JP2006243306A - Aluminum hollow optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum hollow optical fiber having high durability to high power laser light. <P>SOLUTION: In the aluminum hollow optical fiber having an aluminum thin film formed on an inner surface of a thin glass capillary with high flexibility, a layer of a metal other than aluminum is formed between the glass capillary and the aluminum thin film and thereby the thickness of the metallic layer is increased without increasing the surface roughness, and the durability at emission of the high power laser is improved while maintaining high transmission efficiency. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a method for manufacturing an aluminum hollow optical fiber.

Hollow fibers or hollow optical fibers in which an aluminum thin film is formed on the inner surface of a small-diameter quartz glass tube are being developed mainly as transmission paths for ultraviolet and vacuum ultraviolet laser light. Since this hollow fiber uses air or gas as the core, the end face is not likely to break, and there is no reflection at the end face, so there is a short instantaneous power that cannot be transmitted by a normal silica glass optical fiber. It is suitable for transmission of pulsed light, and is applied to industrial and medical fields using nanosecond pulsed light represented by Q-switched Nd: YAG laser and picosecond and femtosecond pulses with shorter pulse width. ing.

When laser pulse light with high instantaneous power is transmitted through an aluminum hollow fiber, the aluminum thin film formed on the inner surface of the glass tube may be ablated by laser irradiation, particularly at the bent portion of the fiber, and the aluminum thin film may be damaged. This damage can lead to an increase in fiber transmission loss and, in turn, damage to the fiber itself.

In order to improve the durability of the aluminum thin film in the glass tube against laser irradiation, a method of increasing the film thickness of the aluminum layer can be considered, but as the film thickness increases, the surface roughness of the aluminum thin film increases. In particular, there is a drawback that the transmission efficiency of the fiber is lowered due to an increase in scattering loss with respect to light having a short wavelength in the ultraviolet / vacuum ultraviolet region.
Japanese Patent No. 3341007

An object of the present invention is to improve the durability of an aluminum hollow optical fiber against high-power laser light.

In order to achieve the above object, the present invention provides a hollow optical fiber in which an aluminum thin film is formed on the inner surface of a glass thin tube, and a high-power laser is provided by providing a metal layer different from aluminum between the glass tube and the aluminum thin film. An aluminum hollow optical fiber with improved durability against light is provided.

Here, the metal layer may be any of silver, nickel, copper, molybdenum or chromium, and the metal layer may be formed by a plating method or a chemical vapor deposition method. . Furthermore, the laser beam may be a short pulse beam.

Since the thickness of the metal layer increases, the strength of the metal layer increases and the durability against laser irradiation improves.

If a metal exhibiting higher adhesion strength than glass is used as the intermediate layer, the adhesion strength of the metal layer is increased and the durability against laser irradiation is improved.

Even if the thickness of the metal layer increases, the thickness of the aluminum thin film can be reduced, so that the surface roughness can be kept low.

Durability when transmitting laser light with high instantaneous power is improved by reducing the transmission loss by increasing the mechanical strength and adhesion strength of the metal layer and reducing the surface roughness.

Hereinafter, an example of an embodiment of the present invention will be described in detail. The case where a silver thin film is formed by a plating method based on the silver mirror reaction will be described in detail below as the intermediate layer metal, but the same effect can be obtained by forming a metal other than silver by various methods other than the plating method. It is done. For example, molybdenum can be produced on the inner surface of a glass tube by the CVD method. The surface of the metal layer needs to be sufficiently smooth so that a smooth surface can be obtained when an aluminum thin film is formed on the intermediate metal layer. Preferably, the mean value of the surface roughness is 10 nm or less, and in order to adapt to a shorter wavelength such as vacuum ultraviolet, it is necessary to be 5 nm or less. The thickness of the metal layer serving as the intermediate layer is not particularly limited, but is preferably 300 nm or less in order to obtain sufficient smoothness. In addition, the glass thin tube as the base preferably has an inner diameter of 1 mm or less and a glass wall thickness of 100 μm or less so that sufficient flexibility can be obtained, and a protective coating with resin is applied to the surface. It may be a thing.

In order to form a silver thin film on the inner surface of a glass tube, an aqueous silver nitrate solution is mixed with a glucose solution and immediately flowed into the glass tube. At this time, the thickness of the silver thin film to be produced can be determined by controlling the concentration, amount and inflow rate of the solution. In addition, if the thickness of the intermediate metal layer is very thin and less than 50 nm and exhibits a translucent black-brown color, the roughness of the surface can be kept small, and the aluminum film is formed in the next process. The formation of the aluminum thin film can be visually confirmed. In addition, when forming a silver thin film, a plurality of glass tubes can be bundled to simultaneously process a large number of tubes.

Next, an aluminum thin film is further formed on the inner surface of the glass thin tube on which the intermediate metal layer is formed. As the method, it is preferable to use a chemical vapor deposition method (MOCVD method) using an organic metal as a raw material. When the vapor of the organoaluminum raw material is caused to flow into the glass thin tube and heated to about 50-150 ° C. from outside, an aluminum thin film is formed on the inner surface of the thin tube. At this time, if the treatment with titanium chloride vapor is performed as a pre-process, the reaction occurs at a lower temperature, and the surface roughness of the aluminum can be reduced. It is possible to form an aluminum thin film with a uniform thickness in the longitudinal direction of the tube by moving the heater that heats from the outside along the glass tube. To longer than 2 m can be manufactured.

It is sectional drawing which shows one Embodiment of this invention.

Explanation of symbols

1 hollow fiber 2 glass capillary tube 3 intermediate metal layer 4 aluminum thin film 5 hollow region

Claims (4)

Aluminum hollow optical fiber in which an aluminum thin film is formed on the inner surface of a thin glass tube, and the durability against high-power laser light is improved by providing a metal layer different from aluminum between the glass tube and the aluminum thin film. . 2. The aluminum hollow optical fiber according to claim 1, wherein the metal layer is silver, nickel, copper, molybdenum, or chromium. The aluminum hollow optical fiber according to claim 1, wherein the metal layer is formed by a plating method or a chemical vapor deposition method. The aluminum hollow optical fiber according to claim 1, wherein the laser light is short pulse light.