Pulse stretching optical fiber and related systems and methods

• US 20090323735A1
• Filed: 06/26/2008
• Published: 12/31/2009
• Est. Priority Date: 06/26/2008
• Status: Active Grant

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Kuksenkov, Dmitri Vladislavovich, Li, Shenping, Wood, William Allen
• Granted Patent: US 7,817,681 B2
• Time in Patent Office: Days
• US Class Current: 372/6
• CPC Class Codes: G02B 6/03627 arranged - +
• CPC Class Codes: G02B 6/03644 arranged - + -
• CPC Class Codes: H01S 3/0057 Temporal shaping, e.g. pulse compression, frequency chirping soliton generation and propagation G02F1/3513, H01S3/063 and H01S3/108
• CPC Class Codes: H01S 3/067 Fibre lasers

Abstract

An optical fiber for performing pulse stretching, and fiber laser systems and methods using the pulse-stretching fiber are disclosed. The pulse-stretching (PS) fiber has low fourth-order dispersion (dispersion curvature) and a third order dispersion (dispersion slope) with a small negative, nearly zero or small positive value. Two different types of fiber laser systems that use the PS fiber in a manner that achieves optimum performance are described. The PS fiber enables an all-fiber (up to the final pulse compressor) ultra-short pulsed laser systems reaching pulse energies exceeding 100 μJ, average powers exceeding 100 W, and output pulse widths of less than 100 fs.

Claims

1. A pulse-stretching optical fiber (“

PS fiber”

) for temporally stretching optical pulses, comprising;

a segmented core having a central core region with a relative refractive index Δ

₁, an inner annular core region surrounding the central core region and having a relative refractive index Δ

₂ where Δ

₂<

Δ

₁, and an outer ring region surrounding the inner annular core region and having a relative refractive index Δ

₃ wherein Δ

₃>

Δ

₂;

a cladding region surrounding the segmented core and having a relative refractive Δ

₄ wherein Δ

₂<

Δ

₄<

Δ

₁, Δ

₃; and

a chromatic dispersion ≦

−

80 ps/nm/km, and a chromatic dispersion slope in the range between −

0.1 and 0 ps/nm²/km at a target wavelength λ

_T.

2. The optical fiber of claim 1, wherein the chromatic dispersion is in the range from −

125 to −

85 ps/nm/km.

3. The optical fiber of claim 1, wherein the target wavelength λ

_T is in the range 1030 nm≦

λ

_T≦

1100 nm.

4. The optical fiber of claim 1, having an effective area A_eff in the range 20 □

m²≦

A_eff≦

30 □

m².

5. The optical fiber of claim 1, having a length L₁₀ in the range 20 m≦

L₁₀≦

2000 m.

6. The optical fiber of claim 5, wherein length L₁₀ is such that the PS optical fiber operates to substantially compensate for chromatic dispersion characteristics of a pulse compressor.

7. A fiber laser, comprising:

a laser configured to provide input pulses having an input pulse width;

the PS fiber of claim 1 optically coupled to the laser, the PS fiber having a length L₁₀ sufficient to temporally stretch the input pulses to form stretched pulses;

a fiber amplifier optically coupled to the PS fiber and configured to receive and amplify the stretched pulses to form amplified stretched pulses;

a pulse compressor having dispersion characteristics and optically coupled to the fiber amplifier and configured to compress the amplified stretched pulses to form temporally compressed output pulses based on said dispersion characteristics; and

wherein the PS fiber length L₁₀, the negative chromatic dispersion and the chromatic dispersion slope operate to substantially compensate for the pulse compressor dispersion characteristics.

8. The fiber laser of claim 7, wherein the compressed output pulses have a pulse width W_O, the input pulses have a pulse width W_I, and wherein 0.05W_I≦

W_O≦

2W_I.

9. The fiber laser of claim 7, wherein:

the input pulses are substantially transform limited and have a pulse width in the range from about 0.1 ps to about 3 ps, and a pulse energy in the range from about 0.1 nJ to 1.0 nJ; and

the output pulse width is less than 500 fs.

10. The fiber laser of claim 7, wherein the laser is a stretched-pulse mode-locked laser.

11. The fiber laser of claim 10, wherein the laser generates chirped input pulses having a substantially linear phase change with time.

12. The fiber laser of claim 7, wherein the input pulses have a width of between 1 ps and 5 ps.

13. The fiber laser of claim 7, further including a self-similar amplifier disposed between the laser and the PS fiber and configured to form parabolic pulses from the input pulses prior to forming said stretched pulses.

14. The fiber laser of claim 13, wherein the parabolic pulses has a pulse width larger than 3 ps.

15. The fiber laser of claim 13, wherein the parabolic pulses have a linear and negative chirp.

16. The fiber laser of claim 7, wherein the laser generates input pulses that are substantially transform limited and that have an energy in the range from 0.1 to 1 nJ.

17. The fiber laser of claim 13, wherein the self-similar amplifier includes a length of amplifying optical fiber having normal (negative) dispersion of ≦

−

10 ps/nm/km.

18. The fiber laser of claim 17, wherein the amplifying optical fiber has a core effective area A_eff such that 20 μ

m≦

A_eff≦

100 μ

m².

19. The fiber laser of claim 13, wherein the self-similar amplifier has a gain G such that 6 dB≦

G≦

23 dB.

20. A method of forming ultra-short high-energy output pulses from a fiber laser, comprising:

generating substantially transform-limited input pulses each having an input pulse width W_I;

passing the input pulses through a length of pulse-stretching (PS) fiber having a segmented core configured to provide at target wavelength a negative chromatic dispersion of ≦

−

80 ps/nm/km, and a chromatic dispersion slope in the range between −

0.1 and 0.0 ps/nm²/km so as to stretch the input pulses by at least a factor of 10; and

compressing the stretched input pulses to form output pulses each having a pulse width W_O, wherein 0.05W_I≦

W_O≦

2W_I.

21. The method of claim 20, including generating the input pulses with a stretched-pulse mode-locked laser.

22. The method of claim 21, including passing the input pulses through a self-similar amplifier prior to said stretching so as to form parabolic pulses having a substantially linear and negative chirp.

23. A method of forming temporally stretched optical pulses, comprising:

providing input pulses; and

passing the input pulses through a length L₁₀ of pulse-stretching (PS) fiber wherein 20 m≦

L₁₀≦

2000 m, the PS fiber having a segmented core that provides the PS fiber at a target wavelength with a negative chromatic dispersion in the range from −

125 to −

85 ps/nm/km, and a chromatic dispersion slope in the range between −

0.1 and 0.0 ps/nm²/km so as to form said temporally stretched optical pulses.

24. The method of claim 23, including selecting the PS fiber length L₁₀ such that the negative chromatic dispersion and the chromatic dispersion slope operate to substantially compensate for chromatic dispersion characteristics of a pulse compressor used to compress the temporally stretched optical pulses.

25. The method of claim 23, wherein the input pulses have a pulse width, and wherein the temporally stretched pulses have a pulse width between 10 times to 2000 times greater than the input pulse width.