JP2002055239A - Photonic crystal fiber and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a filter realizing an optical fiber amplifier having very high efficiency and excellent in a noise characteristic and realizing an optical fiber laser. SOLUTION: In a photonic crystal fiber 1 having a multi-hole part 12 in which a large number of small holes 12a extending in the central axis direction of the fiber are arranged with highest density and a core pat 11 which is formed in a solid shape at the center of the multi-hole part 12, a functional material (for example, Er) which improves a light amplifying action or a nonlinear optical effect is doped in the core part 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photonic crystal fiber comprising a porous portion having a large number of pores extending in the central axis direction of a fiber, and a solid core formed at the center of the porous portion. About.

[0002]

2. Description of the Related Art Conventionally, for example, erbium (Er) or the like is used as an optical fiber for improving conversion efficiency (efficiency), which is a ratio between an excitation input and an amplified signal output in an optical fiber amplifier, and noise characteristics. Rare earth element doped optical fibers doped with rare earth elements are known.

[0003]

However, in ordinary optical fibers such as the above-mentioned rare earth element-doped optical fibers, the mode field diameter is larger than the core diameter, that is, the optical power density in the core is not sufficiently high. There are inconveniences. For this reason, in the optical fiber amplifier using the rare earth element-doped optical fiber, there is a limit in the improvement of the efficiency and the noise characteristics, and there is a disadvantage in that it cannot reach a sufficient level. This inconvenience also occurs for laser oscillation in an optical fiber laser. Further, not only rare earth element-doped optical fiber but also fiber Raman amplification causes the above-mentioned inconvenience.

[0004] The present invention has been made in view of such circumstances, and an object of the present invention is to provide an optical fiber amplifier and an optical fiber laser which are extremely efficient and have excellent noise characteristics. Is to do.

[0005]

In order to achieve the above-mentioned object, the present invention provides a photonic crystal which has recently attracted attention as a material exhibiting a large chromatic dispersion which cannot be obtained with an optical fiber comprising a core and a clad. It was completed by focusing on the fiber. That is,
The photonic crystal fiber includes a porous portion having a large number of pores extending in a central axis direction of the fiber, and a solid or hollow core portion formed at the center of the porous portion. Has an extremely high optical power density. Therefore, if the solid core is doped with a functional material that enhances the optical amplification or nonlinear optical effect, a fiber that can realize an optical fiber amplifier and an optical fiber laser with extremely high efficiency and excellent noise characteristics can be obtained. The present invention has been completed by focusing on the points.

Specifically, the invention according to claim 1 comprises a porous portion having a large number of pores extending in the central axis direction of the fiber;
A photonic crystal fiber including a solid core formed at the center of the porous portion.

[0007] It is a specific matter that the core is doped with a functional material that enhances an optical amplification effect or a nonlinear optical effect.

[0008] The functional material is as described in claim 2,
A rare earth element may be used to improve the light amplification effect using stimulated emission. Specifically, the rare earth element may be at least one of erbium (Er), neodymium (Nd), and ytterbium (Yb).

[0009] Further, the functional material may include:
As described, germanium (Ge) or phosphorus (P) may be used, and a large amount of Ge or P may be doped into the core to improve the light amplification effect using stimulated Raman scattering. .

Further, by doping semiconductor particles of selenium (Se) or cadmium sulfide (CdS), supersaturation absorption and four-wave mixing may be easily generated.

According to the invention described in claims 1 to 4,
Since the photonic crystal fiber has a high optical power density in the core, the efficiency is greatly improved by doping the core with a functional material that enhances the optical amplification or nonlinear optical effect.

As a result, when the photonic crystal fiber is used for an optical fiber amplifier, amplification of an optical signal with extremely high efficiency and low noise is realized, and the pump input (threshold) required for a positive gain is also obtained. descend. Also,
Even if the photonic crystal fiber is used for a fiber laser, extremely high efficiency and low noise laser oscillation can be realized as described above.

The invention according to claim 5 relates to a method for manufacturing a photonic crystal fiber, and more specifically, a porous portion having a large number of pores extending in the central axis direction of the fiber, and the porous portion. And a method for manufacturing a photonic crystal fiber having a solid core portion at the center of the photonic crystal fiber.

[0014] A plurality of cylindrical capillaries serving as the pores are filled in the holes of the cylindrical support tube, and a functional material for enhancing the light amplifying function or the non-linear optical effect serving as the core part is previously prepared. A preform producing step of producing a preform by disposing a doped rod-shaped core member at the center of the support tube, and a drawing step of heating and stretching the preform to draw a fiber. This is a specific matter.

Here, the photonic crystal fiber may be made of, for example, quartz (SiO ₂ ). That is, the support tube, the capillary and the core member are made of SiO ₂
It may be made.

As a method of pre-doping a rod-shaped core member serving as a solid core portion with a functional material that enhances an optical amplification effect or a non-linear optical effect, for example, VAD (Va
A soot made of a SiO ₂ composition doped with a functional material is formed by a por-phase axial deposition method or the like, and the soot is dehydrated and sintered to produce a core member doped with a functional material. You may.

The rod-shaped core member may be doped with a functional material by, for example, ion implantation (ion implantation), or the surface of the rod-shaped core member may be doped with a functional material by ion diffusion. .

Further, the functional material may be doped by, for example, immersion.

According to the fifth aspect of the present invention, a preform is manufactured using a rod-shaped core member doped with a functional material that enhances an optical amplification effect or a nonlinear optical effect in advance, and the preform is drawn. A photonic crystal fiber in which a core is doped with a functional material is easily manufactured.

On the other hand, the invention according to claim 6 provides a photonic comprising a porous portion having a large number of pores extending in the central axis direction of a fiber, and a solid core portion formed at the center of the porous portion. It is intended for the manufacturing method of crystal fiber.

A preform manufacturing step of manufacturing a preform in which a plurality of holes serving as the pores and a solid portion provided at the center of the plurality of hole groups serving as the core are formed; A drawing step of heating and stretching the preform to draw a fiber, and after the drawing step,
A doping step of doping a functional material that enhances an optical amplification effect or a non-linear optical effect into the solid portion by ion implantation or ion diffusion is specified.

Here, the functional material may be driven in the longitudinal or radial direction of the fiber.

In the preform manufacturing step, the preform may be manufactured by filling a cylindrical capillary and a rod-shaped core member into the hole of the cylindrical support tube, or may be formed at the center of the cylindrical body. May be used as a solid part which becomes a core after fiberization, and a preform may be produced by forming a large number of through holes which become pores after fiberization around the solid part. Also, a preform may be produced by bundling a cylindrical capillary around a rod-shaped core member in a close-packed state and fusing and integrating the adjacent capillaries with each other and the core member and the capillary. Good.

According to the present invention, the functional material is doped into the core (solid portion) of the photonic crystal fiber manufactured by drawing the preform by ion implantation or ion diffusion. Thereby, a photonic crystal fiber in which a functional material is doped in a core portion is easily manufactured.

When the photonic crystal fiber is used for an optical fiber amplifier, a functional material may be doped only in a part of the core in the longitudinal direction of the fiber.

[0026]

As described above, according to the photonic crystal fiber of the present invention, the efficiency can be greatly improved by doping the core with a functional material that enhances the optical amplification or nonlinear optical effect. Can be.

As a result, when the photonic crystal fiber is used for an optical fiber amplifier, it is possible to realize extremely high efficiency and low noise amplification of an optical signal, and to lower the threshold value. Even when the photonic crystal fiber is used for a fiber laser, extremely high efficiency and low noise laser oscillation can be realized in the same manner as described above.

Further, according to the method for manufacturing a photonic crystal fiber of the present invention, a photonic crystal fiber having a core doped with a functional material can be easily manufactured.

[0029]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a photonic crystal fiber 1 according to an embodiment of the present invention. The photonic crystal fiber 1 has a core portion 11 extending in the center axis direction of the fiber center and formed in a solid state. The porous portion 12 is provided so as to surround the outer peripheral portion of the core portion 11, and has a plurality of fine pores 12 a extending along the core portion 11, arranged in a close-packed manner.
And a support portion 13 provided to cover these
And

The core portion 11 is doped with a functional material that enhances the optical amplification action, specifically, a rare earth element, more specifically, activated Er.

A method for manufacturing the photonic crystal fiber 1 will be described with reference to FIG.

First, a support tube 2 in which a hole 2a having a regular hexagonal cross section is provided along the central axis at the center of a cylindrical body made of SiO ₂ , and a plurality of cylindrical SiO ₂ tubes having the same diameter as each other. A capillary 3 and one rod-shaped SiO ₂ core member 4 having the same diameter as the capillaries 3 are prepared.

The core member 4 is doped with Er. The core member 4 doped with Er in this manner may be manufactured by, for example, a VAD method. That is, SiC
The organic compounds containing l ₄ and Er is supplied to the oxyhydrogen burner, the flame hydrolysis reaction and the oxidation reaction to form a soot of SiO ₂ composition Er doped (deposition of glass particles). Then, the soot may be dehydrated and sintered (and stretched) in a chlorine atmosphere to form the core member 4.

The method of manufacturing the Er-doped core member 4 is not limited to the method described above. For example, OVD (Outs
ide Vapor Deposition method and MCVD (Modified Chemi
A soot consisting of a SiO ₂ composition doped with Er may be formed by a calvaper deposition method.

Further, as a method for manufacturing a core member 4 which Er is doped, for example, to respect SiO ₂ made of bar-like core member 4 may be doped with Er by ion implantation, the rod-shaped made of the SiO ₂ The surface of the core member 4 may be doped with Er by ion diffusion.

Further, the rod-shaped core member 4 is immersed in the liquid by immersion.
You may make it dope r.

Then, the capillary 3 is filled in the regular hexagonal hole 2a of the support tube 2 in the closest density. At this time, the first layer is formed by arranging the capillaries 3 in parallel with one surface of the inner wall of the regular hexagonal hole 2a, and a pair of adjacent capillaries 3 in the formed first layer is formed. , 3 to form a new second layer. By repeating such mounting of the capillary 3, the capillary 3 is filled in the regular hexagonal hole 2 a in the closest density, but the center position of the regular hexagonal hole 2 a is not a core 3 but a core member. 4 is arranged.

Through the above steps, the preform 5 of the photonic crystal fiber 1 in which the capillaries 3 are filled in the regular hexagonal holes 2a of the support tube 2 in a close-packed manner and the core member 4 is disposed at the center thereof is obtained. Complete.

The preform 5 is subjected to a drawing process for heating and melting to reduce the diameter (to form a fiber). At the time of this drawing process, the adjacent capillaries 3 and 3, the capillary 3 and the support tube 2, and the capillary 3 and the core member 4 are fused and integrated.

Through the above steps, as shown in FIG. 1, the core portion 11 extends in the center axis direction at the center of the fiber and is formed solid, and the outer periphery of the core portion 11 is formed along the core portion 11. A photonic crystal fiber 1 having a porous portion 12 in which a large number of extending pores 12a are arranged in a close-packed manner and a support portion 13 covering these, and in which the core portion 11 is doped with Er, is completed.

Next, the operation and effect of the above embodiment will be described.

Since the photonic crystal fiber 1 has a high optical power density in the core portion 11, the core portion 11 is doped with Er, which is a functional material that enhances the light amplifying effect, so that the efficiency is greatly improved. Can be.

As a result, if the photonic crystal fiber 1 is used for an optical fiber amplifier, it is possible to realize extremely high efficiency and low noise amplification of an optical signal and to lower the threshold value. Also, even when the photonic crystal fiber 1 is used for a fiber laser, extremely high efficiency and low noise laser oscillation can be realized in the same manner as described above.

<Modification> The method of manufacturing the photonic crystal fiber 1 in which the core portion 11 is doped with Er is not limited to the above, and may be, for example, as follows.

That is, as described above, the support tube 2
The preform 5 is produced by filling the capillary 3 and the core member 4 in the regular hexagonal hole 2a in the closest density (preform production step). At this time, the core member 4
Is used without being doped with Er.

Next, the preform 5 is heated and drawn into a fiber shape (drawing step).

After the drawing step, the core portion 11 is doped with Er by performing ion implantation or ion diffusion in the longitudinal direction or the radial direction of the fiber. Thus, a photonic crystal fiber in which the core portion 11 is doped with Er can be manufactured.

The preform is manufactured by, for example, forming a central portion of a cylindrical body made of SiO ₂ into a solid portion which becomes the core portion 11 after forming the fiber, and forming a thin portion around the solid portion after forming the fiber. A preform may be manufactured by forming a through-hole serving as the hole 12a.

Further, a number of cylindrical capillaries 3 are bundled around the rod-shaped core member 4 so as to be in the closest packing state, and the adjacent capillaries 3, 3 and the core member 4 and the capillary 3 are fused and integrated. A preform may be produced by causing the preform. That is, the photonic crystal fiber according to the present invention may not include the support portion 13.

<Other Embodiments> The present invention is not limited to the above-described embodiments, but includes various other embodiments. That is, in the above-described embodiment, Er is used as the functional material that enhances the optical amplification effect, and the activated Er is doped into the core portion 11. However, the present invention is not limited to this. For example, activated Nd or The core 11 may be doped with other rare earth elements such as Yb.

Further, for example, by doping a large amount of Ge or P into the core portion 11, the optical amplification effect may be improved by utilizing stimulated Raman scattering. Also, S
By doping the core portion 11 with semiconductor fine particles of e or CdS, saturable absorption and four-wave mixing may be easily generated.

Further, the core 11 may be co-doped with not only Er but also Al, for example. Further, Er, Ge and Al may be co-doped,
And Yb may be co-doped.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a photonic crystal fiber.

FIG. 2 is a sectional view showing a preform of the photonic crystal fiber.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photonic crystal fiber 2 Support tube 3 Capillary 4 Core member 5 Preform 11 Core part 12 Porous part 13 Support part 12a Pores

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H01S 3/10 H01S 3/10 Z (72) Inventor Masatoshi Tanaka 4-3 Ikejiri, Itami-shi, Hyogo Mitsubishi Cable Industries, Ltd. Inside Itami Works (72) Inventor Moriyuki Fujita 4-3 Ikejiri, Itami-shi, Hyogo Mitsubishi Cable Industries, Ltd. Inside Itami Works (72) Inventor Toshikazu Gozen 4-3-3, Ikejiri, Itami-shi, Hyogo Mitsubishi Cable Industries Itami Works (72) Inventor Kazuo Imamura 4-3 Ikejiri, Itami-shi, Hyogo Mitsubishi Electric Cable Industry Co., Ltd.Itami Works (72) Inventor Masataka Nakazawa 2-3-1, Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Hirokazu Kubota 2-3-1 Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Satoru Kawanishi 2-3-1 Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Co., Ltd. F-term (reference) 2H050 AB0 1Z AB05X AB08X AB18X 2K002 AB12 AB30 CA16 DA10 DA20 HA23 HA31 5F072 AB07 AK06 JJ02 JJ05 QQ07 YY17

Claims (6)

[Claims] 1. A photonic crystal fiber comprising: a porous portion having a large number of pores extending in a central axis direction of a fiber; and a solid core portion formed at the center of the porous portion. A photonic crystal fiber, wherein the portion is doped with a functional material that enhances an optical amplification effect or a nonlinear optical effect. 2. The photonic crystal fiber according to claim 1, wherein the functional material is a rare earth element. 3. The rare earth element according to claim 2, wherein the rare earth element is erbium (Er), neodymium (Nd).
And at least one of ytterbium (Yb). 4. The photonic crystal fiber according to claim 1, wherein the functional material is germanium (Ge) or phosphorus (P), selenium (Se), or cadmium sulfide (CdS). 5. A method for manufacturing a photonic crystal fiber comprising: a porous portion having a large number of pores extending in a central axis direction of a fiber; and a solid core portion formed at the center of the porous portion. A cylindrical support tube, in which a plurality of cylindrical capillaries serving as the pores are filled, and the core portion is a rod-shaped core pre-doped with a functional material that enhances an optical amplification effect or a nonlinear optical effect; A preform manufacturing step of manufacturing a preform by disposing a member at the center of the support tube; and a drawing step of heating and stretching the preform to draw a fiber. Of manufacturing photonic crystal fiber. 6. A method for manufacturing a photonic crystal fiber comprising: a porous portion having a large number of pores extending in a central axis direction of a fiber; and a solid core portion formed at the center of the porous portion. A preform producing step of producing a preform in which a plurality of holes serving as the pores and a solid portion provided at the center of the plurality of hole groups serving as the core are formed; A drawing step of heating and stretching to draw a fiber, and after the drawing step, a doping step of doping by ion implantation or ion diffusion a functional material that enhances the optical amplification or nonlinear optical effect in the solid portion. A method for producing a photonic crystal fiber, comprising: