Resonant Optothermoacoustic Detection of Optical Absorption

• US 20090174884A1
• Filed: 12/31/2008
• Published: 07/09/2009
• Est. Priority Date: 01/02/2008
• Status: Active Grant

• Current Assignee: Rice University
• Original Assignee: Rice University
• Inventors: BACHILO, Sergei M., KOSTEREV, Anatoliy A.
• Granted Patent: US 8,102,532 B2
• Time in Patent Office: Days
• US Class Current: 356/432
• CPC Class Codes: G01N 2021/1704 in gases
• CPC Class Codes: G01N 2021/1708 with piezotransducers probes for investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves G01N29/24
• CPC Class Codes: G01N 21/1702 with opto-acoustic detection, e.g. for gases or analysing solids
• CPC Class Codes: G01N 21/171 with calorimetric detection, e.g. with thermal lens detection
• CPC Class Codes: G01N 2201/0691 Modulated (not pulsed supply)
• CPC Class Codes: G01N 2291/014 Resonance or resonant frequency
• CPC Class Codes: G01N 2291/0427 Flexural waves, plate waves, e.g. Lamb waves, tuning fork, cantilever
• CPC Class Codes: G01N 29/2418 using optoacoustic interaction with the material, e.g. laser radiation, photoacoustics photoacoustic cells G01N21/1702; measuring characteristics of vibrations by using radiation-sensitive means G01H9/00; acousto-optical conversion techniques for short-range imaging G01S15/8965; sound-producing devices using laser bundle G10K15/046

Abstract

A device comprising an acoustic detector, one or more thermal sensing elements coupled to the acoustic detector, and a light source. A method comprising directing a beam of light at a wavelength at or near one or more thermal sensing elements, wherein the thermal sensing elements are coupled to an acoustic detector, determining a resonance frequency of the acoustic detector, wherein the acoustic detector is coupled to one or more of the thermal sensing elements, and measuring the response of the acoustic detector to detect optical radiation absorption proximate to or at the surface of one or more thermal sensing elements.

Claims

1. A device comprising:

an acoustic detector;

one or more thermal sensing elements coupled to the acoustic detector; and

a light source.

2. The device of claim 1, wherein the acoustic detector comprises a piezoelectric element.

3. The device of claim 1, wherein the acoustic detector comprises a quartz tuning fork.

4. The device of claim 1, wherein the acoustic sensor has an acoustic resonance, vibrational resonance, or combinations thereof.

5. The device of claim 1, wherein the one or more thermal sensing elements is integral to the acoustic detector.

6. The device of claim 1, wherein the light source is positioned such that a beam of light emitted from the light source passes through the acoustic detector.

7. The device of claim 6, wherein the light source is a modulated laser.

8. The device of claim 1, wherein the modulated laser has a frequency ranging from 100 Hz to about 50,000 Hz.

9. The device of claim 1, further comprising a cell enclosing the acoustic detector and the one or more thermal sensing elements.

10. The device of claim 1, wherein the one or more thermal sensing elements comprises a fiber, a transparent fiber, an optical fiber, a strip, or combinations thereof.

11. The device of claim 9, wherein the one or more thermal sensing elements is coupled to the cell.

12. The device of claim 3, comprising two thermal sensing elements, wherein the quartz tuning fork comprises at least two tines or prongs, and wherein each thermal sensing element is attached to a separate tine or prong of the acoustic detector.

13. A method comprising:

a) directing a beam of light at a wavelength at or near one or more thermal sensing elements, wherein the thermal sensing elements are coupled to an acoustic detector;

b) determining a resonance frequency of the acoustic detector, wherein the acoustic detector is coupled to one or more of the thermal sensing elements; and

c) measuring the response of the acoustic detector to detect optical radiation absorption proximate to or at the surface of one or more thermal sensing elements.

14. The method of claim 13, further comprising modulating the beam of light at a frequency, wherein the frequency is about equal to the resonance frequency of the acoustic detector or a sub-harmonic of the resonance frequency of the acoustic detector, wherein the sub-harmonic of the resonance frequency of the acoustic detector is the resonance frequency of the acoustic detector divided by in integer number.

15. The method of claim 13, wherein the acoustic detector comprises a piezoelectric element.

16. The method of claim 13, wherein the acoustic detector is a quartz tuning fork.

17. The method of claim 16, wherein two thermal sensing elements are coupled to the quartz tuning fork, wherein the quartz tuning fork comprises two or more prongs or tines, and wherein each of the two thermal sensing elements is coupled to a separate prong or tine of the quartz tuning fork.

18. The method of claim 13, wherein the wavelength of light is selected to effectuate optical radiation absorption proximate to or at the surface of the one or more thermal sensing elements.

19. The method of claim 13, wherein the optical radiation absorption occurs in, on, or about a fluid region and/or object.

20. The method of claim 18, wherein the wavelength of light selected is absorbed in, on, or about a fluid region and/or object absorbs light at the wavelength.