Tunable laser having liquid crystal waveguide

• US 20050265403A1
• Filed: 01/21/2005
• Published: 12/01/2005
• Est. Priority Date: 01/22/2004
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Vescent Photonics Incorporated
• Inventors: Anderson, Michael H., Davis, Scott R., Rommel, Scott D.
• Granted Patent: US 7,720,116 B2
• Time in Patent Office: Days
• US Class Current: 372/20
• CPC Class Codes: H01S 3/0826 using a diffraction grating
• CPC Class Codes: H01S 3/105 by controlling the mutual position or the reflecting properties of the reflectors of the cavity , e.g. by controlling the cavity lengthH01S3/10076, H01S3/13 take precedence
• CPC Class Codes: H01S 3/107 using electro-optic devices, e.g. exhibiting Pockels or Kerr effect H01S3/1061, H01S3/1063, H01S3/1065 take precedence
• CPC Class Codes: H01S 5/005 Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping H01S5/026, H01S5/18388 take precedence
• CPC Class Codes: H01S 5/02315 Support members, e.g. bases or carriers
• CPC Class Codes: H01S 5/02326 Arrangements for relative positioning of laser diodes and optical components, e.g. grooves in the mount to fix optical fibres or lenses
• CPC Class Codes: H01S 5/0233 Mounting configuration of laser chips
• CPC Class Codes: H01S 5/0235 Method for mounting laser chips
• CPC Class Codes: H01S 5/142 which comprises an additional resonator
• CPC Class Codes: H01S 5/143 Littman-Metcalf configuration, e.g. laser - grating - mirror
• CPC Class Codes: H01S 5/146 using a fiber as external cavity

Abstract

A tunable laser for providing a laser beam with a selectable wavelength. In one example, the tunable laser includes a gain medium for generating the laser beam; a waveguide for processing the laser beam, the waveguide having liquid crystal material or other electro-optic material disposed therein; an optical path length control element disposed within said waveguide for controlling an effective optical path length of the laser cavity; and a wavelength selective element for controlling the wavelength of the laser beam. The tunable laser may be designed without any moving mechanical parts if desired.

Claims

1. A tunable laser for providing a laser beam characterized by a wavelength, the tunable laser defining a laser cavity, the tunable laser comprising:

a gain medium for generating the laser beam;

a waveguide for processing the laser beam, the waveguide having liquid crystal material disposed therein;

an optical path length control element disposed within said waveguide for controlling an effective optical path length of the laser cavity; and

a wavelength selective element for controlling the wavelength of the laser beam.

2. The tunable laser of claim 1, wherein the gain medium is a laser diode.

3. The tunable laser of claim 1, wherein the waveguide further comprises:

a core for guiding the laser beam through the waveguide; and

a cladding having a liquid crystal material therein.

4. The tunable laser of claim 3, wherein the optical path length control element includes an electrode for receiving a first voltage for controlling the effective optical path length of the laser cavity.

5. The tunable laser of claim 4, wherein the electrode has a generally rectangular portion.

6. The tunable laser of claim 4, wherein the electrode is positioned adjacent the cladding in the waveguide and when the first voltage is applied to the electrode, the electrode induces an electric field on the liquid crystal material proximate the electrode to alter the effective optical path length of the laser cavity.

7. The tunable laser of claim 4, wherein the electrode is formed using ITO material.

8. The tunable laser of claim 4, wherein the electrode is formed using a conductive layer.

9. The tunable laser of claim 3, wherein the core includes a tantalum pentoxide material.

10. The tunable laser of claim 1, wherein the liquid crystal material is a nemetic material.

11. The tunable laser of claim 3, wherein the wavelength selective element includes an electrode disposed within said waveguide for receiving a second voltage for controlling the wavelength of the laser beam.

12. The tunable laser of claim 11, wherein the electrode of the wavelength selective element has a generally triangular portion.

13. The tunable laser of claim 11, wherein the electrode of the wavelength selective element includes a plurality of refractive shapes.

14. The tunable laser of claim 11, wherein the electrode of the wavelength selective element is positioned adjacent the cladding in the waveguide and when the second voltage is applied to the electrode, the electrode induces an electric field on the liquid crystal material proximate the electrode to steer the laser beam.

15. The tunable laser of claim 11, wherein the electrode of the wavelength selective element is formed using ITO material.

16. The tunable laser of claim 1, wherein the waveguide has a front and rear facet, the tunable laser further comprising:

a diffraction grating coupled with a rear facet of the waveguide.

17. The tunable laser of claim 16, wherein the wavelength selective element controls an angle at which the laser beam strikes the diffraction grating.

18. The tunable laser of claim 17, wherein the tunable laser is configured as a Littrow-type external cavity diode laser.

19. The tunable laser of claim 1, wherein the waveguide has a front facet, a top facet, and a bottom facet, the tunable laser further comprising:

a diffraction grating coupled with the bottom facet of the waveguide; and

a reflector coupled with the top facet of the waveguide.

20. The tunable laser of claim 19, wherein the wavelength selective element controls an angle at which the laser beam strikes the reflector and reflects back into the diffraction grating coupled with the bottom facet.

21. The tunable laser of claim 20, wherein the tunable laser is configured as a Littman-Metcalf type external cavity diode laser.

22. The tunable laser of claim 1, wherein the waveguide further comprises:

a core for guiding the laser beam through the waveguide;

a cladding having a liquid crystal material therein; and

a Bragg grating.

23. The tunable laser of claim 22, wherein the Bragg grating is embedded along a portion of the core.

24. The tunable laser of claim 22, wherein the Bragg grating is embedded along a portion of the cladding.

25. The tunable laser of claim 22, wherein the optical path length control element includes an electrode for receiving a first voltage for controlling the effective optical path length of the laser cavity.

26. The tunable laser of claim 25, wherein the electrode of the optical path length control element has a generally rectangular portion.

27. The tunable laser of claim 22, wherein the wavelength selective element includes an electrode disposed in said waveguide for receiving a second voltage for controlling the wavelength of the laser beam.

28. The tunable laser of claim 27, wherein the electrode of the wavelength selective element is positioned adjacent the Bragg grating in the waveguide, and when the second voltage is applied to the electrode, the electrode induces an electric field on the liquid crystal material of the Bragg grating to selectively reflect wavelengths of the laser beam.

29. The tunable laser of claim 22, wherein the core of the waveguide includes a channel.

30. The tunable laser of claim 1, wherein the waveguide further comprises:

a core for guiding the laser beam through the waveguide;

a cladding having a liquid crystal material therein; and

an out-coupling grating.

31. The tunable laser of claim 30, further comprising:

a prism coupled with a surface of the waveguide proximate the out-coupling grating; and

a reflector coupled with the prism.

32. The tunable laser of claim 1, wherein the optical path length control element includes an electrode for receiving a first voltage for controlling the effective optical path length of the laser cavity, and the wavelength selective element includes an electrode for receiving a second voltage for controlling the wavelength of the laser beam.

33. The tunable laser of claim 32, wherein the first and second voltages are adjusted synchronously in order to provide mode-hop free tuning.

34. The tunable laser of claim 1, wherein the optical path length control element and the wavelength selective element are controlled by a single electrode for receiving a voltage for simultaneously controlling the effective optical path length of the laser cavity and the wavelength of the laser beam.

35. The tunable laser of claim 34, wherein the single electrode controls an angle at which the laser beam propagates within the waveguide.

36. The tunable laser of claim 34, wherein the single electrode alters the optical path length of the laser cavity and the wavelength of the laser beam in a synchronous manner so as to provide substantially mode hop free tuning.

37. The tunable laser of claim 1, wherein the wavelength selective element has a non-normal interface.

38. The tunable laser of claim 1, wherein the wavelength selective element includes a cavity in the waveguide, the cavity defining a non-normal interface for steering the laser beam.

39. The tunable laser of claim 1, wherein the waveguide is substantially planar.

40. The tunable laser of claim 1, further comprising coupling optics positioned between the gain medium and the waveguide.

41. A tunable laser having a laser cavity, comprising:

a gain medium for generating light; and

a waveguide for processing the light within the laser cavity, the waveguide having liquid crystal material disposed therein.

42. The tunable laser of claim 41, wherein the waveguide further comprises:

a core for guiding the light through the waveguide; and

at least one cladding having a liquid crystal material therein.

43. The tunable laser of claim 41, wherein the waveguide further comprises:

an optical path length control element for controlling an effective optical path length of the laser cavity; and

a wavelength selective element for controlling the wavelength of the light.

44. A tunable laser, comprising:

a gain medium for generating a laser beam; and

a waveguide for processing the laser beam, the waveguide having liquid crystal material disposed therein and at least one electrode having a portion with a generally triangular shape for controlling the direction the laser beam within the waveguide.

45. The tunable laser of claim 44, wherein the waveguide further comprises:

a core for guiding the laser beam through the waveguide; and

at least one cladding having a liquid crystal material therein.

46. The tunable laser of claim 44, wherein the waveguide further comprises:

an optical path length control element for controlling an effective optical path length of the tunable laser.

47. A tunable laser having a laser cavity, comprising:

a gain medium for generating a laser beam;

a waveguide for processing the laser beam, the waveguide having liquid crystal material disposed therein; and

an optical path length control element disposed in said waveguide for controlling an effective optical path length of the laser cavity.

48. The tunable laser of claim 47, further comprising a wavelength selective element for controlling the wavelength of the light.

49. A tunable laser having a laser cavity, comprising:

a gain medium for generating a laser beam;

a waveguide for processing the laser beam, the waveguide having electro-optic material disposed therein; and

an optical path length control element disposed in said waveguide for controlling an effective optical path length of the laser cavity; and

a wavelength selective element disposed in said waveguide for controlling the wavelength of the laser beam, wherein the wavelength selective element steers the laser beam within the waveguide.

50. The tunable laser of claim 49, wherein the waveguide has a front facet and a rear facet, the tunable laser further comprising:

a diffraction grating coupled with the rear facet of the waveguide.

51. The tunable laser of claim 50, wherein the wavelength selective element controls an angle at which the laser beam strikes the diffraction grating.

52. The tunable laser of claim 51, wherein the optical path length control element and the wavelength selective element are controlled by a single electrode for receiving a voltage for simultaneously controlling the effective optical path length of the laser cavity and the wavelength of the laser beam.

53. The tunable laser of claim 52, wherein the single electrode alters the optical path length of the laser cavity and the wavelength of the laser beam in a synchronous manner so as to provide substantially mode hop free tuning.

54. A tunable laser for providing a laser beam characterized by a wavelength, the tunable laser defining a laser cavity, the tunable laser comprising:

a gain medium for generating the laser beam;

a waveguide for processing the laser beam, the waveguide having liquid crystal material disposed therein;

an optical path length control element disposed within said waveguide for controlling an effective optical path length of the laser cavity, the optical path length control element including at least a first electrode for receiving a first voltage; and

a wavelength selective element for controlling the wavelength of the laser beam, the wavelength selective element including at least a second electrode for receiving a second voltage.

55. A tunable laser for providing a laser beam characterized by a wavelength, the tunable laser defining a laser cavity, the tunable laser comprising:

a gain medium for generating the laser beam;

a waveguide for processing the laser beam, the waveguide having liquid crystal material disposed therein;

a wavelength selective element disposed within said waveguide for controlling the wavelength of the laser beam; and

an optical path length control element for controlling an effective optical path length of the laser cavity.

56. The tunable laser of claim 55, wherein the wavelength selective element includes a beam steering element.

57. The tunable laser of claim 56, wherein the beam steering element includes an electrode.

58. The tunable laser of claim 55, further comprising a diffraction grating coupled to the waveguide.

59. A method for controlling the wavelength of a laser beam of a laser, comprising:

providing a waveguide for processing the laser beam, the waveguide having electro-optic material disposed therein, the waveguide having a wavelength selective element disposed within said waveguide for controlling the wavelength of the laser beam and an optical path length control element for controlling an effective optical path length of the laser;

applying a first control voltage to the wavelength selective element to control the wavelength of the laser beam; and

applying a second control voltage to the optical path length control element to control the effective optical path length of the laser.

60. The method of claim 59, wherein the operation of applying the first control voltage occurs substantially synchronously with the operation of applying the second control voltage in order to provide mode hop free tuning of the laser beam.