Probe for tunable laser Raman spectroscopy system

• US 20070195320A1
• Filed: 02/17/2006
• Published: 08/23/2007
• Est. Priority Date: 02/17/2006
• Status: Active Grant

• Current Assignee: Excelitas Technologies Corporation (Excelitas Technologies Holdings LLC)
• Original Assignee: Axsun Technologies Incorporated
• Inventors: Zambuto, James, Coppeta, David, Sriram, Tirunelveli
• Granted Patent: US 7,773,217 B2
• Time in Patent Office: Days
• US Class Current: 356/301
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0224 using polarising or depolarising elements
• CPC Class Codes: G01J 3/0291 Housings; Spectrometer accessories; Spatial arrangement of elements, e.g. folded path arrangements
• CPC Class Codes: G01J 3/10 Arrangements of light sources specially adapted for spectrometry or colorimetry
• CPC Class Codes: G01J 3/26 using multiple reflection, e.g. Fabry-Perot interferometer, variable interference filters
• CPC Class Codes: G01J 3/28 Investigating the spectrum using colour filters G01J3/51
• CPC Class Codes: G01J 3/44 Raman spectrometry; Scattering spectrometry ; Fluorescence spectrometry
• CPC Class Codes: G01N 21/65 Raman scattering

Abstract

A probe of a Raman spectroscopy system has a wavelength and/or amplitude referencing system for determining a wavelength of the excitation signal. Preferably, this referencing system is near an output aperture, through which the excitation signal is transmitted to the sample. In this way, any birefringence or polarization dependent loss (PDL) that may be introduced by optical elements in the system can be compensated for since the wavelength reference system will detect the effect or impact of these elements.

Claims

1. A probe subsystem for a Raman spectroscopy system, the probe subsystem comprising:

a wavelength reference system for determining a wavelength of an excitation signal; and

an output aperture through which the excitation signal is transmitted to a sample.

2. A probe subsystem as claimed in claim 1, wherein the wavelength reference system comprises:

at least one reference detector; and

a wavelength reference element for filtering the excitation signal received by the wavelength reference detector.

3. A probe subsystem as claimed in claim 1, wherein the wavelength reference system comprises:

a first reference detector;

a second reference detector;

a partial reflector for dividing the excitation between the first reference detector and the second reference detector; and

a wavelength reference element for filtering the excitation signal received by the first reference detector and the second reference detector.

4. A probe subsystem as claimed in claim 3, further comprising a controller that uses the responses of the first reference detector and the second reference detector to determine the wavelength and a power of the excitation signal.

5. A probe subsystem as claimed in claim 1, further comprising a partially reflective mirror in a path of the excitation signal for tapping the portion of the excitation signal received by the wavelength reference system.

6. A probe subsystem as claimed in claim 1, further comprising excitation optics for shaping a beam of the excitation signal after detection of the portion of the excitation signal by the wavelength reference system.

7. A probe subsystem as claimed in claim 1, further comprising separation optics for enabling transmission of the excitation beam to the sample and receipt of a spectroscopic response from the sample along a common axis and through a common aperture.

8. A probe subsystem as claimed in claim 1, wherein the separation optics comprises a mirror for reflecting light from the sample, the mirror comprising an optical port through which the excitation signal is transmitted to the sample.

9. A probe subsystem as claimed in claim 1, wherein the probe subsystem receives the excitation signal from a semiconductor tunable laser subsystem through an optical fiber.

10. A probe subsystem as claimed in claim 9, further comprising at least one amplified spontaneous emission filter for attenuating amplified spontaneous emission in the excitation signal after receipt from the optical fiber.

11. A probe subsystem as claimed in claim 9, further comprising at least one polarizer for improving a polarization of the excitation signal after receipt from the optical fiber.

12. A probe subsystem as claimed in claim 1, further comprising at least one polarizer for improving a polarization of the excitation signal.

13. A probe subsystem as claimed in claim 1, wherein the probe subsystem receives the excitation signal from a semiconductor tunable laser subsystem through a polarization maintaining optical fiber.

14. A probe subsystem for a Raman spectroscopy system in which an excitation signal is generated by a semiconductor tunable laser, the probe subsystem comprising:

a wavelength reference detector for detecting a portion of the excitation signal that is generated by the semiconductor tunable laser to determine a wavelength of the excitation signal; and

an output aperture through which the excitation signal is transmitted to a sample.

15. A Raman spectroscopy system, comprising:

a tunable laser excitation subsystem comprising at least one tunable semiconductor diode for generating an excitation signal;

a probe subsystem comprising;

a wavelength reference system for determining a wavelength of the excitation signal, and

an output aperture through which the excitation signal is transmitted to a sample; and

a spectrometer subsystem for resolving a spectrum of light returning from the sample; and

a controller for determining a Raman spectral response of the sample in response to the spectrum of light resolved by the spectrometer subsystem and the wavelength of the excitation signal from the wavelength reference system.

16. A system as claimed in claim 15, wherein the wavelength reference system comprises:

at least one reference detector; and

a wavelength reference element for filtering the excitation signal received by the wavelength reference detector.

17. A system as claimed in claim 15, wherein the wavelength reference system comprises:

a first reference detector;

a second reference detector;

a partial reflector for dividing the excitation between the first reference detector and the second reference detector; and

a wavelength reference element for filtering the excitation signal received by the first reference detector and the second reference detector.

18. A system as claimed in claim 17, wherein the controller uses the responses of the first reference detector and the second reference detector to determine the wavelength and a power of the excitation signal.

19. A system as claimed in claim 15, wherein the probe subsystem comprises separation optics for enabling transmission of the excitation beam to the sample and receipt of the light from the sample along a common axis and through a common aperture.

20. A system as claimed in claim 15, further comprising a fiber pigtail for transmitting the excitation signal from the semiconductor tunable laser subsystem to the probe subsystem.

21. A system as claimed in claim 15, wherein the probe subsystem comprises at least one polarizer for improving a polarization of the excitation signal.

22. A system as claimed in claim 15, further comprising polarization maintaining fiber for transmitting the excitation signal from the semiconductor tunable laser subsystem to the probe subsystem.

23. A Raman spectroscopy method, comprising:

generating an excitation signal having a varying wavelength within a scan range;

transmitting the excitation signal to a probe;

determining a wavelength of the excitation signal in the probe;

transmitting the excitation signal from the probe to a sample;

detecting light from the sample; and

determining a Raman spectral response of the sample in response to the detected light from the sample and the wavelength of the excitation signal.