Polarization maintaining dispersion controlled fiber laser source of ultrashort pulses

• US 7,088,756 B2
• Filed: 07/25/2003
• Issued: 08/08/2006
• Est. Priority Date: 07/25/2003
• Status: Expired due to Fees

• Current Assignee: IMRA America Incorporated (Aisin Corp.)
• Original Assignee: IMRA America Incorporated (Aisin Corp.)
• Inventors: Cho, Gyu C., Fermann, Martin E.
• Primary Examiner(s): Harvey, Minsun Oh
• Assistant Examiner(s): FORDE, DELMA ROSA
• Application Number:
  US10/627,069
• Publication Number:
  US 20050018714A1
• Time in Patent Office: 1,110 Days
• Field of Search: 372/6, 372/18, 372/75, 372/98, 372/102, 372/45.013, 372/95
• US Class Current: 372/45.013
• CPC Class Codes: H01S 3/005 Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping shaping laser beam for working metal or other materials B23K26/06; optical elements, systems or apparatus in general G02B
• CPC Class Codes: H01S 3/06708 Constructional details of the fibre, e.g. compositions, cross-section, shape or tapering optical fibres as passive waveguides G02B6/02
• CPC Class Codes: H01S 3/06712 Polarising fibre; Polariser
• CPC Class Codes: H01S 3/094019 Side pumped fibre, whereby pump light is coupled laterally into the fibre via an optical component like a prism, or a grating, or via V-groove coupling
• CPC Class Codes: H01S 3/0941 of a laser diode
• CPC Class Codes: H01S 3/1055 one of the reflectors being constituted by a diffraction grating
• CPC Class Codes: H01S 3/1118 Semiconductor saturable absorbers, e.g. semiconductor saturable absorber mirrors [SESAMs]; Solid-state saturable absorbers, e.g. carbon nanotube [CNT] based

Abstract

A modelocked linear fiber laser cavity with enhanced pulse-width control includes concatenated sections of both polarization-maintaining and non-polarization-maintaining fibers. Apodized fiber Bragg gratings and integrated fiber polarizers are included in the cavity to assist in linearly polarizing the output of the cavity. Very short pulses with a large optical bandwidth are obtained by matching the dispersion value of the fiber Bragg grating to the inverse of the dispersion of the intra-cavity fiber.

Claims

1. A saturable absorber mirror for passive modelocking of lasers, comprising:

a film of a semiconductor material implanted with high energy ions at a penetration depth which differs from the penetration depth of optical signals reflected from said saturable absorber mirror, said semiconductor material having an ion implantation depth profile selected to provide saturable absorption having a multi-temporal carrier relaxation.

2. A saturable absorber mirror as defined in claim 1, wherein the thickness of said film is selected to be in the range of 50 nm–

2000 nm.

3. A saturable absorber mirror as defined in claim 1, wherein said high energy ions comprise protons, arsenic or beryllium.

4. A saturable absorber mirror as defined in claim 1, wherein the implantation dosage of said high energy ions is in a range of 10¹²–

10¹⁷ ions/cm².

6. A saturable absorber mirror as defined in claim 1, wherein said high energy ions comprise arsenic, and wherein the implantation energy is in the range of 100 keV–

1000 keV.

7. A saturable absorber mirror as defined in claim 1, where one surface of said mirror is anti-reflection-coated.

11. A saturable absorber mirror as defined in claim 1, wherein said semiconductor film comprises a bulk semiconductor.

12. A saturable absorber mirror as defined in claim 1, wherein said semiconductor film comprises a multiple quantum well structure.

13. A saturable absorber mirror as defined in claim 1, wherein said semiconductor film comprises a combination of a bulk semiconductor and a multiple quantum well structure.

17. A saturable absorber mirror as defined in claim 1, wherein said ion depth profile is selected to provide saturable absorption having a bi-temporal carrier relaxation.

18. A saturable absorber mirror as defined in claim 1, wherein said semiconductor material comprises GaAs related materials or InP related materials.

19. A saturable absorber mirror as defined in claim 1, wherein said saturable absorber mirror is electrodeless.

20. A saturable absorber mirror as defined in claim 1, wherein said film exhibits a depth-dependent ion concentration profile having a peak value and a minimal value.

21. A saturable absorber mirror as defined in claim 20, wherein the depth corresponding to said minimal value is at said penetration depth of optical signals.

22. A saturable absorber mirror as defined in claim 1, further comprising a heat sink disposed with respect to said film to sink heat therefrom.

5. A saturable absorber mirror as defined in 1, wherein said high energy ions comprise protons and wherein the implantation energy of said high energy ions is in the range of 5 keV–

200 keV.

8. A saturable absorber mirror for passive modelocking of lasers, comprising:

a film of a semiconductor material implanted with high energy ions at a penetration depth which differs from the penetration depth of optical signals reflected from said saturable absorber mirror, said film exhibiting multi-temporal relaxation,

wherein the thickness of said film controls the phase of the reflected light signal within opposite surfaces of said mirror.

23. A saturable absorber mirror as defined in claim 8, wherein said semiconductor material comprises GaAs related materials or InP related materials.

9. A saturable absorber mirror for passive modelocking of lasers, comprising:

a film of a semiconductor material implanted with high energy ions at a penetration depth which differs from the penetration depth of optical signals reflected from said saturable absorber mirror,

wherein said semiconductor material exhibits multi-temporal relaxation under optical excitation with short optical pulses.

10. A saturable absorber mirror as defined in claim 9, wherein a first relaxation time in said semiconductor film is less than 10 ps and a second relaxation time in said semiconductor film is greater than 100 ps.

24. A saturable absorber mirror as defined in claim 9, wherein said semiconductor material comprises GaAs related materials or InP related materials.

14. A saturable absorber mirror for passive modelocking of lasers, comprising:

a film of a semiconductor material implanted with high energy ions at a penetration depth which is smaller than the penetration depth of optical signals reflected from said saturable absorber mirror, said high energy ions creating a first trap concentration at a first depth region and a second trap concentration at a second depth region such that said film exhibits saturable absorption governed by a fast time constant and a slow time constant.

25. A saturable absorber mirror as defined in claim 14, wherein said semiconductor material comprises GaAs related materials or InP related materials.

26. A saturable absorber mirror as defined in claim 14, wherein said film exhibits bi-temporal carrier relaxation.

27. A saturable absorber mirror as defined in claim 14, wherein said saturable absorber mirror is electrodeless.

28. A saturable absorber mirror as defined in claim 14, wherein said film is anti-reflection-coated.

29. A saturable absorber mirror as defined in claim 14, wherein said fast time constant is less than 20 ps and said slow time constant is greater than 100 ps.

30. A saturable absorber mirror as defined in claim 14, wherein said fast time constant is less than 10 ps and said slow time constant is greater than 100 ps.

31. A saturable absorber mirror as defined in claim 14, wherein said fast time constant is less than 1 ps and said slow time constant is greater than 100 ps.

32. A saturable absorber mirror as defined in claim 14, wherein said first trap concentration at said first depth region is a peak value and said second trap concentration at said second depth region is a minimal value.

33. A saturable absorber mirror as defined in claim 32, wherein said peak value controls said fast time constant.

34. A saturable absorber mirror as defined in claim 32, wherein said minimal value controls said slow time constant.

35. A saturable absorber mirror as defined in claim 14, wherein said film is attached to a heat sink.

36. A saturable absorber mirror as defined in claim 35, wherein said heat sink comprises metal, diamond or sapphire.

37. A saturable absorber mirror as defined in claim 35, wherein said heat sink comprises a metallic mirror.

15. A saturable absorber to be operated in transmission for passive modelocking of lasers, comprising:

a film of a semiconductor material implanted with high energy ions at a penetration depth which is smaller than the thickness of said film such that said film exhibits multi-temporal relaxation.

38. A saturable absorber as defined in claim 15, wherein said film exhibits bi-temporal relaxation.

39. A saturable absorber as defined in claim 15, wherein said semiconductor material comprises GaAs related materials or InP related materials.

40. A saturable absorber as defined in claim 15, wherein said material is aluminum-free.

41. A saturable absorber as defined in claim 40, wherein said aluminum-free material comprises InGaAsP material.

42. A saturable absorber as defined in claim 15, wherein said material has a wavelength bandedge of approximately 1 micrometer.

43. A saturable absorber as defined in claim 15, wherein said material has a wavelength bandedge between 1.0 and 1.6 micrometers.

44. A saturable absorber as defined in claim 15, where one surface of said film is anti-reflection-coated.

45. A saturable absorber as defined in claim 15, wherein said saturable absorber is electrodeless.

16. A saturable absorber for passive modelocking of lasers operating in the 1.0–

1.1 um wavelength range, comprising;

a film of bulk InGaAsP or quantum wells fabricated with a bandgap in the 1.0–

1.1 um wavelength region, said film implanted with high energy ions at a penetration depth which differs from the penetration depth of optical signals, and said film exhibit multi-temporal relaxation.

46. A saturable absorber as defined in claim 16, wherein said film exhibits bi-temporal relaxation.

47. A saturable absorber as defined in claim 16, wherein a first relaxation time in said film is less than 10 ps and a second relaxation time in said film is greater than 100 ps.

48. A saturable absorber as defined in claim 16, wherein said film is anti-reflection-coated.

49. A saturable absorber as defined in claim 16, wherein said saturable absorber is electrodeless.

50. A saturable absorber as defined in claim 16, further comprising a heat sink.

51. A saturable absorber as defined in claim 16, further comprising a dielectric mirror.

52. A saturable absorber as defined in claim 16, further comprising a reflector comprising gold or silver.

53. A method of producing optical pulses, said method comprising directing light into a saturable absorber comprising a semiconductor material implanted with high energy ions at a penetration depth which is smaller than the penetration depth of said light directed into said saturable absorber, said high energy ions having a depth profile such said saturable absorber exhibits multi-temporal carrier relaxation.

54. A method of producing optical pulses as defined in claim 53, wherein said ion depth profile is such that said saturable absorber exhibits bi-temporal carrier relaxation.

55. A method of producing optical pulses as defined in claim 53, wherein said ion depth profile is such that said saturable absorber exhibits a first relaxation time less than 10 ps and a second relaxation time greater than 100 ps.

56. A method of producing optical pulses as defined in claim 53, wherein said saturable absorber is electrodeless.

57. A method of producing optical pulses as defined in claim 53, wherein said semiconductor material comprises GaAs related materials or InP related materials.

58. A method of manufacturing a saturable absorber, said method comprising implanting a semiconductor material with high energy ions at a penetration depth which is smaller than the thickness of said semiconductor material thereby creating a first trap concentration at a first depth region and a second trap concentration at a second depth region such that said semiconductor material exhibits saturable absorption governed by a first predetermined fast time constant and a second predetermined slow time constant.

59. A method of manufacturing a saturable absorber as in claim 58, said method further comprising implanting the semiconductor material such that said first predetermined fast time constant is less than 10 ps and said second predetermined slow time constant is greater than 100 ps.

60. A method of manufacturing a saturable absorber as in claim 58, wherein said step of implanting a semiconductor material with high energy ions further comprises providing an ion implantation depth profile selected to provide saturable absorption having a bi-temporal carrier relaxation.

61. A method of manufacturing a saturable absorber as in claim 58, said method further comprising providing a saturable absorber that is electrodeless.

62. A method of manufacturing a saturable absorber as in claim 58, said method further comprising providing said semiconductor material that comprises GaAs related materials or InP related materials.