JP2740601B2 - Copper-containing polarizing glass and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing glass used for an ultra-small optical isolator used in optical communication using a semiconductor laser and an optical fiber, a method for manufacturing the same, and an optical isolator using the polarizing glass.

[0002]

2. Description of the Related Art In an optical communication using a silica-based optical fiber with a semiconductor laser having a wavelength of 1.31 μm or 1.55 μm as a light source, an optical isolator is used to block return light due to reflection and improve the S / N ratio. Used.
The optical isolator is composed of a Faraday rotator, two polarizers, and a magnet. To reduce the size of the optical isolator, it is necessary to reduce the size of each element. However, it is not easy to reduce the size of the polarizer without deteriorating its extinction ratio or environmental resistance. For example, a birefringent crystal or a polarizing beam splitter cannot have a thickness smaller than the effective beam diameter.
In addition, a conventionally known polymer-type polarizing plate obtained by stretching a dichroic dye can be made thin, but the extinction ratio and environmental resistance are insufficient.

[0003]

As a polarizer that can satisfy these conditions, a polarizing glass in which fine metal particles having a large aspect ratio are arranged in one direction in glass can be considered. U.S. Pat.
The glass containing copper disclosed in 3954485 is known. According to the specification, the glass is heated to 500 to 900 ° C. by heating aluminoborosilicate glass containing a halogen element and copper oxide and / or cadmium oxide (in the embodiment, copper oxide and cadmium oxide) to 100 to 900 ° C. 1
A second phase rich in boric acid containing 2,000 ° C. of copper-cadmium halide is precipitated and has a viscosity of 1 × 10 ⁷ to 1 × 1.
By stretching the sample about 50 times while maintaining the temperature range of ⁰⁹ poise, the second phase is deformed so that the aspect ratio becomes 2: 1 to 5: 1, and cooled to a temperature lower than the annealing point. Created.

[0004] This glass is intended for eyeglasses and has a second phase of 100 to impart transparency in the visible region.
It is as small as 0 ° (100 nm) or less and has photochromic characteristics. Further, this glass exhibits polarization characteristics when irradiated with light having a short wavelength (0.3 to 0.45 μm) to be in a darkened state (a state in which the glass is colored by light). However, even in such a darkened state, the extinction ratio is 10:10.
It is only about 1 (10 dB), which is smaller than the extinction ratio (30 dB) required for an optical communication isoletter.

The reason for this is described in US Pat. No. 3,954,485 and the related literature (Journal of noncrystalline solid, 3).
3, pp. 383-390, 1979). That is, in the glass containing copper halide-cadmium, the second phase particles precipitated by the heat treatment are converted into particles of 100 to 1000 ° made of glass rich in a boric acid component and 20 to 50 ° of copper halide which contributes to the development of photochromic properties. Having a structure containing particles made of cadmium, when the glass is drawn, the second phase particles of 100 to 1000 ° are drawn, but the 20 to 5 particles present therein are drawn;
Particles consisting of 0 ° copper-cadmium halide are not stretched. This is because the copper halide-cadmium particles have a small particle size, so that a large force is required for drawing, and drawing is difficult. In addition, the reason why the polarization characteristics are weakly expressed is that copper halide-
This is because the particles made of cadmium are arranged anisotropically.

Further, the wavelengths used for optical communication are 1.3 to 1.
With 55 μm infrared light, the copper-containing glass cannot be darkened, and thus the extinction ratio of the glass is very small. Therefore, the copper-containing glass disclosed in US Pat. No. 3,954,485 cannot be applied to a polarizer for an optical communication isoletter.

An object of the present invention is to provide a polarizing glass containing metallic copper and having a high extinction ratio in the infrared region that can be used for optical communication, and a method for manufacturing the same. It is a further object of the present invention to provide an optical communication isolator using a polarizer that can be miniaturized.

[0008] The polarizing glass of the present invention is a polarizing glass containing shape-anisotropic particles oriented and dispersed in at least a surface layer of a glass substrate, wherein the glass substrate is a silicate glass;
It is made of glass selected from the group consisting of borate glass and borosilicate glass, and the shape anisotropic particles are metallic copper particles.

The present invention further provides a step of heating a glass containing copper and halogen but not containing cadmium and exhibiting no photochromic properties to precipitate copper halide particles in the glass; Drawing the copper halide particle-containing glass at a temperature at which the viscosity of the copper particle-containing glass becomes 1 × 10 ⁸ to 1 × 10 ¹¹ poise, and reducing some or all of the copper halide particles in the drawn glass The present invention relates to a method for producing a copper-containing polarizing glass including a step of performing

Hereinafter, the present invention will be described.

The shape-anisotropic metal copper particles contained in the polarizing glass of the present invention are preferably metal copper particles having an aspect ratio of 2: 1 to 15: 1. The aspect ratio means the aspect ratio of the metallic copper particles, where the vertical is the length in the longitudinal direction of the metallic copper particles, and the horizontal is the length perpendicular to the longitudinal direction, that is, the width. The aspect ratio is a factor that determines the absorption wavelength in the length direction and the width direction of the metal copper particles. In order to exhibit excellent polarization characteristics with respect to infrared light having a wavelength of 1.3 to 1.55 μm, it is appropriate that the aspect ratio of the metal copper particles is 2: 1 to 15: 1. The reason is that when the aspect ratio of the metallic copper particles is less than 2: 1, polarization characteristics are exhibited in the visible region, and when the aspect ratio is greater than 15: 1, excellent polarization characteristics in the mid-infrared region or far-infrared region are obtained. This is because it becomes as shown. Further, when the copper particles are metallic copper, the glass shows a polarizing property for the first time, and when it is another copper compound, the glass shows almost no polarizing property. However, as long as metallic copper is contained, other copper compounds such as copper halide may coexist.

In the polarizing glass of the present invention, the glass substrate is made of glass selected from the group consisting of silicate glass, borate glass and borosilicate glass.

The method for producing the polarizing glass of the present invention will be described below.

In the present invention, a glass containing copper and halogen is used as a raw material glass. As such a glass, when converted to the following components by weight%, SiO ₂ is 48 to 65%, B ₂ O ₃ is 13 to 33%, and Al ₂ O ₃ is 6-1.
3%, AlF ₃ 0-5%, alkali metal oxide (Li ₂ O,
_{Na 2 O, K 2 O,} Rb 2 O, Cs 2 O) is 7-17%, alkali metal chlorides (LiCl, NaCl, KCl, RbCl , CsCl) is 0
~ 5%, alkaline earth oxides (MgO, CaO, SrO, Ba
O) is 0-5%, copper oxide (Cu ₂ O) and copper halide (CuC
l, CuBr, etc.) in the range of 0.5-2.5% and SnO in the range of 0-0.5%.
6% As ₂ O ₃ silicate glass having a composition which is 0-5%, the borosilicate glass can be exemplified.

Further, when converted to the following components by weight%, B ₂ O ₃ is 40 to 75%, SiO ₂ is 0 to 40%,
Al ₂ O ₃ 4-20%, alkali metal oxides (Li ₂ O, Na _{2
O, K 2 O, Rb 2} O, Cs 2 O) 1 to 15% alkali metal chloride (LiCl, NaCl, KCl, RbCl , CsCl) is 0-4
%, Alkaline earth oxides (MgO, CaO, SrO, BaO ) 0 to 15%, oxide (Cu ₂ O) and copper halide (CuCl, C
borate glass and borosilicate glass having a composition of 0.5 to 2.5% in total content with uBr and the like and SnO of 0 to 0.6%.

In order to produce glass having the above composition, carbonates, nitrates, hydroxides, halides and the like can be appropriately used as raw materials in addition to the above oxides and the like. However, since halogen is easily volatilized in the melting step, it is preferable to add a halogen compound to the glass batch in a slightly excessive amount than the equivalent of copper. After melting the glass batch having the above composition, the glass melt is cooled to room temperature to produce a glass containing copper and halogen.

The glass is heated to form a copper halide (eg, CuCl, CuF, CuBr, CuI, or C
uF _1-X Cl _x (mixed crystal such as 0 <X <1)) is precipitated. The heating temperature is preferably 650 to 850C. 65
If the temperature is lower than 0 ° C., it tends to take too much time to precipitate the copper halide in the glass. If the temperature exceeds 850 ° C., the particle size of the precipitated copper halide tends to increase, and the particle size is controlled by heating time. It becomes difficult.

The larger the size of the copper halide particles, the easier the subsequent stretching of the copper halide particles. However, if the size is too large, the loss due to scattering of the obtained polarizing glass increases. Therefore, the particle size of the precipitated copper halide particles is 50
It is preferably in the range of 300 nm. For that purpose, it is appropriate to heat in the above temperature range for 1 to 10 hours.

The obtained glass containing copper halide particles is drawn at a temperature at which the viscosity of the glass containing copper halide particles is 1 × 10 ⁸ to 1 × 10 ¹¹ poise, whereby the copper halide particles in the glass are drawn. The reason for setting the viscosity of the glass to 1 × 10 ⁸ to 1 × 10 ¹¹ poise is that if the viscosity is lower than 1 × 10 ⁸ poise, the drawn copper halide particles may return to the original spherical shape. If the viscosity is higher than 1 × 10 ¹¹ poise, the glass may be broken during stretching. The temperature at which the viscosity falls within the above range varies depending on the composition of the glass, and can be appropriately determined according to the composition of each glass.

The stretching is performed so that the aspect ratio of the copper halide particles in the obtained glass is from 8: 1 to 60: 1. The aspect ratio of the copper halide particles is from 8: 1 to 6
By setting the ratio to 0: 1, the aspect ratio of metal copper particles generated by reduction later can be set to 2: 1 to 15: 1. This is because when the copper halide particles are changed into copper particles by reduction, the volume shrinks by about 70%. However, glass containing copper halide particles having an aspect ratio in the above range does not show photochromic properties and hardly shows polarization characteristics.

Here, the elongation of the copper halide particles includes, for example, pulling, extruding, rolling, or pressing glass containing the copper halide particles. The aspect ratio of the copper halide particles can be controlled by changing the stretching conditions. When stretching by pulling, by changing the pulling conditions,
The shape of the sample obtained can also be controlled.
It is possible to obtain a sample having a required taper or a sample having a required constant width by changing the viscosity of the glass at the time of pulling, the pulling speed, and moving the overheating zone of the sample.

The stretching force varies depending on the viscosity of the glass and the stretching speed. For example, in the case of stretching, the stretching force can be 100 kg / cm ² in the above temperature range. Further, the drawn glass is preferably rapidly cooled to a temperature lower than the annealing point in order to prevent spheroidization of the copper halide particles.

The drawn glass is then subjected to a reduction treatment to reduce a part or all of the copper halide particles in the glass. However, the stretched glass is preferably formed into a desired shape by polishing the surface before the reduction treatment, if necessary.

In order to provide sufficient polarization characteristics, it is necessary to reduce at least a portion of the elongated copper halide particles in the glass to metallic copper. The reduction can be performed, for example, by heat-treating the glass in a hydrogen gas atmosphere. However, it is necessary to reduce copper halide particles while preventing them from re-spheroidizing, and since copper has three valence states (0, 1, and 2 valences), it is important to set reduction conditions, particularly temperature. is there. When the temperature is too low, re-spheroidization of the copper halide particles does not occur, but it takes too much time to obtain a reduced layer having a thickness necessary for obtaining good polarization characteristics. If the temperature is too high, a reduced layer of a required thickness can be obtained in a short time, but the viscosity of the glass becomes too low, and the re-spherical shape of the copper halide particles occurs. However, in anticipation of re-spheroidization, copper halide particles are stretched to a larger aspect ratio than in the case of reduction at a temperature at which re-spheroidization does not occur. It is also possible to reduce at a temperature and obtain a sufficiently thick reduction layer in a short time.

Although it varies depending on the composition of the glass, it is preferable to reduce at a temperature in the range of 350 to 550 ° C., preferably 375 to 475 ° C. for 30 minutes to 10 hours in order to give good polarization characteristics. By the above-described reduction treatment, copper halide particles in a range from the surface to about 1 to 120 μm are reduced. As a result, in glass having a relatively small thickness (glass having a thickness of about 240 μm or less), most of the copper halide particles in the glass are reduced, and a polarizing glass in which anisotropic metallic copper particles are dispersed is obtained. On the other hand, a glass having a relatively large thickness has a three-layer structure in which anisotropic copper metal particles are dispersed in the surface layer of the glass and unreduced anisotropic copper halide particles are dispersed therein. The above-mentioned reduction conditions are for the case where hydrogen gas is used as the reducing gas.
However, a reducing gas other than hydrogen gas can be used, and the reducing conditions in that case can be determined as appropriate.
Reducing gases other than hydrogen gas include, for example, CO-
CO ₂ gas and the like can be mentioned.

The polarization characteristics vary depending on the volume ratio of the copper particles in the glass, the size of the particles, and the thickness of the reduced layer, in addition to the aspect ratio of the copper particles. It also changes depending on the size and volume ratio of the copper halide particles in the unreduced layer and the thickness of the unreduced layer. The volume ratio of copper particles is determined from the product of the volume of one stretched copper particle and the particle density (number per unit volume) observed by a transmission electron microscope. The volume ratio of the copper particles is a factor that affects the magnitude of the absorption coefficient. If the volume ratio is less than 1 × 10 ⁻⁴ , the thickness of the reduction layer must be increased to obtain sufficient polarization characteristics. Takes time. Conversely, if the volume ratio of the copper particles is larger than 1 × 10 ^-2 , the reduced layer may be thin, but the scattering by the copper halide particles in the unreduced layer also increases, so that the insertion loss increases, which is not preferable. . Although the content of the copper halide is related to the heat treatment conditions, it affects the volume ratio of the copper particles. Therefore, the content of 0.5 to 2.5% by weight is optimal.

The copper-containing polarizing glass of the present invention does not show photochromic properties. Further, since at least a part of the copper halide is reduced to metallic copper, it exhibits a polarization characteristic of 30 dB or more at a wavelength of 1.3 to 1.55 microns without irradiation with short wavelength light. Further, the polarizing glass according to the present invention has a broad absorption and is used in optical communication at 1.31 μm.
A large extinction ratio can be simultaneously provided in both the wavelength ranges of m and 1.55 μm.

Since the present invention relates to a polarizing glass that transmits only linearly polarized light in one direction, the polarized light will be described here. Linearly polarized light refers to light whose electric field vector direction is constant. As shown in FIG. 7, light can be generally considered to be composed of two components 1a and 1b whose electric field directions are perpendicular to each other. Here, when the fine metal particles 4 having an anisotropic shape are present in the glass, the light has a component whose electric field direction is parallel to the short axis of the metal particles (lateral light 1b) and a component parallel to the long axis. (Vertical light 2b) causes a difference in absorption. The absorption of the component parallel to the long axis and the absorption of the component parallel to the short axis can be measured by a spectrophotometer as absorbance. As a result of a large difference in absorbance between the component parallel to the short axis (horizontal light) and the component parallel to the long axis (vertical light), a polarizer of a type that transmits only one-way linearly polarized light is obtained.

The optical isolator of the present invention includes a Faraday rotator and at least one polarizer as components, and preferably includes a Faraday rotator, two polarizers and a magnet as components, and the polarizer according to the present invention. Using a copper-containing polarizing glass.

[0030]

The present invention will be described below with reference to examples.

Example 1 A glass having the composition (1) shown in Table 1 was used as a raw material for SiO.
_{2, H 3 BO 3, Al} (OH) 3, Na 2 CO 3, NaCl, AlF 3, CuC
l, SnO and the like were put into a 3 liter platinum crucible and melted at about 1450 ° C, then poured into a graphite mold, molded and cooled to room temperature. This glass was heat-treated at 800 ° C. for 3 hours to precipitate CuCl particles of about 150 nm. This glass did not show photochromic properties. This glass is cut out to a size of 5 × 10 × 100 mm, and the temperature is 60, which is a temperature at which the viscosity becomes about 1 × 10 ⁹ poise.
Heat to 0 ° C and pull at a speed of 100mm / min, 200kg
The film was stretched under a load of / cm ² . As a result, the copper halide grains change to a shape of about 60 × 600 nm (aspect ratio 10: 1), they are arranged in almost one direction, and the density of the copper halide grains is about 2.5 × 10 ¹² / cm ³ was confirmed by observation with a transmission electron microscope. The volume ratio of the copper halide particles was about 4.4 × 10 ⁻³ .

After polishing this glass to a thickness of about 1 mm,
By reducing in a hydrogen gas at 00 ° C. for 1 hour, a glass having the polarization characteristics shown in Table 1 was obtained. The thickness of the reduced layer of glass was about 30 μm. By the reduction, the copper halide particles were changed into copper particles having an aspect ratio of about 2 to 3 (on average, copper particles having a size of about 50 × 125 nm (aspect ratio 2.5: 1)) and hollow portions due to volume shrinkage accompanying the reduction. . The copper particles were deposited mainly at both ends of the portion occupied by the copper halide particles, and had a shape close to a cylinder. The volume ratio of copper particles was calculated to be about 1.1 × 10 ⁻³ .

With respect to this glass, when the particles are oriented parallel to the polarized light (1a (before reduction), 2a (after reduction)) and vertically (1b (before reduction)),
2b (after reduction)) was measured. The results are shown in FIGS. As shown in FIG. 1 (before reduction) and FIG. 2 (after reduction), a remarkable change was observed in the transmittance of the glass before and after reduction, and metallic copper was confirmed in the glass surface layer by ESCA. It was confirmed that at least a part of the copper halide particles in the surface layer was reduced to metallic copper. The measurement results are for a sample without an antireflection film.

Example 2 A glass was prepared in the same manner as in Example 1 with respect to the glass having the composition shown in Table 1 (2). This glass was heat-treated at 750 ° C. for 5 hours to precipitate copper halide particles having a diameter of about 250 nm, and then cut out to a size of 5 × 10 × 100 mm.
Speed 10 while heating to 0 ° C (viscosity 3 × 10 ⁸ poise)
The film was pulled at 0 mm / min and stretched under a load of 300 kg / cm ² .
As a result, 100 × 980 nm (aspect ratio 10: 1)
And it was confirmed by a transmission electron microscope that it was oriented in almost one direction. The CuCl particle density of this glass was about 1 × 10 ¹² / cm ³ , and the copper halide particle volume ratio was calculated to be about 8.2 × 10 ^-3 .

As a result of reducing the glass in a hydrogen atmosphere at 470 ° C. for 4 hours, a polarizing glass having an extinction ratio shown in Table 1 was obtained. The thickness of the reduced layer of glass was about 40 μm. Copper halide particles have an aspect ratio of 2 due to reduction.
〜3 copper particles (on average, copper particles having a size of about 75 × 190 nm (aspect ratio 2.5: 1)) and changed into hollow portions due to volume shrinkage accompanying reduction. The copper particles were deposited mainly at both ends of the portion occupied by the copper halide particles, and had a shape close to a truncated cone. The volume ratio of copper particles is about 2.1 × 1
0 ^-3 and were calculated.

Example 3 A glass having the composition (3) shown in Table 1 was used as a raw material for SiO.
₂ , H ₃ BO ₃ , Al (OH) ₃ , Na ₂ CO ₃ , AlF ₃ , CuCl, SnO, etc., put in a 3 liter platinum crucible, and put about 1450
After melting at ℃, it was poured into a graphite mold, molded, and cooled to room temperature to obtain a glass. 800 ° C
For 3 hours to precipitate copper halide particles of about 150 nm. This glass did not show photochromic properties. This glass is cut into a size of 5 × 10 × 100 mm, and the temperature is 60 at which the viscosity becomes about 10 ⁹ poise.
Heat to 0 ° C and pull at a speed of 100mm / min, 200kg
/ Cm ² . As a result, the copper halide grains change to a shape of about 40 × 2000 nm (aspect ratio 50: 1), they are oriented in almost one direction, and the density of the copper halide grains is about 2.5 × 10 ¹² / cm ³ was confirmed by observation with a transmission electron microscope. The volume ratio of the copper halide particles was about 4.4 × 10 ⁻³ .

This glass was polished to a thickness of about 0.5 mm and then reduced in hydrogen gas at 500 ° C. for 1 hour to obtain a glass having the polarization characteristics shown in Table 1. The thickness of the reduced layer of glass was about 30 μm. Cu by reduction
The Cl particles changed to copper particles having an aspect ratio of about 5 to 14: 1 (on average, copper particles having a size of about 35 × 350 nm (aspect ratio 10: 1)) and hollow portions due to volume shrinkage accompanying reduction. The copper particles were deposited mainly at both ends of the portion occupied by the CuCl particles, and had a shape close to a cylinder. The volume ratio of copper particles was calculated to be about 1.1 × 10 ⁻³ .

Example 4 A glass was prepared in the same manner as in Example 3 for the glass having the composition (4) shown in Table 1. This glass was heat-treated at 700 ° C. for 5 hours to precipitate copper halide particles having a diameter of about 170 nm, cut out into a size of 5 × 10 × 100 mm, and heated to a temperature of 550 ° C. (viscosity 7 × 10 ⁸ poise). The film was stretched at a speed of 150 mm / min and stretched under a load of 200 kg / cm ² . As a result, 60 × 1400 nm (aspect ratio 2)
It was confirmed by a transmission electron microscope that the film was deformed to 3: 1) and oriented substantially in one direction. The particle density of this glass is about 2 × 10 ¹² / cm ³ and the particle volume ratio is about 5.1 ×
It was calculated to be 10 ^-3 .

As a result of reducing the glass in a hydrogen atmosphere at 420 ° C. for 4 hours, a polarizing glass having an extinction ratio shown in Table 1 was obtained. The thickness of the reduced layer of glass was about 20 μm. Copper halide particles have an aspect ratio of 2 due to reduction.
８8: 1 copper particles (about 50 × 230 nm on average)
(Copper particles with an aspect ratio of 4.5: 1) and a cavity due to volume shrinkage accompanying reduction. The copper particles were deposited mainly at both ends of the portion occupied by the copper halide particles, and had a shape close to a cylinder. The volume ratio of copper particles is about 1.3 ×
It was calculated to be 10 ^-3 .

Example 5 A glass having the composition (5) shown in Table 1 was produced in the same manner as in Example 3. This glass is heat-treated at 750 ° C. for 3 hours to precipitate copper halide particles having a diameter of about 120 nm, cut out into a size of 4 × 10 × 180 mm, and heated to a temperature of 580 ° C. (viscosity 2 × 10 ⁹ poise). The film was stretched at a speed of 150 mm / min and stretched under a load of 300 kg / cm ² . As a result, it was confirmed by a transmission electron microscope that the film was deformed to about 35 × 1300 nm (aspect ratio 37: 1) and was oriented in almost one direction. The particle density of this glass is about 7 × 10 ¹² / cm ³ and the particle volume ratio is about 6.3 ×
It was calculated to be 10 ^-3 .

As a result of reducing the glass in a hydrogen atmosphere at 450 ° C. for 3 hours, a polarizing glass having an extinction ratio shown in Table 1 was obtained. The thickness of the reduced layer of glass was about 20 μm. The copper halide particles have an aspect ratio of 3 due to reduction.
〜１０10: 1 copper particles (about 35 × 250n on average)
m (copper particles having an aspect ratio of 7: 1) and a cavity portion due to volume shrinkage accompanying reduction. The copper particles were deposited mainly at both ends of the portion occupied by the copper halide particles, and had a shape close to an ellipsoid. The volume ratio of copper particles is about 1.6 ×
It was calculated to be 10 ^-3 .

Example 6 A glass having the composition (6) shown in Table 2 was produced in the same manner as in Example 3. This glass was heat-treated at 700 ° C. for 1 hour to precipitate copper halide particles having a diameter of about 70 nm, and then cut into a size of 4 × 10 × 220 mm.
While heating to 00 ° C. (viscosity 2 × 10 ⁹ poise), the film was pulled at a speed of 150 mm / min and stretched under a load of 400 kg / cm ² . As a result, about 20 × 750 nm (aspect ratio 3
It was confirmed by a transmission electron microscope that it was deformed to 8: 1) and oriented in almost one direction. The particle density of this glass is about 2 × 10 ¹³ / cm ³ and the particle volume ratio is about 3.6 × 1
0 ^-3 and were calculated.

As a result of reducing the glass in a hydrogen atmosphere at 400 ° C. for 3 hours, a polarizing glass having an extinction ratio shown in Table 2 was obtained. The thickness of the reduced layer of glass was about 20 μm. Copper halide particles have an aspect ratio of 2 due to reduction.
Copper particles of about 10: 1 (on average about 20 × 120 n
m (copper particles having an aspect ratio of 6: 1) and a cavity due to volume shrinkage accompanying reduction. The copper particles were deposited mainly at both ends of the portion occupied by the copper halide particles, and had a shape close to an ellipsoid. The volume ratio of copper particles is about 9 × 10
^-4 was calculated.

Example 7 A glass having the composition (7) shown in Table 2 was prepared in the same manner as in Example 3. This glass is heat-treated at 740 ° C. for 1 hour to precipitate copper halide particles having a diameter of about 110 nm, cut into a size of 4 × 10 × 220 mm, and heated to a temperature of 610 ° C. (viscosity of 1 × 10 ⁹ poise). The film was stretched at a speed of 100 mm / min and stretched under a load of 200 kg / cm ² . As a result, it was confirmed by a transmission electron microscope that it was deformed to about 30 × 1000 nm (aspect ratio: 33: 1) and oriented in almost one direction. The particle density of this glass is about 6 × 10 ¹² / cm ³ and the particle volume ratio is about 4.2 ×
It was calculated to be 10 ^-3 .

This glass was subjected to a reduction treatment in a hydrogen atmosphere at 420 ° C. for 4 hours. As a result, a polarizing glass having an extinction ratio shown in Table 2 was obtained. The thickness of the reduced layer of glass was about 30 μm. Copper halide particles have an aspect ratio of 2 due to reduction.
８8: 1 copper particles (about 30 × 150 nm on average)
(Copper particles having an aspect ratio of 5: 1) and a volume change due to volume shrinkage accompanying reduction. The copper particles were deposited mainly on both ends of the portion occupied by the CuCl particles, and had a shape close to an ellipsoid. The volume ratio of copper particles was calculated to be about 1.1 × 10 ⁻³ .

In this glass, when the particles are oriented parallel to the polarized light (3a (before reduction), 4a (after reduction)) and vertically (3b (before reduction)),
4b (after reduction)) was measured. The results are shown in FIGS. As shown in FIG. 3 (before reduction) and FIG. 4 (after reduction), a remarkable change was observed in the transmittance of the glass before and after the reduction, and metallic copper was confirmed in the glass surface layer by ESCA. It was confirmed that at least a part of the copper halide particles in the surface layer was reduced to metallic copper. Note that the measurement results were obtained for a sample having no antireflection film.

Example 8 A glass having the composition of (8) in Table 2 was used as a raw material for SiO ₂ and H ₂ .
₃ BO ₃ , Al (OH) ₃ , Na ₂ CO ₃ , NaCl ₃ , CuCl 2, SnO, etc., were put into a 3 liter platinum crucible, melted at about 1400 ° C., and poured into a graphite mold to be molded.
The glass is heat-treated at 750 ° C. for 4 hours,
5 × 10 × 10 after the precipitation of copper halide particles
Cut out to a size of 0 mm, temperature 620 ° C (viscosity 1 × 10
While heating to ⁹ poise, the film was pulled at a speed of 150 mm / min and stretched under a load of 200 kg / cm ² . As a result, 60
It was confirmed by a transmission electron microscope that it was deformed to × 960 nm (aspect ratio 16: 1) and oriented in almost one direction. The particle density of this glass was about 3 × 10 ¹² / cm ³ and the particle volume ratio was calculated to be about 5.3 × 10 ^-3 .

The glass was reduced in a hydrogen atmosphere at 500 ° C. for 4 hours. As a result, a polarizing glass having an extinction ratio shown in Table 2 was obtained. The thickness of the reduced layer of glass is about 50 μm
Met. By reduction, the CuCl particles have an aspect ratio of 2 to 4:
About 1 copper particle (average copper particle of about 50 × 150 nm (aspect ratio 3: 1)) and a cavity portion due to volume shrinkage accompanying reduction. The copper particles were deposited mainly at both ends of the portion occupied by the copper halide particles, and had a shape close to a cylinder. The volume ratio of copper particles was calculated to be about 1.4 × 10 ⁻³ .

Example 9 A glass was prepared in the same manner as in Example 8 for the glass having the composition shown in Table 9 (9). This glass was heat-treated at 800 ° C. for 1 hour to precipitate copper halide particles having a diameter of about 140 nm, and then cut out to a size of 5 × 10 × 100 mm.
While heating to 0 ° C (viscosity 2 × 10 ⁹ boise), the speed 8
The film was pulled at 0 mm / min and stretched under a load of 250 kg / cm ² . As a result, 50 × 1000 nm (aspect ratio 20:
It was confirmed by a transmission electron microscope that the film was deformed in 1) and oriented substantially in one direction. The particle density of this glass is about 6 × 10 ¹² / cm ³ and the particle volume ratio is about 8.6 × 10 ^-3.
It was calculated.

As a result of reducing the glass in a hydrogen atmosphere at 500 ° C. for 4 hours, a polarizing glass having an extinction ratio shown in Table 2 was obtained. The thickness of the reduced layer of glass was about 50 μm. Copper halide particles have an aspect ratio of 2 due to reduction.
About 6: 1 copper particles (about 42 × 170 nm on average)
(Aspect ratio of 4: 1 copper particles) and volume reduction due to volume shrinkage due to reduction. The copper particles were deposited mainly at both ends of the portion occupied by the copper halide particles, and had a shape close to a cylinder. The volume ratio of copper particles is about 2.2 × 10
It was calculated as ^-3 .

Example 10 Glass was produced in the same manner as in Example 3 for glass having the composition of (10) in Table 2. This glass was heat-treated at 750 ° C. for 1 hour to precipitate copper halide particles having a diameter of about 110 nm. The glass having a diameter of about 50 mm and a length of about 50 mm obtained by processing was extruded into a rod having a diameter of 5 mm at a pressure of 750 kg / cm ² while being heated at a temperature of 610 ° C. (viscosity of 8 × 10 ⁸ boas). As a result, the copper barogenide particles in the glass are about 30
It was confirmed by a transmission electron microscope that it was deformed to × 1000 nm (aspect ratio 33: 1) and oriented in almost one direction. From this electron micrograph, the particle density of this glass was about 6.2 × 10 ¹² / cm ³ and the particle volume ratio was about 4.
It was calculated to be 3 × 10 ⁻³ .

This glass was subjected to a reduction treatment in a hydrogen atmosphere at 450 ° C. for 3 hours. As a result, a polarizing glass having an extinction ratio shown in Table 2 was obtained. The thickness of the reduced layer of glass was about 20 μm. Observation with a transmission electron microscope revealed that the copper particles were precipitated at both ends of the portion mainly occupied by the copper halide particles due to reduction. The average size of the copper particles was about 25 × 180 nm (aspect ratio 7: 1), and the volume ratio of the copper particles was calculated to be about 1.1 × 10 ⁻³ .

For the obtained glass,
If the particles are oriented parallel (5a (before reduction), 6a
(After reduction)) and in the case of vertical orientation (5b (before reduction), 6b (after reduction)), the absorbance was measured. The results are shown in FIGS. As shown in FIG. 5 (before reduction) and FIG. 6 (after reduction), a remarkable change was observed in the transmittance of the glass before and after the reduction, and metallic copper was confirmed in the glass surface layer by ESCA. It was confirmed that at least a part of the copper halide particles in the surface layer was reduced to metallic copper. Note that the measurement results were obtained for a sample having no antireflection film.

Example 11 A glass having the composition of (11) in Table 2 was melted and produced in the same manner as in Example 3. This glass was heat-treated at 750 ° C. for 2 hours to precipitate copper halide particles having a diameter of about 150 nm. About 50mm diameter 50mm length of the glass obtained by machining, extruded into rods of diameter 5mm at a pressure of 600 Kg / cm ² while heating to a temperature 640 ° C. (viscosity 3 × 18 ⁸ poise). As a result, the copper halide particles in the glass are about 4
It was confirmed by a transmission electron microscope that the film was elongated to 5 × 1100 nm (aspect ratio 24: 1) and arranged in almost one direction. From this electron micrograph, the copper halide particle density was calculated to be about 2.5 × 10 ¹² / cm ² , and the volume ratio of the copper halide particles was calculated to be about 4.4 × 10 ⁻³ . As a result of heat-treating this glass at 470 ° C. for 3 hours in a hydrogen atmosphere, a glass having polarization characteristics shown in Table 2 was obtained. The thickness of the reduced layer of glass was about 20 μm. Observation with a transmission electron microscope revealed that the heat treatment (reduction treatment) caused the copper particles to precipitate at both ends of the portion mainly occupied by the copper halide particles. Its size is about 40 × 220 nm on average (aspect ratio 5.5:
1), the volume ratio was about 1.2 × 10 ⁻³ .

[0055]

[Table 1]

[0056]

[Table 2]

As shown in the above examples, when the volume of the stretched copper halide particles before the reduction is large, the copper particles formed after the reduction tend to have a shape close to a truncated cone. When the volume of the copper halide particles is small, the copper particles formed after the reduction tend to have a shape close to a column or an ellipsoid. Depending on the shape of the resulting copper particles, the position of absorption when the polarization plane and the vertical axis of the particles are parallel tends to change, and the shape near the truncated cone tends to absorb more than the shape near the ellipsoid. Tended to move to longer wavelengths. In addition, the particle density during the above-mentioned operation was determined by counting the number of copper halide particles appearing in a certain area of a TEM (transmission electron microscope) image, and assuming that the thickness of the TEM sample was 300 nm.

The volume ratio of copper particles in the reduction layer was calculated as follows. A = Vcucl × d × 0.25 A: Volume ratio of copper particles Vcucl: Average volume of the portion occupied by one copper chloride particle d: Particle density (number of copper chloride particles present per unit volume) Vcucl The vertical length of this portion was set to 1, the width was set to w, and an ellipsoid was approximated to obtain Vcucl = π × w ² × 1/6. d is the number of portions (consisting of copper particles and portions generated by reduction) occupied by copper chloride particles in a fixed area of a TEM (transmission electron microscope) image, and the thickness of the TEM sample is set to 300 nm. It was determined assuming that: The coefficient multiplied by 0.25 at the end is the result of theoretical examination and observation.
This is because copper particles having a volume 0.25 times the volume occupied by one copper chloride are generated.

Definition and Measurement Method of Extinction Ratio The transmittance when the major axis of the particle is perpendicular to the polarization plane is defined as T⊥%, and the transmittance when the major axis of the particle is parallel to the polarization plane is defined as T‖%. The extinction ratio is defined as in the following equation. Extinction ratio = 10 × log (T⊥% / T‖%) The transmittance was measured using the apparatus shown in FIG. In FIG. 9, 21 is a semiconductor laser used as a light source, 22 is a Glan-Thompson prism, 23 is a sample, 24 is a sample holder, and 25 is a power meter. The 24 sample holders can be rotated around a hole through which light passes. Light emitted from 21 passes through 22 and becomes linearly polarized light. In the absence of a sample 23 to measure the power of the light passing through the hole in the holder, which is referred to as W _0. Next, sample 2
3 and rotate the holder, the maximum power of light W
Measure _MAX , minimum power W _MIN . T⊥% = (W _MAX / W ₀ ) × 100 T‖% = (W _MIN / W ₀ ) × 100

Example 12 A glass containing CuCl particles, which was prepared and stretched in the same manner as in Example 1, was polished to a thickness of 0.1 mm, and then reduced in the same manner as in Example 1 to obtain a polarizing glass of the present invention. Obtained. A commercially available magnetic garnet film 13 (manufactured by TOKIN) formed by the polarizing glasses 11 and 12 and a liquid layer epitaxy method;
FIG. 8 shows an example of an optical isolator for 1.31 μm, which was experimentally produced by combining Sm-Co based magnets 14a and 14b. The thicknesses of the polarizing glasses 11 and 12 were 0.1 mm, the thickness of the magnetic garnet film 13 was about 0.4 mm, and they were heat-sealed with powdered glass (the thickness of each of the bonding glasses was about 0.05 mm). Needless to say, an adhesive is also possible. This isolator has an effective beam diameter of LD (1.
2 mm), the distance between the polarizers (0.7 mm) is shorter. The extinction ratio when this polarizer was irradiated with an LD having a wavelength of 1.3 μm was 30 dB.

Example 13 An isolator was produced in the same manner as in Example 12, except that the polarizing glass was changed from that of Example 1 to a polarizing glass having a thickness of 0.1 mm, which was produced in the same manner as in Example 7. 1.3 wavelength
The extinction ratio when illuminating this polarizer with a μm LD was 48.
dB.

[0062]

As described above in detail, according to the method for producing a polarizing glass of the present invention, the glass on which the copper halide is precipitated is stretched, and the stretched glass is treated in a reducing atmosphere. The amount of reduction of the copper halide particles and the aspect ratio of the copper halide particles can be easily controlled.
Furthermore, the resulting polarizing glass has a high extinction ratio in the infrared region.

The optical isolator using the polarizing glass of the present invention can be thinner than the effective beam diameter and has a high extinction ratio in the infrared region, so that it can be preferably used as an isolator for optical communication.

Further, since the optical isolator using the polarizing glass of the present invention is thin, it can be used by being embedded in a single mode fiber.

[Brief description of the drawings]

FIG. 1 shows the transmittance of the glass (1 mm thick) of Example 1 before reduction (a).

FIG. 2 shows the transmittance of the glass of Example 1 (1 mm thick) after reduction (b).

FIG. 3 shows the transmittance of the glass (0.5 mm thickness) of Example 7 before reduction (a).

FIG. 4 shows the transmittance of the glass (0.5 mm thick) of Example 7 after reduction (b).

FIG. 5 shows the transmittance of the glass (0.5 mm thick) of Example 13 before reduction (a).

FIG. 6 shows the transmittance of the glass (0.5 mm thick) of Example 13 after reduction (b).

FIG. 7 is an explanatory diagram of polarization development using polarizing glass.

FIG. 8 shows polarizing glasses 11 and 12 of the present invention, a commercially available magnetic garnet film 13 (manufactured by Tokin), and a Sn—Co-based magnet 14
FIG. 1 shows an explanatory diagram of a 1.31 micron optical isolator which was experimentally produced by combining a and 14b.

FIG. 9 is a schematic explanatory view of a transmittance measuring device.

──────────────────────────────────────────────────の Continuing on the front page (51) Int.Cl. ⁶ Identification code FI G02B 5/30 G02B 5/30 (72) Inventor Kokei Kura 2-7-5 Nakaochiai, Shinjuku-ku, Tokyo Hoya Corporation (56) References JP-A-4-325423 (JP, A) JP-A-56-169140 (JP, A) JP-A-2-248341 (JP, A)

Claims (10)

(57) [Claims] 1. A polarizing glass comprising shape-anisotropic particles oriented and dispersed at least in a surface layer portion of a glass substrate, wherein the glass substrate is composed of silicate glass, borate glass and borosilicate glass. Wherein the shape-anisotropic particles are metallic copper particles. 2. The metal copper particles having an aspect ratio of 2: 1 to 1
The polarizing glass according to claim 1, wherein the ratio is 5: 1. 3. The polarized light according to claim 1, wherein an extinction ratio to one or both of light in a wavelength region having a central wavelength of 1.31 μm and light in a wavelength region having a central wavelength of 1.55 μm is 30 dB or more. Glass. 4. The metal copper particles have a vertical length of 50 to 1200.
and a width of 12 to 150 nm.
4. The polarizing glass according to any one of 3. 5. When converted to the following components by weight%, SiO ₂ is 48 to 65%, B ₂ O ₃ is 13 to 33%, and Al ₂
O ₃ is 6 to 13%, AlF ₃ is 0 to 5%, alkali metal oxide is 7 to 17%, alkali metal chloride is 0 to 5%, alkaline earth oxide is 0 to 5%, copper oxide and the content of the copper halide is 0.5 to 2.5%, SnO is 0~0.6%, as ₂ O ₃ is 0
The polarizing glass according to any one of claims 1 to 4, having a composition of 5%. 6. When converted to the following components by weight%, B ₂ O ₃ is 40 to 75%, SiO ₂ is 0 to 40%, and Al ₂ O ₃
4-20%, alkali metal oxides 1-15%, alkali metal chlorides 0-4%, alkaline earth oxides 0-0
15%, the content of copper oxide and copper halide is 0.5 to 2.5
%, SnO having a composition of 0 to 0.6%.
The polarizing glass according to any one of the above. 7. A step of heating a glass selected from the group consisting of silicate glass, borate glass and borosilicate glass containing copper and halogen to precipitate copper halide particles in the glass; Stretching the copper halide particle-containing glass at a temperature at which the viscosity of the obtained copper halide particle-containing glass is 1 × 10 ⁸ to 1 × 10 ¹¹ poise, and removing one of the copper halide particles in the stretched glass. A method for producing a polarizing glass, comprising a step of reducing part or all of the glass substrate, wherein shape-anisotropic metallic copper particles are oriented and dispersed in at least the surface layer of the glass substrate. 8. The glass containing copper and halogen has a SiO ₂ content of 48 to 48 when converted to the following components by weight%.
65% B ₂ O ₃ is 13 to 33% Al ₂ O ₃ is 6-13%,
AlF ₃ is 0 to 5%, alkali metal oxide is 7 to 17%,
0-5% of alkali metal chloride, 0-5% of alkaline earth oxide, 0.5-2.5% of copper oxide and copper halide
%, The process according to claim 7 having the composition SnO is 0 to 0.6%, As ₂ O ₃ is 0 to 5%. 9. The glass containing copper and halogen has a B ₂ O ₃ of 40 to 40 when converted to the following components by weight%.
75% SiO ₂ is 0 to 40% Al ₂ O ₃ is 4-20%, alkali metal oxides from 1 to 15% alkali metal chloride 0 to 4% alkaline earth oxides 0-15 %, Content of copper oxide and copper halide is 0.5 to 2.5%, SnO is 0 to 0.6%
%. 10. An optical isolator using the polarizing glass according to claim 1. Description: