JPH0264504A - Production of optical fiber for infrared light - Google Patents

Abstract

PURPOSE:To obtain the fiber which can transmit high energy by setting an extrusion temp. at 210 to 230 deg.C at the time of forming the solid soln. of thallium bromide and thallium iodide by a warm extrusion method to the fiber. CONSTITUTION:The perform crystal 1 of the solid soln. (KRS-5) of the thallium bromide and thallium iodide is set in a container 4 and is extruded to form the fiber by setting the extrusion temp. at 210 to 230 deg.C by a heater 5 and applying 8t/cm<2> pressure to a punching rod 7. While the causes for the deterioration of the fiber include the scattering by the stress and strain generated at the time of the extrusion molding and the thermal strain generated by rapid cooling, the scattering and thermal strain are minimized by setting the extrusion temp. at 210 to 230 deg.C. The optical fiber which has high power resistance and can transmit the high energy without being deteriorated even if CO2 laser light of high power is passed therethrough is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method of manufacturing an infrared optical fiber used for high energy transmission, etc. useful for laser scalpels or laser processing machines.

BACKGROUND OF THE INVENTION Recently, attempts have been made to utilize laser light in the infrared region in laser scalpels in the medical field, laser processing machines in the industrial field, etc., and in particular, CO2 lasers are often used. If a fiber capable of transmitting these wavelengths in the mid-infrared region with high energy can be obtained, a wide range of applications will become possible.

Chalcogen glass and metal halides are used as mid-infrared fibers, and in particular, solid solutions of thallium bromide and thallium iodide (KRS-5) are used for CO2 lasers.
．． It is an excellent material that can transmit a wavelength of 6 μm with high power.

KRS-5 fiber has a temperature of approximately 245°C and a pressure of approximately 8 tons.
/cm2, manufactured by warm extrusion method.

Problems to be Solved by the Invention However, when a high power CO2 laser beam is passed through a KRS-5 fiber manufactured by a conventional method, it deteriorates at about 250 W. In order to use a fiber in a laser processing machine, it must be possible to transmit at least 300 W of C02 laser light.

One way to increase the power resistance of the fiber is to heat-treat the extruded fiber, but in this case the mechanical strength becomes weaker.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a method for manufacturing an infrared optical fiber having high power resistance while maintaining mechanical strength as before.

Means for Solving the Problems The present invention is a method of forming a solid solution of thallium bromide or thallium iodide into a fiber by warm extrusion, in which the temperature during extrusion is 210°C to 230°C.

One of the causes of deterioration of working fibers is scattering due to stress strain during extrusion molding, and in order to improve power resistance, this stress strain must be reduced.

In order to reduce stress strain, it is best to extrude the crystal at a high temperature in a soft state, but if the temperature is too high, thermal strain will occur due to rapid cooling after extrusion. Therefore, by extruding at a temperature that minimizes stress strain and thermal strain, a fiber with high power resistance can be obtained.

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

FIG. 1 is a conceptual diagram showing the entire fiber manufacturing apparatus. l is preform crystal, 2 is polycrystalline infrared fiber, 3
is a die that determines the thickness of the fiber, 4 is a container for processing, 5 is a heater for heating, 6 is a guide that also serves as an upper lid, 7 is a punch rod, and 8 is a holding stand.

A method for manufacturing a fiber according to the present invention will be explained step by step. A KRS-5 single crystal is preformed into a cylindrical shape to match the shape of the container 4. This preform crystal 1 is set in a container 4, set at an appropriate temperature with a heater 5, and extruded into a fiber by applying a pressure of about 8 t/cm 2 to a bunch rod 7 using a hydraulic press.

Figure 2 shows the extrusion temperature when the extrusion pressure is 8t/cm2,
It is a graph showing the relationship between damage thresholds of short fibers with a length of 6 cm. The power resistance shows a maximum value at an extrusion temperature of 220°C. Therefore, the appropriate extrusion temperature is 210°C to 230°C.

FIG. 3 is a graph showing the relationship between extrusion pressure and damage threshold of a short fiber having a length of Gcm when the extrusion temperature is 220°C. Power resistance is hardly affected by extrusion pressure. Therefore, from 4 t/cm” to 12 t/cm”
It may be extruded at any pressure of cm2.

Effects of the Invention As is clear from the above explanation, the present invention provides KRS-5
When converting crystals into fibers by warm extrusion, the extrusion temperature is set to 21
By setting the temperature from 0°C to 230°C, stress strain and thermal strain during molding are minimized, and scattering is reduced, making it suitable for high-energy transmission infrared with higher power resistance for laser scalpels or laser processing machines. This has the effect of being able to provide optical fibers.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram showing the entire fiber manufacturing apparatus used for carrying out the infrared optical fiber manufacturing method according to the present invention, and FIG. 2 shows the extrusion temperature at an extrusion pressure of 8 t/cin2, A graph showing the relationship between the damage threshold of a short fiber with a length of 6 cm, and FIG. 3 shows the relationship between the extrusion pressure and the damage threshold of a short fiber with a length of 6 cm when the extrusion temperature is 220 ° C. It is a graph. l... Preform crystal, 2... Polycrystalline infrared phyto... Preform crystal, 2... Polycrystalline infrared fiber, 3... Dice, 4... Container for processing, 5...・
Heating heater 6...Guide, 7...Punch rod,
8...Name of holding stand agent Patent attorney Shigetaka Awano 1 person Fig. 2 Polycrystalline infrared fiber Fig. Output temperature (°C)

Claims (1)

[Claims] (1) A method for producing an infrared optical fiber, which comprises forming a solid solution of thallium bromide or thallium iodide into a fiber by warm extrusion, the temperature during extrusion being 210°C to 230°C.