JPS5918904A - Optical fiber having metallic film - Google Patents

Abstract

PURPOSE:To obtain a flexible optical fiber suited for guiding of laser light having high energy by providing a specific metallic film on the inside wall of a glass tube, forming a hollow fiber and using the same for transmission of energy. CONSTITUTION:An optical fiber is hollow, and dry air or the like is fed into a hollow part 1. A metallic film 2 consisting of at least one kind of metals selected from Au, Ni, Ag, Cu is formed on the inside wall of the tube 3. Transmitting energy is transmitted in the part 1 and are propagated while reflecting on the film 2. The optical fiber having such structure has about 0.5-3mm. outside diameter and 0.2-1.5mm. inside diameter, and since the fiber is hollow, it is highly flexible. The reflection loss from both end faces of the optical fiber is too large to be negligible with a dielectric optical fiber (e.g.; KRS-5), and the reflected light thereof is fed back to the laser and can be a cause for disturbance of the oscillation. In the case of metal, however, the most of energy propagates in the hollow part; therefore, there is virtually no loss by feflection. Since the light energy passes the hollow part, it is possible to make high output laser light incident to such fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an infrared transmitting optical fiber in which a metal thin film is formed on the inner wall surface of a hollow optical fiber using an electroless plating solution, in particular for guiding high-energy laser light. This invention relates to a flexible optical fiber suitable for.

In recent years, in addition to silica glass optical fibers, non-silica optical fibers have been studied as ultra-low loss optical fibers for wavelengths of 2 to 3 μm or as energy guide paths for CO2 lasers with wavelengths of 10.6 μm. As these non-quartz materials, 1) heavy metal oxide glass, 2) halide crystal or glass, and 2) chalcogenide glass are considered.

Specific examples of heavy metal oxide glass include GeO2 glass (015hansky, R, and 5cher).
er, o, w, .

”High GeO20ptical Wavegui
des,” 5 thEurope4n Conference
ence on QpticaICorrmunica
tion 12.55ept, 1979), TeO2 glass (Boniort et al., nfr2r
ed Qlass Optical Fibers fo
r 4 and 10 MicroBands”, 5
th European Conference o
nQpt 1cal Communication,
pp, 61-64.5ept.

1980) are known.

As a halide, KR, S-5 crystal (TIBr-
TII) (8, Sakuragi etal, ”
Infrared Transmission Capa
bilities of 'ph211iumHali
de and 5ilLler Hal ide Qp
ticalFibers”, American Cer.
amic 5occity 82nd Annual
Meeting (Checago), April, 19
80 or Y, MimUra et al.”
Growth of piber Cuystals f
or Infrared QpticalWavegu
ide”, Japanese Journal of
Applied pHysics, vol, 19. no,
5. pp, L269-L272゜MaY1980), G
dF3-BaFz-ZrF4 glass (Mitachi et al., "Preparation of Fluoride Optical Fiber", "Proceedings of the 1985 National Conference of the Optical and Radio Division of the Institute of Electronics and Communication Engineers", No. 360.p.
360. September 1980) is being studied.

- Also, as chalcogenide glass, AS2S3 glass (N, S, Kapany et al., "R
development in Inf
rared l;"1ber Qptics,":[n
Frared Physics, vol, 5. p
p, 69-80.

1965), G e P S Glass (S, 5
hibata etaL” G e -P-8Cha
Icogenide Glassspibers,”
Japanese Journal of Appli
edpHysics, vol, 19. no, 10.
pp, L603-■, 605, Oct, 198
0) is known.

Now, since the above-mentioned non-quartz material is transparent at a wavelength of 2 μm or more, it generally has a characteristic of having a low melting point or softening point. These optical fibers propagate the transmitted light energy through a dielectric medium. For these, 20W, 10
In order to transmit light with a high energy such as 0W, it is necessary to remove impurities contained in the material through thermal destruction based on light absorption. When the light intensity in a trenched optical fiber increases, stimulated Raman scattering in the direction opposite to the direction of light propagation occurs due to the interaction between light and sound waves based on the nonlinear optical effect of the material, even if it does not lead to so-called destruction. Since stimulated Brillouin scattering occurs, the energy of the transmitted light is correspondingly reduced, and the energy transmission capacity is reduced. The low-loss silica-based optical fiber "C" has a power output of 100 W/mm2 under continuous oscillation and a wavelength of 1.06 cm of Nd-YAG laser light.
Only moderate values have been demonstrated. In order to achieve flexibility in normal optical fibers, the diameter of the optical fiber must be 1 inch or less, and for example, if the diameter is 1 cylinder, the limit for transmitting optical energy of approximately 80 W is This means that it is close to . As mentioned above, in conventionally developed optical fibers, the energy strength of the optical fiber,
There were drawbacks such as limited transmission capacity due to power tolerance and thermal breakdown based on light absorption.

-Also 1.06 μn such as Nd-YAG laser
] and CO2 laser, which have a wavelength of 1086 μm, are invisible to the naked eye, so in order to irradiate the target area with laser light, it is necessary to separately guide a visible light laser such as a He-Ne laser. is necessary.

However, conventional infrared transmitting optical fibers, especially optical fibers for 10.6 μm, have a drawback in that they cannot transmit light of 0.633 μm.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical fiber that can stably transmit high optical energy by avoiding the above-mentioned drawbacks, namely, the limitations on transmittable energy and the wavelength of light to be transmitted.

Conventionally, as a light guide path for transmitting high optical energy -C;
However, in addition to optical fibers, a light guide path using a mirror used in a laser scalpel is also available. This device transmits light energy through space, so there are no problems with heat generation or longevity, but since it uses a mirror to bend the light, it has the drawbacks of lack of flexibility and a large light guide path. The present invention combines the flexibility of an optical fiber and the ability to transmit optical energy through spatial propagation of the light guide. The optical fiber of the present invention will be explained using the drawings. FIG. 1 is a cross-sectional view of the optical fiber of the present invention.

The optical fiber is hollow, and dry air or the like is sent to the hollow part 1. AU on the inner wall of the glass tube 3.

A metal film 2 of Ni, Ag, Cu, etc. is formed.

The transmitted energy is transmitted through the hollow part 1 and propagated while being reflected by the metal film 2. Optical fibers with these structures have an outer diameter of 0
．． Although it has an inner diameter of about 5 to 3 mJI+ and an inner diameter of about 0.2 to 1.5 mJI, it is highly flexible because it is hollow.

The refractive index of metals, except for some, is expressed by complex numbers, and absorption loss is greater than that of dielectric materials. There are various modes that transmit in a metal waveguide, but considering the TE mode here, its absorption coefficient αpq is approximately expressed by the following equation. Here the suffix p.

q indicates the mode order of the propagation mode.

However, a: Radius of the waveguide λ: Wavelength of light R: Bending radius of the waveguide S: Complex refractive index of metal - n-jk (r+: exorbitant part, k: imaginary part) Llpq
: A constant related to the propagation constant of each mode, which is the root of the Bessel function.

The double refractive index of metals generally becomes like a first order at a light wavelength of 10.6 μm.

Table 1 Complex refractive index of metal The second term on the right side of equation (1) indicates the increase in bending loss when the waveguide is bent by radius R.

Here, the case of silver Ag will be explained as an example. Substituting the double refractive index into equation (2), in the case of a waveguide with a radius of 400 μm, αo1 = 1.4 for the TE ol mode.
X 10-3 (1+3.23/R2) (m-')
(3) is obtained. From this, in a metal waveguide with a radius of 400 μrn, even if the bending radius R is 10 crn, it is still 1 m.
When α0-0.45, the transmission loss is about 63%, which is very small compared to a CO2 laser light guide path using a conventional optical fiber. In addition, if the bending radius R is 1 m, α0-5, 9
X 10-3, and the transmission loss can be ignored. The above numerical considerations can also be applied to, for example, He--Ne laser light with a wavelength of 0.63 μm. Since the double refractive index of dAg at 0.63 μm is approximately given by n = 0.19-j4.3, in the case of a waveguide with a radius of 400 μm similar to the above, α11 = 5.5 Xi O-'. transmission is possible. As mentioned above, a waveguide with a metal film has the great feature of being able to transmit even visible light.

In a dielectric optical fiber such as KR8-5, the reflection loss from both end faces of the optical fiber is so large that it cannot be ignored.

For example, in KRS-5, there is 28% reflection from both end faces. This reflected light returns to the laser and becomes a cause of disturbing oscillation. However, in the case of metal, most of the energy propagates through the hollow space, so it can be said that there is almost no loss due to reflection.

-Also, since the light energy passes through the hollow part, high power laser light can be incident.

The present invention will be explained in detail below.

2ooo quartz glass tubes with a diameter of 5m+n and an inner diameter of 4m+n
A hollow optical fiber with a diameter of 1.2 mm and an inner diameter of 0.8 mm was obtained by drawing at a high temperature of c. A mixture of tin chloride and palladium as the main components was injected into the hollow glass tube using a compression pump, and the surface was treated with a plating treatment. After that, the Nl electroless plating solution N1-801 manufactured by Koujun Kagaku Kenkyu Shin was applied again. It was press-fitted using a compression pump. The plating solution is constantly moving. The optical fiber was kept at a temperature of 75C, and after 2 hours Ni-801
After the plating liquid was removed, the inner surface of the quartz glass tube had a thickness of 10 mm.
A high-purity nickel film with a thickness of μm was laminated. In addition, the company's Ag
When electroless Metsugi solution S-900 was injected and held at 80C for 3 hours, a 10 μm thick silver film was deposited.

Output 1 to a 1m long quartz optical fiber with this metal film
When 00 W of 10.6 μm light was incident, a light output of approximately 40% was obtained. This transmission loss is caused by heavy scattering from the metal surface, so when this optical fiber was inserted into an electric furnace at about 1000C and fire polished, the transmittance was 60%.
It was found that it can be used as an optical fiber for laser scalpel.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a hollow optical fiber of the present invention.

Claims (1)

[Claims] 1. N i , A g , A on the inner wall of the glass tube
1. An optical fiber having a metal film, characterized in that it has a metal film made of at least one metal selected from the group consisting of Cu, Cu, is hollow, and is used for energy transmission.