Tunable spectroscopic source with power stability and method of operation

• US 20050286571A1
• Filed: 08/18/2005
• Published: 12/29/2005
• Est. Priority Date: 12/09/2002
• Status: Abandoned Application

• Current Assignee: Infraredx Incorporated (Nipro Corporation)
• Original Assignee: Infraredx Incorporated (Nipro Corporation)
• Inventors: Korn, Jeffrey A.
• Application Number:
  US11/207,042
• Publication Number:
  US 20050286571A1
• Time in Patent Office: Days
• US Class Current: 372/20
• CPC Class Codes: A61B 18/24 with a catheter A61B18/26, A61B18/28 take precedence
• CPC Class Codes: A61B 5/0075 by spectroscopy, i.e. measuring spectra, e.g. Raman spectroscopy, infrared absorption spectroscopy A61B5/0071 takes precedence
• CPC Class Codes: A61B 5/0086 using infrared radiation
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• CPC Class Codes: H01S 3/08 Construction or shape of optical resonators or components thereof
• CPC Class Codes: H01S 3/1055 one of the reflectors being constituted by a diffraction grating
• CPC Class Codes: H01S 5/068 Stabilisation of laser output parameters H01S5/0625 takes precedence
• CPC Class Codes: H01S 5/1039 Details on the cavity length
• CPC Class Codes: H01S 5/141 using a wavelength selective device, e.g. a grating or etalon H01S5/146 takes precedence
• CPC Class Codes: H01S 5/146 using a fiber as external cavity

Abstract

A laser system for a spectroscopic catheter system utilizes an overmoded cavity in order to reduce mode hoping induced power fluctuations during wavelength scanning. In the preferred embodiment, a semiconductor gain medium is used to reduce cost. A fiber pigtail is used to define the laser cavity, which has a tight cavity mode spacing of less that 15 Gigahertz. A diffraction grating is used as the tuning element. A cylindrical lens is used to reduce alignment tolerances and thereby increase manufacturability.

Claims

1. A tunable laser source having stable output power during wavelength scanning, the source comprising:

a laser cavity including;

a wavelength selector for scanning a passband over a scan band, and

a laser gain chip providing gain to longitudinal modes of the laser cavity within a gain bandwidth provided by the passband; and

wherein the laser cavity is characterized by a cavity longitudinal mode spacing that is more than two times smaller than the gain bandwidth.

2. A tunable laser source as claimed in claim 1, wherein the wavelength selector comprises a diffraction grating.

3. A tunable laser source as claimed in claim 1, wherein the wavelength selector comprises a bulk diffraction grating.

4. A tunable laser source as claimed in claim 1, wherein the wavelength selector comprises a Bragg grating.

5. A tunable laser source as claimed in claim 1, wherein the laser cavity further comprises an optical fiber pigtail coupling the laser gain chip and the wavelength selector.

6. A tunable laser source as claimed in claim 1, further comprising an output coupler for coupling laser light out of the laser cavity.

7. A tunable laser source as claimed in claim 6, wherein the output coupler provides the laser light to a catheter for insertion into a patient.

8. A tunable laser source as claimed in claim 1, wherein the laser gain chip comprises a semiconductor optical amplifier.

9. A tunable laser source as claimed in claim 1, wherein the laser gain chip comprises a reflective semiconductor optical amplifier.

10. A tunable laser source as claimed in claim 1, wherein an optical length of the laser cavity is greater than 10 centimeters.

11. A tunable laser source as claimed in claim 1, wherein an optical length of the laser cavity is greater than 50 centimeters.

12. A tunable laser source as claimed in claim 1, wherein an optical length of the laser cavity is greater than 1 meter.

13. A tunable laser source as claimed in claim 1, wherein the cavity mode spacing is less than 15 Gigahertz.

14. A tunable laser source as claimed in claim 1, wherein the cavity mode spacing is less than 1.5 Gigahertz.

15. A tunable laser source as claimed in claim 1, wherein the gain bandwidth is greater than 10 Gigahertz.

16. A tunable laser source as claimed in claim 1, wherein the gain bandwidth is greater than 50 Gigahertz.

17. A tunable laser source as claimed in claim 1, wherein the gain bandwidth is greater than 100 Gigahertz.

18. A tunable laser source as claimed in claim 1, further comprising at least two laser gain chips.

19. A tunable laser source as claimed in claim 1, wherein the laser gain chip is contained within a pigtailed hermetic package.