JPS60103315A - Flexible optical waveguide - Google Patents

Abstract

PURPOSE:To obtain an optical waveguide which is usable over a wide wavelength range and has superior dynamic properties such as flexibility and superior environmental resistance such as moisture resistance by forming a metallic layer which has a high reflection factor to light with in-use wavelength over the internal surface of a flexible tube. CONSTITUTION:The reflecting layer formed over the internal surface of the flexible tube is preferably a smooth surface with less ruggedness increasing the transmission loss of light and needs to have a high reflection factor to light with in-use wavelength so as to utilize the reflection of light from a metallic surface. However, there are restrictions when metal is stacked on the internal surface of the tube and the metallic layer constituting to the reflecting layer is not limited to one layer. The material and diameter of the tube are not specified specially; silver is deposited as the reflecting layer over the internal surface of a polyethylene tube having, for example, a 1mm. internal diameter by displacement plating to form a flexible optical waveguide, which is used to form a double loop with a 4mm. radius, thereby guiding visible light.

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECTS AND BACKGROUND OF THE INVENTION The present invention relates to a waveguide for guiding light through an arbitrary path. The present invention relates to flexible optical waveguides particularly useful for infrared light.

As flexible optical waveguides, various so-called optical fibers have been studied and developed. Optical fibers currently in practical use are mainly optical waveguides with a diameter of 2 μm or less, and are not suitable for optical communication. For example, silica-based optical fibers have 0 transmission loss for light with a wavelength of 1.5 μm. zdB
/km, which is close to the limit performance.

However, for light with a wavelength shorter than this wavelength, the transmission loss due to Rayleigh scattering etc. increases]-1 For light with a wavelength longer than this wavelength, characteristic absorption based on the fundamental vibration of the material used However, there is a problem in that the transmission loss of optical energy increases rapidly as the wavelength increases. The situation is the same for polymer-based optical fibers.

Therefore, as infrared light fibers, optical fibers using materials whose characteristic absorption due to their fundamental vibration is on the longer wavelength side, such as heavy metal oxides, chalcogen compounds, and halogen compounds, have been investigated.

However, in the case of optical fibers using heavy metal oxide glass, the shift of the characteristic absorption wavelength by heavy metals to the longer wavelength side is not so large, so if the wavelength is 2 μm or more, GeO□-
Although an optical fiber using 8bzOa glass has lower loss than a silica glass optical fiber, it is difficult to reduce the loss in the 10.6 μm wavelength range of a carbon dioxide laser, for example.

It has been known for a long time that compounds such as ASXSe and S, so-called chalcogenite compounds, are transparent in the infrared region, but among these, the antecedent of As poses a problem, so recently 2.
Optical fibers using chalcogen compound glass that does not contain As are mainly being studied. In the case of optical fibers using chalcogen compound glass, there is a possibility of low loss in the 2 to 6 μm band, but in the 10 μm band, there is a limit to the reduction in loss due to the characteristic absorption tail of chalcogen compounds. There is.

Z r Fd type glass and /uFB type glass are being considered as halogen compound glasses, but the transmission range is 8 / uFB type glass.
J+n or less. Regarding alkali halide compound proboscis, single-crystal optical fibers and polycrystalline optical fibers have been tested, but there are problems with mechanical performance such as flexibility due to the cleavage of the crystal, and in the case of polycrystalline optical fibers, There is a limit to reducing loss due to scattering due to crystal grain boundaries.

The above example is an optical fiber in which the center of the optical fiber is made of solid material, and the refractive index outside the center is lower than that of the center to guide light.
Basically, the usable wavelength band is determined by the characteristic absorption V of the phase material used, and flexibility, etc. cannot be avoided from constraints derived from the properties of the phase material used.

In addition, by taking advantage of the fact that many glasses have a refractive index smaller than 1 for light with a wavelength around 10μ7n, for example, G e 02 ZIIO-
There is also an attempt to create a hollow fiber made of 20 series glass and use it as an optical fiber, but the wavelength range used is 10.
It is limited to a relatively narrow region around μηl, and it is difficult to arbitrarily change the flexibility.

Summary of the Invention The present invention was developed in view of the current situation, and its purpose is to be usable in a wide wavelength range, and to improve mechanical properties such as iJ flexibility and four environmental properties such as moisture resistance. The objective is to provide an excellent optical waveguide.

The optical waveguide to which the present invention is directed is a flexible tube made of at least one of the above materials, and the inner surface of the tube is made of a metal or Items 1 to 1 are characterized in that at least one metal layer of the alloy is laminated.

In other words, the flexible optical waveguide that is the subject of the present invention has a central part of the waveguide made of air, etc., and on the outside thereof, which has a high reflectance and a low reflectivity for light of a wavelength corresponding to the wavelength that is guided at a contact with the waveguide. A reflective layer with a smooth inner surface that causes transmission loss is provided on the outside of the reflective layer, and is tightly adhered to the reflective layer to suppress changes in the cross-sectional shape of the trout due to external forces and to reduce mechanical properties such as 'jr'h properties. It has a structure with a diameter of 1∆ outside the chamber that provides performance such as properties and environmental resistance.

3. Detailed Description of the Invention In the flexible optical waveguide of the present invention, a metal layer is formed on the inner surface of the flexible core.

In the present invention, the term "flexibility" is used to mean a state in which the light can be bent along the path to which light is to be guided, and can be restored to its original state with almost no buckling. DR flexibility can be imparted by adjusting the structure of the pipe, such as the diameter and wall thickness of the pipe.

For one official! Thermoplastic resins such as d1 polyethylene, polypropyreno, vinyl chloride, A, B S 4nl resin, polyamide, polyester, natural rubber, 5B1 (, chloroprene, ethylene-propyl/
Rubber-like materials such as 7-type rubber, glass, etc. can be used.

The diameter of the tube is not particularly limited and can be set depending on the application, but when the diameter is large, care is taken to prevent buckling due to bending by increasing the wall thickness.

When using a highly rigid material such as glass, the diameter should be 5+l.
The length is preferably 1 m or less, preferably 3 # or less, and the outer periphery is preferably covered with the above-mentioned thermoplastic resin or rubber-like substance.

The reflective layer formed on the inner surface of the flexible tube utilizes the reflection of light by the golden surface, so it is preferably a smooth surface with few irregularities that would cause an increase in low-layer loss of light. Although it is still necessary to have a high reflectance for light of the wavelength used, there are restrictions when laminating metal on the inner surface of the tube, so the metal layer that constitutes the reflective layer does not necessarily have to be one layer.

The metal material that can be used may be a single metal material or an alloy, but silver, copper, gold, aluminum, chromium, nickel, etc. are suitable as metals that have high reflectance over a wide wavelength range. It can be given as an example.

The thickness of the reflective layer may depend on the material of the reflective layer, but recently it is necessary to have a thickness of 20 to 30 angstroms or more, but the upper limit may be as long as it does not impair the necessary flexibility.

In terms of function, if the required flexibility is 81 degrees, that is, the radius of curvature when the optical waveguide is bent is 10z or more, then the thickness of the metal layer should be 50 to 100μ? When the radius of curvature is several inches or less, the thickness of the metal layer is 10 to 20 μ7. Hereinafter, when the radius of curvature is one fold M or less, the thickness of the metal layer is 5 to 10 μm or less.

The part that will become the waveguide may generally be filled with air, but it may also be filled with an inert gas to prevent oxidation of the reflective layer.
It may even be a tiny vacuum.

Various methods can be considered for manufacturing the flexible optical waveguide of the present invention. Typical examples will be described below, but the present invention is not limited thereto in any way.

(1) The inner surface of a plastic tube or glass tube with a smooth inner surface is treated with a chromic acid mixture, etc. to make it sufficiently clean and hydrophilic, and after performing treatments such as sensitization and activation, chemical Plating solution is flowed to form a metal layer on the inner surface of the tube. If necessary, the metal surface may then be chemically polished to smooth the inner surface. The metal layer that can be made by this method is silver, copper, nickel, etc., and may be used as a reflective layer as is, or may be replaced with gold or the like on the surface by displacement plating to serve as a reflective layer.

(2) After forming a metal layer by vapor deposition, chemical plating, etc. on the surface of fibers or hollow fibers that have a smooth outer surface and are soluble in solvents, acids, or alkalis, this outer layer is used as needed. If appropriate, an adhesive layer is interposed to form a protective layer (outer layer), and then a solvent or acid that does not attack the metal layer or the outer layer,
Remove the fibers or hollow fibers in the center using an alkali or the like.

(3) An organometallic compound is passed through a plastic or glass tube and heated to decompose the organometallic compound and form a metal layer on the inner surface of the tube.

(4) After dissolving the metal salt in the entire glass tube or inside it, a reducing gas is flowed while heating to reduce the metal salt on the inner surface and form a metal layer.

(5) After depositing a highly ductile and highly reflective metal such as gold or aluminum on the inner surface of a glass tube that is thick enough to be vacuum-deposited on the inner surface, the metal layer does not peel, cut, or become droplets. The glass tube is heated and stretched in a non-oxidizing atmosphere under conditions that do not cause oxidation, so that it has the necessary inner diameter and flexibility. If necessary, a glass coating may be applied after this to improve mechanical properties.

The flexible optical waveguide obtained by the present invention can be used for waveguide in the ultraviolet region for which there is currently no suitable flexible waveguide, and as a flexible waveguide for infrared lasers such as carbon dioxide lasers, using welding machines and fusing. In addition to being used for machines, laser scalpels, etc., it can also be used as a connector between light emitting diodes, semiconductor lasers, etc. and ordinary optical fibers, etc., or between ordinary optical fibers by giving flexibility in the circumferential direction of the tube to the material of the interlayer. However, this example does not preclude the use of the flexible optical waveguide of the present invention as a step-index optical fiber for other purposes.

Examples of the present invention are shown below, but the present invention is not limited in any way by this.

Example The inner surface of a polyethylene pipe with an inner diameter of 1 mm was coated with the material shown above (
Silver was laminated by the method of 1) to form a flexible optical waveguide.

Using this waveguide, we formed a double laser with a radius of 4 mm and were able to guide visible light.

Patent applicant Mitsubishi Yuka Co., Ltd. Agent: Patent Attorney Hidetoshi Furukawa (1 other person)

Claims (1)

[Claims] 1. A flexible optical waveguide, characterized in that a metal layer having a high reflectance for light at the wavelength used is formed on the inner surface of a flexible tube made of at least one layer of material.