JPH1020116A - Polarizing element and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate the adjustment of the wavelengths of light of a polarizing element constituted by laminating many dielectric substance layers dispersed with metallic particles having anisotropy in a dielectric substance on one main surface of a dielectric substrate having translucency and to miniaturize the element by forming the dielectric substance layers in such a manner that the respective layers thereof vary in thickness from each other. SOLUTION: A laminate P is a laminate before the polarizing element is formed by laminating the many dielectric substance layers dispersed with the metallic particles having the anisotropy in the dielectric substance on the one main surface of the dielectric substrate 1. Namely, a stage for depositing and forming metallic fine particulates on the dielectric substance film forming surface including the dielectric substance substrate 1 consisting of glass, a stage for flocculating the metallic fine particulates and forming the metallic particles on the dielectric substance film forming surface by heating to a temp. lower than the glass softening point and a stage for forming the dielectric substance layers in the form of the films are executed. The metallic layer 2(1) consisting of the metallic fine particulates, the dielectric substance layers 3(1)..., the metallic layer 2(n-1), the dielectric substance layer 3(n-1), the metallic layer 2(n) and the dielectric substance layer 3(n) are laminated on the substrate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a multi-layered structure in which, for example, a metal layer and a dielectric layer are alternately formed on at least one principal surface of a light-transmitting dielectric substrate. The present invention relates to a polarizing element obtained by stretching in the direction of the main surface of a body substrate.

[0002]

2. Description of the Related Art Conventionally, a polarizing prism represented by a Glan-Thompson prism composed of a crystal having a large birefringence, a PBS (polarizing beam splitter) for separating a polarized light component using Brewster conditions, In addition, a polarizing film or the like in which a polymer is oriented in one direction occupies the mainstream of the polarizing element, and such a polarizing element has a function of transmitting only light in a specific vibration direction and absorbing or reflecting other light. Have.

Hitherto, various configurations of polarizing elements have been studied, and some of them have been put to practical use, and are widely used in, for example, optical sensors and optical isolators. In particular, recently, the necessity of a small-sized, high-performance, and inexpensive polarizing element has been increasing in fields such as optical communication and an optical disk, and development has been actively carried out.

[0004] Such high-performance polarizing elements include (1) low insertion loss and high transmittance, (2) high extinction ratio, (3) miniaturization is possible, (4). Although it is mainly required that mass production is possible and that it is inexpensive, none of the conventional polarizing elements can satisfy all of the required items.

[0005] In order to satisfy such a demand, an island-shaped metal thin film layer and a transparent glass layer are alternately laminated to form a laminate, which is then stretched to impart anisotropy. A method of forming an insulated metal thin film has been proposed (see, for example, the 1990 IEICE Fall National Convention, Proceedings, C-212).

According to this proposal, a metal thin film layer and a glass layer having an island-like structure are repeatedly and alternately stacked to form a laminate, and the laminate is stretched in a direction perpendicular to the laminating direction, so that the shape and distribution of the metal islands are improved. Can be given structural anisotropy, and the resonance absorption characteristics can have polarization dependence. Further, since light is incident perpendicularly to the lamination surface and used, the length (thickness) of the polarizing element in the incident direction can be short, so that there is an advantage that a large-diameter element can be easily manufactured. Further, by laminating the metal thin film layer and the glass layer, the polarization characteristics are greatly improved.

Here, the requirements for the metal material used for the metal thin film layer are to have high conductivity and to facilitate physical vapor deposition. On the other hand, the material used for the glass layer needs to have a softening point equal to or lower than the melting point of the metal thin film material for the following reasons. That is, in the stretching process, the glass layer is heated to a temperature equal to or higher than the annealing point and equal to or lower than the softening point, and is elongated in a direction parallel to the glass layer.

However, in the case of a polarizing element in which a metal thin film having an anisotropic structure having the above-mentioned anisotropy is formed and the resonance absorption characteristic has polarization dependency, only a light of a specific wavelength is polarized. However, only those having poor versatility, such as limitations on the wavelength used, could be obtained. Also, it was not easy to adjust the wavelength of the light to be polarized.

Therefore, the present invention provides a very excellent polarizing element which does not limit the wavelength of light used, easily adjusts the wavelength of light to be polarized (absorbed), and can be miniaturized, and a method of manufacturing the same. The purpose is to do.

[0010]

According to a first aspect of the present invention, there is provided a polarizing element comprising metal particles having anisotropy in a dielectric on at least one main surface of a dielectric substrate having a light transmitting property. A polarizing element comprising a large number of dielectric layers in which is dispersed, wherein the thickness of each of the dielectric layers is different from each other.

The thickness of each layer except the uppermost layer of the dielectric layer is formed so as to be gradually thicker or thinner than the layer located on the dielectric substrate side.

Here, only the uppermost layer is formed so that the uppermost dielectric layer before the thermoplastic deformation is thicker than the other dielectric layers so as to cope with surface polishing after thermoplastic deformation and thermoplastic deformation other than stretching. May be. By thickening the top layer in this way, it is possible to withstand processing such as polishing after thermoplastic deformation, and it is also possible to select a method other than stretching, which is simple and high in mass productivity, in selecting thermoplastic deformation. Become. In order to increase the thickness of the uppermost layer, a method of extending the film formation time when forming a thin film and forming a thick film as it is, or a thick film method such as a dip coating or a spin coating method after laminating a multilayer film is usually performed. , A thick film having the same composition as the dielectric thin film may be newly formed by a method called a sol-gel method.

Further, the method of manufacturing a polarizing element of the present invention comprises laminating a plurality of dielectric layers in which metal particles having anisotropy are dispersed in a dielectric, on a dielectric substrate having a light transmitting property. A method for manufacturing a polarizing element, comprising: laminating a plurality of metal layers and dielectric layers alternately on at least one main surface of a dielectric substrate, and changing the thickness of each of the dielectric layers to each other. A multilayer body, and then heating and softening and stretching the dielectric substrate to disperse anisotropic metal particles in the dielectric.

In this manner, by changing the thickness of each of the dielectric layers laminated on the substrate, the wavelength characteristic can be adjusted by utilizing the difference in the resonance absorption characteristics of each layer. . Also, by gradually increasing the thickness of the dielectric layer from the first layer to the uppermost layer of the laminate, or by gradually decreasing the thickness from the first layer to the uppermost layer, the absorption wavelength of each layer is different. , It is possible to broaden the wavelength characteristics as a whole.

Hereinafter, the reason will be described. In a polarization element with resonance-dependent absorption characteristics, the conduction electrons in a metal particle receive a force from the electric field when a uniform electric field with the same magnitude and direction is applied everywhere. Move while being restricted to the shape of.

As a result, when the incident light passes through the metal particles, the conduction electrons are shaken by the oscillating electric field. As the incident light continues to impinge on the metal particles, the conduction electrons, on the one hand, are shaken by the oscillating electric field and, on the other hand, try to be stopped by the electrical resistance, and continue to oscillate at an amplitude that finally reaches equilibrium.

At this time, the electrons oscillating while receiving the electric resistance emit heat by Joule loss. The energy of the vibration is changed to heat and the vibration is attenuated as it is, but the vibration continues because the energy of the vibration is constantly supplied from the incident light.

The energy of the incident light is partially converted to the vibrational energy of conduction electrons, which are then released as Joule heat. As a result of transmitting the energy of the incident light to the conduction electrons, the energy of the incident light after passing through the metal particles is reduced as compared with before the light hits the metal particles. Therefore, passing through the metal particles weakens the incident light.

However, since the incident light of all wavelengths does not decrease at the same rate, when the incident light having the same intensity at all wavelengths hits the metal particles, the incident light of the wavelength that increases the amplitude of the conduction electrons is applied. Light loses as much energy as light. That is, incident light having a wavelength that causes resonance with the plasma oscillation of the conduction electrons loses the most energy.

That is, when the incident light of various wavelengths, in other words, the incident light of various frequencies hits the metal particles, the incident light of the frequency equal to the plasma frequency loses the most energy, and the attenuation becomes severe. Even if the frequency is not exactly equal to the frequency of the plasma, a large energy reduction occurs when the frequency is close to it.

The above-described phenomenon that occurs in the metal particles occurs similarly even when the metal particles have a specific shape having anisotropy (for example, an ellipsoidal shape or a cylindrical shape). At that time, a unique polarization occurs due to the shape of the metal particle. For example, in the case of a metal particle having a long axis length and a short axis length, for example, the long axis direction and the short axis direction (the Y axis direction and the X axis direction of the dielectric film laminate) Respectively), and resonance vibration is caused for incident light having different specific wavelengths, and resonance absorption of light occurs in each direction. At this time, it is possible to have a function as a polarizing element due to the difference in the amount of absorption between the polarization component in the major axis direction and the polarization component in the minor axis direction of the incident light incident on the metal particles.

Therefore, by changing the film thickness of each layer of the dielectric layer, different anisotropy is given to the metal particles in each layer by thermoplastic deformation, and it becomes easy to adjust and control the wavelength characteristic, and furthermore, to control the wavelength characteristics. By making the absorption wavelength different, it becomes possible to broaden the wavelength characteristics as a whole,
An excellent polarizing element having no wavelength dependency can be provided.

[0023]

Embodiments of the present invention will be described with reference to the drawings. In the laminate P shown in FIG. 1, a dielectric layer in which metal particles having anisotropy are dispersed on one main surface or both main surfaces of a dielectric substrate 1 made of, for example, translucent glass is formed. This is a laminate before forming a large number of laminated polarizing elements while changing the thickness. That is, for example,
Steps A to C (A: Dielectric substrate 1 made of glass)
A step of depositing and forming metal fine particles on a dielectric film-forming surface containing a metal by sputtering, and B: heating the dielectric film-forming surface at a temperature lower than the glass softening point of the dielectric to aggregate the metal fine particles. The step of forming particles, C: the step of forming a dielectric layer into a film by sputtering) is repeated a plurality of times to form a metal layer 2 made of metal fine particles on a dielectric substrate 1.
(1), dielectric layer 3 (1)... Metal layer 2 (n-1),
Dielectric layer 3 (n-1), metal layer 2 (n), dielectric layer 3
(N) are stacked in large numbers.

Then, while heating the laminated body P at a predetermined temperature, a predetermined direction (direction of the main surface of the dielectric substrate 1) AA '
Are subjected to plastic processing such as stretching by applying stress to the metal particles 4 (4 (1),... 4 (n) having anisotropy on the dielectric substrate 1 as shown in FIGS. -1), 4
(N)) is dispersed in the dielectric layer 5 (5 (1),... 5)
(N-1), 5 (n)) are obtained.
After that, the uppermost layer 5 (n) of the dielectric substrate 1 is polished to produce desired polarizing elements P1 and P2. Here, when manufacturing a polarizing element in which the thickness of each layer of the dielectric layer is different from each other,
The layers other than the uppermost layer of the dielectric layer are formed so as to be sequentially thicker or sequentially thinner.

When the heating temperature is equal to or higher than the melting point of the metal, the metal particles stretched together with the dielectric layer are re-sphered due to surface tension, lose their shape anisotropy and exhibit polarization characteristics. The temperature is set lower than the melting point of the metal.

The dielectric substrate 1 and the dielectric layer 5 are made of borosilicate glass BK-7 glass (about 69% SiO _2).
wt%, B ₂ O ₃ is about 10 wt%), Pyrex glass (# 7740, SiO ₂ is about 81wt%, B ₂ O ₃ is about 1
3 wt%), quartz glass and the like are suitable. The dielectric layer 3 is made of the same material as the dielectric substrate 1 so that the coefficient of thermal expansion is equal, and the mutual adhesion is improved.

The metal particles 4 are made of Ag, Cu, Au, F
e, Ni, Cr and the like are suitably used for the material of these dielectric layers 5.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail. [Example 1] As shown in FIG. 2, the laminated polarizing element P1 is characterized in that the thickness of the dielectric layer 5 is gradually increased from the first layer to the uppermost layer of the multilayer body (multilayer body). Is what you do.

The dielectric substrate 1 is made of BK7 glass. First, a copper (Cu) thin film layer as a metal fine particle layer and a BK7 glass thin film layer as a dielectric layer are alternately laminated on the substrate 1 to obtain a Cu-based material. A BK7 laminate is produced.

That is, the degree of vacuum was 2.0 × 10 −3 on the BK7 glass substrate 1 by magnetron sputtering.
Torr, film formation speed of 7.6 nm / sec, film thickness of about 30
A first Cu thin film layer having a thickness of 2.0 nm is formed, and a vacuum degree of 2.0.times.10@-3 Torr and a film forming rate of 0.1 nm are formed on the Cu thin film layer.
A BK7 thin film layer as a first dielectric thin film layer having a thickness of about 100 nm at 2 nm / sec is formed.

This series of steps is repeated 10 times.
When manufacturing a laminated body composed of alternating layers of the thin film layer and the BK7 thin film layer, the thickness of the BK7 thin film is increased by 20 nm as the number of stacked layers increases from the second layer to the uppermost layer.

Thereafter, the laminate is heated at a temperature of 625 ° C. near the softening point of BK7 glass and stretched, as shown in FIG. 2, to make the shape of the island-shaped metal particles 4 have anisotropy.
At the same time, the particles are oriented.

Here, the aspect ratio (major axis length / minor axis length) of the metal particles 4 after stretching is about 5 (about 25 n) in the first layer.
m / about 5 nm), and gradually increased from the second layer to the top layer, and was about 10 (about 400 nm / about 40 nm) in the top layer. The thickness of the first dielectric layer after stretching is about 40 nm, and the thickness of the second to uppermost layers is gradually increased to about 1 nm in the uppermost layer.
43 nm, and about 1900 n
m to about 665 nm.

As a result, the shape of the metal particles in each layer is different, the polarization characteristics are obtained in a wide wavelength band from the visible light region to the infrared light region, and a very excellent polarization element having no wavelength dependence has been made possible.

Example 2 As shown in FIG. 3, in the laminated polarizing element P2, the thickness of the dielectric layer 5 is gradually reduced from the first layer to the uppermost layer of the multilayer body (multilayer body). It is characterized by the following.

That is, the degree of vacuum was 2.0 × 10 −3 on the BK7 glass substrate 1 by magnetron sputtering film formation.
Torr, film formation speed of 7.6 nm / sec, film thickness of about 30
A first Cu thin film layer having a thickness of 2.0 nm is formed, and a vacuum degree of 2.0.times.10@-3 Torr and a film forming rate of 0.1 nm are formed on the Cu thin film layer.
A Cu thin film layer as a first metal thin film layer having a thickness of about 30 nm is formed at 2 nm / sec, and a vacuum degree of 2.0.times.10@-3 Torr and a film forming speed of 0.1 mm are formed on the Cu thin film layer. 2n
A BK7 thin film layer as a first dielectric thin film layer having a thickness of 300 nm is formed at m / sec.

This series of steps is repeated 10 times.
When manufacturing a laminated body composed of alternating layers of the thin film layer and the BK7 thin film layer, the thickness of the BK7 thin film is reduced by 20 nm as the number of stacked layers increases from the second layer to the uppermost layer.

Thereafter, the laminate is heated at a temperature of 625 ° C. in the vicinity of the softening point of BK7 glass and stretched to give anisotropic metal particles 4 as shown in FIG.
At the same time, the particles are oriented.

Here, the aspect ratio (major axis length / minor axis length) of the metal particles 4 after stretching is about 10 (about 30) in the first layer.
0 nm / about 30 nm), and gradually decreased from the second layer to the top layer, and was about 5 (about 50 nm / about 10 nm) in the top layer. The first dielectric layer after stretching is about 110 n.
m, the thickness of the second layer to the uppermost layer gradually decreases to about 42 nm in the uppermost layer.
nm to about 735 nm.

As a result, the shape of the metal particles in each layer is different, the polarization characteristics are obtained in a wide wavelength band from the visible light region to the infrared region, and a very excellent polarization element having no wavelength dependence has been made possible.

[0041]

According to the polarizing element and the method of manufacturing the same of the present invention, a high-performance polarizing element having extremely excellent wavelength characteristics without any limitation on the wavelength of light used can be provided. In particular, it can be suitably applied to an optical isolator, an optical sensor, a magnetic sensor, and the like having a short transmission distance.

Further, by changing the thickness of the dielectric layer laminated on the dielectric substrate, it is possible to control the anisotropy of the metal particles by thermoplastic deformation such as stretching accurately and easily, and to polarize ( Adjustment of the wavelength of light to be absorbed) can be facilitated.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating an example of a multilayer body according to the present invention. FIG. 2 is a partial cross-sectional view illustrating an example of a polarizing element according to the present invention. FIG. 3 is a partial cross-sectional view illustrating another polarizing element according to the present invention.

[Explanation of symbols]

1: dielectric substrate, 2: metal layer, 3: dielectric layer, 4:
Metal particles, 5: dielectric layer, P: laminate (multilayer), P
1, P2: polarizing element

Claims (3)

[Claims] 1. A polarizing element comprising a plurality of dielectric layers in which metal particles having anisotropy are dispersed in a dielectric on at least one principal surface of a dielectric substrate having a light-transmitting property. ,
A polarizing element, wherein the thickness of each of the dielectric layers is different from each other. 2. The semiconductor device according to claim 1, wherein the thickness of each of the dielectric layers except for the uppermost layer is formed so as to be gradually thicker or thinner than the layer located on the dielectric substrate side. Item 2. The polarizing element according to Item 1. 3. A method for manufacturing a polarizing element, comprising: laminating a plurality of dielectric layers in which metal particles having anisotropy are dispersed in a dielectric, on a dielectric substrate having a light-transmitting property. On at least one principal surface of the dielectric substrate, a plurality of metal layers and dielectric layers are alternately stacked, and the thickness of each layer of the dielectric layers is alternately changed to obtain a multilayer body. A method for manufacturing a polarizing element, comprising heating and softening and stretching a dielectric substrate to disperse anisotropic metal particles in a dielectric.