Broadband or mid-infrared fiber light sources

• US 8,055,108 B2
• Filed: 02/05/2009
• Issued: 11/08/2011
• Est. Priority Date: 11/18/2005
• Status: Active Grant

• Current Assignee: Omni Continuum LLC
• Original Assignee: Cheetah Omni LLC
• Inventors: Islam, Mohammed N.
• Primary Examiner(s): PAK, SUNG H
• Application Number:
  US12/366,323
• Publication Number:
  US 20090204110A1
• Time in Patent Office: 1,006 Days
• Field of Search: None
• US Class Current: 385/122
• CPC Class Codes: G01B 9/02091 Tomographic interferometers, e.g. based on optical coherence
• CPC Class Codes: G01J 2003/102 Plural sources
• CPC Class Codes: G01J 2003/423 Spectral arrangements using lasers, e.g. tunable
• CPC Class Codes: G01J 3/0218 using optical fibers
• CPC Class Codes: G01J 3/0245 using an optical amplifier of light, e.g. doped fiber
• CPC Class Codes: G01J 3/108 for measurement in the infrared range
• CPC Class Codes: G01J 3/42 Absorption spectrometry; Double beam spectrometry; Flicker spectrometry; Reflection spectrometry beam switching arrangements G01J3/08
• CPC Class Codes: G02B 6/29349 Michelson or Michelson/Gires-Tournois configuration, i.e. based on splitting and interferometrically combining relatively delayed signals at a single beamsplitter
• CPC Class Codes: G02F 1/3528 for producing a supercontinuum
• CPC Class Codes: G02F 1/365 in an optical waveguide structure G02F1/377, G02F1/395 take precedence
• CPC Class Codes: G02F 2202/32 Photonic crystals
• CPC Class Codes: H01S 2301/085 solitons
• CPC Class Codes: H01S 3/06725 Fibre characterized by a specific dispersion, e.g. for pulse shaping in soliton lasers or for dispersion compensating [DCF]
• CPC Class Codes: H01S 3/06754 Fibre amplifiers H01S3/06708 takes precedence
• CPC Class Codes: H01S 3/094007 Cladding pumping, i.e. pump light propagating in a clad surrounding the active core
• CPC Class Codes: H01S 3/094069 Multi-mode pumping
• CPC Class Codes: H01S 3/094076 Pulsed or modulated pumping H01S3/1024 takes precedence
• CPC Class Codes: H01S 3/1024 for pulse generation
• CPC Class Codes: H01S 3/302 in an optical fibre
• CPC Class Codes: H01S 5/0064 Anti-reflection components, e.g. optical isolators
• CPC Class Codes: H01S 5/0085 : for modulating the output, i.e. the laser beam is modulated outside the laser cavity
• CPC Class Codes: H01S 5/0092 : for nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity
• CPC Class Codes: H01S 5/1092 : Multi-wavelength lasing
• CPC Class Codes: H01S 5/146 : using a fiber as external cavity
• CPC Class Codes: H01S 5/4012 : Beam combining, e.g. by the use of fibres, gratings, polarisers, prisms

Abstract

A broadband light source includes one or more laser diodes that are capable of generating a pump signal having a wavelength shorter than 2.5 microns, a pulse width of at least 100 picoseconds and a pump optical spectral width. The light source also includes one or more optical amplifiers that are coupled to the pump signal and are capable of amplifying the pump signal to a peak power of at least 500 W. The light source further includes a first fiber that is coupled to the one or more optical amplifiers. The first fiber including an anomalous group-velocity dispersion regime and a modulational instability mechanism that operates to modulate the pump signal. In one particular embodiment, the pump signal wavelength resides in the anomalous group-velocity dispersion regime of the first fiber and where different intensities in the pump signal can cause relative motion between different parts of the modulated pump signal produced through modulational instability in the first fiber. The light source also including a nonlinear element that is coupled to the first fiber that is capable of broadening the pump optical spectral width to at least 100 nm through a nonlinear effect in the nonlinear element.

Claims

1. An optical system for use in a medical procedure, the system comprising:

one or more laser diodes capable of generating one or more optical signals;

a gain fiber coupled to the one of more laser diodes, the gain fiber receiving the one or more optical signals and generating a corresponding pump signal having at least one wavelength;

a wavelength shifter coupled to the gain fiber, the wavelength shifter adapted to wavelength shift the at least one wavelength of the pump signal to a shifted pump wavelength based at least in part on a Raman wavelength shifting mechanism, wherein the shifted pump wavelength is in a wavelength range between approximately 1700 nm and 1900 nm; and

a lens system adapted to receive and deliver at least a portion of the wavelength-shifted pump signal to unwanted parts of tissue, to substantially damage the unwanted parts without significantly damaging surrounding tissue or tissue above the unwanted parts, wherein the shifted pump wavelength is selected to obtain a desired penetration depth and to substantially minimize water absorption, wherein the wavelength-shifted pump signal has a pulse width greater than approximately 100 picoseconds, wherein a time averaged output power of the wavelength-shifted pump signal is 20 mW or more, and wherein an intensity of the wavelength-shifted pump signal delivered by the lens system is less than approximately 50 MW/cm².

2. The optical system of claim 1, wherein the wavelength shifter comprises a Raman oscillator that comprises an optical fiber and a plurality of optical gratings.

3. The optical system of claim 1, wherein the gain fiber further comprises one or more optical gratings.

4. The optical system of claim 1, wherein the gain fiber is a cladding pumped fiber co-doped with erbium and ytterbium.

5. The optical system of claim 1, wherein the shifted pump wavelength is in a wavelength range between approximately 1710 nm and 1740 nm.

6. The optical system of claim 1, wherein at least the portion of the wavelength-shifted pump signal has a beam quality factor of M² less than approximately 1.4 and wherein the wavelength-shifted pump signal has a repetition rate between continuous wave and several Megahertz.

7. The optical system of claim 1, wherein the unwanted parts of tissue comprise protein, amino acids, or amide groups.

8. The optical system of claim 1, wherein the shifted pump wavelength comprises an optical wavelength where an optical absorption in the unwanted parts of tissue exceeds an optical absorption of water.

9. The optical system of claim 1, wherein the gain fiber coupled to the one or more laser diodes is a cladding pumped fiber laser and wherein the wavelength shifter is a cascaded Raman wavelength shifter comprising an optical fiber and a plurality of optical gratings.

10. The optical system of claim 9, wherein the cascaded Raman wavelength shifter is adapted to wavelength shift the at least one wavelength of the pump signal to the shifted pump signal through at least two Raman orders.

11. The optical system of claim 1, wherein the medical procedure is a minimally invasive procedure.

12. The optical system of claim 1, wherein the pulse width of the wavelength-shifted pump signal is less than 100 nanoseconds.

13. The optical system of claim 1, wherein the unwanted parts of tissue have at least in part nerve agents that disrupt one or more mechanisms by which nerves transfer messages to organs.