selectively applying potentials to respective predetermined groups of one or more electrodes adjacent said first surface of said first port relative to electrodes adjacent said second surface of said first port.

7. The switch of claim 1, wherein D_max=2π

radians, F(x)=L(x)+Q(x), where L(x) increases or decreases substantially linearly over said second predetermined range of x, and Q(x) is an adjustment value less than 2π

radians.