Tunable blue laser diode

• US 6,021,141 A
• Filed: 02/28/1997
• Issued: 02/01/2000
• Est. Priority Date: 03/29/1996
• Status: Expired due to Term

• Current Assignee: Lumentum Operations, LLC (Lumentum Holdings Inc.)
• Original Assignee: SDL PLC (RWS Holdings Plc)
• Inventors: Waarts, Robert G., Nam, Derek W., Welch, David F., Major, Jo S.
• Primary Examiner(s): Scott, Jr., Leon
• Application Number:
  US08/808,737
• Time in Patent Office: 1,068 Days
• Field of Search: 372/20, 372/22, 372/6, 372/34, 372/102, 372/92, 372/64, 372/26, 372/36, 372/75, 372/96, 372/5, 372/99
• US Class Current: 372/20
• CPC Class Codes: H01S 5/02 Structural details or components not essential to laser action

Abstract

A harmonic generator laser system which features a distributed Bragg reflector (DBR) or distributed feedback (DFB) tunable diode laser coupled to a quasi-phase matched (QPM) waveguide of optically nonlinear material. Tuning of the DBR laser may be achieved either thermally or via current injection, or both, halving the wavelength of a red laser into the visible blue spectral band. Thermal tuning may provide a coarse tuning adjustment, while injected current may provide fine tuning accessible to a user. Separately or in combination with current tuning, a modulation signal may be applied to the DBR laser for achieving an intensity modulated or a pulsed output. In another embodiment, modulation may be achieved by frequency modulation of the laser. A very compact tunable blue laser is formed. In yet another embodiment a double clad fiber amplifier is disposed between the tunable laser and the waveguide. The fiber amplifier is pumped by a high power laser, while the core guides light to be frequency doubled in the nonlinear material from a continuously tunable laser.

Claims

1. A frequency converting light emitting device comprising,

a semiconductor laser emitting a light beam of a first wavelength,

a nonlinear frequency converting material optically coupled to said laser to receive said light beam, said nonlinear converting material oriented for carrying out frequency conversion of said light beam received from said laser, said nonlinear frequency converting material having a temperature dependent resonance wavelength band for converting light of said first wavelength that coincides with said resonance wavelength band to a second wavelength;

temperature control means in thermal communication with said nonlinear frequency converting material for setting a temperature of said nonlinear frequency

converting material to correspond to a selected resonance wavelength band including said second wavelength;

means for coarse tuning said laser such that said first wavelength of said light beam emitted by said laser coincides with said selected resonance wavelength band of said nonlinear frequency converting material for converting to said second wavelength;

said temperature control means for fine tuning said second wavelength after coarse tuning of said first wavelength.

2. The frequency converting light emitting device of claim 1 further comprising said means in thermal communication with said laser for wavelength tuning said laser via adjustment to its operational temperature.

3. The frequency converting light emitting device of claim 1 wherein said laser includes resonant optical cavity, a reflector in said cavity for providing optical feedback at said first wavelength.

4. The frequency converting light emitting device of claim 1 wherein said means for tuning said first wavelength includes current injection means for applying a tuning current to said laser.

5. The frequency converting light emitting device of claim 4 wherein said laser includes a grating region capable of variable refractive index, said tuning current applied to said grating region.

6. The frequency converting light emitting device of claim 4 wherein said laser includes modulation means for modulating said light beam.

7. The frequency converting light emitting device of claim 1 wherein said laser tuning means comprises means for applying a tuning current to a region of said laser proximate to said reflector.

8. The frequency converting light emitting device of claim 1 wherein said nonlinear material includes a quasi-phase-matched waveguide.

9. The frequency converting light emitting device of claim 1 further defined by servo means for matching the wavelength of said laser to the resonance condition of said nonlinear frequency converting material.

10. The frequency converting light emitting device of claim 1 further comprising a fiber amplifier having an input optically coupled to receive and amplify said semiconductor laser light beam and having an output comprising the amplified laser light beam optically coupled as an input to said nonlinear frequency converting material.

11. The frequency converting light emitting device of claim 10 wherein said fiber amplifier comprises a double clad fiber with a central core doped with an active light amplifying element.

12. The frequency converting light emitting device of claim 1 wherein said laser is a DBR laser and said reflector is a DBR grating.

13. The frequency converting light emitting device of claim 1 wherein a planar extent of said laser is substantially orthogonal relative to said nonlinear frequency converting material.

14. The frequency converting light emitting device of claim 1 wherein said laser and said nonlinear frequency converting material are optically butt coupled.

15. The frequency converting light emitting device of claim 1 wherein said temperature control means is a thermoelectric cooler.

16. The frequency converting light emitting device of claim 1 wherein said temperature control means is a heater.

18. The laser device of claim 1 wherein said second frequency tuning means comprises a thermoelectric cooler, a heater, or an annealing process and said first frequency tuning means comprises a thermoelectric cooler or a heater.

17. A laser device comprising:

a laser oscillator having a first frequency;

a nonlinear optical waveguide for converting the laser first frequency to a second frequency, the waveguide having means for selectively tuning the second frequency;

means to optically couple said laser oscillator to said waveguide;

thermal applying means for tuning the first frequency; and

means for tuning the second frequency in conjunction with tuning the first frequency so that said first and second frequencies are phase matched for efficient frequency conversion.

19. A laser device comprising:

a laser oscillator having a first frequency, the laser oscillator having first means for selectively tuning the first frequency;

a nonlinear optical waveguide for converting the laser frequency to a second frequency, the waveguide having second means for selectively tuning the second frequency;

means to optically couple said laser oscillator to said waveguide;

said first and second means for independently tuning the first and second frequencies so that said first and second frequencies are phase matched for efficient frequency conversion of said first frequency to said second frequency.

20. The laser device of claim 19 further comprising means for tuning the first frequency after tuning the second frequency so that said first and second resonant frequencies are phase matched for efficient frequency conversion.

21. The laser device of claim 20 wherein said first frequency tuning means comprises a thermoelectric cooler or a heater and said second frequency tuning means comprises a thermoelectric cooler, a heater, or an annealing process.

22. The laser device of claim 19 further comprising a grating for selecting the first wavelength of said laser oscillator.

23. A method of tuning a system comprising a laser having an output of a first frequency optically coupled to a frequency converting waveguide for converting the laser first frequency to a second frequency provided at its output, comprising the steps of:

operating the laser to provide a light beam into the frequency converting waveguide;

annealing the frequency converting waveguide while monitoring the resonant wavelength of the same;

terminating annealing after the first resonant frequency coincides with the resonance wavelength band of the frequency converting waveguide including the second frequency; and

tuning the laser to maintain its output substantially the same as the first frequency so that conversion to the second frequency is maintained.

24. The method of claim 23 wherein the step of tuning the laser comprises the step of adjusting the temperature of the laser.

25. The method of claim 24 wherein the step of tuning the laser comprises employment of a thermoelectric cooler.

26. The method of claim 24 wherein the step of tuning the laser comprises employment of a heater.

27. The method of claim 23 wherein the step of tuning the laser comprises the step of applying a tuning current to the laser.

28. The method of claim 23 further comprising the step of providing a wavelength reflector in the laser for providing feedback to maintain its operation substantially at the first frequency, the step of tuning the laser comprises the step of heating a region of the laser at or in proximity to the reflector.

29. The method of claim 23 further comprising the step of providing a wavelength reflector in the laser for providing feedback to maintain its operation substantially at the first frequency, the step of tuning the laser comprises the step of applying a tuning current to a region of the laser at or in proximity to the reflector.

30. A frequency converting light emitting device comprising,

a semiconductor laser having means for selecting a lasing wavelength;

a nonlinear frequency doubler operating at a wavelength within a range of wavelengths;

means for tuning said nonlinear frequency doubler to a conversion frequency within said wavelength range;

means for optically coupling the nonlinear frequency doubler with the laser;

said selecting means selective of a lasing wavelength and said tuning means selective of a conversion wavelength independently adjusted to provide for optimum conversion efficiency of said lasing wavelength to said conversion wavelength.

31. The laser device of claim 30 wherein said doubler nonlinear frequency material includes a waveguide therein.

32. The laser device of claim 30 wherein said selecting means is a grating in said laser.

33. The laser device of claim 30 wherein said laser is tunable via said selecting means over a range of wavelengths.

34. The laser device of claim 33 wherein said selecting means is a grating in said laser.

35. The laser device of claim 30 wherein said nonlinear frequency doubler includes means for tuning over a range of wavelengths.

36. The laser device of claim 30 wherein said nonlinear frequency doubler and said laser are independently tunable over a range of wavelengths.

37. The laser device of claim 30 wherein said selecting means in said laser is a DBR or a DFB structure.

38. The laser device of claim 37 wherein said selecting means in said laser further comprises means for applying a tuning source to said laser.

39. The laser device of claim 30 wherein said selecting means in said laser and said tuning means in said nonlinear frequency doubler comprises at least one thermoelectric cooler or at least one heater.

40. The laser device of claim 30 further comprising a temperature controlling means for said nonlinear frequency doubler.

41. The laser device of claim 40 wherein said temperature controlling means comprises a thermo electric cooler or a heater.

42. The laser device of claim 30 wherein said selecting means in said laser and said tuning means in said nonlinear frequency doubler comprises one independently controlled thermoelectric cooler or heater for each of said laser and said nonlinear frequency doubler.