Systems and methods for generating a longitudinally structured light beam to improve transmission in a turbulent flow

Abstract

Methods and systems for generating a longitudinally structured light beam to improve transmission in a turbulent flow are disclosed. The method includes receiving turbulence information indicative of a location of a turbulent flow region; determining a spatial mode of a light beam based on the location of the turbulent flow region; and generating instructions for generating a longitudinally structured light beam comprising the spatial mode, wherein the longitudinally structured light beam comprises a smaller light beam width at the location of the turbulent flow region compared to a light beam width outside of the location of the turbulent flow region.

Description

Technical Field

[0001] The disclosure of this paper generally relates to free-space optics, and more specifically to generating longitudinally structured beams to improve transmission in turbulent flow. Background Technology

[0002] Free-space optics transmission provides the ability to transmit data or light through space, such as air or a vacuum, without the need for optical fibers or other guiding media. In many applications of free-space optics, a fundamental Gaussian beam is typically used. However, turbulence in the transmission path of free-space optics, such as lasers, can distort the beam. Turbulence effects can significantly distort the transmitted Gaussian beam and degrade system performance. Previous techniques, such as adaptive optics (AO), have been proposed to mitigate wavefront distortion caused by turbulence in Gaussian beams. However, these methods require additional optical and electrical components, as well as complex signal processing and feedback loops. Furthermore, while these mitigation methods address the cumulative effects throughout the beam propagation path, they are not specifically designed and optimized for cases where turbulence intensity varies along the path. A fundamental Gaussian beam with a single Gaussian spatial mode diverges, and its beam width increases as the beam propagates. Therefore, its beam width cannot be easily customized at any distance.

[0003] These and other drawbacks exist. Therefore, a Gaussian beam that can be tuned along its path based on the location of the turbulence is needed to improve spatially free optical transmission in turbulence. Summary of the Invention

[0004] The described subject matter relates to systems, methods, apparatuses, and computer-readable storage media for generating longitudinally structured beams to improve transmission in turbulent flow. An example method for generating longitudinally structured beams to improve transmission in turbulent flow includes: receiving turbulence information indicating the location of a turbulent region by a computing device. The method includes: determining multiple spatial patterns of the beam by the computing device based on the location of the turbulent region. The method further includes: generating instructions by the computing device for generating a longitudinally structured beam including multiple spatial patterns, wherein the longitudinally structured beam at the location in the turbulent region includes a smaller beam width compared to the beam width outside the location in the turbulent region.

[0005] In one aspect of the described method, the method includes: sending generated instructions from a computing device to a spatial light modulator to generate a longitudinally structured beam, wherein the beam is incident from a laser onto the spatial light modulator.

[0006] In one aspect of the described method, the generated instructions are used to narrow the beam width of the longitudinally structured beam when it reaches the location of the turbulent region and widen it when it passes through the location of the turbulent region.

[0007] In one aspect of the described method, the method includes: generating a longitudinally structured beam from an aircraft, wherein the longitudinally structured beam is configured for optical communication.

[0008] In one aspect of the described method, turbulence information indicates the turbulence intensity at a turbulent region, wherein the width of the longitudinally structured beam at the turbulent region is based on the turbulence intensity.

[0009] In one aspect of the described method, the multiple spatial modes include multiple Bessel-Gaussian spatial modes, each of which includes a different P-wave number.

[0010] In one aspect of the described method, different P-wave numbers include equal spatial frequency intervals.

[0011] An example system for generating longitudinally structured beams to improve transmission in turbulence includes: a computing device communicatively connected to a spatial light modulator. The computing device includes a processor and a memory storing instructions that, when executed by the processor, cause the processor to: receive turbulence information indicating the location of a turbulent region; determine multiple spatial patterns of the beam based on the location of the turbulent region; and generate instructions for generating a longitudinally structured beam including the multiple spatial patterns, wherein the longitudinally structured beam at the location of the turbulent region includes a smaller beam width compared to the beam width outside the location of the turbulent region.

[0012] In one aspect of the described system, instructions cause the processor to send generated instructions to a spatial light modulator to generate a longitudinally structured beam, wherein the beam is incident from a laser onto the spatial light modulator.

[0013] In one aspect of the described system, the generated instructions are used to narrow the beam width of the longitudinally structured beam when it reaches the location of the turbulent region and widen it when it passes through the location of the turbulent region.

[0014] In one aspect of the described system, the system includes an aircraft from which a longitudinally structured beam is generated, wherein the longitudinally structured beam is configured for optical communication.

[0015] In one aspect of the described system, turbulence information indicates the turbulence intensity at a turbulent region, wherein the width of the longitudinally structured beam at the turbulent region is based on the turbulence intensity.

[0016] In one aspect of the described system, the multiple spatial modes include multiple Bessel-Gaussian spatial modes, each of which includes a different P-wave number.

[0017] In one aspect of the system described, different longitudinal wave numbers include equal spatial frequency intervals.

[0018] An example non-transitory computer-readable storage medium includes instructions that, when executed by a processor of a device, cause the processor to: receive turbulence information indicating the location of a turbulent region; determine multiple spatial patterns of a beam based on the location of the turbulent region; and generate instructions for generating a longitudinally structured beam including the multiple spatial patterns, wherein the longitudinally structured beam includes a smaller beam width at the location of the turbulent region compared to the beam width outside the location of the turbulent region.

[0019] In one aspect of the described non-transitory computer-readable storage medium, the instructions cause a processor to send generated instructions to a spatial light modulator to generate a longitudinally structured beam, wherein the beam is incident from a laser onto the spatial light modulator.

[0020] In one aspect of the described non-transitory computer-readable storage medium, the generated instructions are used to narrow the beam width of a longitudinally structured beam when the longitudinally structured beam reaches a location in a turbulent region and to widen it when it passes through a location in a turbulent region.

[0021] In one aspect of the described non-transitory computer-readable storage medium, the non-transitory computer-readable storage medium includes an aircraft that generates a longitudinally structured beam, wherein the longitudinally structured beam is configured for optical communication.

[0022] In one aspect of the described non-transitory computer-readable storage medium, turbulence information indicates the turbulence intensity at a turbulent region, wherein the width of the longitudinally structured beam at the turbulent region is based on the turbulence intensity.

[0023] In one aspect of the described non-transitory computer-readable storage medium, the plurality of spatial modes include a plurality of Bessel-Gaussian spatial modes, each of which includes a different longitudinal wave number. Attached Figure Description

[0024] To facilitate identification of any discussion of a particular element or action, one or more of the highest-order digits in the figure references indicate the figure number in which the element was first introduced.

[0025] Figure 1 A system for generating longitudinally structured beams for improving communication in turbulent flow is shown.

[0026] Figure 2 This is a schematic diagram of a longitudinally structured beam passing through a turbulent region.

[0027] Figure 3 This is a schematic diagram of a longitudinally structured beam passing through multiple turbulent regions.

[0028] Figure 4 A graph showing different longitudinal wave numbers in a Bessel-Gaussian spatial mode and the on-axis intensity and width of the beam obtained by the coherent superposition of the modes is presented.

[0029] Figure 5 An example method for generating longitudinally structured beams for improving transmission in turbulent flow is shown according to one embodiment. Detailed Implementation

[0030] The following description of the embodiments provides non-limiting representative examples of the reference numerals to specifically describe the features and teachings of different aspects of the disclosure herein. The described embodiments are to be considered as being able to be implemented alone or in combination with other embodiments, and the features and teachings of any embodiment can be interchangeably combined with the features and teachings of any other embodiment. Those skilled in the art will be able to learn and understand the different aspects of the disclosure herein upon reading the description of the embodiments. The description of the embodiments is so helpful in understanding the disclosure herein that other implementations not specifically covered but within the scope of knowledge of those skilled in the art upon reading the description of the embodiments will be understood to be consistent with the application of the disclosure herein.

[0031] Furthermore, the features, advantages, and characteristics described in the embodiments can be combined in any suitable manner. Those skilled in the art will recognize that these embodiments can be practiced without one or more specific features or advantages of each embodiment. In other cases, additional features and advantages that may not be present in all embodiments may be recognized in some embodiments. Those skilled in the art will understand that the features, advantages, and characteristics described in any embodiment can be combined interchangeably with the features, advantages, and characteristics of any other embodiment.

[0032] The systems and methods disclosed herein relate to generating longitudinally structured beams to improve transmission in turbulent environments. Turbulence is the irregular flow of air and typically occurs in the atmosphere due to temperature variations. Turbulence also occurs near flying aircraft, caused by the aircraft's own motion and engines. Turbulence leads to changes in refractive index, thereby distorting light waves and hindering free-space optics. The degree of distortion of a laser beam traveling through turbulence is related to the size of the beam's cross-sectional area, which is also referred to herein as the beam width. A beam with a smaller width will incur less distortion when passing through a turbulent region than a corresponding beam with a larger width. Specifically, narrowing the beam's cross-section minimizes higher-order optical wavefront distortion in turbulent environments.

[0033] The described subject provides novel systems and methods for minimizing higher-order optical wavefront distortions caused by turbulent environments, particularly when turbulence intensity varies along the beam's propagation path, by cropping the beam width along the path to a smaller width in the turbulent region compared to its width outside the turbulent region. The described beam is a longitudinally structured beam, where the beam width can be customized and tuned with distance. The beam consists of multiple coherently superimposed Bessel-Gaussian spatial modes. These spatial modes describe the intensity and phase distribution across the beam cross-section.

[0034] Due to the constructive and destructive interference between multiple Bessel-Gaussian modes, the beam width of a longitudinally structured beam at a given distance can be customized by designing the complex coefficients of the Bessel-Gaussian spatial modes. Furthermore, each Bessel-Gaussian spatial mode can have a different longitudinal wavenumber k. z P-wave number k z The spatial frequency of a wave is measured as the number of wavelengths per unit length. The longitudinal wave number k is... z They can have equal spatial frequency spacing. Adjust the P-wave number k of the Bessel-Gaussian spatial mode. z The resulting constructive or destructive interference with other modes of the beam is determined, and the complex coefficients are adjusted to determine the amplitude of the induced interference and the location on the beam along the propagation path where interference occurs. By having a smaller beam width in areas of strong turbulence, smaller wavefront errors accumulate in those regions. This effect is analogous to imaging under turbulent conditions, where, for a given turbulence intensity, image quality deteriorates with increasing aperture, particularly when the aperture becomes larger than the coherence length of atmospheric turbulence, i.e., the Fried parameter. For a given Fried parameter, for a smaller beam width, fewer higher-order wavefront errors accumulate.

[0035] Unlike a basic Gaussian beam (which has only a single Gaussian spatial mode) that diverges and broadens as it propagates and cannot be easily customized at any distance, a longitudinally structured beam can be customized at any distance. Furthermore, compared to previous methods such as adaptive optics for mitigating distortions from turbulence, longitudinally structured beams mitigate turbulence by being customized to adapt to distance-varying turbulence without requiring additional wavefront correction. Therefore, longitudinally structured beams do not require additional optical and electrical components or complex signal processing and feedback loops for beam customization.

[0036] The computing device receives turbulence information, including the locations of one or more turbulent regions and potentially the corresponding turbulence intensities of those regions. Based on the turbulence information, the computing device determines a Bessel-Gaussian spatial pattern for the beam. The spatial pattern is determined to be a Bessel-Gaussian beam tuned such that, when superimposed, it yields a longitudinally structured beam with different beam widths along various longitudinal distances based on constructive and destructive interference between the combined patterns. The computing device then generates instructions for generating a longitudinally structured beam comprising multiple spatial patterns, wherein the longitudinally structured beam at the locations of the turbulent regions includes a smaller beam width compared to the beam width outside the locations of the turbulent regions. Without limitation, example applications include optical transmitters mounted on aircraft, where much stronger turbulence is expected in their vicinity due to the aircraft's motion and engines. The aircraft can implement the described longitudinally structured beam to customize its transmitted beam, such as for communication or sensing, and to reduce distortion caused by turbulence. Aircraft can also utilize longitudinally structured beams to reduce beam distortion caused by unevenly distributed atmospheric turbulence at different altitudes, which is typically stronger at lower altitudes. Longitudinally structured beams can be implemented to transmit free-space optical signals through any source of turbulence, including unmanned aerial vehicles (UAVs) and satellites. This presents challenges in various applications across different flight platforms, such as free-space optical communication or sensing.

[0037] The reference to beam width refers to the width of the beam's cross-section, which is perpendicular to the beam's propagation path z. It should also be understood that the beam width affects the beam's cross-sectional area; therefore, a narrower or wider beam refers to a smaller or larger cross-sectional area, respectively.

[0038] In the following description, numerous specific details are set forth for illustrative purposes to provide a thorough understanding thereof. However, it may be apparent that new embodiments can be practiced without these specific details. In other instances, well-known structures and apparatuses are shown in block diagram form to facilitate their description.

[0039] Figure 1 A system 100 for generating longitudinally structured beams to improve communication in turbulent flow is illustrated. System 100 may include a computing device 102, which includes at least one processor 104 and memory 106. The computing device 102 may be a network-enabled computer and communicatively connected to a database 108. As described herein, a network-enabled computer may include, but is not limited to, computer devices or communication devices, including, for example, servers, network devices, personal computers, workstations, telephones, handheld PCs, personal digital assistants, thin clients, fat clients, internet browsers, or other devices. Although Figure 1 Only one database is shown, but it should be understood that database 108 may include multiple databases. Database 108 may include at least one database accessed by computing device 102 via network 110.

[0040] The computing device 102 can execute one or more applications, such as software applications, that enable, for example, network communication with one or more components of system 100, sending and / or receiving data, and performing the functions and processes described herein. System 100 may include one or more networks 110. In some examples, network 110 may be one or more of a wireless network, a wired network, or any combination of wireless and wired networks. For example, network 110 may include one or more of the following: fiber optic network, passive optical network, cable network, Internet network, network utilizing free-space optics, satellite network, wireless local area network (LAN), Global System for Mobile Communications (GSMO), personal communication service, personal area network, wireless application protocol, multimedia messaging service, enhanced messaging service, short message service, time division multiplexing-based system, code division multiple access-based system, D-AMPS, Wi-Fi, fixed wireless data, IEEE 802.11 series networking, Bluetooth, NFC, radio frequency identification (RFID), Wi-Fi, etc.

[0041] Additionally, network 110 may include, but is not limited to, telephone lines, fiber optic cables, IEEE Ethernet 802.3, wide area networks, wireless personal area networks, LANs, or global networks such as the Internet. Furthermore, network 110 may support Internet networks, wireless communication networks, cellular networks, and any combination thereof. Network 110 may also include one or more networks of the aforementioned exemplary types, which operate as independent networks or cooperate with each other. Network 110 may utilize one or more protocols of one or more network elements communicatively coupled thereto. Network 110 may convert other protocols to one or more protocols of network devices or convert one or more protocols of network devices to other protocols. Although network 110 is depicted as a single network, it should be understood that, according to one or more examples, network 110 may include multiple interconnected networks, such as, for example, the Internet, service provider networks, cable television networks, corporate networks such as credit card association networks, and home networks.

[0042] The computing device 102 is communicatively connected to an optical terminal 112 having at least one laser 114 and at least one spatial light modulator 116. The optical terminal 112 can utilize free-space optics for communication or sensing. The optical terminal 112 can be located, for example, in an aircraft, satellite, or ground station. Figure 2As shown, optical terminal 112 can communicate with a remote optical terminal, which may be located in another aircraft, satellite, or ground station, by transmitting data via a beam generated by laser 114. Optical terminal 112 can use the beam generated by laser 114 for sensing, such as weather monitoring or mapping.

[0043] Laser 114 emits a laser beam, which system 100 can modify to produce a longitudinally structured beam as described herein. Laser 114 may include, for example, a gas laser (e.g., a CO2 laser), a solid-state laser, a fiber laser, and a semiconductor laser. Laser 114 can produce a beam with a beam waist of any size, such as 5 mm or smaller, 6 mm, 7 mm, 8 mm, 9 mm or larger, or in between. Laser 114 can emit a beam incident on spatial light modulator 116, the wavelength of which corresponds to wavelengths typically realized in free-space optics, such as, but not limited to, wavelengths in the near-infrared (NIR) or short-wave infrared (SWIR) spectrum, or any other wavelength.

[0044] Spatial light modulator 116 can be programmable to customize the beam emitted by laser 114. Spatial light modulator 116 can adjust the properties of the beam to one or more values ​​defined by computing device 102. These defined values ​​can be received from computing device 102. Specifically, spatial light modulator 116 can generate multiple spatial modes of the incident beam, each with a different longitudinal wavenumber and an amplitude customized based on complex coefficients determined by computing device 102. Spatial light modulator 116 can coherently superimpose the customized modes to obtain a longitudinally structured beam.

[0045] The computing device 102 determines the composition of the longitudinally structured beam to propagate in the z-direction based on the turbulence in the path of the beam transmitted by the laser 114. To reduce beam distortion caused by turbulence in the beam's propagation path, the computing device 102 determines the spatial modes of the beam, namely Bessel-Gaussian spatial modes, which result in a longitudinally structured beam with a smaller width at turbulent locations due to the coherent superposition of Bessel-Gaussian modes caused by constructive and destructive interference between modes.

[0046] The computing device 102 receives turbulence information including the locations of one or more turbulent regions. The turbulence information may also include the turbulence intensity of each turbulence region. In some embodiments, the turbulence intensity may include at least one Friedel-Crafts parameter for each turbulence region. The turbulence information may be generated locally, for example, on an aircraft having system 100, or received from a remote source via network 110. The turbulence information may also include the current or expected movement of the turbulence. The computing device 102 may receive the turbulence information from various sources, including LiDAR, weather radar, air traffic control reports, real-time pilot reports, etc. In some embodiments, the computing device 102 determines the Bessel-Gaussian pattern of the beam with a z-correlation width only when the turbulence intensity exceeds a threshold. The computing device 102 may determine the expected location of the turbulence region relative to the beam to be emitted, and generate a longitudinally structured beam based on the expected relative position of the turbulence location. The computing device 102 may combine the expected location of the beam to be emitted from optical terminal 112 with the turbulence information to determine the location and corresponding turbulence intensity of the turbulence. The computing device 102 can determine the relative position of the turbulent region with respect to the beam expected to be emitted from the optical terminal 112 based on the position and movement of the optical terminal 112, the destination and turbulent region of the beam, and the expected time when the beam will be emitted.

[0047] In some embodiments of system 100 on an aircraft, computing device 102 may have historical data on turbulence generated by the aircraft in flight, stored in memory 106 or retrieved from database 108. The historical data may include turbulence information depending on the aircraft's flight state. The flight state may include the aircraft's altitude, speed, attitude, and / or model. Computing device 102 may retrieve turbulence information corresponding to the aircraft's current flight state, which may be used independently or in combination with other turbulence information to generate a longitudinally structured beam.

[0048] The computing device 102 determines the different P-wave numbers k z Multiple Bessel-Gaussian (BG) spatial modes are used to determine the composition of a longitudinally structured beam with range-dependent or z-dependent widths. Each Bessel-Gaussian (BG) spatial mode has an orbital angular momentum (OAM) l equal to zero. The value l is the number of 2π phase shifts in the azimuth direction. The value k z With radial wave number k r Related, k r Determine the radial ring spacing in the intensity distribution. Value k z and k r satisfy

[0049]

[0050] Where λ is the wavelength. The computing device 102 determines the k of the l=0 order BG spatial mode based on the desired z-correlated beam width. z Complex coefficients. For example... Figure 4 As shown, the longitudinal wavenumber k z It can have equal spatial frequency spacing, forming a series of uniformly spaced frequencies or a "comb" in the space-frequency domain. It propagates along the z-axis from z=0 to z=L and includes frequencies at the same optical frequencies. The waveform equations for the longitudinally structured beams of the (2N+1) BG spatial modes are as follows:

[0051]

[0052] Where ρ is the radius in cylindrical coordinates; For transverse wave number, Let be the P-wave number, where ; It is a Gaussian apodization and can be selected by the computing device 102, such that all BG space modes have low divergence over the relevant longitudinal range. Coefficients It is given by the following formula:

[0053]

[0054] Where the function Define the desired central intensity distribution along the longitudinal axis. For example, for a beam with high intensity at the z-axis, which is the central axis, and therefore at a distance... A longitudinally structured beam with a narrow beam width, function It could be:

[0055]

[0056] Therefore, the computing device 102 can determine the distance range on the z-axis, i.e. This results in a beam with a smaller width than elsewhere, and accordingly determines the longitudinal wave number k. z The complex coefficients.

[0057] Spatial light modulator 116 modulates the incident coherent light from laser 114 to generate light with different longitudinal wavenumbers k. z The coherent superposition of multiple co-propagating BG spatial modes of order l=0. The spatial light modulator 116 receives instructions from the computing device 102 to generate multiple BG spatial modes of the beam incident on the spatial light modulator 116, each BG spatial mode having a different longitudinal wavenumber k. z And custom complex coefficients, which determine the z-correlation amplitude. The spatial light modulator 116 is based on instructions received from the computing device 102, specifically the BG spatial mode and its corresponding different P-wave numbers k. zComplex coefficients are used to generate a hologram. When the beam is incident on the hologram, the hologram structures the spatial amplitude and phase of the beam to generate a BG spatial pattern. The BG spatial patterns are coherently superimposed to obtain a longitudinally structured beam.

[0058] System 100 may also include an optical system to filter out the desired longitudinally structured beam and remove any unwanted diffraction orders. For example, system 100 may include a 4f optical system 118 and an aperture 120. After passing through the hologram generated by the spatial light modulator 116, the beam may pass through the 4f optical system 118 and then through the aperture 120 for spatial filtering and / or further beam shaping.

[0059] A longitudinally structured beam can be configured to have a narrower beam in multiple regions along the z-axis, corresponding to the beam passing through multiple turbulent regions. The degree of narrowing of the longitudinally structured beam can also be based on the corresponding turbulence intensity, such that the longitudinally structured beam narrows slightly in turbulent regions of moderate turbulence intensity and further narrows in turbulent regions of strong turbulence intensity. When turbulent regions are adjacent to each other, the longitudinally structured beam can also have different portions with decreasing widths adjacent to each other. Similarly, when the longitudinally structured beam passes through a single turbulent region with variable turbulence intensity, the longitudinally structured beam can have a variable width, where the beam width is based on the turbulence intensity at the corresponding position along the beam path.

[0060] Figure 2 This is a schematic diagram of an example longitudinally structured beam 202 passing through turbulent region 204. In Example 210, the longitudinally structured beam 202 is transmitted between optical terminals 112 on different flying vehicles 206. In Example 220, the longitudinally structured beam 202 is transmitted between optical terminals 112 on satellite 222 and optical terminals 112 on the ground (e.g., at a ground station). In both Examples 210 and 220, the longitudinally structured beam 202 is configured to have a narrowing region 208 at a location on the longitudinally structured beam 202, such that the beam width is smaller as it passes through turbulent region 204. The longitudinally structured beam 202 may have a narrower width only at a defined location in turbulent region 204, where the beam width changes around the periphery of turbulent region 204. In other embodiments, the longitudinally structured beam 202 may narrow a distance before passing through turbulent region 204 and continue to narrow until a certain distance after passing through turbulent region 204, such that some of the beam narrows outside turbulent region 204.

[0061] Figure 3This is a schematic diagram of a longitudinally structured beam 202 passing through multiple turbulent regions. The longitudinally structured beam 202 can encounter multiple turbulent regions with increased turbulence, and can therefore be configured to have narrow beams in multiple regions along the z-axis, corresponding to the beam's passage through said turbulent regions. The degree of narrowing of the longitudinally structured beam 202 can also be based on the corresponding turbulence intensity, such that the longitudinally structured beam 202 narrows slightly in turbulent regions of moderate turbulence intensity and further narrows in turbulent regions of strong turbulence intensity. Similar to... Figure 2 In Example 210, a longitudinally structured beam 202 is transmitted between optical terminals 112 on different flying vehicles 206. However, in this example, the longitudinally structured beam 202 traverses multiple turbulent regions, namely a first turbulent region 302 with a first turbulence intensity and a second turbulent region 304 with a second turbulence intensity, wherein the first turbulence intensity is greater than the second turbulence intensity. Therefore, the longitudinally structured beam 202 is configured to have a reduced width at the first turbulent region 302 and the second turbulent region 304. The width of the longitudinally structured beam 202 at the first turbulent region 302 is smaller than its width at the second turbulent region 304 to accommodate the different turbulence intensities. Although Figure 3 The example shown only illustrates two turbulent regions and two corresponding narrowing regions of the longitudinally structured beam 202, but it should be understood that additional turbulent regions can be identified in the path of the longitudinally structured beam 202, and the longitudinally structured beam 202 can be constructed to have a corresponding number of narrowing regions.

[0062] When turbulent regions are adjacent, the longitudinally structured beam 202 can also have distinct portions with decreasing widths adjacent to each other. For example, a first turbulent region 302 can be adjacent to a second turbulent region 304, such that the longitudinally structured beam 202 passes through the first turbulent region 302 and then immediately passes through the second turbulent region 304. In this case, the longitudinally structured beam 202 can be configured such that a first length of the longitudinally structured beam 202 narrows to a first width corresponding to its position where it passes through the first turbulent region 302, and an adjacent second length of the longitudinally structured beam 202 narrows to a second width corresponding to its position where it passes through the second turbulent region 304. Similarly, the longitudinally structured beam 202 can have a variable width when it passes through a single turbulent region with variable turbulence intensity, wherein the width is based on the turbulence intensity at the corresponding position along the beam path.

[0063] Figure 4 A graph showing different P-wave numbers in a Bessel-Gaussian spatial mode, along with the on-axis intensity and width of the beam obtained from the coherent superposition of the spatial modes, is presented. In the top graph, the P-wave number k... z This includes a series of uniformly spaced frequencies that form a comb in the space-frequency domain. The intermediate longitudinal wave number k... zIt has a high corresponding coefficient A n This results in a longitudinally structured beam with a region of higher on-axis intensity along the z-axis, as shown in the middle graph. The on-axis intensity of the beam is inversely proportional to the beam width, meaning that the beam will be narrower in the same region along the z-axis, where the beam has higher on-axis intensity.

[0064] Figure 5 This is an example of method 500 or a flowchart of generating a longitudinally structured beam to improve transmission in turbulence. As described herein, the steps of method 500 are performed by a computing device; however, it should be understood that method 500 can be implemented, for example, by at least one processor according to instructions stored in memory, which, when executed, cause the processor to perform the steps. In block 502, the computing device receives turbulence information indicating the location of a turbulent region. The turbulence information may also indicate the turbulence intensity at the turbulent region.

[0065] At box 504, the computing device determines multiple spatial modes of the beam based on the location of the turbulent region. These multiple spatial modes can include multiple Bessel-Gaussian spatial modes, each comprising a different P-wave number. The different P-wave numbers can have equal spatial frequency intervals. The computing device can also determine the complex coefficients of the spatial modes based on turbulence information.

[0066] In block 506, the computing device generates instructions for generating a longitudinally structured beam comprising multiple spatial patterns, wherein the longitudinally structured beam at a location within the turbulent region has a smaller beam width compared to its beam width outside the turbulent region. The beam width of the longitudinally structured beam may narrow as it reaches the turbulent region and widen as it passes through the turbulent region, such that the beam width within the turbulent region is narrower compared to its beam width outside and on both sides of the turbulent region. The width of the longitudinally structured beam at the turbulent region may be based on the turbulence intensity.

[0067] In optional box 508, the computing device sends the generated instructions to a spatial light modulator to generate a longitudinally structured beam, wherein the beam originates from a laser and is incident on the spatial light modulator. The longitudinally structured beam can be generated from an aircraft. The longitudinally structured beam can be configured for optical communication.

[0068] While at least one exemplary embodiment of the invention has been disclosed herein, it should be understood that modifications, alternatives, and alternatives may be apparent to those skilled in the art and may be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiments. Furthermore, in this disclosure, the terms “comprising” or “including” do not exclude other elements or steps, the absence of a modifier or “a” does not exclude a plurality, and the term “or” means one or both. Moreover, unless otherwise stated in this disclosure or the context, features or steps already described may be used in combination with other features or steps and may be used in any order.

Claims

1. A method for generating longitudinally structured beams to improve transmission in turbulent flow, the method comprising: The computing device receives turbulence information indicating the location of the turbulent region; The computing device determines multiple spatial patterns of the light beam based on the location of the turbulent region; as well as The computing device generates instructions for generating longitudinally structured beams comprising the plurality of spatial patterns, wherein the longitudinally structured beams at the location in the turbulent region have a smaller beam width compared to the beam width outside the location in the turbulent region.

2. The method according to claim 1, comprising: The computing device sends the generated instructions to the spatial light modulator to generate the longitudinally structured beam, wherein the beam is incident from the laser onto the spatial light modulator.

3. The method according to claim 1, wherein, The generated instructions are used to narrow the beam width of the longitudinally structured beam when it reaches the turbulent region and widen it when it passes through the turbulent region.

4. The method according to claim 1, comprising: The longitudinally structured beam is generated from the aircraft, wherein the longitudinally structured beam is configured for optical communication.

5. The method according to claim 1, wherein, The turbulence information indicates the turbulence intensity at the turbulence region, wherein the width of the longitudinally structured beam at the turbulence region is based on the turbulence intensity.

6. The method according to claim 1, wherein, The plurality of spatial modes include a plurality of Bessel-Gaussian spatial modes, each of which includes a different P-wave number.

7. The method according to claim 6, wherein, The different longitudinal wave numbers include equal spatial frequency intervals.

8. A system for generating longitudinally structured beams to improve transmission in turbulent flow, the system comprising: A computing device communicatively connected to a spatial light modulator, the computing device including a processor and a memory storing instructions, which, when executed by the processor, cause the processor to: Receive turbulence information indicating the location of turbulent regions; Multiple spatial modes of the beam are determined based on the location of the turbulent region; and Instructions are generated for generating longitudinally structured beams comprising the plurality of spatial patterns, wherein the longitudinally structured beams at the location in the turbulent region have a smaller beam width compared to the beam width outside the location in the turbulent region.

9. The system according to claim 8, wherein, The instruction causes the processor to send the generated instruction to the spatial light modulator to generate the longitudinally structured beam, wherein the beam is incident from the laser onto the spatial light modulator.

10. The system according to claim 8, wherein, The generated instructions are used to narrow the beam width of the longitudinally structured beam when it reaches the turbulent region and widen it when it passes through the turbulent region.

11. The system of claim 8, comprising an aircraft, from which the longitudinally structured beam is generated, wherein, The longitudinally structured beam is configured for optical communication.

12. The system according to claim 8, wherein, The turbulence information indicates the turbulence intensity at the turbulence region, wherein the width of the longitudinally structured beam at the turbulence region is based on the turbulence intensity.

13. The system according to claim 8, wherein, The plurality of spatial modes include a plurality of Bessel-Gaussian spatial modes, each of which includes a different P-wave number.

14. The system according to claim 13, wherein, The different longitudinal wave numbers include equal spatial frequency intervals.

15. A non-transitory computer-readable storage medium, the non-transitory computer-readable storage medium comprising instructions that, when executed by a processor of a device, cause the processor to: Receive turbulence information indicating the location of turbulent regions; Multiple spatial modes of the beam are determined based on the location of the turbulent region; and Instructions are generated for generating a longitudinally structured beam comprising the plurality of spatial patterns, wherein, The longitudinally structured beam at the location in the turbulent region has a smaller beam width compared to the beam width outside the location in the turbulent region.

16. The non-transitory computer-readable storage medium according to claim 15, wherein, The instructions cause the processor to send the generated instructions to the spatial light modulator to generate the longitudinally structured beam, wherein the beam is incident from the laser onto the spatial light modulator.

17. The non-transitory computer-readable storage medium according to claim 15, wherein, The generated instructions are used to narrow the beam width of the longitudinally structured beam when it reaches the turbulent region and widen it when it passes through the turbulent region.

18. The non-transitory computer-readable storage medium of claim 15, comprising an aircraft, from which the longitudinally structured beam is generated, wherein, The longitudinally structured beam is configured for optical communication.

19. The non-transitory computer-readable storage medium according to claim 15, wherein, The turbulence information indicates the turbulence intensity at the turbulence region, wherein the width of the longitudinally structured beam at the turbulence region is based on the turbulence intensity.

20. The non-transitory computer-readable storage medium according to claim 15, wherein, The plurality of spatial modes include a plurality of Bessel-Gaussian spatial modes, each of which includes a different P-wave number.

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