KR100738802B1 - Magneto-optic device employing magnetic flux concentration structure and method for preferential saturation magnetization of the same - Google Patents

Abstract

A magneto-optic device having a magnetic flux concentration structure and a selective saturation magnetization method of a magneto-optic device are provided to selectively saturate and magnetize only a specific region of a magneto-optic waveguide layer through the relatively small magnetic field by applying the magnetic flux concentration structure. A magneto-optic device having a magnetic flux concentration structure is formed by stacking magnetic field applying layers(210) and magneto-optic waveguide layers(220) in order. The magneto-optic waveguide layer is formed in a ridge-shaped structure of which a center portion is protruded upward higher than both parts of the center portion. The magnetic field applying layer formed at the lower side of the center portion of the magneto-optic waveguide layer is thinner than the magnetic field applying layer formed at both parts.

Description

Magneto-optic device employing magnetic flux concentration structure and method for preferential saturation magnetization of the same

1 is a reference diagram for explaining the effect of increasing the focusing flux.

2 is a cross-sectional view of a magneto-optical device having a flux focusing structure according to the present invention.

3 is a reference diagram for explaining a longitudinal arrangement of a traveling direction and a magnetic field direction of light.

4 is a reference diagram for explaining a transverse arrangement of a traveling direction and a magnetic field direction of light.

5 is a reference diagram for explaining a method of selective saturation magnetization of a magneto-optical waveguide layer in a longitudinal configuration.

FIG. 6 is a reference diagram for explaining a method of selective saturation magnetization of a magneto-optical waveguide layer in an lateral configuration. FIG.

The present invention relates to a magneto-optical device having a magnetic flux focusing structure and a selective saturation magnetization method of the magneto-optical device. More particularly, by applying the magnetic flux focusing structure, it is possible to selectively saturate a specific region of the magneto-optical waveguide layer. The present invention relates to a magneto-optical device having a magnetic flux focusing structure and a selective saturation magnetization method of the magneto-optical device.

The recent rapid development of optical communication systems requires the integration of various optical components, and many attempts have been made to implement them. In particular, isolators and circulators that utilize magneto-optical properties for the stability of devices used for optical signal processing, such as semiconductor lasers, optical amplifiers, and optical modulators, which are used as light sources to implement optical integration. The need for this is increasing.

On the other hand, since the elements using these magneto-optical characteristics are optical components that are not strictly usable as integrated bulk components, the non-reciprocal effect that optical properties change according to the light propagation direction is used. There is an active research on the proposal of new alternatives to waveguide integrated devices and their implementation.

In order to achieve the integration, the saturation magnetization of the magneto-optical waveguide layer of the non-reciprocal phase shifter (Non-reciprocal phase shifter), which maximizes the magneto-optical effect and minimizes the size of the device, is essential. It is essential to develop a method for efficiently magnetizing a magneto-optical waveguide layer using a small magnetic field rather than the method.

SUMMARY OF THE INVENTION The present invention has been made to meet the above requirements, and includes a magneto-optical device and a magneto-optical device having a magnetic flux focusing structure capable of selectively saturating a specific region of the magneto-optical waveguide layer by applying a magnetic flux focusing structure. An object of the present invention is to provide a selective saturation magnetization method of.

A magneto-optical device having a flux focusing structure according to the present invention for achieving the above object has a structure in which a magnetic field applying layer and a magneto optical waveguide layer are sequentially stacked, the magneto optical waveguide layer is the other part of the center portion It is a ridge type structure having a relatively protruding shape compared to the above, and the thickness of the magnetic field applying layer provided below the center portion of the magneto-optical waveguide layer is smaller than the thickness of the magnetic field applying layer in other portions. do.

Preferably, the thickness of the central portion of the magnetic field applying layer is 20 to 80% of the thickness of the other portions.

Preferably, the magnetic field applying layer has a structure in which a magnetization stable layer, a non-magnetic layer, and a magnet layer are sequentially stacked, and the thickness of the center portion of the magnet layer is smaller than the thickness of the magnet layer of other portions.

Preferably, the non-magnetic layer is Ru.

Preferably, the magnetization stable layer and the magnet layer is made of any one of CoPtCrTa, CoPtCrB.

In addition, the magneto-optical device having a magnetic flux focusing structure according to the present invention includes a first magneto-optical device and a second magneto-optical device, and the first and second magneto-optical devices each include a magnetic field applying layer and a magneto-optical waveguide layer. The magnetic field applying layer of the first magneto-optical element is designed such that the thickness of the center portion is smaller than that of other portions, and the magnetic field applying layer of the second magneto-optical element has a cross-sectional structure. Another technical feature is that the thickness is constant so that the critical magnetic field value at which the magneto-optical waveguide layer of the first magneto-optical element is saturated magnetization is smaller than the critical magnetic field value at which the magneto-optical waveguide layer of the second magneto-optical device is saturated magnetization. .

Preferably, the thickness of the other part of the magnetic field applying layer of the first magneto-optical element and the thickness of the magnetic field applying layer of the second magneto-optical element are the same.

Preferably, the first and second magneto-optical elements are formed on a substrate, and the magnetic field transfer layer is further provided on the substrate to be in physical contact with the magnetic field applying layers of the first and second magneto-optical elements.

Preferably, the first and second magneto-optical elements are formed on a substrate, and a magnetic field transfer layer is further provided on the substrate in the longitudinal direction of the first and second magneto-optical elements, and the magnetic field transfer layer is It is in physical contact with the magnetic field applying layer of the first magneto-optical element.

The selective saturation magnetization method of the magneto-optical device according to the present invention is larger than the critical magnetic field in which the magneto-optical waveguide layer of the first magneto-optical device is saturated magnetization, and is larger than the critical magnetic field in which the magneto-optical waveguide layer of the second magneto-optical device is saturated magnetization. The small magnetic field is applied to the magnetic field applying layers of the first and second magneto-optical elements, so that only the magneto-optical waveguide layer of the first magneto-optical element is selectively saturated.

Preferably, the magnetic field direction applied to the magnetic field applying layers of the first and second magneto-optical elements is parallel or perpendicular to the traveling direction of light passing through the magneto-optical waveguide layers of the first and second magneto-optical elements.

According to a feature of the present invention, by applying a magnetic flux focusing structure, the magneto-optical waveguide layer can be saturated by a relatively small magnetic field, and using this principle, only a specific region of the magneto-optical waveguide layer can be selectively saturated. You can do it.

Hereinafter, an embodiment of a magneto-optical device having a flux focusing structure according to the present invention will be described in detail with reference to the drawings. 1 is a reference diagram for explaining an effect of increasing the flux focus, and FIG. 2 is a cross-sectional view of a magneto-optical device having a flux focusing structure according to the present invention.

First, as shown in FIG. 2, the magneto-optical device having the flux focusing structure according to the present invention is composed of a combination of a magnetic field applying layer 210, a magneto-optical waveguide layer 220, and a protective layer 230. Although not shown, the magnetic field applying layer 210 may be formed on a single crystal silicon substrate, and the magneto-optical waveguide layer 220 and the protective layer 230 are sequentially stacked on the magnetic field applying layer 210. do.

The magnetic field applying layer 210 serves to magnetize the magneto-optical waveguide layer 220. In detail, the magnetization stabilizer layer 211, the non-magnetic layer 212, and the magnet layer 213 are sequentially stacked. It can be configured as a structure. Here, the magnetization stable layer 211 and the magnet layer 213 is made of a magnetic material, and specifically, may be composed of any one of CoPtCrTa and CoPtCrB. In addition, the non-magnetic layer 212 is made of a nonmagnetic material, it may be composed of Ru.

On the other hand, as described in the object of the present invention, the magneto-optical device according to the present invention is characterized by having a magnetic flux focusing structure. The following principle is used to implement the flux focusing structure.

Magnetic flux ( Φ _B ) refers to the number of magnetic induction lines passing through a certain surface in an object. I can express it.

Φ _B  = ∫B · dA

Meanwhile, as shown in FIG. 1, when a constant magnetic flux passes through an object having various cross-sectional areas in the flow direction of the magnetic flux, as the cross-sectional area decreases, the magnetic flux density of the cross-sectional area, that is, the magnetic field becomes relatively large and the cross-sectional area increases. The magnetic field of the cross-sectional area becomes small (see Equation 2).

Φ = B _One A _One = B ₂ A ₂ (A _One 〉 A ₂ , B ₂ 〉 B _One )

The magneto-optical device according to the present invention uses the principle that the magnetic field becomes larger as the cross-sectional area is smaller as described above, and proposes a cross-sectional structure of the magnet layer 213 as shown in FIG.

Specifically, the magneto-optical device according to the present invention has a ridge type structure in which a central portion of the magneto-optical waveguide layer protrudes relatively upward compared to other portions, and has a ridge-type structure. The cross-sectional area of the magnet layer provided in the lower portion is characterized in that it is designed to be smaller than the cross-sectional area of the other portion (hereinafter referred to as "side portion"). Accordingly, even when a small magnetic field is applied to the magnet layer, a relatively large magnetic field can be applied to the central portion of the magnet layer due to the relatively small cross-sectional area, and ultimately the magneto-optical waveguide layer. This saturation magnetization becomes possible. The thickness t ₁ of the center portion of the magnet layer 213 is preferably set to be 20 to 80% of the thickness t ₂ of both portions.

On the other hand, the optical properties vary according to the arrangement of the traveling direction of the light incident on the magneto-optical element and the magnetic field direction applied to the magneto-optical waveguide layer of the magneto-optical element. Optical devices, such as optical isolators and optical circulators, utilize such variations in optical properties, such as non-reciprocal phase shift, mode conversion, and the like.

The arrangement of the light propagation direction and the magnetic field direction may be largely divided into a longitudinal configuration and a transverse arrangement. The longitudinal arrangement refers to an arrangement in which the traveling direction of the light and the magnetic field direction are parallel as shown in FIGS. 3A and 3B, and the transverse arrangement refers to the traveling and magnetic field directions of the light as shown in FIGS. 4A and 4B. This means an array perpendicular to each other.

The longitudinal arrangement may enable polarization rotation of incident light, wherein the polarization rotation angle is proportional to the length of the magnetized magnetization region. By selectively adjusting the length of the magnetization region, the polarization rotation angle can be adjusted, thereby implementing a Faraday rotator.

The lateral arrangement has a characteristic of causing an irreversible phase shift phenomenon in the vertical mode of incident light, so that the intensity of the output light can be adjusted by selectively adjusting the magnetization region.

In the longitudinal and transverse arrangements, it may be necessary to selectively saturate magnetize specific regions of the magneto-optical waveguide layer in order to induce specific optical properties such as irreversible phase shift and mode conversion.

The magneto-optical device having the flux focusing structure according to the present invention is ultimately applied to the selective saturation magnetization of the magneto-optical waveguide layer, and through this, optical devices such as an optical isolator and an optical circulator can be precisely implemented. Will be. Hereinafter, a method of implementing selective saturation magnetization by applying the magneto-optical device according to the present invention will be described. 5 is a reference diagram illustrating a selective saturation magnetization method of the magneto-optical waveguide layer in the longitudinal configuration, and FIG. 6 is a selective saturation magnetization method of the magneto-optical waveguide layer in the lateral configuration. It is a reference diagram for explaining this.

First, the selective saturation magnetization method of the magneto-optical waveguide layer in the longitudinal arrangement will be described. As shown in FIG. 5, the magneto-optical element is disposed on the substrate. The magneto-optical device is divided into a first magneto-optical device 300 and a second magneto-optical device 400, and the first magneto-optical device 300 includes a structure of the magneto-optical device according to the present invention, that is, magnetic flux focusing. It is a magneto-optical device having a structure, and the second magneto-optical device 400 is a conventional general magneto-optical device that does not have a flux focusing structure.

Like the first magneto-optical device 300, the second magneto-optical device 400 has a structure in which a magnetic field applying layer 410, a magneto-optical waveguide layer 420, and a protective layer 430 are sequentially stacked. In addition, the magnetic field applying layer 410 may be formed of a combination of a magnetization stable layer 411, a non-magnetic layer 412, a magnet layer 413. However, the magnet layer 313 of the first magneto-optical device 300 has a so-called magnetic flux focusing structure in which a center portion has a smaller thickness of the magnet layer than both portions, whereas the second magneto-optic device 400 The magnet layer 413 has a structure in which the thickness of the magnet layer of the center part and both parts is constant.

As the first magneto-optical device 300 has a magnetic flux focusing structure, the magneto-optical waveguide layer 320 may be easily saturated even when a relatively small magnetic field is applied to the second magneto-optical device 400. It becomes possible.

On the other hand, a magnetic field transfer layer 502 is formed on the substrate 501 to transfer a magnetic field to the magnetic field applying layers 310 and 410 of the first and second magneto-optical elements 300 and 400. The magnetic field transfer layer 502 may be made of a metallic nonmagnetic material having a high permeability, for example, copper (Cu).

In the above structure, the selective saturation magnetization of the magneto-optical waveguide layer in the longitudinal arrangement is performed through the following process. First, light is incident in the longitudinal direction of the first and second magneto-optical elements 300 and 400, and a magnetic field is assumed to be applied in a direction parallel to the traveling direction of the light.

Selective saturation magnetization of the magneto-optical waveguide layer refers to the saturation magnetization of only the magneto-optical waveguide layer 320 of the first magneto-optical device 300 of the first magneto-optical device 300 and the second magneto-optical device 400. It means to let.

As described above, the magneto-optical waveguide layer 320 of the first magneto-optical device 300 is saturated with a smaller magnetic field than the magneto-optical waveguide layer 420 of the second magneto-optical device 400. do. This is because the magneto-optical waveguide layer 320 of the first magneto-optical device 300 has a flux focusing structure. Therefore, the critical magnetic field that saturates the magneto-optical waveguide layer 320 of the first magneto-optical device 300 is greater than the critical magnetic field that saturates the magneto-optical waveguide layer 420 of the second magneto-optical device 400. Becomes small.

As a result, even when the same magnetic field is applied to the magnetic field applying layers 310 and 410 of the first and second magneto-optical elements 300 and 400 through the magnetic field transfer layer 502, the second magnetic optics are applied. The magneto-optical waveguide layer 420 of the device 400 may not be saturated magnetized, but only the magneto-optical waveguide layer 320 of the first magneto-optical device 300 may be saturated magnetized. That is, when a magnetic field having a magnitude corresponding to a critical magnetic field that saturates the magneto-optical waveguide layer 320 of the first magneto-optical device 300 is applied, the magneto-optical waveguide layer of the first magneto-optical device 300 ( Only 320 may be saturated magnetized.

Through such selective saturation magnetization of the magneto-optical waveguide layer, it is possible to selectively implement optical effects such as a non-reciprocal effect in a specific region of the magneto-optical waveguide layer.

On the other hand, the selective saturation magnetization method of the magneto-optical waveguide layer in the lateral configuration (equatorial configuration) is as follows. First, as shown in FIG. 6, a magneto-optical element composed of first and second magneto-optical elements 300 and 400 is disposed on the substrate 501 as in the longitudinal arrangement, and the first magnetism is disposed. The optical element has a magnetic flux focusing structure, and the second magneto-optical element has no magnetic flux focusing structure.

A magnetic field transfer layer 502 is formed on the substrate 501. Unlike the longitudinal arrangement, the magnetic field transfer layer 502 is formed in the longitudinal direction of the first and second magneto-optical elements 300 and 400. It is formed in the direction perpendicular to the direction. Accordingly, the magnetic field transfer layer 502 on the substrate 501 is in physical contact only with the magnetic field applying layer 310 of the first magneto-optical device 300.

In the above structure, the selective saturation magnetization of the magneto-optical waveguide layer in the transverse direction is performed through the following process. First, light is incident in the longitudinal direction of the first and second magneto-optical elements 300 and 400, and it is assumed that a magnetic field is applied in a direction perpendicular to the traveling direction of the light.

In this state, when a magnetic field is applied to the magnetic field transfer layer 502, the magnetic field applying layers 310 and 410 of the first and second magneto-optical elements 300 and 400 are magnetized and finally the first And the magneto-optical waveguide layers 320 and 420 of the second magneto-optical elements 300 and 400 are magnetized. However, since the first magneto-optical device 300 has a magnetic flux focusing structure, the magneto-optical waveguide layer 320 of the first magneto-optical device 300 and the magneto-optical device of the second magneto-optical device 400 are provided. The critical magnetic fields that saturate the optical waveguide layer 420 are different.

Accordingly, when the magnetic field having a magnitude corresponding to the critical magnetic field that saturates the magneto-optical waveguide layer 320 of the first magneto-optical device 300 is applied to the magnetic field transfer layer 502, the first magneto-optical layer Only the magneto-optical waveguide layer 320 of the element 300 can selectively saturate magnetize. Through such selective saturation magnetization of the magneto-optical waveguide layer, it is possible to selectively implement optical effects such as a non-reciprocal effect in a specific region of the magneto-optical waveguide layer.

The magneto-optical device having the flux focusing structure and the selective saturation magnetization method of the magneto-optical device according to the present invention have the following effects.

By applying a magnetic flux focusing structure, the magneto-optical waveguide layer can be saturated by a relatively small magnetic field. By using this principle, only a specific region of the magneto-optical waveguide layer can be selectively saturated.

Claims (14)

The magnetic field applying layer and the magneto optical waveguide layer are sequentially stacked, The magneto-optical waveguide layer has a ridge type structure in which a central portion protrudes upward relative to both sides of the central portion, and a thickness of the magnetic field applying layer provided below the central portion of the magneto-optical waveguide layer. The magneto-optical device having a flux focusing structure, characterized in that is smaller than the thickness of the magnetic field applying layer at both sides. The magneto-optical device having a magnetic flux focus increasing structure according to claim 1, wherein the thickness of the central portion of the magnetic field applying layer is 20 to 80% of the thickness of both portions. According to claim 1, wherein the magnetic field applying layer has a structure in which a magnetization stable layer, a non-magnetic layer, a magnet layer is sequentially stacked, the thickness of the central portion of the magnet layer is smaller than the thickness of the magnet layer of both sides A magneto-optical device having a magnetic flux focusing structure, characterized by the above-mentioned. 4. The magneto-optical device having a flux focusing structure according to claim 3, wherein the non-magnetic layer is made of Ru. 4. The magneto-optical device having a flux focusing structure according to claim 3, wherein the magnetization stable layer and the magnet layer are made of any one of CoPtCrTa and CoPtCrB. A first magneto-optical element and a second magneto-optical element, The first and second magneto-optical elements each have a structure in which a magnetic field applying layer and a magneto-optical waveguide layer are sequentially stacked. The magnetic field applying layer of the first magneto-optical element is formed such that the thickness of the center portion is smaller than the thickness of both portions, and the magnetic field applying layer of the second magneto-optical element has a constant cross section thickness over the entire surface, A magnetic field having a magnetic flux focusing structure, characterized in that the critical magnetic field value at which the magneto-optical waveguide layer of the first magneto-optical element is saturated magnetization is smaller than the critical magnetic field value at which the magneto-optical waveguide layer of the second magneto-optical device is saturated magnetization. Optical elements. 7. The magneto-optical device having a magnetic flux focus increasing structure according to claim 6, wherein the thicknesses of both sides of the magnetic field applying layer of the first magneto-optical device are the same as the thickness of the magnetic field applying layer of the second magneto-optical device. The magnetic field transfer layer of claim 6, wherein the first and second magneto-optical elements are formed on a substrate, and the magnetic field transfer layer is further provided on the substrate to be in physical contact with the magnetic field applying layers of the first and second magneto-optical elements. Magneto-optical device having a magnetic flux focusing structure, characterized in that. The magnetic field transfer layer of claim 6, wherein the first and second magneto-optical elements are formed on a substrate, and the magnetic field transfer layer is further provided on the substrate in a length direction of the first and second magneto-optical elements. The magneto-optical device having a magnetic flux focusing structure, characterized in that the physical contact with the magnetic field applying layer of the first magneto-optical device. The magnetic field applying layer of claim 6, wherein the magnetic field applying layer of the first and second magneto-optical elements has a structure in which a magnetization stabilizer layer, a non-magnetic layer, and a magnet layer are sequentially stacked. Optical elements. The magneto-optical device having a magnetic flux focus increasing structure according to claim 10, wherein the magnet layer of the first magneto-optical device has a thickness of a central portion smaller than that of magnet layers of both sides. 7. The magneto-optical device having a magnetic flux focus increasing structure according to claim 6, wherein the thickness of the center portion of the magnetic field applying layer of the first magneto-optical element is 20 to 80% of the thickness of both portions. In the selective saturation magnetization method using the magneto-optical device of claim 6, The first and second magnetic optics may have a magnetic field having a magnitude greater than a critical magnetic field in which the magneto-optical waveguide layer of the first magneto-optical element is saturated and smaller than a critical magnetic field in which the magneto-optical waveguide layer of the second magneto-optic device is saturated. Applied to the magnetic field applying layer of the device, And selectively saturating magnetization only of the magneto-optical waveguide layer of the first magneto-optical device. The magnetic field direction applied to the magnetic field applying layers of the first and second magneto-optical elements is parallel or perpendicular to the traveling direction of light passing through the magneto-optical waveguide layers of the first and second magneto-optical elements. Selective saturation magnetization method of the magneto-optical device, characterized in that.

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