Opto-mechanical array element

Abstract

An optomechanical array element (100) is configured from a rod-shaped matrix (101) having a circular outer shape, and is provided with, in the matrix (101), a plurality of small diameter coupling parts (102) formed by reducing the diameter at equal intervals, and a bottle-type resonance part (103) between adjacent ones of the plurality of coupling parts (102). The bottle-type resonance part (103) is a whispering gallery mode optical resonator, and each of the plurality of coupling parts (102) is able to propagate mechanical vibration of the bottle-type resonance part (103) adjacent to each other.

Description

[Technical field]

[0001] The present invention relates to an optomechanical array element consisting of an optical resonator and a mechanical resonator. [Background technology]

[0002] In recent years, signal processing technology using mechanical resonators has been attracting attention. For example, a membrane array structure has been proposed in which membrane-type mechanical resonators are arrayed (Non-Patent Document 1, Non-Patent Document 2). This structure can mount multiple MEMS sensors and actuators as an integrated element, and by utilizing the mechanical vibration coupling between membrane structures, it is possible to propagate and transfer information (signals) carried by the amplitude and phase of mechanical vibration in the array direction. This is expected to lead to the realization of a low-power signal transfer network mainly using mechanical resonators.

[0003] On the other hand, in order to incorporate such a mechanical resonator network as an IoT element into a node of a conventional optical network, highly efficient opto-mechanical conversion is required in each mechanical resonator. Highly efficient opto-mechanical conversion in a single mechanical resonator has been realized, for example, by coupling an optical resonator with a strong light confinement effect to a mechanical resonator (Non-Patent Document 3). Mechanical-opto-mechanical coupling using a microbottle resonator has also been proposed (Non-Patent Document 4). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] D. Hatanaka et al., "Phonon waveguides for electromechanical circuits", Nature Nanotechnology, vol. 9, pp. 520-524, 2014. [Non-Patent Document 2] E. Romero et al., "Propagation and Imaging of MechanicalWaves in a Highly Stressed Single-Mode Acoustic Waveguide", Physical Review Applied, vol. 11, 064035, 2019. [Non-Patent Document 3] TJ Kippenberg and KJ Vahala, "Cavity Opto-Mechanics", Optics Express, vol. 15, no. 22, pp. 17172-17205, 2007. [Non-Patent Document 4] M. Asano et al., "Observation of optomechanical coupling in a microbottle resonator", Laser & Photonics Reviews, vol. 10, Issue 4, 2016. Summary of the Invention [Problem to be solved by the invention]

[0005] However, attempting to network the above-mentioned optomechanical resonator structures in an array is not easy and has not yet been realized. In fact, it is technically difficult to incorporate an optical resonator into each of the conventional membrane structures, and it is difficult to realize it with a configuration based on the conventional mechanical resonator array structure.

[0006] The present invention has been made to solve the above problems, and has an object to provide an optomechanical array element in which a plurality of optomechanical resonator structures are connected in an array. [Means for solving the problem]

[0007] The optomechanical array element of the present invention comprises a rod-shaped base body having a circular outer shape, a plurality of narrow-diameter connecting portions formed by narrowing the diameter at equal intervals, and bottle-shaped resonating portions between adjacent ones of the plurality of connecting portions, and the bottle-shaped resonating portions are configured as whispering gallery mode optical resonators. Effect of the Invention

[0008] As described above, according to the present invention, a plurality of bottle-shaped resonating portions, which serve as whispering gallery mode optical resonators, are connected together by connecting portions, making it possible to provide an optomechanical array element in which a plurality of optomechanical resonator structures are connected in an array. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing the configuration of an optomechanical array element according to an embodiment of the present invention. [Figure 2A] FIG. 2A is a diagram showing a partial configuration of an opto-mechanical array element according to an embodiment of the present invention. [Figure 2B] FIG. 2B is a characteristic diagram showing the whispering gallery type optical mode of the bottle-shaped resonating unit 103. As shown in FIG. [Figure 3A] FIG. 3A is a diagram illustrating the principle of excitation and measurement of mechanical vibrations of an optomechanical array element according to an embodiment of the present invention. [Figure 3B] FIG. 3B is a diagram illustrating the principle of excitation and measurement of mechanical vibrations of the optomechanical array element according to the embodiment of the present invention. [Figure 4A] FIG. 4A is a diagram showing the configuration of another optomechanical array element according to an embodiment of the present invention. [Figure 4B] FIG. 4B is a diagram showing the configuration of another optomechanical array element according to an embodiment of the present invention. [Figure 5A] FIG. 5A is a configuration diagram showing the configuration of an optomechanical array element according to Example 1 of the embodiment of the present invention. [Figure 5B] FIG. 5B is a micrograph of the optomechanical array element according to Example 1 of the embodiment of the present invention. [Figure 5C] FIG. 5C is a characteristic diagram showing a mechanical vibration signal measured by first measuring instrument 108a connected to first optical fiber 105a. [Figure 5D] FIG. 5D is a characteristic diagram showing a mechanical vibration signal measured by second measuring instrument 108b connected to first optical fiber 105a. [Figure 6A] FIG. 6A is a configuration diagram showing the configuration of an optomechanical array element according to Example 2 of the embodiment of the present invention. [Figure 6B] FIG. 6B is a configuration diagram showing the configuration of another optomechanical array element according to Example 2 of the embodiment of the present invention. [Figure 7] FIG. 7 is a diagram showing the configuration of an optomechanical array element according to Example 3 of the embodiment of the present invention. [Figure 8] FIG. 8 is a configuration diagram showing the configuration of an optomechanical array element according to Example 4 of the embodiment of the present invention. [Figure 9] FIG. 9 is a configuration diagram showing the configuration of an optomechanical array element according to Example 5 of the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An optomechanical array element 100 according to an embodiment of the present invention will be described below with reference to Fig. 1. The optomechanical array element 100 is composed of a rod-shaped base body 101 having a circular outer shape. The base body 101 can be composed of a fiber made of glass or plastic.

[0011] The base body 101 is provided with a plurality of narrow-diameter connecting parts 102 formed by narrowing the diameter at equal intervals, and a bottle-shaped resonating part 103 between adjacent connecting parts 102. The connecting parts 102 are parts having a narrower diameter than the bottle-shaped resonating parts 103. The bottle-shaped resonating parts 103 have a so-called bottle-shaped shape. The connecting parts 102 having a narrower diameter and the bottle-shaped resonating parts 103 having a wider diameter are alternately formed on the cylindrical base body 101. The optomechanical array element 100 can be said to have a structure in which a plurality of bottle-shaped resonating parts 103 are connected by the connecting parts 102. The bottle-shaped resonating part 103 is an optical resonator in a whispering gallery mode. The bottle-shaped resonating part 103 is a mechanical resonator having a mechanical vibration mode in the radial direction or the deflection angle direction. Each of the plurality of connecting parts 102 is capable of propagating the mechanical vibration of the adjacent bottle-shaped resonating part 103.

[0012] According to the optomechanical array element of the embodiment, for example, as shown in Fig. 2A, by arranging the input / output section 106 of the optical fiber 105 close to a region of the bottle-shaped resonator 103 having a large density of states, it is possible to inject photons into the whispering gallery mode 131 of the bottle-shaped resonator 103 to excite optical resonance. As shown in Fig. 2B, the bottle-shaped resonator 103 has a whispering gallery type optical mode with an axial light intensity (density of states) distribution.

[0013] In addition, the optical resonance of the whispering gallery mode of the bottle-shaped resonator 103 can be read out by the optical fiber 105. The input / output unit 106 is, for example, a region where the coating of the optical fiber 105 is removed and the cladding layer is thinned to allow light to leak out from the core. The above-mentioned excitation and readout are possible by arranging the input / output unit 106 close enough to allow the core of the optical fiber 105 and the whispering gallery mode of the bottle-shaped resonator 103 to be optically coupled. In addition, the above-mentioned excitation and readout can also be performed by using an optical element such as a prism.

[0014] The optical resonance described above is periodically modulated by the influence of mechanical resonance that vibrates at the inherent frequency of the bottle-shaped resonating portion 103. That is, in the optomechanical array element 100, light and mechanical vibrations interact with each other. Therefore, by using the optomechanical array element 100, it is possible to read the magnitude of mechanical vibrations with high sensitivity through modulation of optical resonance. By utilizing this principle, it is possible to realize excitation, control, and measurement of minute mechanical vibrations (displacements).

[0015] A specific principle of excitation and measurement of mechanical vibration will be described with reference to FIG. 3A, taking the radial vibration mode of the bottle-shaped resonator 103 as an example. In FIG. 3A, the dotted line indicates the propagation of light, and the solid line indicates the direction of mechanical vibration. The mechanical vibration of the bottle-shaped resonator 103 is excited by radiation pressure generated by photons in the whispering gallery mode that orbit the radial periphery of the bottle-shaped resonator 103 many times. The whispering gallery optical mode is a mode that orbits the bottle-shaped resonator 103 while being totally reflected in the deflection angle direction, so that it is possible to generate radial radiation pressure at each point of total reflection.

[0016] On the other hand, the mechanical vibration of the bottle-shaped resonator 103 can be measured through the change in the phase or frequency of light that occurs when the effective propagation length of the optical mode changes due to radial displacement [Fig. 3B]. In Fig. 3B, the solid line indicates the state without displacement, and the dotted line indicates the state with displacement.

[0017] 4A, by bridging multiple optomechanical array elements 100 using thinned optical fibers 105 as optical waveguides, signal communication between elements can be implemented by light. By forming the base body 101 from a material whose connecting parts 102 are bendable, and by using a bendable material as the cylindrical base material as shown in FIG. 4B, an optomechanical array element 100' having flexibility in shape can be formed.

[0018] The opto-mechanical array element 100 of the embodiment enables overlap (coupling) between mechanical vibration modes by appropriately adjusting and designing the spacing between the bottle-shaped resonating sections 103, which are structural units (the length in the connecting direction of the connecting sections 102), thereby making it possible to propagate and transfer mechanical vibrations in the array direction (connecting direction).

[0019] The optomechanical array element 100 according to the embodiment can directly process information as mechanical vibrations of vibration sensors, actuators, and filter nodes on a one-dimensional array. Furthermore, by utilizing parametric optomechanical interaction for mechanical vibrations propagating between multiple bottle-shaped resonators 103, it is possible to realize signal amplification and attenuation of vibration propagation by light.

[0020] Moreover, the base 101 can be made of a material that allows the connecting portion 102 to twist around an axis. With this configuration, it becomes possible to simultaneously control the optical and mechanical characteristics of each bottle-shaped resonator 103 incorporated in the optomechanical array element 100 by applying tension or torsional stress from both ends of the optomechanical array element 100.

[0021] Moreover, the base body 101 can be cylindrical. With this configuration, it is possible to dispose a silica optical fiber having a core region that allows light to propagate in the axial direction of the cylinder in the center of the cylindrical base body 101, and it is possible to read the tension and torsional stress applied to the optomechanical array element 100 using the light propagating through this optical fiber (core).

[0022] By using the optomechanical array element 100 according to the embodiment, it is possible to sense disturbances by light by utilizing the fact that mechanical resonance in the bottle-shaped resonating unit 103 of each unit structure is modulated by disturbance. In addition, by using the optomechanical array element 100, it is possible to control fluid by vibration of the multiple bottle-shaped resonating units 103 by making the inside of the hollow structure of the base body 101 a flow path.

[0023] The present invention will be described in more detail below with reference to examples.

[0024] [Example 1] First, Example 1 will be described with reference to FIG. 5A. In Example 1, a silica optical fiber was used as a base, and a fiber processing machine was used to form connecting portions 102 at equal intervals to form a plurality of bottle-shaped resonating portions 103, thereby fabricating an opto-mechanical array element 100. A constriction having a diameter of 70 μm was formed in a silica optical fiber clad having a diameter of 80 μm to form the connecting portion 102. In addition, the connecting portions 102 were formed at intervals of 550 μm to form nine bottle-shaped resonating portions 103, thereby fabricating an opto-mechanical array element 100. A micrograph of a portion of the actually fabricated opto-mechanical array element 100 is shown in FIG. 5B.

[0025] Furthermore, an input / output section of a first optical fiber 105a is optically coupled to the bottle-shaped resonator 103 at one end of the optomechanical array element 100, and an input / output section of a second optical fiber 105b is optically coupled to the bottle-shaped resonator 103 at the other end. The input / output section of each optical fiber is a section in which the cladding diameter is thinned to approximately the optical wavelength (up to 1.5 μm). Each optical fiber is fixed with the input / output section brought close to the corresponding bottle-shaped resonator 103, for example, to approximately the optical wavelength.

[0026] The first optical fiber 105a has one end connected to a first light source 107a and the other end connected to a first measuring device 108a. The second optical fiber 105b has one end connected to a second light source 107b and the other end connected to a second measuring device 108b. Each light source may be, for example, a laser device. Each measuring device may be composed of a light receiving element such as a photodiode.

[0027] By introducing light into the first optical fiber 105a, mechanical vibrations 132 are excited by light in the optomechanical array element 100. Meanwhile, by measuring a change in the light introduced into the second optical fiber 105b with the second measuring device 108b, the mechanical vibrations 132 generated in the optomechanical array element 100 are measured.

[0028] By appropriately adjusting the frequency of the laser light emitted from first light source 107a, a mechanical vibration signal having a peak near 49.2 MHz as shown in Fig. 5C is measured by first measuring device 108a connected to first optical fiber 105a. At the same time, by adjusting the frequency of the laser light emitted from second light source 107b, a signal having a peak near 49.2 MHz as shown in Fig. 5D is measured by second measuring device 108b.

[0029] The laser power of the second light source 107b is 10 μW, which is three orders of magnitude smaller than that of the first light source 107a, and the excess vibration excitation by the detection laser is suppressed to a negligible level. The experimental results show that vibration is propagated between the bottle-shaped resonator 103 on one end side of the optomechanical array element 100 and the bottle-shaped resonator 103 on the other end side, indicating that a one-dimensional optomechanical array element has been realized.

[0030] [Example 2] Next, Example 2 will be described with reference to Figs. 6A and 6B. In Example 2, an opto-mechanical array element 100 similar to that in Example 1 was fabricated and used. In Example 2, a first optical fiber 105a and a second optical fiber 105b were provided, similar to that in Example 1. Although not shown, a first light source and a first measuring instrument are connected to the first optical fiber 105a. Furthermore, although not shown, a second light source and a second measuring instrument are connected to the second optical fiber 105b.

[0031] In the second embodiment, an input / output portion of a third optical fiber 105c is optically coupled to the bottle-shaped resonator 103 at the center of the optomechanical array device 100. A third light source (not shown) is connected to one end of the third optical fiber 105c, and a third measuring device (not shown) is connected to the other end of the third optical fiber 105c.

[0032] The vibration 133 excited in the bottle-shaped resonator 103 at one end by the light from the first light source for excitation reaches the bottle-shaped resonator 103 at the center. At this time, by setting the frequency of the light input from the third light source to the third optical fiber 105c to the sum frequency of the optical resonance frequency and the mechanical vibration frequency, the vibration 133 can be made into a parametrically amplified vibration 134 as shown in Fig. 6A. In addition, by setting the frequency of the light input from the third light source to the third optical fiber 105c to the difference frequency between the optical resonance frequency and the mechanical vibration frequency, the vibration 133 can be made into a parametrically damped vibration 135 as shown in Fig. 6B.

[0033] [Example 3] Next, a third embodiment will be described with reference to Fig. 7. In the third embodiment, a plurality (N pieces) of opto-mechanical array elements 100-1, 100-2, ..., 100-N (N is a natural number) are used. Each of the opto-mechanical array elements is similar to that in the first embodiment. A first optical fiber 105a is coupled to the bottle-shaped resonating unit 103 on one end side of the opto-mechanical array element 100-1, 100-2, ..., 100-N, and a second optical fiber 105b is coupled to the bottle-shaped resonating unit 103 on the other end side.

[0034] Although not shown, a first light source and a first measuring instrument are connected to the first optical fiber 105a. Also, although not shown, a second light source and a second measuring instrument are connected to the second optical fiber 105b. Using the first optical fiber 105a, excitation of a coupled mechanical vibration mode is performed for each opto-mechanical array element. Also, using the second optical fiber 105b, optical reading is performed.

[0035] Here, the light obtained from the second light source is frequency multiplexed by an acousto-optic modulator (AOM) or the like and input to the second optical fiber 105b. This makes it possible to measure mechanical vibration information for each of the optomechanical array element 100-1, optomechanical array element 100-2, ..., optomechanical array element 100-N independently by optical frequency.

[0036] For example, the coupled mechanical vibration mode of the Mth optomechanical array element appears in the beat signal of the photodetection signal as a sideband that appears around the frequency. When a disturbance occurs in this system, the coupled mechanical vibration mode is modulated according to the position of the disturbed unit structure. By reading this modulation from the spectral change of the sideband mentioned above, it is possible to identify the disturbed optomechanical array element and its position.

[0037] [Example 4] Next, Example 4 will be described with reference to Fig. 8. In Example 4, an optomechanical array element 100 similar to that in Example 1 was fabricated and used. In Example 4, a multiplexer 111 is optically coupled to one end of the optomechanical array element 100, and a splitter 109 is optically coupled to the other end. A reference light optical fiber 110 is connected to the splitter 109 and the multiplexer 111. The splitter 109 and the multiplexer 111 can be configured, for example, from a 50:50 beam splitter.

[0038] In the fourth embodiment, light emitted from the light source 107 is split by the splitter 109 into the optomechanical array element 100 and the reference light optical fiber 110. The split light that is guided (propagated) through the optomechanical array element 100 and the reference light optical fiber 110 is multiplexed by the multiplexer 111 and measured by the measuring instrument 108. In the fourth embodiment, an interferometer is constructed by the optomechanical array element 100 and the reference light optical fiber 110.

[0039] In this interferometer, when tension is applied to the optomechanical array element 100 in the coupling direction, the applied tension causes a change in the refractive index, modulating the input light in the optomechanical array element 100. By causing the modulated light to interfere with the reference light propagating through the reference light optical fiber 110 in the multiplexer 111, it becomes possible to measure the above-mentioned change in tension with the measuring instrument 108.

[0040] [Example 5] Next, a fifth embodiment will be described with reference to FIG. 9. In the fifth embodiment, a hollow optomechanical array element 100a was fabricated using a cylindrical base. For example, a hollow silica capillary can be used as the cylindrical base. The optomechanical array element 100a has a flow path 112 therein. In addition, a first optical fiber 105a is coupled to, for example, a bottle-shaped resonator 103 at one end of the optomechanical array element 100a. An excitation light source is connected to the first optical fiber 105a.

[0041] In the fifth embodiment, for example, water is introduced into the flow path 112. In this state, the first optical fiber 105a is used to excite the mechanical vibration 132 in the coupled mechanical vibration mode to the bottle-shaped resonating unit 103. This causes a flow in the water introduced into the flow path 112. In this way, according to the fifth embodiment, the flow path 112 can transport the fluid.

[0042] As described above, according to the present invention, a plurality of bottle-shaped resonating sections, which serve as whispering gallery mode optical resonators, are connected together by connecting sections, making it possible to provide an optomechanical array element in which a plurality of optomechanical resonator structures are connected in an array.

[0043] It should be noted that the present invention is not limited to the above-described embodiments, and it is apparent that many modifications and combinations can be made by a person having ordinary knowledge in the art within the technical concept of the present invention. [Explanation of symbols]

[0044] 100: Opto-mechanical array element, 101: base, 102: connecting portion, 103: bottle-shaped resonator portion.

Claims

1. The device comprises a rod-shaped base body having a circular outer shape, a plurality of narrow-diameter connecting parts formed by narrowing the diameter at equal intervals, and bottle-shaped resonating parts between adjacent ones of the plurality of connecting parts, The bottle-shaped resonator is an optical resonator in a whispering gallery mode, An optomechanical array element, characterized in that each of the multiple connecting portions is capable of transmitting mechanical vibrations of the adjacent bottle-shaped resonating portion.

2. 2. The optomechanical array element of claim 1, An opto-mechanical array element, wherein the base body has connecting portions made of a bendable material.

3. 3. The optomechanical array element according to claim 1, An opto-mechanical array element, wherein the base body is made of a material whose connecting portion is twistable about an axis.

4. 4. The optomechanical array element according to claim 2 or 3, An optomechanical array element, wherein the matrix is ​​comprised of a fiber made of glass or plastic.

5. The optomechanical array element according to any one of claims 1 to 4, The body is cylindrical in shape.

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