Resonant fabry-perot semiconductor saturable absorbers and two photon absorption power limiters

• US 6,252,892 B1
• Filed: 09/08/1998
• Issued: 06/26/2001
• Est. Priority Date: 09/08/1998
• Status: Expired due to Term

• Current Assignee: IMRA America Incorporated (Aisin Corp.)
• Original Assignee: IMRA America Incorporated (Aisin Corp.)
• Inventors: Harter, Donald J., Fermann, Martin E., Sucha, Gregg D., Jiang, Min
• Primary Examiner(s): Arroyo, Teresa M.
• Assistant Examiner(s): ZAHN, JEFFREY N
• Application Number:
  US09/149,368
• Time in Patent Office: 1,022 Days
• Field of Search: 372/18, 372/11, 372/10, 372/6
• US Class Current: 372/11
• CPC Class Codes: G02F 1/3523 Non-linear absorption changing by light, e.g. bleaching
• CPC Class Codes: H01S 3/067 Fibre lasers
• CPC Class Codes: H01S 3/08059 Constructional details of the reflector, e.g. shape mirrors in general G02B5/08; mountings for mirrors G02B7/18
• CPC Class Codes: H01S 3/094003 the pumped medium being a fibre
• CPC Class Codes: H01S 3/1063 using a solid state device provided with at least one potential jump barrier
• 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
• CPC Class Codes: H01S 3/1608 erbium

Abstract

An intracavity resonant Fabry-Perot saturable absorber (R-FPSA) induces modelocking in a laser such as a fiber laser. An optical limiter such as a two photon absorber (TPA) can be used in conjunction with the R-FPSA, so that Q-switching is inhibited, resulting in laser output that is cw modelocked. By using both an R-FPSA and a TPA, the Q-switched modelocked behavior of a fiber laser is observed to evolve into cw modelocking.

Claims

1. A Mode-locked laser, comprising:

a gain medium;

first and second reflectors disposed on opposite ends of said gain medium to form an optical cavity;

a third reflector disposed within said cavity and spaced from said first reflector to form a Fabry-Perot etalon which is near resonance at the laser frequency; and

a saturable absorber having nonlinear absorption characteristics and inducing mode-locked laser pulses, said absorber located within said Fabry-Perot etalon.

2. The laser of claim 1, further comprising a Q-switching suppressor.

3. The laser of claim 2, wherein said Q-switching suppressor comprises a two photon absorber (TPA) disposed within said cavity.

4. The laser of claim 3, wherein said TPA is distributed within said cavity.

5. The laser of claim 3, wherein said TPA is self-defocusing.

6. The laser of claim 3, wherein said TPA is disposed on said saturable absorber.

7. The laser of claim 3, wherein said TPA adjoins said first reflector.

8. The laser of claim 3, wherein said TPA comprises a material selected from the group of InP, InGaAs, GaAs, InGaAsP, ZnS, CdSe, CdS, CdTe, AlAs and AlGaAs.

9. The laser of claim 1, further comprising a protector which guards said saturable absorber from optically induced damage.

10. The laser of claim 9, wherein said protector comprises a two photon absorber (TPA) disposed within said cavity.

11. The laser of claim 10, wherein said TPA comprises a material selected from the group of InP, InGaAs, GaAs, InGaAsP, ZnS, CdSe, CdS, CdTe, AlAs and AlGaAs.

12. The laser of claim 1, additionally comprising a polarization drift compensator disposed within said cavity.

13. The laser of claim 1, wherein said saturable absorber is disposed between said first reflector and said third reflector.

14. The laser of claim 1, wherein said saturable absorber is distributed within said cavity.

15. The laser of claim 1, wherein said Fabry-Perot etalon is tunable.

16. The laser of claim 1, wherein said Fabry-Perot etalon comprises a monolithic structure.

17. The laser of claim 16, wherein said monolithic structure comprises a distributed bragg reflector overlying a semiconductor substrate.

18. The laser of claim 17, wherein said monolithic structure further comprises:

a TPA adjoining said distributed bragg reflector; and

said saturable absorber adjoining said TPA.

19. The laser of claim 1, wherein said Fabry-Perot etalon has a free spectral range which is large compared with the bandwidth of said mode-locked laser pulses.

20. The laser of claim 1, wherein the bandwidth of resonance of said Fabry-Perot etalon is broader than the gain bandwidth of said laser.

21. The laser of claim 1, wherein said saturable absorber comprises InGaAsP.

22. A mode-locked laser, comprising:

a gain medium;

first and second reflectors disposed on opposite ends of said gain, medium to form an optical cavity; and

a resonant Fabry-Perot saturable absorber (R-FPSA) disposed within said cavity, said R-FPSA having nonlinear aborption characteristics and inducing mode-locked laser pulses.

23. The laser of claim 22, further comprising a Q-switching suppressor.

24. The laser of claim 23, wherein said Q-switching suppressor comprises a two photon absorber (TPA) disposed within said cavity.

25. The laser of claim 24, wherein said TPA is distributed within said cavity.

26. The laser of claim 24, wherein said TPA is self-defocusing.

27. The laser of claim 24, wherein said TPA is disposed on said R-FPSA.

28. The laser of claim 24, wherein said TPA adjoins said first reflector.

29. The laser of claim 24, wherein said TPA comprises InP.

30. The laser of claim 22, further comprising a protector which guards said R-FPSA from optically induced damage.

31. The laser of claim 30, wherein said protector comprises a two photon absorber (TPA) disposed within said cavity.

32. The laser of claim 31, wherein said TPA comprises InP.

33. The laser of claim 22, additionally comprising a polarization drift compensator disposed within said cavity.

34. The laser of claim 22, wherein said R-FPSA comprises a saturable absorber disposed between said first reflector and a partial reflector.

35. The laser of claim 22, wherein said R-FPSA comprises a saturable absorber which is distributed within said cavity.

36. The laser of claim 22, wherein said R-FPSA is tunable.

37. The laser of claim 22, wherein said R-FPSA comprises a monolithic structure.

38. The laser of claim 37, wherein said monolithic structure comprises a distributed bragg reflector overlying a semiconductor substrate.

39. The laser of claim 38, wherein said monolithic structure further comprises:

a TPA adjoining said distributed bragg reflector; and

a saturable absorber adjoining said TPA.

40. The laser of claim 22, wherein said R-FPSA has a free spectral range which is large compared with the bandwidth of said mode-locked laser pulses.

41. The laser of claim 22, wherein the bandwidth of resonance of said R-FPSA is broader than the gain bandwidth of said laser.

42. The laser of claim 22, wherein said R-FPSA comprises InGaAsP.

43. A mode-locked laser, comprising:

an optical cavity including a gain medium;

a Fabry-Perot etalon within said cavity which is near resonance at the laser frequency; and

a saturable absorber having nonlinear absorption characteristics and inducing mode-locked laser pulses, said absorber located within said Fabry-Perot etalon.