WO2011048343A1

WO2011048343A1 - Method for producing a magnetophotonic crystal, magnetophotonic crystal and component including such a crystal

Info

Publication number: WO2011048343A1
Application number: PCT/FR2010/052263
Authority: WO
Inventors: Béatrice Dagens; Liubov Magdenko; Mathias Vanwolleghem; Franck Nicolas Fortuna
Original assignee: Universite Paris Sud 11; Centre National De La Recherche Scientifique
Priority date: 2009-10-23
Filing date: 2010-10-22
Publication date: 2011-04-28
Also published as: FR2951740B1; FR2951740A1

Abstract

The invention relates to a method for producing a magnetophotonic crystal (100) characterised in that said method includes the following steps: producing a photonic crystal in a first layer (102); producing a magneto-optical crystal in a second layer (104) separate from said first layer (102). The invention also relates to a magnetophotonic crystal produced using to the method according to the invention, in which the photonic crystal is separate from the magneto-optical crystal. The method enables self-alignment of the photonic crystal and the magneto-optical crystal.

Description

"Process for producing a magneto-photonic crystal, magneto-photonic crystal and component comprising such a crystal"

The present invention relates to a method for producing a magneto-photonic crystal. It also relates to a magneto-photonic crystal and a component comprising such a crystal.

The field of the invention is the field of designing and producing planar optical components, in particular magneto-photonic crystals, guided optics.

Nowadays, there is a development of magneto-photonic crystal components. More particularly, magneto-photonic crystal waveguides are the subject of much research because of their possible use for non-reciprocal optical transmissions, which is the basic principle of the isolation or circulation functions. optical.

The magneto-photonic crystal waveguide is based on the principle of the transverse magneto-optical Kerr effect and uses a combination of two properties, namely:

an optical function provided by an optical index grating generated by a network of air holes made in a garnet or a magnetic oxide, and

a magneto-optical Kerr effect provided by a network of interfaces between anisotropic materials (magneto-optical material) and isotropic (air holes)

Currently, the magneto-photonic crystal-based components are obtained by etching the magneto-photonic crystal in a layer of magneto-optic material by optoelectronic techniques using etching masks. Materials with the highest magneto-optical coefficients include Yttrium garnets or bismuth. These materials also have the characteristic of not having a loss in the infrared range or at least very little.

Nevertheless, these magneto-optical materials have the disadvantage of being among the most difficult to engrave by the techniques of optoelectronics because of their greater hardness than that of the conventional masks of engraving used which are most often made of dielectric or metallic material. Thus, the realization of nano-photonic crystals in a garnet film becomes a real challenge, particularly in the case of the use of scaling techniques on large scale substrates for a large scale. low cost manufacturing.

An object of the present invention is therefore to overcome the aforementioned drawbacks.

Another object of the invention is to provide a method for producing a simpler magneto-photonic crystal.

Another object of the invention is to provide a method for producing a low-cost magneto-photonic crystal.

Yet another object of the invention is to propose a method for producing a magneto-photonic crystal that is more effective than the currently known magneto- photonic crystals.

Finally, an object of the invention is to provide a method for producing a magneto-optical crystal with the standard techniques for producing planar optical components. The invention proposes to achieve the aforementioned objects by a method for producing a magneto-photonic crystal, characterized in that it comprises the following steps:

producing a photonic crystal in a first layer, and producing a magneto-optical crystal in a second layer distinct from said first layer.

The invention makes it possible to avoid the step of etching in a layer of magneto-optical material while producing a magneto-photonic crystal with the standard techniques for producing planar optical components. Indeed, the method according to the invention proposes to separate the two functions mentioned above, namely the optical function and the magneto-optical Kerr effect provided, in two layers separated from each other.

Unlike the magneto-photonic crystals of the state of the art in which the photonic crystal and the magneto-optical crystal are made in a single layer, the photonic crystal is not made in the same layer as the magneto-optical crystal; which avoids a step of guring of a layer of renal or magical oxide used to make the magneto-optic crystal.

The fact of not having to engrave a layer of garnet or magnetic oxide in order to achieve the photonic crista makes it possible to facilitate the production of the photonic crystal and therefore of the magneto-photonic crystal.

Therefore, by avoiding such a step of guring, the method according to the invention makes possible a low-cost manufacture of magneto-photonic crystals on the scale of large substrates.

Moreover, the real isation of the photonic crystal in a layer separated from the layer in which the magneto-optical crystal is made makes it possible to produce a photonic crystal of better quality, in particular because the photonic crystal can then be produced with interfaces having less roughness, the air holes being easier to achieve.

Finally, the production of the photonic crystal in a layer separated from the layer in which the néto-optic mag crystal is made allows to enjoy more freedom of design of a component integrating a photonic crystal because the air holes composing the crystal photon iq ue may have a greater depth compared to the crystals of the state of the art.

According to the invention, the photonic crystal can be produced by making holes in said first layer. The network of air holes providing mode guidance in the magneto-optical crystal, can be achieved by known etching techniques, for example using an etching mask also called periodic crystal mask.

In a preferred embodiment, the air holes are made over the entire thickness of the first layer. This configuration is optimal for a stronger influence of the photonic crystal, and a more accurate alignment with the magneto-optical crystal.

The magneto-optic crystal can be made by locally destroying the magnetic properties of the second layer by ion implantation, without destroying the garnet or mag- netic oxide layer. Ion implantation may be accomplished using a periodic crystal mask.

In a preferred embodiment, the magnetic properties of the second layer are dewatered to a greater extent. This configuration makes it possible to increase the efficiency of the crystal obtained.

Advantageously, the same periodic crystal mask can be used for producing said photonic crystal and said magneto-optical crystal. The use of a same periodic crystal mask for producing the photonic crystal and the magneto-optical crystal makes it possible to facilitate the alignment of the photonic and magneto-optical crystals, and in particular allows a self-alignment of the crystals. This further facilitates the manufacture of magneto-photonic crystal. Indeed, the alignment of the photonic crystal and the magneto-optical crystal is essential for the realization of the magneto-photonic crystal consisting of two separate crystals. Without alleviation, the desired effect is diminished and eventually lost. The self-alignment of the two crystals is all the more advantageous given the size scale of the crystals. The periodic crystal mask may be a thick metal mask.

The first layer may be a layer of dielectric material, for example a layer of SiO ₂ or Si ₃ N ₄ .

Advantageously, the magneto-photonic crystal may be made in a multilayer structure in which the second layer is disposed between the first layer and a substrate layer. Such a configuration of the magneto-photonic crystal makes it possible to position the crystal magneto-optical, that is to say the second layer, between two layers of similar optical indices, namely the first dielectric layer in which is formed the photonic crystal and the substrate layer. The multilayer structure thus obtained has a symmetry leading to a very low or even non-existent mode guiding cutoff threshold.

According to a second aspect of the invention, there is provided a magneto-photonic crystal produced according to the method according to the invention. According to a third aspect of the invention there is provided a magneto-photonic crystal comprising the photonic crystal separated from the magneto-optical crystal.

Advantageously, the thickness of the layer in which the magneto-optical crystal is formed is between 200 nm and 500 nm.

Advantageously, the thickness of the layer in which the photonic crystal is produced is between 100 nm and 500 nm.

In a particular embodiment, the photonic crystal may be a dielectric layer having an array of holes.

The magneto-optical crystal may be a layer consisting of an isotropic-anisotropic interface network. According to a particular embodiment, the isotropic-anisotropic interface network consists of a layer of garnet or magnetic oxide whose magnetic properties have been destroyed locally, for example over the entire thickness of the layer. .

According to a particular embodiment of the magnetophotonic crystal according to the invention, the magneto-optical crystal may be arranged between the photonic crystal and a substrate layer. Such an arrangement provides symmetry at the optical indexes allowing a very low or nonexistent mode guiding cutoff threshold. According to a fourth aspect of the invention, there is provided an optical component comprising at least one magneto-photonic crystal according to the invention. The magneto-photonic crystal can be integrated into the component.

In such a component, the magneto-photonic crystal may be arranged to provide an optical isolator, an optical circulator or a non-reciprocal mirror. The invention is particularly useful in the field of complex photonic circuits (PIC). It allows to increase their degree of integration.

One of the applications concerns the multiwavelength Tx / Rx receivers used in the routing nodes of the telecommunication networks.

Many other applications could take advantage of integrated photonic laser circuits comprising at least one magneto-photonic crystal, such as bio-photonics, for example for purposes of miniaturization.

Other advantages and characteristics will appear on examining the detailed description of a non-limiting embodiment, and the appended drawings in which:

FIG. 1 is a schematic representation in section of the principle of the magneto-photonic crystal according to the invention;

FIG. 2 is a schematic representation of a non-reciprocal mirror comprising a magneto-photonic crystal;

FIG. 3 is a diagrammatic sectional representation of the magneto-photonic crystal implemented in the non-reciprocal mirror of FIG. 2;

FIG. 4 is a schematic representation of an optical circulator comprising a magneto-photonic crystal;

FIG. 5 is a detailed schematic representation of a portion of the optical circulator of FIG. 4; and - Figure 6 is a schematic sectional representation of the magneto-photonic crystal implemented in the optical circulator of Figure 4. In the figures and in the following description, the elements common to several figures retain the same reference.

Figure 1 is a schematic representation, in section, of the principle of a magneto-photonic crystal 100 according to the invention.

The magneto-photonic crystal 100 has a first layer

102 of dielectric material in which is formed a photonic crystal providing the optical function. The first layer may be a layer of Si0 ₂ or Si ₃ N ₄ .

The magneto-photonic crystal 100 comprises a second layer 104 in which a magneto-optical crystal providing the magneto-optical Kerr effect is produced. The second layer 104 is composed of an anisotropic material and may be for example a layer of garnet or magnetic oxide. This second layer may for example be a layer of BIG: Bi ₃ Fe ₅ O ₁₂ or YIG: Y ₃ Fe ₅ O ₁₂ .

The second layer 104 is disposed between the first layer 102 and a substrate layer 106. Thus, the magneto-optical crystal is disposed between the photonic crystal and a substrate layer having optical indices of the same order. The photonic crystal is obtained by producing a network of optical indices. Such a network is obtained by producing a periodic network of holes 108 in the first layer 102. The network of holes can be made by known etching techniques using a periodic crystal mask or dielectric etching, for example a metal mask. thick. The dielectric zones are denoted 110

The holes 108 are made in the present example over the entire thickness of the first layer. The crista l mag néto-optic is obtained by performing a network of interfaces between anisotropic material and isotropic material in the second layer 104. Such a network is obtained by destroying locally, and su r all the shoulder of the second neck 104, the magnetic properties of the material constituting the second layer 104. Such an interface network can be achieved by ion implantation in the second layer 104 periodically, this ion depletion of destroying ions. locally, the magnetic properties of the magnetic material in which the second layer 104 is made. The magneto-optical crystal can be produced according to the same periodic diagram used for producing the holes in the first layer 102. It is possible to use the periodic mask used for producing the holes in the first layer 102. After implantation, a perimeter network is thus obtained. odique of implanted magnetic material 112. Areas of non-implanted materials are noted 114

The realization of the nano-optical crista l mag according to the invention can use methods known to perform the following steps, and for example in this order:

a growth of the second layer 104 on a substrate 106; then

a growth of the first layer 102 above the second layer 104; then

- Making a crystal mask layer above the first layer 102

an etching of the network of holes 108 in the first layer 102 using the crystal mask, then;

through the same mask, an implantation of the second layer 104. In the magneto-photonic crystal 100 obtained, the wave 117 is guided in the direction of the arrow 116, the arrow 118 indicating the orientation of the magnetization in the material. Thus, the process according to the invention makes it possible to simplify the manufacture of a nano-photonic crystal crystal by avoiding a complex and difficult operation of etching a magnetic material layer such as a layer of resin, especially at the scale of large size substrates.

Furthermore, according to the invention, the photonic crystal is obtained by making holes in a layer of dielectric, that is to say the first layer, which is easier to achieve and allows a greater freedom on the depth of the holes to be achieved. Such an omerty makes it possible to increase the design freedoms of components comprising at least one magneto-photonic crystal.

In addition, the realisation of the holes in a dielectric layer makes it possible to reduce the roughness of the interfaces obtained, and therefore a photonic crystal of better quality.

In addition, the invention facilitates the design of a magneto-photonic crystal-based component by guiding the mode in the second layer 104 surrounded by the first layer 102 and the substrate layer 106 which have indicia. similar optics. Indeed, the structure of the magneto-photonic crystal 100 obtained has a vertical symmetry which leads to a very low or nonexistent mode guiding cutoff threshold.

The layer of substrate has an optical efficiency of 1.97 at the wavelength 1.3 μm. In the particular case where the first layer is Si0 ₂ , the optical index of this first layer is 1.5 to 1.3 pm. In the particular case where the first layer is Si ₃ N _4, the optical index of this first layer is 1.7 to 1.3 pm.

FIG. 2 is a schematic representation of a component comprising a magneto-photonic crystal according to the invention. The component 200 shown in Figure 2 in an isometric view is a non-reciprocal mirror.

The first layer 102 is a layer of Si0 ₂ , and the second layer 104 is a layer of garnet. The zone of the nano-photonic crystal mag is referenced 202 in FIG. 2. The holes 108 made to obtain the photonic crystal have a clover shape. In the continuation of the holes 108, ions are implanted in the thickness of the garnet to suppress the magnetic properties of the garnet. The profile of the g uide mode is referenced 204. The making of the holes 108 and the ion implantation is carried out using the same periodic crystal mask.

FIG. 3 gives a sectional representation of the magneto-photonic crystal zone implemented in the non-reciprocal mirror 200 of FIG.

In the case of the non-reciprocal mirror 200, the hole array 108 performs a filter function.

The non-reciprocal mirror is made with a network of holes on a surface of about 50 × 50 μm ² . The thickness of the different layers is listed below:

first layer: ~ 200nm

second layer: ~ 300 nm

- substrate layer:> = 50pm

FIG. 4 is a schematic representation of another component comprising a magneto-photonic crystal according to the invention. The component 400 shown in FIG. 4 according to an isometric view is a magneto-photonic crystal optical circulator.

In component 400, the first layer 102 of the magnetophotonic crystal is a layer of Si0 ₂ , and the second layer 104 is a layer of garnet.

The circulator 400 has three input-outputs 402, 404 and 406.

The area of the magneto-photonic crystal is referenced 408 in FIG. 4. The holes 108 made to obtain the photonic crystal have a circular shape. In the hole 108, 10% are implanted in the thickness of the garnet to suppress the magnetic properties of the garnet. In the case of lattice 400, the hole areas 108 in the first layer 102 and the non-implanted areas 114 in the second layer are of different diameter according to their positioning in the structure. The widest part in the center being a hole 108.

FIG. 5 gives a detailed schematic representation of the area referenced 410 of the optical circulator 400 of FIG. 4.

Fig ure 6 is a sectional representation of the magneto-photonic crystal implemented in the optical circulator 400 of Figure 2.

The central part of the circulator is approximately 10 μm in diameter and the total (with the three access guides) is 100 to 200 μm on the side. The thickness of the different layers is listed below:

- first layer: ~ 200 nm

second layer: ~ 300 nm

- substrate layer:> = 50 pm

Naturally, the invention is not limited to the examples which have just been described.

Claims

1. A method for producing a magneto-photonic crystal (100), characterized in that it comprises the following steps:

- Realization of a photonic crista in a first layer

(102)

producing a magneto-optic crystal in a second layer (104) separate from said first layer (102); said photonic crystal being made by making holes (108) in said first layer,

said magneto-optical crystal being made by locally destroying the magnetic properties of the second layer by ion implantation; said method being characterized in that a same crystal mask is used for producing said photonic crystal and said magneto-optical crystal.

2. Method according to claim 1, characterized in that the holes (108) are formed over the entire thickness of the first layer.

3. Method according to any one of the preceding claims, characterized in that the magnetic properties are locally destroyed throughout the thickness of the second layer (104).

4. Method according to any one of the preceding claims, characterized in that the magneto-photonic crystal (100) is formed in a multilayer structure in which the second layer (104) is disposed between the first layer (102) and a layer substrate (106).

5. magneto-photonic crystal (100) made according to any one of the preceding claims.

The magneto-photonic crystal (100) according to claim 5, characterized in that the photonic crystal consists of a dielectric layer (102) having an array of holes (108).

Magneto-photonic crystal (100) according to claim 5 or 6, characterized in that the magneto-optical crystal consists of a layer (104) consisting of an isotropic-anisotropic interface network (112, 114).

8. magneto-photonic crystal (100) according to claim 7, characterized in that the isotropic-anisotropic interface network (112, 114) consists of a garnet or a magnetic oxide whose magnetic properties have been destroyed locally.

9. magneto-photonic crystal (100) according to any one of claims 5 to 8, characterized in that the magneto-optical crystal is disposed between the photonic crystal and a substrate layer (106).

An optical component (200, 400) comprising at least one magnetophotonic crystal according to any one of claims 5 to 9.

11. Component according to claim 10, characterized in that the magnetophotonic crystal is arranged to produce an optical isolator.

12. Component according to claim 10, characterized in that the magnetophotonic crystal is arranged to produce an optical circulator (400).

13. Component according to claim 10, characterized in that the magnetophotonic crystal is arranged to produce a non-reciprocal mirror (200).