KR20200121731A - Structure for acousto-optic interaction - Google Patents

Abstract

According to one embodiment of the present invention, an acousto-optic interaction structure is a stacked structure for inducing an interaction between incident acoustic wave and incident optical wave, wherein the acousto-optic interaction structure includes: a pair of multi-layered structures consisting of a plurality of unit structures which are successively stacked in a direction in which the acoustic wave and the optical wave propagate; and a cavity layer disposed between the pair of multi-layered structures, wherein each of the plurality of unit structures is formed by stacking a first medium layer and a second medium layer having an acoustic impedance and an optical impedance different from the first medium layer, and the pair of multi-layer structures and the cavity layer are sequentially arranged, and the first medium layer and the second medium layer are alternately arranged symmetrically with respect to the cavity layer. The present invention provides the multi-layered structure for enhancing an interaction between incident acoustic waves and optical waves.

Description

Acousto-optic interaction structure {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 an incident sound wave and a light wave.

Acousto-optic 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 interaction can be used in devices that control light waves such as optical modulators, switches, deflectors, filters, and frequency shifters. The efficiency and performance of this device can be improved by increasing the acousto-optic interaction. Recently, researches on increasing the acousto-optic interaction have been actively conducted.

For example, in order to increase the acousto-optic interaction, an attempt has been made to use a light wave having a slow speed or a high frequency sound wave having a similar wavelength scale to control a light wave of a short wavelength.

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

According to an embodiment of the present invention, as a laminate structure in which a plurality of media are stacked to generate an interaction between an incident sound wave and a light wave, two media layers having different acoustic impedance and optical impedance are provided. A pair of multi-layered structures including structures alternately arranged along the 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 formed of a medium in contact with both surfaces and a medium having different acoustic impedances and optical impedances, and the sound wave and the light wave The two media layers are arranged symmetrically with respect to the cavity layer so that the is 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 includes the first medium layer and the second medium layer. The unit structure consisting of may include a structure in which a plurality of layers are stacked along the direction in which the sound and light waves travel.

The cavity layer may be continuously arranged with the pair of multilayer structures along a direction in which the sound 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 equal to or greater than 1/8 wavelength of the light wave.

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

The product of the thickness of the cavity layer and the optical refractive index of the cavity layer may be an integer multiple of a half wavelength of the light wave.

The first medium layer and the second medium layer may have the same thickness.

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

The hollow layer is continuously arranged with the pair of multilayer structures along a direction in which the sound and light waves travel, and the second medium layer may contact both surfaces of the hollow layer.

Each of the pair of multilayer structures further includes a second' medium layer in contact with the common layer, and the second' medium layer includes two sub medium layers having different acoustic impedances and optical impedances in a direction in which the sound and light waves travel It includes a structure that is alternately arranged along each other, 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 an acoustic impedance and an optical impedance greater than that of the first sub medium layer, and the second' medium layer comprises 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 and light waves travel.

The first sub-medium layer and the second sub-medium layer may be symmetrically arranged based on the cavity 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.

The thickness of the first sub medium layer may be smaller than the thickness of the second sub medium layer.

The 2'medium layer may have three or more sub-unit structures.

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

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

According to an embodiment of the present invention, by providing a cavity layer that focuses sound and light waves in the center of a structure in which a plurality of media are stacked, the interaction between sound and light waves may be enhanced.

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

1 is a perspective view showing an acousto-optic interaction structure according to an embodiment of the present invention.
2 is a cross-sectional view showing 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 showing an acoustooptic interaction structure according to a second embodiment of the present invention.
5 to 7 are graphs showing the effect of the acousto-optic interaction structure according to the second embodiment of the present invention.

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

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

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

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

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

The 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, the 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, when 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 an embodiment of the present invention, the acousto-optic interaction structure 100 has a cavity layer 150 having a predetermined thickness D in the center, and the first medium layer 121 and the second medium layer described above are The multilayer structure in which 122 is stacked and the cavity layer 150 may be continuously stacked. That is, the cavity layer 150 may be inserted in the center of the 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 order of arrangement of the first medium layer 121 and the second medium layer 122 arranged on both sides of the cavity layer 150 may be symmetrical. In this case, a multilayer structure arranged on both sides of the cavity layer 150 may function as a mirror having high reflectivity. In particular, the greater the contrast between the acoustic impedance and the optical impedance of the first medium layer 121 and the second medium layer 122, the higher the reflectance. Accordingly, sound waves and light waves incident on the acousto-optic interaction structure 100 may be focused on the cavity layer 150 due to the high reflectance of the multilayer structure disposed on both sides of the cavity layer 150, Action can be enhanced.

In more detail, in the structure in which the first medium layer 121 and the second medium layer 122 are alternately arranged with a high 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 are reflected, causing constructive interference between waves transmitted multiple times or reflected multiple times. Accordingly, in a structure in which a medium having a large impedance contrast for sound and light waves is alternately arranged so that both incident sound and light waves can be completely reflected (to have a very high reflectivity for incident sound and light waves), the cavity in the center ( cavity), two waves at a specific frequency cause constructive interference in the cavity, resulting in a phenomenon in which the amplitude becomes very large and focused. This phenomenon is called an acoustic and optical cavity mode, and a phenomenon in which two waves interact strongly in the cavity mode appears.

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 and second medium layers 121 and 122 is 1/ of the incident wavelength. It must have a thickness of 4 or more. Explaining the reason, in order for the cavity mode to appear, the multilayer structure arranged on both sides of the cavity layer 150 must have high reflectance. When the wave propagates through the multilayer structure, the phase difference between the reflected waves becomes 360°. The multilayer structure can have a 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, constructive interference due to the small phase change when the wave propagates through each medium layer This does not appear 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 the acoustic and optical cavity modes 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 in accordance with the wavelength scale (eg, 1550 nm) of light waves used for communication of optical fibers, and sound waves having a wavelength scale similar to the incident light wave may be incident. However, since the sound wave at this time becomes a very large frequency band above the GHz band, acoustic energy loss may occur in the medium. In order to solve this problem, the scale of the above-described unit structure 120 (refer to FIG. 2) may be configured to allow light waves and sound waves having different wavelength scales to be incident, but in this case, the wavelength scale of the light wave and the unit structure ( 120 (refer to FIG. 2 ), there is a problem that radiation loss of light waves may occur, and 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-described problems will be described in detail.

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

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

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

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

The unit structure 120 constituting the multilayer structure 140 may be composed of 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 certain ratio of the thickness of the unit structure 120. Preferably, the first medium layer 121 and the second medium layer 122 may have the same thickness.

According to the 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 an acoustic impedance and an optical impedance different from each other.

According to the 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 acoustic and optical properties (acoustic impedance and optical impedance). For example, the first medium layer 121 may be made of silicon dioxide (SiO ₂ ), and the second medium layer 122 may be made of silicon (Si). As another example, the first medium layer 121 may be made of Arsenic triselenide glass (As_2Se_3), and the second medium layer 122 may be made of polyethersulphone (PES).

As described above, due to the stacked structure of the first and second media layers 121 and 122 that are alternately repeated, sound waves and light waves incident on the multilayer structure 140 may be transmitted or reflected depending on the wavelength. At this time, when a sound wave or a light wave of a specific wavelength band is incident on the stacked structure in which the first and second media layers 121 and 122 of a certain thickness are periodically repeated, constructive interference between the reflected waves may occur. Structure 140 may have a 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, an acousto-optic interaction does not occur, and when the number of unit structures 120 is three or more, an acousto-optic interaction may occur. Accordingly, it is possible to select an appropriate number of unit structures 120 so that the size of the acousto-optic interaction structure 101 is small and the maximum acousto-optic interaction occurs at a target wavelength.

As described above, in order for the acoustic and optical cavity modes to occur, the first medium layer 121 and the second medium layer 122 constituting the multilayer structure 140 must each have a thickness of 1/4 or more of the incident wavelength. , The thickness a ₀ of the unit structure 120 may vary according to a target wavelength. Accordingly, while the size of the acousto-optic interaction structure 101 is small, a unit structure 120 having an appropriate thickness may be selected so that the maximum acousto-optic interaction occurs at a target wavelength.

The cavity layer 150 is a space where sound waves and light waves incident on the multilayer structure 140 are focused, and is disposed between the pair of multilayer structures 140. A multilayer structure 140 is disposed on both sides of the cavity layer 150 as the center, and referring to FIG. 2, a 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, a second medium layer 122 having relatively large 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 is disposed, a mirror reflecting sound and light waves on both sides of the cavity layer 150 Since this arrangement can be made, 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 sound waves and light waves are confined by reflection because the multilayer structure 140 in contact with both sides functions like a mirror. That is, optical and acoustic cavity modes must exist for light waves 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 that of a medium in contact with both sides. According to the exemplary embodiment of the present invention, the cavity layer 150 may be formed of a medium having an acoustic impedance and an optical impedance smaller than that of a medium contacting both sides. The cavity layer 150 may be formed of the same medium as the first medium layer 121 (eg, silicon dioxide), and the second medium layer 122 may be in contact with both surfaces of the cavity layer 150.

That is, in a structure in which the cavity layer 150 is disposed between the multilayer structure 140, sound waves and light waves may be focused on the cavity layer 150 at a specific frequency by a Fabry-Perot resonance phenomenon. At this time, the waves (sound waves and light waves) existing inside the cavity layer 150 cause interference, so that only waves of a specific frequency remain and resonate, and the sound waves and light waves existing in the cavity layer 150 may cause interference. So that the cavity layer 150 may have a predetermined spacing (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 the half wavelength of light. Constructive interference can occur only when the phase change that occurs as light propagates inside the cavity layer 150 is an integer multiple of 360°, and the phase that changes as light propagates through the cavity layer 150 is 360°* (optical refractive index of the cavity layer) This is because it can be calculated as )*2*(thickness of the cavity layer)/(wavelength). Accordingly, when the thickness of the cavity layer 150 is determined, the optical refractive index of the cavity layer 150 may be calculated.

The thickness D of the cavity layer 150 may be equal to or greater than 1/8 wavelength of the light wave. In theory, for the optical cavity mode to appear, the thickness (D) of the cavity layer 150 having an optical refractive index of n satisfies the relationship 2*D=m*(wavelength of light wave)/(optical refractive index)/2 (from the relationship m = 1, 2, 3, ...), since the maximum optical refractive index (n) of a material existing in nature is 4, the minimum thickness of the cavity layer 150 may be 1/8 wavelength of the 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 multilayer 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 When it is twice the thickness (a ₀ ) of (120), the acousto-optic interaction becomes the maximum value, and when it is greater than that, the acousto-optic interaction decreases.

Hereinafter, the effects of the acoustooptic interaction structure 101 according to the first embodiment of the present invention will be described.

3 is a graph showing the effect of the acousto-optic interaction structure 101 according to the first embodiment of the present invention. 3A and 3B are graphs showing the displacement field and the electric field according to the position of the acoustooptic interaction structure 101 at the acoustic and optical cavity mode frequencies, respectively. In FIG. 2, the unit structure 120 ), the first medium layer 121 and the second medium layer 122 have the same thickness (content, f _0s ), 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 The number of structures 120 is 5, and the optical cavity mode appears at 1550 nm where the wavelength of light waves is mainly used for communication of optical fibers.

Here, in the case where 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, due to the loss of acoustic energy among the thicknesses of the many unit structures 120 A structure with less than 5% impact on interaction was 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 (a) and (b) of FIG. 3) at the acoustic and optical cavity mode frequencies. As described above, since the interaction is caused by using sound waves and light waves of similar wavelength scale, high-frequency sound waves must be used for the acoustic and optical cavity modes. 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, a low-frequency sound wave with low loss can be used, and the sound wave Since it is possible to reduce the loss of acoustic energy, the effect of the acousto-optic interaction can be increased as a result.

On the other hand, the measure of the interaction between the focused sound wave and the light wave can be expressed as the sum of the following equations (1) and (2). In the following equations (1) and (2), p is the photoelastic coefficient, ε 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 by the displacement over space, and the numerator term in Equation (2) represents the sum of the squared electric field multiplied by the displacement at the interface. In other words, in Equations (1) and (2), the interaction between sound waves and light waves increases when the square of the electric field multiplied by the displacement is large, so the cavity layer (Fig. 3) in Figs. 3(a) and (b) From the results of the large displacement field and the large electric field in the graphs (a) and (b) of 150), it can be confirmed that the interaction between the sound wave and the light wave occurs greatly.

Using the value shown in FIG. 3, a measure of the interaction between sound waves and light waves of the acousto-optic 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 it means that the sound wave can modulate the cavity mode of the light wave more.

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 showing an acoustooptic interaction structure according to a second embodiment of the present invention. In the second embodiment to be described below, descriptions of configurations overlapping with those of the first embodiment will be omitted, and different configurations will be mainly described.

Referring to FIG. 4, in the acousto-optic interaction structure 102 according to the second embodiment of the present invention, a multilayer structure arranged on both sides of the cavity layer 150 is a second ′ in contact with the cavity layer 150, respectively. It further includes a medium layer 122 ′. According to the present 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 sound waves and light waves 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 cavity layer 150.

In more detail, the second'medium layer 122' in contact with both sides of the common layer 150 may be formed by successively stacking a plurality of sub-unit structures 220 having a smaller scale than the unit structure 120 described above. , 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 those of the first sub medium layer 221. That is, by inserting a stacked structure having a similar wavelength scale to a light wave on both sides of the cavity layer 150, a sound wave having a relatively large wavelength scale can be obtained through a stacked structure of a unit structure 120 having a relatively large size (thickness). A light wave that is controlled and has 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 cavity layer 150, and the first sub-medium layer 221 is a first medium layer. It is made of the same medium as 121, the second sub medium layer 222 may be made of the same medium as the second medium layer 122. The first sub 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 (for example, 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 made 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.

In this case, the second medium layer 122 ′ in contact with both sides of the cavity layer 150 in the second exemplary embodiment of the present invention is the same as the second medium layer 122 in the first exemplary embodiment. Or function similarly. Accordingly, since the content of the second sub-medium layer 222 constituting the sub-unit structure 220 of a certain 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 composed of a plurality, but may be composed of three or more. If the number of sub-unit structures 220 is less than 3, the role of a reflector for waves (light waves) cannot be properly performed, and the number of sub-unit structures 220 is large, so that the medium layer constituting the sub-unit structure 220 (The first sub-medium layer 221 and the second sub-medium layer 222) When 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 the sub-unit structure 220 is composed of 3 to 9 parts.

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 acoustooptic 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 the 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, 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 It is the result of doing differently.

FIG. 5 is a case in which 9 sub-unit structures 220 are disposed on both sides of the cavity layer 150 in the acousto-optic interaction structure 102 of FIG. 4, and f _{1 s} = 0.1408, and FIG. 6 is a sub-unit There are 8 structures 220 and f _1s = 0.3064, and FIG. 7 shows a case where there are 3 sub unit structures 220 and f _1s = 0.2834.

5 to 7, in the acousto-optic interaction structure 102 according to the second embodiment of the present invention in various forms, both in the cavity layer 150 at the acoustic and optical cavity mode frequencies, a large displacement field and It can be seen that a large electric field appeared. If the results in FIGS. 5 to 7 are calculated as a measure of the interaction between the sound wave and the light wave, which is the sum of Equations (1) and (2) described above, 913 GHz in FIG. 5 and 768 GHz in FIG. 6 In the case of FIG. 7, it is 933 GHz. Therefore, compared with the first embodiment, it can be seen that the measure of the interaction between sound waves and light waves is improved by about twice. This is controlled through a stacked structure of a unit structure 120 having a relatively large size (thickness) for sound waves having a relatively large wavelength scale, and a sub-unit structure having a relatively small size (thickness) for light waves having a relatively small wavelength scale ( 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 As the physical properties of the second medium layer 122 of the acousto-optic interaction structure 101 become similar, it can be seen that the acoustic focusing speed is improved.

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

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 media layers 221 and 222 are formed in the media layer in contact with the cavity layer 150 By inserting a stacked structure of a small scale that repeats periodically, the interaction between sound waves and light waves can be greatly improved.

Although a preferred embodiment of the present invention has been described above, the present invention is not limited thereto, and it is possible to implement various modifications within the scope of the claims, the detailed description of the invention, and the accompanying drawings. It is natural to fall within the scope of the invention.

100, 101, 102 Acousto-optic interaction structures
120 unit structure
121 first medium layer
122 Second medium layer
122'second' medium layer
140 multi-layered structure
150 cavity floor
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 two medium layers having different acoustic impedances and optical impedances are arranged alternately with each other along a direction in which the sound and light waves travel; And
It includes 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 in contact with both surfaces and a medium having different acoustic impedances and optical impedances,
The two media layers are arranged symmetrically with respect to the cavity layer so that the sound and light waves are focused on the cavity layer. The method of claim 1,
The two media 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,
Each of the pair of multilayer structures
An acousto-optic interaction structure including a structure in which a unit structure consisting of the first medium layer and the second medium layer is stacked in plural along a direction in which the sound and light waves travel. The method of claim 2,
The cavity layer is continuously arranged with the pair of multilayer structures along the direction in which the sound and light waves travel, and is made of the same medium as the first medium layer. The method of claim 2,
The thickness of the cavity layer is equal to or greater than 1/8 wavelength of the light wave. The method of claim 2,
The thickness of the cavity layer is twice the thickness of each of the unit structures. The method of claim 2,
The acousto-optic interaction structure, wherein a product of the thickness of the cavity layer and the optical refractive index of the cavity layer is an integer multiple of a half wavelength of the light wave. The method of claim 5,
The thickness of the first medium layer and the second medium layer is the same. 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), an acousto-optic interaction structure. The method of claim 2,
The cavity layer is continuously arranged with the pair of multilayer structures along the direction in which the sound and light waves travel,
The acousto-optic interaction structure, wherein the second medium layer contacts each side of the cavity layer. The method of claim 2,
Each of the pair of multilayer structures further includes a second' medium layer in contact with the common layer,
The second' medium layer
Including a structure in which two sub-medium layers having different acoustic impedance and optical impedance are alternately arranged along the direction in which the sound wave and the light wave travel, and having the same thickness as one of the two medium layers, Working structure. The method of claim 10,
The two sub medium layers,
A first sub medium layer, and a second sub medium layer having an acoustic impedance and an optical impedance greater than that of the first sub medium layer,
The second' medium layer,
An acousto-optic interaction structure having a structure in which a plurality of sub-unit structures composed of the first sub-medium layer and the second sub-medium layer are stacked along a direction in which the sound and light waves travel. 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. The method of claim 12,
The first sub medium layer is made of the same medium as the first medium layer,
The second sub medium layer is made of the same medium as the second medium layer, an acousto-optic interaction structure. The method of claim 13,
The thickness of the first sub medium layer is smaller than the thickness of the second sub medium layer, an acousto-optic interaction structure. The method of claim 13,
The second' medium layer is composed of three or more sub-unit structures, an acousto-optic interaction structure. The method of claim 13,
The second' medium layer
An acousto-optic interaction structure interposed between the cavity layer and the first medium layer and arranged in succession and having the same thickness as the second medium layer. The method of claim 10,
The second' medium layer is continuously arranged between the cavity layer and the other of the two medium layers.

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