Method of Designing Optical Pulse Shaping Device and Optical Pulse Shaping Device

• US 20070280613A1
• Filed: 03/17/2005
• Published: 12/06/2007
• 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
• Granted Patent: US 7,483,608 B2
• Time in Patent Office: Days
• 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_1n and s_2n, respectively, and normalized lengths of the nonlinear medium and the dispersion medium are K_n and 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_1n and s_2n, respectively, and normalized lengths of the nonlinear medium and the dispersion medium are K_n and 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
K_n=K₁/α

<sup>n−

1</sup>
L_n=L₁/α

²⁽n−

1)

a;

a compression ratio

8. ] The method of any one of claims 1 to 7, 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 any one of claims 1 to 8, 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=−

(1/2δ

)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 any one of claims 1 to 9, 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 any one of claims 1 to 10.

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 any one of claims 11 to 17, wherein used as the nonlinear medium is a photonic crystal fiber.

19. ] The optical pulse shaper of any one of claims 11 to 17, wherein used as the dispersion medium is a fiber Bragg grating.

20. ] The optical pulse shaper of any one of claims 11 to 17, wherein used as the dispersion medium is a high-order mode fiber.

21. ] A pulse outputting device comprising the optical pulse shaper of any one of claims 11 to 20.

22. ] A laser machining device comprising the optical pulse shaper of any one of claims 11 to 20.

23. ] A measurement device comprising the optical pulse shaper of any one of claims 11 to 20.

24. ] An optical sampling oscilloscope comprising the optical pulse shaper of any one of claims 11 to 20.