RESONANT PHOTO ACOUSTIC SYSTEM

• US 20130008229A1
• Filed: 06/15/2012
• Published: 01/10/2013
• Est. Priority Date: 07/07/2011
• Status: Abandoned Application

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Avramescu, Viorel, Gologanu, Mihai, Youngner, Daniel, Carlson, Bob Jon
• Application Number:
  US13/524,384
• Publication Number:
  US 20130008229A1
• Time in Patent Office: Days
• US Class Current: 73/24.02
• CPC Class Codes: G01N 21/1702 with opto-acoustic detection, e.g. for gases or analysing solids

Abstract

A device includes a resonator having an oscillating portion with dimensions chosen to lead to a desired resonant frequency. A light source is positioned to provide light along the length of the oscillating portion at a specific wave length. A detector detects a change in oscillation of the resonator responsive to the wave pressure produced by the light source heating a gas. The light source is modulated with a frequency the same as the resonant frequency of the resonator.

Claims

1. A device comprising:

a resonator having an oscillating portion;

a light source to provide light along a length of the oscillating portion; and

a detector to detect a change in oscillation of the resonator responsive to the light source heating a gas.

2. The device of claim 1 wherein the resonator comprises a micro electro-mechanical systems (MEMS) beam oscillator formed of silicon.

3. The device of claim 1 wherein the resonator comprises a micro electro-mechanical systems (MEMS) tuning fork oscillator.

4. The device of claim 3 and further comprising a further light source such that light is directed along outside lengths of two tines of the tuning fork oscillator.

5. The device of claim 1 wherein the resonator comprises a micro electro-mechanical systems (MEMS) T shaped oscillator and wherein the light is directed along a length of a top of the T shaped oscillator.

6. The device of claim 1 wherein the light source comprises an optical fiber to couple to a laser.

7. The device of claim 6 and further comprising a lens to focus light from the optical fiber to minimize dispersion of the light along the length of the resonator.

8. The device of claim 1 wherein the resonator is formed of silicon.

9. The device of claim 1 wherein the light is tuned to a resonant frequency of the resonator and to a selected absorption line of the gas to be detected.

10. A method comprising:

providing light adjacent to a length of a micro electromechanical systems (MEMS) resonant oscillator;

exposing a gas to be detected to the light to create a pressure wave; and

detecting oscillation of the oscillator responsive to the pressure wave.

11. The method of claim 10 wherein the light has a frequency corresponding to a resonant frequency of the resonant oscillator and to an absorption line of the gas to be detected.

12. The method of claim 11 wherein the light source comprises an optical fiber having a diameter similar to a height of the resonator.

13. The method of claim 12 wherein the light source further comprises a splitter coupled to the optical fiber and two additional optical fibers to receive light form the splitter and direct the light along a length outside of two tines of a resonant oscillator tuning fork.

14. The method of claim 10 and further comprising focusing the light along the length of the resonator such that the light does not significantly disperse.

15. The method of claim 10 wherein the resonator comprises a micro electro-mechanical systems (MEMS) beam oscillator formed of silicon.

16. The method of claim 10 wherein the resonator comprises a micro electromechanical systems (MEMS) T shaped oscillator and wherein the light is directed along a length of a top of the T shaped oscillator.

17. The method of claim 10 wherein the light source comprises an optical fiber to couple to a laser.

18. A sensor comprising:

a device wafer formed of silicon;

a microelectricalmechanical single crystal resonator released from the silicon on insulator device wafer and having an oscillating portion with dimensions chosen to lead to a desired resonant frequency

an optical fiber light source to provide light along the length of the oscillating portion in a cavity formed in the device wafer, the light having a frequency tuned to a resonant frequency of the resonator and to an absorption line of a gas to be detected;

a handle wafer supporting the device wafer and the optical fiber light source; and

a detector to detect a change in oscillation of the resonator responsive to the light source heating the gas.

19. The sensor of claim 18 wherein the detector comprises a piezoelectric layer supported by the resonator to provide a signal representative of deflection of the resonator due to pressure waves from the heated gas.

20. The sensor of claim 19 wherein the piezoelectric layer is spit into two portions along the length of the resonator and further comprising a pair of electrodes coupled to respective portions of the piezoelectric layer.