Chirped pulse fiber amplifier

• US 20090128892A1
• Filed: 04/14/2006
• Published: 05/21/2009
• Est. Priority Date: 04/14/2005
• Status: Active Grant

• Current Assignee: Cornell University
• Original Assignee: Cornell University
• Inventors: Zhou, Shian, Kuznetsova, Lyuba, Wise, Frank W., Chong, Chin Yu
• Granted Patent: US 8,107,161 B2
• Time in Patent Office: Days
• US Class Current: 359/341.100
• 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 3/06725 Fibre characterized by a specific dispersion, e.g. for pulse shaping in soliton lasers or for dispersion compensating [DCF]
• CPC Class Codes: H01S 3/06754 Fibre amplifiers H01S3/06708 takes precedence
• CPC Class Codes: H01S 3/06791 Fibre ring lasers fibre laser gyrometers G01C19/72
• CPC Class Codes: H01S 3/1618 ytterbium

Abstract

A short-pulse fiber amplifier system (10) is designed so that nonlinear phase shifts and third-order dispersion are purposely introduced that compensate each other. In particular, the nonlinear phase shift accumulated in the amplifier is compensated by the third-order dispersion of the combination of a fiber stretcher (12) and a grating compressor (16). In the presence of third-order dispersion, an optimal nonlinear phase shift reduces the pulse duration, and enhances the peak power and pulse contrast compared to the pulse produced in linear propagation.

Claims

1. A fiber amplifier system, comprising:

a source of optical pulses;

a pulse stretcher connected to said source for receiving said pulses and generating a plurality of broadened optical pulses;

a fiber amplifier connected to said pulse stretcher for receiving said broadened optical pulses from said pulse stretcher and generating a plurality of amplified pulses; and

,

a pulse compressor connected to said fiber amplifier for receiving said amplified pulses received from said fiber amplifier and generating a plurality of compressed amplified pulses;

wherein, said pulse stretcher and said pulse compressor are selected to have dispersion characteristics that are mismatched with one another to thereby introduce an amount of third order dispersion into the system and said system is further designed to introduce an amount of nonlinear phase shift to a pulse as it travels through said system, said amounts of third order dispersion and nonlinear phase shift being sufficient to compensate for one another and thereby produce pulses of short duration and high peak power.

2. The system of claim 1, wherein said stretcher is a segment of optical fiber

3. The system of claim 2, wherein said compressor is a dispersive delay line.

4. The system of claim 3, wherein said dispersive delay line comprises a pair of diffraction gratings.

5. The system of claim 1, wherein said amounts of third order dispersion and said nonlinear phase shift are selected to minimize the width of said output pulses and thereby maximize a value of peak power in said pulses.

6. The system of claim 5, wherein said system is designed to impart a nonlinear phase shift magnitude of at least π

to said pulses.

7. The system of claim 6, wherein said system is designed such that the relationship of the magnitude of nonlinear phase shift, Φ

^NL, is related to the third order dispersion (TOD) approximately by the formula;

|TOD|=|T·

GVD−

0.14Φ

^NL·

T²|, where GVD is the net group velocity dispersion of the system and T is the interval of the pulse.

8. The system of claim 1, wherein said fiber amplifier includes a first section of fiber that is doped to produce gain and a second section of single mode fiber that provides an amount of nonlinear phase shift in said system.

9. A method of compensating for nonlinear phase shifts in short-pulse fiber amplifiers, comprising:

providing a pulse fiber amplifier system including a source of optical pulses, a pulse stretcher connected to said source, a pulse fiber amplifier connected to pulse stretcher and a pulse compressor connected to said pus amplifier;

selecting said pulse stretcher and said pulse compressor to have dispersion characteristics that are mismatched to one another and thereby introduce an amount of third order dispersion into said system; and

selecting said pulse fiber amplifier to introduce a controllable amount of nonlinear phase shift into said system that is sufficient to compensate for said third order dispersions; and

adjusting the amount of linear phase shift introduced by said pulse fiber amplifier to produce pulses of short duration and high peak power.

10. The method of claim 9, wherein said stretcher is selected to be a segment of optical fiber

11. The method of claim 10, wherein said compressor is selected to be a dispersive delay line.

12. The method of claim 11, wherein said dispersive delay line is selected to be a pair of diffraction gratings.

13. The method of claim 9, wherein said amount of nonlinear phase shift introduced by said fiber amplifier is adjusted to minimize the width of said output pulses and thereby maximize a value of peak power in said pulses.

14. The method of claim 13, where said phase shift is adjusted by adjusting an amount of pump power applied to sad amplifier.

15. The method of claim 13, wherein said system is designed to impart a nonlinear phase shift magnitude of at least π

to said pulses.

16. The method of claim 15, wherein said system is designed such that the relationship of the magnitude of nonlinear phase shift, Φ

^NL, is related to the third order dispersion (TOD) approximately by the formula;

|TOD|=|T·

GVD−

0.14Φ

^NL·

T²|, where GVD is the net group velocity dispersion of the system and T is the interval of the pulse.

17. The method of claim 9, wherein said fiber amplifier is selected to include a first section of fiber that is doped to produce gain and a second section of single mode fiber that introduces an amount of nonlinear phase shift in said system.