Optical modulator/switch including reflective zone plate and related method of use

• US 5,684,631 A
• Filed: 05/13/1996
• Issued: 11/04/1997
• Est. Priority Date: 05/13/1996
• Status: Expired due to Term

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Greywall, Dennis S.
• Primary Examiner(s): Henry, Jon W.
• Application Number:
  US08/645,109
• Time in Patent Office: 540 Days
• Field of Search: 359/565, 359/572, 359/569, 359/15, 359/19, 359/128, 359/157, 359/173, 385/15, 385/16, 385/18, 385/33, 385/34
• US Class Current: 359/565
• CPC Class Codes: G02B 26/0808 by means of one or more diffracting elements

Abstract

An optical modulator/optical switch is disclosed. The modulator/switch includes a reflective zone plate defined in a movable zone plate support. The reflective zone plate focuses an optical signal reflected therefrom. In response to a control signal, a controlled voltage source applies a voltage across the movable zone plate support and a layer spaced from the zone plate support. The applied voltage generates an electrostatic force that causes the zone plate support to move towards the other layer. When the zone plate support moves, the reflective zone plate'"'"'s orientation to an optical signal incident thereon changes. Such a change in orientation alters the path of the optical signal reflected from the reflective zone plate. The reflected optical signal can be directed to different receiving waveguides by changing the amplitude of the applied voltage.

Claims

1. An optical modulator/switch comprising:

a reflective zone plate for receiving an incident optical signal and returning a reflected optical signal that is focused at a location a predetermined distance from the reflective zone plate, the reflective zone plate having a first and a second state and defined by (i) a central circular region enclosed by a first plurality of spaced, concentrically-disposed annular-shaped regions, both the circular and annular regions being of a first type and (ii) a second plurality of regions of a second type located between the spaced annular-shaped regions of the first type, the reflective zone plate having one of either a first or a second configuration;

a zone-plate support, in which or on which the reflective zone plate is defined, the zone-plate support physically configured so that it moves in response to a force, changing state from or to the first state, to or from the second state;

a conductive layer spaced from the zone-plate support; and

a controlled voltage source electrically connected to the zone-plate support and the layer;

wherein,

in the first configuration, regions of the first type prevent negative contributions to the amplitude of the reflected optical signal from reaching the focal location and regions of the second type reflect positive contributions to the amplitude of the reflected optical signal to the focal location, and, in the second configuration, regions of the first type reflect positive contributions to the amplitude of the reflected signal to the focal location and regions of the second type prevent negative contributions to the amplitude of the reflected signal from reaching the focal location.

2. The optical modulator/switch of claim 1 wherein, in the first orientation, the reflective zone plate is perpendicular to the the incident optical signal.

3. The optical modulator/switch of claim 1 further comprising a first waveguide, wherein, the first waveguide delivers the incident signal to the reflective zone plate and, in the first state, the first waveguide is in optical communication with the reflected signal, and, in the second state, the first waveguide is not in optical communication with the reflected signal.

4. The optical modulator/switch of claim 1 further comprising a first and a second waveguide, wherein, the first waveguide delivers the incident optical signal to the reflective zone plate and, in the first state, the second waveguide is in optical communication with the reflected optical signal, and, in the second state, the second waveguide is not in optical communication with the reflected optical signal.

5. The optical modulator/switch of claim 1 further comprising a first, a second and a third waveguide, wherein, the first waveguide delivers the incident signal to the reflective zone plate, and, in the first state, the second waveguide is in optical communication with the reflected signal, and, in the second state, the third waveguide is in optical communication with the reflected signal.

6. The optical modulator/switch of claim 1 wherein the distance between the reflective zone plate and the focal location is in the range from about 100 to about 500 times the wavelength of the incident optical signal.

7. The optical modulator/switch of claim 1 wherein the regions that prevent negative contributions to the amplitude of the reflected signal from reaching the focal location do not reflect negative contributions.

8. The optical modulator/switch of claim 1 wherein the regions that prevent negative contributions to the amplitude of the reflected signal from reaching the focal location change the phase of the reflected optical signal by about 180°

.

9. The optical modulator/switch of claim 1 further comprising a waveguide having a first end positioned at the focal location.

10. The optical modulator/switch of claim 1 wherein the zone-plate support is flexible and has a doubly-supported beam configuration.

11. The optical modulator/switch of claim 10 further comprising a waveguide having a first end positioned at the focal location.

12. The optical modulator/switch of claim 1 wherein the zone-plate support has a cantilever configuration.

13. The optical modulator/switch of claim 12 further comprising a waveguide having a first end positioned at the focal location.

14. The optical modulator/switch of claim 1 wherein the zone-plate support has a torsional configuration.

15. The optical modulator/switch of claim 14 further comprising a waveguide having a first end positioned at the focal location.

16. The optical modulator/switch of claim 1 wherein each region of the first and second plurality of regions are further comprised of sections, each section within a region differing in height from an adjacent section in the region by the same amount.

17. A method for modulating an optical signal, comprising the steps of:

generating an electrostatic force according to a control signal, the electrostatic force causing a reflective zone plate to change between a first and a second orientation relative to the optical signal; and

reflecting the optical signal off of the reflective zone plate, wherein,

the change in orientation of the reflective zone plate causes a change in a path of the optical signal reflected from the reflective zone plate so that in the first orientation, the optical signal is reflected to a predetermined location, and, in the second orientation, the optical signal is not reflected to the predetermined location, the controlled change in optical path resulting in modulation of the optical signal.

18. A method for switching an optical signal, comprising the steps of:

generating an electrostatic force in response to a control signal causing a reflective zone plate to move between a first first orientation and a second orientation relative to the optical signal; and

reflecting the optical signal off of the reflective zone plate to a first waveguide when the reflective zone plate is in the first orientation and to a second waveguide when the reflective zone plate is in the second orientation.

19. The method of claim 18 and further wherein the step of moving results in a third orientation of the reflective zone plate and the step of reflecting further comprises reflecting the optical signal off the reflective zone plate to a third waveguide when the reflective zone plate is in the third orientation.