Planar photon resonant motor structure

Abstract

Described herein is a photonic motor comprising: a first optical waveguide arrangement adapted to guide at least one optical mode and form a stator (12); and an electromagnetic interaction device electromagnetically interacting with the optical modality, configured for rotation and forming a rotor (14), the electromagnetic interaction device comprising a plurality of optical resonators or a plurality of reflective metal structures or a combination thereof, the electromagnetic interaction device being concentrically positioned inside the first optical waveguide device, and the first optical waveguide device is separated from the first optical waveguide device by a preset transverse interaction distance, and the preset transverse interaction distance is suitable for establishing coupling of an optical mode and evanescent waves of the plurality of second optical resonators or enabling the evanescent waves of the optical mode to be reflected by the plurality of reflection metal structures. The rotor comprises a circular frame (22) coaxial with the central hub (20) and comprising spokes (R) in an integral arrangement converging towards the central hub, the spokes being adapted to support a region (24) for accommodating a plurality of second optical resonators or for accommodating a plurality of reflective metal structures in a peripheral region of the frame. The frame is separate from the central hub and disposed above the substrate (S), in a non-operational state, the frame can be supported on the substrate by a support structure (26), and in an operational state in which the optical mode is guided in the first optical waveguide arrangement of the stator, the frame can be raised from the substrate.

Description

Planar photonic resonant motor structure Technical Field

[0001] This invention relates to an optomechanical system. Specifically, this invention relates to a mechanical system capable of realizing a photonic motor to extract mechanical energy from a photon source (e.g., a laser source). Specifically, the object of this invention is a photonic motor according to the preamble of claim 1. Background Technology

[0002] International patent application WO 2018 / 087789 discloses a photonic motor suitable for efficiently converting optical power into mechanical torque. This photonic motor includes a device with two sets of guided photonic resonators optically coupled to each other and sharing a common axis of rotation, rotating relative to each other due to an asymmetric optical force induced by resonance. In this motor, the stator plane contains a plurality of optical ring resonators arranged in a circular geometry, which are simultaneously excited by a main ring resonator surrounding them. The rotor plane preferably contains the same number of optical ring resonators arranged in the same manner as in the stator plane. The rotor plane and the stator plane are optically coupled to each other through evanescent coupling between mirrored ring resonators. At a specific input excitation wavelength, the photonic resonant motor rotates and follows the wavelength of the light source, achieved by photomechanical torque generated by the force related to the radiation pressure generated by the coupling of the stator and rotor resonators. The asymmetric optical force associated with the symmetric and antisymmetric resonance modes of the excited ring resonators generates operating torque on the rotor.

[0003] Italian Patent 102021000007118 discloses a photonic resonant motor of the above type in a planar configuration, which includes a first optical waveguide device (e.g., a plurality of first optical resonators) forming the static part or stator of the motor, and a second optical waveguide device (e.g., at least one second optical resonator) forming the movable part or rotor of the motor, which are located in a first spatial region and a second spatial region of a common plane and spaced apart from each other by a predetermined lateral coupling distance, wherein the second optical waveguide device is configured to move relative to the first optical waveguide device in the second region of the plane.

[0004] The lateral coupling distance is adjusted to establish an evanescent wave coupling of optical modes between at least one first optical resonator in the first optical waveguide device and at least one second optical resonator in the second optical waveguide device. When the first and second optical resonators are in a state of proximity to each other, a condition is created such that the second optical resonator is attracted to or repelled from the first optical resonator, thereby causing the second optical resonator to move closer to or further away from the first optical resonator along a predetermined local movement direction.

[0005] More specifically, this photonic motor includes an excitation optical waveguide device and at least one optical radiation input terminal. The excitation optical waveguide device is coupled to the first optical waveguide device at a predetermined optical mode coupling distance relative to at least one first optical resonator, and is configured to receive at least one type of optical radiation having a predetermined wavelength from the optical radiation input terminal and optically couple the received optical radiation to the at least one first optical resonator. The photonic motor also includes a control device preset to control at least one parameter of the radiation from the optical radiation input terminal to selectively establish at least one symmetric and antisymmetric mode.

[0006] Each of the first and second optical resonators is adapted to guide a symmetrical resonant mode at a first predetermined wavelength or an antisymmetric resonant mode at a second predetermined wavelength, depending on the lateral coupling distance and the distance between the first and second optical resonators in the plane. Whenever a symmetrical resonant mode is selectively established, a condition arises such that the second optical resonator is attracted to the first optical resonator, resulting in a movement of the second optical resonator toward the first optical resonator along a predetermined local movement direction in a second spatial region in the plane. Whenever an antisymmetric resonator mode is established, a condition arises such that the second optical resonator is repelled from the first optical resonator, resulting in a movement of the second optical resonator away from the first optical resonator along a predetermined local movement direction in the second spatial region in the plane.

[0007] The control device is also configured to: synchronously control the wavelength of radiation from the optical radiation input terminal so that, whenever the second optical resonator, moving along a predetermined direction in the second spatial region of the common plane, approaches the maximum proximity state or lateral coupling distance state relative to the first optical resonator in the first spatial region of the common plane, it selectively switches from a symmetrical resonance mode to an antisymmetrical resonance mode; or, if a symmetrical resonance mode has been set, synchronously control the opening of the optical radiation input terminal only during the approach step, and turn off the optical radiation input terminal whenever the second optical resonator, moving along a predetermined direction in the second spatial region of the common plane, approaches the maximum proximity state or lateral coupling distance state relative to the first optical resonator in the first spatial region of the common plane, and then, by means of inertial force, cause... The second optical resonator reaches a subsequent evanescent wave coupling state with another different first optical resonator along the predetermined movement direction; or, after the antisymmetric resonance mode has been set, the optical radiation input terminal is synchronously controlled only during the distance step, and the optical radiation input terminal is turned on whenever the second optical resonator moving along the predetermined movement direction in the second spatial region of the common plane is closer to the maximum proximity state or the coupling lateral distance state relative to the first optical resonator in the first spatial region of the common plane; and the second optical resonator is turned off whenever the second optical resonator moving along the predetermined movement direction in the second spatial region of the common plane leaves the coupling state, and then, by means of inertial force, the second optical resonator reaches a subsequent coupling state with another different first optical resonator along the predetermined movement direction.

[0008] The type of photonic motor described in the prior art does not describe a mechanical system solution for supporting and maintaining the rotation of the rotor relative to the stator in a laterally coupled state. Summary of the Invention

[0009] The object of the present invention is to provide a planar photonic motor comprising a structure adapted to maintain the rotation of the rotor relative to the stator by keeping the rotor waveguide and the stator waveguide in a laterally coupled state, thereby maintaining the optomechanical force for allowing the rotor to rotate in a common plane.

[0010] Another object of the present invention is to realize a planar photonic motor with reduced technical complexity in terms of implementation and operation.

[0011] According to the invention, these objectives are achieved by a photonic motor having the features set forth in claim 1.

[0012] Detailed embodiments are described in the dependent claims, which are an integral part of this disclosure.

[0013] Specifically, the present invention relates to a planar photonic motor, comprising: a first optical waveguide device including a first optical ring resonator adapted to guide at least one optical mode and forming a static portion or stator of the motor in a planar region or stator plane; and an electromagnetic interaction device for electromagnetic interaction with at least one of the optical modes, the electromagnetic interaction device being concentrically positioned inside the first optical ring resonator and forming a movable portion or rotor of the motor in a planar region or rotor plane, and the electromagnetic interaction device including a plurality of second optical resonators or a plurality of reflective metal structures or combinations thereof, wherein, when the motor is in an operating state, the stator plane and the rotor plane are coplanar. The static portion and the movable portion of the motor are spaced apart from each other by a predetermined lateral interaction distance, thereby configuring the electromagnetic interaction device for electromagnetic interaction with the optical mode guided by the first optical ring resonator to rotate in the rotor plane relative to the first optical waveguide device in the stator plane.

[0014] The optical mode guided by the first optical waveguide device is provided by at least one excitation optical waveguide coupled to the first optical waveguide device at a predetermined optical mode coupling distance. The at least one excitation optical waveguide is configured to receive at least one optical radiation having a predetermined wavelength from at least one optical radiation input terminal, which is at least one coherent radiation source or coupled to at least one coherent radiation source.

[0015] In the currently preferred embodiment, the first optical ring resonator, the second optical resonator, and the excitation waveguide are implemented by an optical guide integrated on a dielectric substrate, and the excitation waveguide is coplanar with the first optical waveguide device.

[0016] The lateral interaction distance is adjusted to establish evanescent wave coupling of at least one of the optical modes between the first optical resonator and the plurality of second optical resonators, or to cause the evanescent wave of at least one of the optical modes of the first optical resonator to be reflected by the plurality of the reflective metal structures. Evanescent wave optical coupling ensures that a portion of the optical power is transmitted from the stator waveguide to the second optical resonators of the rotor. Conversely, the reflection of the evanescent wave leads to an exchange of momentum, thereby generating radiation pressure that produces torque applied to the rotor.

[0017] To keep the lateral interaction distance stable and enable the rotor to rotate relative to the stator, an innovative configuration of a mechanical rotor system is proposed.

[0018] The rotor is formed from a circular frame in the form of a wheel. This frame includes integrally arranged spokes converging towards a central hub coaxial with the rotor's axis of rotation. These spokes are adapted to support a region on the periphery for accommodating multiple second optical resonators or multiple reflective metal structures. The second optical resonators or reflective metal structures are uniformly distributed along the circumferential periphery of the rotor frame. In this mechanical rotor system, the central hub is separate from the frame, and the frame is positioned above a substrate. The frame can be supported on the substrate by a support structure integrally formed with or connected to the frame, and the support structure protrudes orthogonally relative to the frame in a half-plane facing the substrate and cannot move on the substrate. The height of the support structure is determined such that the rotor frame is held at a predetermined lifting distance from the substrate, slightly below the horizontal level of the stator plane. During operation, when the optical modes are excited and guided in the first optical waveguide device of the stator, an attractive optomechanical force is generated between the rotor and the stator, causing the rotor to be lifted upwards until it is aligned with the stator plane. The lifted rotor advantageously reduces the static friction, dynamic friction and adhesion between the rotor and the substrate, suppressing or significantly reducing the area of ​​the support structure intended for contact with the substrate by suspending the rotor completely or partially.

[0019] The area of ​​the support structure intended for contact with the substrate should be as small as possible in any case to reduce the adhesive and contact forces acting between the support structure and the substrate.

[0020] The center hub is fixed to the base plate located below the wheel, and the center hub is configured to form the joint of the mechanical rotor system and allow the rotor to rotate in the frame plane, while restricting the rotor's rotational degrees of freedom in other spatial directions and preventing the rotor from separating during rotation.

[0021] Advantageously, this mechanical structure prevents the rotor from moving in a plane perpendicular to the plane of rotation, such as the rotor being raised or lowered relative to the plane of rotation and supported on a substrate, thereby optimizing torque and reducing the static friction and adhesion forces acting microscopically between the rotor plane and its corresponding supporting substrate. Attached Figure Description

[0022] Other features and advantages of the invention will be discussed in more detail in the following description of a preferred embodiment provided with reference to the accompanying drawings for illustrative and non-limiting purposes, in which: FIG1a is an exemplary planar photonic resonant motor according to a first embodiment of the invention; FIG1b is an exemplary planar photonic resonant motor according to a second embodiment of the invention; FIG2a and FIG2b are two exemplary cross-sectional views of the planar photonic resonant motor according to the invention in an operational state, taken along IIa-IIa and IIb-IIb, respectively; FIG2c is an exemplary view of the planar photonic resonant motor according to FIG2b in a non-operational state; FIG3a is an enlarged view of a portion of the rotor of the photonic resonant motor according to the invention; and FIG3b is a cross-sectional view of FIG3a taken along line IIIb-IIIb. Detailed Implementation

[0023] Figures 1a and 1b illustrate a photonic resonant motor 10 according to the present invention, which includes a stator 12 and a rotor 14. In the embodiment shown in Figure 1a, the stator 12 is located in the stator plane and includes a closed optical waveguide 16' (such as an optical ring resonator) coupled to an excitation waveguide 18. In the embodiment shown in Figure 1b, the stator 12 is located in the stator plane and includes an open optical waveguide 16' coupled to the excitation waveguide 18, which takes the form of an incomplete optical ring resonator.

[0024] Reference numeral 20 indicates a central hub extending from the base plate S supporting the motor, the hub being coaxial with the rotation axis X of the rotor.

[0025] The rotor 14 includes a circular frame 22 coaxial with the central hub 20, which defines the rotor plane, and includes integrally arranged spokes R converging toward the central hub 20. These spokes are adapted to support a region 24 for accommodating multiple second optical resonators or multiple reflective metal structures or combinations thereof (rotor poles) in the circumferential peripheral region of the frame. The reflective metal structure may be (by way of example) a small, flat metal platform coplanar with the rotor plane.

[0026] Multiple support structures 26 are integral with or connected to the frame and protrude orthogonally relative to the frame in a half-plane facing the substrate S. When the motor is in a non-operating state, the multiple support structures are adapted to hold the rotor frame at a predetermined lifting distance (e.g., 1.95 micrometers) from the substrate S, such that the rotor frame is slightly lower than the horizontal height of the stator plane (e.g., 50 nm lower).

[0027] Due to the tangential optomechanical forces generated between the first optical waveguide device and multiple second optical resonators or reflective metal structures, the frame 22 cannot rotate around the central hub 20.

[0028] The rotor frame 22 is able to rotate around the central hub 20 due to the electromagnetic interaction between the optical modes guided by the optical waveguide 16' or 16" and the multiple second optical resonators or multiple reflective metal structures housed in region 24. This electromagnetic interaction is caused by evanescent wave coupling between the optical modes guided by the optical resonators of the waveguide 16' or 16" and the multiple second optical resonators, or by the reflection of the evanescent waves of the optical modes guided by the optical resonators of the waveguide 16' or 16" by the multiple reflective metal structures.

[0029] Referring to Figures 2a, 2b, and 2c, the central hub 20 is integrally formed with the substrate S, and the central hub includes a first cylindrical portion 20' and a second cylindrical portion 20''. The first cylindrical portion is close to the substrate S and has a cross-section with a first radius, while the second cylindrical portion is away from the substrate S and has a cross-section with a second radius, which is greater than the first radius. The frame 22 is slidably coupled around the central hub 20 at the first cylindrical portion and is spaced a predetermined radial distance from the first cylindrical portion. The second cylindrical portion extends partially above the frame and, in the operating state, is spaced a predetermined buffer distance from the frame to prevent the frame from being lifted upwards beyond a predetermined height above the plane of rotation.

[0030] The radial elongation of the spokes R of the frame is proportional to the working couple generated by the tangential photomechanical force. This working couple must be sufficient to overcome the frictional and adhesive torques generated by the support structure on the substrate, which would impede the rotation of the rotor.

[0031] The support structure 26 is configured to hold the rotor fixed at a predetermined height (e.g., 1.95 micrometers) above the substrate and prevent it from moving on the substrate located below the frame 22. Preferably, the support structure is configured to have the smallest possible contact area with the substrate to reduce the microscopic adhesive forces acting between the frame and the substrate. For example, the support structure includes an axially perforated pin with a surface at its end away from the frame designed for contacting the substrate, the area of ​​which is smaller than the cross-sectional area of ​​the pin. In operation, an optomechanical attraction is generated between the rotor and the stator by stimulating an optical mode guided in the first optical waveguide device of the stator, thereby lifting the rotor (e.g., lifting it by 50 nm) until it is aligned with the stator plane. This process operates as a mechanism for reducing static friction, dynamic friction, and adhesive forces by suppressing or significantly reducing the contact area between the support structure 26 and the substrate S by suspending the rotor completely or partially.

[0032] Preferably, the support structure 26 is arranged at the shortest possible radial distance from the rotation axis of the frame, that is, the support structure is arranged as close as possible to the rotation axis of the rotor to increase the working torque generated by the tangential optomechanical force that counteracts the frictional torque, which depends on static friction and adhesion and hinders rotation.

[0033] Finally, Figure 3a shows in detail the current preferred embodiment of the region 24 for accommodating a plurality of second optical resonators.

[0034] This region includes a groove 30 obtained by micromachining (etching) the frame 22 of the silicon rotor, and a ring-shaped optical waveguide 32 is formed therein using a similar technique to create a second optical resonator. The figure also partially shows a portion of the rotor 12 and its corresponding waveguide 16' near the outer portion of the groove 30 and waveguide 32.

[0035] These manufacturing techniques are typical of microelectromechanical devices (MEMS) and are therefore commonly used in the fabrication of integrated electronic devices (e.g., etching, deposition). In one configuration of the structure, the wafer used is of the SOI (silicon-on-insulator) type, the rotor and stator are implemented on the same silicon layer as the wafer itself and separated from each other by using appropriate etching techniques, while the support structure 26 and hub 20 are obtained by depositing their respective materials and subsequently separated from the substrate by a subsequent etching technique.

[0036] Advantageously, the photonic motor described above can be used in applications where the rotor's magnetic poles acquire dipole moments under the action of photomechanical gradient forces through interaction with the stator, and the fact that the interference generated by the photomechanical forces forms a non-equilibrium system following Rayleigh-Jeans heating causes the rotor to stabilize at a higher energy state rather than at the lowest possible energy state.

[0037] In alternative applications, the rotor's magnetic poles interact with the stator to behave like a localized many-body system capable of generating condensed matter phases, which can be used to realize many-body physics-based sensors and actuators, as well as photonic resonant motors of the photothermal type.

[0038] In another application, the rotor's magnetic poles act as a localized many-body system capable of generating optomechanical waves by interacting with the stator. These optomechanical waves interact with other similar devices on a large scale, thereby allowing the phenomenon to be amplified on a large scale.

[0039] In another application, the rotor's magnetic poles interact with the stator, causing a dynamic change in the stator's refractive index. This allows the stator to function as a time-photonic crystal under ambient temperature and non-vacuum conditions, enabling applications in sensing, actuation, and quantum computing.

[0040] Finally, the rotor's magnetic poles dynamically change the stator's refractive index over time by interacting with the stator, thus generating the dynamic Casimir effect, which has applications including the development of novel light sources and propulsion systems on a macroscopic scale.

[0041] It goes without saying that changes can be made to the embodiments described above for illustrative purposes only and not for limiting purposes without prejudice to the principles of the invention, and without departing from the scope of protection defined by the appended claims.

Claims

1. A photonic motor (10), comprising: - At least one optical radiation input terminal; - A first optical waveguide device adapted to guide at least one optical mode, the first optical waveguide device including a ring-shaped first optical resonator (16'; 16"), the ring-shaped first optical resonator forming a static portion of the motor (10) in a stator plane, the static portion being a stator (12); - At least one excitation optical waveguide (18) coupled to the first optical waveguide device at a predetermined optical mode coupling distance, and at least one of the excitation optical waveguides being configured to receive at least one optical radiation having a predetermined wavelength from at least one of the optical radiation input terminals and optically couple the received optical radiation to the first optical waveguide device; - An electromagnetic interaction device, which performs electromagnetic interaction with at least one of the optical modes, the electromagnetic interaction device comprising a plurality of second optical resonators (32) or a plurality of reflective metal structures or a combination thereof, the electromagnetic interaction device being concentrically positioned inside the first optical waveguide device and spaced apart from the first optical waveguide device by a predetermined lateral interaction distance, the predetermined lateral interaction distance being suitable for the first optical resonator (16'). 16” establishes at least one evanescent wave coupling of the optical mode between the first optical resonator (16'; 16") and a plurality of second optical resonators (32), or is adapted to cause the evanescent wave of at least one optical mode of the first optical resonator (16'; 16") to be reflected by a plurality of the reflective metal structures; the electromagnetic interaction device is configured to rotate relative to the first optical waveguide device about a rotation axis (X) in at least one predetermined rotation direction, thereby forming a movable part of the motor (10) in the rotor plane, the movable part being the rotor (14); a central hub (20) extending from the substrate (S), the central hub being coaxial with the rotation axis (X) of the rotor (14); wherein the rotor (14) includes: a circular frame (22), the circular frame being coaxial with the central hub (20) and including spokes (R) arranged integrally toward the central hub (20), the spokes being adapted to accommodate a plurality of the The second optical resonator (32) or the region (24) for accommodating the plurality of the reflective metal structures is supported in the circumferential peripheral region of the frame (22); a plurality of support structures (26) are integrally formed with the frame (22) and protrude orthogonally to the frame, wherein the frame (22) is separated from the central hub (20) and disposed above the substrate (S), in a non-operating state, the frame can be supported on the substrate by the support structures (26), and in an operating state in which the optical mode is excited and guided in the first optical waveguide device of the stator (12), the frame can be lifted from the substrate, the height of the plurality of support structures (26) such that in the non-operating state, the frame (22) is held at a predetermined lifting distance from the substrate (S), thereby placing the rotor plane below and close to the stator plane.

2. The photonic motor (10) according to claim 1, wherein, The central hub (20) is integrally formed with the substrate (S) and includes a first cylindrical portion (20') and a second cylindrical portion (20'). The first cylindrical portion is close to the substrate (S) and has a first radius in its cross section. The second cylindrical portion is far from the substrate (S) and has a second radius in its cross section. The second radius is greater than the first radius. The circular frame (22) is slidably coupled around the central hub (20) at the first cylindrical portion (20') and is a predetermined radial distance away from the central hub. The second cylindrical portion (20') extends partially above the frame (22) to prevent the frame (22) from being lifted above a predetermined height above the plane of rotation.

3. The photonic motor (10) according to any one of the preceding claims, wherein, The support structure (26) includes an axially perforated pin having a surface at one end away from the frame (22) intended for contact with the substrate (S), the area of ​​which is smaller than the cross-sectional area of ​​the pin.

4. The photonic motor (10) according to any one of the preceding claims, wherein, The support structure (26) is arranged at the shortest possible radial distance from the axis of rotation (X) of the frame (22) of the rotor (14).

5. The photonic motor (10) according to any one of the preceding claims, wherein, The first waveguide device includes a closed-loop optical resonator (16').

6. The photonic motor (10) according to any one of claims 1 to 4, wherein, The first waveguide device includes an open-loop optical resonator (16”).

7. The photonic motor (10) according to any one of the preceding claims, wherein, The second optical resonator (32) or the reflective metal structure is uniformly distributed along the circumferential peripheral region of the frame (22) of the rotor (14).

8. The photonic motor (10) according to any one of the preceding claims, wherein, The excitation optical waveguide (18) is coplanar with the first optical waveguide device.

9. The photonic motor (10) according to any one of the preceding claims, wherein, The optical radiation input terminal is at least one coherent radiation source, or the optical radiation input terminal is coupled to at least one coherent radiation source.

10. The photonic motor (10) according to any one of the preceding claims, wherein, The first optical resonator (16'; 16"), the second optical resonator (32) and the excitation optical waveguide device (18) are formed by an optical guide integrated on a dielectric substrate.

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