Method and apparatus for waveguide optics and devices

• US 6,330,388 B1
• Filed: 01/22/2000
• Issued: 12/11/2001
• Est. Priority Date: 01/27/1999
• Status: Expired due to Fees

• Current Assignee: Teem Photonics
• Original Assignee: Northstar Photonics, Inc. (Teem Photonics S.A.)
• Inventors: Bendett, Mark P., McCoy, Michael A.
• Primary Examiner(s): Kim, Ellen E.
• Application Number:
  US09/490,168
• Time in Patent Office: 689 Days
• Field of Search: 385/1, 385/4-6, 385/11-14, 385/129-132, 372/41, 372/102, 372/19, 372/6, 372/94, 372/81, 372/92, 372/93, 372/97, 372/99, 372/98
• US Class Current: 385/132
• CPC Class Codes: C03C 4/00 Compositions for glass with special properties
• CPC Class Codes: G02B 2006/12107 Grating
• CPC Class Codes: G02B 2006/12121 Laser
• CPC Class Codes: G02B 2006/1215 Splitter
• CPC Class Codes: G02B 2006/12183 Ion-exchange
• CPC Class Codes: G02B 6/12004 Combinations of two or more optical elements
• CPC Class Codes: G02B 6/12007 forming wavelength selective elements, e.g. multiplexer, demultiplexer
• CPC Class Codes: G02B 6/124 Geodesic lenses or integrated gratings
• CPC Class Codes: G02B 6/125 Bends, branchings or intersections
• CPC Class Codes: G02B 6/1345 using ion exchange ion exchange in glass C03C21/00
• CPC Class Codes: G02B 6/2551 using thermal methods, e.g. fusion welding by arc discharge, laser beam, plasma torch
• CPC Class Codes: G02B 6/30 for use between fibre and thin-film device
• CPC Class Codes: G02B 6/3508 Lateral or transverse displacement of the whole waveguides, e.g. by varying the distance between opposed waveguide ends, or by mutual lateral displacement of opposed waveguide ends
• CPC Class Codes: G02B 6/4249 comprising arrays of active devices and fibres
• CPC Class Codes: H01S 2302/00 Amplification / lasing wavelength
• CPC Class Codes: H01S 3/0621 Coatings on the end-faces, e.g. input/output surfaces of the laser light
• CPC Class Codes: H01S 3/063 Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength waveguide gas lasers H01S3/0315
• CPC Class Codes: H01S 3/0632 Thin film lasers in which light propagates in the plane of the thin film
• CPC Class Codes: H01S 3/0635 provided with a periodic structure, e.g. using distributed feed-back, grating couplers controlling, e.g. modulating distributed feed-back lasers H01S3/102
• CPC Class Codes: H01S 3/0637 Integrated lateral waveguide, e.g. the active waveguide is integrated on a substrate made by Si on insulator technology (Si/SiO2)
• CPC Class Codes: H01S 3/08086 : Multiple-wavelength emission
• CPC Class Codes: H01S 3/094053 : Fibre coupled pump, e.g. delivering pump light using a fibre or a fibre bundle
• CPC Class Codes: H01S 3/094084 : with pump light recycling, i.e. with reinjection of the unused pump light, e.g. by reflectors or circulators
• CPC Class Codes: H01S 3/0941 : of a laser diode
• CPC Class Codes: H01S 3/09415 : the pumping beam being parallel to the lasing mode of the pumped medium, e.g. end-pumping
• CPC Class Codes: H01S 3/1055 : one of the reflectors being constituted by a diffraction grating
• CPC Class Codes: H01S 3/1608 : erbium
• CPC Class Codes: H01S 3/1611 : neodymium
• CPC Class Codes: H01S 3/1618 : ytterbium
• CPC Class Codes: H01S 3/17 : amorphous, e.g. glass
• CPC Class Codes: H01S 3/175 : phosphate glass
• CPC Class Codes: H01S 3/176 : silica or silicate glass
• CPC Class Codes: H01S 3/2383 : Parallel arrangements
• CPC Class Codes: H01S 3/2391 : emitting at different wavelengths
• CPC Class Codes: H01S 5/0654 : Single longitudinal mode emission

Abstract

Optical structures and method for producing tunable waveguide lasers. In one embodiment, a waveguide is defined within a glass substrate doped with a rare-earth element or elements by ion diffusion. Feedback elements such as mirrors or reflection gratings in the waveguide further define a laser-resonator cavity so that laser light is output from the waveguide when pumped optically or otherwise. Means are disclosed for varying the wavelengths reflected by the reflection gratings and varying the effective length of the resonator cavity to thereby tune the laser to a selected wavelength. Apparatus and method for integrating rare-earth doped lasers and optics on glass substrates. The invention includes a laser component formed from a glass substrate doped with a optically active lanthanides species with a plurality of waveguides defined by channels within the substrate. The laser component may constitute a monolithic array of individual waveguides in which the waveguides of the array form laser resonator cavities with differing resonance characteristics. The channels defining the waveguides are created by exposing a surface of the substrate to an ion-exchange solvent through a mask layer having a plurality of line apertures corresponding to the channels which are to be formed.

Claims

1. A laser component comprising:

a glass substrate doped with a laser species and having a plurality of waveguides defined by channels within the substrate, each one of the plurality of waveguides forming a laser-resonator cavity with a distinct resonance characteristic to provide lasing action at a selected wavelength when pumped, wherein the substrate is an alkali phosphate glass doped with Er and Yb and wherein the channels are formed at a surface of the substrate as regions of increased refractive index;

one or more feedback elements for providing optical feedback to the waveguides to form the one or more laser-resonator cavities, wherein injection of pump light at one or more suitable wavelengths into the laser-resonator cavity causes output of laser light at a wavelength in accordance with a longitudinal cavity mode of the cavity and wherein the laser-resonator cavities have a plurality of widths on the substrate surface to thereby define a plurality of effective indices of refraction for the cavities, the wavelength of a longitudinal cavity mode being dependent thereon;

a ferrule having a plurality of spaced-apart attachment sites; and

a plurality of optic fibers attached to the ferrule, each optic fiber attached to its own attachment site wherein each attachment site corresponds to a different group of cavities, each group including a plurality of cavities, such that each of the optic fibers is coupled to a corresponding one cavity on a different one of the groups.

2. The laser component according to claim 1, further comprising:

a silicon oxide layer formed on a surface of the glass substrate; and

a surface-relief diffraction grating formed into the silicon oxide layer, wherein the silicon oxide layer is of sufficient depth for the diffraction grating to be formed at least in part in the silicon oxide layer.

3. The laser component of claim 2 wherein the diffraction grating forms a diffraction Bragg reflector (DBR) mirror extending only into silicon oxide layer.

4. The laser component of claim 2 wherein the diffraction grating is formed only into the silicon oxide layer and not into the substrate.

5. The laser component of claim 2 wherein the silicon oxide layer has a thickness in a range of between about 500 nm and about 2000 nm.

6. The laser component of claim 2, wherein the silicon oxide layer has a thickness in a range of between about 1000 nm and about 2000 nm.

7. The laser component according to claim 1, further comprising:

at least one pump that excites the laser species of the substrate waveguides;

a first surface-relief reflection grating formed on the substrate waveguide for providing feedback of a first one of the one or more feedback elements to the resonator cavity;

means for tuning the laser by altering the wavelength reflected by the first grating, wherein the laser tuning means comprises;

an electro-optic material optically coupled to the first grating; and

electrodes for applying an electrical potential across the electro-optic material to vary an index of refraction in accordance therewith and thereby vary a wavelength of light reflected by the first grating.

8. The laser of claim 7 wherein a voltage to the electro-optic material is varied to vary a reflection coefficient of the grating.

9. The laser of claim 7 wherein a voltage to the electro-optic material is varied to maximize a reflection coefficient of the grating.

10. The laser of claim 7 wherein a voltage to the electro-optic material is varied to minimize a reflection coefficient of the grating.

11. The laser of claim 7 wherein a voltage to the electro-optic material is selected to maximize a reflection coefficient of the first grating in order to select a lasing wavelength determined by the first grating.

12. The laser of claim 7 wherein a voltage to the electro-optic material is selected to minimize a reflection coefficient of the first grating in order to select a lasing wavelength determined by a grating other than the first grating.

13. The laser component of claim 1, further comprising:

one or more pump light sources operatively coupled to the cavities; and

packaging enclosing the laser component.

14. The laser component of claim 1, further comprising:

a silicon oxide layer formed on a surface of the glass substrate, wherein the one or more feedback elements comprise a surface-relief diffraction grating formed into the silicon oxide layer, wherein the silicon oxide layer is of sufficient depth for the diffraction grating to be formed at least in part in the silicon oxide layer.

15. The laser component of claim 14, wherein the diffraction grating is formed only into the silicon oxide layer and not into the substrate.

16. The laser component of claim 13, wherein the silicon oxide layer has a thickness in a range of between about 1000 nm and about 2000 nm.

17. The laser component of claim 1, wherein the one or more feedback elements comprise:

a first surface-relief diffraction grating on the substrate waveguide that provides feedback to the resonator cavity;

an electro-optic material optically coupled to the first grating; and

electrodes that apply an electrical potential across the electro-optic material to vary an index of refraction in accordance therewith and thereby control a wavelength of the resonator cavity.

18. The laser component of claim 17 wherein a voltage to the electro-optic material is selected to maximize a reflection coefficient of the first grating and thereby control a wavelength of the resonator cavity.

19. The laser component of claim 17 wherein a voltage to the electro-optic material is selected to minimize a reflection coefficient of the first grating and thereby control a wavelength of the resonator cavity.

20. A method for operating a waveguide laser comprising:

providing a waveguide laser resonater cavity having a plurality of reflection gratings at a first end for providing optical feedback to the cavity, wherein a first electro-optic cladding having a variable index of refraction is cladded to a first one of the plurality of the gratings;

injecting pump light into the waveguide laser resonator cavity; and

tuning the laser by selectively applying a first electrical potential to the first one of the grating claddings to selectively render the first grating reflective at a first wavelength that corresponds to a first longitudinal mode of the substrate waveguide cavity in order to tune the laser to the first wavelength.

21. The method of claim 20, wherein, the tuning further comprises selectively applying a second electrical potential to the first cladding to selectively render the first grating substantially transparent at a second wavelength that corresponds to a second longitudinal mode of the substrate waveguide cavity, wherein applying the second electrical potential renders the first grating substantially not reflective at the first wavelength, and wherein a second one of the plurality of gratings is reflective at the second wavelength in order to tune the laser to the second wavelength.

22. The method of claim 21, wherein, when reflective, the first one of the gratings reflects at a first wavelength, and when reflective, the second one of the gratings reflects at a second wavelength different from the first wavelength, and wherein the tuning further comprises applying an electrical potential to the second one of the grating claddings to selectively render the second grating reflective at a wavelength that corresponds to the second longitudinal mode of the substrate waveguide cavity.

23. The method of claim 20, wherein, when reflective, the first one of the gratings reflects at a first wavelength that is based in part on a first angle between the first grating and the waveguide laser resonator cavity, and when reflective, the second one of the gratings reflects at a second wavelength different from the first wavelength, the second wavelength based in part on a second angle between the second grating and the waveguide laser resonator cavity.

24. A laser comprising:

a glass substrate doped with a laser species;

a waveguide within the substrate forming a laser resonator cavity;

a pump coupled to the laser resonator cavity to excite the laser species in the waveguide;

a surface-relief grating formed over the waveguide on the substrate that selectively provides feedback to the laser resonator cavity;

an electro-optic cladding optically coupled to the grating on the substrate; and

electrodes that selectively apply an electric field to the electro-optic cladding to vary the index of refraction of the electro-optic cladding and thereby determine a characteristic wavelength of the laser resonator cavity.

25. The laser of claim 24 wherein the voltage to the electro-optic material is varied to vary a reflective wavelength of the grating.

26. The laser of claim 24 wherein the voltage to the electro-optic material is varied to maximize a reflection coefficient of the grating.

27. The laser of claim 24 wherein the voltage to the electro-optic material is varied to minimize a reflection coefficient of the grating.

28. The laser of claim 24 wherein the electro-optic cladding is located between the grating and the waveguide.

29. The laser of claim 24 wherein the grating is located between the electro-optic cladding and the waveguide.

30. A laser component comprising:

a glass substrate doped with a laser species and having a plurality of waveguides defined by channels within the substrate, each one of the plurality of waveguides forming a laser-resonator cavity with a distinct resonance characteristic to provide lasing action at a selected wavelength when pumped, wherein the substrate is an alkali phosphate glass doped with Er and Yb and wherein the channels are formed at a surface of the substrate as regions of increased refractive index, wherein each cavity includes a feedback element that provides optical feedback to form the laser-resonator, wherein injection of pump light at one or more suitable pump wavelengths into the laser-resonator cavity causes output of laser light at a wavelength in accordance with a longitudinal cavity mode of each cavity and wherein each one of the plurality of laser-resonator cavities lases at a different selected wavelength of a plurality of different wavelengths;

a ferrule having a plurality of spaced-apart attachment sites; and

a plurality of optic fibers attached to the ferrule, each optic fiber attached to its own attachment site wherein each attachment site corresponds to a different one of the cavities, wherein the number of optic fibers is fewer than the number of cavities such that each of the optic fibers is coupled to a corresponding one cavity selected from a plurality of possible cavities.

31. The laser component of claim 30, wherein the plurality of cavities are formed as a plurality of groups, each group including a plurality of cavities and corresponding to one of the plurality of otic fibers such that the plurality of optic fibers is aligned to the plurality of groups in order that either a first optic fiber is coupled to a first cavity of a first group and a second optic fiber is coupled to a first cavity of a second group, or the first optic fiber is coupled to a second cavity of the first group and the second optic fiber is coupled to a second cavity of the second group.

32. A method of making the laser component of claim 30, comprising:

forming the substrate such that a first plurality of waveguides each lase at a different wavelength selected from a first plurality of wavelengths and a second plurality of waveguides each lase at a different wavelength selected from a second plurality of wavelengths; and

aligning the ferrule such that a first laser wavelength is output to a first one of the plurality of optic fibers and a second laser wavelength different than the first laser wavelength is output to a second one of the plurality of optic fibers.

33. The laser component of claim 30, further comprising:

a pump light source; and

packaging enclosing the laser component.

34. The laser component of claim 30, further comprising:

a silicon oxide layer formed on a surface of the glass substrate, wherein the one or more feedback elements comprise a surface-relief diffraction grating formed into the silicon oxide layer and not into the substrate.

35. The laser component of claim 34, wherein the one or more feedback elements further comprise:

an electro-optic cladding optically coupled to the grating on the substrate; and

electrodes that selectively apply an electric field to the electro-optic cladding to vary the index of refraction of the electro-optic cladding and thereby determine a characteristic wavelength of the laser resonator cavity.

36. The laser component of claim 33, wherein the silicon oxide layer has a thickness in a range of between about 1000 nm and about 2000 nm.

37. The laser component of claim 30, wherein the feedback element comprises

a first surface-relief diffraction grating on the substrate waveguide that provides feedback to the resonator cavity;

an electro-optic material optically coupled to the first grating; and

electrodes that apply an electrical potential across the electro-optic material to vary an index of refraction in accordance therewith and thereby control a wavelength of the resonator cavity.

38. The laser component of claim 37 wherein a voltage to the electro-optic material is selected to maximize a reflection coefficient of the first grating and thereby control a wavelength of the resonator cavity.

39. The laser component of claim 37 wherein a voltage to the electro-optic material is selected to minimize a reflection coefficient of the first grating and thereby control a wavelength of the resonator cavity.

40. A laser component comprising:

a substrate doped with a laser species and having a plurality of laser cavities including a first cavity, each cavity providing lasing action at a selected wavelength when pumped;

a ferrule having a first laser-output fiber-attachment site; and

a first optic fiber attached to the ferrule at the first laser-output fiber-attachment site, wherein the ferrule is aligned to the substrate such that the first optic fiber is aligned to an output interface of the first cavity, wherein the first cavity is selected from a plurality of possible cavities that the first fiber could align to.

41. The laser component of claim 40, wherein the plurality of laser cavities further includes a second cavity, the ferrule further having a second laser-output fiber-attachment site, the component further comprising a second optic fiber attached to the ferrule at the second laser-output fiber-attachment site, wherein the ferrule is aligned to the substrate such that the second optic fiber is aligned to an output interface of the second cavity, wherein the second cavity is selected from a plurality of possible cavities that the second fiber could align to.

42. The laser component of claim 41, wherein the first laser cavity lases at a first wavelength, the second cavity lases at a second wavelength that is different than the first wavelength, wherein the substrate and ferrule are configured such that when the first optic fiber is aligned to the first cavity lasing at the first wavelength, the second optic fiber will be spaced to a cavity lasing at the second wavelength.

43. The laser component of claim 40, wherein the ferrule further includes a first pump-light site, and wherein the ferrule is aligned to the substrate such that the first optic fiber is aligned to an output interface of the first cavity and the first pump light site is aligned to a pump-light input interface of the first cavity.

44. The laser component of claim 40, wherein the plurality of laser cavities further includes a second cavity, the ferrule further having a second laser-output fiber-attachment site and a first and a second pump-light site, the component further comprising a second optic fiber attached to the ferrule at the second laser-output fiber-attachment site, wherein the ferrule is aligned to the substrate such that the second optic fiber is aligned to an output interface of the second cavity, and the first pump light site is aligned to a pump-light input interface of the first cavity and the second pump light site is aligned to a pump-light input interface of the second cavity, wherein the second cavity is selected from a plurality of possible cavities that the second fiber could align to.

45. A laser component comprising:

a substrate doped with a laser species and having a first cavity, the first cavity providing lasing action when pumped by suitable pump light;

a ferrule having a first pump-light site and a first laser-output fiber-attachment site; and

a first optic fiber attached to the ferrule at the first laser-output fiber-attachment site, wherein the ferrule is aligned to the substrate such that the first optic fiber is aligned to an output interface of the first cavity and the first pump light site is aligned to a pump-light input interface of the first cavity.

46. The laser component of claim 45, wherein the substrate further includes a second cavity, the ferrule further having a second pump-light site and a second laser-output fiber-attachment site, the component further comprising a second optic fiber attached to the ferrule at the second laser-output fiber-attachment site, wherein the ferrule is aligned to the substrate such that the second optic fiber is aligned to an output interface of the second cavity, and the second pump light site is aligned to a pump-light input interface of the second cavity.

47. The laser component of claim 46, wherein the output interface of the first cavity and of the second cavity and the pump-light input interface of the first cavity and of the second cavity are all located on a single surface of the substrate.

48. The laser component of claim 45, wherein the output interface of the first cavity and the pump-light input interface of the first cavity are both located on a single surface of the substrate.

49. The laser component of claim 45, wherein the first cavity comprises:

a first surface-relief diffraction grating on the substrate waveguide that provides feedback to the resonator cavity;

an electro-optic material optically coupled to the first grating; and

electrodes that apply an electrical potential across the electro-optic material to vary an index of refraction in accordance therewith and thereby control a wavelength of the resonator cavity.

50. The laser component of claim 45, wherein the first cavity comprises:

a silicon oxide layer formed on a surface of the glass substrate and a surface-relief diffraction grating formed into the silicon oxide layer and not into the substrate.

51. A method for making a laser component comprising:

providing a substrate having a first cavity doped with a laser species, the first cavity providing lasing action when pumped by suitable pump light;

providing a ferrule having an attached first optic fiber and an attached first pump-light source; and

aligning the ferrule to the substrate such that the first optic fiber is aligned to an output interface of the first cavity and the first pump-light source is aligned to a pump-light input interface of the first cavity.

52. The method of claim 51, wherein the substrate further includes a second cavity doped with a laser species, the second cavity providing lasing action when pumped by suitable pump light, and wherein the ferrule further includes an attached second optic fiber and an attached second pump-light source, and wherein the aligning of the ferrule to the substrate further comprises:

selecting between the first cavity and the second cavity based on a desired laser output characteristic; and

aligning the ferrule to the substrate such that the first optic fiber is aligned to an output interface of the second cavity and the second pump-light source is aligned to a pump-light input interface of the second cavity.

53. The method of claim 52, wherein the output interface of the second cavity and the pump-light input interface of the second cavity are both located on a single face of the substrate.

54. The method of claim 51, wherein the substrate further includes a second cavity doped with a laser species, the second cavity providing lasing action when pumped by suitable pump light, and wherein the ferrule further includes an attached second optic fiber and an attached second pump-light source, and wherein the aligning of the ferrule to the substrate further comprises:

selecting the first cavity and the second cavity from among a larger plurality of cavities based on a desired laser output characteristic; and

aligning the ferrule to the substrate such that the first optic fiber is aligned to an output interface of the first cavity and the first pump-light source is aligned to a pump-light input interface of the first cavity, and the second optic fiber is aligned to an output interface of the second cavity and the second pump-light source is aligned to a pump-light input interface of the second cavity.

55. The method of claim 51, wherein the attached first pump-light source comprises an optic fiber connectable to an external light source.

56. A method for making a laser component comprising:

providing a substrate having a first cavity doped with a laser species and a second cavity doped with a laser species, the first cavity providing lasing action when pumped by suitable pump light and the second cavity providing lasing action when pumped by suitable pump light;

providing a ferrule having an attached first optic fiber;

selecting between the first cavity and the second cavity based on a desired laser output characteristic; and

aligning the ferrule to the substrate such that the first optic fiber is aligned to an output interface of the selected first or second cavity.

57. The method of claim 56, wherein the substrate includes a plurality of cavities doped with a laser species including the first cavity, the second cavity, and a third cavity, and wherein the ferrule further includes an attached second optic fiber, and wherein the aligning of the ferrule to the substrate further comprises aligning the ferrule to the substrate such that the second optic fiber is aligned to an output interface of the third cavity when the first optic fiber is aligned to the output interface of the selected first or second cavity.

58. The method of claim 56, wherein the substrate includes a plurality of cavities doped with a laser species including the first cavity, the second cavity, and a third cavity, and wherein the ferrule further includes an attached second optic fiber, an attached first pump-light source, and an attached second pump-light source, and wherein the aligning of the ferrule to the substrate further comprises:

aligning the ferrule to the substrate such that the first optic fiber is aligned to an output interface of the first cavity and the first pump-light source is aligned to a pump-light input interface of the first cavity, and the second optic fiber is aligned to an output interface of the second cavity and the second pump-light source is aligned to a pump-light input interface of the second cavity.

59. The method of claim 58, wherein the attached first pump-light source comprises an optic fiber connectable to an external light source.

60. The method of claim 58, wherein the output interface of the second cavity and the pump-light input interface of the second cavity are both located on a single face of the substrate.