SYSTEM AND METHOD FOR EMITTING A LASER BEAM INTO SPACE
The remote laser source system with hollow-core fiber wavelength conversion simplifies and stabilizes laser beam emissions into space by reducing system complexity and ensuring eye safety through the use of high-energy, eye-safe wavelengths.
Patent Information
- Application Number
- FR2023014501
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2023-12-21
- Publication Date
- 2026-01-02
- Estimated Expiration
- 2043-12-21
AI Technical Summary
Existing laser beam emission systems for space applications are complex and heavy due to the integration of high-energy laser sources, posing challenges in alignment and eye safety, particularly when using wavelengths outside the eye-safe near-infrared spectrum.
A system utilizing a remote laser source independent of the mount, employing a hollow-core fiber for wavelength conversion and beam expansion, allowing high-energy laser beams to be generated with wavelengths within the eye-safe near-infrared spectrum, thus reducing system complexity and weight.
The system achieves reduced mechanical stress, simplified alignment, and enhanced eye safety by using a lightweight, high-energy laser source with wavelength conversion, enabling stable laser emissions into space.
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Abstract
Description
Title of the invention: SYSTEM AND METHOD FOR EMITTING A LASER BEAM INTO SPACE technical field
[0001] The present invention relates to a laser beam emission system for space, particularly but not exclusively for telescope observation of a body in space, including a telescope and a laser source. PRIOR TECHNOLOGY
[0002] Laser beam emissions are produced into space. These laser beam emissions are used, for example, in ranging systems, such as satellite laser ranging (SLR) systems. In such ranging applications, telescopes coupled to laser sources are used. The telescope and the laser source are fixed to a mount that has joints allowing alignment between the telescope and the laser emission.
[0003] A suitable arrangement is schematically illustrated in [Fig. 1A]. A telescope 100 is fixed to a mount 130. A laser source 120 and a beam magnifier 110 are also fixed to the mount 130. The beam magnifier 110 is arranged to enlarge the size of a laser beam emitted by the laser source 120, in order to reduce the divergence of the laser beam emitted by the laser source 120. A beam magnifier with a magnification ratio of G conventionally allows the initial divergence to be divided approximately by G.
[0004] The wavelength of the laser beam emitted by the laser source 120 is typically in the range of 1.4 pm to 2 pm, which corresponds to an eye-safe subset of the near-infrared (NIR) spectrum. Indeed, the cornea of the human eye strongly attenuates wavelengths beyond 1.4 pm. Using such laser beams, with wavelengths in the eye-safe subset of the near-infrared spectrum, therefore limits the risk of retinal damage.
[0005] One problem posed by such laser sources is their size and weight. To ensure fine alignment between the telescope and the laser emission, the mount 130 is therefore a complex mechanical structure capable of supporting the weight and size of such laser sources.
[0006] It is also possible to produce laser beam emissions into space without coupling the laser source to a telescope on the mount. This arrangement is schematically illustrated in [Fig. 1B]. The mount 131 used, however, remains high complexity, due to the size and weight of the laser source, despite the absence of the telescope on this mount 131.
[0007] Furthermore, high-energy laser sources (i.e., suitable for emission into space, typically with an energy greater than 10 mJ) and high pulse frequency, which emit laser beams with wavelengths in the range of 1.4 to 2 pm, are themselves highly complex devices. Less complex laser sources exist, but these laser sources, on the one hand, have an even greater size and weight, and on the other hand, emit laser beams at wavelengths that are below the eye-safe subset of the near-infrared spectrum, which presents a higher risk of retinal damage to the human eye.
[0008] It is therefore desirable to overcome these drawbacks of the prior art. In particular, it is desirable to provide a solution that reduces the complexity of systems using laser emissions into space, especially of the mount used, while ensuring eye safety. Description of the invention
[0009] To this end, a system for producing a laser emission into space is proposed herein. The system includes a laser source, a beam expander from which the laser emission into space originates, and a mount on which the beam expander is fixed. The mount is arranged to allow adjustment of the direction of the laser emission from the beam expander. The laser source is arranged to generate a first laser beam with a wavelength shorter than an eye-safe subset of the near-infrared spectrum. The system further includes a wavelength matching device based on a hollow-core fiber, and a remote device using a hollow-body optical fiber to connect the remote device to the beam expander so that the laser source is independent of the mount.The wavelength adaptation device is designed to convert the first laser beam into a second laser beam, injected at the input of the refracting device, whose wavelength falls within the eye-safe subset of the near-infrared spectrum. Thus, the system uses a low-complexity laser source without the mount bearing the weight and bulk of the laser source, thereby minimizing the risk of eye damage. The overall system complexity is therefore reduced.
[0010] According to a particular embodiment, the laser source is based on neodymium-doped yttrium-aluminum garnet amplifying media. Thus, a low-complexity, high-energy laser source can be readily found off the shelf.
[0011] According to a particular embodiment, the laser source, the wavelength matching device, and the offset device are located in a controlled environment room, and the beam magnifier and the mount are located outside the controlled environment room. Thus, laser emission into space is easily achieved, with high laser beam stability.
[0012] According to a particular embodiment, the order of magnitude of the wavelength of the first laser beam is 1 pm and the order of magnitude of the wavelength of the second laser beam is greater than 1.4 pm.
[0013] According to a particular embodiment, the system further comprises a telescope, the telescope also being fixed on the mount, the mount being arranged to allow alignment between the telescope (200) and the laser emission into space.
[0014] Also proposed here is a method of emitting a laser beam into space by the system presented above in any of its embodiments, the method including: generating the first laser beam; modifying the wavelength of the first laser beam in order to obtain the second laser beam; conveying the second laser beam by optical fiber; emitting the second laser beam into space by performing beam magnification.
[0015] In a particular embodiment, when the system includes a telescope as mentioned above, the method further includes capturing, via the telescope, light information induced by the second laser beam emitted. Brief description of the drawings
[0016] The features of the invention mentioned above, as well as others, will become clearer upon reading the following description of at least one exemplary embodiment, said description being made in relation to the accompanying drawings, among which:
[0017] [Fig. 1 A] schematically illustrates an arrangement producing a laser emission towards space, according to a first mode of realization of the state of the art;
[0018] [Fig. IB] schematically illustrates an arrangement producing a laser emission towards space, according to a second embodiment of the prior art;
[0019] [Fig.2A] schematically illustrates a system arrangement for emitting a laser into space using a remote laser source, according to a first particular embodiment;
[0020] [Fig. 2B] schematically illustrates a system arrangement for emitting a laser into space using a remote laser source, according to a second particular embodiment; and
[0021] [Fig.3] schematically illustrates a flowchart of a process implemented by the system of [Fig.2A] or [Fig.2B].
[0022] DETAILED DESCRIPTION OF IMPROVEMENTS
[0023] In relation to [Fig.2A] a system is schematically presented including a mount 230 on which a beam enlarger 210 is fixed. The mount 230 is arranged to allow adjustment of the direction of a laser emission from the beam enlarger 210. To do this, the mount 230 has various joints providing the degrees of freedom necessary for adjusting the direction of this laser emission.
[0024] The system therefore also includes a laser source 220. Unlike the systems in Figs. IA and IB, the laser source 220 of the system in [Fig. 2A] is independent of the mount 230. The laser source 220 is thus not fixed to the mount 230 supporting the beam enlarger 210. The complexity of the mount 230 is thereby reduced.
[0025] The laser source 220 is thus offset from the mount 230 by means of an offset device 222 which uses a hollow-core fiber 223 filled with a gas and which includes a device for injecting a laser beam into the optical fiber 223. The use of a hollow-core fiber makes it possible to support high-energy laser beams, which is not possible with a solid-core fiber.
[0026] The optical fiber 223 is connected to the input of the beam enlarger 210 so that, by enlarging the beam size, the divergence of the laser beam supplied at the output of the optical fiber 223 is reduced.
[0027] The offset device 222 is arranged to emit a laser beam into the optical fiber 223 which is injected into the input of said offset device 222.
[0028] The laser source 220 is arranged to generate a high-energy laser beam with a wavelength shorter than the eye-safe subset of the near-infrared spectrum. In a particular embodiment, the laser source 220 is configured to generate a laser beam with a wavelength on the order of 1 pm. For example, the laser source generates a laser beam of 1.054 pm or 1.064 pm.
[0029] The laser source 220 is then heavier and bulkier than if the laser source were configured to generate a laser beam with a wavelength within the eye-safe subset of the near-infrared spectrum. However, since the laser source 220 is independent of the mount 230, it is not necessary to modify the mount 230 to support the weight and bulk of the laser source 220. This also allows the laser source 220 to be placed in a stabilized environment, for example, horizontally, thus preventing the laser source 220 from being subjected to vibrations or mechanical stresses.
[0030] For example, the laser source 220 is a high-energy laser source based on neodymium-doped yttrium-aluminum garnet (Nd YAG) amplifying media.
[0031] Between the laser source 220 and the remote device 222, the observation system includes a wavelength matching device 221 based on a hollow-core fiber. The hollow-core fiber is filled with a gas. In a particular embodiment, the hollow-core fiber is stretched, typically over several meters, in order to induce wavelength conversion by Raman effect of the light injected into it.
[0032] The gas filling the hollow body fibers used by the system is adapted to the wavelengths of the laser beams used.
[0033] The wavelength matching device 221 is thus arranged to convert the laser beam supplied by the laser source 220 into a laser beam, injected at the input of the offset device 222, whose wavelength is included in the eye-safe subset of the near-infrared spectrum. For example, the order of magnitude of the wavelength of the laser beam at the output of the wavelength matching device 221 is greater than 1.4 pm. Because the laser beam at the output of the laser source 200 is high-energy, the laser beam at the output of the wavelength matching device 221 is also high-energy.
[0034] Thus, thanks to this arrangement, the mount 230 does not have to support the laser source 220 and therefore does not need to be able to bear its weight and size. A reduction in complexity is then achieved by using a laser source producing a high-energy laser beam with a wavelength shorter than the eye-safe subset of the near-infrared spectrum, thereby reducing the mechanical stresses on the mount 230 and eliminating the risk of retinal damage to the human eye. Furthermore, such a system can easily withstand high pulse frequencies.
[0035] In a particular embodiment, the laser source 220, the wavelength matching device 221, and the offset device 222 are located in a room with a controlled environment, particularly with regard to temperature and humidity, and the beam magnifier 210 and the mount 230 are located outside the room with a controlled environment. The laser beam generated by the laser source 220 and the wavelength conversion performed by the wavelength matching device 221 are thus more stable.
[0036] In relation to [Fig.2B] is schematically presented a system including a telescope 200 fixed to a mount 231. The system of [Fig.2B] is adapted to carry out telemetry operations.
[0037] The beam enlarger 210 is also fixed to the mount 231. The mount 231 is arranged to allow alignment between the telescope 200 and a laser emission from the beam enlarger 210. To do this, the mount 231 has various joints offering the degrees of freedom necessary to achieve this alignment between the telescope and the laser emission.
[0038] In a particular embodiment, the alignment of the telescope 200 and the laser emission from the beam expander 210 is controlled by a computer system. The computer system includes electronic circuitry configured to implement software functions. The telescope 200 is, for example, equipped with a dichroic mirror that splits an incident light beam into a first sub-flow in the visible spectrum and a second sub-flow in the near-infrared spectrum. A first camera is arranged to capture images of the first sub-flow in order to allow a first software function to track a body in space (satellite, debris, etc.).A second camera is arranged to capture images of the second sub-stream in order to allow a second software function to perform edge detection to detect backscattered laser pulses, to ensure the alignment of the telescope and the laser emission from the beam magnifier 210. A single photon avalanche diode SPAD (Single Photon Avalanche Detector) and a time digital converter TDC (Time Digital Converter) allow ranging operations to be performed from the backscattered laser pulses of the second sub-stream.
[0039] Thus, the mount 231 is more complex than the mount 230 shown in relation to [Fig. 2A]. However, the mount 231 is less complex than the mount 131 of [Fig. 1B], thanks to the offset of the laser source 220 using the hollow-body optical fiber 223 and the offset device 222. It should be noted here that, when a telescope is used, reducing the complexity of the mount supporting the telescope is an even more important issue.
[0040] Fig. 3 schematically illustrates a flowchart of a process implemented by the system of Fig. 2A or Fig. 2B.
[0041] In step 301, the system generates a first laser beam with a wavelength shorter than the eye-safe subset of the near-infrared spectrum (e.g., on the order of 1 pm). The first laser beam is high-energy (typically greater than 10 rnJ). In Figs. 2A and 2B, the first laser beam is generated by the laser source 220.
[0042] In step 302, the system modifies the wavelength of the first laser beam to obtain a second laser beam whose wavelength is included in the eye-safe subset of the near-infrared spectrum (e.g., on the order of 1.5 pm). A gas-filled hollow-core fiber is used for this purpose. In Figs. 2A and 2B, the second laser beam is generated by the wavelength-matching device 221.
[0043] In step 303, the system carries the second laser beam via a hollow-body optical fiber. This enables it to support the high energy of the laser beam. See Figs. 2A and 2B, the second laser beam is conveyed by the offset device 222 and the optical fiber 223 to the beam enlarger 210.
[0044] In a step 304, the system emits the second laser beam into space by performing beam magnification. In Figs. 2A and 2B, the beam magnification and emission into space are carried out by the beam magnifier 210. The second laser beam has characteristics, particularly energy characteristics, that allow it to reach space.
[0045] In the particular embodiment of [Fig. 2B] where the telescope is coupled to the laser source, in step 305, the system captures, via the telescope 200, light information induced by the second emitted laser beam. Tracking of a body in space by the system, and telemetry operations, can then be carried out, as already described above.
Claims
Demands
1. A system for producing a laser emission into space, the system including a laser source (220), a beam expander (210) from which the laser emission into space originates, and a mount (230, 231) on which the beam expander (210) is fixed, the mount (230, 231) being arranged to allow adjustment of the direction of the laser emission, characterized in that the laser source (200) is arranged to generate a first laser beam with a wavelength less than an eye-safe subset of the near-infrared spectrum, the system further including a wavelength matching device (221) based on a hollow-core fiber, and a relocation device (222) using a hollow-core optical fiber (223) to connect the relocation device (222) to the beam expander (210) such that the laser source (220) is independent of the mount (230, 231),and the wavelength adaptation device (221) being arranged to convert the first laser beam into a second laser beam, injected at the inlet of the offset device (222), whose wavelength is included in the eye-safe subset of the near-infrared spectrum.
2. The system according to claim 1, wherein the laser source (220) is based on neodymium-doped yttrium-aluminum garnet amplifying media.
3. The system according to claim 1 or 2, wherein the laser source (220), the wavelength matching device (221) and the offset device (222) are placed in a controlled environment room, and the beam enlarger (210) and the mount (230, 231) are placed outside the controlled environment room.
4. The system according to any one of claims 1 to 3, wherein the order of magnitude of the wavelength of the first laser beam is 1 pm and the order of magnitude of the wavelength of the second laser beam is greater than 1.4 pm.
5. The system according to any one of claims 1 to 4, further comprising a telescope (200), the telescope (200) also being fixed to the mount (231), the mount (230, 231) being arranged to to allow alignment between the telescope (200) and the laser emission towards space.
6. A method of emitting a laser beam into space by the system according to any one of claims 1 to 4, the method including: - generating (301) the first laser beam; - modifying (302) the wavelength of the first laser beam in order to obtain the second laser beam; - conveying (303) the second laser beam by optical fiber; and - emitting (304) the second laser beam into space by performing beam magnification.
7. The method according to claim 6, wherein the system is according to claim 5, and wherein the method further comprises: - capturing (305), via the telescope, light information induced by the second laser beam emitted.