Reflective liquid crystal spatial light modulator

• US 20070076163A1
• Filed: 11/30/2006
• Published: 04/05/2007
• Est. Priority Date: 10/04/1999
• Status: Abandoned Application

• Current Assignee: Thomas Swan & Company Limited (Aixtron AG)
• Original Assignee: Thomas Swan & Company Limited (Aixtron AG)
• Inventors: Crossland, William, Holmes, Melanie, Robertson, Brian, Wilkinson, Timothy, Redmond, Maura, Manolis, Ilias
• Application Number:
  US11/607,770
• Publication Number:
  US 20070076163A1
• Time in Patent Office: Days
• US Class Current: 349/196
• CPC Class Codes: G02B 5/32 Holograms used as optical elements
• CPC Class Codes: G02B 6/264 with optical elements between opposed fibre ends which perform a function other than beam splitting having lens focusing means G02B6/32; utilising prism or grating G02B6/34
• CPC Class Codes: G02B 6/32 having lens focusing means positioned between opposed fibre ends with lens being an integral part of the single fibre end G02B6/262
• CPC Class Codes: G02F 1/133638 Waveplates, i.e. plates with a retardation value of lambda/n
• CPC Class Codes: G02F 1/136277 formed on a semiconductor substrate, e.g. of silicon
• CPC Class Codes: G02F 1/1393 the birefringence of the liquid crystal being electrically controlled, e.g. ECB-, DAP-, HAN-, PI-LC cells G02F1/1396, G02F1/141 take precedence
• CPC Class Codes: G02F 1/1395 Optically compensated birefringence [OCB]- cells or PI- cells
• CPC Class Codes: G02F 1/141 using ferroelectric liquid crystals
• CPC Class Codes: G02F 1/31 Digital deflection, i.e. optical switchingG02F1/33 takes precedence
• CPC Class Codes: G02F 2203/02 reflective
• CPC Class Codes: G02F 2203/12 spatial light modulator
• CPC Class Codes: G02F 2203/50 Phase-only modulation
• CPC Class Codes: G03H 1/0005 Adaptation of holography to specific applications holographic optical element G02B5/32; holographic scanner G02B26/106; recognition using holographic mask G06V10/88; holographic memories G11B7/0065, G11C13/042
• CPC Class Codes: G03H 1/02 Details of features involved during the holographic process; Replication of holograms without interference recording
• CPC Class Codes: G03H 1/08 Synthesising holograms, i.e. holograms synthesized from objects or objects from hologramsusing electric digital computers G06F; G06T
• CPC Class Codes: G03H 1/2294 Addressing the hologram to an active spatial light modulator
• CPC Class Codes: G03H 2001/0224 Active addressable light modulator, i.e. Spatial Light Modulator [SLM] corresponding details, see subgroups of G03H2225/00
• CPC Class Codes: G03H 2001/0825 Numerical processing in hologram space, e.g. combination of the CGH [computer generated hologram] with a numerical optical element
• CPC Class Codes: G03H 2001/085 Kinoform, i.e. phase only encoding wherein the computed field is processed into a distribution of phase differences
• CPC Class Codes: G03H 2001/221 Element having optical power, e.g. field lens
• CPC Class Codes: G03H 2001/261 : in optical contact
• CPC Class Codes: G03H 2001/306 : Tiled identical sub-holograms
• CPC Class Codes: G03H 2210/20 : 2D object
• CPC Class Codes: G03H 2222/31 : Polarised light
• CPC Class Codes: G03H 2222/32 : Unpolarised light
• CPC Class Codes: G03H 2222/34 : Multiple light sources
• CPC Class Codes: G03H 2223/19 : Microoptic array, e.g. lens array
• CPC Class Codes: G03H 2223/20 : Birefringent optical element, e.g. wave plate
• CPC Class Codes: G03H 2225/22 : Electrically addressed SLM [EA-SLM]
• CPC Class Codes: G03H 2225/32 : Phase only
• CPC Class Codes: G03H 2225/52 : Reflective modulator
• CPC Class Codes: G03H 2227/03 : Means for moving one component G03H1/0476, G03H2001/2695 take precedence
• CPC Class Codes: G03H 2240/41 : Binary
• CPC Class Codes: H04Q 2213/1301 : Optical transmission, optical switches
• CPC Class Codes: H04Q 2213/1319 : Amplifier, attenuation circuit, echo suppressor

Abstract

An optical switch uses a polarisation insensitive spatial light modulator operating by a double pass through a liquid crystal cell. The switch includes two such modulators in a cross bar arrangement. Different embodiments employing techniques for reducing cross talk are described.

Claims

1-30. -30. (canceled)

31. A reflective liquid crystal spatial light modulator comprising

a two dimensional array of a plurality of reflective pixel electrodes;

each reflective electrode defining a respective pixel,

the reflective liquid crystal spatial light modulator further comprising

a quarter wave plate disposed on the reflective electrodes,

a liquid crystal layer disposed over the quarter wave-plate, and

a transparent conductive layer over the liquid crystal layer, wherein the transparent conductive layer forms a common electrode plane to said array, the common electrode plane completely overlaying said plurality of the reflective electrodes.

32. The reflective liquid crystal spatial light modulator of claim 31, wherein said liquid crystal layer is a nematic liquid crystal layer.

33. The reflective liquid crystal spatial light modulator of claim 31, wherein said liquid crystal layer is a π

-cell.

34. An integrated spatial light modulator for light of a predetermined wavelength, the integrated spatial light modulator comprising:

a transparent common electrode,

a plurality of reflective electrodes,

a retardance layer having an optical retardance of an odd integer number of quarter-waves of said predetermined wavelength, the retardance layer being disposed on the plurality of reflective electrodes; and

a liquid crystal layer,

wherein the liquid crystal layer is disposed between the retardance layer and the transparent common electrode, wherein the liquid crystal layer is disposed and configured to provide out-of-plane tilt in response to voltage applied across the liquid crystal layer between the reflective electrodes and the transparent common electrode;

wherein the reflective electrodes are reflective pixel electrodes disposed in a regular two-dimensional array, and the transparent common electrode completely overlays said plurality of reflective electrodes.

35. The integrated spatial light modulator of claim 34, wherein said liquid crystal layer is a nematic liquid crystal layer.

36. The integrated spatial light modulator of claim 34, wherein said liquid crystal layer is a π

-cell.

37. The integrated spatial light modulator of claim 34 further comprising voltage application circuitry for applying desired voltages across the liquid crystal layer whereby the liquid crystal layer has desired values of out of plane tilt;

the arrangement being such that application of voltage to each electrode causes a respective portion of the liquid crystal layer associated with a respective reflective pixel electrode to have a specific value of said out-of-plane tilt; and

wherein

the voltage application circuitry is adapted to apply voltages to said two dimensional pixel array for two-dimensionally steering light incident upon said modulator.

38. A method of routing a light beam incident on an array of phase modulating elements, the light beam having a first component polarized in a first direction and a second component polarized in a second direction orthogonal to the first, the method comprising:

a) providing an integrated spatial light modulator comprising a liquid crystal layer, a wave plate layer having an optical retardance of (2n+1) λ

/4, a transparent conductive layer, and a reflector layer, the liquid crystal being responsive to a variation in a drive voltage to provide a variation in out-of-plane director angle tilt, the spatial light modulator having;

a two dimensional array of a plurality of pixels; and

an array of a plurality of reflective electrodes wherein each electrode is associated with a respective pixel of the integrated spatial light modulator and a respective portion of the liquid crystal layer to define a said phase modulating element whereby the spatial light modulator comprises a said array of phase modulating elements;

wherein the transparent conductive layer completely overlays said plurality of the reflective electrodes;

b) applying respective drive voltages to each said electrode whereby the portion of liquid crystal associated with the electrode has a respective specific value of director angle tilt;

c) applying said beam to the integrated spatial light modulator whereby the first and second components each pass through the liquid crystal layer and the wave plate layer, and are reflected at the reflector layer to again pass through the wave plate layer and liquid crystal layer to emerge with both components phase modulated by the same amount; and

d) controlling the drive voltages to vary a deflection direction of said light beam due to said array of phase modulating elements.

39. An optical switch comprising an integrated spatial light modulator for light of a predetermined wavelength, the integrated spatial light modulator comprising:

a transparent conductive layer,

a plurality of reflective pixel electrodes, said reflective pixel electrodes being disposed in a regular two-dimensional array;

a retardance layer having an optical retardance of an odd integer number of quarter-waves of said predetermined wavelength, the retardance layer being disposed on the regular two-dimensional pixel array; and

a liquid crystal layer being disposed between the retardance layer and the transparent conductive layer, wherein the transparent conductive layer completely overlays said plurality of the reflective electrodes.

40. The switch of claim 39, wherein said liquid crystal layer is a nematic crystal layer.

41. The switch of claim 40, wherein said liquid crystal layer is a π

-cell.