JPS6116961B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an optical polarization circuit element.

Conventional optical polarization circuit elements have generally been made of prism bodies made from optical crystals.

However, it cannot be said that it is easy to obtain such an optical polarization circuit element.
Furthermore, the conventional optical polarization circuit element described above cannot be said to have good compatibility with other optical integrated circuit elements constituting the optical integrated circuit device, and therefore, it cannot be said that the conventional optical polarization circuit element described above has good compatibility with other optical integrated circuit elements constituting the optical integrated circuit device. Even if a device could not be constructed, it had drawbacks such as the fact that it could not be easily constructed as a small, stable, and low-loss device.

Therefore, the present invention aims to propose a novel optical polarization circuit element free from the above-mentioned drawbacks, which will become clear from the detailed description below.

The present inventors have developed a dielectric layer (a dielectric layer having a dielectric constant such that when the dielectric constant is expressed as a complex quantity, the real part is positive and the imaginary part can be ignored with respect to the real part) as follows. By doing so, it is possible to obtain a waveguide configuration that allows light to be transmitted with almost no attenuation for any polarization component in any polarization direction contained therein. A dielectric layer having a dielectric constant expressed by a complex quantity with a non-negligible imaginary part, or a complex quantity whose real part is negative (including the case where the imaginary part is 0). Ba,
In view of the fact that it is possible to obtain a waveguide structure that can transmit light while imparting relatively large attenuation to polarization components in all polarization directions contained therein, a combination of a dielectric layer and a complex dielectric layer is proposed. As a result of various considerations and experiments, we found that the wavelength λ of the light to be polarized is as shown in Figure 1. A dielectric layer ₁ having a small thickness D 1 and a thickness D ₂ which is also small compared to the wavelength λ of the light to be polarized and sufficiently compared to the dielectric constant ε ₁ of the dielectric layer 1. It consists of a laminate 3 in which complex dielectric layers 2 having a large dielectric constant ε ₂ are laminated in alternating order. The dielectric layer is such that the plane perpendicular to the planes of the dielectric layer 1 and the complex dielectric layer 2, that is, the plane perpendicular to the top surface of the laminate 3, serves as the input/output planes P1 and P2 of light to be polarized. In the case of a combination configuration with a complex dielectric layer, the dielectric layer 1 and the complex dielectric layer constituting the laminate 3 in a plane parallel to the laminate end faces 4 and 5 of the laminate 3, that is, the light input/output surfaces P1 and P2. The stacking direction of the body layer 2 is the y-axis direction, and the direction orthogonal to the y-axis direction in a plane parallel to the stacked end surface 4 of the laminate 3 is the x-axis direction, and the y-axis direction and x
The direction perpendicular to both directions of the axis is defined as the z-axis direction.
A polarized light component whose polarization direction is in the y-axis direction (so-called
If light containing a polarization component (TM wave component) and a polarization component (so-called TE wave component) whose polarization direction is in the x-axis direction is incident as incident light, generally speaking, a polarization component whose polarization direction is in the y-axis direction and a polarization component whose polarization direction is in the x-axis direction are incident. Light containing a polarized component in the axial direction is obtained as emitted light from the light input/output surface P2 of the laminate 3, but in this case, the light incident into the laminate 3 is polarized within the laminate 3. Regarding the polarization component whose polarization direction is the x-axis direction, the polarization direction is the y-axis direction.
The polarization component is attenuated with a larger attenuation constant than the polarization component in the axial direction, and the polarization direction is
Assuming that a polarized light component whose polarization direction is in the x-axis direction is attenuated with a larger attenuation constant than a polarized light component whose polarization direction is in the y-axis direction, When the attenuation constants for a certain polarization component are α _x and α _y , respectively, the relationship between the attenuation constants α _x and α _y with the dielectric constants ε ₁ and ε 2 of the dielectric layer 1 and the complex dielectric layer ₂ is as follows. Approximately given by α _y /α _x = |ε ₁ /ε ₂ | ² , therefore, the dielectric constant ε ₂ of the complex dielectric layer 2 is sufficiently larger than that of the dielectric layer 1 ε ₁ By doing this, it is possible to obtain a polarized light component whose polarization direction is in the x-axis direction from the output light obtained from the light input/output surface P2, which can be ignored with respect to a polarized light component whose polarization direction is in the y-axis direction. In fact, we have confirmed that it is possible to obtain a function as an optical polarization circuit element.

Therefore, we have here proposed a novel optical polarization circuit element according to the present invention as set forth in the claims, one embodiment of which has the configuration described above in FIG. The structure uses a substrate made of quartz glass, for example, and then attaches a dielectric layer thereon by, for example, sputtering, and then attaches a complex dielectric layer on top of the dielectric layer, for example, by vapor deposition. This can be obtained by obtaining a laminate on which dielectric layers and complex dielectric layers are sequentially and alternately stacked, and then obtaining this from a substrate.

The structure of one embodiment of the optical polarization circuit element according to the present invention has been clarified above, and according to this structure, as is clear from the above,
It is possible to obtain a function as an optical polarization circuit element. Incidentally, the dielectric layer 1 constituting the laminate 3 has a dielectric constant ε for light with a wavelength λ of 1 μm.
₁ is made of silica exhibiting ε ₁ ≒2, and complex dielectric layer 2 is made of aluminum exhibiting a dielectric constant ε ₂ of (ε ₂ ≈−61.9−j23.2) for light having the same wavelength λ of 1 μm. If α is assumed to be
Since the value of _y /α _x = |ε ₁ /ε ₂ | ² is obtained as 0.9×10 ^-3 , the polarization direction of most of the output light obtained from the light input/output surface P2 of the laminate 3 is in the x-axis direction. The function as an optical polarization circuit element can be obtained by obtaining light that does not contain any polarization component and is composed of a polarization component whose polarization direction is mostly in the y-axis direction.

According to the configuration of the embodiment of the optical polarization circuit element according to the present invention, it is possible to obtain the function as an optical polarization circuit element, but the configuration is such that dielectric layers and complex dielectric layers are sequentially and alternately arranged. Since it has a long laminate structure in which layers are stacked, the optical polarization circuit element itself can be used as an optical polarization circuit made of a prism body produced from a conventional optical crystal by, for example, sputtering or vapor deposition, as described above. This can be obtained more easily than obtaining the element itself.

Further, according to the structure of the embodiment of the present invention described above, since it has a structure in which dielectric layers and complex dielectric layers are sequentially and alternately laminated,
It has a structure that can be said to have better compatibility with other optical integrated circuit elements constituting an optical integrated circuit device than a conventional optical polarization circuit element made of a prism body made from an optical crystal. Including the configuration of the embodiment of the present invention described above, there are various types of devices that are smaller, more stable, and have lower loss than those that include an optical polarization circuit element made of a prism body made from a conventional optical crystal. An optical integrated circuit device can be easily constructed.

Further, according to the structure of the embodiment of the optical polarization circuit element according to the present invention described above, the optical polarization circuit element (hereinafter referred to as optical polarization circuit element A) has a light input/output surface as shown in FIG. By leaving P1 and P2 and embedding them in the cladding layer B, the optical polarization circuit element A can also have the function of a waveguide. In addition, the incidence of light into the light polarization circuit element A from the light input/output surface P1 and the exit of light from the light input/output surface P2 of the light polarization circuit element A are controlled by the light input/output ratio. Face P
When optical transmission lines such as optical fibers are coupled to 1 and P2, respectively, the coupling becomes easy, and the incidence of light into the optical polarization circuit element A and the light output therefrom are prevented from being lost. This is something that can be done less.

Further, according to the structure of the optical polarization circuit element A according to the present invention as described above in FIG. and A2, and one of the optical polarization circuit elements A1 is rotated by 45 degrees with respect to the incident polarized light while the required magnetic field is applied from the magnet 11 as shown in FIG. A magneto-optical effect element (Faraday effect element) 12 configured to emit light is arranged to face one light input/output surface 13 with a lens 14 interposed therebetween, if necessary, and the other light polarization circuit element A2. is arranged facing the other light input/output surface 15 of the magneto-optic effect element 12 in a relationship rotated by 45 degrees with respect to the light polarization circuit element A1, while the light polarization circuit elements A1 and A2
By coupling the optical fibers F1 and F2 on the side opposite to the magneto-optic effect element 12, the polarization direction of the optical fiber F1 is in the y-axis direction when viewed on the light input/output surface of the optical polarization circuit element A1. When light having a certain polarization component is transmitted toward the light polarization circuit element A1 side, the polarization direction of the light is the y-axis direction and the polarization component is transmitted to the light polarization circuit element A1-lens 1.
4-Magneto-optic effect element 12-Optical polarization circuit element A2
Although the light from the optical fiber F1 is transmitted to the optical fiber F2 by entering the optical fiber F2 through the optical fiber F2, the light enters the optical fiber F2 and is transmitted to the optical fiber F2. Therefore, even if light having a polarization component whose polarization direction is in the y-axis direction is transmitted toward the optical polarization circuit element A2, it is impossible for any polarization component of that light to enter the optical fiber F1. Therefore, it is easy to obtain a configuration that can function as an optical isolator in which the light from the optical fiber F2 is not transmitted to the optical fiber F1, and in this case, the light from the optical fibers F1 and F2 is not transmitted to the optical fiber F1. Since the respective couplings to the polarization circuit elements A1 and A2 can be achieved by bringing the end faces of the optical fibers into close contact with the light input/output surfaces of the optical polarization circuit elements, the function as an optical isolator in this case can be achieved more effectively. It has great features such as:

In FIG. 1, which shows one embodiment of the optical polarization circuit element according to the present invention, the stacked body 3 is shown in the shape of the stacked end faces 4 and 5 facing each other, which are the light input/output surfaces P1 and P2. Although the laminate 3 is shown as having a rectangular configuration, as shown in FIG. It is also possible to use a circular configuration and use this configuration as another embodiment of the optical polarization circuit element according to the present invention. According to the structure of another embodiment of the optical polarization circuit element according to the present invention shown in FIG. Accordingly, the incidence of light into and the light output from the structure of another embodiment of the light polarization circuit element according to the present invention shown in FIG. As shown in FIG. 5, this is described above in FIG. 4 in the same way as described in FIG. 2 above. It will be even more advantageous if the structure of the other embodiment of the optical polarization circuit element according to the present invention is embedded in the cladding layer B.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view showing an example of the optical polarization circuit element according to the present invention, FIG. 2 is a schematic perspective view showing an example of its usage, and FIG. 3 is a schematic perspective view showing an example of the optical polarization circuit element according to the invention. FIG. 4 is a schematic side view showing an example of application, FIG. 4 is a schematic perspective view showing another example of the optical polarization circuit element according to the present invention, and FIG. 5 is a schematic perspective view showing an example of its usage. be. In the figure, 1 is a dielectric layer, 2 is a complex dielectric layer, 3 is a laminate, 4 and 5 are end faces of the laminate, P1 and P2 are light input/output surfaces, A, A1, and A2 are optical polarization circuit elements, and B
11 is a cladding layer, 11 is a magnet, 12 is a magneto-optic effect element, 13 and 15 are light incident/exit surfaces, 14 is a lens, and F1 and F2 are optical fibers.

Claims (1)

[Scope of Claims] 1. A dielectric layer having a thickness smaller than the wavelength of the light to be polarized; and the dielectric layer having a thickness smaller than the wavelength of the light to be polarized. complex dielectric layers having a dielectric constant sufficiently larger than that of the laminate, the end faces of the laminate facing each other parallel to each other and perpendicular to the upper surface of the laminate; is the input/output plane of the light to be polarized, the direction perpendicular to the top surface of the laminate in a plane parallel to the input/output plane is the y-axis direction, and the above in a plane parallel to the input/output plane is the y-axis direction. The direction perpendicular to the y-axis direction is the x-axis direction, and the polarized light includes a polarized component whose polarization direction is in the y-axis direction and a polarized component whose polarization direction is in the x-axis direction. When entering the laminate from one side of the input/output surface, the output light obtained from the other side of the input/output surface has a polarization component whose polarization direction is the x-axis direction, and the polarization direction is the x-axis direction. An optical polarization circuit element, characterized in that it is configured so that the polarization component in the y-axis direction can be ignored.