SENSOR DEVICE AND FOR DETERMINING A PHYSICAL VALUE

• US 20090141279A1
• Filed: 07/06/2005
• Published: 06/04/2009
• Est. Priority Date: 07/30/2004
• Status: Active Grant

• Current Assignee: University Kassel
• Original Assignee: University Kassel
• Inventors: Hillmer, Hartmut
• Granted Patent: US 8,120,775 B2
• Time in Patent Office: Days
• US Class Current: 356/436
• CPC Class Codes: G01N 21/39 using tunable lasers

Abstract

A sensor process and device are described for determining a physical value by means of a laser whose emission properties can be influenced by the physical value. The laser is designed to radiate at least two concurrent modes (E1, E2, E1′, E2′) above the laser threshold. The physical value is determined by comparing the influence of changes in the at least two modes resulting from the influence of the physical value (such as ΔI). The physical value can be, for example, a substance concentration, length, temperature, pressure or electric current.

Claims

1. A sensor device for determining a physical value, with a laser (1, 25, 37, 51, 61, 71, 80, 91, 102, 103) whose emission behaviour can be affected by the physical value, characterized in that the laser (1, 25, 37, 51, 61, 71, 80, 91, 102, 103) is arranged to emit at least two concurrent modes (E1, E2, E1′

, E2′

, E3, E4) lying above the laser threshold and the determination of the physical value is effected by a comparison between changes of the at least two modes (E1, E2, E1′

, E2′

, E3, E4) occurring under the influence of the physical value.

2. A sensor device according to claim 1, characterized in that the determination of the physical value is effected through a comparison between the intensities of the at least two modes (E1, E2, E1′

, E2′

, E3, E4).

3. A sensor device according to claim 1, characterized in that the comparison is effected by formation of a difference (Δ

I) between the spectral intensity maxima of the at least two modes (E1, E2, E1′

, E2′

, E3, E4).

4. A sensor device according to claim 2, characterized in that it comprises an optical detection system (6 to 10) for measuring a spectral intensity distribution of the radiation emitted from the laser (1, 25, 37, 51, 61, 71, 80, 91, 102, 103).

5. A sensor device according to claim 2, characterized in that it comprises a measuring device for receiving the relative intensity noise (RIN) of the laser (1, 25, 37, 51, 61, 71, 80, 91, 102, 103) for the determination of the intensities or intensity difference of the modes emitted by the laser (1, 25, 37, 51, 61, 71, 80, 91, 102, 103).

6. A sensor device according to claim 1, characterized in that the laser (1, 25, 37, 51, 61, 71, 80, 91, 102, 103) is a solid body laser.

7. A sensor device according to claim 1, characterized in that it is arranged to determine the optical absorption through a chemical substance having at least one optical absorption band (A) as a physical value.

8. A sensor device according to claim 7, characterized in that it comprises a receiving space (14, 28, 30, 34, 57b, 58a, 58b, 60, 64, 74, 84, 90, 94, 96 to 98, 109, 110) for a fluid within a resonator of the laser (1, 25, 37, 51, 61, 71, 80, 91, 102, 103).

9. A sensor device according to claim 1, characterized in that it includes a laser (1, 25, 37, 51, 61, 71, 80, 91, 102, 103) with a horizontal resonator.

10. A sensor device according to claim 9, characterized in that the receiving space (14, 28, 30, 34, 84, 89, 94) is formed as at least one interruption in an active laser material (4, 85).

11. A sensor device according to claim 9, characterized in that the resonator includes a resonator mirrors (87, 88, 92, 104) formed as photonic crystals.

12. A sensor device according to claim 11, characterized in that the receiving space (90, 94) includes hollow spaces remaining free between columns (89, 93) of the photonic crystals (87, 88, 92).

13. A sensor device according to claim 11, characterized in that the photonic crystals contain tubular holes (97, 98) forming the receiving space.

14. A sensor device according to claim 1, characterized in that it includes a laser (51) with a vertical resonator.

15. A sensor device according to claim 14, characterized in that the receiving space includes at least one hollow space (60) which is disposed between two resonator mirrors (53, 54) formed by DBR mirrors.

16. A sensor device according to claim 14, characterized in that at least one resonator mirror (53) includes a layer sequence of at least one solid body layer (58a, 59a) and at least one air layer (58b, 59b) forming a receiving space for a fluid.

17. A sensor device according to claim 7, characterized in that it is arranged to determine the absorption by a plurality of chemical substances, in that it includes a laser (1, 25, 37, 51, 61, 71, 80, 91, 102, 103) which is formed to emit a corresponding number of modes (E1, E2, E1′

, E2′

, E3, E4), of which each mode can be tuned to an absorption band (A) of one of the substances.

18. A sensor device according to claim 7, characterized in that it is arranged to determine the absorption of a plurality (k−

1) of chemical substances, in that it includes a laser (1, 25, 37, 51, 61, 71, 80, 91, 102, 103) which is arranged to emit a number (k) of modes (E1, E2, E1′

, E2′

, E3, E4) which is at least one greater than the plurality (k−

1) of the substances, wherein all other modes (k−

1) apart from a mode serving as a reference mode can be tuned simultaneously to an absorption band (A) of one each of the substances.

19. A method of determining a physical value using a laser (1, 25, 37, 51, 61, 71, 80, 91, 102, 103) by affecting its emission behaviour by means of the physical value, characterized in that the laser (1, 25, 37, 51, 61, 71, 80, 91, 102, 103) is so operated that it emits at least two concurrent modes (E1, E2, E1′

, E2′

, E3, E4) lying above the laser threshold, and in that the physical value is determined by comparison of those changes which result in relation to the at least two modes (E1, E2, E1′

, E2′

, E3, E4) under the influence of the physical value.

20. A method according to claim 19, characterized in that the at least two modes (E1, E2, E1′

, E2′

, E3, E4) are determined by and compared by optical spectroscopy.

21. A method according to claim 19, characterized in that the comparison is based on the optical intensities of the at least two modes (E1, E2, E1′

, E2′

, E3, E4).

22. A method according to claim 21, characterized in that the comparison is effected by formation of a difference (Δ

I) between the spectral intensity maxima of the at least two modes (E1, E2, E1′

, E2′

, E3, E4).

23. A method according to claim 21, characterized in that the intensities of the at least two modes (E1, E2, E1′

, E2′

, E3, E4) are determined by measuring the relative intensity noise (RIN) of the laser (1, 25, 37, 51, 61, 71, 80, 91, 102, 103).

24. A method according to, claim 19 characterized in that longitudinal and/or transverse electrical and/or magnetic modes are employed as modes (E1, E2, E1′

, E2′

, E3, E4).

25. A method according to any of claims 19 to 21claim 19, characterized in that the laser (1, 25, 37, 51, 61, 71, 80, 91, 102, 103) is operated with at least two modes (E1, E2, E1′

, E2′

, E3, E4) which have different polarisations.

26. A method according to claim 19, characterized in that calibration measurements are effected for quantitative determination of the physical value.

27. A method according to claim 19, characterized in that an optical absorption (A) by a chemical substance is determined as a physical value.

28. A method according to claim 19, characterized in that a length, a pressure, a magnetic or electric field, an electromagnetic radiation energy, a temperature, a heat energy, a radiation power or a value derived therefrom is determined as a physical value.

29. A method according to claim 27, characterized in that the laser (1, 25, 37, 51, 61, 71, 80, 91, 102, 103) is so operated that it radiates a plurality (k) of modes (E1, E2, E1′

, E2′

, E3, E4) and is so tuned that the plurality (k) of the modes (E1, E2, E1′

, E2′

, E3, E4) apart from one mode each matches spectrally an absorption band (A) of a smaller plurality (k−

1) of chemical substances and in that at least one mode which is associated with none of the substances is used as a reference mode.

30. A method according to claim 27, characterized in that the laser (1, 25, 37, 51, 61, 71, 80, 91, 102, 103) is so operated that a plurality (k) of modes (E1, E2, E1′

, E2′

, E3, E4) can be radiated and so tuned for determining the absorption which can be affected by different substances that each one of the modes spectrally matches an absorption band (A) of one of the substances.