JP2002006149A - Optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To propagate a high power laser beam and radiate a laser beam having a small diffusion angle. SOLUTION: An optical fiber comprises a core element 5 having a large diffraction index and a clad part 6 which is formed in the circumference of the core part 5 and has a smaller diffraction index than that of the core part 5. In addition, the amount of impurities contained in the clad part 6, which lower the diffraction index, becomes smaller gradually from the incidence side to the radiation side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber for transmitting a laser beam so as to irradiate a laser beam to an object to be processed.

[0002]

2. Description of the Related Art A conventional optical fiber used for laser processing extends from a laser oscillator for generating a laser beam to a laser emitting portion, and as shown in FIG.
And a cladding part 2 formed around the core part 1.

The core portion 1 is formed of pure quartz and has a high refractive index. The cladding portion 2 contains a predetermined ratio of impurities for lowering the refractive index with respect to silicon tetrachloride glass. Has a refractive index slightly smaller than the refractive index of the core 1.

When a laser beam is propagated through an optical fiber, the laser beam is incident on a core 1 on the optical fiber incident side from a lens 3 adjacent to a laser oscillator (not shown), and propagates inside the core 1. By doing so, the light is emitted from the emission side to the laser emission part.

Here, when the laser light propagating inside the core portion 1 travels to the boundary surface 4 between the core portion 1 and the clad portion 2, the angle (diffusion angle) of the laser light with respect to the boundary surface 4 becomes larger. If the angle is within the propagation angle determined by the ratio of the refractive index of 1 to the cladding part 2, the light is totally reflected.

[0006]

However, when the laser beam used for laser processing has a large output when the laser beam is to be propagated, the spatial coherence of the high-output laser beam is poor, so that the propagation angle is small. It is necessary to use an optical fiber having a large diameter, and there is a problem that fine laser processing cannot be performed. On the other hand, when an optical fiber having a small propagation angle is used so that fine laser processing can be performed, as shown in FIG. 2, laser light having a large diffusion angle leaks intensively from the incident side of the cladding portion 2 of the optical fiber. There was a problem that burnout occurred in the part.

The optical fiber of the present invention has been made in view of the above-mentioned circumstances, and has an object to propagate a high-power laser beam and emit a laser beam having a small diffusion angle.

[0008]

An optical fiber according to the present invention is an optical fiber comprising a core having a high refractive index and a cladding formed around the core and having a refractive index smaller than the core. The clad portion contains impurities that lower the refractive index so as to gradually decrease from the incident side toward the emission side.

[0009] The incident side of the clad portion contains an impurity which lowers the refractive index at such a rate that the laser light does not leak intensively even when a high-output laser light is incident.

Further, the impurity which lowers the refractive index may be fluorine.

When a large-power laser beam having a large diffusion angle is incident from the incident side, the ratio of impurities that reduce the refractive index is large on the incident side of the clad portion. Large laser light is also reflected at the interface between the core and the cladding, and when high-power laser light propagates through the core, the proportion of impurities that lower the refractive index is emitted from the incident side of the cladding. By gradually decreasing toward the side, the laser light having a large diffusion angle is gradually emitted to the outside with propagation, and the laser light having a small diffusion angle is emitted on the emission side.

As described above, if the cladding portion contains the impurity that lowers the refractive index so as to gradually decrease from the incident side to the outgoing side, even if a large output laser beam is input, the laser Does not leak intensively on the incident side of the cladding part and gradually allows laser light with a large diffusion angle to escape to the outside, so that high-power laser light propagates from the incident side and is emitted with a small diffusion angle. As a result, fine laser processing can be performed with high-power laser light.

Further, when the incident side of the cladding contains an impurity which lowers the refractive index at such a rate that the laser beam does not leak intensively even when the laser beam with a large output is incident, the laser beam with a large output is surely provided. Since the light is reflected on the incident side of the clad portion, it is possible to prevent the occurrence of burning.

Furthermore, if the impurity which lowers the refractive index is fluorine, the refractive index of the cladding containing fluorine is reduced at a desired ratio, so that a high-power laser beam can be surely propagated from the incident side and the diffusion angle can be increased. Can be emitted.

[0015]

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

FIG. 1 shows an example of an optical fiber according to the present invention.

The optical fiber extends from a laser oscillator for generating a laser beam to a laser emitting portion, and as shown in FIG.
It is composed of a linear core part 5 and a clad part 6 formed around the core part 5.

Here, the core portion 5 is made of pure quartz and has a high refractive index, and the cladding portion 6 is made of silicon tetrachloride glass with at least one of fluorine and boron as impurities for lowering the refractive index. Is contained at a predetermined ratio on the incident side, the amount of impurities is gradually reduced from the incident side to the output side, and is contained at a predetermined ratio on the output side.
In addition, it is preferable that the emission side contains an impurity that reduces the refractive index at substantially the same ratio as in the conventional example.

A protective material (not shown) is provided around the clad portion 6, and the protective material is provided with cooling means (not shown) for circulating water for cooling.

The operation of the embodiment of the present invention will be described below.

When a high-power laser beam having a large diffusion angle is incident from the incident side via the lens 7, the diffusion angle is increased due to a large proportion of impurities that lower the refractive index on the incident side of the clad portion 6. Not only small laser light but also large laser light is reflected at the boundary surface 8 between the core portion 5 and the clad portion 6.

Subsequently, when the laser light reflected on the boundary surface 8 propagates through the core portion 5, the ratio of impurities that lower the refractive index gradually decreases from the incident side to the emission side of the clad portion 6. As a result, laser light having a large diffusion angle is made to gradually escape to the outside as it propagates, and laser light having a small diffusion angle is emitted on the emission side. When the laser light incident from the incident side does not have a large output, the laser light propagates normally and is emitted.

As described above, when the clad portion 6 contains the impurity for lowering the refractive index so as to gradually decrease from the incident side to the emission side, even if a large output laser beam is input, the Since the light does not leak intensively on the incident side of the clad portion 6, the laser light having a large diffusion angle gradually escapes to the outside, so that the high-power laser light propagates from the incident side and has a small diffusion angle. The laser beam is emitted, and as a result, fine laser processing can be performed with high-power laser light.

If the incident side of the cladding portion 6 contains an impurity which lowers the refractive index at such a rate that the laser beam does not leak intensively even when the laser beam with a high output is incident, the laser beam with a high output can be ensured. Since the light is reflected by the boundary surface 8 on the incident side of the clad portion 6, the occurrence of burning can be prevented.

Further, if the impurity which lowers the refractive index is fluorine, the refractive index of the fluorine-containing clad portion 6 is reduced at a desired ratio, so that a high-power laser beam can be surely propagated from the incident side and diffused. A laser beam with a small angle can be emitted.

Incidentally, the optical fiber of the present invention is not limited to the above-described embodiment. If the refractive index of the clad is changed as desired, the impurities may be not only fluorine but also other substances. It goes without saying that various changes can be made without departing from the spirit of the present invention.

[0027]

According to the optical fiber of the present invention, various excellent effects as described below can be obtained.

I) If the cladding portion contains an impurity which lowers the refractive index so as to gradually decrease from the incident side to the outgoing side, the laser light can be applied even when a large output laser beam is input. The laser beam with a large diffusion angle is allowed to gradually escape to the outside without leaking intensively on the entrance side of the part, so that high-power laser light propagates from the entrance side and is emitted with a small diffusion angle. As a result, fine laser processing can be performed with high-power laser light.

II) If the incident side of the cladding contains an impurity that lowers the refractive index at such a rate that the laser light does not leak intensively even when the laser light with a high output power is incident, the laser light with a high output power is surely obtained. Since the light is reflected on the incident side of the clad portion, it is possible to prevent the occurrence of burning.

III) If fluorine is used as the impurity for lowering the refractive index, the refractive index of the fluorine-containing clad portion is reduced at a desired ratio. Can be emitted.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of an embodiment of an optical fiber of the present invention.

FIG. 2 is a conceptual diagram showing an example of a conventional optical fiber.

[Explanation of symbols]

 5 Core 6 Cladding

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Akihiro Nishimi 3-1-1-15 Toyosu, Koto-ku, Tokyo Ishikawajima Harima Heavy Industries, Ltd. Tokyo Engineering Center (72) Inventor Minoru Uehara 3-1-1 Toyosu, Koto-ku, Tokyo No. 15 Ishikawajima Harima Heavy Industries, Ltd. Tokyo Engineering Center (72) Inventor Yoshihisa Yamauchi 3-1-1, Toyosu, Koto-ku, Tokyo Ishikawajima Harima Heavy Industries, Ltd. Tokyo Engineering Center F-term (reference) 2H037 AA04 BA03 CA05 2H050 AB10Y AC03 AC82 4E068 CD01 CE08

Claims (3)

[Claims] 1. An optical fiber comprising a core having a high refractive index and a clad formed around the core and having a refractive index smaller than the core, wherein the clad lowers the refractive index. An optical fiber, characterized by containing impurities to be gradually reduced from an incident side to an emission side. 2. The optical fiber according to claim 1, wherein the incident side of the clad portion contains an impurity for lowering the refractive index at such a rate that the laser light does not leak intensively even when a high-power laser light is incident. 3. The optical fiber according to claim 1, wherein the impurity that reduces the refractive index is fluorine.