JPS63266404A - Hollow light guide and its production - Google Patents

Abstract

PURPOSE:To decrease the transmission loss of a waveguide and to lessen an increase in loss by bending by providing a thin film layer consisting of a specific metal between an internally provided dielectric layer and a thick film metallic layer provided on the outside. CONSTITUTION:The thick film metallic layer 23 consisting of Ni, etc., is formed via the thin film metallic layer 22 consisting of Au, Ag or Cu on the dielectric layer 21 consisting of a material having small absorption in an IR wavelength range (e.g.: ZnSe) and having a circular section. The film thickness of the layer 22 is preferably <=0.5mum. A layer consisting of other metals may be interposed between the layer 22 and the layer 23. This waveguide is produced by successively forming the layer 21 and the layer 22 on a base material pipe which can be etched and forming the layer 23 by electroplating using the layer 22 as an electrode on said layer, then removing the base material pipe by etching.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a hollow optical waveguide with a dielectric inside and a method for manufacturing the same, and is particularly suitable for transmitting carbon dioxide laser light used in medical and industrial processing. The present invention relates to a low-loss, flexible hollow optical waveguide and a method for manufacturing the same.

[Conventional technology] Carbon dioxide lasers have high oscillation efficiency and can obtain large output, so they are used for laser scalpels for medical purposes, welding for industrial processing,
It has come to be widely used for cutting, etc. However, since its oscillation wavelength is in the infrared W4 region of 10.6μ clear, conventional silica-based optical fibers have large losses and cannot be used as waveguides for carbon dioxide laser light.

Therefore, currently, the main means for guiding carbon dioxide laser light is aerial transmission using several mirrors, which is extremely disadvantageous in terms of operability.

Therefore, as a result of the development of infrared fibers as waveguides for carbon dioxide laser light, hollow metal optical waveguides with a dielectric inside were proposed for the purpose of even greater power transmission. A prototype hollow optical waveguide with nickel interior has been produced (M, Miyaol,
A, f-1ongo, Y.

Aizawa, and S. Kawakami
, Appl, phys.

1-ett, , 43. 430 (191113)
), this manufacturing method first uses an aluminum pipe as a base material, forms a germanium layer 11 on its outer surface by sputtering, and then coats the outer surface with nickel It! 12
is formed by electroplating, and then the aluminum pipe serving as the base material is removed by etching to form the hollow region 10.
, thereby forming a germanium-incorporated nickel hollow optical waveguide.

Until now, the transmission loss in a 1m-long hollow optical waveguide was 0.35.
dB has been obtained, but this is about an order of magnitude worse than the theoretical value, and the increase in transmission loss due to bending is still large. In this germanium-incorporated nickel hollow optical waveguide, nickel is electroplated directly on the germanium thin film 11, but the nickel layer 12 not only maintains mechanical strength but also contributes to optical transmission loss.

For the metal in contact with the dielectric, the mechanical strength will be greater if a thick film is used, and the absolute value of the complex refractive index is sufficiently large, or the imaginary part of the complex refractive index is sufficiently large compared to the real part. The transmission loss will be smaller if . In this respect, nickel can be easily formed into a thick metal layer by electroplating and is suitable for maintaining the mechanical strength of the waveguide, but it cannot be said to be the best material for forming the waveguide wall. .

In addition, in the conventional germanium-incorporated nickel hollow optical waveguide described above, nickel is electroplated using germanium's ￥lff1 property, but since germanium does not have high conductivity, the nickel layer 12 has an uneven distribution of film thickness. defects such as pinholes and blisters. In particular, when an insulating pipe other than aluminum is used as the base material pipe, the non-uniformity of the thickness of the metal layer due to plating becomes significant.

[Problems to be solved by the invention] As described above, in the conventional dielectric-incorporated metal hollow optical waveguide, the transmission loss is not small enough for practical use, and defects are likely to occur during the manufacturing process, resulting in poor reproducibility. The drawback is that it is difficult to obtain a certain stable waveguide.

The purpose of the present invention is to eliminate the drawbacks of the prior art described above,
An object of the present invention is to provide a hollow optical waveguide that is capable of low-loss transmission, is resistant to bending, and has fewer defects in the manufacturing process, and a method for manufacturing the same.

[Means for Solving the Problems] The hollow optical waveguide of the present invention has a dielectric layer with a circular cross section and low absorption in the infrared wavelength range, and an external layer that increases the mechanical strength of the waveguide. In the hollow optical waveguide, a thin metal layer is provided on and in contact with the dielectric layer, and this thin gold a layer has a complex refractive index of absolute 1.
A metal with high directivity and high conductivity, ie, gold, silver, or copper, is used, and the WI demetallized layer is a waveguide r8Il! It also serves as an electrode for the thick metal layer formed on the outside by electroplating.

Further, a method for manufacturing a hollow waveguide according to the present invention is as follows. First, a dielectric layer having low absorption in the light wavelength band to be transmitted is formed by sputtering or vacuum evaporation on a base material pipe that can be etched, regardless of whether it is conductive or not. For example, suitable dielectric materials at a wavelength of 10.6 μm include Ge, ZnSe,
, ZnS, KCJ2°NaCβ, chalcogenide glass, and fluoride compounds. In the infrared band, 7
All substances such as scales, which are important transmission media for IM waves, behave as dielectrics.

Further, on the outside of these dielectric layers, gold is coated with a sufficiently large complex refractive index and high electrical conductivity.

Either silver or copper nR gold! i! ! The layer is formed by sputtering, vacuum evaporation, ion blasting, electroless plating, or the like. At this time, the thickness of the thin metal layer is 0.5μ
It is important to keep it below m. That is, in order for this thin film base yt layer to play the role of a waveguide wall, l! The thickness should be sufficiently thicker than the epidermal thickness (skin depth). but,
If the thickness of the thin metal layer formed by the above method exceeds 0.5 μm, the film will easily peel off or crack due to external factors such as sudden bending.

The conductivity of this L-film metal layer can be used to form another thick metal layer by electroplating directly on this gold layer, or to form another metal layer by electroless plating, e.g.
Another thick metal layer is formed by electroplating through an alloy layer based on Cu*A(++ Au and Ni, P. Generally, electroless plating shows brittleness to bending and thick film formation This is difficult, and a thick metal layer to maintain the mechanical strength of the waveguide must be formed by electroplating. After RLK, the base material pipe is removed by chemical etching to form a hollow optical waveguide.

[Function] As described above, in the hollow optical waveguide of the present invention, the innermost iF
At least one metal layer is formed between the electrically conductive layer and the outermost thick metal layer formed by electroplating, of which the thin metal layer in contact with the dielectric layer has a thickness of 0.5 mm.
It is made of gold, silver, or copper with a diameter of 5μ or less.

Therefore, the thin metal layer is the best material for forming the waveguide wall, so a hollow optical waveguide with low transmission loss can be obtained, and the increase in transmission loss due to bending is tolerably small. In addition, thin metal layers made of gold, silver, and copper have extremely high conductivity, and because they are used as electrodes for electroplating, uneven distribution of film thickness may occur in the thick metal layer formed by electroplating. J! such as Binhole Yafukure! There is no possibility of quality defects. Therefore, there is no need to use a relatively conductive material such as Ge for the internal electric body, and a stable waveguide can be obtained even with a material that has almost no J[ property. Furthermore, the base material vibrator that can be etched does not require the use of a conductive vibrator such as aluminum.

[Example] Examples of the present invention will be described below with reference to FIGS. 1 and 2.

Figure 1 shows a sample of 7-nSe manufactured by the above-mentioned manufacturing method.
FIG. 2 is a cross-sectional view of a (zinc selenide) interior silver hollow optical waveguide. Here, Zn5e1i! ! 21 and Ag! ! Reference numeral 122 optically constitutes a waveguide wall, which is formed by sputtering or vacuum deposition. Furthermore, the nickel layer 23 formed by electroplating on the outside serves only to maintain mechanical strength. 20 is a hollow area. The thickness of each layer is 0.7 μra for the Zn5e layer 21, A!
J! IJ22 is 0.2 μm.

There are 200μ1llt' of Ni Fm23. Zn5ef
f121's! 1! Thickness greatly affects transmission loss, and transmission loss is 1! of 1nSe! It changes periodically as the thickness changes.

A film thickness of Δg1m22 does not have a large effect on transmission loss in a narrow sense, but when it exceeds 0.5 μm, the film peels and loses its gloss, causing Ni-plated! 23, defects such as blisters and pinholes will occur.

Instead of forming a silver layer on ZnSe by sputtering or vacuum deposition, the metal layer can also be formed by electroless plating. Since electroless plating is brittle against bending, the thickness in m must be 0.5 .mu.m or less in this case as well.

FIG. 2 shows a silver layer 32 formed by sputtering or vacuum evaporation and a Ni layer 32 formed by electroplating.
! ! 134, a Ni alloy layer 3 is formed by electroless plating.
This is an example in which 3 is interposed. 3° is a hollow region, and 31 is a zinc selenide layer. If the N1 alloy 1133 formed by electroless plating is too thick, cracks will occur when bent, so the best thickness is about 0.5 μm. The waveguide constructed in this manner is particularly suitable for a long waveguide with a small diameter.

Note that when the metal in contact with the dielectric is copper, the metal layer interposed between the thin copper film and the thick metal layer formed by electroplating can be formed of Ni, ALI, AC+, etc. by electroless plating. be. 5 [Effects of the Invention] To summarize, the present invention provides the following excellent effects.

(1) According to this waveguide, a thin film of gold, silver, or copper is interposed on the dielectric layer as a waveguide wall, so the transmission loss is small and the loss due to bending is increased. It is also possible to obtain a flexible waveguide that is smaller in size, enables low-loss transmission, and is resistant to bending.

(2) According to this manufacturing method, the thick metal layer is formed by electroplating using the RWA metal layer as an electrode, so the uneven thickness and poor film quality of JW1m gold Ji [W:4] are eliminated. As a result, a stable hollow optical waveguide can be obtained during the manufacturing process.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a silver hollow optical waveguide containing zinc selenide in which AC117 is interposed between Zn se m and Ni1l formed by electroplating, showing one embodiment of the present invention.
FIG. 2 shows another embodiment of the present invention, in which a zinc selenide-incorporated silver hollow is interposed between a Zn5e layer and a Ni alloy layer formed by electroplating with A+IIM and a Ni alloy layer formed by electroless plating. FIG. 3 is a cross-sectional view of a conventional germanium-incorporated nickel hollow optical waveguide. In the figure, 20.30 is a hollow region, 23.34 is an electroplated nickel layer, 21.31 is a zinc selenide layer, 22
．． 32 is a silver layer, and 33 is a nickel alloy layer formed by electroless plating. Patent Applicant Hitachi Cable Co., Ltd. Patent Attorney Nobuo Kinutani Figure 1 Figure 2 Figure 3 20.30: Hollow region 22.32: Ri I (rumored shoes)

Claims (4)

[Claims] (1) A thin metal layer made of gold, silver, or copper is provided as a waveguide wall on a dielectric layer with a circular cross section and low absorption in the infrared wavelength range, and the mechanical structure of the waveguide is A hollow optical waveguide characterized by having a thick metal layer that maintains strength. (2) The waveguide according to claim 1, further comprising a metal layer different from the thin film metal layer and the thick film metal layer interposed between the thin film metal layer and the thick film metal layer. (3) The waveguide according to claim 1 or 2, wherein the thickness of the thin metal layer is 0.5 μm or less and greater than the skin thickness. (4) Forming a dielectric layer on an etched base material pipe, providing a thin metal layer made of gold, silver, or copper on top of the dielectric layer, and electroplating using this thin metal layer as an electrode. A method for manufacturing a hollow optical waveguide, comprising forming a thick metal layer on the outside and then removing the base material pipe by etching to manufacture the hollow optical waveguide.