Optical switch including two integrated multiphase SLM's and a wave-plate the wave-plate providing an optical retardance of (2n+1)λ/4

• US 6,954,252 B1
• Filed: 10/04/2000
• Issued: 10/11/2005
• Est. Priority Date: 10/04/1999
• Status: Expired due to Fees

• Current Assignee: Thomas Swan & Company Limited (Aixtron AG)
• Original Assignee: Thomas Swan & Company Limited (Aixtron AG)
• Inventors: Robertson, Brian, Crossland, William, Wilkinson, Timothy, Holmes, Melanie, Redmond, Maura, Manolis, Ilias
• Primary Examiner(s): CHOWDHURY, TARIFUR RASHID
• Application Number:
  US10/089,929
• Time in Patent Office: 1,833 Days
• Field of Search: 349/193, 349/196, 349/197, 349/201, 359/10, 359/245, 359/237, 359/279, 359/295, 359/316
• 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]
• 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 polarization 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. A routing switch comprising a first and a second integrated multiphase spatial light modulator for spatial phase modulation of unpolarized light of a predetermined wavelength, the integrated spatial light modulators having a substantially planar liquid crystal layer, a layer reflective of said light of said wavelength and a wave-plate layer, the wave-plate layer providing an optical retardance of (2n+1)λ

/4, said liquid crystal layer having two opposed faces and being disposed and configured to provide an out of plane tilt in response to a voltage applied between said faces, and said liquid crystal layer being spaced from the reflective layer by the said wave-plate layer, wherein the integrated spatial light modulators comprise an integrated array of phase modulating elements and voltage application circuitry, the 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;

wherein the integrated multiphase spatial light modulators comprise an array of electrodes, each of the electrodes being associated with a respective portion of the liquid crystal layer to define a said phase modulating element, the electrodes being such that application of voltage to each electrode causes the portion of the liquid crystal layer associated with the said 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 array of electrodes for varying a deflection angle of light and the second integrated spatial light modulator is disposed with respect to the first integrated spatial light modulator for receiving light from said first integrated spatial light modulator thereby to route said light, the device further comprising;

a first array of optical fibers forming light sources directed to be off-normally incident on the first integrated spatial light modulator and a second array of optical fibers forming light receivers directed to be off-normally incident on the second integrated spatial light modulator for receiving light from the second integrated spatial light modulator; and

drive circuitry for forming a respective plurality of switching holograms on each integrated spatial light modulator, each said switching hologram on said first integrated spatial light modulator in use being operative to deflect light incident on said first integrated spatial light modulator to said switching holograms on said second integrated spatial light modulator, and each said switching hologram on said second integrated spatial light modulator in use being operative to deflect said light beams to a respective optical receiver.

2. The routing switch of claim 1, wherein the switching holograms are spaced apart on said first and second integrated spatial light modulators and the first and second integrated spatial light modulators are disposed such that a respective zero-order beam reflected from each switching hologram on said first integrated spatial light modulator is incident on a spacing between two adjacent switching holograms on said second integrated spatial light modulator.

3. The routing switch of claim 1, wherein a half wave plate is disposed between said first and second integrated spatial light modulators.

4. The routing switch of claim 1, wherein the first and second spatial light modulators are mutually offset so no zero-order beams from the first spatial light modulator are incident on the second spatial light modulator.

5. The routing switch of claim 1, wherein the switching holograms are spaced apart on said first and second spatial light modulators, and the first and second spatial light modulators are disposed such that a respective second-order beam from each switching hologram on said first spatial light modulator is incident on a space between two adjacent switching holograms on said second spatial light modulator.