Semiconductor laser-based spectrometer

• US 20060280216A1
• Filed: 06/06/2006
• Published: 12/14/2006
• Est. Priority Date: 06/07/2005
• Status: Abandoned Application

• Current Assignee: Vijaysekhar Jayaraman
• Original Assignee: Vijaysekhar Jayaraman
• Inventors: Jayaraman, Vijaysekhar
• Application Number:
  US11/447,655
• Publication Number:
  US 20060280216A1
• Time in Patent Office: Days
• US Class Current: 372/50.121
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0218 using optical fibers
• CPC Class Codes: G01J 3/0256 Compact construction
• CPC Class Codes: G01J 3/10 Arrangements of light sources specially adapted for spectrometry or colorimetry
• CPC Class Codes: G01J 3/4338 Frequency modulated spectrometry
• CPC Class Codes: G01N 21/39 using tunable lasers
• CPC Class Codes: G02B 6/4202 for coupling an active element with fibres without intermediate optical elements, e.g. fibres with plane ends, fibres with shaped ends, bundles
• CPC Class Codes: H01S 5/02251 using optical fibres
• CPC Class Codes: H01S 5/4012 Beam combining, e.g. by the use of fibres, gratings, polarisers, prisms
• CPC Class Codes: H01S 5/4025 Array arrangements, e.g. constituted by discrete laser diodes or laser bar H01S5/42 takes precedence
• CPC Class Codes: H01S 5/4087 emitting more than one wavelength

Abstract

A semiconductor laser-based spectrometer according to the present invention includes a plurality of semiconductor lasers comprising a plurality of semiconductor gain medium compositions directly coupled to a large-core multi-mode fiber with no intervening optics. An output radiation from the multi-mode fiber is tunable by switching the drive current amongst the lasers, and by thermal tuning of each laser in the array. In combination with presentation to a sample, and means for detection of a diffuse reflectance or transmittance, this assembly functions as a compact, high signal to noise ratio, fast measurement spectrometer. In one preferred embodiment of this invention the plurality of semiconductor lasers consists of Fabry-Perot edge-emitting lasers arranged around the perimeter of a cylindrical submount with a substantially circular cross-section. In another preferred embodiment a linear array of Fabry-Perot edge-emitting lasers is directly coupled to a multi-mode fiber. In still another preferred embodiment, a two-dimensional array of vertical cavity surface-emitting lasers is directly coupled to a multi-mode optical fiber.

Claims

1. A tunable radiation source comprising

a plurality of semiconductor lasers comprising a plurality of semiconductor gain medium compositions, operative to emit a plurality of radiation components having a plurality of wavelengths

wherein each of said plurality of radiation components is directly coupled into one common multi-mode optical fiber with no optical components disposed between said plurality of semiconductor lasers and said multi-mode optical fiber,

and

means for directing electrical power to each one of said plurality of semiconductor lasers.

2. The tunable radiation source of claim 1, wherein said plurality of semiconductor lasers is a plurality of vertical cavity surface emitting lasers.

3. The tunable radiation source of claim 2, wherein said plurality of vertical cavity surface-emitting lasers is configured in a 2-dimensional array.

4. The tunable radiation source of claim 1, wherein said plurality of semiconductor lasers is a plurality of edge-emitting semiconductor lasers.

5. The tunable radiation source of claim 4, wherein said plurality of edge-emitting semiconductor lasers is a plurality of Fabry-Perot lasers.

6. The tunable radiation source of claim 4, wherein said plurality of edge-emitting semiconductor lasers is a plurality of grating-based semiconductor lasers.

7. The tunable radiation source of claim 4, wherein said plurality of edge-emitting semiconductor lasers encompasses between about 4 and about 16 edge-emitting semiconductor lasers.

8. The tunable radiation source of claim 1, further comprising means for thermally tuning at least one of said plurality of semiconductor lasers, thereby tuning at least one of said plurality of wavelengths.

9. The tunable radiation source of claim 5, further comprising means for thermally tuning at least one of said plurality of Fabry-Perot lasers, thereby tuning at least one of said plurality of wavelengths.

10. The tunable radiation source of claim 4, wherein said plurality of edge-emitting semiconductor lasers is arranged in a linear array.

11. The tunable radiation source of claim 4, wherein said plurality of edge-emitting semiconductor lasers is arranged in a 2-dimensional array.

12. The tunable radiation source of claim 1, wherein said multi-mode optical fiber has a core diameter in a range between about 100 microns and about 5 millimeters.

13. The tunable radiation source of claim 1, wherein said plurality of wavelengths is in a range between about 650 nm and about 1000 nm.

14. The tunable radiation source of claim 1, wherein said plurality of wavelengths is in a range between about 1100 nm and about 2500 nm.

15. The tunable radiation source of claim 1, wherein said plurality of wavelengths is in the range between about 800 nm and about 1700 nm.

16. The tunable radiation source of claim 9, wherein said plurality of wavelengths encompasses complete wavelength coverage over a range of at least about 200 nm.

17. The tunable radiation source of claim 1, further comprising means for electrically modulating at least one of said plurality of semiconductor lasers at frequencies in the range of about 100 Mhz to about 3 Ghz.

18. The tunable radiation source of claim 4, wherein said plurality of edge-emitting semiconductor lasers is arranged around the perimeter of a cylindrical sub-mount, wherein a cross-section of said cylindrical sub-mount is a polygon.

19. The tunable radiation source of claim 18, wherein said polygon has between about 4 and about 16 sides.

20. The tunable radiation source of claim 18, wherein said polygon is a circle.

21. The tunable radiation source of claim 18, further comprising a means for bending a path of said electrical power into a plane substantially perpendicular to an axis of said cylindrical submount.

22. The tunable radiation source of claim 21, wherein said means for bending a path of said electrical power is a flex circuit.

23. A spectrometer comprising the tunable source of claim 1, means for presenting an output radiation of said multi-mode fiber to a sample, and means for detecting at least one of a radiation reflected from said sample and a radiation transmitted through said sample.

24. The spectrometer of claim 23, wherein said sample is an in-vivo biological sample.

25. The spectrometer of claim 23, wherein said sample is an ex-vivo biological sample.

26. The spectrometer of claim 23, wherein said sample is an agricultural sample.

27. The spectrometer of claim 23, wherein said sample is a pharmaceutical sample.

28. A system for at least one of the detection, characterization, and therapeutic monitoring of breast cancer, the system comprising the tunable source of claim 1, a means for presenting an output radiation of said multi-mode fiber to in-vivo human breast tissue, and a means for detecting at least one of a radiation reflected from said breast tissue and a radiation transmitted through said breast tissue.

29. A system for at least one of the detection, characterization, and therapeutic monitoring of breast cancer, the system comprising the tunable source of claim 17, a means for presenting an output radiation of said multi-mode fiber to in-vivo human breast tissue, and a means for detecting at least one of a radiation reflected from said sample and a radiation transmitted through said sample.

30. The system of claim 28, wherein said plurality of wavelengths is in a range of about 650 nm to about 1000 nm.

31. The system of claim 29, wherein said plurality of wavelengths is in a range of about 650 nm to about 1000 nm.

32. The system of claim 28, wherein said plurality of wavelengths covers substantially all of a range from about 650 nm to about 1000 nm.

33. The system of claim 29, wherein said plurality of wavelengths covers substantially all of a range from about 650 nm to about 1000 nm.