Controllable multi-wavelength laser source

• US 8,976,823 B2
• Filed: 09/12/2012
• Issued: 03/10/2015
• Est. Priority Date: 09/14/2011
• Status: Active Grant

• Current Assignee: IMRA America Incorporated (Aisin Corp.)
• Original Assignee: IMRA America Incorporated (Aisin Corp.)
• Inventors: Xu, Jingzhou, Cho, Gyu
• Primary Examiner(s): Park, Kinam
• Application Number:
  US13/611,646
• Publication Number:
  US 20130064256A1
• Time in Patent Office: 909 Days
• Field of Search: 372/27, 372/26, 372/21, 372/22, 372/6
• US Class Current: 372/27
• CPC Class Codes: G02B 5/3083 Birefringent or phase retarding elements G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001
• CPC Class Codes: G02F 1/353 Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams
• CPC Class Codes: G02F 1/3544 Particular phase matching techniques
• CPC Class Codes: G02F 1/3546 Active phase matching, e.g. by electro- or thermo-optic tuning
• CPC Class Codes: H01S 3/0092 Nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity nonlinear frequency conversion per se G02F1/35
• CPC Class Codes: H01S 3/067 Fibre lasers
• CPC Class Codes: H01S 3/06712 Polarising fibre; Polariser
• CPC Class Codes: H01S 3/06754 Fibre amplifiers H01S3/06708 takes precedence
• CPC Class Codes: H01S 3/10053 Phase control
• CPC Class Codes: H01S 3/10061 Polarization control

Abstract

In at least one embodiment a laser system includes a fiber laser source, a polarization controller and a wavelength converter. The relative power distribution between a pump wavelength and a signal wavelength is controllable using the polarization controller. An optional phase compensator is used to control polarization state of the output laser beam. In various embodiments the relative power distribution among multiple wavelengths may be controlled over a range of at least about 100:1.

Claims

1. A laser system, comprising:

a laser source which generates an input beam having a first wavelength;

a polarization controller to control a polarization of the input beam, said polarization controller comprising a phase retarder comprising a wave plate; and

a wavelength converter which receives the input beam from the polarization controller at a first wavelength and generates a wavelength converted beam in which at least a portion of beam power at the first wavelength is converted into beam power at a second wavelength, wherein the wavelength converter comprises a birefringent nonlinear crystal, wherein the wavelength conversion efficiency is determined by phase matching, said phase matching comprising quasi-phase matching, non-critical phase matching, or critical phase matching,

wherein the polarization controller is arranged in such a way that the relative power at each of the first and second wavelengths is controllable, and the laser system output comprises signal power at both the first and second wavelengths, and wherein a wavelength dependent signal power at the output of the wavelength converter can be varied from full available power output to near extinction.

2. The laser system in claim 1, wherein the laser source comprises rare earth doped optical fiber.

3. The laser system in claim 1, wherein the laser source comprises polarization maintaining fiber.

4. The laser system in claim 1, wherein the laser source comprises a pulsed laser that generates a pulsed laser beam having at least one pulse width in the femtosecond to picosecond range, wherein the relative power of corresponding input and wavelength converted pulses at respective first and second wavelengths is controllable with the polarization controller.

5. The laser system of claim 1, wherein the polarization controller comprises a liquid crystal phase retarder.

6. The laser system of claim 1, the polarization controller comprises a controllable Faraday rotator.

7. The laser system of claim 1, wherein a phase compensator is disposed downstream from the wavelength converter, and is arranged to control a polarization state at one or more wavelengths.

8. The laser system of claim 7, wherein the phase compensator comprises birefringent optics.

9. The laser system of claim 8, wherein the birefringent optics comprise a polarization maintaining fiber.

10. The laser system of claim 8, wherein the birefringent optics comprise two elements having a prism shape.

11. The laser system of claim 8, wherein the birefringent optics comprise an active phase retarder.

12. The laser system of claim 11, wherein the active phase retarder comprises an electro-optical phase modulator.

13. The laser system of claim 1, wherein one or more wavelength selective filters are disposed downstream from the wavelength converter to control the output energy fraction of the first and second wavelengths.

14. The laser system of claim 1, wherein the pulsed laser source comprises a fiber laser and/or amplifier.

15. The laser system of claim 1, further comprising a feedback controller to stabilize the output laser power.

16. The laser system of claim 1, wherein the first wavelength is a pump wavelength, the second wavelength is a signal wavelength, and the laser system is configured as a portion of a system for time gating pump and probe measurements, wherein energy at the first wavelength is used to excite an object and energy at the second wavelength is used as a probe.

17. The laser system of claim 1, wherein the laser system is configured as a portion of a material processing system in which energy at the first wavelength is used to pre-process a target material and energy at the second wavelength is used to further process the target material.

18. The laser system of claim 1, wherein the relative power is controllable over a control range of at least about 10:

1.

19. The laser system of claim 1, wherein the laser source comprises both a fiber laser and fiber amplifier.

20. The laser system of claim 1, wherein said non-linear crystal comprises periodically poled lithium niobate (PPLN).

21. The laser system of claim 1, wherein said non-linear crystal comprises lithium triborate (LBO).

22. A laser system comprising:

a fiber-based laser source which generates an input beam having a first wavelength, the source comprising a fiber-based laser and/or amplifier;

a polarization controller arranged in such a way as to control a polarization of an input beam received from the laser source, and to output a first beam having a first wavelength and a desired polarization, said polarization controller being capable of polarization adjustment over a substantially continuous range from full available power to near extinction, said polarization controller comprising a phase-retarder, comprising a wave plate; and

a wavelength converter which receives the first beam from the polarization controller and generates a wavelength converted beam in which at least a portion of beam power at the first wavelength is converted into beam power at a second wavelength, wherein the wavelength converter comprises a birefringent nonlinear crystal, where the wavelength conversion efficiency is determined by phase matching, said phase matching comprising quasi-phase matching , non-critical phase matching, or critical phase matching,

wherein the polarization controller is arranged in such a way that the relative power at each of the first and second wavelengths is controlled by the polarization controller, and the laser system output comprises signal power at both the first and second wavelengths.

23. The laser system of claim 22, further comprising a phase compensator disposed downstream from the wavelength converter to control a beam polarization at one or more wavelengths.

24. The laser system of claim 22, wherein the fiber-based laser source comprises a polarization maintaining fiber.

25. The laser system of claim 22, wherein the polarization controller provides a preset polarization of the input beam such that the relative output power detectable at the first and second wavelengths is substantially constant.

26. The laser system of claim 22, further comprising:

a spectral selective filter to select either the first wavelength or the second wavelength.

27. The laser system of claim 22, wherein non-linear crystal comprises periodically poled lithium niobate (PPLN).

28. The laser system of claim 22, wherein said non-linear crystal comprises lithium triborate (LBO).

29. The laser system of claim 22, wherein the laser source comprises both a fiber laser and fiber amplifier.

30. The laser system in claim 22, wherein the fiber-based laser source comprises a pulsed laser that generates a pulsed laser beam having at least one pulse width in the femtosecond to picosecond range, wherein the relative power of corresponding input and wavelength converted pulses at respective first and second wavelengths is controllable with the polarization controller.

31. The laser system of claim 22, wherein one or more wavelength selective filters are disposed downstream from the wavelength converter to control the output energy fraction of the first and second wavelengths.

32. The laser system of claim 22, wherein the phase compensator comprises birefringent optics.

33. A laser system, comprising:

a laser source which generates an input beam having a first wavelength;

a polarization controller to control a polarization of the input beam;

a wavelength converter which receives the input beam from the polarization controller and generates a wavelength converted beam in which at least a portion of beam power at the first wavelength is converted into beam power at a second wavelength, wherein the polarization controller is arranged in such a way that the relative power at each of the first and second wavelengths is controllable, and the laser system output comprises signal power at both the first and second wavelengths; and

a phase compensator to compensate phase retardation at one or both wavelength(s) generated in the wavelength converter.

34. The laser system of claim 33, comprising a spectral selective filter to select either a first wavelength or the second wavelength.