Optomechanical radiant energy detector

• US 6,392,233 B1
• Filed: 08/10/2000
• Issued: 05/21/2002
• Est. Priority Date: 08/10/2000
• Status: Expired due to Fees

• Current Assignee: Sarnoff Corporation (SRI International, Inc.)
• Original Assignee: Sarnoff Corporation (SRI International, Inc.)
• Inventors: Amantea, Robert, Michael, Robert Raymond, Channin, Donald Jones, Pantuso, Francis Paul
• Primary Examiner(s): Sugarman, Scott J.
• Assistant Examiner(s): HANIG, RICHARD E
• Application Number:
  US09/635,552
• Time in Patent Office: 649 Days
• Field of Search: 250/338.1, 250/338.4, 250/332, 250/334, 250/306
• US Class Current: 250/338.1
• CPC Class Codes: G01J 5/40 using bimaterial elements
• CPC Class Codes: H01G 5/16 using variation of distance between electrodes
• CPC Class Codes: H01G 5/40 Structural combinations of variable capacitors with other electric elements not covered by this subclass, the structure mainly consisting of a capacitor, e.g. RC combinations

Abstract

A MicroOptoElectroMechanical (MOEM) IR detector utilizes a novel combination of integrated MEMS and photonics to achieve high responsivity with low noise. Increasing incident radiant energy bends a bimaterial arm that moves a coupling waveguide into the evanescent field of a principal optical waveguide. This, in turn, modulates the light in the principal waveguide. This device has high detection sensitivity to incident radiation due to the combination of the length of the lever arm and the sensitivity of the evanescent field. The device exhibits low noise because photons are being modulated instead of electrons.

Claims

1. An optomechanical radiant energy detector comprising:

a substrate;

a radiant energy absorber;

an anchor mechanically coupled to the substrate;

an isolation arm mechanically coupled to the anchor and the radiant energy absorber;

a first waveguide having a first waveguide evanescent field, mechanically coupled to the substrate;

a second waveguide having a second waveguide evanescent field, said second waveguide being positioned in proximity to the first waveguide, and

an actuator mechanically coupled to the second waveguide, the radiant energy absorber and the isolation arm, wherein the actuator is responsive to incident energy on the radiant energy absorber to move the second waveguide to a position at which the first and second waveguide evanescent fields interact.

2. An optomechanical radiant energy detector in accordance with claim 1, wherein the first waveguide and the second waveguide comprise hydrogenated amorphous SiC.

3. An optomechanical radiant energy detector in accordance with claim 1, wherein the substrate comprises a material selected from one of SiO₂ and Al₂O₃.

4. An optomechanical radiant energy detector in accordance with claim 1, further comprising an absorber mirror for reflecting radiant energy onto the radiant energy absorber.

5. An optomechanical radiant energy detector in accordance with claim 4, wherein the radiant energy absorber comprises SiC and TiW and the absorber mirror comprises Al.

6. An optomechanical radiant energy detector in accordance with claim 4, wherein the TiW has a sheet resistance between 300 ohms/square and 400 ohms/square.

7. An optomechanical radiant energy detector comprising:

a substrate;

a radiant energy absorber for converting incident energy into thermal energy;

an anchor mechanically coupled to the substrate;

an isolation arm mechanically coupled to the anchor and the radiant energy absorber for providing thermal resistance between the radiant energy absorber and the substrate and for providing mechanical support for the absorber;

a first waveguide having a first waveguide evanescent field, mechanically coupled to the substrate;

a second waveguide having a second waveguide evanescent field, mechanically coupled to the actuator and positioned in proximity to the first waveguide, and

an actuator mechanically coupled to the second waveguide, the radiant energy absorber and the isolation arm, wherein the actuator is responsive to incident energy on the radiant energy absorber to move the second waveguide to a position at which the first and second waveguide evanescent fields interact.

8. An optomechanical radiant energy detector in accordance with claim 7, wherein the first waveguide and the second waveguide comprise hydrogenated amorphous SiC.

9. An optomechanical radiant energy detector in accordance with claim 7, wherein the substrate comprises a material selected from one of SiO₂ and Al₂O₃.

10. An optomechanical radiant energy detector in accordance with claim 7, wherein the radiant energy absorber comprises SiC and TiW.

11. An optomechanical radiant energy detector in accordance with claim 9, wherein the TiW has a sheet resistance between 300 ohms/square and 400 ohms/square.

12. A method for fabricating an optomechanical radiant energy detector having a substrate, a first waveguide region, and a cantilever arm including a second waveguide region, an anchor region, an actuator and an absorber, said method comprising the steps of:

forming said first waveguide region and said anchor region on said substrate;

depositing a sacrificial layer onto said first waveguide region and said anchor region;

defining an anchor opening within said sacrificial layer;

contiguously depositing an amorphous material, an absorber metal, and a bimaterial metal, onto said sacrificial layer and said anchor opening;

defining and etching said bimaterial metal, said absorber metal, and said amorphous material, to form said actuator, said absorber, and said second waveguide, respectively; and

etching said sacrificial layer to form the cantilever arm.

13. A method for fabricating an optomechanical radiant energy detector having a substrate, an absorber mirror, a first waveguide region, and a cantilever arm including a second waveguide region, an anchor region, an actuator and an absorber, said method comprising the steps of:

defining and etching a recess region into said substrate;

forming an absorber mirror within said recess region;

sputtering a passivation coating onto said absorber mirror;

forming said first waveguide region and said anchor region on said substrate;

depositing a sacrificial layer onto said passivation coating, said first waveguide region, and said anchor region;

defining an anchor opening within said sacrificial layer;

contiguously depositing an amorphous material, an absorber metal, and a bimaterial metal, onto said sacrificial layer and said anchor opening;

defining and etching said bimaterial metal, said absorber metal, and said amorphous material, to form said actuator, said absorber, and said second waveguide, respectively; and

etching said sacrificial layer to form the cantilever arm.

14. The method in accordance with claim 13, wherein said absorber mirror comprises Al.

15. The method in accordance with claim 13, wherein said passivation coating comprises Al₂O₃.

16. The method in accordance with claim 13, wherein said amorphous material comprises SiC.