KR102357157B1 - Structure for acousto-optic interaction - Google Patents

Abstract

An acousto-optic interaction structure according to an embodiment of the present invention is a laminated structure that generates an interaction between an incident sound wave and a light wave, and includes a plurality of unit structures continuously stacked in a direction in which the sound wave and the light wave travel. a pair of multi-layered structures; and a cavity layer disposed between the pair of multilayer structures, wherein each of the plurality of unit structures includes a first medium layer, and an acoustic impedance and an optical impedance of the first medium layer. The first medium layer and the second medium layer are laminated, and the pair of multilayer structures and the cavity layer are continuously arranged, and the first medium layer and the second medium layer are symmetrical with respect to the cavity layer. are arranged alternately.

Description

STRUCTURE FOR ACOUSTO-OPTIC INTERACTION

The present invention relates to a structure for acousto-optic interaction, and more particularly, to a multilayer structure for increasing the interaction between incident sound waves and light waves.

Acousto-optical interaction is a phenomenon in which the propagation direction, frequency, wavelength, and intensity of light waves are modulated by sound waves. It was first predicted by Leon Brillouin and confirmed experimentally by P. Debye and F. W. Sears. Acousto-optic interactions can be used in devices that control light waves, such as light modulators, switches, deflectors, filters, and frequency shifters. The efficiency and performance of this device can be improved by increasing the acousto-optical interaction, and recently, research to enhance the acousto-optical interaction has been actively conducted.

For example, attempts have been made to use slow light waves to enhance the acousto-optical interaction, or to use high-frequency sound waves with similar wavelength scales to control short-wavelength light waves.

One aspect of the present invention is to provide a structure that enhances the interaction between the two waves by varying the wavelength scales of the sound wave and the light wave.

According to an embodiment of the present invention, as a stacked structure in which a plurality of media is stacked to generate an interaction between an incident sound wave and a light wave, two media layers having different acoustic impedance and optical impedance a pair of multilayer structures including structures alternately arranged with each other along a direction in which the sound waves and light waves travel; and a cavity layer disposed between the pair of multilayer structures along a direction in which the sound wave and the light wave travel and made of a medium contacting both surfaces and a medium having different acoustic impedance and optical impedance, wherein the sound wave and the light wave The two medium layers are symmetrically arranged with respect to the cavity layer so that the ions are focused on the cavity layer.

The two medium layers are a first medium layer and a second medium layer having an acoustic impedance and an optical impedance greater than that of the first medium layer, and each of the pair of multilayer structures is the first medium layer and the second medium layer The unit structure made of may include a structure in which a plurality of layers are stacked along the direction in which the sound wave and the light wave travel.

The hollow layer may be continuously arranged with the pair of multilayer structures along a direction in which the sound waves and light waves travel, and may be formed of the same medium as the first medium layer.

The thickness of the cavity layer may be greater than or equal to 1/8 wavelength of the light wave.

The thickness of the cavity layer may be twice the thickness of each of the unit structures.

A product of a thickness of the cavity layer and an optical refractive index of the cavity layer may be an integer multiple of 1/2 wavelength of the light wave.

The thickness of the first medium layer and the second medium layer may be the same.

The first medium layer may _{be made of silicon dioxide (SiO 2} ), and the second medium layer may be made of silicon (Si).

The cavity layer may be continuously arranged with the pair of multilayer structures along the direction in which the sound wave and the light wave travel, and the second medium layer may be in contact with both surfaces of the cavity layer.

Each of the pair of multilayer structures further includes a second 'medium layer in contact with the hollow layer, wherein the second' medium layer has two sub-medium layers having different acoustic impedance and optical impedance in a direction in which the sound wave and the light wave travel may include a structure alternately arranged along the , and may have the same thickness as any one of the two medium layers.

The two sub-medium layers are a first sub-medium layer, and a second sub-medium layer having acoustic impedance and optical impedance greater than that of the first sub-medium layer, and the second 'medium layer includes the first sub-medium layer and The sub-unit structure including the second sub-medium layer may have a structure in which a plurality of sub-unit structures are stacked along a direction in which the sound wave and the light wave travel.

The first sub-medium layer and the second sub-medium layer may be symmetrically arranged with respect to the hollow layer.

The first sub-medium layer may be formed of the same medium as the first medium layer, and the second sub-medium layer may be formed of the same medium as the second medium layer.

A thickness of the first sub-medium layer may be smaller than a thickness of the second sub-medium layer.

The second 'medium layer may have three or more sub-unit structures.

The second medium layer may be continuously arranged between the cavity layer and the first medium layer, and may have the same thickness as the second medium layer.

The 2' medium layer may be continuously arranged between the other medium layer of the two medium layers and the cavity layer.

According to an embodiment of the present invention, by providing a cavity layer for focusing sound waves and light waves in the middle of a structure in which a plurality of media are stacked, interaction between sound waves and light waves can be enhanced.

In addition, since a hierarchical structure is included in the structure in which a plurality of media are stacked to reduce acoustic energy loss and reduce radiation loss of light waves, interaction between sound waves and light waves may be enhanced.

1 is a perspective view illustrating an acousto-optic interaction structure according to an embodiment of the present invention.
2 is a cross-sectional view illustrating an acousto-optic interaction structure according to a first embodiment of the present invention.
3 is a graph showing the effect of the acousto-optic interaction structure according to the first embodiment of the present invention.
4 is a cross-sectional view illustrating an acousto-optical interaction structure according to a second embodiment of the present invention.
5 to 7 are graphs showing effects of an acousto-optical interaction structure according to a second embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily carry out the present invention. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

In order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and the same reference numerals are given to the same or similar components throughout the specification.

In addition, since the size and thickness of each component shown in the drawings are arbitrarily indicated for convenience of description, the present invention is not necessarily limited to the illustrated bar.

Throughout the specification, when a part is "connected" to another part, it includes not only the case where it is "directly connected" but also the case where it is "indirectly connected" with another member interposed therebetween. In addition, when a part "includes" a certain component, this means that other components may be further included rather than excluding other components unless otherwise stated.

1 is a perspective view illustrating an acousto-optic interaction structure according to an embodiment of the present invention.

An acousto-optic interaction structure according to an embodiment of the present invention is a structure for generating an interaction between an incident sound wave and a light wave, and has a multilayer structure in which a plurality of medium layers are stacked along a direction in which the sound wave and the light wave travel.

Referring to FIG. 1 , an acousto-optic interaction structure 100 according to an embodiment of the present invention has a structure in which a first medium layer 121 and a second medium layer 122 made of different media are alternately stacked. . In FIG. 1 , if the z-axis direction is a direction in which sound waves and light waves travel, the first medium layer 121 and the second medium layer 122 form an xy plane and have a predetermined thickness in the z-axis direction.

According to the embodiment of the present invention, in the acousto-optical interaction structure 100 , a cavity layer 150 of a predetermined thickness D is disposed in the center, and the first medium layer 121 and the second medium layer are described above. The multi-layer structure in which 122 is stacked and the cavity layer 150 may be in a continuous stacked structure. That is, the cavity layer 150 may be inserted in the middle of a multilayer structure in which the first medium layer 121 and the second medium layer 122 are stacked.

In this case, referring to FIG. 1 , the first medium layer 121 and the second medium layer 122 may be alternately arranged symmetrically with respect to the cavity layer 150 . That is, the arrangement order of the first medium layer 121 and the second medium layer 122 arranged on both sides with respect to the hollow layer 150 may be symmetrical. At this time, the multi-layer structure arranged on both sides of the cavity layer 150 as a center may function as a high reflectance mirror. In particular, as the contrast between the acoustic impedance and the optical impedance of the first medium layer 121 and the second medium layer 122 increases, the reflectance increases. Accordingly, sound waves and light waves incident on the acousto-optic interaction structure 100 can be focused on the cavity layer 150 due to the high reflectivity of the multi-layer structure disposed on both sides of the cavity layer 150 , so that the acousto-optic interaction structure 100 is mutually acousto-optical. action can be enhanced.

More specifically, in the structure in which the first medium layer 121 and the second medium layer 122 are alternately arranged with a large contrast between the acoustic impedance and the optical impedance, the incident wave (sound wave or light wave) is partially at the interface of each medium. is transmitted and some is reflected, causing constructive interference between multiple transmitted waves or multiple reflected waves. Accordingly, in a structure in which a medium with high impedance to sound and light waves is alternately arranged in a structure to perfectly reflect both incident sound waves and light waves (to have very high reflectance for the incident sound waves and light waves), a cavity ( When the cavity) is inserted, two waves at a specific frequency cause constructive interference in the cavity, causing the amplitude to become very large and focus. This phenomenon is called acoustic and optical cavity mode, and a phenomenon in which two waves strongly interact occurs in the cavity mode.

In general, in order for the acoustic and optical cavity modes to occur in the above-described acousto-optic interaction structure 100 , the thickness of the alternately arranged first medium layer 121 and second medium layer 122 is 1/ of the incident wavelength. It must have a thickness of 4 or more. To explain the reason, in order for the cavity mode to appear, the multilayer structures arranged on both sides of the cavity layer 150 must have high reflectivity. The multilayer structure may have high reflectivity. Accordingly, when the thickness of the first medium layer 121 and the second medium layer 122 constituting the multilayer structure is less than 1/4 of the wavelength, the phase change is small when the wave propagates through each medium layer, so constructive interference It doesn't show up well. Therefore, in order for the cavity mode to occur, each medium layer constituting the multilayer structure arranged on both sides of the cavity layer 150 must have a thickness of 1/4 or more of the wavelength.

Accordingly, in order to generate an acoustic and optical cavity mode in the acousto-optic interaction structure 100 , light waves and sound waves having similar wavelength scales may be used. For example, the above-described structure may be configured according to a wavelength scale (eg, 1550 nm) of a light wave used for communication of an optical fiber, and a sound wave having a wavelength scale similar to that of the incident light wave may be incident. However, since the sound wave at this time becomes a very large frequency band of more than the GHz band, acoustic energy loss may occur in the medium. In order to solve this problem, light waves and sound waves having different wavelength scales may be incident by configuring the scale of the above-described unit structure 120 (see FIG. 2 ) large, but in this case, the wavelength scale of the light wave and the unit structure ( 120 (refer to FIG. 2) is different, so radiation loss of light waves may occur, and there is a problem in that the size of the acousto-optic interaction structure 100 increases.

Hereinafter, an acousto-optic interaction structure 100 according to an embodiment of the present invention capable of enhancing the interaction between sound waves and light waves while solving the above problems will be described in detail.

2 is a cross-sectional view illustrating an acousto-optic interaction structure according to a first embodiment of the present invention.

Referring to FIG. 2 , an acousto-optical interaction structure 101 according to a first embodiment of the present invention includes a pair of multi-layer structures 140 and a cavity layer 150 disposed between the pair of multi-layer structures 140 . includes

The multilayer structure 140 includes a structure in which two different medium layers are alternately arranged. For example, the multilayer structure 140 may be configured by sequentially stacking a plurality of unit structures 120 . In this case, each of the plurality of unit structures 120 includes a first medium layer 121 and a second medium layer. The layers 122 may be stacked. In this case, the plurality of unit structures 120 may be stacked along a direction in which the sound wave and the light wave are incident (left arrow in FIG. 2 ).

The multi-layer structure 140 is configured as a pair, and the cavity layer 150 is disposed between the pair of multi-layer structures 140 . At this time, the pair of multi-layer structures 140 and the cavity layer 150 are continuously arranged, and referring to FIG. 2 , the acousto-optic interaction structure 101 according to the first embodiment of the present invention has a multi-layer structure ( 140 ), the cavity layer 150 , and the multi-layer structure 140 may be sequentially stacked in the order of the structure.

The unit structure 120 constituting the multilayer structure 140 may include a first medium layer 121 and a second medium layer 122 having a predetermined thickness. For example, the thickness of the first medium layer 121 may occupy a predetermined ratio of the thickness of the unit structure 120 . Preferably, the thickness of the first medium layer 121 and the second medium layer 122 may be the same.

According to an embodiment of the present invention, the first medium layer 121 and the second medium layer 122 may have different acoustic and optical properties. More specifically, the first medium layer 121 and the second medium layer 122 may have different acoustic impedances and different optical impedances.

According to an embodiment of the present invention, the acoustic impedance and optical impedance of the first medium layer 121 may be relatively small, and the acoustic impedance and optical impedance of the second medium layer 122 adjacent thereto may be relatively large. In this case, the first medium layer 121 and the second medium layer 122 may be formed of a medium having low optical loss in a target wavelength band (eg, a band adjacent to 1550 nm used for optical fiber communication). In addition, the first medium layer 121 and the second medium layer 122 may be formed of a medium having a sufficiently large contrast between the acoustic and optical properties (acoustic impedance and optical impedance). For example, the first medium layer 121 _{may be formed of silicon dioxide (SiO 2} ), and the second medium layer 122 may be formed of silicon (Si). As another example, the first medium layer 121 may be formed of Arsenic triselenide glass (As_2Se_3), and the second medium layer 122 may be formed of Polyethersulphone (PES).

As described above, due to the alternately repeated laminated structure of the first medium layer 121 and the second medium layer 122 , the sound waves and light waves incident to the multilayer structure 140 are transmitted or reflected depending on the wavelength. At this time, constructive interference between reflected waves may occur when a sound wave or light wave of a specific wavelength band is incident on the stacked structure in which the first medium layer 121 and the second medium layer 122 of a certain thickness are periodically repeated, so that the multilayer Structure 140 may have high reflectivity.

According to an embodiment of the present invention, the number of unit structures 120 constituting the multilayer structure 140 may be three or more. When the number of unit structures 120 is less than three, acousto-optic interaction does not occur, and when there are three or more unit structures 120 , acousto-optic interaction may occur. Accordingly, an appropriate number of unit structures 120 may be selected so that the acousto-optic interaction structure 101 has a small size and maximum acousto-optic interaction occurs at a target wavelength.

As described above, in order for the acoustic and optical cavity mode to occur, the thickness of each of the first medium layer 121 and the second medium layer 122 constituting the multilayer structure 140 must have a thickness equal to or greater than 1/4 of the incident wavelength. _{, the thickness a 0} of the unit structure 120 may vary depending on a target wavelength. Accordingly, it is possible to select the unit structure 120 having an appropriate thickness so that the acousto-optic interaction structure 101 has a small size and maximum acousto-optic interaction occurs at a target wavelength.

The cavity layer 150 is a space in which sound waves and light waves incident on the multilayer structure 140 are focused, and is disposed between the pair of multilayer structures 140 . The multilayer structure 140 is disposed on both sides of the cavity layer 150 as the center, and referring to FIG. 2 , the first medium layer 121 included in the multilayer structure 140 based on the cavity layer 150 . and the second medium layer 122 may be symmetrically arranged. For example, the second medium layer 122 having relatively high acoustic impedance and optical impedance may be in contact with both surfaces of the cavity layer 150 . As the multilayer structure 140 in which the first and second medium layers 121 and 122 are alternately arranged on both sides of the cavity layer 150, mirrors that reflect sound waves and light waves on both sides of the cavity layer 150 Since this structure can be arranged, sound waves and light waves can be well focused on the cavity layer 150 .

The cavity layer 150 may function as a space in which the multi-layer structure 140 in contact with both sides functions like a mirror, so that sound waves and light waves are confined by reflection. That is, optical and acoustic cavity modes must exist for light and sound waves incident through the cavity layer 150 . In this case, the cavity layer 150 may have a structure that breaks the regularity of the multilayer structure 140 disposed on both sides. For example, the cavity layer 150 may be formed of a medium having an acoustic impedance and an optical impedance different from a medium in contact with both sides. According to an embodiment of the present invention, the cavity layer 150 may be formed of a medium having smaller acoustic impedance and optical impedance than a medium in contact with both sides. The cavity layer 150 may be made of the same medium (eg, silicon dioxide) as the first medium layer 121 , and the second medium layer 122 may be in contact with both surfaces of the cavity layer 150 .

That is, in the structure in which the cavity layer 150 is disposed between the multilayer structures 140 , sound waves and light waves may be focused on the cavity layer 150 at a specific frequency due to a Fabry-Perot resonance phenomenon. At this time, waves (sound waves and light waves) existing in the cavity layer 150 cause an interference phenomenon, so that only waves of a specific frequency remain and resonate. Sound waves and light waves present in the cavity layer 150 may cause interference. So that the cavity layer 150 may have a predetermined interval (thickness, D). For example, in order for the optical cavity mode to exist, the product of the thickness of the cavity layer 150 and the optical refractive index of the cavity layer 150 may be an integer multiple of a half wavelength of light. Constructive interference can occur only when the phase change that appears as light propagates inside the cavity layer 150 is an integer multiple of 360°. )*2*(thickness of cavity layer)/(wavelength). Accordingly, when the thickness of the cavity layer 150 is determined, the optical refractive index of the cavity layer 150 can be calculated.

The thickness D of the cavity layer 150 may be equal to or greater than 1/8 wavelength of the light wave. Theoretically, in order for the optical cavity mode to appear, the thickness D of the cavity layer 150 having an optical refractive index of n satisfies the relation 2*D=m*(wavelength of light wave)/(optical refractive index)/2 (in the relation m=1, 2, 3, ...), the optical refractive index n of a material existing in nature has a maximum of 4, so the minimum thickness of the cavity layer 150 may be 1/8 wavelength of a light wave.

According to an embodiment of the present invention, the thickness D of the cavity layer 150 may be twice _{the thickness a 0 of the unit structure 120 constituting the multi-layer structure 140 .} As a result of numerically investigating the effect of the thickness of the cavity layer 150 on the acousto-optic interaction in the acousto-optic interaction structure according to the embodiment of the present invention, the thickness D of the cavity layer 150 is a unit structure This is because, when the thickness (a ₀ ) of (120) is doubled, the acousto-optic interaction becomes maximum, and when it becomes larger than that, the acousto-optic interaction decreases.

Hereinafter, the effect of the acousto-optical interaction structure 101 according to the first embodiment of the present invention described above will be described.

3 is a graph showing the effect of the acousto-optical interaction structure 101 according to the first embodiment of the present invention. 3 (a) and (b) are graphs showing the displacement field and the electric field according to the position of the acousto-optic interaction structure 101 at acoustic and optical cavity mode frequencies, respectively. In FIG. 2, the unit structure 120 _{), the thickness (content, f 0s} ) of the first medium layer 121 and the second medium layer 122 is the same, the first medium layer 121 is silicon dioxide, and the second medium layer 122 is silicon. , the thickness D of the cavity layer 150 is _{twice the thickness a 0} of the unit structure 120 , a ₀ = 8.23 μm, f _0s = 0.5, and a unit constituting one multilayer structure 140 . When the number of structures 120 is 5, the optical cavity mode appears at 1550 nm, where the wavelength of the light wave is mainly used for optical fiber communication.

Here, when the thickness a ₀ of the unit structure 120 is 8.23 μm, the optical cavity mode appears when the wavelength of the light wave is 1550 nm. Structures with less than 5% influence on interaction were selected.

Referring to FIG. 3 , it can be seen that a large displacement field and a large electric field appear in the cavity layer (150 in the graphs of FIGS. 3A and 3B ) at acoustic and optical cavity mode frequencies. As described above, high-frequency sound waves must be used for acoustic and optical cavity modes because they interact using sound waves and light waves of similar wavelength scales. is lowered _{However, by adjusting the thickness (a 0} ) of the unit structure 120 constituting the acousto-optic interaction structure 101 according to the first embodiment of the present invention, it is possible to use a low-frequency sound wave with little loss, and the sound wave Since it is possible to reduce the acoustic energy loss of the acousto-optical interaction, as a result, the effect of the acousto-optic interaction can be increased.

On the other hand, the scale value of the interaction between the focused sound wave and light wave can be expressed by the sum of Equations (1) and (2) below, where p is the photoelastic coefficient, ε in Equations (1) and (2) below. is the permittivity, u is the displacement, E is the electric field, and ω is the frequency of the cavity mode.

Equation (1):

Equation (2):

The numerator term in Equation (1) is the value obtained by integrating the squared electric field multiplied by the displacement over space, and the molecular term in Equation (2) represents the sum of the values obtained by multiplying the electric field squared by the displacement at the interface. That is, in common in Equations (1) and (2), the interaction between sound waves and light waves increases when the value obtained by multiplying the electric field squared by the displacement is large. In (a) and (b) of (b), the large displacement field and large electric field appear in 150), confirming that the interaction between sound waves and light waves occurs significantly.

Using the values shown in FIG. 3 , a scale value of the interaction between sound waves and light waves of the acousto-optical interaction structure 101 according to the first embodiment of the present invention applied in FIG. 3 is 471 GHz. This scale value means the degree of modulation of the optical cavity mode frequency, and the larger the value, the more the sound wave can modulate the cavity mode of the light wave.

Meanwhile, another embodiment of the present invention configured to further enhance the interaction between sound waves and light waves will be described below.

4 is a cross-sectional view illustrating an acousto-optical interaction structure according to a second embodiment of the present invention. In the second embodiment to be described below, a description of a configuration overlapping with the first embodiment will be omitted and a different configuration will be mainly described.

Referring to FIG. 4 , in the acousto-optical interaction structure 102 according to the second embodiment of the present invention, the multi-layer structure arranged on both sides of the cavity layer 150 is in contact with the cavity layer 150, respectively. It further includes a medium layer 122'. According to this embodiment, the second 'medium layer 122' may include a structure in which two sub-medium layers made of different media are alternately arranged along the direction in which the sound wave and the light wave travel. In addition, the second medium layer 122 ′ may have the same thickness as any one of the first and second medium layers 121 and 122 , for example, the second medium layer 122 . That is, a multi-layer structure including a structural hierarchy may be disposed on both sides of the hollow layer 150 .

In more detail, the second 'medium layer 122' in contact with both sides of the hollow layer 150 may be formed by successively stacking a plurality of sub-unit structures 220 having a smaller scale than the aforementioned unit structures 120, , the sub-unit structure 220 may include a first sub-medium layer 221 and a second sub-medium layer 222 having an acoustic impedance and an optical impedance different from that of the first sub-medium layer 221 . That is, by inserting a stacked structure having a similar wavelength scale to that of light wave on both sides of the cavity layer 150, a sound wave having a relatively large wavelength scale is transmitted through a structure in which a unit structure 120 having a relatively large size (thickness) is stacked. The controlled light wave having a relatively small wavelength scale may be controlled through a structure in which the sub-unit structures 220 having a relatively small size (thickness) are stacked.

In this case, the first sub-medium layer 221 and the second sub-medium layer 222 may be alternately arranged symmetrically with respect to the hollow layer 150 , and the first sub-medium layer 221 is the first medium layer. It may be made of the same medium as (121), and the second sub-medium layer 222 may be made of the same medium as the second medium layer 122. The first sub-first medium layer 221 and the second sub-medium layer 222 may be formed of a medium having low optical loss in a target wavelength band (eg, a band adjacent to 1550 nm used for optical fiber communication). In addition, the first sub-medium layer 221 and the second sub-medium layer 222 may be formed of a medium having a sufficiently large contrast between acoustic and optical properties (acoustic impedance and optical impedance).

According to an embodiment of the present invention, the acoustic impedance and optical impedance of the first sub-medium layer 221 may be relatively small, and the acoustic impedance and optical impedance of the second sub-medium layer 222 adjacent thereto may be relatively large. . For example, the first sub-medium layer 221 may be made of silicon dioxide, and the second sub-medium layer 222 may be made of silicon.

At this time, the second medium layer 122' in contact with both sides of the cavity layer 150 in the second embodiment of the present invention is the same as the second medium layer 122 in the first embodiment described above. or function similarly. Accordingly, since the content of the second sub-medium layer 222 constituting the sub-unit structure 220 having a constant thickness must be greater than the content of the first sub-medium layer 221 , the thickness of the first sub-medium layer 221 . may be smaller than the thickness of the second sub-medium layer 222 .

Meanwhile, the sub-unit structure 220 may be configured in plurality, and may be configured in three or more. If the number of sub-unit structures 220 is less than three, the role of a reflector for a wave (light wave) cannot be properly performed, and the number of sub-unit structures 220 is large, so the medium layer forming the sub-unit structures 220 (The first sub-medium layer 221 and the second sub-medium layer 222) If the size (thickness) of each is smaller than 1/4 wavelength of the light wave, the optical cavity mode does not appear, so an appropriate number of sub-unit structures is selected can do. For example, in order for the optical cavity mode to appear at 1550 nm, it is preferable that 3 to 9 sub-unit structures 220 are formed.

Hereinafter, the effect of the acousto-optic interaction structure 102 according to the second embodiment of the present invention will be described.

5 to 7 are graphs showing the focusing effect of the acousto-optical interaction structure 102 according to the second embodiment of the present invention. 5 to 7 are graphs showing the displacement field and the electric field according to the position of the acousto-optic interaction structure 102 at acoustic and optical cavity mode frequencies under the same conditions as in FIG. 3 . In addition, the first sub-medium layer 221 is silicon dioxide and the second sub-medium layer 222 is silicon, the number of sub-unit structures 220 and the thickness (content) of the first sub-medium layer 221 . is the result of different

FIG. 5 is a case in which 9 sub-unit structures 220 are respectively disposed on both sides of the cavity layer 150 in the acousto-optical interaction structure 102 of FIG. 4 and f _1s = 0.1408, and FIG. 6 shows the sub-units A case in which there are 8 structures 220 and f _1s = 0.3064, FIG. 7 shows a case in which there are 3 sub-unit structures 220 and f _1s = 0.2834.

5 to 7 , in the acousto-optical interaction structure 102 according to the second embodiment of the present invention in various forms, a large displacement field and a large displacement in the cavity layer 150 at both acoustic and optical cavity mode frequencies and It can be seen that a large electric field appears. When the results in FIGS. 5 to 7 are calculated as a scale value of the interaction between sound waves and light waves obtained by summing the above-mentioned equations (1) and (2), 913 GHz in the case of FIG. 5 and 768 GHz in the case of FIG. , 933 GHz in the case of FIG. Accordingly, it can be seen that the scale value of the interaction between sound waves and light waves is improved by about two times compared to the first embodiment. This is because the sound wave having a relatively large wavelength scale is controlled through the stacked structure of the unit structure 120 having a relatively large size (thickness), and the light wave having a relatively small wavelength scale is controlled by the sub-unit structure having a relatively small size (thickness) (thickness). 220) because it can be controlled. That is, both the incident sound wave and the light wave can reduce the loss in the medium, so that the interaction between the sound wave and the light wave can be greatly improved.

_{In addition, referring to FIGS. 5 to 7 , as the value of f 1s} , which is the content of the first sub-medium layer 221, decreases, that is, the second 'medium layer 122' is similar to that of the first embodiment described above. As the physical properties of the second medium layer 122 of the acousto-optical interaction structure 101 are similar to each other, it can be seen that the acoustic focusing velocity is improved.

As described above, according to an embodiment of the present invention, by providing a common layer 150 for focusing sound waves and light waves in the middle of the multilayer structure 140 in which two different medium layers 121 and 122 are periodically repeated, the sound wave and the interaction of light waves can be strengthened.

In addition, by including a hierarchical structure in the multilayer structure 140 disposed on both sides of the cavity layer 150 , for example, different sub medium layers 221 and 222 are provided in the medium layer in contact with the cavity layer 150 . By inserting a small-scale stacked structure that is repeated periodically, the interaction between sound waves and light waves can be greatly improved.

Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and variations are possible within the scope of the appended claims and the detailed description of the invention and the accompanying drawings. It goes without saying that it falls within the scope of the invention.

100, 101, 102 Acousto-Optical Interaction Structures
120 unit structure
121 first medium layer
122 second medium layer
122'second' media layer
140 multi-layer structure
150 common floors
220 sub-unit structure
221 first sub-medium layer
222 second sub-medium layer

Claims (17)

As a structure in which a plurality of media are stacked to generate an interaction between an incident sound wave and a light wave,
a pair of multilayer structures including a structure in which a first medium layer and a second medium layer having different acoustic impedance and optical impedance are alternately arranged along the direction in which the sound wave and the light wave travel; and
It is disposed between the pair of multilayer structures along the direction in which the sound wave and the light wave travel and includes a cavity layer composed of a medium contacting both sides and a medium having different acoustic impedance and optical impedance,
The first medium layer and the second medium layer are symmetrically arranged with respect to the cavity layer so that the sound wave and the light wave are focused on the cavity layer,
Each of the pair of multilayer structures further comprises a second 'medium layer adjoining the hollow layer,
The second 'medium layer is
Including a structure in which two sub-medium layers having different acoustic impedance and optical impedance and having a thickness smaller than that of the first medium layer and the second medium layer are alternately arranged along the direction in which the sound wave and the light wave travel working structure. The method of claim 1,
The second medium layer has an acoustic impedance and an optical impedance greater than that of the first medium layer,
Each of the pair of multilayer structures is
and a structure in which a unit structure including the first medium layer and the second medium layer is stacked in plurality along a direction in which the sound wave and the light wave travel. 3. The method of claim 2,
and the cavity layer is continuously arranged with the pair of multilayer structures along a direction in which the sound waves and light waves travel, and is made of the same medium as the first medium layer. 3. The method of claim 2,
and the thickness of the cavity layer is at least 1/8 wavelength of the light wave. 3. The method of claim 2,
and the thickness of the cavity layer is twice the thickness of each of the unit structures. 3. The method of claim 2,
wherein the product of the thickness of the cavity layer and the optical refractive index of the cavity layer is an integer multiple of one half wavelength of the light wave. 6. The method of claim 5,
and the thickness of the first medium layer and the second medium layer are the same. 8. The method of claim 7,
The first medium layer is made of silicon dioxide (SiO ₂ ), and the second medium layer is made of silicon (Si). delete The method of claim 1,
The second 'medium layer is
an acousto-optic interaction structure having the same thickness as any one of the first medium layer and the second medium layer. 11. The method of claim 10,
The two sub-medium layers are
a first sub-medium layer, and a second sub-medium layer having acoustic impedance and optical impedance greater than those of the first sub-medium layer;
The second 'medium layer,
The acousto-optic interaction structure, wherein the sub-unit structure including the first sub-medium layer and the second sub-medium layer has a structure in which a plurality of sub-unit structures are stacked in a direction in which the sound waves and light waves travel. 12. The method of claim 11,
The acousto-optic interaction structure, wherein the first sub-medium layer and the second sub-medium layer are symmetrically arranged with respect to the cavity layer. 13. The method of claim 12,
The first sub-medium layer is made of the same medium as the first medium layer,
and the second sub-medium layer is made of the same medium as the second medium layer. 14. The method of claim 13,
and a thickness of the first sub-medium layer is less than a thickness of the second sub-medium layer. 14. The method of claim 13,
The second 'medium layer is composed of three or more sub-unit structures, acousto-optic interaction structure. 14. The method of claim 13,
The second 'medium layer is
An acousto-optic interaction structure, which is interposed between the cavity layer and the first medium layer and is continuously arranged and has the same thickness as the second medium layer. 11. The method of claim 10,
and the second' medium layer is continuously arranged between the cavity layer and the other of the first and second medium layers.

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