Polarization-independent needle-shaped light generation system and method

Abstract

The invention relates to a polarization-independent needle-shaped light generation system and method, and relates to the technical field of optical communication, and the polarization-independent needle-shaped light generation system comprises a light source; the dual-polarization assembly comprises a light path element and a spatial light modulator, the light path element is used for dividing the incident light output by the light source into two polarized light and converting the two polarized light into target polarized light capable of being modulated by the spatial light modulator, and the complex amplitude of the needle-shaped light is written into the spatial light modulator so as to modulate the target polarized light to generate polarization-independent needle-shaped light. According to the invention, signals in any polarization state can be processed, incident light is focused into a needle shape, and the diffraction-free characteristic is kept in a design range, so that the quality of received signals is ensured.

Description

Technical Field

[0001] The present invention relates to the field of optical communication technology, and in particular to a polarization-independent needle-shaped light generation system and method. Background Art

[0002] In recent years, space optical communication has attracted more and more attention due to its advantages such as high bandwidth, good confidentiality, multiple unlicensed frequency bands and low cost, and is widely regarded as the next generation of high-speed wireless communication technology. Compared with radio communication, space optical communication has greater potential in campus interconnection, video surveillance, storage area network and military access.

[0003] However, current space optical links often use Gaussian light as the carrier. When propagating over long distances, the diffraction effect will cause the beam to diverge and become wider, and the peak intensity will weaken, resulting in large power loss, mode crosstalk and loss during reception. Especially in the communication link from ground stations to drones / aircraft, ground stations usually have a larger transmit aperture, while drones / aircraft usually have a smaller receive aperture. This requires a narrow and low-divergence beam to maintain its propagation-invariant characteristics over a fairly long distance. Summary of the invention

[0004] The present application provides a polarization-independent needle-shaped light generation system and method, which can process signals of any polarization state and focus the incident light into a needle shape, maintaining a diffraction-free characteristic within a designed range, thereby ensuring the quality of the received signal.

[0005] In a first aspect, an embodiment of the present application provides a polarization-independent needle-shaped light generating system, the polarization-independent needle-shaped light generating system comprising:

[0006] light source;

[0007] A dual polarization component comprises an optical path element and a spatial light modulator, wherein the optical path element is used to split the incident light output by the light source into two polarized lights and convert the light into a target polarized light modulatable by the spatial light modulator, wherein the spatial light modulator is written with the complex amplitude of the needle-shaped light to modulate the target polarized light to generate polarization-independent needle-shaped light.

[0008] In combination with the first aspect, in one implementation, the optical path element includes:

[0009] A beam splitter prism, which is used to receive the incident light output by the light source;

[0010] A polarization beam splitter prism, used to split the light beam output by the beam splitter prism into two orthogonal polarized lights;

[0011] A reflector assembly, comprising a first branch and a second branch, wherein the first branch is provided with a first reflector, and the first reflector is used to directly input a polarized light into the spatial light modulator, and the first branch is provided with a second reflector and a half-wave plate, and the second reflector is used to input another polarized light into the half-wave plate for conversion, and then input into the spatial light modulator;

[0012] The reflector assembly is also used to receive the light beam modulated by the spatial light modulator and output it to the lens through the beam splitter prism.

[0013] In combination with the first aspect, in one implementation, the light source is a collimated light source, and the collimated light source includes a laser and a collimator.

[0014] In combination with the first aspect, in one implementation, the laser is a narrow linewidth external cavity tunable laser.

[0015] In combination with the first aspect, in one implementation, the spatial light modulator is a modulator that only modulates the phase.

[0016] In a second aspect, an embodiment of the present application provides a polarization-independent needle-shaped light generation method, the polarization-independent needle-shaped light generation method comprising:

[0017] The dual polarization component is used to split the incident light output by the light source into two polarized lights, and convert them into target polarized lights that can be modulated by the spatial light modulator;

[0018] The target polarized light is modulated by the spatial light modulator to generate polarization-independent needle-shaped light.

[0019] In conjunction with the second aspect, in one implementation,

[0020] According to the formula: The phase of the needle light is written into the spatial light modulator, where k is the wave vector, β is a value related to the design distance, and ρ is the pole distance.

[0021] In conjunction with the second aspect, in one implementation,

[0022] According to the formula: The amplitude of the needle light is written into the spatial light modulator, where A OPB is a parameter related to the amplitude, ρ is the pole pitch, and when the pole pitch approaches 0, the amplitude is 0.

[0023] In combination with the second aspect, in one implementation, the spatial light modulator is a modulator that only modulates the phase.

[0024] In conjunction with the second aspect, in one implementation, a beam splitter grating is used so that the phase written into the spatial light modulator satisfies:

[0025] in, A is the amplitude, is the phase, is the grating phase.

[0026] The beneficial effects brought by the technical solution provided in the embodiments of the present application include:

[0027] The polarization-independent needle-shaped light generating system in the present application utilizes a dual-polarization component to split the incident light output by a light source into two polarized lights, and converts the light into a target polarized light modulated by a spatial light modulator; and utilizes a complex amplitude spatial light modulator with needle-shaped light written therein to modulate the target polarized light to generate needle-shaped light.

[0028] That is, the present application uses a dual polarization component to split the incident light into two polarized lights, and then processes the two components separately, and finally merges them, which can reduce the impact of polarization on system performance. Thus, it can process signals of any polarization state, and at the same time focus the incident light into a needle shape, maintaining the non-diffraction characteristics within the design range, thereby ensuring the quality of the received signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 A structural block diagram of an embodiment of a polarization-independent needle-shaped light generating system of the present application;

[0031] Figure 2 This is a schematic structural diagram of an embodiment of a dual polarization component of the present application;

[0032] Figure 3 This is the principle diagram of needle light generation for this application;

[0033] Figure 4 This is a schematic diagram of the needle-shaped light phase superposition of this application;

[0034] Figure 5 This is a schematic diagram of the needle beam space separation of this application;

[0035] Figure 6 This is a schematic diagram of the light field intensity at the focal position of the needle-shaped light beam of this application;

[0036] Figure 7 This is a schematic diagram of the light field intensity after the needle-shaped light of this application is focused for a certain distance;

[0037] Figure 8 This is a flow chart of an embodiment of a polarization-independent needle-shaped light generating method of the present application. DETAILED DESCRIPTION

[0038] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0039] In order to make the objectives, technical solutions and advantages of the present application clearer, the implementation methods of the present application will be further described in detail below with reference to the accompanying drawings.

[0040] In a first aspect, an embodiment of the present application provides a polarization-independent needle-shaped light generating system.

[0041] In one embodiment, referring to Figure 1 , Figure 1 FIG. 1 is a structural block diagram of an embodiment of a polarization-independent needle-shaped light generating system of the present application. Figure 1 As shown, the polarization-independent needle light generation system includes a light source and a dual polarization component

[0042] The light source is used to output incident light to the dual polarization component. In the present embodiment, the light source is a collimated light source. Specifically, the collimated light source includes a laser and a collimator. Preferably, the laser is a narrow linewidth external cavity tunable laser. Of course, other types of lasers can also be selected as needed, and this embodiment does not limit this.

[0043] A dual polarization component comprises an optical path element and a spatial light modulator, wherein the optical path element is used to split the incident light output by the light source into two polarized lights and convert the light into a target polarized light modulatable by the spatial light modulator, wherein the spatial light modulator is written with the complex amplitude of the needle-shaped light to modulate the target polarized light to generate polarization-independent needle-shaped light.

[0044] For details, see Figure 2 As shown, the optical path elements include a beam splitter prism, a polarization beam splitter prism and a reflector assembly.

[0045] The beam splitter prism is used to receive the incident light output by the light source, and the polarization beam splitter prism is used to split the light beam output by the beam splitter prism into two orthogonal polarized lights.

[0046] The reflector assembly includes a first branch and a second branch. The first branch is provided with a first reflector, which is used to directly input a polarized light into the spatial light modulator. The first branch is provided with a second reflector and a half-wave plate, which is used to input another polarized light into the half-wave plate for conversion and then input into the spatial light modulator. The reflector assembly is also used to receive the light beam modulated by the spatial light modulator and output it to the lens through a beam splitter prism.

[0047] It is worth noting that, generally speaking, a spatial light modulator can only modulate one of the polarization states, namely the target polarization state. For the other polarization state that cannot be modulated, a half-wave plate is required to convert it into a usable polarized light.

[0048] It can be understood that this embodiment uses a polarization beam splitter to split light into two orthogonal polarization components, and then processes the two components separately and finally combines them, which can reduce the impact of polarization on system performance and thus achieve polarization independence.

[0049] The principle of the polarization-independent spatial light obstacle avoidance system is explained below:

[0050] First, the optical path needs to be adjusted. In this embodiment, a light source with a wavelength of 1550nm is taken as an example. Since the 1550nm light source is invisible to the naked eye, when adjusting the dual-polarization optical path, the optical path should be roughly adjusted using visible light, and then the CCD (Charge-Coupled Device) is used to observe the light beam and fine-tune the optical path to ensure that the dual-polarization light is incident on the same position on the spatial light modulator and the light beams overlap when emitted from the dual-polarization part.

[0051] The specific operation of fine-tuning is as follows: first load the vortex phase on the spatial light modulator, place the CCD between the first reflector on the left and the spatial light modulator, adjust the optical path so that a standard circular ring can be observed on the CCD, indicating that the polarized light is now located at the center of the loaded phase, and then place the CCD between the second reflector on the right and the spatial light modulator. Repeat the above operation to make the dual polarized light incident on the same position on the spatial light modulator; when adjusting the overlap of the outgoing light beams, the CCD should be placed between the dual polarization component and the lens, and the optical path should be adjusted until only one light spot is observed on the CCD. Since adjusting the optical path will affect the position of the incident light and the outgoing light at the same time, the above operation needs to be performed multiple times. In order to verify the accuracy of the final optical path, a polarization controller can be added in front of the collimated light source to change the polarization state of the laser. If the outgoing light does not change, it means that the system is polarization independent.

[0052] Needle light is generated by radially superimposing Airy-like beams using the principle of caustics. Its transverse wave vectors cancel each other out, and all wave components propagate in the same direction. For the specific generation principle, see Figure 3As shown. Needle-shaped light can be directly modulated by phase: Among them, k is the wave vector, β is a value related to the design distance, and ρ is the pole distance.

[0053] In order to keep the needle beam constant or with low amplitude variation during propagation, its amplitude can be modulated as follows: Among them, A OPB is a parameter related to the amplitude, ρ is the pole pitch, and because the amplitude diverges when the radius approaches 0, the amplitude within the radius ρ0 is set to 0.

[0054] Since the current spatial light modulator can only modulate the phase or the amplitude, it cannot modulate the amplitude and phase at the same time. When the spatial light modulator used is phase-only, in order to write the amplitude and phase at the same time, the principle of the beam splitter grating is used to make the phase satisfy:

[0055] in, A is the amplitude, is the phase, is the grating phase, and Mod means remainder.

[0056] For the specific phase superposition process, see Figure 4 As shown, the first picture represents the image of M, the second picture represents F, and the third picture represents Additive representation The final multiplication gives the desired phase: Since the phase is in period 2π, and The images are the same image.

[0057] In addition, the beam splitter grating can be used to split two beams of light deflected in any direction, so as to perform spatial division multiplexing of the spatial light and transmit signals to multiple targets at the same time. Figure 5 The light field intensity at the focus position and after focusing for a certain distance is shown as follows: Figure 6 and Figure 7 shown.

[0058] In summary, the polarization-independent needle-shaped light generating system in the present application utilizes a dual-polarization component to split the incident light output by a light source into two polarized lights, and converts them into target polarized light modulatable by a spatial light modulator; and utilizes a complex amplitude spatial light modulator with needle-shaped light written therein to modulate the target polarized light to generate needle-shaped light.

[0059] That is, the present application uses a dual polarization component to split the incident light into two polarized lights, and then processes the two components separately, and finally merges them, which can reduce the impact of polarization on system performance. Thus, it can process signals of any polarization state, and at the same time focus the incident light into a needle shape, maintaining the non-diffraction characteristics within the design range, thereby ensuring the quality of the received signal.

[0060] In a second aspect, an embodiment of the present application provides a polarization-independent needle-shaped light generation method.

[0061] In one embodiment, referring to Figure 8 , Figure 8 This is a flow chart of an embodiment of a polarization-independent needle-shaped light generation method of the present application. Figure 8 As shown, the polarization-independent needle-like light generation method includes:

[0062] S1, using the dual polarization component to split the incident light output by the light source into two polarized lights, and converting them into target polarized lights modulatable by the spatial light modulator;

[0063] S2. Modulate the target polarized light using the spatial light modulator to generate polarization-independent needle-shaped light.

[0064] Furthermore, in one embodiment,

[0065] According to the formula: The phase of the needle light is written into the spatial light modulator, where k is the wave vector, β is a value related to the design distance, and ρ is the pole distance.

[0066] Furthermore, in one embodiment,

[0067] According to the formula: The amplitude of the needle light is written into the spatial light modulator, where A OPB is a parameter related to the amplitude, ρ is the pole pitch, and when the pole pitch approaches 0, the amplitude is 0.

[0068] Furthermore, in one embodiment, the spatial light modulator is a modulator that only modulates the phase.

[0069] Furthermore, in one embodiment, a beam splitter grating is used so that the phase written into the spatial light modulator satisfies:

[0070] in, A is the amplitude, is the phase, is the grating phase.

[0071] In the description of the present application, it should be noted that the terms "upper", "lower", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0072] It should be noted that, in this application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0073] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A polarization-independent needle-shaped light generating system, characterized in that: The polarization-independent needle-shaped light generating system comprises: light source; A dual polarization component comprises an optical path element and a spatial light modulator, wherein the optical path element is used to split the incident light output by the light source into two polarized lights and convert the light into a target polarized light modulatable by the spatial light modulator, wherein the spatial light modulator is written with the complex amplitude of the needle-shaped light to modulate the target polarized light to generate polarization-independent needle-shaped light.

2. The polarization-independent needle-shaped light generating system according to claim 1, characterized in that: The optical path element comprises: A beam splitter prism, which is used to receive the incident light output by the light source; A polarization beam splitter prism, used to split the light beam output by the beam splitter prism into two orthogonal polarized lights; A reflector assembly, comprising a first branch and a second branch, wherein the first branch is provided with a first reflector, and the first reflector is used to directly input a polarized light into the spatial light modulator, and the first branch is provided with a second reflector and a half-wave plate, and the second reflector is used to input another polarized light into the half-wave plate for conversion, and then input into the spatial light modulator; The reflector assembly is also used to receive the light beam modulated by the spatial light modulator and output it to the lens through the beam splitter prism.

3. The polarization-independent needle-light generating system according to claim 1, characterized in that: The light source is a collimated light source, and the collimated light source includes a laser and a collimator.

4. The polarization-independent needle-light generating system according to claim 3, characterized in that: The laser is a narrow line width external cavity tunable laser.

5. The polarization-independent needle-light generating system according to claim 1, characterized in that: The spatial light modulator is a modulator that modulates only the phase.

6. A polarization-independent needle-shaped light generating method using the polarization-independent needle-shaped light generating system according to claim 1, characterized in that: The polarization-independent needle-shaped light generation method comprises: The dual polarization component is used to split the incident light output by the light source into two polarized lights, and convert them into target polarized lights that can be modulated by the spatial light modulator; The target polarized light is modulated by the spatial light modulator to generate polarization-independent needle-shaped light.

7. The polarization-independent needle-shaped light generation method according to claim 6, characterized in that: According to the formula: The phase of the needle light is written into the spatial light modulator, where k is the wave vector, β is a value related to the design distance, and ρ is the pole distance.

8. The polarization-independent needle-shaped light generation method according to claim 7, characterized in that: According to the formula: The amplitude of the needle light is written into the spatial light modulator, where A OPB is a parameter related to the amplitude, ρ is the pole pitch, and when the pole pitch tends to 0, the amplitude is 0.

9. The polarization-independent needle-shaped light generation method according to claim 6, characterized in that: The spatial light modulator is a modulator that modulates only the phase.

10. The polarization-independent needle-shaped light generating method according to claim 9, characterized in that: A beam splitter grating is used to make the phase written into the spatial light modulator satisfy: in, A is the amplitude, is the phase, is the grating phase.

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