Broadband dynamic polarization regulation and control device and method based on interference principle

Abstract

The invention discloses a broadband dynamic polarization regulation and control device and method based on an interference principle. According to the method, laser can be controlled to be emitted in any polarization state. In the control process, the polarization form of emergent light is controlled by moving the optical platform to adjust the distance between the two groups of light splitting prisms and the reflector, and the polarization size of the emergent light is controlled by adjusting the modulation depth of the light modulator. Due to the fact that the birefringence principle is not adopted, laser can be output in any polarization state, and the method has the advantages of being wide in frequency band and easy to adjust and can be applied to the fields of material detection, optical storage and the like.

Description

Technical Field

[0001] The present invention belongs to the field related to optical control, and specifically relates to a wide-band dynamic polarization control device and method based on the interference principle. By adjusting the optical path difference and amplitude, arbitrary control of the polarization state of the output light can be achieved, and it is suitable for scenarios requiring high-precision dynamic adjustment of the polarization state. Background Art

[0002] Polarization control technology is widely used in fields such as fiber-optic communications, optical imaging, laser processing, biomedicine, and materials testing. For example, linearly polarized light in fiber-optic communications can improve the speed and stability of signal transmission and enhance the confidentiality of communication systems. Circularly polarized light is used in biomedicine to study the structure and function of biomolecules by exploiting their absorption and scattering properties. Elliptically polarized light is used in materials testing to analyze the changes in the parameters of the material when it is illuminated, providing information such as the material's refractive index, thickness, and surface roughness.

[0003] The current mainstream polarization control devices include wave plate polarization controllers, fiber ring polarization controllers, electro-optic polarization controllers, pressure polarization controllers, etc., which are based on the different propagation speeds of light in different polarization directions to achieve the change of polarization state, and control the polarization state of light by controlling the distance of light propagation. These methods have strict requirements on the wavelength and polarization state of the input light. For example, the wave plate polarization controller (see Application optics, 1979, 18: 1288-1291) includes λ / 4 and λ / 2 wave plates in the device. When the wavelength of the input light changes, the change of the polarization state by the wave plate will change accordingly. The fiber ring polarization controller (see Journal of Lightwave Technology, 1987, Lt-5 (7): 980-984) is similar to the wave plate polarization controller in principle. It uses the different refractive indexes of light in two perpendicular directions in the optical fiber to make the propagation speed of light in the two directions different, so that by changing the propagation distance of light in the optical fiber, the state of the output polarization light can be changed. This modulation method also has high requirements on wavelength. At the same time, these methods can only change the phase difference between the two perpendicular light components, but cannot change the amplitude of their components. The control over the state of the output polarized light is not complete, and it is impossible to achieve polarized light output with arbitrary amplitude, arbitrary polarization direction, and arbitrary polarization state. Summary of the Invention

[0004] In response to the shortcomings of the aforementioned prior art, the present invention aims to provide a novel method for controlling the polarization state of light. By adjusting the distance between the reflector assembly and the beam splitter prism, the phase change of one of the light beams can be controlled. By controlling the optical modulator, the amplitude of the light can be controlled. By controlling the phase and amplitude of the two split light beams, the polarization state of the outgoing light can be controlled. Using this method, light can be output in any polarization state by varying the distance between the beam splitter prism and the reflector assembly and the depth of the optical modulator, thus satisfying adjustments in various situations. This method offers advantages such as a wide frequency band and high output controllability.

[0005] The technical solutions of the present invention are as follows:

[0006] On the one hand, the present invention provides a wide-band dynamic polarization control device based on the interference principle, which is characterized in that it comprises: a first polarization beam splitter prism (1), a second polarization beam splitter prism (3), a first reflector (4), a second reflector (6), an S-light modulator (2), and a P-light modulator (5); incident light is split into S-light and P-light by the first polarization beam splitter prism (1), and the P-light passes through the P-light modulator (2) in turn and enters the second polarization beam splitter prism (3); the S-light passes through the first reflector (4), the S-light modulator (5), and the second reflector (6) in turn and enters the second polarization beam splitter prism (3) to be combined with the P-light for output;

[0007] By adjusting the modulation parameters of the s-light modulator (2) and the p-light modulator (5), the amplitudes of the p-light and the s-light are independently controlled;

[0008] By moving an optical platform (7) integrating the first reflector (4) and the second reflector (6), a distance l between the first reflector (4) and the first polarization beam splitting prism (1) is adjusted to change the optical path difference of the S light, thereby controlling the phase difference between the S light and the P light.

[0009] Furthermore, a measuring element is included for respectively measuring the optical power of the p-light or the s-light when the s-light or the p-light is blocked, so as to assist in adjusting the s-light optical modulator (2) and the p-light optical modulator (5) and set the amplitude of the s-light and the p-light in the output light.

[0010] Second, the present invention also provides a method for controlling the polarization state of light based on the interference principle, comprising the following steps:

[0011] Step S1: Build a beam splitting and combining device to control the polarization state of the incident light, including two polarization beam splitters, two reflectors, and optical modulators that control the amplitude of the two beams. The reflectors and their corresponding optical modulators can be integrated onto an optical platform that can be moved by a motor to adjust the distance between the reflectors and the polarization beam splitters.

[0012] Step S2: According to the requirements of the incident light and the desired output light, the modulation result of the optical modulator is adjusted to control the amplitudes of the p-light component and the s-light component in the output polarized light.

[0013] Step S3: According to the requirements of the incident light and the desired output light, the distance between the reflector group and the polarization beam splitter prism is changed to obtain output light with different polarization characteristics. The specific control method is as follows:

[0014] Assume that the wave function of the incident light is in is the phase difference between s-light and p-light, A s and A p are the amplitudes of s-light and p-light respectively.

[0015] The incident light is split into s-light and p-light after passing through the polarization beam splitter prism. The p-light passes through the light modulator and reaches the combined polarization beam splitter prism, while the s-light passes through the reflector group and the light modulator and then reaches the combined polarization beam splitter prism. The distance between the reflector group and the polarization beam splitter prism is l, so the s-light has an additional optical path difference of 2l, and the corresponding phase difference is The wave function of the output polarized light is The corresponding ellipse equation is:

[0016]

[0017] According to the ellipse equation, we can deduce:

[0018] when When , the equation of the ellipse becomes The corresponding polarized light is linearly polarized light;

[0019] when When , the equation of the ellipse is Corresponding to the standard ellipse equation, on this basis, adjust A s =A p , the equation becomes Corresponding to circularly polarized light;

[0020] when When other values are taken, the output is elliptically polarized light.

[0021] The control relationship between the polarization state, amplitude and phase of the output light is shown in Table 1.

[0022] Table 1

[0023]

[0024]

[0025] Once the entire optical system is complete, the distance between the reflector assembly and the polarization beam splitter prism can be controlled electronically, thereby controlling the state of the output polarized light. This control method makes it easier and faster to control polarized light.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1) The present invention can achieve arbitrary control of the polarization state by changing the distance between the reflector group and the polarization splitter prism and controlling the phase difference and amplitude of the s light and p light respectively with the light modulator, thereby achieving the effect of outputting various forms of polarized light.

[0028] 2) The present invention controls the polarization state of the outgoing light by varying the optical path length difference between s-light and p-light, offering the advantages of easier control and simple operation. Furthermore, the device's components are insensitive to wavelength; polarization control can be achieved for light of different wavelengths simply by varying the distance, resulting in a wide-bandwidth advantage.

[0029] 3) In subsequent applications, based on this light splitting idea, the present invention can independently change the various properties of the two groups of light and then combine them to achieve more control requirements. It can be applied to the control process of Raman light in atomic fountains. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the overall optical path of a method for controlling the polarization state of light based on the interference principle.

[0031] Figure 2 It is a method based on the principle of interference to control the polarization state of light, which involves the amplitude and phase changes of two polarized lights.

[0032] Figure 3 The present invention is a control flow chart of a method for controlling the polarization state of light based on the interference principle.

[0033] In the figure: a first polarization beam splitter prism-1, a p-light modulator-2, a second polarization beam splitter prism-3, a first reflector-4, an s-light modulator-5, a second reflector-6, and an electrically controlled displacement platform-7. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the embodiments and drawings, but the scope of protection of the present invention shall not be limited thereby.

[0035] See Figure 3 FIG. 1 is a schematic flow chart of a method for controlling the polarization state of light based on the interference principle of the present invention. Figure 1 The solution to change the position of the optical platform is to Figure 3 The steps are described in detail:

[0036] Step S1: Build a beam splitting and combining device to control the polarization state of the incident light, including:

[0037] A first polarization beam splitter prism 1 is used to split the incident light into s-light and p-light;

[0038] The second polarization beam splitter prism 3 is used to combine the processed s-light and p-light into one beam for output;

[0039] Optical platform 7: An integrated reflector group and an s-light modulator can be moved by motor control to adjust the distance between the reflector group and the polarization beam splitter prism group.

[0040] The incident light passes through the first polarization beam splitter prism (1) and is split into s-light and p-light, with the propagation directions of the two beams being perpendicular. The p-light is adjusted in amplitude by the p-light modulator (2) and then reaches the second polarization beam splitter prism (3). The s-light passes through the first reflector (4) and changes its propagation direction so that it is parallel to the p-light. Then, it passes through the s-light modulator (5) and has its amplitude adjusted again before reaching the second reflector (6). The propagation direction is changed again so that it is perpendicular to the p-light and then reaches the second polarization beam splitter prism (3). The s-light and p-light are combined into one beam of light at the second polarization beam splitter prism (3) and output.

[0041] By changing the position of the optical platform (7), the phase difference of the p-light relative to the s-light can be changed without affecting the direction of the output light.

[0042] Step S2: According to the requirements of the incident light and the desired output light, the modulation result of the optical modulator is changed to obtain the corresponding amplitudes of the p-light component and the s-light component in the target polarized light. The specific control method is as follows:

[0043] The incident light is Among them A s0 and A p0 are the amplitudes of s light and p light in the incident light, ω is the original frequency of the incident light, k is the light wave vector of the incident light, z is the distance the light propagates, is the phase difference between s-light and p-light.

[0044] First, block the s-light, measure the optical power of the p-light at the output part, adjust the s-light modulator (2), and obtain the corresponding optical power output of the p-light;

[0045] Then, the p light is blocked, the optical power of the s light is measured at the output part, and the p light modulator (5) is changed to obtain the corresponding s light power output;

[0046] Neither the s-light nor the p-light is blocked, and they are superimposed at the output to form polarized light. At this time, the wave equation of the polarized light can be expressed as Among them A s and A p is the amplitude of s light and p light in the required output light, is the phase difference between s-light and p-light.

[0047] Step S3: According to the requirements of the incident light and the desired output light, the distance l between the reflector group and the polarization beam splitter prism is changed to obtain output light with different polarization states. The specific control method is as follows:

[0048] The s-light has an additional optical path difference of 2l, and the corresponding phase difference is The wave function of the output polarized light is The corresponding ellipse equation is:

[0049]

[0050] At this point, we change the position of the optical platform, that is, change the value of l, to obtain outputs with different polarization states. The optical platform is adjustable within a small range by a motor.

[0051] when When , the output light is controlled to be linearly polarized light.

[0052] when When , the output light is controlled to be circularly polarized light or elliptically polarized light.

[0053] when When other values are taken, the output is elliptically polarized light.

[0054] The specific characteristics of the output light, such as the rotation angle of linear polarization and the major and minor axes of elliptically polarized light, are determined by the amplitude relationship between the s-light and p-light in step S2. After determining the value of l, the optical platform is locked to obtain the desired polarized light output.

[0055] The present invention uses the interference method to split the polarized light components in two directions into two paths, adjusts the distance to control the phase and amplitude of the components, realizes the control of the output polarization state, and achieves the purpose of outputting arbitrary polarization state.

[0056] The present invention achieves arbitrary control of the polarization state of light by varying the distance between the reflector assembly and the polarization beam splitter prism, and by using an optical modulator to control the phase difference and amplitude of the S-light and P-light, thereby outputting various polarized light forms. This method offers the advantages of easier control and simple operation. Furthermore, the components used in this device are insensitive to wavelength; polarization can be controlled for light of different wavelengths simply by varying the distance, resulting in a wide-bandwidth solution.

Claims

1. A wide-band dynamic polarization control device based on the interference principle, characterized in that: include: A first polarization beam splitter prism (1), a second polarization beam splitter prism (3), a first reflector (4), a second reflector (6), an S-light modulator (2), and a P-light modulator (5); incident light is split into S-light and P-light by the first polarization beam splitter prism (1); the P-light sequentially passes through the P-light modulator (2) and enters the second polarization beam splitter prism (3); the S-light sequentially passes through the first reflector (4), the S-light modulator (5), and the second reflector (6) and enters the second polarization beam splitter prism (3) to be combined with the P-light for output; By adjusting the modulation parameters of the s-light modulator (2) and the p-light modulator (5), the amplitudes of the p-light and the s-light are independently controlled; By moving an optical platform (7) integrating the first reflector (4) and the second reflector (6), a distance l between the first reflector (4) and the first polarization beam splitting prism (1) is adjusted to change the optical path difference of the S light, thereby controlling the phase difference between the S light and the P light.

2. The wide-band dynamic polarization control device based on the interference principle according to claim 1, characterized in that: It also includes a measuring element for measuring the optical power of the p-light or the s-light respectively when the s-light or the p-light is blocked, so as to assist in adjusting the s-light optical modulator (2) and the p-light optical modulator (5) and set the amplitude of the s-light and the p-light in the output light.

3. The wide-band dynamic polarization control device based on the interference principle according to claim 1, characterized in that: The optical platform is precisely controlled by a motor, so that the value of the distance l can be continuously changed, thereby continuously adjusting the polarization state of the output light.

4. The wide-band dynamic polarization control device based on the interference principle according to any one of claims 1 to 3, characterized in that: When the distance l takes a specific value, the output light is linearly polarized light; when the distance l takes other specific values, the output light is circularly polarized light or special elliptically polarized light; when the distance l takes any other arbitrary value, the output light is general elliptically polarized light.

5. The wide-band dynamic polarization control device based on the interference principle according to claim 4, characterized in that: It also includes a locking mechanism for locking the optical platform after determining the value of the distance l to keep the polarization state of the output light stable.

6. A dynamic polarization control method using the wide-band dynamic polarization control device according to any one of claims 1 to 5, characterized in that: Including steps: Splitting the incident light into s-light and p-light through a first polarization splitting prism; An additional optical path difference is introduced through the reflector group, and the propagation direction of the s light is changed; The amplitudes of the s-light and the p-light are adjusted respectively by an s-light optical modulator (2) and a p-light optical modulator (5); The optical platform is driven by a motor to change the distance l between the reflector group and the polarization beam splitter prism to adjust the phase difference between the s-light and the p-light; The s light and the p light are combined into one output light by a second polarization beam splitter prism; According to needs, the modulation parameters of the s-light modulator (2) and the p-light modulator (5) are adjusted to independently control the amplitudes of the s-light and p-light in the output light; By adjusting the distance l between the reflector group and the first polarization beam splitter prism, the output of linearly polarized light, circularly polarized light or elliptically polarized light can be achieved.

7. The dynamic polarization control method according to claim 6, wherein: When the s light is blocked, the first light modulator (2) is adjusted so that the amplitude of the p light reaches a target value; When the p light is blocked, the second light modulator (5) is adjusted so that the amplitude of the s light reaches a target value.

8. The dynamic polarization control method according to claim 6, wherein: when When , the output light is linearly polarized light; when When , the output light is circularly polarized light or elliptically polarized light; when When other values are taken, the output light is elliptically polarized light; in, is the phase difference between s-light and p-light, k is the wave vector of the incident light, l is the distance between the reflector group and the polarization beam splitter prism, and N is a positive integer.

Images