Raman spectroscopy with stabilized multi-mode lasers

• US 20060176478A1
• Filed: 02/09/2005
• Published: 08/10/2006
• Est. Priority Date: 02/09/2005
• Status: Abandoned Application

• Current Assignee: Raman Systems, Inc.
• Original Assignee: Raman Systems, Inc.
• Inventors: Clarke, Richard H., Womble, M. Edward
• Application Number:
  US11/054,379
• Publication Number:
  US 20060176478A1
• Time in Patent Office: Days
• US Class Current: 356/301
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0218 using optical fibers
• CPC Class Codes: G01J 3/0227 using notch filters
• CPC Class Codes: G01J 3/10 Arrangements of light sources specially adapted for spectrometry or colorimetry
• CPC Class Codes: G01J 3/44 Raman spectrometry; Scattering spectrometry ; Fluorescence spectrometry
• CPC Class Codes: G01N 2021/651 Cuvettes therefore
• CPC Class Codes: G01N 2021/656 Raman microprobe
• CPC Class Codes: G01N 2021/8528 Immerged light conductor
• CPC Class Codes: G01N 21/65 Raman scattering
• CPC Class Codes: G01N 2201/08 Optical fibres; light guides

Abstract

Methods and apparatus for analysis of a sample using Raman spectroscopy, which employs a multi-mode radiation source and a spectral filter, are disclosed. The source radiation produces a Raman spectrum consisting of scattered electromagnetic radiation that is separated into different wavelength components by a dispersion element. A detection array detects a least some of the wavelength components of the scattered light and provides data to a processor for processing the data. The resulting spectroscopic data has higher resolution and stability than conventional low-resolution Raman systems.

Claims

1. A Raman spectroscopy apparatus for measuring a property of a sample, the apparatus comprising:

a multi-mode laser for irradiating a sample to produce a Raman spectrum,

a grating positioned to receive and filter radiation from the multi-mode laser;

a dispersion element positioned to receive and separate scattered radiation into different wavelength components,

a detection array, optically aligned with the dispersion element for detecting at least some of the wavelength components of the scattered light, and

a processor for processing data from the detector array to measure a property of the sample,

wherein the apparatus provides a Raman spectrometer having a resolution of less than about 10 cm<sup>−

1</sup>.

2. The apparatus of claim 1, wherein the apparatus further comprises an excitation fiber for transmitting the laser radiation from the grating to the sample, the excitation fiber having a first end coupled to the grating and a second end positioned for interaction with the sample.

3. The apparatus of claim 2, wherein the apparatus further comprises a sample chamber adapted to receive a sample.

4. The apparatus of claim 1, wherein the grating is a volume phase Bragg grating.

5. The apparatus of claim 1, wherein the multi-mode laser produces laser radiation having a wavelength between about 700 nm and about 1 μ

m.

6. The apparatus of claim 1, wherein the multi-mode laser comprises a 785 nm GaAs laser diode.

7. The apparatus of claim 1, wherein the multi-mode laser has a full width at half maximum of at least about 2 nm without the volume phase grating.

8. The apparatus of claim 1, wherein the multi-mode laser has a power between about 50 mw and about 1000 mw.

9. The apparatus of claim 1, wherein the processor includes a chemometric means for applying partial least square analysis for extracting information from the Raman spectrum.

10. The apparatus of claim 1, wherein the detection array comprises a diode array detector.

11. The apparatus of claim 1, wherein the detection array comprises a charged coupled device detector.

12. The apparatus of claim 1, wherein the apparatus further comprises a collection fiber for collecting light scattered from a sample.

13. The apparatus of claim 1, wherein said apparatus has a resolution of between about 4 cm⁻

1 and 10 cm<sup>−

1</sup>, the resolution of the apparatus being determined in part by the volume phase grating and, in part, by the dispersion element.

14. A method for measuring a property of a sample using low resolution Raman spectroscopy comprising:

providing a sample;

producing radiation using a multi-mode laser;

passing the produced radiation through a grating that reduces mode-hopping effects and increase stability;

irradiating the sample to produce a Raman spectrum consisting of scattered electromagnetic radiation;

receiving and separating the scattered radiation into different wavelength components using a dispersion element;

detecting at least some of the wavelength components of the scattered light using a detection array; and

processing data from the detector array and calculating information about the sample with a processor.