Optical device and methods

• US 10,257,594 B2
• Filed: 08/15/2013
• Issued: 04/09/2019
• Est. Priority Date: 08/15/2012
• Status: Active Grant

• Current Assignee: Thomas Swan & Company Limited (Aixtron AG)
• Original Assignee: Thomas Swan & Company Limited (Aixtron AG)
• Inventors: Holmes, Melanie, Janssen, Adrian Perrin
• Primary Examiner(s): Sedighian, Mohammad R
• Application Number:
  US14/421,694
• Publication Number:
  US 20150208144A1
• Time in Patent Office: 2,063 Days
• CPC Class Codes: H04J 14/02 Wavelength-division multiplex systems
• CPC Class Codes: H04J 14/0212 using optical switches or wavelength selective switches [WSS]
• CPC Class Codes: H04Q 11/0003 Details
• CPC Class Codes: H04Q 11/0005 Switch and router aspects
• CPC Class Codes: H04Q 2011/0009 using wavelength filters

Abstract

A device and method for controlling light by wavelength in a device with a switch plane and a dispersion plane uses optics providing an imaging function in the dispersion plane, and a Fourier transform function in the switch plane, so as to enable crosstalk to be reduced.

Claims

1. A switch device having a spatial light modulator, a dispersion device for spatially dispersing light onto the spatial light modulator, the switch device having a switch plane, a dispersion plane and optics, wherein the dispersion plane is defined as the plane across which light is dispersed by the dispersion device, wherein the switch plane is disposed orthogonal to the spatial light modulator and the dispersion plane and wherein the optics are configured to provide an imaging function in the dispersion plane, and a Fourier transform function in the switch plane, wherein the spatial light modulator has a first portion for spatially filtering light and a second portion for routing light.

2. A switch device according to claim 1, wherein the spatial light modulator comprises an LCOS SLM.

3. The switch device according to claim 1, wherein there is a single spatial light modulator, having a front electrode, wherein the front electrode is split to allow RMS voltages to be controlled independently for the first and second portions.

4. The switch device of claim 1, further having plural switch inputs, a switch output and input optics, each switch input being configured to receive plural input wavelength channels, the input optics configured to separate the input signals by wavelength and input port and direct the separated input signals to the first portion of the spatial light modulator, wherein the first portion of the spatial light modulator is configured to carry out wavelength-dependent spatial filtering to block at least some of the non-selected signals from each input and to output selected signals to the second portion of the spatial light modulator wherein the second portion of the spatial light modulator is configured to receive selected wavelengths from the first portion of the spatial light modulator and to route the selected wavelengths to the switch output.

5. The switch device of claim 1, having plural input ports, the device configured such that spatial filtering is carried out independently, per channel-port combination, whereby at least one of the non-selected signals in a wavelength channel in at least one input port is blocked by the first portion of the spatial light modulator.

6. The switch device of claim 1 wherein the spatial light modulator is reflective, the switch device further, having a focusing arrangement configured to spatially distribute light by wavelength in wavelength groups onto the reflective spatial light modulator, the switch device being configured so that reflected light from at least one of the wavelength groups passes through a device that has a focusing action in the dispersion plane to an optical device that acts as a retroreflector in the dispersion plane and a mirror in the switch plane.

7. The switch device of claim 1, having a single input port and plural output ports.

8. The switch device of claim 1, wherein the optics are configured to form a retroreflector configured to reflect light back along an incident path regardless of direction of incidence in the dispersion plane and to act as a mirror configured to reflect light with an angle of reflection equal to an angle of incidence with respect to a normal, in the switch plane.

9. The switch device of claim 8, configured such that light from the first portion of the spatial light modulator travels through one of a mirror and a lens to a reflecting device and returns via said one of a mirror and a lens to the second portion of the spatial light modulator to be imaged in the dispersion plane.

10. The switch device of claim 8, wherein the optics comprise a cylindrical lens disposed such that the optics act as a curved mirror in the switch plane and a retroreflector in the dispersion plane.

11. The switch device of claim 1, wherein the optics comprise a cylindrical lens and a retroreflector.

12. The switch device of claim 1, wherein the optics are configured to act as a tilted cylindrical mirror in the switch plane to pass light from the first portion to the second portion.

13. The switch device of claim 1, having a pair of refractive wedges in the beam path to pass beams from the first portion to the second portion.

14. The switch device of claim 1, wherein the optics comprise an equivalent Fourier element for performing the Fourier transform function, the Fourier element having a focal length substantially twice the focal length of the dispersion device.

15. The switch device of claim 1, wherein the optics comprise an equivalent Fourier element for performing the Fourier transform function, the Fourier element having a focal length more than twice the focal length of the dispersion device.

16. The switch device of claim 1 wherein the optics comprise an equivalent Fourier element for performing the Fourier transform function, the Fourier element having a focal length less than twice the focal length of the dispersion device.

17. The switch device of claim 1, wherein the first portion of the spatial light modulator is configured to provide relatively coarse attenuation of unwanted light and the second portion of the spatial light modulator is configured to provide a relatively fine attenuation of unwanted light.

18. The switch device of claim 1, wherein at least the first portion of the spatial light modulator is pixellated.

31. The method of claim 9, comprising assigning plural rows of the first portion of the spatial light modulator to a corresponding plurality of separated wavelength channels, wherein each row is a respective group or array of modulating elements of the first portion of the spatial light modulator and is assigned to a respective output port.

19. A method of controlling light using a spatial light modulator device, the spatial light modulator device having a first portion acting as a spatial filter and a second portion acting as a routing device in a switch having a dispersion plane for spatially dispersing light and a switching plane, wherein the switching plane is disposed orthogonal to the dispersion plane, the method comprising performing an imaging function in the dispersion plane and performing a Fourier transform function in the switching plane.

20. The method of claim 19, wherein the spatial light modulator device comprises a single spatial light modulator comprising said first and second portions.

21. The method of claim 19 further comprising spatially filtering light by the first portion to block unwanted light thereby to reduce crosstalk.

22. The method of claim 21 further comprising spatially filtering light at the first portion to block unwanted orders that cause transient crosstalk when switching holograms on or off.

23. The method of claim 21 further comprising spatially filtering light at the first portion to suppress wavelength-dependent adjacent port crosstalk.

24. The method of claim 21 further comprising spatially filtering light at the first portion to suppress crosstalk spikes created at hologram boundaries.

25. The method of claim 21 further comprising spatially filtering light at the first portion to reduce crosstalk from spacers used to control a cell gap in the spatial light modulator.

26. The method of claim 21 further comprising spatially filtering light at the first portion to reduce sensitivity to temperature.

27. The method of claim 21 further comprising spatially filtering light at the first portion to block unwanted diffraction orders.

28. The method of claim 21 further comprising spatially filtering light at the first portion to allow the use of symmetric orders.

29. The method of claim 19, comprising using at least one of the first and second portions to provide attenuation of light.

30. The method of claim 19, comprising assigning plural rows of the first portion of the spatial light modulator to a corresponding plurality of separated wavelength channels, wherein each row is a respective group or array of modulating elements of the first portion of the spatial light modulator and is assigned to a respective input port.

32. A switch device having a spatial light modulator, a dispersion device for spatially dispersing light onto the spatial light modulator, the switch device having a switch plane, a dispersion plane and optics, wherein the dispersion plane is defined as the plane across which light is dispersed by the dispersion device, wherein the switch plane is disposed orthogonal to the spatial light modulator and the dispersion plane and wherein the optics are configured to provide an imaging function in the dispersion plane, and a Fourier transform function in the switch plane, wherein the spatial light modulator has a portion for spatially filtering light and a portion for routing light, the switch further having a single switch input, plural switch outputs and input optics, the single input being configured to receive plural input wavelengths, the input optics to separate the input wavelengths and direct the separated input wavelengths to the portion for routing light, wherein the portion for routing light is configured to receive selected wavelengths from the single input and to route the selected wavelengths via the optics to the portion for spatially filtering light, the portion for spatially filtering light being configured to block independently, for each wavelength channel or signal band, separated diffraction orders from a routing hologram of the portion for routing light that are not required to propagate to one or more of the switch outputs and to pass selected signals to desired switch outputs.

33. A switch device having plural spatial light modulators, a switch input, a switch output and a dispersion device for spatially dispersing light from the switch input onto a first spatial light modulator, wherein the switch device has a switch plane, a dispersion plane and optics, wherein the dispersion plane is defined as the plane across which light is dispersed by the dispersion device, wherein the switch plane is disposed orthogonal to the spatial light modulators and the dispersion plane and wherein the optics are configured to provide an imaging function in the dispersion plane and a Fourier transform function in the switch plane, wherein a first spatial light modulator is configured to spatially filter light for selectively blocking at least one signal of at least one wavelength of the light and a second spatial light modulator is configured for selectively routing light, to a switch output.

34. A switch device having plural spatial light modulators, a switch input, and a dispersion device for spatially dispersing light from the switch input onto a first spatial light modulator, the switch device having a switch plane, a dispersion plane and optics, wherein the dispersion plane is defined as the plane across which light is dispersed by the dispersion device, wherein the switch plane is disposed orthogonal to the spatial light modulator and the dispersion plane and wherein the optics are configured to provide an imaging function in the dispersion plane, and a Fourier transform function in the switch plane, wherein the first spatial light modulator is for spatially filtering light and a second spatial light modulator is for routing light, the switch having a single switch input, plural switch outputs and input optics, the single input being configured to receive plural input wavelengths, the input optics to separate the input wavelengths and direct the separated input wavelengths to the portion for routing light, wherein the second spatial light modulator light is configured to receive selected wavelengths from the single input and to route the selected wavelengths via the optics to the first spatial light modulator for spatially filtering light, the first spatial light modulator for spatially filtering light being configured to block independently, for each wavelength channel or signal band, separated diffraction orders from a routing hologram of the second spatial light modulator for routing light that are not required to propagate to one or more of the switch outputs and to pass selected signals to desired switch outputs.