A dual-drive circular fast-axis tunable electro-optic modulator support device

Abstract

The application belongs to the technical field of supporting devices, and particularly relates to a double-driving circular fast-axis adjustable electro-optic modulator supporting device. The fixed base is provided with a first threaded hole and a second threaded hole. The first fastener is matched with the second threaded hole, and the second fastener is matched with the first threaded hole. The outer shell is fixedly connected with the fixed base through the first fastener and the second fastener. The electro-optic modulator is placed between the outer shell and the fixed base. The optical feedback system of the application can be used for real-time accurate phase delay labeling of the electro-optic modulator, because the obtained detection signal is the same as the detection signal during measurement. The application ensures uniform damping of the whole vibration plane of the circular electro-optic crystal, so that the vibration deformation of the circular electro-optic crystal will not suddenly decrease or increase due to the increase or decrease of the damping in a certain direction. The application reduces the damping of the vibration plane of the electro-optic modulator and keeps the damping uniform, which is beneficial to the change of the fast-axis azimuth of the pure traveling wave mode.

Description

Technical Field

[0001] This invention belongs to the field of support device technology, specifically relating to a dual-drive circular fast-axis adjustable elastic modulator support device. Background Technology

[0002] An optical-elastic modulator (PEM) is a resonant polarization modulation device that operates at the resonant frequency of its optical elements. A PEM consists of an anisotropic piezoelectric crystal and isotropic optical materials. The characteristics of operating in a resonant state and using isotropic optical materials endow PEMs with unique properties, such as high modulation frequency, large aperture, high modulation efficiency, and good modulation stability, making them highly efficient polarization modulation devices. Common one-dimensional and two-dimensional PEMs can only adjust their modulation axis mechanically, limiting their application in measurement fields. In recent years, the fast-axis adjustable optical-elastic modulator (FaaPEM) has been proposed. This new type of PEM allows for flexible adjustment of the fast axis and phase delay by controlling the applied excitation voltage. FaaPEMs have both pure standing wave and pure traveling wave modes. In its pure traveling wave mode, the fast axis can perform circular motion at a specific frequency, and the vibration direction of the optical-elastic crystal changes constantly. Common support devices use soft foam to wrap around the elastic crystal and fix it to the support. This type of support device cannot guarantee uniform damping throughout the entire vibration plane, which is not conducive to the change of the fast axis in the pure traveling wave mode. There is a certain error between the detection signal obtained by the optical feedback system and the detection signal during use. Summary of the Invention

[0003] To address the technical problems of traditional support devices failing to guarantee uniform damping across the entire vibration plane, which is detrimental to the constant changes of the fast axis in pure traveling wave mode, and the existence of certain errors between the detection signal obtained by the optical feedback system and the detection signal during use, this invention provides a dual-drive circular fast-axis adjustable elastic modulator support device with uniform vibration plane damping, small error between the optical feedback signal and the detection signal, and high efficiency.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] A dual-drive circular fast-axis adjustable elastic modulator support device includes a housing, a fixed base, a first fastener, and a second fastener. The fixed base is disposed at the bottom of the housing and has a first threaded hole and a second threaded hole. The first fastener engages with the second threaded hole, and the second fastener engages with the first threaded hole. The housing and the fixed base are fixedly connected by the first fastener and the second fastener. An elastic modulator is placed between the housing and the fixed base.

[0006] The photoelastic modulator includes a circular photoelastic crystal and a piezoelectric actuator. Two piezoelectric actuators are provided, and the two piezoelectric actuators are coupled to the circular photoelastic crystal.

[0007] Both the outer shell and the fixed base are provided with light-transmitting hole protrusions. The two light-transmitting hole protrusions are located at the corresponding positions of the circular elastic crystal, and the two light-transmitting hole protrusions are fixed perpendicular to the vibration plane of the circular elastic crystal.

[0008] Both of the two light-transmitting protrusions are provided with light-transmitting holes, which are located at the center of the circular elastic crystal.

[0009] Both the outer casing and the fixed base are provided with heat dissipation holes.

[0010] The first fastener passes through the second threaded hole and is secured at the center of the piezoelectric actuator, while the second fastener passes through the first threaded hole and is fixedly connected to the housing.

[0011] An optical feedback system is provided in the optical path direction of the elastic-optical modulator. The optical feedback system includes a first laser, a first polarizer, a first analyzer, and a photodetector. The first polarizer, the elastic-optical modulator, the first analyzer, and the photodetector are arranged sequentially in the optical path direction of the first laser.

[0012] The optical feedback system further includes a second laser, a second polarizer, a second analyzer, and a photodetector. The second laser has the second polarizer, a light-sensitive modulator, a second analyzer, and a photodetector arranged sequentially along its optical path.

[0013] A method for calculating the optical path difference of a dual-drive circular fast-axis adjustable elastic modulator support device includes the following steps:

[0014] S1. Under the action of AC high voltage of the same frequency and arbitrary phase, the piezoelectric actuator of the elastic-optic modulator causes strain in the circular elastic-optic crystal. The stress distribution inside the circular elastic-optic crystal is as follows:

[0015]

[0016] In equation (a), T A T B These are the stress amplitudes between the two piezoelectric actuators and the circular photoelastic crystal, respectively, and the stress amplitudes are proportional to the driving voltage; ω = 2πf, where f is the driving voltage frequency; θ is the spatial position in polar coordinates, cos2θ = ±1 is the modulation axis position of the circular photoelastic crystal, and the position where cos2θ = 1 is the fast axis azimuth angle of the circular photoelastic crystal, denoted as θ0; This represents the initial position of one piezoelectric actuator relative to another; is the delay difference in stress generation between the two piezoelectric actuators on the circular photoelastomer crystal; This represents the phase difference of the driving voltages on the two piezoelectric actuators.

[0017] S2. Rewrite equation (a) using trigonometric formulas as follows:

[0018] T=T1cos(ωt-2θ+γ1)+T2cos(ωt+2θ+γ2) (b)

[0019] In equation (b), the stress amplitude term is expressed as:

[0020] The phase term is represented as

[0021] S3, when or And T A =T B When the elastic modulator operates in pure traveling wave mode, equation (b) can be rewritten as:

[0022] T = 2T A cos(ωt±2θ) (c)

[0023] In equation (c), the - represents At this time, the stress traveling wave in the circular elastocrystalline crystal propagates in a counterclockwise direction; the + indicates At this point, the stress traveling wave in the circular photoelastic crystal propagates clockwise; therefore, in pure traveling wave mode, the azimuth angle of the fast axis of the photoelastic modulator is... The fast axis of the photoelastic modulator undergoes circular motion at a frequency of f / 2, with a constant phase delay.

[0024] S4. Let the thickness direction of the circular elastic-optical crystal be the z-direction, and the incident light be along the x-direction. Let o be the origin of the coordinate system, which is the center of the circular elastic-optical crystal. Establish a rectangular coordinate system in xyz space according to the right-hand rule. At y = 0, the angle between the incident light direction and the z-axis is θ0, and the refraction angle is θ1. Assuming the incident light is an ideal light source and the crystal thickness is d, according to elasticity, the stress of the circular elastic-optical crystal at y = 0 as x changes satisfies:

[0025]

[0026] Where l is the diameter of the elastocrystalline crystal, and δ0 is the stress amplitude of the circular elastocrystalline crystal; at y = 0, the difference in refractive index between the two incident rays is:

[0027]

[0028] σ is the stress-elastic coefficient;

[0029] S5. If the incident light is incident perpendicularly at (0,0), it is decomposed into ordinary light (o) and extraordinary light (e) by the optical modulator. The optical path difference between the ordinary light (o) and the extraordinary light (e) is:

[0030] L=dδ0σ (f)

[0031] When the light is incident at an oblique angle, due to the symmetry of the optical modulator, the x-axis is shifted to the center of the circular optical modulator crystal. The incident light is then decomposed by the optical modulator into ordinary (o) light and extraordinary (e) light. The optical path difference between the ordinary (o) light and the extraordinary (e) light is:

[0032]

[0033] Right now in,

[0034] According to Snell's law, then

[0035] n0sinθ0=n1sinθ1 (h)

[0036] n0 is the refractive index of air, and n1 is the refractive index of the circular elastocrystalline crystal at the incident point.

[0037] Compared with the prior art, the beneficial effects of this invention are:

[0038] This invention fully utilizes the aperture of the photoelastic crystal and provides excellent heat dissipation through heat dissipation holes. During the operation of the photoelastic modulator, this invention leverages the two-dimensional vibration characteristics of the circular photoelastic crystal and the fact that the displacement at the center of the crystal is minimal during vibration. A protrusion extends the aperture, perpendicular to the vibration plane of the circular photoelastic crystal, and serves as a primary support point. This ensures uniform damping across the entire vibration plane, preventing sudden changes in deformation due to increased or decreased damping in a particular direction. This invention reduces and maintains uniform damping on the vibration plane of the photoelastic modulator, which is beneficial for the temporal variation of the fast axis azimuth in pure traveling wave mode. The optical feedback system of this invention provides the same detection signal as the measurement signal, which can be used for real-time and precise calibration of the phase delay of the photoelastic modulator. Attached Figure Description

[0039] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0040] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0041] Figure 1 This is a schematic diagram of the structure of the present invention;

[0042] Figure 2 This is a front view of the present invention;

[0043] Figure 3 This is a cross-sectional view of the present invention;

[0044] Figure 4 This is a schematic diagram of the optical feedback system of the present invention;

[0045] Figure 5 This is a schematic diagram of the optical path of the optical feedback system of the present invention.

[0046] Wherein: 1 is the outer shell, 2 is the fixed base, 3 is the light modulator, 4 is the light-transmitting hole, 5 is the first fastener, 6 is the second fastener, 7 is the heat dissipation hole, 8-1 is the first threaded hole, 8-2 is the second threaded hole, 9 is the light-transmitting hole boss, 3-1 is the circular light-transmitting crystal, 3-2 is the piezoelectric actuator, 1-1 is the first laser, 2-1 is the first polarizer, 4-1 is the first analyzer, 5-1 is the photodetector, 1-2 is the second laser, 2-2 is the second polarizer, 4-2 is the second analyzer, and 5-2 is the photodetector. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. These descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the claims of the present invention. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0048] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0049] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0050] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0051] like Figure 1-3 As shown, in this embodiment, the elastic modulator 3 is placed in the cavity formed between the outer shell 1 and the fixed base 2. The first fastener 5 and the second fastener 6 are used to fasten the outer shell 1 and the fixed base 2. The heat dissipation holes of the outer shell 1 and the fixed base 2 have a good heat dissipation effect. When the elastic modulator 3 is working, taking advantage of the two-dimensional vibration characteristics of the circular elastic crystal 3-1 and the characteristic that the displacement at the center of the circular elastic crystal 3-1 is minimal when it vibrates, the light-transmitting hole 4 is extended to form a light-transmitting hole protrusion 9. The light-transmitting hole protrusion 9 is perpendicular to the vibration plane of the circular elastic crystal 3-1 and serves as the main support point, ensuring that the damping of the entire vibration plane of the circular elastic crystal is uniform. This prevents the deformation of the circular elastic crystal 3-1 from suddenly decreasing or increasing due to the damping increasing or decreasing in a certain direction. This reduces the damping of the vibration plane of the elastic modulator 3 and keeps the damping uniform, which is beneficial for the change of the fast axis orientation in the pure traveling wave mode.

[0052] In this embodiment, the first fastener 5 serves as an auxiliary support point. In order to reduce the influence of gravity on the piezoelectric actuator 3-2 (which is generally negligible in actual operation) and to reflect whether the support of the photoelectric modulator 3 is balanced, a small first fastener 5 is used to support the piezoelectric actuator 3-2 at the vibration node position of the photoelectric modulator 3. The first fastener 5 needs to meet two requirements: first, the fastener must be fixed at the center of the piezoelectric actuator 3-2; second, in order to reduce the influence on the vibration of the piezoelectric actuator 3-2, the contact area between the first fastener 5 and the piezoelectric actuator 3-2 should be as small as possible and should not cause damage to the piezoelectric actuator 3-2 due to tightening.

[0053] like Figure 4 As shown, the optical feedback system in this embodiment can track the reduction in optical path difference caused by the frequency shift of the photoelastic modulator 3 in real time. When polarized light is incident perpendicularly to the center of the photoelastic crystal, the optical path is small at perpendicular incidence, but the optical path difference is largest at the center of the circular photoelastic crystal 3-1 due to the maximum stress. When polarized light is incident obliquely, the optical path increases, and the refractive index difference between the o-ray and e-ray first increases and then decreases with x. The increase and decrease are symmetrical, so the optical path difference of oblique incidence is equal to that of perpendicular incidence. By changing the amplitude of the driving voltage to keep its phase delay constant, the optical path difference remains unchanged, which is beneficial for real-time and accurate calibration of the phase delay of the photoelastic modulator 3 when using it for measurement.

[0054] In this embodiment, the optical path difference between the incident light, which is decomposed into ordinary light (o-ray) and extraordinary light (e-ray) by the optical modulator, is calculated as follows:

[0055] Under the action of AC high voltage of the same frequency and arbitrary phase, the piezoelectric actuator 3-2 of the piezoelectric modulator 3 causes strain in the circular piezoelectric crystal 3-1. The stress distribution inside the circular piezoelectric crystal 3-1 is as follows:

[0056]

[0057] In equation (a), T A T B The stress amplitudes of the two piezoelectric actuators and the circular photoelectroluminescent crystal are respectively, and the stress amplitude is proportional to the driving voltage; ω=2πf, where f is the 3-1 resonant frequency of the circular photoelectroluminescent crystal; θ is the spatial position in polar coordinates, where cos2θ=±1 is the position of the modulation axis, and the position where cos2θ=1 is the azimuth angle of the fast axis, denoted as θ0; This indicates the initial position of one piezoelectric actuator 3-2 relative to the other piezoelectric actuator 3-2; α BA =α B -α A The delay difference in stress generated by the two piezoelectric actuators 3-2 on the circular elasto-optic crystal 3-1; This represents the phase difference of the driving voltages on the two piezoelectric actuators 3-2.

[0058] Using trigonometric formulas, equation (a) can be rewritten as:

[0059] T=T1cos(ωt-2θ+γ1)+T2cos(ωt+2θ+γ2) (b)

[0060] In equation (b), the stress amplitude term can be expressed as: The phase term can be expressed as

[0061] when or And T A =T B When the elastic modulator 3 operates in pure traveling wave mode, equation (b) can be rewritten as:

[0062] T = 2T A cos(ωt±2θ) (c)

[0063] In formula (d), "-" indicates At this point, the stress traveling wave in the circular elasto-optic crystal 3-1 propagates in a counterclockwise direction; "+" indicates... At this point, the stress traveling wave in the circular elasto-optic crystal 3-1 propagates counterclockwise. Therefore, in pure traveling wave mode, the azimuth angle of the fast axis of FaaPEM is... The fast axis of the photoelectric modulator 3 performs circular motion at a frequency of f / 2, and the phase delay is constant.

[0064] like Figure 5 As shown, the thickness direction of the circular elastic-optical crystal 3-1 is the z-direction, the incident light is along the x-direction, and the y-direction is perpendicular to the paper and outwards. O is the origin (center of the circle). The interface shown is located at y = 0. The angle between the incident light direction and the z-axis is θ0, and the angle of refraction is θ1. Assume the incident light is an ideal light source and the crystal thickness is d. According to elasticity, the stress of the circular elastic-optical crystal 3-1 at y = 0 as x changes satisfies:

[0065]

[0066] Where l is the diameter of the circular elasto-optic crystal 3-1, and δ0 is the stress amplitude of the circular elasto-optic crystal 3-1, which is proportional to the input voltage amplitude. At y = 0, the difference in refractive index between the o-ray and the e-ray is:

[0067]

[0068] Where σ is the stress-optical coefficient.

[0069] If the light is incident perpendicularly at (0,0), the optical path difference between the o-ray and e-ray is:

[0070] L=dδ0σ (f)

[0071] If the incident light is oblique, such as Figure 5 As shown, based on the symmetry of the photoelastic modulator 3, shifting the x-axis to the center position x1 of the circular photoelastic crystal 3-1, the optical path difference between its o-ray and e-ray is:

[0072]

[0073] Right now in,

[0074] According to Snell's law, then

[0075] n0sinθ0=n1sinθ1 (h)

[0076] Where n0 is the refractive index of air and n1 is the refractive index at point x of the circular elasto-optic crystal 3-1.

[0077] When the optical-elastic modulator 3 operates in traveling wave mode, under steady-state conditions, if the amplitude, frequency, and phase of the driving voltage remain unchanged, the fast axis undergoes circular motion at a frequency of f / 2, and the vibration direction of the circular optical-elastic crystal 3-1 changes constantly. Ensuring uniform damping across the entire vibration plane of the circular optical-elastic crystal 3-1 prevents sudden decreases (or increases) in deformation due to increased (or decreased) damping in a certain direction. The support device reduces the damping of the vibration plane of the optical-elastic modulator 3 and maintains uniform damping, which is beneficial for the constant change of the fast axis orientation in pure traveling wave mode. The optical feedback system provides the same detection signal as the measurement signal, which can be used to accurately calibrate the phase delay of the optical-elastic modulator 3 in real time.

[0078] The above description only illustrates the preferred embodiments of the present invention. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention, and all such changes should be included within the protection scope of the present invention.

Claims

1. A dual-drive circular fast-axis adjustable elastic modulator support device, characterized in that: The device includes a housing (1), a fixed base (2), a first fastener (5), and a second fastener (6). The fixed base (2) is located at the bottom of the housing (1) and has a first threaded hole (8-1) and a second threaded hole (8-2). The first fastener (5) engages with the second threaded hole (8-2), and the second fastener (6) engages with the first threaded hole (8-1). The housing (1) and the fixed base (2) are fixedly connected by the first fastener (5) and the second fastener (6). An elastic-optic modulator (3) is placed between them; the elastic-optic modulator (3) includes a circular elastic-optic crystal (3-1) and a piezoelectric actuator (3-2), and two piezoelectric actuators (3-2) are provided, with the two piezoelectric actuators (3-2) coupled to the circular elastic-optic crystal (3-1); both the outer shell (1) and the fixed base (2) are provided with light-transmitting hole protrusions (9), and the two light-transmitting hole protrusions (9) are both located at corresponding positions on the circular elastic-optic crystal (3-1), and the two light-transmitting hole protrusions (9) are fixed perpendicular to the vibration plane of the circular elastic-optic crystal (3-1); the two Each light-transmitting boss (9) is provided with a light-transmitting hole (4), and the light-transmitting hole (4) is located at the center of the circular elastic crystal (3-1); the first fastener (5) passes through the second threaded hole (8-2) and is fixed at the center of the piezoelectric actuator (3-2), and the second fastener (6) passes through the first threaded hole (8-1) and is fixedly connected to the outer shell (1); an optical feedback system is provided in the optical path direction of the elastic modulator (3), and the optical feedback system includes a first laser (1-1), a first polarizer (2-1), a first analyzer (4-1), and a photoelectric sensor. The detector (5-1) includes a first polarizer (2-1), a light-sensitive modulator (3), a first analyzer (4-1), and a photodetector (5-1) arranged sequentially along the optical path of the first laser (1-1); the optical feedback system also includes a second laser (1-2), a second polarizer (2-2), a second analyzer (4-2), and a photodetector (5-2), with the second polarizer (2-2), a light-sensitive modulator (3), a second analyzer (4-2), and a photodetector (5-2) arranged sequentially along the optical path of the second laser (1-2). A method for calculating the optical path difference of a dual-drive circular fast-axis adjustable elastic modulator support device, characterized by comprising the following steps: S1. Under the action of AC high voltage of the same frequency and arbitrary phase, the piezoelectric actuator of the elastic-optic modulator causes strain in the circular elastic-optic crystal. The stress distribution inside the circular elastic-optic crystal is as follows: （a） In formula (a), , These represent the stress amplitudes between the two piezoelectric actuators and the circular photoelastic crystal, respectively, and the stress amplitudes are proportional to the driving voltage; ,in The driving voltage frequency; The spatial position in polar coordinates. The modulation axis position of the circular elasto-optic crystal. The position is the fast axis azimuth angle of the circular elasto-optic crystal, denoted as . The This represents the initial position of one piezoelectric actuator relative to another; is the delay difference in stress generation between the two piezoelectric actuators on the circular photoelastomer crystal; This represents the phase difference of the driving voltages on the two piezoelectric actuators. S2. Rewrite equation (a) using trigonometric formulas as follows: （b） In equation (b), the stress amplitude term is expressed as: , ; The phase term is represented as , ; S3, when ,and When the elastic modulator operates in pure traveling wave mode, equation (b) can be rewritten as: （c） In equation (c), the - represents At this time, the stress traveling wave in the circular elastocrystalline crystal propagates in a counterclockwise direction; the + indicates At this point, the stress traveling wave in the circular photoelastic crystal propagates clockwise; therefore, in pure traveling wave mode, the azimuth angle of the fast axis of the photoelastic modulator is... The fast axis of the elastic modulator operates at a frequency of . The circular motion has a constant phase delay; S4. Let the thickness direction of the circular elastic crystal be... Direction, incident line direction, Using the origin as the center of a circular elastocrystalline crystal, a rectangular coordinate system in xyz space is established according to the right-hand rule; At that point, the direction of light incidence is... The included angle of the axis is The angle of refraction is Assuming the incident light is an ideal light source and the crystal thickness is... According to the principles of elasticity, a circular elastic-optical crystal... With The changing stress satisfies: （d） The The diameter of the elastocrystalline crystal is [missing information]. The stress amplitude of a circular elastocrystalline crystal; in At this point, the difference in refractive index between the two incident rays is: （e） The The stress-elastic coefficient; S5. If the incident light is incident perpendicularly at (0,0), it is decomposed into ordinary light (o) and extraordinary light (e) by an optical modulator. The optical path difference between the ordinary light (o) and the extraordinary light (e) is: （f） When the light is incident at an oblique angle, due to the symmetry of the optical modulator, the x-axis is shifted to the center of the circular optical modulator crystal. The incident light is then decomposed by the optical modulator into ordinary (o) light and extraordinary (e) light. The optical path difference between the ordinary (o) light and the extraordinary (e) light is: （g） Right now ,in, ; According to Snell's law, then （h） The The refractive index of air, the denoted as the refractive index of the circular elastocrystalline crystal at the point of incidence.

2. The dual-drive circular fast-axis adjustable elastic modulator support device according to claim 1, characterized in that: Both the outer shell (1) and the fixed base (2) are provided with heat dissipation holes (7).

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