MODULAR, HIGH ENERGY, WIDELY-TUNABLE ULTRAFAST FIBER SOURCE

• US 20100046067A1
• Filed: 10/29/2009
• Published: 02/25/2010
• Est. Priority Date: 05/23/2000
• Status: Active Grant

• Current Assignee: IMRA America Incorporated (Aisin Corp.)
• Original Assignee: IMRA America Incorporated (Aisin Corp.)
• Inventors: HARTER, Donald J., FERMANN, Martin E., GALVANAUSKAS, Almantas
• Granted Patent: US 8,072,678 B2
• Time in Patent Office: Days
• US Class Current: 359/341.310
• 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 3/0675 Resonators including a grating structure, e.g. distributed Bragg reflectors [DBR] or distributed feedback [DFB] fibre lasers
• CPC Class Codes: H01S 3/06754 Fibre amplifiers H01S3/06708 takes precedence
• 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 3/094042 of a fibre laser
• CPC Class Codes: H01S 3/109 Frequency multiplication, e.g. harmonic generation
• CPC Class Codes: H01S 3/1112 Passive mode locking
• CPC Class Codes: H01S 3/1115 using intracavity saturable absorbers
• CPC Class Codes: H01S 3/1616 thulium
• CPC Class Codes: H01S 3/1618 ytterbium
• CPC Class Codes: H01S 3/302 in an optical fibre

Abstract

A modular, compact and widely tunable laser system for the efficient generation of high peak and high average power ultrashort pulses. Modularity is ensured by the implementation of interchangeable amplifier components. System compactness is ensured by employing efficient fiber amplifiers, directly or indirectly pumped by diode lasers. Peak power handling capability of the fiber amplifiers is expanded by using optimized pulse shapes, as well as dispersively broadened pulses. Dispersive broadening is introduced by dispersive pulse stretching in the presence of self-phase modulation and gain, resulting in the formation of high-power parabolic pulses. In addition, dispersive broadening is also introduced by simple fiber delay lines or chirped fiber gratings, resulting in a further increase of the energy handling ability of the fiber amplifiers. The phase of the pulses in the dispersive delay line is controlled to quartic order by the use of fibers with varying amounts of waveguide dispersion or by controlling the chirp of the fiber gratings. After amplification, the dispersively stretched pulses can be re-compressed to nearly their bandwidth limit by the implementation of another set of dispersive delay lines. To ensure a wide tunability of the whole system, Raman-shifting of the compact sources of ultrashort pulses in conjunction with frequency-conversion in nonlinear optical crystals can be implemented, or an Anti-Stokes fiber in conjunction with fiber amplifiers and Raman-shifters are used. A particularly compact implementation of the whole system uses fiber oscillators in conjunction with fiber amplifiers. Additionally, long, distributed, positive dispersion optical amplifiers are used to improve transmission characteristics of an optical communication system. Finally, an optical communication system utilizes a Raman amplifier fiber pumped by a train of Raman-shifted, wavelength-tunable pump pulses, to thereby amplify an optical signal which counterpropogates within the Raman amplifier fiber with respect to the pump pulses.

Claims

1. A fiber based chirped pulse amplification system generating output pulses in the range of 1-1.15 μ

m, comprising;

a seed source comprising a passively modelocked Yb;

fiber laser;

a Yb;

fiber amplifier for amplifying an output of said fiber laser;

a pulse stretcher which receives said pulses from said seed source, dispersively stretches said pulses in time, and outputs said stretched pulses to said fiber amplifier;

an optical modulator disposed between said passively modelocked fiber laser and said Yb;

amplifier, said modulator being controllable to reduce the repetition rate of pulses injected into said Yb;

amplifier and to increase the available pulse energy of pulses amplified with said Yb;

amplifier; and

a pulse compressor which inputs said amplified stretched pulses and temporally compresses them to approximately their bandwidth limit.

2. The fiber chirped pulse amplification system according to claim 1, wherein said passively modelocked fiber laser is polarization maintaining.

3. The fiber chirped pulse amplification system according to claim 1, wherein said passively modelocked fiber laser is single-mode and polarization maintaining.

4. The fiber chirped pulse amplification system according to claim 1, wherein said Yb:

amplifier is cladding-pumped.

5. The fiber chirped pulse amplification system according to claim 1, further comprising:

a coupler between the seed source and the fiber amplifier, which couples the seed source to the fiber amplifier, and which further comprises an optical fiber with a length less than 1 km.

6. The fiber chirped pulse amplification system according to claim 1, further comprising:

an optical delivery fiber coupled to the output of the fiber amplifier.

7. The fiber chirped pulse amplification system according to claim 1, wherein said optical delivery fiber comprise one or more of a holey fiber, a length of few-moded fiber and a length of few-moded fiber spliced together with one or two lengths of single-mode fiber.

8. The fiber chirped pulse amplification system according to claim 1, wherein said pulse stretcher comprises a fiber with a length less than 1 km.

9. The fiber chirped pulse amplification system according to claim 1, wherein said pulse stretcher comprises a holey fiber.

10. The fiber chirped pulse amplification system according to claim 1, wherein said pulse stretcher comprises a length of few-moded fiber.

11. The fiber chirped pulse amplification system according to claim 1, wherein said pulse stretcher comprises a length of few-moded fiber spliced together with one or more lengths of single-mode fiber.

12. The fiber chirped pulse amplification system according to claim 1, wherein said pulse stretcher comprises a single-mode fiber with a length less than 1 km.

13. The fiber chirped pulse amplification system according to claim 1, wherein said pulse stretcher comprises a fiber with a W refractive index profile.

14. The fiber chirped pulse amplification system according to claim 1, wherein said pulse stretcher comprises a fiber with a multi-clad refractive index profile.

15. The fiber chirped pulse amplification system according to claim 1, wherein said pulse stretcher comprises:

a length of fiber with negative 3^rd order dispersion; and

a linearly chirped fiber grating with negative 2^nd order dispersion.

16. An optical pulse source comprising:

a seed source generating output pulses in the range of 1-1.15 μ

m;

a large gain Yb;

non-linear fiber amplifier having a core diameter in the range from about 1 μ

m to 50 μ

m, said amplifier configured in such a way that the fundamental mode is excited and propagates in said Yb;

amplifier, said Yb;

amplifier generating amplified pulses.

17. The optical pulse source according to claim 16, wherein said non-linear amplifier generates parabolic pulses.

18. An optical pulse source comprising:

a Yb;

seed laser;

a Yb;

fiber amplifier having a core diameter in the range from about 1 μ

m to 50 μ

m, and configured in such a way that the fundamental mode is excited and propagates in said Yb;

amplifier, said Yb;

amplifier generating amplified pulses.

19. The optical pulse source according to claim 18, further comprising:

an optical modulator disposed between said Yb;

seed laser and said Yb;

fiber amplifier, said modulator being controllable to reduce the repetition rate of pulses injected into said Yb;

amplifier and to increase the available pulse energy of pulses amplified with said Yb;

amplifier.