Method of designing optical pulse shaping device and optical pulse shaping device

• US 7,483,608 B2
• Filed: 03/17/2005
• Issued: 01/27/2009
• Est. Priority Date: 03/19/2004
• Status: Active Grant

• Current Assignee: Furukawa Electric Company Limited
• Original Assignee: Furukawa Electric Company Limited
• Inventors: Inoue, Takashi, Namiki, Shu
• Primary Examiner(s): Connelly-Cushwa; Michelle R.
• Assistant Examiner(s): CHU, CHRIS H
• Application Number:
  US10/593,340
• Publication Number:
  US 20070280613A1
• Time in Patent Office: 1,412 Days
• Field of Search: 385/122
• US Class Current: 385/122
• CPC Class Codes: G02F 1/365 in an optical waveguide structure G02F1/377, G02F1/395 take precedence
• CPC Class Codes: G02F 2203/26 Pulse shaping; Apparatus or methods therefor
• CPC Class Codes: G02F 2203/54 Optical pulse train (comb) synthesizer

Abstract

The present invention provides a method for designing an optical pulse shaper including a first optical propagation line unit having a nonlinear medium and a dispersion medium concatenated, including: specifying design specifications of the first optical propagation line unit; and based on the design specification, calculating a quasi-periodic stationary pulse of which a waveform of an input optical pulse to the first optical propagation line unit is similar to a waveform of an output pulse from the first optical propagation line unit.

Claims

1. A method for designing an optical pulse shaper including a first optical propagation line unit having a nonlinear medium and a dispersion medium concatenated, comprising:

specifying design specifications of the first optical propagation line unit; and

based on the design specification, calculating a quasi-periodic stationary pulse of which a waveform of an input optical pulse to the first optical propagation line unit is similar to a waveform of an output pulse from the first optical propagation line unit.

2. The method of claim 1, wherein a second or a second and later optical propagation line units are subsequently concatenated to the first optical propagation line unit.

3. The method of claim 2, further comprising:

specifying design specifications of the second or the second and later optical propagation line units.

4. The method of any one of claims 1 to 3, wherein the design specifications include at least a nonlinear coefficient, a dispersion value and a length in a light propagation direction of each of the nonlinear medium and the dispersion medium of each of the optical propagation line units and a power peak of the input optical pulse.

5. The method of claim 4, wherein provided that generalized dispersion values of the nonlinear medium and the dispersion medium included in the first optical propagation line unit are s₁ and s₂, respectively, and normalized lengths of the nonlinear medium and the dispersion medium are K₁ and L₁, respectively, s₂ is a value of anomalous dispersion and satisfies a following equation and the values of K₁ and L₁ satisfy a following equation:

0≦

|s₁|<

<

1<

<

s₂

L₁<

<

K₁

in which |s₁|is an absolute value of s₁.

6. The method of claim 5, wherein provided that generalized dispersion values of the nonlinear medium and the dispersion medium included in the nth optical propagation line unit (n is a positive integer equal to or more than 2) counting from the optical propagation line unit among the optical propagation line units are s_1nand s_2n, respectively, and normalized lengths of the nonlinear medium and the dispersion medium are K_nand L_n, respectively, s_2n is a value of anomalous dispersion and satisfies a following equation and the values of K_n and L_n satisfy following equations:

s_1n=s₁/α

<sup>n−

1</sup>

s_2n=s₂/α

<sup>n−

1</sup>

K_n=K₁/α

<sup>n−

1</sup>

L_n=L₁/α

<sup>n−

1</sup>

α

;

a compression ratio.

7. The method of claim 5, wherein provided that generalized dispersion values of the nonlinear medium and the dispersion medium included in the nth optical propagation line unit (n is a positive integer equal to or more than 2) counting from the optical propagation line unit among the optical propagation line units are s_1nand s_2n, respectively, and normalized lengths of the nonlinear medium and the dispersion medium are K_n and L_n , respectively, s_2nis a value of anomalous dispersion and satisfies a following equation and the values of K_n and L_n satisfy following equations:

s_1ns₁/α

<sup>n−

1</sup>

s_1n=s₂

K_n=K₁/α

<sup>n−

1</sup>

L_n=L₁α

<sup>2(n−

1)</sup>

α

;

a compression ratio.

8. The method of claim 1, wherein the input optical pulse is an optical pulse having a waveform close to a waveform of the quasi-periodic stationary pulse.

9. The method of claim 1, wherein provided that the nonlinear coefficient and a loss coefficient of the nonlinear medium are ν

and δ

respectively, the nonlinear medium is a highly nonlinear medium with the values of ν and

δ

satisfying a following equation;

z=−

(½

δ

)ln(1−

2δ

/a₀²ν

)ζ

z;

a total length in the light propagation direction of the nonlinear medium in the optical pulse shaper, expressed by a real distance

ζ

;

a total length in the light propagation direction of the nonlinear medium in the optical pulse shaper, expressed by a normalized distance of dimensionless amount

a₀;

a power attenuation coefficient of an input end of an optical pulse of the nonlinear medium

ln;

logarithm natural.

10. The method of claim 1, wherein the nonlinear medium is a highly nonlinear optical fiber and the dispersion medium is a single mode optical fiber.

11. An optical pulse shaper designed based on the method of claim 1.

12. The optical pulse shaper of claim 11, wherein a nonlinear phase shift amount of a pulse generated per step is O(1).

13. The optical pulse shaper of claim 11, wherein the length of the nonlinear medium is set in consideration of a propagation loss of the nonlinear medium and the dispersion medium and a connection loss including a connection loss of different media.

14. The optical pulse shaper of claim 11, wherein an optical amplifier is inserted at a given portion so as to compensate power loss due to a propagation loss of the nonlinear medium and the dispersion medium and a connection loss including a connection loss of different media.

15. The optical pulse shaper of claim 11, wherein a pulse light source, an optical amplifier and a band pass filter are sequentially concatenated to reduce a noise in input light.

16. The optical pulse shaper of claim 11, wherein two members each having a DFB laser diode, an optical amplifier and a band pass filter sequentially concatenated are used to generate beat light and the beat light is input the optical pulse shaper.

17. The optical pulse shaper of claim 11, wherein a polarization-maintaining fiber is used.

18. The optical pulse shaper of claim 11, wherein used as the nonlinear medium is a photonic crystal fiber.

19. The optical pulse shaper of claim 11, wherein used as the dispersion medium is a fiber Bragg grating.

20. The optical pulse shaper of claim 11, wherein used as the dispersion medium is a high-order mode fiber.

21. A pulse outputting device comprising the optical pulse shaper of claim 11.

22. A laser machining device comprising the optical pulse shaper of claim 11.

23. A measurement device comprising the optical pulse shaper of claim 11.

24. An optical sampling oscilloscope comprising the optical pulse shaper of claim 11.