Tunable laser fluid sensor

• US 7,145,165 B2
• Filed: 09/28/2004
• Issued: 12/05/2006
• Est. Priority Date: 09/12/2001
• Status: Expired due to Term

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Cole, Barrett E., Cox, James A.
• Primary Examiner(s): Luu, Thanh X.
• Assistant Examiner(s): Yam, Stephen
• Application Number:
  US10/953,174
• Publication Number:
  US 20050040337A1
• Time in Patent Office: 798 Days
• Field of Search: 250/343, 250/573, 250/574, 250/226, 356/436, 356/437, 356/438, 356/439, 356/441, 356/442
• US Class Current: 250/573
• CPC Class Codes: G01N 2021/391 Intracavity sample
• CPC Class Codes: G01N 2021/399 Diode laser
• CPC Class Codes: G01N 21/05 Flow-through cuvettes G01N21/09 takes precedence; handling fluid samples G01N1/10
• CPC Class Codes: G01N 21/35 using infrared light G01N21/39 takes precedence
• CPC Class Codes: G01N 21/3504 for analysing gases, e.g. multi-gas analysis
• CPC Class Codes: G01N 21/3577 for analysing liquids, e.g. polluted water
• CPC Class Codes: G01N 21/39 using tunable lasers
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26
• CPC Class Codes: G02F 1/0147 based on thermo-optic effects G02F1/132 takes precedence
• CPC Class Codes: G02F 1/015 based on semiconductor elements having potential barriers, e.g. having a PN or PIN junction G02F1/03 takes precedence
• CPC Class Codes: G02F 1/21 by interference
• CPC Class Codes: G02F 1/213 Fabry-Perot type
• CPC Class Codes: G02F 2203/055 wavelength filtering

Abstract

A sensitive fluid sensor for detecting fluids and particularly trace fluids. The sensor may be adjustable for detecting fluids of various absorption lines. To effect such adjustment, a tunable laser may be used. The laser may be an edge emitting diode, a VCSEL or other tunable source. The detection apparatus of the sensor may incorporate a sample cell through which a laser light may go through. The sample cell may comprise a tunable ring-down cavity. The ring-down cavity may be a ring laser cavity like that of a ring laser gyroscope. There may be a photo detector proximate to the ring down cavity connected to a processor.

Claims

1. A fluid sensor comprising:

a tunable light source;

a cavity positioned to receive light from the tunable light source; and

a detector positioned to receive light from the cavity; and

wherein;

the tunable light source is an edge emitting diode; and

the edge emitting diode comprises;

a substrate;

a layer, having a laser cavity with reflective surfaces situated at the edges of the laser cavity, situated on the substrate; and

a moveable mirror proximate to one edge for tuning the laser cavity.

2. The sensor of claim 1, wherein the moveable mirror may be adjusted to tune the laser cavity to a particular wavelength.

3. A fluid sensor comprising:

a tunable light source;

a ring down cavity positioned to receive light from the tunable light source; and

a detector positioned to receive light from the ring down cavity; and

wherein;

the tunable light source is a VCSEL; and

the VCSEL comprises;

a substrate;

a first mirror situated on the substrate;

an active area situated on the first mirror; and

a second mirror situated at a variable distance from the first mirror.

4. The sensor of claim 3, wherein the variable distance may be adjusted to tune the VCSEL to a particular wavelength.

5. The sensor of claim 4, wherein the wavelength may be adjusted to determine the kind of fluid in the ring down cavity.

6. The sensor of claim 3, wherein the VCSEL further comprises:

a current spreading layer on the active region; and

an adjustable gap between the second mirror and the current spreading layer.

7. The sensor of claim 6, wherein the VCSEL further comprises:

a first spacer situated between the first mirror and the active region; and

a second spacer situated between the active region and the current spreading layer.

8. The sensor of claim 7, wherein the VCSEL further comprises a current confinement region situated at least partially in the current spreading layer.

9. The sensor of claim 8, wherein the VCSEL has an infrared bandwidth.

10. A fluid sensor comprising:

a tunable light source;

a ring down cavity positioned to receive light from the tunable light source; and

a detector positioned to receive light from the ring down cavity; and

wherein;

the ring down cavity comprises;

a containing structure;

a first mirror positioned in the containing structure to receive light from the tunable light source; and

at least another mirror positioned in the containing structure to receive light reflected by the first mirror arid reflect it back to the first mirror and vice versa for a plurality of times;

the at least another mirror is moveable to adjust the wavelength of the containing structure;

the light source is tuned to an absorption line of a fluid in the containing structure;

the detector is proximate to the at least another mirror to detect light reflected in the containing structure;

the ring down cavity is a ring laser cavity;

the containing structure is tuned to an absorption line of the fluid in the containing structure; and

the tunable light source is an edge emitting diode.

11. The sensor of claim 10, wherein the edge emitting diode comprises:

a substrate;

a layer, having a laser cavity with reflective surfaces situated at the edges of the cavity, situated on the substrate; and

a moveable mirror proximate to one edge for tuning the laser cavity.

12. The sensor of claim 11, wherein the moveable mirror may be adjusted to tune the laser cavity to a particular wavelength.

13. The sensor of claim 12, wherein the wavelength may be adjusted to determine the kind of fluid in the containing structure.